server(filesystem): rebuild everything imaginable

This wonderfully large commit replaces basically everything under the
`server/filesystem` package, re-implementing essentially everything.

This is related to
https://github.com/pterodactyl/wings/security/advisories/GHSA-494h-9924-xww9

If any vulnerabilities related to symlinks persist after this commit, I
will be very upset.

Signed-off-by: Matthew Penner <me@matthewp.io>

config/config.go

@@ -12,6 +12,7 @@ import (
 	"regexp"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"text/template"
 	"time"
 
@@ -20,6 +21,7 @@ import (
 	"github.com/apex/log"
 	"github.com/creasty/defaults"
 	"github.com/gbrlsnchs/jwt/v3"
+	"golang.org/x/sys/unix"
 	"gopkg.in/yaml.v2"
 
 	"github.com/pterodactyl/wings/system"
@@ -209,6 +211,8 @@ type SystemConfiguration struct {
 	Backups Backups `yaml:"backups"`
 
 	Transfers Transfers `yaml:"transfers"`
+
+	OpenatMode string `default:"auto" yaml:"openat_mode"`
 }
 
 type CrashDetection struct {
@@ -671,3 +675,34 @@ func getSystemName() (string, error) {
 	}
 	return release["ID"], nil
 }
+
+var openat2 atomic.Bool
+var openat2Set atomic.Bool
+
+func UseOpenat2() bool {
+	if openat2Set.Load() {
+		return openat2.Load()
+	}
+	defer openat2Set.Store(true)
+
+	c := Get()
+	openatMode := c.System.OpenatMode
+	switch openatMode {
+	case "openat2":
+		openat2.Store(true)
+		return true
+	case "openat":
+		openat2.Store(false)
+		return false
+	default:
+		fd, err := unix.Openat2(unix.AT_FDCWD, "/", &unix.OpenHow{})
+		if err != nil {
+			log.WithError(err).Warn("error occurred while checking for openat2 support, falling back to openat")
+			openat2.Store(false)
+			return false
+		}
+		_ = unix.Close(fd)
+		openat2.Store(true)
+		return true
+	}
+}

go.mod

@@ -30,7 +30,7 @@ require (
 	github.com/iancoleman/strcase v0.3.0
 	github.com/icza/dyno v0.0.0-20230330125955-09f820a8d9c0
 	github.com/juju/ratelimit v1.0.2
-	github.com/karrick/godirwalk v1.17.0
+	github.com/klauspost/compress v1.17.7
 	github.com/klauspost/pgzip v1.2.6
 	github.com/magiconair/properties v1.8.7
 	github.com/mattn/go-colorable v0.1.13
@@ -43,6 +43,7 @@ require (
 	github.com/stretchr/testify v1.9.0
 	golang.org/x/crypto v0.21.0
 	golang.org/x/sync v0.6.0
+	golang.org/x/sys v0.18.0
 	gopkg.in/ini.v1 v1.67.0
 	gopkg.in/yaml.v2 v2.4.0
 	gopkg.in/yaml.v3 v3.0.1
@@ -83,7 +84,6 @@ require (
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
-	github.com/klauspost/compress v1.17.7 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
@@ -122,7 +122,6 @@ require (
 	golang.org/x/arch v0.7.0 // indirect
 	golang.org/x/mod v0.16.0 // indirect
 	golang.org/x/net v0.22.0 // indirect
-	golang.org/x/sys v0.18.0 // indirect
 	golang.org/x/term v0.18.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	golang.org/x/time v0.0.0-20220922220347-f3bd1da661af // indirect

go.sum

@@ -219,8 +219,6 @@ github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1
 github.com/jstemmer/go-junit-report v0.9.1/go.mod h1:Brl9GWCQeLvo8nXZwPNNblvFj/XSXhF0NWZEnDohbsk=
 github.com/juju/ratelimit v1.0.2 h1:sRxmtRiajbvrcLQT7S+JbqU0ntsb9W2yhSdNN8tWfaI=
 github.com/juju/ratelimit v1.0.2/go.mod h1:qapgC/Gy+xNh9UxzV13HGGl/6UXNN+ct+vwSgWNm/qk=
-github.com/karrick/godirwalk v1.17.0 h1:b4kY7nqDdioR/6qnbHQyDvmA17u5G1cZ6J+CZXwSWoI=
-github.com/karrick/godirwalk v1.17.0/go.mod h1:j4mkqPuvaLI8mp1DroR3P6ad7cyYd4c1qeJ3RV7ULlk=
 github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNUXsshfwJMBgNA0RU6/i7WVaAegv3PtuIHPMs=
 github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=

internal/ufs/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Matthew Penner
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

internal/ufs/README.md

@@ -0,0 +1,17 @@
+# Filesystem
+
+## Licensing
+
+Most code in this package is licensed under `MIT` with some exceptions.
+
+The following files are licensed under `BSD-3-Clause` due to them being copied
+verbatim or derived from [Go](https://go.dev)'s source code.
+
+- [`file_posix.go`](./file_posix.go)
+- [`mkdir_unix.go`](./mkdir_unix.go)
+- [`path_unix.go`](./path_unix.go)
+- [`removeall_unix.go`](./removeall_unix.go)
+- [`stat_unix.go`](./stat_unix.go) 
+- [`walk.go`](./walk.go)
+
+These changes are not associated with nor endorsed by The Go Authors.

internal/ufs/doc.go

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+// Package ufs provides an abstraction layer for performing I/O on filesystems.
+// This package is designed to be used in-place of standard `os` package I/O
+// calls, and is not designed to be used as a generic filesystem abstraction
+// like the `io/fs` package.
+//
+// The primary use-case of this package was to provide a "chroot-like" `os`
+// wrapper, so we can safely sandbox I/O operations within a directory and
+// use untrusted arbitrary paths.
+package ufs

internal/ufs/error.go

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+package ufs
+
+import (
+	"errors"
+	iofs "io/fs"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+var (
+	// ErrIsDirectory is an error for when an operation that operates only on
+	// files is given a path to a directory.
+	ErrIsDirectory = errors.New("is a directory")
+	// ErrNotDirectory is an error for when an operation that operates only on
+	// directories is given a path to a file.
+	ErrNotDirectory = errors.New("not a directory")
+	// ErrBadPathResolution is an error for when a sand-boxed filesystem
+	// resolves a given path to a forbidden location.
+	ErrBadPathResolution = errors.New("bad path resolution")
+	// ErrNotRegular is an error for when an operation that operates only on
+	// regular files is passed something other than a regular file.
+	ErrNotRegular = errors.New("not a regular file")
+
+	// ErrClosed is an error for when an entry was accessed after being closed.
+	ErrClosed = iofs.ErrClosed
+	// ErrInvalid is an error for when an invalid argument was used.
+	ErrInvalid = iofs.ErrInvalid
+	// ErrExist is an error for when an entry already exists.
+	ErrExist = iofs.ErrExist
+	// ErrNotExist is an error for when an entry does not exist.
+	ErrNotExist = iofs.ErrNotExist
+	// ErrPermission is an error for when the required permissions to perform an
+	// operation are missing.
+	ErrPermission = iofs.ErrPermission
+)
+
+// LinkError records an error during a link or symlink or rename
+// system call and the paths that caused it.
+type LinkError = os.LinkError
+
+// PathError records an error and the operation and file path that caused it.
+type PathError = iofs.PathError
+
+// SyscallError records an error from a specific system call.
+type SyscallError = os.SyscallError
+
+// NewSyscallError returns, as an error, a new SyscallError
+// with the given system call name and error details.
+// As a convenience, if err is nil, NewSyscallError returns nil.
+func NewSyscallError(syscall string, err error) error {
+	return os.NewSyscallError(syscall, err)
+}
+
+// convertErrorType converts errors into our custom errors to ensure consistent
+// error values.
+func convertErrorType(err error) error {
+	if err == nil {
+		return nil
+	}
+	var pErr *PathError
+	switch {
+	case errors.As(err, &pErr):
+		switch {
+		// File exists
+		case errors.Is(pErr.Err, unix.EEXIST):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrExist,
+			}
+		// Is a directory
+		case errors.Is(pErr.Err, unix.EISDIR):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrIsDirectory,
+			}
+		// Not a directory
+		case errors.Is(pErr.Err, unix.ENOTDIR):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrNotDirectory,
+			}
+		// No such file or directory
+		case errors.Is(pErr.Err, unix.ENOENT):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrNotExist,
+			}
+		// Operation not permitted
+		case errors.Is(pErr.Err, unix.EPERM):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrPermission,
+			}
+		// Invalid cross-device link
+		case errors.Is(pErr.Err, unix.EXDEV):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrBadPathResolution,
+			}
+		// Too many levels of symbolic links
+		case errors.Is(pErr.Err, unix.ELOOP):
+			return &PathError{
+				Op:   pErr.Op,
+				Path: pErr.Path,
+				Err:  ErrBadPathResolution,
+			}
+		}
+	}
+	return err
+}

internal/ufs/file.go

@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+package ufs
+
+import (
+	"io"
+	iofs "io/fs"
+
+	"golang.org/x/sys/unix"
+)
+
+// DirEntry is an entry read from a directory.
+type DirEntry = iofs.DirEntry
+
+// File describes readable and/or writable file from a Filesystem.
+type File interface {
+	// Name returns the base name of the file.
+	Name() string
+
+	// Stat returns the FileInfo structure describing the file.
+	// If there is an error, it will be of type *PathError.
+	Stat() (FileInfo, error)
+
+	// ReadDir reads the contents of the directory associated with the file f
+	// and returns a slice of DirEntry values in directory order.
+	// Subsequent calls on the same file will yield later DirEntry records in the directory.
+	//
+	// If n > 0, ReadDir returns at most n DirEntry records.
+	// In this case, if ReadDir returns an empty slice, it will return an error explaining why.
+	// At the end of a directory, the error is io.EOF.
+	//
+	// If n <= 0, ReadDir returns all the DirEntry records remaining in the directory.
+	// When it succeeds, it returns a nil error (not io.EOF).
+	ReadDir(n int) ([]DirEntry, error)
+
+	// Readdirnames reads the contents of the directory associated with file
+	// and returns a slice of up to n names of files in the directory,
+	// in directory order. Subsequent calls on the same file will yield
+	// further names.
+	//
+	// If n > 0, Readdirnames returns at most n names. In this case, if
+	// Readdirnames returns an empty slice, it will return a non-nil error
+	// explaining why. At the end of a directory, the error is io.EOF.
+	//
+	// If n <= 0, Readdirnames returns all the names from the directory in
+	// a single slice. In this case, if Readdirnames succeeds (reads all
+	// the way to the end of the directory), it returns the slice and a
+	// nil error. If it encounters an error before the end of the
+	// directory, Readdirnames returns the names read until that point and
+	// a non-nil error.
+	Readdirnames(n int) (names []string, err error)
+
+	// Fd returns the integer Unix file descriptor referencing the open file.
+	// If f is closed, the file descriptor becomes invalid.
+	// If f is garbage collected, a finalizer may close the file descriptor,
+	// making it invalid; see runtime.SetFinalizer for more information on when
+	// a finalizer might be run. On Unix systems this will cause the SetDeadline
+	// methods to stop working.
+	// Because file descriptors can be reused, the returned file descriptor may
+	// only be closed through the Close method of f, or by its finalizer during
+	// garbage collection. Otherwise, during garbage collection the finalizer
+	// may close an unrelated file descriptor with the same (reused) number.
+	//
+	// As an alternative, see the f.SyscallConn method.
+	Fd() uintptr
+
+	// Truncate changes the size of the file.
+	// It does not change the I/O offset.
+	// If there is an error, it will be of type *PathError.
+	Truncate(size int64) error
+
+	io.Closer
+
+	io.Reader
+	io.ReaderAt
+	io.ReaderFrom
+
+	io.Writer
+	io.WriterAt
+
+	io.Seeker
+}
+
+// FileInfo describes a file and is returned by Stat and Lstat.
+type FileInfo = iofs.FileInfo
+
+// FileMode represents a file's mode and permission bits.
+// The bits have the same definition on all systems, so that
+// information about files can be moved from one system
+// to another portably. Not all bits apply to all systems.
+// The only required bit is ModeDir for directories.
+type FileMode = iofs.FileMode
+
+// The defined file mode bits are the most significant bits of the FileMode.
+// The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
+// The values of these bits should be considered part of the public API and
+// may be used in wire protocols or disk representations: they must not be
+// changed, although new bits might be added.
+const (
+	// ModeDir represents a directory.
+	// d: is a directory
+	ModeDir = iofs.ModeDir
+	// ModeAppend represents an append-only file.
+	// a: append-only
+	ModeAppend = iofs.ModeAppend
+	// ModeExclusive represents an exclusive file.
+	// l: exclusive use
+	ModeExclusive = iofs.ModeExclusive
+	// ModeTemporary .
+	// T: temporary file; Plan 9 only.
+	ModeTemporary = iofs.ModeTemporary
+	// ModeSymlink .
+	// L: symbolic link.
+	ModeSymlink = iofs.ModeSymlink
+	// ModeDevice .
+	// D: device file.
+	ModeDevice = iofs.ModeDevice
+	// ModeNamedPipe .
+	// p: named pipe (FIFO)
+	ModeNamedPipe = iofs.ModeNamedPipe
+	// ModeSocket .
+	// S: Unix domain socket.
+	ModeSocket = iofs.ModeSocket
+	// ModeSetuid .
+	// u: setuid
+	ModeSetuid = iofs.ModeSetuid
+	// ModeSetgid .
+	// g: setgid
+	ModeSetgid = iofs.ModeSetgid
+	// ModeCharDevice .
+	// c: Unix character device, when ModeDevice is set
+	ModeCharDevice = iofs.ModeCharDevice
+	// ModeSticky .
+	// t: sticky
+	ModeSticky = iofs.ModeSticky
+	// ModeIrregular .
+	// ?: non-regular file; nothing else is known about this file.
+	ModeIrregular = iofs.ModeIrregular
+
+	// ModeType .
+	ModeType = iofs.ModeType
+
+	// ModePerm .
+	// Unix permission bits, 0o777.
+	ModePerm = iofs.ModePerm
+)
+
+const (
+	// O_RDONLY opens the file read-only.
+	O_RDONLY = unix.O_RDONLY
+	// O_WRONLY opens the file write-only.
+	O_WRONLY = unix.O_WRONLY
+	// O_RDWR opens the file read-write.
+	O_RDWR = unix.O_RDWR
+	// O_APPEND appends data to the file when writing.
+	O_APPEND = unix.O_APPEND
+	// O_CREATE creates a new file if it doesn't exist.
+	O_CREATE = unix.O_CREAT
+	// O_EXCL is used with O_CREATE, file must not exist.
+	O_EXCL = unix.O_EXCL
+	// O_SYNC open for synchronous I/O.
+	O_SYNC = unix.O_SYNC
+	// O_TRUNC truncates regular writable file when opened.
+	O_TRUNC = unix.O_TRUNC
+	// O_DIRECTORY opens a directory only. If the entry is not a directory an
+	// error will be returned.
+	O_DIRECTORY = unix.O_DIRECTORY
+	// O_NOFOLLOW opens the exact path given without following symlinks.
+	O_NOFOLLOW  = unix.O_NOFOLLOW
+	O_CLOEXEC   = unix.O_CLOEXEC
+	O_LARGEFILE = unix.O_LARGEFILE
+)
+
+const (
+	AT_SYMLINK_NOFOLLOW = unix.AT_SYMLINK_NOFOLLOW
+	AT_REMOVEDIR        = unix.AT_REMOVEDIR
+	AT_EMPTY_PATH       = unix.AT_EMPTY_PATH
+)

internal/ufs/file_posix.go

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was copied from `go/src/os/file_posix.go`.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+//go:build unix || (js && wasm) || wasip1 || windows
+
+package ufs
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// ignoringEINTR makes a function call and repeats it if it returns an
+// EINTR error. This appears to be required even though we install all
+// signal handlers with SA_RESTART: see https://go.dev/issue/22838,
+// https://go.dev/issue/38033, https://go.dev/issue/38836,
+// https://go.dev/issue/40846. Also, https://go.dev/issue/20400 and
+// https://go.dev/issue/36644 are issues in which a signal handler is
+// installed without setting SA_RESTART. None of these are the common case,
+// but there are enough of them that it seems that we can't avoid
+// an EINTR loop.
+func ignoringEINTR(fn func() error) error {
+	for {
+		err := fn()
+		if err != unix.EINTR {
+			return err
+		}
+	}
+}
+
+// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
+func syscallMode(i FileMode) (o FileMode) {
+	o |= i.Perm()
+	if i&ModeSetuid != 0 {
+		o |= unix.S_ISUID
+	}
+	if i&ModeSetgid != 0 {
+		o |= unix.S_ISGID
+	}
+	if i&ModeSticky != 0 {
+		o |= unix.S_ISVTX
+	}
+	// No mapping for Go's ModeTemporary (plan9 only).
+	return
+}

internal/ufs/filesystem.go

@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+package ufs
+
+import (
+	"time"
+)
+
+// Filesystem represents a filesystem capable of performing I/O operations.
+type Filesystem interface {
+	// Chmod changes the mode of the named file to mode.
+	//
+	// If the file is a symbolic link, it changes the mode of the link's target.
+	// If there is an error, it will be of type *PathError.
+	//
+	// A different subset of the mode bits are used, depending on the
+	// operating system.
+	//
+	// On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
+	// ModeSticky are used.
+	//
+	// On Windows, only the 0200 bit (owner writable) of mode is used; it
+	// controls whether the file's read-only attribute is set or cleared.
+	// The other bits are currently unused. For compatibility with Go 1.12
+	// and earlier, use a non-zero mode. Use mode 0400 for a read-only
+	// file and 0600 for a readable+writable file.
+	//
+	// On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
+	// and ModeTemporary are used.
+	Chmod(name string, mode FileMode) error
+
+	// Chown changes the numeric uid and gid of the named file.
+	//
+	// If the file is a symbolic link, it changes the uid and gid of the link's target.
+	// A uid or gid of -1 means to not change that value.
+	// If there is an error, it will be of type *PathError.
+	//
+	// On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
+	// EPLAN9 error, wrapped in *PathError.
+	Chown(name string, uid, gid int) error
+
+	// Lchown changes the numeric uid and gid of the named file.
+	//
+	// If the file is a symbolic link, it changes the uid and gid of the link itself.
+	// If there is an error, it will be of type *PathError.
+	//
+	// On Windows, it always returns the syscall.EWINDOWS error, wrapped
+	// in *PathError.
+	Lchown(name string, uid, gid int) error
+
+	// Chtimes changes the access and modification times of the named
+	// file, similar to the Unix utime() or utimes() functions.
+	//
+	// The underlying filesystem may truncate or round the values to a
+	// less precise time unit.
+	//
+	// If there is an error, it will be of type *PathError.
+	Chtimes(name string, atime, mtime time.Time) error
+
+	// Create creates or truncates the named file. If the file already exists,
+	// it is truncated.
+	//
+	// If the file does not exist, it is created with mode 0666
+	// (before umask). If successful, methods on the returned File can
+	// be used for I/O; the associated file descriptor has mode O_RDWR.
+	// If there is an error, it will be of type *PathError.
+	Create(name string) (File, error)
+
+	// Mkdir creates a new directory with the specified name and permission
+	// bits (before umask).
+	//
+	// If there is an error, it will be of type *PathError.
+	Mkdir(name string, perm FileMode) error
+
+	// MkdirAll creates a directory named path, along with any necessary
+	// parents, and returns nil, or else returns an error.
+	//
+	// The permission bits perm (before umask) are used for all
+	// directories that MkdirAll creates.
+	// If path is already a directory, MkdirAll does nothing
+	// and returns nil.
+	MkdirAll(path string, perm FileMode) error
+
+	// Open opens the named file for reading.
+	//
+	// If successful, methods on the returned file can be used for reading; the
+	// associated file descriptor has mode O_RDONLY.
+	//
+	// If there is an error, it will be of type *PathError.
+	Open(name string) (File, error)
+
+	// OpenFile is the generalized open call; most users will use Open
+	// or Create instead. It opens the named file with specified flag
+	// (O_RDONLY etc.).
+	//
+	// If the file does not exist, and the O_CREATE flag
+	// is passed, it is created with mode perm (before umask). If successful,
+	// methods on the returned File can be used for I/O.
+	//
+	// If there is an error, it will be of type *PathError.
+	OpenFile(name string, flag int, perm FileMode) (File, error)
+
+	// ReadDir reads the named directory,
+	//
+	// returning all its directory entries sorted by filename.
+	// If an error occurs reading the directory, ReadDir returns the entries it
+	// was able to read before the error, along with the error.
+	ReadDir(name string) ([]DirEntry, error)
+
+	// Remove removes the named file or (empty) directory.
+	//
+	// If there is an error, it will be of type *PathError.
+	Remove(name string) error
+
+	// RemoveAll removes path and any children it contains.
+	//
+	// It removes everything it can but returns the first error
+	// it encounters. If the path does not exist, RemoveAll
+	// returns nil (no error).
+	//
+	// If there is an error, it will be of type *PathError.
+	RemoveAll(path string) error
+
+	// Rename renames (moves) oldpath to newpath.
+	//
+	// If newpath already exists and is not a directory, Rename replaces it.
+	// OS-specific restrictions may apply when oldpath and newpath are in different directories.
+	// Even within the same directory, on non-Unix platforms Rename is not an atomic operation.
+	//
+	// If there is an error, it will be of type *LinkError.
+	Rename(oldname, newname string) error
+
+	// Stat returns a FileInfo describing the named file.
+	//
+	// If there is an error, it will be of type *PathError.
+	Stat(name string) (FileInfo, error)
+
+	// Lstat returns a FileInfo describing the named file.
+	//
+	// If the file is a symbolic link, the returned FileInfo
+	// describes the symbolic link. Lstat makes no attempt to follow the link.
+	//
+	// If there is an error, it will be of type *PathError.
+	Lstat(name string) (FileInfo, error)
+
+	// Symlink creates newname as a symbolic link to oldname.
+	//
+	// On Windows, a symlink to a non-existent oldname creates a file symlink;
+	// if oldname is later created as a directory the symlink will not work.
+	//
+	// If there is an error, it will be of type *LinkError.
+	Symlink(oldname, newname string) error
+
+	// WalkDir walks the file tree rooted at root, calling fn for each file or
+	// directory in the tree, including root.
+	//
+	// All errors that arise visiting files and directories are filtered by fn:
+	// see the [WalkDirFunc] documentation for details.
+	//
+	// The files are walked in lexical order, which makes the output deterministic
+	// but requires WalkDir to read an entire directory into memory before proceeding
+	// to walk that directory.
+	//
+	// WalkDir does not follow symbolic links found in directories,
+	// but if root itself is a symbolic link, its target will be walked.
+	WalkDir(root string, fn WalkDirFunc) error
+}

internal/ufs/fs_quota.go

@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+package ufs
+
+import (
+	"sync/atomic"
+)
+
+type Quota struct {
+	// fs is the underlying filesystem that runs the actual I/O operations.
+	*UnixFS
+
+	// limit is the size limit of the filesystem.
+	//
+	// limit is atomic to allow the limit to be safely changed after the
+	// filesystem was created.
+	//
+	// A limit of `-1` disables any write operation from being performed.
+	// A limit of `0` disables any limit checking.
+	limit atomic.Int64
+
+	// usage is the current usage of the filesystem.
+	//
+	// If usage is set to `-1`, it hasn't been calculated yet.
+	usage atomic.Int64
+}
+
+func NewQuota(fs *UnixFS, limit int64) *Quota {
+	qfs := Quota{UnixFS: fs}
+	qfs.limit.Store(limit)
+	return &qfs
+}
+
+// Close closes the filesystem.
+func (fs *Quota) Close() (err error) {
+	err = fs.UnixFS.Close()
+	return
+}
+
+// Limit returns the limit of the filesystem.
+func (fs *Quota) Limit() int64 {
+	return fs.limit.Load()
+}
+
+// SetLimit returns the limit of the filesystem.
+func (fs *Quota) SetLimit(newLimit int64) int64 {
+	return fs.limit.Swap(newLimit)
+}
+
+// Usage returns the current usage of the filesystem.
+func (fs *Quota) Usage() int64 {
+	return fs.usage.Load()
+}
+
+// SetUsage updates the total usage of the filesystem.
+func (fs *Quota) SetUsage(newUsage int64) int64 {
+	return fs.usage.Swap(newUsage)
+}
+
+// Add adds `i` to the tracked usage total.
+func (fs *Quota) Add(i int64) int64 {
+	usage := fs.Usage()
+
+	// If adding `i` to the usage will put us below 0, cap it. (`i` can be negative)
+	if usage+i < 0 {
+		fs.usage.Store(0)
+		return 0
+	}
+	return fs.usage.Add(i)
+}
+
+// CanFit checks if the given size can fit in the filesystem without exceeding
+// the limit of the filesystem.
+func (fs *Quota) CanFit(size int64) bool {
+	// Get the size limit of the filesystem.
+	limit := fs.Limit()
+	switch limit {
+	case -1:
+		// A limit of -1 means no write operations are allowed.
+		return false
+	case 0:
+		// A limit of 0 means unlimited.
+		return true
+	}
+
+	// Any other limit is a value we need to check.
+	usage := fs.Usage()
+	if usage == -1 {
+		// We don't know what the current usage is yet.
+		return true
+	}
+
+	// If the current usage + the requested size are under the limit of the
+	// filesystem, allow it.
+	if usage+size <= limit {
+		return true
+	}
+
+	// Welp, the size would exceed the limit of the filesystem, deny it.
+	return false
+}
+
+func (fs *Quota) Remove(name string) error {
+	// For information on why this interface is used here, check its
+	// documentation.
+	s, err := fs.RemoveStat(name)
+	if err != nil {
+		return err
+	}
+
+	// Don't reduce the quota's usage as `name` is not a regular file.
+	if !s.Mode().IsRegular() {
+		return nil
+	}
+
+	// Remove the size of the deleted file from the quota usage.
+	fs.Add(-s.Size())
+	return nil
+}
+
+// RemoveAll removes path and any children it contains.
+//
+// It removes everything it can but returns the first error
+// it encounters. If the path does not exist, RemoveAll
+// returns nil (no error).
+//
+// If there is an error, it will be of type *PathError.
+func (fs *Quota) RemoveAll(name string) error {
+	name, err := fs.unsafePath(name)
+	if err != nil {
+		return err
+	}
+	// While removeAll internally checks this, I want to make sure we check it
+	// and return the proper error so our tests can ensure that this will never
+	// be a possibility.
+	if name == "." {
+		return &PathError{
+			Op:   "removeall",
+			Path: name,
+			Err:  ErrBadPathResolution,
+		}
+	}
+	return fs.removeAll(name)
+}
+
+func (fs *Quota) removeAll(path string) error {
+	return removeAll(fs, path)
+}
+
+func (fs *Quota) unlinkat(dirfd int, name string, flags int) error {
+	if flags == 0 {
+		s, err := fs.Lstatat(dirfd, name)
+		if err == nil && s.Mode().IsRegular() {
+			fs.Add(-s.Size())
+		}
+	}
+	return fs.UnixFS.unlinkat(dirfd, name, flags)
+}

internal/ufs/fs_unix.go

@@ -0,0 +1,825 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+//go:build unix
+
+package ufs
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+// UnixFS is a filesystem that uses the unix package to make io calls.
+//
+// This is used for proper sand-boxing and full control over the exact syscalls
+// being performed.
+type UnixFS struct {
+	// basePath is the base path for file operations to take place in.
+	basePath string
+
+	// dirfd holds the file descriptor of BasePath and is used to ensure
+	// operations are restricted into descendants of BasePath.
+	dirfd atomic.Int64
+
+	// useOpenat2 controls whether the `openat2` syscall is used instead of the
+	// older `openat` syscall.
+	useOpenat2 bool
+}
+
+// NewUnixFS creates a new sandboxed unix filesystem. BasePath is used as the
+// sandbox path, operations on BasePath itself are not allowed, but any
+// operations on its descendants are. Symlinks pointing outside BasePath are
+// checked and prevented from enabling an escape in a non-raceable manor.
+func NewUnixFS(basePath string, useOpenat2 bool) (*UnixFS, error) {
+	basePath = strings.TrimSuffix(basePath, "/")
+	// We don't need Openat2, if we are given a basePath that is already unsafe
+	// I give up on trying to sandbox it.
+	dirfd, err := unix.Openat(AT_EMPTY_PATH, basePath, O_DIRECTORY|O_RDONLY, 0)
+	if err != nil {
+		return nil, convertErrorType(err)
+	}
+
+	fs := &UnixFS{
+		basePath:   basePath,
+		useOpenat2: useOpenat2,
+	}
+	fs.dirfd.Store(int64(dirfd))
+	return fs, nil
+}
+
+// BasePath returns the base path of the UnixFS sandbox, file operations
+// pointing outside this path are prohibited and will be blocked by all
+// operations implemented by UnixFS.
+func (fs *UnixFS) BasePath() string {
+	return fs.basePath
+}
+
+// Close releases the file descriptor used to sandbox operations within the
+// base path of the filesystem.
+func (fs *UnixFS) Close() error {
+	// Once closed, change dirfd to something invalid to detect when it has been
+	// closed.
+	defer func() {
+		fs.dirfd.Store(-1)
+	}()
+	return unix.Close(int(fs.dirfd.Load()))
+}
+
+// Chmod changes the mode of the named file to mode.
+//
+// If the file is a symbolic link, it changes the mode of the link's target.
+// If there is an error, it will be of type *PathError.
+//
+// A different subset of the mode bits are used, depending on the
+// operating system.
+//
+// On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
+// ModeSticky are used.
+//
+// On Windows, only the 0200 bit (owner writable) of mode is used; it
+// controls whether the file's read-only attribute is set or cleared.
+// The other bits are currently unused. For compatibility with Go 1.12
+// and earlier, use a non-zero mode. Use mode 0400 for a read-only
+// file and 0600 for a readable+writable file.
+//
+// On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
+// and ModeTemporary are used.
+func (fs *UnixFS) Chmod(name string, mode FileMode) error {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	return convertErrorType(unix.Fchmodat(dirfd, name, uint32(mode), 0))
+}
+
+// Chown changes the numeric uid and gid of the named file.
+//
+// If the file is a symbolic link, it changes the uid and gid of the link's target.
+// A uid or gid of -1 means to not change that value.
+// If there is an error, it will be of type *PathError.
+//
+// On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
+// EPLAN9 error, wrapped in *PathError.
+func (fs *UnixFS) Chown(name string, uid, gid int) error {
+	return fs.fchown(name, uid, gid, 0)
+}
+
+// Lchown changes the numeric uid and gid of the named file.
+//
+// If the file is a symbolic link, it changes the uid and gid of the link itself.
+// If there is an error, it will be of type *PathError.
+//
+// On Windows, it always returns the syscall.EWINDOWS error, wrapped
+// in *PathError.
+func (fs *UnixFS) Lchown(name string, uid, gid int) error {
+	// With AT_SYMLINK_NOFOLLOW, Fchownat acts like Lchown but allows us to
+	// pass a dirfd.
+	return fs.fchown(name, uid, gid, AT_SYMLINK_NOFOLLOW)
+}
+
+// fchown is a re-usable Fchownat syscall used by Chown and Lchown.
+func (fs *UnixFS) fchown(name string, uid, gid, flags int) error {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	return convertErrorType(unix.Fchownat(dirfd, name, uid, gid, flags))
+}
+
+// Chownat is like Chown but allows passing an existing directory file
+// descriptor rather than needing to resolve one.
+func (fs *UnixFS) Chownat(dirfd int, name string, uid, gid int) error {
+	return convertErrorType(unix.Fchownat(dirfd, name, uid, gid, 0))
+}
+
+// Lchownat is like Lchown but allows passing an existing directory file
+// descriptor rather than needing to resolve one.
+func (fs *UnixFS) Lchownat(dirfd int, name string, uid, gid int) error {
+	return convertErrorType(unix.Fchownat(dirfd, name, uid, gid, AT_SYMLINK_NOFOLLOW))
+}
+
+// Chtimes changes the access and modification times of the named
+// file, similar to the Unix utime() or utimes() functions.
+//
+// The underlying filesystem may truncate or round the values to a
+// less precise time unit.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Chtimes(name string, atime, mtime time.Time) error {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	return fs.Chtimesat(dirfd, name, atime, mtime)
+}
+
+// Chtimesat is like Chtimes but allows passing an existing directory file
+// descriptor rather than needing to resolve one.
+func (fs *UnixFS) Chtimesat(dirfd int, name string, atime, mtime time.Time) error {
+	var utimes [2]unix.Timespec
+	set := func(i int, t time.Time) {
+		if t.IsZero() {
+			utimes[i] = unix.Timespec{Sec: unix.UTIME_OMIT, Nsec: unix.UTIME_OMIT}
+		} else {
+			utimes[i] = unix.NsecToTimespec(t.UnixNano())
+		}
+	}
+	set(0, atime)
+	set(1, mtime)
+	// This does support `AT_SYMLINK_NOFOLLOW` as well if needed.
+	if err := unix.UtimesNanoAt(dirfd, name, utimes[0:], 0); err != nil {
+		return convertErrorType(&PathError{Op: "chtimes", Path: name, Err: err})
+	}
+	return nil
+}
+
+// Create creates or truncates the named file. If the file already exists,
+// it is truncated.
+//
+// If the file does not exist, it is created with mode 0666
+// (before umask). If successful, methods on the returned File can
+// be used for I/O; the associated file descriptor has mode O_RDWR.
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Create(name string) (File, error) {
+	return fs.OpenFile(name, O_CREATE|O_WRONLY|O_TRUNC, 0o644)
+}
+
+// Mkdir creates a new directory with the specified name and permission
+// bits (before umask).
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Mkdir(name string, mode FileMode) error {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	return fs.Mkdirat(dirfd, name, mode)
+}
+
+func (fs *UnixFS) Mkdirat(dirfd int, name string, mode FileMode) error {
+	return convertErrorType(unix.Mkdirat(dirfd, name, uint32(mode)))
+}
+
+// MkdirAll creates a directory named path, along with any necessary
+// parents, and returns nil, or else returns an error.
+//
+// The permission bits perm (before umask) are used for all
+// directories that MkdirAll creates.
+// If path is already a directory, MkdirAll does nothing
+// and returns nil.
+func (fs *UnixFS) MkdirAll(name string, mode FileMode) error {
+	// Ensure name is somewhat clean before continuing.
+	name, err := fs.unsafePath(name)
+	if err != nil {
+		return err
+	}
+	return fs.mkdirAll(name, mode)
+}
+
+// Open opens the named file for reading.
+//
+// If successful, methods on the returned file can be used for reading; the
+// associated file descriptor has mode O_RDONLY.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Open(name string) (File, error) {
+	return fs.OpenFile(name, O_RDONLY, 0)
+}
+
+// OpenFile is the generalized open call; most users will use Open
+// or Create instead. It opens the named file with specified flag
+// (O_RDONLY etc.).
+//
+// If the file does not exist, and the O_CREATE flag
+// is passed, it is created with mode perm (before umask). If successful,
+// methods on the returned File can be used for I/O.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) OpenFile(name string, flag int, mode FileMode) (File, error) {
+	fd, err := fs.openFile(name, flag, mode)
+	if err != nil {
+		return nil, err
+	}
+	// Do not close `fd` here, it is passed to a file that needs the fd, the
+	// caller of this function is responsible for calling Close() on the File
+	// to release the file descriptor.
+	return os.NewFile(uintptr(fd), name), nil
+}
+
+func (fs *UnixFS) openFile(name string, flag int, mode FileMode) (int, error) {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return 0, err
+	}
+	return fs.openat(dirfd, name, flag, mode)
+}
+
+func (fs *UnixFS) OpenFileat(dirfd int, name string, flag int, mode FileMode) (File, error) {
+	fd, err := fs.openat(dirfd, name, flag, mode)
+	if err != nil {
+		return nil, err
+	}
+	// Do not close `fd` here, it is passed to a file that needs the fd, the
+	// caller of this function is responsible for calling Close() on the File
+	// to release the file descriptor.
+	return os.NewFile(uintptr(fd), name), nil
+}
+
+// ReadDir reads the named directory,
+//
+// returning all its directory entries sorted by filename.
+// If an error occurs reading the directory, ReadDir returns the entries it
+// was able to read before the error, along with the error.
+func (fs *UnixFS) ReadDir(path string) ([]DirEntry, error) {
+	dirfd, name, closeFd, err := fs.safePath(path)
+	defer closeFd()
+	if err != nil {
+		return nil, err
+	}
+	fd, err := fs.openat(dirfd, name, O_DIRECTORY|O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer unix.Close(fd)
+	return fs.readDir(fd, name, nil)
+}
+
+// RemoveStat is a combination of Stat and Remove, it is used to more
+// efficiently remove a file when the caller needs to stat it before
+// removing it.
+//
+// This optimized function exists for our QuotaFS abstraction, which needs
+// to track writes to a filesystem. When removing a file, the QuotaFS needs
+// to know if the entry is a file and if so, how large it is. Because we
+// need to Stat a file in order to get its mode and size, we will already
+// know if the entry needs to be removed by using Unlink or Rmdir. The
+// standard `Remove` method just tries both Unlink and Rmdir (in that order)
+// as it ends up usually being faster and more efficient than calling Stat +
+// the proper operation in the first place.
+func (fs *UnixFS) RemoveStat(name string) (FileInfo, error) {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return nil, err
+	}
+
+	// Lstat name, we use Lstat as Unlink doesn't care about symlinks.
+	s, err := fs.Lstatat(dirfd, name)
+	if err != nil {
+		return nil, err
+	}
+
+	if s.IsDir() {
+		err = fs.unlinkat(dirfd, name, AT_REMOVEDIR) // Rmdir
+	} else {
+		err = fs.unlinkat(dirfd, name, 0)
+	}
+	if err != nil {
+		return s, convertErrorType(&PathError{Op: "remove", Path: name, Err: err})
+	}
+	return s, nil
+}
+
+// Remove removes the named file or (empty) directory.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Remove(name string) error {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+
+	// Prevent trying to Remove the base directory.
+	if name == "." {
+		return &PathError{
+			Op:   "remove",
+			Path: name,
+			Err:  ErrBadPathResolution,
+		}
+	}
+
+	// System call interface forces us to know
+	// whether name is a file or directory.
+	// Try both: it is cheaper on average than
+	// doing a Stat plus the right one.
+	err = fs.unlinkat(dirfd, name, 0)
+	if err == nil {
+		return nil
+	}
+	err1 := fs.unlinkat(dirfd, name, AT_REMOVEDIR) // Rmdir
+	if err1 == nil {
+		return nil
+	}
+
+	// Both failed: figure out which error to return.
+	// OS X and Linux differ on whether unlink(dir)
+	// returns EISDIR, so can't use that. However,
+	// both agree that rmdir(file) returns ENOTDIR,
+	// so we can use that to decide which error is real.
+	// Rmdir might also return ENOTDIR if given a bad
+	// file path, like /etc/passwd/foo, but in that case,
+	// both errors will be ENOTDIR, so it's okay to
+	// use the error from unlink.
+	if err1 != unix.ENOTDIR {
+		err = err1
+	}
+	return convertErrorType(&PathError{Op: "remove", Path: name, Err: err})
+}
+
+// RemoveAll removes path and any children it contains.
+//
+// It removes everything it can but returns the first error
+// it encounters. If the path does not exist, RemoveAll
+// returns nil (no error).
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) RemoveAll(name string) error {
+	name, err := fs.unsafePath(name)
+	if err != nil {
+		return err
+	}
+	// While removeAll internally checks this, I want to make sure we check it
+	// and return the proper error so our tests can ensure that this will never
+	// be a possibility.
+	if name == "." {
+		return &PathError{
+			Op:   "removeall",
+			Path: name,
+			Err:  ErrBadPathResolution,
+		}
+	}
+	return fs.removeAll(name)
+}
+
+func (fs *UnixFS) unlinkat(dirfd int, name string, flags int) error {
+	return ignoringEINTR(func() error {
+		return unix.Unlinkat(dirfd, name, flags)
+	})
+}
+
+// Rename renames (moves) oldpath to newpath.
+//
+// If newpath already exists and is not a directory, Rename replaces it.
+// OS-specific restrictions may apply when oldpath and newpath are in different directories.
+// Even within the same directory, on non-Unix platforms Rename is not an atomic operation.
+//
+// If there is an error, it will be of type *LinkError.
+func (fs *UnixFS) Rename(oldpath, newpath string) error {
+	// Simple case: both paths are the same.
+	if oldpath == newpath {
+		return nil
+	}
+
+	olddirfd, oldname, closeFd, err := fs.safePath(oldpath)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	// Ensure that we are not trying to rename the base directory itself.
+	// While unix.Renameat ends up throwing a "device or resource busy" error,
+	// that doesn't mean we are protecting the system properly.
+	if oldname == "." {
+		return convertErrorType(&PathError{
+			Op:   "rename",
+			Path: oldname,
+			Err:  ErrBadPathResolution,
+		})
+	}
+	// Stat the old target to return proper errors.
+	if _, err := fs.Lstatat(olddirfd, oldname); err != nil {
+		return err
+	}
+
+	newdirfd, newname, closeFd2, err := fs.safePath(newpath)
+	if err != nil {
+		closeFd2()
+		if !errors.Is(err, ErrNotExist) {
+			return convertErrorType(err)
+		}
+		var pathErr *PathError
+		if !errors.As(err, &pathErr) {
+			return convertErrorType(err)
+		}
+		if err := fs.MkdirAll(pathErr.Path, 0o755); err != nil {
+			return err
+		}
+		newdirfd, newname, closeFd2, err = fs.safePath(newpath)
+		defer closeFd2()
+		if err != nil {
+			return err
+		}
+	} else {
+		defer closeFd2()
+	}
+
+	// Ensure that we are not trying to rename the base directory itself.
+	// While unix.Renameat ends up throwing a "device or resource busy" error,
+	// that doesn't mean we are protecting the system properly.
+	if newname == "." {
+		return convertErrorType(&PathError{
+			Op:   "rename",
+			Path: newname,
+			Err:  ErrBadPathResolution,
+		})
+	}
+	// Stat the new target to return proper errors.
+	_, err = fs.Lstatat(newdirfd, newname)
+	switch {
+	case err == nil:
+		return convertErrorType(&PathError{
+			Op:   "rename",
+			Path: newname,
+			Err:  ErrExist,
+		})
+	case !errors.Is(err, ErrNotExist):
+		return err
+	}
+	return unix.Renameat(olddirfd, oldname, newdirfd, newname)
+}
+
+// Stat returns a FileInfo describing the named file.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Stat(name string) (FileInfo, error) {
+	return fs.fstat(name, 0)
+}
+
+// Statat is like Stat but allows passing an existing directory file
+// descriptor rather than needing to resolve one.
+func (fs *UnixFS) Statat(dirfd int, name string) (FileInfo, error) {
+	return fs.fstatat(dirfd, name, 0)
+}
+
+// Lstat returns a FileInfo describing the named file.
+//
+// If the file is a symbolic link, the returned FileInfo
+// describes the symbolic link. Lstat makes no attempt to follow the link.
+//
+// If there is an error, it will be of type *PathError.
+func (fs *UnixFS) Lstat(name string) (FileInfo, error) {
+	return fs.fstat(name, AT_SYMLINK_NOFOLLOW)
+}
+
+// Lstatat is like Lstat but allows passing an existing directory file
+// descriptor rather than needing to resolve one.
+func (fs *UnixFS) Lstatat(dirfd int, name string) (FileInfo, error) {
+	return fs.fstatat(dirfd, name, AT_SYMLINK_NOFOLLOW)
+}
+
+func (fs *UnixFS) fstat(name string, flags int) (FileInfo, error) {
+	dirfd, name, closeFd, err := fs.safePath(name)
+	defer closeFd()
+	if err != nil {
+		return nil, err
+	}
+	return fs.fstatat(dirfd, name, flags)
+}
+
+func (fs *UnixFS) fstatat(dirfd int, name string, flags int) (FileInfo, error) {
+	var s fileStat
+	if err := ignoringEINTR(func() error {
+		return unix.Fstatat(dirfd, name, &s.sys, flags)
+	}); err != nil {
+		return nil, &PathError{Op: "stat", Path: name, Err: err}
+	}
+	fillFileStatFromSys(&s, name)
+	return &s, nil
+}
+
+// Symlink creates newname as a symbolic link to oldname.
+//
+// On Windows, a symlink to a non-existent oldname creates a file symlink;
+// if oldname is later created as a directory the symlink will not work.
+//
+// If there is an error, it will be of type *LinkError.
+func (fs *UnixFS) Symlink(oldpath, newpath string) error {
+	dirfd, newpath, closeFd, err := fs.safePath(newpath)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	if err := ignoringEINTR(func() error {
+		// We aren't concerned with oldpath here as a symlink can point anywhere
+		// it wants.
+		return unix.Symlinkat(oldpath, dirfd, newpath)
+	}); err != nil {
+		return &LinkError{Op: "symlink", Old: oldpath, New: newpath, Err: err}
+	}
+	return nil
+}
+
+// Touch will attempt to open a file for reading and/or writing. If the file
+// does not exist it will be created, and any missing parent directories will
+// also be created. The opened file may be truncated, only if `flag` has
+// O_TRUNC set.
+func (fs *UnixFS) Touch(path string, flag int, mode FileMode) (File, error) {
+	if flag&O_CREATE == 0 {
+		flag |= O_CREATE
+	}
+	dirfd, name, closeFd, err := fs.safePath(path)
+	defer closeFd()
+	if err == nil {
+		return fs.OpenFileat(dirfd, name, flag, mode)
+	}
+	if !errors.Is(err, ErrNotExist) {
+		return nil, err
+	}
+	var pathErr *PathError
+	if !errors.As(err, &pathErr) {
+		return nil, err
+	}
+	if err := fs.MkdirAll(pathErr.Path, 0o755); err != nil {
+		return nil, err
+	}
+	// Try to open the file one more time after creating its parent directories.
+	return fs.OpenFile(path, flag, mode)
+}
+
+// WalkDir walks the file tree rooted at root, calling fn for each file or
+// directory in the tree, including root.
+//
+// All errors that arise visiting files and directories are filtered by fn:
+// see the [WalkDirFunc] documentation for details.
+//
+// The files are walked in lexical order, which makes the output deterministic
+// but requires WalkDir to read an entire directory into memory before proceeding
+// to walk that directory.
+//
+// WalkDir does not follow symbolic links found in directories,
+// but if root itself is a symbolic link, its target will be walked.
+func (fs *UnixFS) WalkDir(root string, fn WalkDirFunc) error {
+	return WalkDir(fs, root, fn)
+}
+
+// openat is a wrapper around both unix.Openat and unix.Openat2. If the UnixFS
+// was configured to enable openat2 support, unix.Openat2 will be used instead
+// of unix.Openat due to having better security properties for our use-case.
+func (fs *UnixFS) openat(dirfd int, name string, flag int, mode FileMode) (int, error) {
+	if flag&O_NOFOLLOW == 0 {
+		flag |= O_NOFOLLOW
+	}
+
+	var fd int
+	for {
+		var err error
+		if fs.useOpenat2 {
+			fd, err = fs._openat2(dirfd, name, uint64(flag), uint64(syscallMode(mode)))
+		} else {
+			fd, err = fs._openat(dirfd, name, flag, uint32(syscallMode(mode)))
+		}
+		if err == nil {
+			break
+		}
+		// We have to check EINTR here, per issues https://go.dev/issue/11180 and https://go.dev/issue/39237.
+		if err == unix.EINTR {
+			continue
+		}
+		return 0, convertErrorType(err)
+	}
+
+	// If we are not using openat2, do additional path checking. This assumes
+	// that openat2 is using `RESOLVE_BENEATH` to avoid the same security
+	// issue.
+	if !fs.useOpenat2 {
+		var finalPath string
+		finalPath, err := filepath.EvalSymlinks(filepath.Join("/proc/self/fd/", strconv.Itoa(dirfd)))
+		if err != nil {
+			return fd, convertErrorType(err)
+		}
+		if err != nil {
+			if !errors.Is(err, ErrNotExist) {
+				return fd, fmt.Errorf("failed to evaluate symlink: %w", convertErrorType(err))
+			}
+
+			// The target of one of the symlinks (EvalSymlinks is recursive)
+			// does not exist. So get the path that does not exist and use
+			// that for further validation instead.
+			var pErr *PathError
+			if ok := errors.As(err, &pErr); !ok {
+				return fd, fmt.Errorf("failed to evaluate symlink: %w", convertErrorType(err))
+			}
+			finalPath = pErr.Path
+		}
+
+		// Check if the path is within our root.
+		if !fs.unsafeIsPathInsideOfBase(finalPath) {
+			return fd, convertErrorType(&PathError{
+				Op:   "openat",
+				Path: name,
+				Err:  ErrBadPathResolution,
+			})
+		}
+	}
+	return fd, nil
+}
+
+// _openat is a wrapper around unix.Openat. This method should never be directly
+// called, use `openat` instead.
+func (fs *UnixFS) _openat(dirfd int, name string, flag int, mode uint32) (int, error) {
+	// Ensure the O_CLOEXEC flag is set.
+	// Go sets this in the os package, but since we are directly using unix
+	// we need to set it ourselves.
+	if flag&O_CLOEXEC == 0 {
+		flag |= O_CLOEXEC
+	}
+	// O_LARGEFILE is set by Openat for us automatically.
+	fd, err := unix.Openat(dirfd, name, flag, mode)
+	switch {
+	case err == nil:
+		return fd, nil
+	case err == unix.EINTR:
+		return 0, err
+	case err == unix.EAGAIN:
+		return 0, err
+	default:
+		return 0, &PathError{Op: "openat", Path: name, Err: err}
+	}
+}
+
+// _openat2 is a wonderful syscall that supersedes the `openat` syscall. It has
+// improved validation and security characteristics that weren't available or
+// considered when `openat` was originally implemented. As such, it is only
+// present in Kernel 5.6 and above.
+//
+// This method should never be directly called, use `openat` instead.
+func (fs *UnixFS) _openat2(dirfd int, name string, flag uint64, mode uint64) (int, error) {
+	// Ensure the O_CLOEXEC flag is set.
+	// Go sets this when using the os package, but since we are directly using
+	// the unix package we need to set it ourselves.
+	if flag&O_CLOEXEC == 0 {
+		flag |= O_CLOEXEC
+	}
+	// Ensure the O_LARGEFILE flag is set.
+	// Go sets this for unix.Open, unix.Openat, but not unix.Openat2.
+	if flag&O_LARGEFILE == 0 {
+		flag |= O_LARGEFILE
+	}
+	fd, err := unix.Openat2(dirfd, name, &unix.OpenHow{
+		Flags: flag,
+		Mode:  mode,
+		// This is the bread and butter of preventing a symlink escape, without
+		// this option, we have to handle path validation fully on our own.
+		//
+		// This is why using Openat2 over Openat is preferred if available.
+		Resolve: unix.RESOLVE_BENEATH,
+	})
+	switch {
+	case err == nil:
+		return fd, nil
+	case err == unix.EINTR:
+		return 0, err
+	case err == unix.EAGAIN:
+		return 0, err
+	default:
+		return 0, &PathError{Op: "openat2", Path: name, Err: err}
+	}
+}
+
+func (fs *UnixFS) SafePath(path string) (int, string, func(), error) {
+	return fs.safePath(path)
+}
+
+func (fs *UnixFS) safePath(path string) (dirfd int, file string, closeFd func(), err error) {
+	// Default closeFd to a NO-OP.
+	closeFd = func() {}
+
+	// Use unsafePath to clean the path and strip BasePath if path is absolute.
+	var name string
+	name, err = fs.unsafePath(path)
+	if err != nil {
+		return
+	}
+
+	// Check if dirfd was closed, this will happen if (*UnixFS).Close()
+	// was called.
+	fsDirfd := int(fs.dirfd.Load())
+	if fsDirfd == -1 {
+		err = ErrClosed
+		return
+	}
+
+	// Split the parent from the last element in the path, this gives us the
+	// "file name" and the full path to its parent.
+	var dir string
+	dir, file = filepath.Split(name)
+	// If dir is empty then name is not nested.
+	if dir == "" {
+		// We don't need to set closeFd here as it will default to a NO-OP and
+		// `fs.dirfd` is re-used until the filesystem is no-longer needed.
+		dirfd = fsDirfd
+
+		// Return dirfd, name, an empty closeFd func, and no error
+		return
+	}
+
+	// Dir will usually contain a trailing slash as filepath.Split doesn't
+	// trim slashes.
+	dir = strings.TrimSuffix(dir, "/")
+	dirfd, err = fs.openat(fsDirfd, dir, O_DIRECTORY|O_RDONLY, 0)
+	if dirfd != 0 {
+		// Set closeFd to close the newly opened directory file descriptor.
+		closeFd = func() { _ = unix.Close(dirfd) }
+	}
+
+	// Return dirfd, name, the closeFd func, and err
+	return
+}
+
+// unsafePath prefixes the given path and prefixes it with the filesystem's
+// base path, cleaning the result. The path returned by this function may not
+// be inside the filesystem's base path, additional checks are required to
+// safely use paths returned by this function.
+func (fs *UnixFS) unsafePath(path string) (string, error) {
+	// Calling filepath.Clean on the joined directory will resolve it to the
+	// absolute path, removing any ../ type of resolution arguments, and leaving
+	// us with a direct path link.
+	//
+	// This will also trim the existing root path off the beginning of the path
+	// passed to the function since that can get a bit messy.
+	r := filepath.Clean(filepath.Join(fs.basePath, strings.TrimPrefix(path, fs.basePath)))
+
+	if fs.unsafeIsPathInsideOfBase(r) {
+		// This is kinda ironic isn't it.
+		// We do this as we are operating with dirfds and `*at` syscalls which
+		// behave differently if given an absolute path.
+		//
+		// First trim the BasePath, then trim any leading slashes.
+		r = strings.TrimPrefix(strings.TrimPrefix(r, fs.basePath), "/")
+		// If the path is empty then return "." as the path is pointing to the
+		// root.
+		if r == "" {
+			return ".", nil
+		}
+		return r, nil
+	}
+
+	return "", &PathError{
+		Op:   "safePath",
+		Path: path,
+		Err:  ErrBadPathResolution,
+	}
+}
+
+// unsafeIsPathInsideOfBase checks if the given path is inside the filesystem's
+// base path.
+func (fs *UnixFS) unsafeIsPathInsideOfBase(path string) bool {
+	return strings.HasPrefix(
+		strings.TrimSuffix(path, "/")+"/",
+		fs.basePath+"/",
+	)
+}

internal/ufs/fs_unix_test.go

@@ -0,0 +1,255 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+//go:build unix
+
+package ufs_test
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/pterodactyl/wings/internal/ufs"
+)
+
+type testUnixFS struct {
+	*ufs.UnixFS
+
+	TmpDir string
+	Root   string
+}
+
+func (fs *testUnixFS) Cleanup() {
+	_ = fs.Close()
+	_ = os.RemoveAll(fs.TmpDir)
+}
+
+func newTestUnixFS() (*testUnixFS, error) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "ufs")
+	if err != nil {
+		return nil, err
+	}
+	root := filepath.Join(tmpDir, "root")
+	if err := os.Mkdir(root, 0o755); err != nil {
+		return nil, err
+	}
+	// TODO: test both disabled and enabled.
+	fs, err := ufs.NewUnixFS(root, false)
+	if err != nil {
+		return nil, err
+	}
+	tfs := &testUnixFS{
+		UnixFS: fs,
+		TmpDir: tmpDir,
+		Root:   root,
+	}
+	return tfs, nil
+}
+
+func TestUnixFS_Remove(t *testing.T) {
+	t.Parallel()
+	fs, err := newTestUnixFS()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+	defer fs.Cleanup()
+
+	t.Run("base directory", func(t *testing.T) {
+		// Try to remove the base directory.
+		if err := fs.Remove(""); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+
+	t.Run("path traversal", func(t *testing.T) {
+		// Try to remove the base directory.
+		if err := fs.RemoveAll("../root"); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+}
+
+func TestUnixFS_RemoveAll(t *testing.T) {
+	t.Parallel()
+	fs, err := newTestUnixFS()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+	defer fs.Cleanup()
+
+	t.Run("base directory", func(t *testing.T) {
+		// Try to remove the base directory.
+		if err := fs.RemoveAll(""); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+
+	t.Run("path traversal", func(t *testing.T) {
+		// Try to remove the base directory.
+		if err := fs.RemoveAll("../root"); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+}
+
+func TestUnixFS_Rename(t *testing.T) {
+	t.Parallel()
+	fs, err := newTestUnixFS()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+	defer fs.Cleanup()
+
+	t.Run("rename base directory", func(t *testing.T) {
+		// Try to rename the base directory.
+		if err := fs.Rename("", "yeet"); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+
+	t.Run("rename over base directory", func(t *testing.T) {
+		// Create a directory that we are going to try and move over top of the
+		// existing base directory.
+		if err := fs.Mkdir("overwrite_dir", 0o755); err != nil {
+			t.Error(err)
+			return
+		}
+
+		// Try to rename over the base directory.
+		if err := fs.Rename("overwrite_dir", ""); !errors.Is(err, ufs.ErrBadPathResolution) {
+			t.Errorf("expected an a bad path resolution error, but got: %v", err)
+			return
+		}
+	})
+
+	t.Run("directory rename", func(t *testing.T) {
+		// Create a directory to rename to something else.
+		if err := fs.Mkdir("test_directory", 0o755); err != nil {
+			t.Error(err)
+			return
+		}
+
+		// Try to rename "test_directory" to "directory".
+		if err := fs.Rename("test_directory", "directory"); err != nil {
+			t.Errorf("expected no error, but got: %v", err)
+			return
+		}
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, "directory")); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+
+	t.Run("file rename", func(t *testing.T) {
+		// Create a directory to rename to something else.
+		if f, err := fs.Create("test_file"); err != nil {
+			t.Error(err)
+			return
+		} else {
+			_ = f.Close()
+		}
+
+		// Try to rename "test_file" to "file".
+		if err := fs.Rename("test_file", "file"); err != nil {
+			t.Errorf("expected no error, but got: %v", err)
+			return
+		}
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, "file")); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+}
+
+func TestUnixFS_Touch(t *testing.T) {
+	t.Parallel()
+	fs, err := newTestUnixFS()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+	defer fs.Cleanup()
+
+	t.Run("base directory", func(t *testing.T) {
+		path := "i_touched_a_file"
+		f, err := fs.Touch(path, ufs.O_RDWR, 0o644)
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		_ = f.Close()
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, path)); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+
+	t.Run("existing parent directory", func(t *testing.T) {
+		dir := "some_parent_directory"
+		if err := fs.Mkdir(dir, 0o755); err != nil {
+			t.Errorf("error creating parent directory: %v", err)
+			return
+		}
+		path := filepath.Join(dir, "i_touched_a_file")
+		f, err := fs.Touch(path, ufs.O_RDWR, 0o644)
+		if err != nil {
+			t.Errorf("error touching file: %v", err)
+			return
+		}
+		_ = f.Close()
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, path)); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+
+	t.Run("non-existent parent directory", func(t *testing.T) {
+		path := "some_other_directory/i_touched_a_file"
+		f, err := fs.Touch(path, ufs.O_RDWR, 0o644)
+		if err != nil {
+			t.Errorf("error touching file: %v", err)
+			return
+		}
+		_ = f.Close()
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, path)); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+
+	t.Run("non-existent parent directories", func(t *testing.T) {
+		path := "some_other_directory/some_directory/i_touched_a_file"
+		f, err := fs.Touch(path, ufs.O_RDWR, 0o644)
+		if err != nil {
+			t.Errorf("error touching file: %v", err)
+			return
+		}
+		_ = f.Close()
+
+		// Sanity check
+		if _, err := os.Lstat(filepath.Join(fs.Root, path)); err != nil {
+			t.Errorf("Lstat errored when performing sanity check: %v", err)
+			return
+		}
+	})
+}

internal/ufs/go.LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

internal/ufs/mkdir_unix.go

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was derived from `go/src/os/path.go`.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+//go:build unix
+
+package ufs
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// mkdirAll is a recursive Mkdir implementation that properly handles symlinks.
+func (fs *UnixFS) mkdirAll(name string, mode FileMode) error {
+	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
+	dir, err := fs.Lstat(name)
+	if err == nil {
+		if dir.Mode()&ModeSymlink != 0 {
+			// If the final path is a symlink, resolve its target and use that
+			// to check instead.
+			dir, err = fs.Stat(name)
+			if err != nil {
+				return err
+			}
+		}
+		if dir.IsDir() {
+			return nil
+		}
+		return convertErrorType(&PathError{Op: "mkdir", Path: name, Err: unix.ENOTDIR})
+	}
+
+	// Slow path: make sure parent exists and then call Mkdir for path.
+	i := len(name)
+	for i > 0 && name[i-1] == '/' { // Skip trailing path separator.
+		i--
+	}
+
+	j := i
+	for j > 0 && name[j-1] != '/' { // Scan backward over element.
+		j--
+	}
+
+	if j > 1 {
+		// Create parent.
+		err = fs.mkdirAll(name[:j-1], mode)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Parent now exists; invoke Mkdir and use its result.
+	err = fs.Mkdir(name, mode)
+	if err != nil {
+		// Handle arguments like "foo/." by
+		// double-checking that directory doesn't exist.
+		dir, err1 := fs.Lstat(name)
+		if err1 == nil && dir.IsDir() {
+			return nil
+		}
+		return err
+	}
+	return nil
+}

internal/ufs/path_unix.go

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was copied from `go/src/os/path.go`
+// and `go/src/os/path_unix.go`.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+//go:build unix
+
+package ufs
+
+import (
+	"os"
+)
+
+// basename removes trailing slashes and the leading directory name from path name.
+func basename(name string) string {
+	i := len(name) - 1
+	// Remove trailing slashes
+	for ; i > 0 && name[i] == '/'; i-- {
+		name = name[:i]
+	}
+	// Remove leading directory name
+	for i--; i >= 0; i-- {
+		if name[i] == '/' {
+			name = name[i+1:]
+			break
+		}
+	}
+	return name
+}
+
+// endsWithDot reports whether the final component of path is ".".
+func endsWithDot(path string) bool {
+	if path == "." {
+		return true
+	}
+	if len(path) >= 2 && path[len(path)-1] == '.' && os.IsPathSeparator(path[len(path)-2]) {
+		return true
+	}
+	return false
+}
+
+// splitPath returns the base name and parent directory.
+func splitPath(path string) (string, string) {
+	// if no better parent is found, the path is relative from "here"
+	dirname := "."
+
+	// Remove all but one leading slash.
+	for len(path) > 1 && path[0] == '/' && path[1] == '/' {
+		path = path[1:]
+	}
+
+	i := len(path) - 1
+
+	// Remove trailing slashes.
+	for ; i > 0 && path[i] == '/'; i-- {
+		path = path[:i]
+	}
+
+	// if no slashes in path, base is path
+	basename := path
+
+	// Remove leading directory path
+	for i--; i >= 0; i-- {
+		if path[i] == '/' {
+			if i == 0 {
+				dirname = path[:1]
+			} else {
+				dirname = path[:i]
+			}
+			basename = path[i+1:]
+			break
+		}
+	}
+
+	return dirname, basename
+}

internal/ufs/quota_writer.go

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (c) 2024 Matthew Penner
+
+package ufs
+
+import (
+	"errors"
+	"io"
+	"sync/atomic"
+)
+
+// CountedWriter is a writer that counts the amount of data written to the
+// underlying writer.
+type CountedWriter struct {
+	File
+
+	counter atomic.Int64
+	err     error
+}
+
+// NewCountedWriter returns a new countedWriter that counts the amount of bytes
+// written to the underlying writer.
+func NewCountedWriter(f File) *CountedWriter {
+	return &CountedWriter{File: f}
+}
+
+// BytesWritten returns the amount of bytes that have been written to the
+// underlying writer.
+func (w *CountedWriter) BytesWritten() int64 {
+	return w.counter.Load()
+}
+
+// Error returns the error from the writer if any. If the error is an EOF, nil
+// will be returned.
+func (w *CountedWriter) Error() error {
+	if errors.Is(w.err, io.EOF) {
+		return nil
+	}
+	return w.err
+}
+
+// Write writes bytes to the underlying writer while tracking the total amount
+// of bytes written.
+func (w *CountedWriter) Write(p []byte) (int, error) {
+	if w.err != nil {
+		return 0, io.EOF
+	}
+
+	// Write is a very simple operation for us to handle.
+	n, err := w.File.Write(p)
+	w.counter.Add(int64(n))
+	w.err = err
+
+	// TODO: is this how we actually want to handle errors with this?
+	if err == io.EOF {
+		return n, io.EOF
+	} else {
+		return n, nil
+	}
+}
+
+func (w *CountedWriter) ReadFrom(r io.Reader) (n int64, err error) {
+	cr := NewCountedReader(r)
+	n, err = w.File.ReadFrom(cr)
+	w.counter.Add(n)
+	return
+}
+
+// CountedReader is a reader that counts the amount of data read from the
+// underlying reader.
+type CountedReader struct {
+	reader io.Reader
+
+	counter atomic.Int64
+	err     error
+}
+
+var _ io.Reader = (*CountedReader)(nil)
+
+// NewCountedReader returns a new countedReader that counts the amount of bytes
+// read from the underlying reader.
+func NewCountedReader(r io.Reader) *CountedReader {
+	return &CountedReader{reader: r}
+}
+
+// BytesRead returns the amount of bytes that have been read from the underlying
+// reader.
+func (r *CountedReader) BytesRead() int64 {
+	return r.counter.Load()
+}
+
+// Error returns the error from the reader if any. If the error is an EOF, nil
+// will be returned.
+func (r *CountedReader) Error() error {
+	if errors.Is(r.err, io.EOF) {
+		return nil
+	}
+	return r.err
+}
+
+// Read reads bytes from the underlying reader while tracking the total amount
+// of bytes read.
+func (r *CountedReader) Read(p []byte) (int, error) {
+	if r.err != nil {
+		return 0, io.EOF
+	}
+
+	n, err := r.reader.Read(p)
+	r.counter.Add(int64(n))
+	r.err = err
+
+	if err == io.EOF {
+		return n, io.EOF
+	} else {
+		return n, nil
+	}
+}

internal/ufs/removeall_unix.go

@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was derived from `go/src/os/removeall_at.go`.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+//go:build unix
+
+package ufs
+
+import (
+	"errors"
+	"io"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+type unixFS interface {
+	Open(name string) (File, error)
+	Remove(name string) error
+	unlinkat(dirfd int, path string, flags int) error
+}
+
+func (fs *UnixFS) removeAll(path string) error {
+	return removeAll(fs, path)
+}
+
+func removeAll(fs unixFS, path string) error {
+	if path == "" {
+		// fail silently to retain compatibility with previous behavior
+		// of RemoveAll. See issue https://go.dev/issue/28830.
+		return nil
+	}
+
+	// The rmdir system call does not permit removing ".",
+	// so we don't permit it either.
+	if endsWithDot(path) {
+		return &PathError{Op: "removeall", Path: path, Err: unix.EINVAL}
+	}
+
+	// Simple case: if Remove works, we're done.
+	err := fs.Remove(path)
+	if err == nil || errors.Is(err, ErrNotExist) {
+		return nil
+	}
+
+	// RemoveAll recurses by deleting the path base from
+	// its parent directory
+	parentDir, base := splitPath(path)
+
+	parent, err := fs.Open(parentDir)
+	if errors.Is(err, ErrNotExist) {
+		// If parent does not exist, base cannot exist. Fail silently
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	defer parent.Close()
+
+	if err := removeAllFrom(fs, parent, base); err != nil {
+		if pathErr, ok := err.(*PathError); ok {
+			pathErr.Path = parentDir + string(os.PathSeparator) + pathErr.Path
+			err = pathErr
+		}
+		return convertErrorType(err)
+	}
+	return nil
+}
+
+func removeAllFrom(fs unixFS, parent File, base string) error {
+	parentFd := int(parent.Fd())
+	// Simple case: if Unlink (aka remove) works, we're done.
+	err := fs.unlinkat(parentFd, base, 0)
+	if err == nil || errors.Is(err, ErrNotExist) {
+		return nil
+	}
+
+	// EISDIR means that we have a directory, and we need to
+	// remove its contents.
+	// EPERM or EACCES means that we don't have write permission on
+	// the parent directory, but this entry might still be a directory
+	// whose contents need to be removed.
+	// Otherwise, just return the error.
+	if err != unix.EISDIR && err != unix.EPERM && err != unix.EACCES {
+		return &PathError{Op: "unlinkat", Path: base, Err: err}
+	}
+
+	// Is this a directory we need to recurse into?
+	var statInfo unix.Stat_t
+	statErr := ignoringEINTR(func() error {
+		return unix.Fstatat(parentFd, base, &statInfo, AT_SYMLINK_NOFOLLOW)
+	})
+	if statErr != nil {
+		if errors.Is(statErr, ErrNotExist) {
+			return nil
+		}
+		return &PathError{Op: "fstatat", Path: base, Err: statErr}
+	}
+	if statInfo.Mode&unix.S_IFMT != unix.S_IFDIR {
+		// Not a directory; return the error from the unix.Unlinkat.
+		return &PathError{Op: "unlinkat", Path: base, Err: err}
+	}
+
+	// Remove the directory's entries.
+	var recurseErr error
+	for {
+		const reqSize = 1024
+		var respSize int
+
+		// Open the directory to recurse into
+		file, err := openFdAt(parentFd, base)
+		if err != nil {
+			if errors.Is(err, ErrNotExist) {
+				return nil
+			}
+			recurseErr = &PathError{Op: "openfdat", Path: base, Err: err}
+			break
+		}
+
+		for {
+			numErr := 0
+
+			names, readErr := file.Readdirnames(reqSize)
+			// Errors other than EOF should stop us from continuing.
+			if readErr != nil && readErr != io.EOF {
+				_ = file.Close()
+				if errors.Is(readErr, ErrNotExist) {
+					return nil
+				}
+				return &PathError{Op: "readdirnames", Path: base, Err: readErr}
+			}
+
+			respSize = len(names)
+			for _, name := range names {
+				err := removeAllFrom(fs, file, name)
+				if err != nil {
+					if pathErr, ok := err.(*PathError); ok {
+						pathErr.Path = base + string(os.PathSeparator) + pathErr.Path
+					}
+					numErr++
+					if recurseErr == nil {
+						recurseErr = err
+					}
+				}
+			}
+
+			// If we can delete any entry, break to start new iteration.
+			// Otherwise, we discard current names, get next entries and try deleting them.
+			if numErr != reqSize {
+				break
+			}
+		}
+
+		// Removing files from the directory may have caused
+		// the OS to reshuffle it. Simply calling Readdirnames
+		// again may skip some entries. The only reliable way
+		// to avoid this is to close and re-open the
+		// directory. See issue https://go.dev/issue/20841.
+		_ = file.Close()
+
+		// Finish when the end of the directory is reached
+		if respSize < reqSize {
+			break
+		}
+	}
+
+	// Remove the directory itself.
+	unlinkErr := fs.unlinkat(parentFd, base, AT_REMOVEDIR)
+	if unlinkErr == nil || errors.Is(unlinkErr, ErrNotExist) {
+		return nil
+	}
+
+	if recurseErr != nil {
+		return recurseErr
+	}
+	return &PathError{Op: "unlinkat", Path: base, Err: unlinkErr}
+}
+
+// openFdAt opens path relative to the directory in fd.
+// Other than that this should act like openFileNolog.
+// This acts like openFileNolog rather than OpenFile because
+// we are going to (try to) remove the file.
+// The contents of this file are not relevant for test caching.
+func openFdAt(dirfd int, name string) (File, error) {
+	var fd int
+	for {
+		var err error
+		fd, err = unix.Openat(dirfd, name, O_RDONLY|O_CLOEXEC|O_NOFOLLOW, 0)
+		if err == nil {
+			break
+		}
+
+		// See comment in openFileNolog.
+		if err == unix.EINTR {
+			continue
+		}
+
+		return nil, err
+	}
+	// This is stupid, os.NewFile immediately casts `fd` to an `int`, but wants
+	// it to be passed as a `uintptr`.
+	return os.NewFile(uintptr(fd), name), nil
+}

internal/ufs/stat_unix.go

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was copied from `go/src/os/stat_linux.go`
+// and `go/src/os/types_unix.go`.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+//go:build unix
+
+package ufs
+
+import (
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+type fileStat struct {
+	name    string
+	size    int64
+	mode    FileMode
+	modTime time.Time
+	sys     unix.Stat_t
+}
+
+var _ FileInfo = (*fileStat)(nil)
+
+func (fs *fileStat) Size() int64        { return fs.size }
+func (fs *fileStat) Mode() FileMode     { return fs.mode }
+func (fs *fileStat) ModTime() time.Time { return fs.modTime }
+func (fs *fileStat) Sys() any           { return &fs.sys }
+func (fs *fileStat) Name() string       { return fs.name }
+func (fs *fileStat) IsDir() bool        { return fs.Mode().IsDir() }
+
+func fillFileStatFromSys(fs *fileStat, name string) {
+	fs.name = basename(name)
+	fs.size = fs.sys.Size
+	fs.modTime = time.Unix(fs.sys.Mtim.Unix())
+	fs.mode = FileMode(fs.sys.Mode & 0o777)
+	switch fs.sys.Mode & unix.S_IFMT {
+	case unix.S_IFBLK:
+		fs.mode |= ModeDevice
+	case unix.S_IFCHR:
+		fs.mode |= ModeDevice | ModeCharDevice
+	case unix.S_IFDIR:
+		fs.mode |= ModeDir
+	case unix.S_IFIFO:
+		fs.mode |= ModeNamedPipe
+	case unix.S_IFLNK:
+		fs.mode |= ModeSymlink
+	case unix.S_IFREG:
+		// nothing to do
+	case unix.S_IFSOCK:
+		fs.mode |= ModeSocket
+	}
+	if fs.sys.Mode&unix.S_ISGID != 0 {
+		fs.mode |= ModeSetgid
+	}
+	if fs.sys.Mode&unix.S_ISUID != 0 {
+		fs.mode |= ModeSetuid
+	}
+	if fs.sys.Mode&unix.S_ISVTX != 0 {
+		fs.mode |= ModeSticky
+	}
+}

internal/ufs/walk.go

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code in this file was derived from `go/src/io/fs/walk.go`.
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the `go.LICENSE` file.
+
+package ufs
+
+import (
+	iofs "io/fs"
+	"path"
+)
+
+// SkipDir is used as a return value from [WalkDirFunc] to indicate that
+// the directory named in the call is to be skipped. It is not returned
+// as an error by any function.
+var SkipDir = iofs.SkipDir
+
+// SkipAll is used as a return value from [WalkDirFunc] to indicate that
+// all remaining files and directories are to be skipped. It is not returned
+// as an error by any function.
+var SkipAll = iofs.SkipAll
+
+// WalkDirFunc is the type of the function called by [WalkDir] to visit
+// each file or directory.
+//
+// The path argument contains the argument to [WalkDir] as a prefix.
+// That is, if WalkDir is called with root argument "dir" and finds a file
+// named "a" in that directory, the walk function will be called with
+// argument "dir/a".
+//
+// The d argument is the [DirEntry] for the named path.
+//
+// The error result returned by the function controls how [WalkDir]
+// continues. If the function returns the special value [SkipDir], WalkDir
+// skips the current directory (path if d.IsDir() is true, otherwise
+// path's parent directory). If the function returns the special value
+// [SkipAll], WalkDir skips all remaining files and directories. Otherwise,
+// if the function returns a non-nil error, WalkDir stops entirely and
+// returns that error.
+//
+// The err argument reports an error related to path, signaling that
+// [WalkDir] will not walk into that directory. The function can decide how
+// to handle that error; as described earlier, returning the error will
+// cause WalkDir to stop walking the entire tree.
+//
+// [WalkDir] calls the function with a non-nil err argument in two cases.
+//
+// First, if the initial [Stat] on the root directory fails, WalkDir
+// calls the function with path set to root, d set to nil, and err set to
+// the error from [fs.Stat].
+//
+// Second, if a directory's ReadDir method (see [ReadDirFile]) fails, WalkDir calls the
+// function with path set to the directory's path, d set to an
+// [DirEntry] describing the directory, and err set to the error from
+// ReadDir. In this second case, the function is called twice with the
+// path of the directory: the first call is before the directory read is
+// attempted and has err set to nil, giving the function a chance to
+// return [SkipDir] or [SkipAll] and avoid the ReadDir entirely. The second call
+// is after a failed ReadDir and reports the error from ReadDir.
+// (If ReadDir succeeds, there is no second call.)
+type WalkDirFunc func(path string, d DirEntry, err error) error
+
+// WalkDir walks the file tree rooted at root, calling fn for each file or
+// directory in the tree, including root.
+//
+// All errors that arise visiting files and directories are filtered by fn:
+// see the [WalkDirFunc] documentation for details.
+//
+// The files are walked in lexical order, which makes the output deterministic
+// but requires WalkDir to read an entire directory into memory before proceeding
+// to walk that directory.
+//
+// WalkDir does not follow symbolic links found in directories,
+// but if root itself is a symbolic link, its target will be walked.
+func WalkDir(fs Filesystem, root string, fn WalkDirFunc) error {
+	info, err := fs.Stat(root)
+	if err != nil {
+		err = fn(root, nil, err)
+	} else {
+		err = walkDir(fs, root, iofs.FileInfoToDirEntry(info), fn)
+	}
+	if err == SkipDir || err == SkipAll {
+		return nil
+	}
+	return err
+}
+
+// walkDir recursively descends path, calling walkDirFn.
+func walkDir(fs Filesystem, name string, d DirEntry, walkDirFn WalkDirFunc) error {
+	if err := walkDirFn(name, d, nil); err != nil || !d.IsDir() {
+		if err == SkipDir && d.IsDir() {
+			// Successfully skipped directory.
+			err = nil
+		}
+		return err
+	}
+
+	dirs, err := fs.ReadDir(name)
+	if err != nil {
+		// Second call, to report ReadDir error.
+		err = walkDirFn(name, d, err)
+		if err != nil {
+			if err == SkipDir && d.IsDir() {
+				err = nil
+			}
+			return err
+		}
+	}
+
+	for _, d1 := range dirs {
+		name1 := path.Join(name, d1.Name())
+		if err := walkDir(fs, name1, d1, walkDirFn); err != nil {
+			if err == SkipDir {
+				break
+			}
+			return err
+		}
+	}
+	return nil
+}

internal/ufs/walk_unix.go

@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: BSD-2-Clause
+
+// Some code in this file was derived from https://github.com/karrick/godirwalk.
+
+//go:build unix
+
+package ufs
+
+import (
+	"bytes"
+	iofs "io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"reflect"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+type WalkDiratFunc func(dirfd int, name, relative string, d DirEntry, err error) error
+
+func (fs *UnixFS) WalkDirat(dirfd int, name string, fn WalkDiratFunc) error {
+	if dirfd == 0 {
+		// TODO: proper validation, ideally a dedicated function.
+		dirfd = int(fs.dirfd.Load())
+	}
+	info, err := fs.Lstatat(dirfd, name)
+	if err != nil {
+		err = fn(dirfd, name, name, nil, err)
+	} else {
+		b := newScratchBuffer()
+		err = fs.walkDir(b, dirfd, name, name, iofs.FileInfoToDirEntry(info), fn)
+	}
+	if err == SkipDir || err == SkipAll {
+		return nil
+	}
+	return err
+}
+
+func (fs *UnixFS) walkDir(b []byte, parentfd int, name, relative string, d DirEntry, walkDirFn WalkDiratFunc) error {
+	if err := walkDirFn(parentfd, name, relative, d, nil); err != nil || !d.IsDir() {
+		if err == SkipDir && d.IsDir() {
+			// Successfully skipped directory.
+			err = nil
+		}
+		return err
+	}
+
+	dirfd, err := fs.openat(parentfd, name, O_DIRECTORY|O_RDONLY, 0)
+	if err != nil {
+		return err
+	}
+	defer unix.Close(dirfd)
+
+	dirs, err := fs.readDir(dirfd, name, b)
+	if err != nil {
+		// Second call, to report ReadDir error.
+		err = walkDirFn(dirfd, name, relative, d, err)
+		if err != nil {
+			if err == SkipDir && d.IsDir() {
+				err = nil
+			}
+			return err
+		}
+	}
+
+	for _, d1 := range dirs {
+		if err := fs.walkDir(b, dirfd, d1.Name(), path.Join(relative, d1.Name()), d1, walkDirFn); err != nil {
+			if err == SkipDir {
+				break
+			}
+			return err
+		}
+	}
+	return nil
+}
+
+// ReadDirMap .
+// TODO: document
+func ReadDirMap[T any](fs *UnixFS, path string, fn func(DirEntry) (T, error)) ([]T, error) {
+	dirfd, name, closeFd, err := fs.safePath(path)
+	defer closeFd()
+	if err != nil {
+		return nil, err
+	}
+	fd, err := fs.openat(dirfd, name, O_DIRECTORY|O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer unix.Close(fd)
+
+	entries, err := fs.readDir(fd, ".", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	out := make([]T, len(entries))
+	for i, e := range entries {
+		idx := i
+		e := e
+		v, err := fn(e)
+		if err != nil {
+			return nil, err
+		}
+		out[idx] = v
+	}
+	return out, nil
+}
+
+// nameOffset is a compile time constant
+const nameOffset = int(unsafe.Offsetof(unix.Dirent{}.Name))
+
+func nameFromDirent(de *unix.Dirent) (name []byte) {
+	// Because this GOOS' syscall.Dirent does not provide a field that specifies
+	// the name length, this function must first calculate the max possible name
+	// length, and then search for the NULL byte.
+	ml := int(de.Reclen) - nameOffset
+
+	// Convert syscall.Dirent.Name, which is array of int8, to []byte, by
+	// overwriting Cap, Len, and Data slice header fields to the max possible
+	// name length computed above, and finding the terminating NULL byte.
+	//
+	// TODO: is there an alternative to the deprecated SliceHeader?
+	// SliceHeader was mainly deprecated due to it being misused for avoiding
+	// allocations when converting a byte slice to a string, ref;
+	// https://go.dev/issue/53003
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&name))
+	sh.Cap = ml
+	sh.Len = ml
+	sh.Data = uintptr(unsafe.Pointer(&de.Name[0]))
+
+	if index := bytes.IndexByte(name, 0); index >= 0 {
+		// Found NULL byte; set slice's cap and len accordingly.
+		sh.Cap = index
+		sh.Len = index
+		return
+	}
+
+	// NOTE: This branch is not expected, but included for defensive
+	// programming, and provides a hard stop on the name based on the structure
+	// field array size.
+	sh.Cap = len(de.Name)
+	sh.Len = sh.Cap
+	return
+}
+
+// modeTypeFromDirent converts a syscall defined constant, which is in purview
+// of OS, to a constant defined by Go, assumed by this project to be stable.
+//
+// When the syscall constant is not recognized, this function falls back to a
+// Stat on the file system.
+func (fs *UnixFS) modeTypeFromDirent(fd int, de *unix.Dirent, osDirname, osBasename string) (FileMode, error) {
+	switch de.Type {
+	case unix.DT_REG:
+		return 0, nil
+	case unix.DT_DIR:
+		return ModeDir, nil
+	case unix.DT_LNK:
+		return ModeSymlink, nil
+	case unix.DT_CHR:
+		return ModeDevice | ModeCharDevice, nil
+	case unix.DT_BLK:
+		return ModeDevice, nil
+	case unix.DT_FIFO:
+		return ModeNamedPipe, nil
+	case unix.DT_SOCK:
+		return ModeSocket, nil
+	default:
+		// If syscall returned unknown type (e.g., DT_UNKNOWN, DT_WHT), then
+		// resolve actual mode by reading file information.
+		return fs.modeType(fd, filepath.Join(osDirname, osBasename))
+	}
+}
+
+// modeType returns the mode type of the file system entry identified by
+// osPathname by calling os.LStat function, to intentionally not follow symbolic
+// links.
+//
+// Even though os.LStat provides all file mode bits, we want to ensure same
+// values returned to caller regardless of whether we obtained file mode bits
+// from syscall or stat call. Therefore, mask out the additional file mode bits
+// that are provided by stat but not by the syscall, so users can rely on their
+// values.
+func (fs *UnixFS) modeType(dirfd int, name string) (os.FileMode, error) {
+	fi, err := fs.Lstatat(dirfd, name)
+	if err == nil {
+		return fi.Mode() & ModeType, nil
+	}
+	return 0, err
+}
+
+var minimumScratchBufferSize = os.Getpagesize()
+
+func newScratchBuffer() []byte {
+	return make([]byte, minimumScratchBufferSize)
+}
+
+func (fs *UnixFS) readDir(fd int, name string, b []byte) ([]DirEntry, error) {
+	scratchBuffer := b
+	if scratchBuffer == nil || len(scratchBuffer) < minimumScratchBufferSize {
+		scratchBuffer = newScratchBuffer()
+	}
+
+	var entries []DirEntry
+	var workBuffer []byte
+
+	var sde unix.Dirent
+	for {
+		if len(workBuffer) == 0 {
+			n, err := unix.Getdents(fd, scratchBuffer)
+			if err != nil {
+				if err == unix.EINTR {
+					continue
+				}
+				return nil, convertErrorType(err)
+			}
+			if n <= 0 {
+				// end of directory: normal exit
+				return entries, nil
+			}
+			workBuffer = scratchBuffer[:n] // trim work buffer to number of bytes read
+		}
+
+		// "Go is like C, except that you just put `unsafe` all over the place".
+		copy((*[unsafe.Sizeof(unix.Dirent{})]byte)(unsafe.Pointer(&sde))[:], workBuffer)
+		workBuffer = workBuffer[sde.Reclen:] // advance buffer for next iteration through loop
+
+		if sde.Ino == 0 {
+			continue // inode set to 0 indicates an entry that was marked as deleted
+		}
+
+		nameSlice := nameFromDirent(&sde)
+		nameLength := len(nameSlice)
+
+		if nameLength == 0 || (nameSlice[0] == '.' && (nameLength == 1 || (nameLength == 2 && nameSlice[1] == '.'))) {
+			continue
+		}
+
+		childName := string(nameSlice)
+		mt, err := fs.modeTypeFromDirent(fd, &sde, name, childName)
+		if err != nil {
+			return nil, convertErrorType(err)
+		}
+		entries = append(entries, &dirent{name: childName, path: name, modeType: mt, dirfd: fd, fs: fs})
+	}
+}
+
+// dirent stores the name and file system mode type of discovered file system
+// entries.
+type dirent struct {
+	name     string
+	path     string
+	modeType FileMode
+
+	dirfd int
+	fs    *UnixFS
+}
+
+func (de dirent) Name() string {
+	return de.name
+}
+
+func (de dirent) IsDir() bool {
+	return de.modeType&ModeDir != 0
+}
+
+func (de dirent) Type() FileMode {
+	return de.modeType
+}
+
+func (de dirent) Info() (FileInfo, error) {
+	if de.fs == nil {
+		return nil, nil
+	}
+	return de.fs.Lstatat(de.dirfd, de.name)
+}
+
+func (de dirent) Open() (File, error) {
+	if de.fs == nil {
+		return nil, nil
+	}
+	return de.fs.OpenFileat(de.dirfd, de.name, O_RDONLY, 0)
+}
+
+// reset releases memory held by entry err and name, and resets mode type to 0.
+func (de *dirent) reset() {
+	de.name = ""
+	de.path = ""
+	de.modeType = 0
+}

parser/helpers.go

@@ -2,8 +2,6 @@ package parser
 
 import (
 	"bytes"
-	"io"
-	"os"
 	"regexp"
 	"strconv"
 	"strings"
@@ -29,24 +27,14 @@ var configMatchRegex = regexp.MustCompile(`{{\s?config\.([\w.-]+)\s?}}`)
 // matching:
 //
 // <Root>
+//
 //	<Property value="testing"/>
+//
 // </Root>
 //
 // noinspection RegExpRedundantEscape
 var xmlValueMatchRegex = regexp.MustCompile(`^\[([\w]+)='(.*)'\]$`)
 
-// Gets the []byte representation of a configuration file to be passed through to other
-// handler functions. If the file does not currently exist, it will be created.
-func readFileBytes(path string) ([]byte, error) {
-	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o644)
-	if err != nil {
-		return nil, err
-	}
-	defer file.Close()
-
-	return io.ReadAll(file)
-}
-
 // Gets the value of a key based on the value type defined.
 func (cfr *ConfigurationFileReplacement) getKeyValue(value string) interface{} {
 	if cfr.ReplaceWith.Type() == jsonparser.Boolean {

parser/parser.go

@@ -2,8 +2,8 @@ package parser
 
 import (
 	"bufio"
-	"os"
+	"bytes"
-	"path/filepath"
+	"io"
 	"strconv"
 	"strings"
 
@@ -18,6 +18,7 @@ import (
 	"gopkg.in/yaml.v3"
 
 	"github.com/pterodactyl/wings/config"
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 // The file parsing options that are available for a server configuration file.
@@ -74,6 +75,26 @@ func (cv *ReplaceValue) String() string {
 	}
 }
 
+func (cv *ReplaceValue) Bytes() []byte {
+	switch cv.Type() {
+	case jsonparser.String:
+		var stackbuf [64]byte
+		bU, err := jsonparser.Unescape(cv.value, stackbuf[:])
+		if err != nil {
+			panic(errors.Wrap(err, "parser: could not parse value"))
+		}
+		return bU
+	case jsonparser.Null:
+		return []byte("<nil>")
+	case jsonparser.Boolean:
+		return cv.value
+	case jsonparser.Number:
+		return cv.value
+	default:
+		return []byte("<invalid>")
+	}
+}
+
 type ConfigurationParser string
 
 func (cp ConfigurationParser) String() string {
@@ -167,11 +188,12 @@ func (cfr *ConfigurationFileReplacement) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
-// Parses a given configuration file and updates all of the values within as defined
+// Parse parses a given configuration file and updates all the values within
-// in the API response from the Panel.
+// as defined in the API response from the Panel.
-func (f *ConfigurationFile) Parse(path string, internal bool) error {
+func (f *ConfigurationFile) Parse(file ufs.File) error {
-	log.WithField("path", path).WithField("parser", f.Parser.String()).Debug("parsing server configuration file")
+	//log.WithField("path", path).WithField("parser", f.Parser.String()).Debug("parsing server configuration file")
 
+	// What the fuck is going on here?
 	if mb, err := json.Marshal(config.Get()); err != nil {
 		return err
 	} else {
@@ -182,56 +204,24 @@ func (f *ConfigurationFile) Parse(path string, internal bool) error {
 
 	switch f.Parser {
 	case Properties:
-		err = f.parsePropertiesFile(path)
+		err = f.parsePropertiesFile(file)
-		break
 	case File:
-		err = f.parseTextFile(path)
+		err = f.parseTextFile(file)
-		break
 	case Yaml, "yml":
-		err = f.parseYamlFile(path)
+		err = f.parseYamlFile(file)
-		break
 	case Json:
-		err = f.parseJsonFile(path)
+		err = f.parseJsonFile(file)
-		break
 	case Ini:
-		err = f.parseIniFile(path)
+		err = f.parseIniFile(file)
-		break
 	case Xml:
-		err = f.parseXmlFile(path)
+		err = f.parseXmlFile(file)
-		break
 	}
-
-	if errors.Is(err, os.ErrNotExist) {
-		// File doesn't exist, we tried creating it, and same error is returned? Pretty
-		// sure this pathway is impossible, but if not, abort here.
-		if internal {
-			return nil
-		}
-
-		b := strings.TrimSuffix(path, filepath.Base(path))
-		if err := os.MkdirAll(b, 0o755); err != nil {
-			return errors.WithMessage(err, "failed to create base directory for missing configuration file")
-		} else {
-			if _, err := os.Create(path); err != nil {
-				return errors.WithMessage(err, "failed to create missing configuration file")
-			}
-		}
-
-		return f.Parse(path, true)
-	}
-
 	return err
 }
 
 // Parses an xml file.
-func (f *ConfigurationFile) parseXmlFile(path string) error {
+func (f *ConfigurationFile) parseXmlFile(file ufs.File) error {
 	doc := etree.NewDocument()
-	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o644)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-
 	if _, err := doc.ReadFrom(file); err != nil {
 		return err
 	}
@@ -291,41 +281,27 @@ func (f *ConfigurationFile) parseXmlFile(path string) error {
 		}
 	}
 
-	// If you don't truncate the file you'll end up duplicating the data in there (or just appending
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
-	// to the end of the file. We don't want to do that.
+		return err
+	}
 	if err := file.Truncate(0); err != nil {
 		return err
 	}
 
-	// Move the cursor to the start of the file to avoid weird spacing issues.
-	file.Seek(0, 0)
-
 	// Ensure the XML is indented properly.
 	doc.Indent(2)
 
-	// Truncate the file before attempting to write the changes.
+	// Write the XML to the file.
-	if err := os.Truncate(path, 0); err != nil {
+	if _, err := doc.WriteTo(file); err != nil {
 		return err
 	}
-
+	return nil
-	// Write the XML to the file.
-	_, err = doc.WriteTo(file)
-
-	return err
 }
 
 // Parses an ini file.
-func (f *ConfigurationFile) parseIniFile(path string) error {
+func (f *ConfigurationFile) parseIniFile(file ufs.File) error {
-	// Ini package can't handle a non-existent file, so handle that automatically here
+	// Wrap the file in a NopCloser so the ini package doesn't close the file.
-	// by creating it if not exists. Then, immediately close the file since we will use
+	cfg, err := ini.Load(io.NopCloser(file))
-	// other methods to write the new contents.
-	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o644)
-	if err != nil {
-		return err
-	}
-	file.Close()
-
-	cfg, err := ini.Load(path)
 	if err != nil {
 		return err
 	}
@@ -388,14 +364,24 @@ func (f *ConfigurationFile) parseIniFile(path string) error {
 		}
 	}
 
-	return cfg.SaveTo(path)
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	if err := file.Truncate(0); err != nil {
+		return err
+	}
+
+	if _, err := cfg.WriteTo(file); err != nil {
+		return err
+	}
+	return nil
 }
 
 // Parses a json file updating any matching key/value pairs. If a match is not found, the
 // value is set regardless in the file. See the commentary in parseYamlFile for more details
 // about what is happening during this process.
-func (f *ConfigurationFile) parseJsonFile(path string) error {
+func (f *ConfigurationFile) parseJsonFile(file ufs.File) error {
-	b, err := readFileBytes(path)
+	b, err := io.ReadAll(file)
 	if err != nil {
 		return err
 	}
@@ -405,14 +391,24 @@ func (f *ConfigurationFile) parseJsonFile(path string) error {
 		return err
 	}
 
-	output := []byte(data.StringIndent("", "    "))
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
-	return os.WriteFile(path, output, 0o644)
+		return err
+	}
+	if err := file.Truncate(0); err != nil {
+		return err
+	}
+
+	// Write the data to the file.
+	if _, err := io.Copy(file, bytes.NewReader(data.BytesIndent("", "    "))); err != nil {
+		return errors.Wrap(err, "parser: failed to write properties file to disk")
+	}
+	return nil
 }
 
 // Parses a yaml file and updates any matching key/value pairs before persisting
 // it back to the disk.
-func (f *ConfigurationFile) parseYamlFile(path string) error {
+func (f *ConfigurationFile) parseYamlFile(file ufs.File) error {
-	b, err := readFileBytes(path)
+	b, err := io.ReadAll(file)
 	if err != nil {
 		return err
 	}
@@ -443,35 +439,56 @@ func (f *ConfigurationFile) parseYamlFile(path string) error {
 		return err
 	}
 
-	return os.WriteFile(path, marshaled, 0o644)
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	if err := file.Truncate(0); err != nil {
+		return err
+	}
+
+	// Write the data to the file.
+	if _, err := io.Copy(file, bytes.NewReader(marshaled)); err != nil {
+		return errors.Wrap(err, "parser: failed to write properties file to disk")
+	}
+	return nil
 }
 
 // Parses a text file using basic find and replace. This is a highly inefficient method of
 // scanning a file and performing a replacement. You should attempt to use anything other
 // than this function where possible.
-func (f *ConfigurationFile) parseTextFile(path string) error {
+func (f *ConfigurationFile) parseTextFile(file ufs.File) error {
-	input, err := os.ReadFile(path)
+	b := bytes.NewBuffer(nil)
-	if err != nil {
+	s := bufio.NewScanner(file)
-		return err
+	var replaced bool
-	}
+	for s.Scan() {
-
+		line := s.Bytes()
-	lines := strings.Split(string(input), "\n")
+		replaced = false
-	for i, line := range lines {
 		for _, replace := range f.Replace {
 			// If this line doesn't match what we expect for the replacement, move on to the next
 			// line. Otherwise, update the line to have the replacement value.
-			if !strings.HasPrefix(line, replace.Match) {
+			if !bytes.HasPrefix(line, []byte(replace.Match)) {
 				continue
 			}
-
+			b.Write(replace.ReplaceWith.Bytes())
-			lines[i] = replace.ReplaceWith.String()
+			replaced = true
 		}
+		if !replaced {
+			b.Write(line)
+		}
+		b.WriteByte('\n')
 	}
 
-	if err := os.WriteFile(path, []byte(strings.Join(lines, "\n")), 0o644); err != nil {
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	if err := file.Truncate(0); err != nil {
 		return err
 	}
 
+	// Write the data to the file.
+	if _, err := io.Copy(file, b); err != nil {
+		return errors.Wrap(err, "parser: failed to write properties file to disk")
+	}
 	return nil
 }
 
@@ -501,31 +518,29 @@ func (f *ConfigurationFile) parseTextFile(path string) error {
 //
 // @see https://github.com/pterodactyl/panel/issues/2308 (original)
 // @see https://github.com/pterodactyl/panel/issues/3009 ("bug" introduced as result)
-func (f *ConfigurationFile) parsePropertiesFile(path string) error {
+func (f *ConfigurationFile) parsePropertiesFile(file ufs.File) error {
-	var s strings.Builder
+	b, err := io.ReadAll(file)
-	// Open the file and attempt to load any comments that currenty exist at the start
+	if err != nil {
-	// of the file. This is kind of a hack, but should work for a majority of users for
+		return err
-	// the time being.
+	}
-	if fd, err := os.Open(path); err != nil {
+
-		return errors.Wrap(err, "parser: could not open file for reading")
+	s := bytes.NewBuffer(nil)
-	} else {
+	scanner := bufio.NewScanner(bytes.NewReader(b))
-		scanner := bufio.NewScanner(fd)
 	// Scan until we hit a line that is not a comment that actually has content
 	// on it. Keep appending the comments until that time.
 	for scanner.Scan() {
-			text := scanner.Text()
+		text := scanner.Bytes()
 		if len(text) > 0 && text[0] != '#' {
 			break
 		}
-			s.WriteString(text + "\n")
+		s.Write(text)
+		s.WriteByte('\n')
 	}
-		_ = fd.Close()
 	if err := scanner.Err(); err != nil {
 		return errors.WithStackIf(err)
 	}
-	}
 
-	p, err := properties.LoadFile(path, properties.UTF8)
+	p, err := properties.Load(b, properties.UTF8)
 	if err != nil {
 		return errors.Wrap(err, "parser: could not load properties file for configuration update")
 	}
@@ -563,17 +578,16 @@ func (f *ConfigurationFile) parsePropertiesFile(path string) error {
 		s.WriteString(key + "=" + strings.Trim(strconv.QuoteToASCII(value), "\"") + "\n")
 	}
 
-	// Open the file for writing.
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
-	w, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
+		return err
-	if err != nil {
+	}
+	if err := file.Truncate(0); err != nil {
 		return err
 	}
-	defer w.Close()
 
 	// Write the data to the file.
-	if _, err := w.Write([]byte(s.String())); err != nil {
+	if _, err := io.Copy(file, s); err != nil {
 		return errors.Wrap(err, "parser: failed to write properties file to disk")
 	}
-
 	return nil
 }

router/downloader/downloader.go

@@ -167,13 +167,8 @@ func (dl *Download) Execute() error {
 		return errors.New("downloader: got bad response status from endpoint: " + res.Status)
 	}
 
-	// If there is a Content-Length header on this request go ahead and check that we can
+	if res.ContentLength < 1 {
-	// even write the whole file before beginning this process. If there is no header present
+		return errors.New("downloader: request is missing ContentLength")
-	// we'll just have to give it a spin and see how it goes.
-	if res.ContentLength > 0 {
-		if err := dl.server.Filesystem().HasSpaceFor(res.ContentLength); err != nil {
-			return errors.WrapIf(err, "downloader: failed to write file: not enough space")
-		}
 	}
 
 	if dl.req.UseHeader {
@@ -200,8 +195,10 @@ func (dl *Download) Execute() error {
 	p := dl.Path()
 	dl.server.Log().WithField("path", p).Debug("writing remote file to disk")
 
+	// Write the file while tracking the progress, Write will check that the
+	// size of the file won't exceed the disk limit.
 	r := io.TeeReader(res.Body, dl.counter(res.ContentLength))
-	if err := dl.server.Filesystem().Writefile(p, r); err != nil {
+	if err := dl.server.Filesystem().Write(p, r, res.ContentLength, 0o644); err != nil {
 		return errors.WrapIf(err, "downloader: failed to write file to server directory")
 	}
 	return nil

router/router_download.go

@@ -45,6 +45,8 @@ func getDownloadBackup(c *gin.Context) {
 		return
 	}
 
+	// The use of `os` here is safe as backups are not stored within server
+	// accessible directories.
 	f, err := os.Open(b.Path())
 	if err != nil {
 		middleware.CaptureAndAbort(c, err)
@@ -76,26 +78,18 @@ func getDownloadFile(c *gin.Context) {
 		return
 	}
 
-	p, _ := s.Filesystem().SafePath(token.FilePath)
+	f, st, err := s.Filesystem().File(token.FilePath)
-	st, err := os.Stat(p)
-	// If there is an error or we're somehow trying to download a directory, just
-	// respond with the appropriate error.
-	if err != nil {
-		middleware.CaptureAndAbort(c, err)
-		return
-	} else if st.IsDir() {
-		c.AbortWithStatusJSON(http.StatusNotFound, gin.H{
-			"error": "The requested resource was not found on this server.",
-		})
-		return
-	}
-
-	f, err := os.Open(p)
 	if err != nil {
 		middleware.CaptureAndAbort(c, err)
 		return
 	}
 	defer f.Close()
+	if st.IsDir() {
+		c.AbortWithStatusJSON(http.StatusNotFound, gin.H{
+			"error": "The requested resource was not found on this server.",
+		})
+		return
+	}
 
 	c.Header("Content-Length", strconv.Itoa(int(st.Size())))
 	c.Header("Content-Disposition", "attachment; filename="+strconv.Quote(st.Name()))

router/router_server.go

@@ -228,6 +228,7 @@ func deleteServer(c *gin.Context) {
 	// In addition, servers with large amounts of files can take some time to finish deleting,
 	// so we don't want to block the HTTP call while waiting on this.
 	go func(p string) {
+		_ = s.Filesystem().UnixFS().Close()
 		if err := os.RemoveAll(p); err != nil {
 			log.WithFields(log.Fields{"path": p, "error": err}).Warn("failed to remove server files during deletion process")
 		}

router/router_server_files.go

@@ -30,7 +30,7 @@ import (
 // getServerFileContents returns the contents of a file on the server.
 func getServerFileContents(c *gin.Context) {
 	s := middleware.ExtractServer(c)
-	p := "/" + strings.TrimLeft(c.Query("file"), "/")
+	p := strings.TrimLeft(c.Query("file"), "/")
 	f, st, err := s.Filesystem().File(p)
 	if err != nil {
 		middleware.CaptureAndAbort(c, err)
@@ -129,7 +129,6 @@ func putServerRenameFiles(c *gin.Context) {
 				}
 				if err := fs.Rename(pf, pt); err != nil {
 					// Return nil if the error is an is not exists.
-					// NOTE: os.IsNotExist() does not work if the error is wrapped.
 					if errors.Is(err, os.ErrNotExist) {
 						s.Log().WithField("error", err).
 							WithField("from_path", pf).
@@ -239,7 +238,15 @@ func postServerWriteFile(c *gin.Context) {
 		middleware.CaptureAndAbort(c, err)
 		return
 	}
-	if err := s.Filesystem().Writefile(f, c.Request.Body); err != nil {
+
+	if c.Request.ContentLength < 1 {
+		c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
+			"error": "Missing Content-Length",
+		})
+		return
+	}
+
+	if err := s.Filesystem().Write(f, c.Request.Body, c.Request.ContentLength, 0o644); err != nil {
 		if filesystem.IsErrorCode(err, filesystem.ErrCodeIsDirectory) {
 			c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
 				"error": "Cannot write file, name conflicts with an existing directory by the same name.",
@@ -589,15 +596,9 @@ func postServerUploadFiles(c *gin.Context) {
 	}
 
 	for _, header := range headers {
-		p, err := s.Filesystem().SafePath(filepath.Join(directory, header.Filename))
-		if err != nil {
-			middleware.CaptureAndAbort(c, err)
-			return
-		}
-
 		// We run this in a different method so I can use defer without any of
 		// the consequences caused by calling it in a loop.
-		if err := handleFileUpload(p, s, header); err != nil {
+		if err := handleFileUpload(filepath.Join(directory, header.Filename), s, header); err != nil {
 			middleware.CaptureAndAbort(c, err)
 			return
 		} else {
@@ -619,7 +620,8 @@ func handleFileUpload(p string, s *server.Server, header *multipart.FileHeader)
 	if err := s.Filesystem().IsIgnored(p); err != nil {
 		return err
 	}
-	if err := s.Filesystem().Writefile(p, file); err != nil {
+
+	if err := s.Filesystem().Write(p, file, header.Size, 0o644); err != nil {
 		return err
 	}
 	return nil

router/router_transfer.go

@@ -106,6 +106,7 @@ func postTransfers(c *gin.Context) {
 			if !successful && err != nil {
 				// Delete all extracted files.
 				go func(trnsfr *transfer.Transfer) {
+					_ = trnsfr.Server.Filesystem().UnixFS().Close()
 					if err := os.RemoveAll(trnsfr.Server.Filesystem().Path()); err != nil && !os.IsNotExist(err) {
 						trnsfr.Log().WithError(err).Warn("failed to delete local server files")
 					}

server/backup.go

@@ -67,7 +67,7 @@ func (s *Server) Backup(b backup.BackupInterface) error {
 		}
 	}
 
-	ad, err := b.Generate(s.Context(), s.Filesystem().Path(), ignored)
+	ad, err := b.Generate(s.Context(), s.Filesystem(), ignored)
 	if err != nil {
 		if err := s.notifyPanelOfBackup(b.Identifier(), &backup.ArchiveDetails{}, false); err != nil {
 			s.Log().WithFields(log.Fields{
@@ -154,17 +154,14 @@ func (s *Server) RestoreBackup(b backup.BackupInterface, reader io.ReadCloser) (
 	err = b.Restore(s.Context(), reader, func(file string, info fs.FileInfo, r io.ReadCloser) error {
 		defer r.Close()
 		s.Events().Publish(DaemonMessageEvent, "(restoring): "+file)
-
+		// TODO: since this will be called a lot, it may be worth adding an optimized
-		if err := s.Filesystem().Writefile(file, r); err != nil {
+		// Write with Chtimes method to the UnixFS that is able to re-use the
+		// same dirfd and file name.
+		if err := s.Filesystem().Write(file, r, info.Size(), info.Mode()); err != nil {
 			return err
 		}
-		if err := s.Filesystem().Chmod(file, info.Mode()); err != nil {
-			return err
-		}
-
 		atime := info.ModTime()
-		mtime := atime
+		return s.Filesystem().Chtimes(file, atime, atime)
-		return s.Filesystem().Chtimes(file, atime, mtime)
 	})
 
 	return errors.WithStackIf(err)

server/backup/backup.go

@@ -16,6 +16,7 @@ import (
 
 	"github.com/pterodactyl/wings/config"
 	"github.com/pterodactyl/wings/remote"
+	"github.com/pterodactyl/wings/server/filesystem"
 )
 
 var format = archiver.CompressedArchive{
@@ -46,7 +47,7 @@ type BackupInterface interface {
 	WithLogContext(map[string]interface{})
 	// Generate creates a backup in whatever the configured source for the
 	// specific implementation is.
-	Generate(context.Context, string, string) (*ArchiveDetails, error)
+	Generate(context.Context, *filesystem.Filesystem, string) (*ArchiveDetails, error)
 	// Ignored returns the ignored files for this backup instance.
 	Ignored() string
 	// Checksum returns a SHA1 checksum for the generated backup.

server/backup/backup_local.go

@@ -59,9 +59,9 @@ func (b *LocalBackup) WithLogContext(c map[string]interface{}) {
 
 // Generate generates a backup of the selected files and pushes it to the
 // defined location for this instance.
-func (b *LocalBackup) Generate(ctx context.Context, basePath, ignore string) (*ArchiveDetails, error) {
+func (b *LocalBackup) Generate(ctx context.Context, fsys *filesystem.Filesystem, ignore string) (*ArchiveDetails, error) {
 	a := &filesystem.Archive{
-		BasePath: basePath,
+		Filesystem: fsys,
 		Ignore:     ignore,
 	}
 

server/backup/backup_s3.go

@@ -48,11 +48,11 @@ func (s *S3Backup) WithLogContext(c map[string]interface{}) {
 
 // Generate creates a new backup on the disk, moves it into the S3 bucket via
 // the provided presigned URL, and then deletes the backup from the disk.
-func (s *S3Backup) Generate(ctx context.Context, basePath, ignore string) (*ArchiveDetails, error) {
+func (s *S3Backup) Generate(ctx context.Context, fsys *filesystem.Filesystem, ignore string) (*ArchiveDetails, error) {
 	defer s.Remove()
 
 	a := &filesystem.Archive{
-		BasePath: basePath,
+		Filesystem: fsys,
 		Ignore:     ignore,
 	}
 

server/config_parser.go

@@ -4,9 +4,11 @@ import (
 	"runtime"
 
 	"github.com/gammazero/workerpool"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
-// UpdateConfigurationFiles updates all of the defined configuration files for
+// UpdateConfigurationFiles updates all the defined configuration files for
 // a server automatically to ensure that they always use the specified values.
 func (s *Server) UpdateConfigurationFiles() {
 	pool := workerpool.New(runtime.NumCPU())
@@ -18,18 +20,18 @@ func (s *Server) UpdateConfigurationFiles() {
 		f := cf
 
 		pool.Submit(func() {
-			p, err := s.Filesystem().SafePath(f.FileName)
+			file, err := s.Filesystem().UnixFS().Touch(f.FileName, ufs.O_RDWR|ufs.O_CREATE, 0o644)
 			if err != nil {
-				s.Log().WithField("error", err).Error("failed to generate safe path for configuration file")
+				s.Log().WithField("file_name", f.FileName).WithField("error", err).Error("failed to open file for configuration")
-
 				return
 			}
+			defer file.Close()
 
-			if err := f.Parse(p, false); err != nil {
+			if err := f.Parse(file); err != nil {
 				s.Log().WithField("error", err).Error("failed to parse and update server configuration file")
 			}
 
-			s.Log().WithField("path", f.FileName).Debug("finished processing server configuration file")
+			s.Log().WithField("file_name", f.FileName).Debug("finished processing server configuration file")
 		})
 	}
 

server/filesystem/archive.go

@@ -3,7 +3,6 @@ package filesystem
 import (
 	"archive/tar"
 	"context"
-	"fmt"
 	"io"
 	"io/fs"
 	"os"
@@ -14,12 +13,12 @@ import (
 	"emperror.dev/errors"
 	"github.com/apex/log"
 	"github.com/juju/ratelimit"
-	"github.com/karrick/godirwalk"
 	"github.com/klauspost/pgzip"
 	ignore "github.com/sabhiram/go-gitignore"
 
 	"github.com/pterodactyl/wings/config"
 	"github.com/pterodactyl/wings/internal/progress"
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 const memory = 4 * 1024
@@ -57,14 +56,16 @@ func (p *TarProgress) Write(v []byte) (int, error) {
 }
 
 type Archive struct {
-	// BasePath is the absolute path to create the archive from where Files and Ignore are
+	// Filesystem to create the archive with.
-	// relative to.
+	Filesystem *Filesystem
-	BasePath string
 
 	// Ignore is a gitignore string (most likely read from a file) of files to ignore
 	// from the archive.
 	Ignore string
 
+	// BaseDirectory .
+	BaseDirectory string
+
 	// Files specifies the files to archive, this takes priority over the Ignore option, if
 	// unspecified, all files in the BasePath will be archived unless Ignore is set.
 	//
@@ -73,11 +74,18 @@ type Archive struct {
 
 	// Progress wraps the writer of the archive to pass through the progress tracker.
 	Progress *progress.Progress
+
+	w *TarProgress
 }
 
 // Create creates an archive at dst with all the files defined in the
 // included Files array.
+//
+// THIS IS UNSAFE TO USE IF `dst` IS PROVIDED BY A USER! ONLY USE THIS WITH
+// CONTROLLED PATHS!
 func (a *Archive) Create(ctx context.Context, dst string) error {
+	// Using os.OpenFile here is expected, as long as `dst` is not a user
+	// provided path.
 	f, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
 	if err != nil {
 		return err
@@ -98,14 +106,19 @@ func (a *Archive) Create(ctx context.Context, dst string) error {
 	return a.Stream(ctx, writer)
 }
 
-// Stream .
+type walkFunc func(dirfd int, name, relative string, d ufs.DirEntry) error
+
+// Stream streams the creation of the archive to the given writer.
 func (a *Archive) Stream(ctx context.Context, w io.Writer) error {
-	for _, f := range a.Files {
+	if a.Filesystem == nil {
-		if strings.HasPrefix(f, a.BasePath) {
+		return errors.New("filesystem: archive.Filesystem is unset")
-			continue
 	}
 
-		return fmt.Errorf("archive: all entries in Files must be absolute and within BasePath: %s\n", f)
+	for i, f := range a.Files {
+		if !strings.HasPrefix(f, a.Filesystem.Path()) {
+			continue
+		}
+		a.Files[i] = strings.TrimPrefix(strings.TrimPrefix(f, a.Filesystem.Path()), "/")
 	}
 
 	// Choose which compression level to use based on the compression_level configuration option
@@ -130,107 +143,100 @@ func (a *Archive) Stream(ctx context.Context, w io.Writer) error {
 	tw := tar.NewWriter(gw)
 	defer tw.Close()
 
-	pw := NewTarProgress(tw, a.Progress)
+	a.w = NewTarProgress(tw, a.Progress)
 
-	// Configure godirwalk.
+	fs := a.Filesystem.unixFS
-	options := &godirwalk.Options{
-		FollowSymbolicLinks: false,
-		Unsorted:            true,
-	}
 
 	// If we're specifically looking for only certain files, or have requested
 	// that certain files be ignored we'll update the callback function to reflect
 	// that request.
-	var callback godirwalk.WalkFunc
+	var callback walkFunc
 	if len(a.Files) == 0 && len(a.Ignore) > 0 {
 		i := ignore.CompileIgnoreLines(strings.Split(a.Ignore, "\n")...)
-
+		callback = a.callback(func(_ int, _, relative string, _ ufs.DirEntry) error {
-		callback = a.callback(pw, func(_ string, rp string) error {
+			if i.MatchesPath(relative) {
-			if i.MatchesPath(rp) {
+				return ufs.SkipDir
-				return godirwalk.SkipThis
 			}
-
 			return nil
 		})
 	} else if len(a.Files) > 0 {
-		callback = a.withFilesCallback(pw)
+		callback = a.withFilesCallback()
 	} else {
-		callback = a.callback(pw)
+		callback = a.callback()
 	}
 
-	// Set the callback function, wrapped with support for context cancellation.
+	dirfd, name, closeFd, err := fs.SafePath(a.BaseDirectory)
-	options.Callback = func(path string, de *godirwalk.Dirent) error {
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+	return fs.WalkDirat(dirfd, name, func(dirfd int, name, relative string, d ufs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
 		default:
-			return callback(path, de)
+			return callback(dirfd, name, relative, d)
 		}
-	}
+	})
-
-	// Recursively walk the path we are archiving.
-	return godirwalk.Walk(a.BasePath, options)
 }
 
 // Callback function used to determine if a given file should be included in the archive
 // being generated.
-func (a *Archive) callback(tw *TarProgress, opts ...func(path string, relative string) error) func(path string, de *godirwalk.Dirent) error {
+func (a *Archive) callback(opts ...walkFunc) walkFunc {
-	return func(path string, de *godirwalk.Dirent) error {
+	return func(dirfd int, name, relative string, d ufs.DirEntry) error {
 		// Skip directories because we are walking them recursively.
-		if de.IsDir() {
+		if d.IsDir() {
 			return nil
 		}
 
-		relative := filepath.ToSlash(strings.TrimPrefix(path, a.BasePath+string(filepath.Separator)))
-
 		// Call the additional options passed to this callback function. If any of them return
 		// a non-nil error we will exit immediately.
 		for _, opt := range opts {
-			if err := opt(path, relative); err != nil {
+			if err := opt(dirfd, name, relative, d); err != nil {
 				return err
 			}
 		}
 
 		// Add the file to the archive, if it is nested in a directory,
 		// the directory will be automatically "created" in the archive.
-		return a.addToArchive(path, relative, tw)
+		return a.addToArchive(dirfd, name, relative, d)
 	}
 }
 
 // Pushes only files defined in the Files key to the final archive.
-func (a *Archive) withFilesCallback(tw *TarProgress) func(path string, de *godirwalk.Dirent) error {
+func (a *Archive) withFilesCallback() walkFunc {
-	return a.callback(tw, func(p string, rp string) error {
+	return a.callback(func(_ int, _, relative string, _ ufs.DirEntry) error {
 		for _, f := range a.Files {
 			// Allow exact file matches, otherwise check if file is within a parent directory.
 			//
 			// The slashes are added in the prefix checks to prevent partial name matches from being
 			// included in the archive.
-			if f != p && !strings.HasPrefix(strings.TrimSuffix(p, "/")+"/", strings.TrimSuffix(f, "/")+"/") {
+			if f != relative && !strings.HasPrefix(strings.TrimSuffix(relative, "/")+"/", strings.TrimSuffix(f, "/")+"/") {
 				continue
 			}
 
 			// Once we have a match return a nil value here so that the loop stops and the
 			// call to this function will correctly include the file in the archive. If there
 			// are no matches we'll never make it to this line, and the final error returned
-			// will be the godirwalk.SkipThis error.
+			// will be the ufs.SkipDir error.
 			return nil
 		}
 
-		return godirwalk.SkipThis
+		return ufs.SkipDir
 	})
 }
 
 // Adds a given file path to the final archive being created.
-func (a *Archive) addToArchive(p string, rp string, w *TarProgress) error {
+func (a *Archive) addToArchive(dirfd int, name, relative string, entry ufs.DirEntry) error {
-	// Lstat the file, this will give us the same information as Stat except that it will not
+	s, err := entry.Info()
-	// follow a symlink to its target automatically. This is important to avoid including
-	// files that exist outside the server root unintentionally in the backup.
-	s, err := os.Lstat(p)
 	if err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, ufs.ErrNotExist) {
 			return nil
 		}
-		return errors.WrapIff(err, "failed executing os.Lstat on '%s'", rp)
+		return errors.WrapIff(err, "failed executing os.Lstat on '%s'", name)
 	}
 
 	// Skip socket files as they are unsupported by archive/tar.
@@ -250,7 +256,7 @@ func (a *Archive) addToArchive(p string, rp string, w *TarProgress) error {
 		if err != nil {
 			// Ignore the not exist errors specifically, since there is nothing important about that.
 			if !os.IsNotExist(err) {
-				log.WithField("path", rp).WithField("readlink_err", err.Error()).Warn("failed reading symlink for target path; skipping...")
+				log.WithField("name", name).WithField("readlink_err", err.Error()).Warn("failed reading symlink for target path; skipping...")
 			}
 			return nil
 		}
@@ -259,17 +265,17 @@ func (a *Archive) addToArchive(p string, rp string, w *TarProgress) error {
 	// Get the tar FileInfoHeader in order to add the file to the archive.
 	header, err := tar.FileInfoHeader(s, filepath.ToSlash(target))
 	if err != nil {
-		return errors.WrapIff(err, "failed to get tar#FileInfoHeader for '%s'", rp)
+		return errors.WrapIff(err, "failed to get tar#FileInfoHeader for '%s'", name)
 	}
 
 	// Fix the header name if the file is not a symlink.
 	if s.Mode()&fs.ModeSymlink == 0 {
-		header.Name = rp
+		header.Name = relative
 	}
 
 	// Write the tar FileInfoHeader to the archive.
-	if err := w.WriteHeader(header); err != nil {
+	if err := a.w.WriteHeader(header); err != nil {
-		return errors.WrapIff(err, "failed to write tar#FileInfoHeader for '%s'", rp)
+		return errors.WrapIff(err, "failed to write tar#FileInfoHeader for '%s'", name)
 	}
 
 	// If the size of the file is less than 1 (most likely for symlinks), skip writing the file.
@@ -291,7 +297,7 @@ func (a *Archive) addToArchive(p string, rp string, w *TarProgress) error {
 	}
 
 	// Open the file.
-	f, err := os.Open(p)
+	f, err := a.Filesystem.unixFS.OpenFileat(dirfd, name, ufs.O_RDONLY, 0)
 	if err != nil {
 		if os.IsNotExist(err) {
 			return nil
@@ -301,9 +307,8 @@ func (a *Archive) addToArchive(p string, rp string, w *TarProgress) error {
 	defer f.Close()
 
 	// Copy the file's contents to the archive using our buffer.
-	if _, err := io.CopyBuffer(w, io.LimitReader(f, header.Size), buf); err != nil {
+	if _, err := io.CopyBuffer(a.w, io.LimitReader(f, header.Size), buf); err != nil {
 		return errors.WrapIff(err, "failed to copy '%s' to archive", header.Name)
 	}
-
 	return nil
 }

server/filesystem/archive_test.go

@@ -20,43 +20,34 @@ func TestArchive_Stream(t *testing.T) {
 	g.Describe("Archive", func() {
 		g.AfterEach(func() {
 			// Reset the filesystem after each run.
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
-		})
-
-		g.It("throws an error when passed invalid file paths", func() {
-			a := &Archive{
-				BasePath: fs.Path(),
-				Files: []string{
-					// To use the archiver properly, this needs to be filepath.Join(BasePath, "yeet")
-					// However, this test tests that we actually validate that behavior.
-					"yeet",
-				},
-			}
-
-			g.Assert(a.Create(context.Background(), "")).IsNotNil()
 		})
 
 		g.It("creates archive with intended files", func() {
 			g.Assert(fs.CreateDirectory("test", "/")).IsNil()
 			g.Assert(fs.CreateDirectory("test2", "/")).IsNil()
 
-			err := fs.Writefile("test/file.txt", strings.NewReader("hello, world!\n"))
+			r := strings.NewReader("hello, world!\n")
+			err := fs.Write("test/file.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
-			err = fs.Writefile("test2/file.txt", strings.NewReader("hello, world!\n"))
+			r = strings.NewReader("hello, world!\n")
+			err = fs.Write("test2/file.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
-			err = fs.Writefile("test_file.txt", strings.NewReader("hello, world!\n"))
+			r = strings.NewReader("hello, world!\n")
+			err = fs.Write("test_file.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
-			err = fs.Writefile("test_file.txt.old", strings.NewReader("hello, world!\n"))
+			r = strings.NewReader("hello, world!\n")
+			err = fs.Write("test_file.txt.old", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			a := &Archive{
-				BasePath: fs.Path(),
+				Filesystem: fs,
 				Files: []string{
-					filepath.Join(fs.Path(), "test"),
+					"test",
-					filepath.Join(fs.Path(), "test_file.txt"),
+					"test_file.txt",
 				},
 			}
 

server/filesystem/compress.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io"
 	iofs "io/fs"
-	"os"
 	"path"
 	"path/filepath"
 	"strings"
@@ -13,7 +12,10 @@ import (
 	"time"
 
 	"emperror.dev/errors"
+	"github.com/klauspost/compress/zip"
 	"github.com/mholt/archiver/v4"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 // CompressFiles compresses all the files matching the given paths in the
@@ -25,46 +27,69 @@ import (
 // All paths are relative to the dir that is passed in as the first argument,
 // and the compressed file will be placed at that location named
 // `archive-{date}.tar.gz`.
-func (fs *Filesystem) CompressFiles(dir string, paths []string) (os.FileInfo, error) {
+func (fs *Filesystem) CompressFiles(dir string, paths []string) (ufs.FileInfo, error) {
-	cleanedRootDir, err := fs.SafePath(dir)
+	a := &Archive{Filesystem: fs, BaseDirectory: dir, Files: paths}
-	if err != nil {
-		return nil, err
-	}
-
-	// Take all the paths passed in and merge them together with the root directory we've gotten.
-	for i, p := range paths {
-		paths[i] = filepath.Join(cleanedRootDir, p)
-	}
-
-	cleaned, err := fs.ParallelSafePath(paths)
-	if err != nil {
-		return nil, err
-	}
-
-	a := &Archive{BasePath: cleanedRootDir, Files: cleaned}
 	d := path.Join(
-		cleanedRootDir,
+		dir,
 		fmt.Sprintf("archive-%s.tar.gz", strings.ReplaceAll(time.Now().Format(time.RFC3339), ":", "")),
 	)
-
+	f, err := fs.unixFS.OpenFile(d, ufs.O_WRONLY|ufs.O_CREATE, 0o644)
-	if err := a.Create(context.Background(), d); err != nil {
-		return nil, err
-	}
-
-	f, err := os.Stat(d)
 	if err != nil {
-		_ = os.Remove(d)
+		return nil, err
+	}
+	defer f.Close()
+	cw := ufs.NewCountedWriter(f)
+	if err := a.Stream(context.Background(), cw); err != nil {
+		return nil, err
+	}
+	if !fs.unixFS.CanFit(cw.BytesWritten()) {
+		_ = fs.unixFS.Remove(d)
+		return nil, newFilesystemError(ErrCodeDiskSpace, nil)
+	}
+	fs.unixFS.Add(cw.BytesWritten())
+	return f.Stat()
+}
+
+func (fs *Filesystem) archiverFileSystem(ctx context.Context, p string) (iofs.FS, error) {
+	f, err := fs.unixFS.Open(p)
+	if err != nil {
+		return nil, err
+	}
+	// Do not use defer to close `f`, it will likely be used later.
+
+	format, _, err := archiver.Identify(filepath.Base(p), f)
+	if err != nil && !errors.Is(err, archiver.ErrNoMatch) {
+		_ = f.Close()
 		return nil, err
 	}
 
-	if err := fs.HasSpaceFor(f.Size()); err != nil {
+	// Reset the file reader.
-		_ = os.Remove(d)
+	if _, err := f.Seek(0, io.SeekStart); err != nil {
+		_ = f.Close()
 		return nil, err
 	}
 
-	fs.addDisk(f.Size())
+	info, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
 
-	return f, nil
+	if format != nil {
+		switch ff := format.(type) {
+		case archiver.Zip:
+			// zip.Reader is more performant than ArchiveFS, because zip.Reader caches content information
+			// and zip.Reader can open several content files concurrently because of io.ReaderAt requirement
+			// while ArchiveFS can't.
+			// zip.Reader doesn't suffer from issue #330 and #310 according to local test (but they should be fixed anyway)
+			return zip.NewReader(f, info.Size())
+		case archiver.Archival:
+			return archiver.ArchiveFS{Stream: io.NewSectionReader(f, 0, info.Size()), Format: ff, Context: ctx}, nil
+		}
+	}
+
+	_ = f.Close()
+	return nil, nil
 }
 
 // SpaceAvailableForDecompression looks through a given archive and determines
@@ -76,16 +101,7 @@ func (fs *Filesystem) SpaceAvailableForDecompression(ctx context.Context, dir st
 		return nil
 	}
 
-	source, err := fs.SafePath(filepath.Join(dir, file))
+	fsys, err := fs.archiverFileSystem(ctx, filepath.Join(dir, file))
-	if err != nil {
-		return err
-	}
-
-	// Get the cached size in a parallel process so that if it is not cached we are not
-	// waiting an unnecessary amount of time on this call.
-	dirSize, err := fs.DiskUsage(false)
-
-	fsys, err := archiver.FileSystem(ctx, source)
 	if err != nil {
 		if errors.Is(err, archiver.ErrNoMatch) {
 			return newFilesystemError(ErrCodeUnknownArchive, err)
@@ -93,7 +109,7 @@ func (fs *Filesystem) SpaceAvailableForDecompression(ctx context.Context, dir st
 		return err
 	}
 
-	var size int64
+	var size atomic.Int64
 	return iofs.WalkDir(fsys, ".", func(path string, d iofs.DirEntry, err error) error {
 		if err != nil {
 			return err
@@ -108,7 +124,7 @@ func (fs *Filesystem) SpaceAvailableForDecompression(ctx context.Context, dir st
 			if err != nil {
 				return err
 			}
-			if atomic.AddInt64(&size, info.Size())+dirSize > fs.MaxDisk() {
+			if !fs.unixFS.CanFit(size.Add(info.Size())) {
 				return newFilesystemError(ErrCodeDiskSpace, nil)
 			}
 			return nil
@@ -122,23 +138,7 @@ func (fs *Filesystem) SpaceAvailableForDecompression(ctx context.Context, dir st
 // zip-slip attack being attempted by validating that the final path is within
 // the server data directory.
 func (fs *Filesystem) DecompressFile(ctx context.Context, dir string, file string) error {
-	source, err := fs.SafePath(filepath.Join(dir, file))
+	f, err := fs.unixFS.Open(filepath.Join(dir, file))
-	if err != nil {
-		return err
-	}
-	return fs.DecompressFileUnsafe(ctx, dir, source)
-}
-
-// DecompressFileUnsafe will decompress any file on the local disk without checking
-// if it is owned by the server.  The file will be SAFELY decompressed and extracted
-// into the server's directory.
-func (fs *Filesystem) DecompressFileUnsafe(ctx context.Context, dir string, file string) error {
-	// Ensure that the archive actually exists on the system.
-	if _, err := os.Stat(file); err != nil {
-		return errors.WithStack(err)
-	}
-
-	f, err := os.Open(file)
 	if err != nil {
 		return err
 	}
@@ -169,7 +169,6 @@ func (fs *Filesystem) ExtractStreamUnsafe(ctx context.Context, dir string, r io.
 		}
 		return err
 	}
-
 	return fs.extractStream(ctx, extractStreamOptions{
 		Directory: dir,
 		Format:    format,
@@ -190,7 +189,10 @@ type extractStreamOptions struct {
 
 func (fs *Filesystem) extractStream(ctx context.Context, opts extractStreamOptions) error {
 	// Decompress and extract archive
-	if ex, ok := opts.Format.(archiver.Extractor); ok {
+	ex, ok := opts.Format.(archiver.Extractor)
+	if !ok {
+		return nil
+	}
 	return ex.Extract(ctx, opts.Reader, nil, func(ctx context.Context, f archiver.File) error {
 		if f.IsDir() {
 			return nil
@@ -205,11 +207,7 @@ func (fs *Filesystem) extractStream(ctx context.Context, opts extractStreamOptio
 			return err
 		}
 		defer r.Close()
-			if err := fs.Writefile(p, r); err != nil {
+		if err := fs.Write(p, r, f.Size(), f.Mode()); err != nil {
-				return wrapError(err, opts.FileName)
-			}
-			// Update the file permissions to the one set in the archive.
-			if err := fs.Chmod(p, f.Mode()); err != nil {
 			return wrapError(err, opts.FileName)
 		}
 		// Update the file modification time to the one set in the archive.
@@ -219,5 +217,3 @@ func (fs *Filesystem) extractStream(ctx context.Context, opts extractStreamOptio
 		return nil
 	})
 }
-	return nil
-}

server/filesystem/compress_test.go

@@ -3,17 +3,18 @@ package filesystem
 import (
 	"context"
 	"os"
-	"sync/atomic"
 	"testing"
 
 	. "github.com/franela/goblin"
 )
 
 // Given an archive named test.{ext}, with the following file structure:
+//
 //	test/
 //	|──inside/
 //	|────finside.txt
 //	|──outside.txt
+//
 // this test will ensure that it's being decompressed as expected
 func TestFilesystem_DecompressFile(t *testing.T) {
 	g := Goblin(t)
@@ -47,9 +48,7 @@ func TestFilesystem_DecompressFile(t *testing.T) {
 		}
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
-			atomic.StoreInt64(&fs.diskUsed, 0)
-			atomic.StoreInt64(&fs.diskLimit, 0)
 		})
 	})
 }

server/filesystem/disk_space.go

@@ -3,24 +3,25 @@ package filesystem
 import (
 	"sync"
 	"sync/atomic"
-	"syscall"
 	"time"
 
 	"emperror.dev/errors"
 	"github.com/apex/log"
-	"github.com/karrick/godirwalk"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 type SpaceCheckingOpts struct {
 	AllowStaleResponse bool
 }
 
+// TODO: can this be replaced with some sort of atomic? Like atomic.Pointer?
 type usageLookupTime struct {
 	sync.RWMutex
 	value time.Time
 }
 
-// Update the last time that a disk space lookup was performed.
+// Set sets the last time that a disk space lookup was performed.
 func (ult *usageLookupTime) Set(t time.Time) {
 	ult.Lock()
 	ult.value = t
@@ -35,14 +36,15 @@ func (ult *usageLookupTime) Get() time.Time {
 	return ult.value
 }
 
-// Returns the maximum amount of disk space that this Filesystem instance is allowed to use.
+// MaxDisk returns the maximum amount of disk space that this Filesystem
+// instance is allowed to use.
 func (fs *Filesystem) MaxDisk() int64 {
-	return atomic.LoadInt64(&fs.diskLimit)
+	return fs.unixFS.Limit()
 }
 
-// Sets the disk space limit for this Filesystem instance.
+// SetDiskLimit sets the disk space limit for this Filesystem instance.
 func (fs *Filesystem) SetDiskLimit(i int64) {
-	atomic.SwapInt64(&fs.diskLimit, i)
+	fs.unixFS.SetLimit(i)
 }
 
 // The same concept as HasSpaceAvailable however this will return an error if there is
@@ -65,7 +67,7 @@ func (fs *Filesystem) HasSpaceErr(allowStaleValue bool) error {
 func (fs *Filesystem) HasSpaceAvailable(allowStaleValue bool) bool {
 	size, err := fs.DiskUsage(allowStaleValue)
 	if err != nil {
-		log.WithField("root", fs.root).WithField("error", err).Warn("failed to determine root fs directory size")
+		log.WithField("root", fs.Path()).WithField("error", err).Warn("failed to determine root fs directory size")
 	}
 
 	// If space is -1 or 0 just return true, means they're allowed unlimited.
@@ -84,7 +86,7 @@ func (fs *Filesystem) HasSpaceAvailable(allowStaleValue bool) bool {
 // function for critical logical checks. It should only be used in areas where the actual disk usage
 // does not need to be perfect, e.g. API responses for server resource usage.
 func (fs *Filesystem) CachedUsage() int64 {
-	return atomic.LoadInt64(&fs.diskUsed)
+	return fs.unixFS.Usage()
 }
 
 // Internal helper function to allow other parts of the codebase to check the total used disk space
@@ -114,14 +116,14 @@ func (fs *Filesystem) DiskUsage(allowStaleValue bool) (int64, error) {
 			// currently performing a lookup, just do the disk usage calculation in the background.
 			go func(fs *Filesystem) {
 				if _, err := fs.updateCachedDiskUsage(); err != nil {
-					log.WithField("root", fs.root).WithField("error", err).Warn("failed to update fs disk usage from within routine")
+					log.WithField("root", fs.Path()).WithField("error", err).Warn("failed to update fs disk usage from within routine")
 				}
 			}(fs)
 		}
 	}
 
 	// Return the currently cached value back to the calling function.
-	return atomic.LoadInt64(&fs.diskUsed), nil
+	return fs.unixFS.Usage(), nil
 }
 
 // Updates the currently used disk space for a server.
@@ -149,63 +151,46 @@ func (fs *Filesystem) updateCachedDiskUsage() (int64, error) {
 	// error encountered.
 	fs.lastLookupTime.Set(time.Now())
 
-	atomic.StoreInt64(&fs.diskUsed, size)
+	fs.unixFS.SetUsage(size)
 
 	return size, err
 }
 
-// Determines the directory size of a given location by running parallel tasks to iterate
+// DirectorySize calculates the size of a directory and its descendants.
-// through all of the folders. Returns the size in bytes. This can be a fairly taxing operation
+func (fs *Filesystem) DirectorySize(root string) (int64, error) {
-// on locations with tons of files, so it is recommended that you cache the output.
+	dirfd, name, closeFd, err := fs.unixFS.SafePath(root)
-func (fs *Filesystem) DirectorySize(dir string) (int64, error) {
+	defer closeFd()
-	d, err := fs.SafePath(dir)
 	if err != nil {
 		return 0, err
 	}
 
-	var size int64
+	var size atomic.Int64
-	var st syscall.Stat_t
+	err = fs.unixFS.WalkDirat(dirfd, name, func(dirfd int, name, _ string, d ufs.DirEntry, err error) error {
-
-	err = godirwalk.Walk(d, &godirwalk.Options{
-		Unsorted: true,
-		Callback: func(p string, e *godirwalk.Dirent) error {
-			// If this is a symlink then resolve the final destination of it before trying to continue walking
-			// over its contents. If it resolves outside the server data directory just skip everything else for
-			// it. Otherwise, allow it to continue.
-			if e.IsSymlink() {
-				if _, err := fs.SafePath(p); err != nil {
-					if IsErrorCode(err, ErrCodePathResolution) {
-						return godirwalk.SkipThis
-					}
-
-					return err
-				}
-			}
-
-			if !e.IsDir() {
-				_ = syscall.Lstat(p, &st)
-				atomic.AddInt64(&size, st.Size)
-			}
-
-			return nil
-		},
-	})
-
-	return size, errors.WrapIf(err, "server/filesystem: directorysize: failed to walk directory")
-}
-
-// Helper function to determine if a server has space available for a file of a given size.
-// If space is available, no error will be returned, otherwise an ErrNotEnoughSpace error
-// will be raised.
-func (fs *Filesystem) HasSpaceFor(size int64) error {
-	if fs.MaxDisk() == 0 {
-		return nil
-	}
-	s, err := fs.DiskUsage(true)
 		if err != nil {
-		return err
+			return errors.Wrap(err, "walkdirat err")
 		}
-	if (s + size) > fs.MaxDisk() {
+
+		// Only calculate the size of regular files.
+		if !d.Type().IsRegular() {
+			return nil
+		}
+
+		info, err := fs.unixFS.Lstatat(dirfd, name)
+		if err != nil {
+			return errors.Wrap(err, "lstatat err")
+		}
+
+		// TODO: detect if info is a hard-link and de-duplicate it.
+		// ref; https://github.com/pterodactyl/wings/pull/181/files
+
+		size.Add(info.Size())
+		return nil
+	})
+	return size.Load(), errors.WrapIf(err, "server/filesystem: directorysize: failed to walk directory")
+}
+
+func (fs *Filesystem) HasSpaceFor(size int64) error {
+	if !fs.unixFS.CanFit(size) {
 		return newFilesystemError(ErrCodeDiskSpace, nil)
 	}
 	return nil
@@ -213,24 +198,5 @@ func (fs *Filesystem) HasSpaceFor(size int64) error {
 
 // Updates the disk usage for the Filesystem instance.
 func (fs *Filesystem) addDisk(i int64) int64 {
-	size := atomic.LoadInt64(&fs.diskUsed)
+	return fs.unixFS.Add(i)
-
-	// Sorry go gods. This is ugly but the best approach I can come up with for right
-	// now without completely re-evaluating the logic we use for determining disk space.
-	//
-	// Normally I would just be using the atomic load right below, but I'm not sure about
-	// the scenarios where it is 0 because nothing has run that would trigger a disk size
-	// calculation?
-	//
-	// Perhaps that isn't even a concern for the sake of this?
-	if !fs.isTest {
-		size, _ = fs.DiskUsage(true)
-	}
-
-	// If we're dropping below 0 somehow just cap it to 0.
-	if (size + i) < 0 {
-		return atomic.SwapInt64(&fs.diskUsed, 0)
-	}
-
-	return atomic.AddInt64(&fs.diskUsed, i)
 }

server/filesystem/errors.go

@@ -2,11 +2,12 @@ package filesystem
 
 import (
 	"fmt"
-	"os"
 	"path/filepath"
 
 	"emperror.dev/errors"
 	"github.com/apex/log"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 type ErrorCode string
@@ -86,15 +87,15 @@ func (e *Error) Unwrap() error {
 
 // Generates an error logger instance with some basic information.
 func (fs *Filesystem) error(err error) *log.Entry {
-	return log.WithField("subsystem", "filesystem").WithField("root", fs.root).WithField("error", err)
+	return log.WithField("subsystem", "filesystem").WithField("root", fs.Path()).WithField("error", err)
 }
 
 // Handle errors encountered when walking through directories.
 //
 // If there is a path resolution error just skip the item entirely. Only return this for a
 // directory, otherwise return nil. Returning this error for a file will stop the walking
-// for the remainder of the directory. This is assuming an os.FileInfo struct was even returned.
+// for the remainder of the directory. This is assuming an FileInfo struct was even returned.
-func (fs *Filesystem) handleWalkerError(err error, f os.FileInfo) error {
+func (fs *Filesystem) handleWalkerError(err error, f ufs.FileInfo) error {
 	if !IsErrorCode(err, ErrCodePathResolution) {
 		return err
 	}

server/filesystem/filesystem.go

@@ -1,13 +1,11 @@
 package filesystem
 
 import (
-	"bufio"
+	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
-	"path"
 	"path/filepath"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -15,220 +13,205 @@ import (
 	"time"
 
 	"emperror.dev/errors"
+	"github.com/apex/log"
 	"github.com/gabriel-vasile/mimetype"
-	"github.com/karrick/godirwalk"
 	ignore "github.com/sabhiram/go-gitignore"
 
 	"github.com/pterodactyl/wings/config"
-	"github.com/pterodactyl/wings/system"
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
+// TODO: detect and enable
+var useOpenat2 = true
+
 type Filesystem struct {
+	unixFS *ufs.Quota
+
 	mu                sync.RWMutex
 	lastLookupTime    *usageLookupTime
-	lookupInProgress  *system.AtomicBool
+	lookupInProgress  atomic.Bool
-	diskUsed          int64
 	diskCheckInterval time.Duration
 	denylist          *ignore.GitIgnore
 
-	// The maximum amount of disk space (in bytes) that this Filesystem instance can use.
-	diskLimit int64
-
-	// The root data directory path for this Filesystem instance.
-	root string
-
 	isTest bool
 }
 
 // New creates a new Filesystem instance for a given server.
-func New(root string, size int64, denylist []string) *Filesystem {
+func New(root string, size int64, denylist []string) (*Filesystem, error) {
+	if err := os.MkdirAll(root, 0o755); err != nil {
+		return nil, err
+	}
+	unixFS, err := ufs.NewUnixFS(root, config.UseOpenat2())
+	if err != nil {
+		return nil, err
+	}
+	quota := ufs.NewQuota(unixFS, size)
+
 	return &Filesystem{
-		root:              root,
+		unixFS: quota,
-		diskLimit:         size,
+
 		diskCheckInterval: time.Duration(config.Get().System.DiskCheckInterval),
 		lastLookupTime:    &usageLookupTime{},
-		lookupInProgress:  system.NewAtomicBool(false),
 		denylist:          ignore.CompileIgnoreLines(denylist...),
-	}
+	}, nil
 }
 
 // Path returns the root path for the Filesystem instance.
 func (fs *Filesystem) Path() string {
-	return fs.root
+	return fs.unixFS.BasePath()
+}
+
+// ReadDir reads directory entries.
+func (fs *Filesystem) ReadDir(path string) ([]ufs.DirEntry, error) {
+	return fs.unixFS.ReadDir(path)
+}
+
+// ReadDirStat is like ReadDir except that it returns FileInfo for each entry
+// instead of just a DirEntry.
+func (fs *Filesystem) ReadDirStat(path string) ([]ufs.FileInfo, error) {
+	return ufs.ReadDirMap(fs.unixFS.UnixFS, path, func(e ufs.DirEntry) (ufs.FileInfo, error) {
+		return e.Info()
+	})
 }
 
 // File returns a reader for a file instance as well as the stat information.
-func (fs *Filesystem) File(p string) (*os.File, Stat, error) {
+func (fs *Filesystem) File(p string) (ufs.File, Stat, error) {
-	cleaned, err := fs.SafePath(p)
+	f, err := fs.unixFS.Open(p)
 	if err != nil {
-		return nil, Stat{}, errors.WithStackIf(err)
+		return nil, Stat{}, err
 	}
-	st, err := fs.Stat(cleaned)
+	st, err := statFromFile(f)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) {
+		_ = f.Close()
-			return nil, Stat{}, newFilesystemError(ErrNotExist, err)
+		return nil, Stat{}, err
-		}
-		return nil, Stat{}, errors.WithStackIf(err)
-	}
-	if st.IsDir() {
-		return nil, Stat{}, newFilesystemError(ErrCodeIsDirectory, nil)
-	}
-	f, err := os.Open(cleaned)
-	if err != nil {
-		return nil, Stat{}, errors.WithStackIf(err)
 	}
 	return f, st, nil
 }
 
+func (fs *Filesystem) UnixFS() *ufs.UnixFS {
+	return fs.unixFS.UnixFS
+}
+
 // Touch acts by creating the given file and path on the disk if it is not present
 // already. If  it is present, the file is opened using the defaults which will truncate
 // the contents. The opened file is then returned to the caller.
-func (fs *Filesystem) Touch(p string, flag int) (*os.File, error) {
+func (fs *Filesystem) Touch(p string, flag int) (ufs.File, error) {
-	cleaned, err := fs.SafePath(p)
+	return fs.unixFS.Touch(p, flag, 0o644)
-	if err != nil {
-		return nil, err
-	}
-	f, err := os.OpenFile(cleaned, flag, 0o644)
-	if err == nil {
-		return f, nil
-	}
-	if f != nil {
-		_ = f.Close()
-	}
-	// If the error is not because it doesn't exist then we just need to bail at this point.
-	if !errors.Is(err, os.ErrNotExist) {
-		return nil, errors.Wrap(err, "server/filesystem: touch: failed to open file handle")
-	}
-	// Only create and chown the directory if it doesn't exist.
-	if _, err := os.Stat(filepath.Dir(cleaned)); errors.Is(err, os.ErrNotExist) {
-		// Create the path leading up to the file we're trying to create, setting the final perms
-		// on it as we go.
-		if err := os.MkdirAll(filepath.Dir(cleaned), 0o755); err != nil {
-			return nil, errors.Wrap(err, "server/filesystem: touch: failed to create directory tree")
-		}
-		if err := fs.Chown(filepath.Dir(cleaned)); err != nil {
-			return nil, err
-		}
-	}
-	o := &fileOpener{}
-	// Try to open the file now that we have created the pathing necessary for it, and then
-	// Chown that file so that the permissions don't mess with things.
-	f, err = o.open(cleaned, flag, 0o644)
-	if err != nil {
-		return nil, errors.Wrap(err, "server/filesystem: touch: failed to open file with wait")
-	}
-	_ = fs.Chown(cleaned)
-	return f, nil
 }
 
 // Writefile writes a file to the system. If the file does not already exist one
 // will be created. This will also properly recalculate the disk space used by
 // the server when writing new files or modifying existing ones.
+//
+// DEPRECATED: use `Write` instead.
 func (fs *Filesystem) Writefile(p string, r io.Reader) error {
-	cleaned, err := fs.SafePath(p)
+	var currentSize int64
+	st, err := fs.unixFS.Stat(p)
+	if err != nil && !errors.Is(err, ufs.ErrNotExist) {
+		return errors.Wrap(err, "server/filesystem: writefile: failed to stat file")
+	} else if err == nil {
+		if st.IsDir() {
+			// TODO: resolved
+			return errors.WithStack(&Error{code: ErrCodeIsDirectory, resolved: ""})
+		}
+		currentSize = st.Size()
+	}
+
+	// Touch the file and return the handle to it at this point. This will
+	// create or truncate the file, and create any necessary parent directories
+	// if they are missing.
+	file, err := fs.unixFS.Touch(p, ufs.O_RDWR|ufs.O_TRUNC, 0o644)
 	if err != nil {
+		return fmt.Errorf("error touching file: %w", err)
+	}
+	defer file.Close()
+
+	// Do not use CopyBuffer here, it is wasteful as the file implements
+	// io.ReaderFrom, which causes it to not use the buffer anyways.
+	n, err := io.Copy(file, r)
+
+	// Adjust the disk usage to account for the old size and the new size of the file.
+	fs.unixFS.Add(n - currentSize)
+
+	if err := fs.chownFile(p); err != nil {
+		return fmt.Errorf("error chowning file: %w", err)
+	}
+	// Return the error from io.Copy.
 	return err
 }
 
+func (fs *Filesystem) Write(p string, r io.Reader, newSize int64, mode ufs.FileMode) error {
 	var currentSize int64
-	// If the file does not exist on the system already go ahead and create the pathway
+	st, err := fs.unixFS.Stat(p)
-	// to it and an empty file. We'll then write to it later on after this completes.
+	if err != nil && !errors.Is(err, ufs.ErrNotExist) {
-	stat, err := os.Stat(cleaned)
-	if err != nil && !os.IsNotExist(err) {
 		return errors.Wrap(err, "server/filesystem: writefile: failed to stat file")
 	} else if err == nil {
-		if stat.IsDir() {
+		if st.IsDir() {
-			return errors.WithStack(&Error{code: ErrCodeIsDirectory, resolved: cleaned})
+			// TODO: resolved
+			return errors.WithStack(&Error{code: ErrCodeIsDirectory, resolved: ""})
 		}
-		currentSize = stat.Size()
+		currentSize = st.Size()
 	}
 
-	br := bufio.NewReader(r)
 	// Check that the new size we're writing to the disk can fit. If there is currently
 	// a file we'll subtract that current file size from the size of the buffer to determine
 	// the amount of new data we're writing (or amount we're removing if smaller).
-	if err := fs.HasSpaceFor(int64(br.Size()) - currentSize); err != nil {
+	if err := fs.HasSpaceFor(newSize - currentSize); err != nil {
 		return err
 	}
 
-	// Touch the file and return the handle to it at this point. This will create the file,
+	// Touch the file and return the handle to it at this point. This will
-	// any necessary directories, and set the proper owner of the file.
+	// create or truncate the file, and create any necessary parent directories
-	file, err := fs.Touch(cleaned, os.O_RDWR|os.O_CREATE|os.O_TRUNC)
+	// if they are missing.
+	file, err := fs.unixFS.Touch(p, ufs.O_RDWR|ufs.O_TRUNC, mode)
 	if err != nil {
 		return err
 	}
 	defer file.Close()
 
-	buf := make([]byte, 1024*4)
+	// Do not use CopyBuffer here, it is wasteful as the file implements
-	sz, err := io.CopyBuffer(file, r, buf)
+	// io.ReaderFrom, which causes it to not use the buffer anyways.
+	n, err := io.Copy(file, io.LimitReader(r, newSize))
 
 	// Adjust the disk usage to account for the old size and the new size of the file.
-	fs.addDisk(sz - currentSize)
+	fs.unixFS.Add(n - currentSize)
 
-	return fs.unsafeChown(cleaned)
+	if err := fs.chownFile(p); err != nil {
-}
-
-// Creates a new directory (name) at a specified path (p) for the server.
-func (fs *Filesystem) CreateDirectory(name string, p string) error {
-	cleaned, err := fs.SafePath(path.Join(p, name))
-	if err != nil {
 		return err
 	}
-	return os.MkdirAll(cleaned, 0o755)
+	// Return the error from io.Copy.
+	return err
 }
 
-// Rename moves (or renames) a file or directory.
+// CreateDirectory creates a new directory (name) at a specified path (p) for
-func (fs *Filesystem) Rename(from string, to string) error {
+// the server.
-	cleanedFrom, err := fs.SafePath(from)
+func (fs *Filesystem) CreateDirectory(name string, p string) error {
-	if err != nil {
+	return fs.unixFS.MkdirAll(filepath.Join(p, name), 0o755)
-		return errors.WithStack(err)
 }
 
-	cleanedTo, err := fs.SafePath(to)
+func (fs *Filesystem) Rename(oldpath, newpath string) error {
-	if err != nil {
+	return fs.unixFS.Rename(oldpath, newpath)
-		return errors.WithStack(err)
 }
 
-	// If the target file or directory already exists the rename function will fail, so just
+func (fs *Filesystem) Symlink(oldpath, newpath string) error {
-	// bail out now.
+	return fs.unixFS.Symlink(oldpath, newpath)
-	if _, err := os.Stat(cleanedTo); err == nil {
-		return os.ErrExist
 }
 
-	if cleanedTo == fs.Path() {
+func (fs *Filesystem) chownFile(name string) error {
-		return errors.New("attempting to rename into an invalid directory space")
+	if fs.isTest {
-	}
-
-	d := strings.TrimSuffix(cleanedTo, path.Base(cleanedTo))
-	// Ensure that the directory we're moving into exists correctly on the system. Only do this if
-	// we're not at the root directory level.
-	if d != fs.Path() {
-		if mkerr := os.MkdirAll(d, 0o755); mkerr != nil {
-			return errors.WithMessage(mkerr, "failed to create directory structure for file rename")
-		}
-	}
-
-	if err := os.Rename(cleanedFrom, cleanedTo); err != nil {
-		return errors.WithStack(err)
-	}
 		return nil
 	}
 
-// Recursively iterates over a file or directory and sets the permissions on all of the
+	uid := config.Get().System.User.Uid
+	gid := config.Get().System.User.Gid
+	return fs.unixFS.Lchown(name, uid, gid)
+}
+
+// Chown recursively iterates over a file or directory and sets the permissions on all of the
 // underlying files. Iterate over all of the files and directories. If it is a file just
 // go ahead and perform the chown operation. Otherwise dig deeper into the directory until
 // we've run out of directories to dig into.
-func (fs *Filesystem) Chown(path string) error {
+func (fs *Filesystem) Chown(p string) error {
-	cleaned, err := fs.SafePath(path)
-	if err != nil {
-		return err
-	}
-	return fs.unsafeChown(cleaned)
-}
-
-// unsafeChown chowns the given path, without checking if the path is safe. This should only be used
-// when the path has already been checked.
-func (fs *Filesystem) unsafeChown(path string) error {
 	if fs.isTest {
 		return nil
 	}
@@ -236,54 +219,44 @@ func (fs *Filesystem) unsafeChown(path string) error {
 	uid := config.Get().System.User.Uid
 	gid := config.Get().System.User.Gid
 
+	dirfd, name, closeFd, err := fs.unixFS.SafePath(p)
+	defer closeFd()
+	if err != nil {
+		return err
+	}
+
 	// Start by just chowning the initial path that we received.
-	if err := os.Chown(path, uid, gid); err != nil {
+	if err := fs.unixFS.Lchownat(dirfd, name, uid, gid); err != nil {
 		return errors.Wrap(err, "server/filesystem: chown: failed to chown path")
 	}
 
 	// If this is not a directory we can now return from the function, there is nothing
 	// left that we need to do.
-	if st, err := os.Stat(path); err != nil || !st.IsDir() {
+	if st, err := fs.unixFS.Lstatat(dirfd, name); err != nil || !st.IsDir() {
 		return nil
 	}
 
-	// If this was a directory, begin walking over its contents recursively and ensure that all
+	// This walker is probably some of the most efficient code in Wings. It has
-	// of the subfiles and directories get their permissions updated as well.
+	// an internally re-used buffer for listing directory entries and doesn't
-	err := godirwalk.Walk(path, &godirwalk.Options{
+	// need to check if every individual path it touches is safe as the code
-		Unsorted: true,
+	// doesn't traverse symlinks, is immune to symlink timing attacks, and
-		Callback: func(p string, e *godirwalk.Dirent) error {
+	// gives us a dirfd and file name to make a direct syscall with.
-			// Do not attempt to chown a symlink. Go's os.Chown function will affect the symlink
+	if err := fs.unixFS.WalkDirat(dirfd, name, func(dirfd int, name, _ string, info ufs.DirEntry, err error) error {
-			// so if it points to a location outside the data directory the user would be able to
-			// (un)intentionally modify that files permissions.
-			if e.IsSymlink() {
-				if e.IsDir() {
-					return godirwalk.SkipThis
-				}
-
-				return nil
-			}
-
-			return os.Chown(p, uid, gid)
-		},
-	})
-	return errors.Wrap(err, "server/filesystem: chown: failed to chown during walk function")
-}
-
-func (fs *Filesystem) Chmod(path string, mode os.FileMode) error {
-	cleaned, err := fs.SafePath(path)
 		if err != nil {
 			return err
 		}
-
+		if err := fs.unixFS.Lchownat(dirfd, name, uid, gid); err != nil {
-	if fs.isTest {
-		return nil
-	}
-
-	if err := os.Chmod(cleaned, mode); err != nil {
 			return err
 		}
-
 		return nil
+	}); err != nil {
+		return fmt.Errorf("server/filesystem: chown: failed to chown during walk function: %w", err)
+	}
+	return nil
+}
+
+func (fs *Filesystem) Chmod(path string, mode ufs.FileMode) error {
+	return fs.unixFS.Chmod(path, mode)
 }
 
 // Begin looping up to 50 times to try and create a unique copy file name. This will take
@@ -294,7 +267,7 @@ func (fs *Filesystem) Chmod(path string, mode os.FileMode) error {
 // Could probably make this more efficient by checking if there are any files matching the copy
 // pattern, and trying to find the highest number and then incrementing it by one rather than
 // looping endlessly.
-func (fs *Filesystem) findCopySuffix(dir string, name string, extension string) (string, error) {
+func (fs *Filesystem) findCopySuffix(dirfd int, name, extension string) (string, error) {
 	var i int
 	suffix := " copy"
 
@@ -306,11 +279,10 @@ func (fs *Filesystem) findCopySuffix(dir string, name string, extension string)
 		n := name + suffix + extension
 		// If we stat the file and it does not exist that means we're good to create the copy. If it
 		// does exist, we'll just continue to the next loop and try again.
-		if _, err := fs.Stat(path.Join(dir, n)); err != nil {
+		if _, err := fs.unixFS.Lstatat(dirfd, n); err != nil {
-			if !errors.Is(err, os.ErrNotExist) {
+			if !errors.Is(err, ufs.ErrNotExist) {
 				return "", err
 			}
-
 			break
 		}
 
@@ -322,53 +294,68 @@ func (fs *Filesystem) findCopySuffix(dir string, name string, extension string)
 	return name + suffix + extension, nil
 }
 
-// Copies a given file to the same location and appends a suffix to the file to indicate that
+// Copy copies a given file to the same location and appends a suffix to the
-// it has been copied.
+// file to indicate that it has been copied.
 func (fs *Filesystem) Copy(p string) error {
-	cleaned, err := fs.SafePath(p)
+	dirfd, name, closeFd, err := fs.unixFS.SafePath(p)
+	defer closeFd()
 	if err != nil {
 		return err
 	}
-
+	source, err := fs.unixFS.OpenFileat(dirfd, name, ufs.O_RDONLY, 0)
-	s, err := os.Stat(cleaned)
-	if err != nil {
-		return err
-	} else if s.IsDir() || !s.Mode().IsRegular() {
-		// If this is a directory or not a regular file, just throw a not-exist error
-		// since anything calling this function should understand what that means.
-		return os.ErrNotExist
-	}
-
-	// Check that copying this file wouldn't put the server over its limit.
-	if err := fs.HasSpaceFor(s.Size()); err != nil {
-		return err
-	}
-
-	base := filepath.Base(cleaned)
-	relative := strings.TrimSuffix(strings.TrimPrefix(cleaned, fs.Path()), base)
-	extension := filepath.Ext(base)
-	name := strings.TrimSuffix(base, extension)
-
-	// Ensure that ".tar" is also counted as apart of the file extension.
-	// There might be a better way to handle this for other double file extensions,
-	// but this is a good workaround for now.
-	if strings.HasSuffix(name, ".tar") {
-		extension = ".tar" + extension
-		name = strings.TrimSuffix(name, ".tar")
-	}
-
-	source, err := os.Open(cleaned)
 	if err != nil {
 		return err
 	}
 	defer source.Close()
+	info, err := source.Stat()
+	if err != nil {
+		return err
+	}
+	if info.IsDir() || !info.Mode().IsRegular() {
+		// If this is a directory or not a regular file, just throw a not-exist error
+		// since anything calling this function should understand what that means.
+		return ufs.ErrNotExist
+	}
+	currentSize := info.Size()
 
-	n, err := fs.findCopySuffix(relative, name, extension)
+	// Check that copying this file wouldn't put the server over its limit.
+	if err := fs.HasSpaceFor(currentSize); err != nil {
+		return err
+	}
+
+	base := info.Name()
+	extension := filepath.Ext(base)
+	baseName := strings.TrimSuffix(base, extension)
+
+	// Ensure that ".tar" is also counted as apart of the file extension.
+	// There might be a better way to handle this for other double file extensions,
+	// but this is a good workaround for now.
+	if strings.HasSuffix(baseName, ".tar") {
+		extension = ".tar" + extension
+		baseName = strings.TrimSuffix(baseName, ".tar")
+	}
+
+	newName, err := fs.findCopySuffix(dirfd, baseName, extension)
+	if err != nil {
+		return err
+	}
+	dst, err := fs.unixFS.OpenFileat(dirfd, newName, ufs.O_WRONLY|ufs.O_CREATE, info.Mode())
 	if err != nil {
 		return err
 	}
 
-	return fs.Writefile(path.Join(relative, n), source)
+	// Do not use CopyBuffer here, it is wasteful as the file implements
+	// io.ReaderFrom, which causes it to not use the buffer anyways.
+	n, err := io.Copy(dst, io.LimitReader(source, currentSize))
+	fs.unixFS.Add(n)
+
+	if !fs.isTest {
+		if err := fs.unixFS.Lchownat(dirfd, newName, config.Get().System.User.Uid, config.Get().System.User.Gid); err != nil {
+			return err
+		}
+	}
+	// Return the error from io.Copy.
+	return err
 }
 
 // TruncateRootDirectory removes _all_ files and directories from a server's
@@ -380,211 +367,128 @@ func (fs *Filesystem) TruncateRootDirectory() error {
 	if err := os.Mkdir(fs.Path(), 0o755); err != nil {
 		return err
 	}
-	atomic.StoreInt64(&fs.diskUsed, 0)
+	_ = fs.unixFS.Close()
+	unixFS, err := ufs.NewUnixFS(fs.Path(), config.UseOpenat2())
+	if err != nil {
+		return err
+	}
+	var limit int64
+	if fs.isTest {
+		limit = 0
+	} else {
+		limit = fs.unixFS.Limit()
+	}
+	fs.unixFS = ufs.NewQuota(unixFS, limit)
 	return nil
 }
 
 // Delete removes a file or folder from the system. Prevents the user from
 // accidentally (or maliciously) removing their root server data directory.
 func (fs *Filesystem) Delete(p string) error {
-	// This is one of the few (only?) places in the codebase where we're explicitly not using
+	return fs.unixFS.RemoveAll(p)
-	// the SafePath functionality when working with user provided input. If we did, you would
+}
-	// not be able to delete a file that is a symlink pointing to a location outside the data
+
-	// directory.
+//type fileOpener struct {
+//	fs   *Filesystem
+//	busy uint
+//}
 //
-	// We also want to avoid resolving a symlink that points _within_ the data directory and thus
+//// Attempts to open a given file up to "attempts" number of times, using a backoff. If the file
-	// deleting the actual source file for the symlink rather than the symlink itself. For these
+//// cannot be opened because of a "text file busy" error, we will attempt until the number of attempts
-	// purposes just resolve the actual file path using filepath.Join() and confirm that the path
+//// has been exhaused, at which point we will abort with an error.
-	// exists within the data directory.
+//func (fo *fileOpener) open(path string, flags int, perm ufs.FileMode) (ufs.File, error) {
-	resolved := fs.unsafeFilePath(p)
+//	for {
-	if !fs.unsafeIsInDataDirectory(resolved) {
+//		f, err := fo.fs.unixFS.OpenFile(path, flags, perm)
-		return NewBadPathResolution(p, resolved)
-	}
-
-	// Block any whoopsies.
-	if resolved == fs.Path() {
-		return errors.New("cannot delete root server directory")
-	}
-
-	st, err := os.Lstat(resolved)
-	if err != nil {
-		if !os.IsNotExist(err) {
-			fs.error(err).Warn("error while attempting to stat file before deletion")
-			return err
-		}
-
-		// The following logic is used to handle a case where a user attempts to
-		// delete a file that does not exist through a directory symlink.
-		// We don't want to reveal that the file does not exist, so we validate
-		// the path of the symlink and return a bad path error if it is invalid.
-
-		// The requested file or directory doesn't exist, so at this point we
-		// need to iterate up the path chain until we hit a directory that
-		// _does_ exist and can be validated.
-		parts := strings.Split(filepath.Dir(resolved), "/")
-
-		// Range over all the path parts and form directory paths from the end
-		// moving up until we have a valid resolution, or we run out of paths to
-		// try.
-		for k := range parts {
-			try := strings.Join(parts[:(len(parts)-k)], "/")
-			if !fs.unsafeIsInDataDirectory(try) {
-				break
-			}
-
-			t, err := filepath.EvalSymlinks(try)
-			if err == nil {
-				if !fs.unsafeIsInDataDirectory(t) {
-					return NewBadPathResolution(p, t)
-				}
-				break
-			}
-		}
-
-		// Always return early if the file does not exist.
-		return nil
-	}
-
-	// If the file is not a symlink, we need to check that it is not within a
-	// symlinked directory that points outside the data directory.
-	if st.Mode()&os.ModeSymlink == 0 {
-		ep, err := filepath.EvalSymlinks(resolved)
-		if err != nil {
-			if !os.IsNotExist(err) {
-				return err
-			}
-		} else if !fs.unsafeIsInDataDirectory(ep) {
-			return NewBadPathResolution(p, ep)
-		}
-	}
-
-	if st.IsDir() {
-		if s, err := fs.DirectorySize(resolved); err == nil {
-			fs.addDisk(-s)
-		}
-	} else {
-		fs.addDisk(-st.Size())
-	}
-
-	return os.RemoveAll(resolved)
-}
-
-type fileOpener struct {
-	busy uint
-}
-
-// Attempts to open a given file up to "attempts" number of times, using a backoff. If the file
-// cannot be opened because of a "text file busy" error, we will attempt until the number of attempts
-// has been exhaused, at which point we will abort with an error.
-func (fo *fileOpener) open(path string, flags int, perm os.FileMode) (*os.File, error) {
-	for {
-		f, err := os.OpenFile(path, flags, perm)
-
-		// If there is an error because the text file is busy, go ahead and sleep for a few
-		// hundred milliseconds and then try again up to three times before just returning the
-		// error back to the caller.
 //
-		// Based on code from: https://github.com/golang/go/issues/22220#issuecomment-336458122
+//		// If there is an error because the text file is busy, go ahead and sleep for a few
-		if err != nil && fo.busy < 3 && strings.Contains(err.Error(), "text file busy") {
+//		// hundred milliseconds and then try again up to three times before just returning the
-			time.Sleep(100 * time.Millisecond << fo.busy)
+//		// error back to the caller.
-			fo.busy++
+//		//
-			continue
+//		// Based on code from: https://github.com/golang/go/issues/22220#issuecomment-336458122
-		}
+//		if err != nil && fo.busy < 3 && strings.Contains(err.Error(), "text file busy") {
-
+//			time.Sleep(100 * time.Millisecond << fo.busy)
-		return f, err
+//			fo.busy++
-	}
+//			continue
-}
+//		}
+//
+//		return f, err
+//	}
+//}
 
 // ListDirectory lists the contents of a given directory and returns stat
 // information about each file and folder within it.
 func (fs *Filesystem) ListDirectory(p string) ([]Stat, error) {
-	cleaned, err := fs.SafePath(p)
+	// Read entries from the path on the filesystem, using the mapped reader, so
+	// we can map the DirEntry slice into a Stat slice with mimetype information.
+	out, err := ufs.ReadDirMap(fs.unixFS.UnixFS, p, func(e ufs.DirEntry) (Stat, error) {
+		info, err := e.Info()
 		if err != nil {
-		return nil, err
+			return Stat{}, err
 		}
 
-	files, err := ioutil.ReadDir(cleaned)
+		var d string
-	if err != nil {
+		if e.Type().IsDir() {
-		return nil, err
+			d = "inode/directory"
-	}
-
-	var wg sync.WaitGroup
-
-	// You must initialize the output of this directory as a non-nil value otherwise
-	// when it is marshaled into a JSON object you'll just get 'null' back, which will
-	// break the panel badly.
-	out := make([]Stat, len(files))
-
-	// Iterate over all of the files and directories returned and perform an async process
-	// to get the mime-type for them all.
-	for i, file := range files {
-		wg.Add(1)
-
-		go func(idx int, f os.FileInfo) {
-			defer wg.Done()
-
-			var m *mimetype.MIME
-			d := "inode/directory"
-			if !f.IsDir() {
-				cleanedp := filepath.Join(cleaned, f.Name())
-				if f.Mode()&os.ModeSymlink != 0 {
-					cleanedp, _ = fs.SafePath(filepath.Join(cleaned, f.Name()))
-				}
-
-				// Don't try to detect the type on a pipe — this will just hang the application and
-				// you'll never get a response back.
-				//
-				// @see https://github.com/pterodactyl/panel/issues/4059
-				if cleanedp != "" && f.Mode()&os.ModeNamedPipe == 0 {
-					m, _ = mimetype.DetectFile(filepath.Join(cleaned, f.Name()))
 		} else {
-					// Just pass this for an unknown type because the file could not safely be resolved within
-					// the server data path.
 			d = "application/octet-stream"
 		}
+		var m *mimetype.MIME
+		if e.Type().IsRegular() {
+			// TODO: I should probably find a better way to do this.
+			eO := e.(interface {
+				Open() (ufs.File, error)
+			})
+			f, err := eO.Open()
+			if err != nil {
+				return Stat{}, err
+			}
+			m, err = mimetype.DetectReader(f)
+			if err != nil {
+				log.Error(err.Error())
+			}
+			_ = f.Close()
 		}
 
-			st := Stat{FileInfo: f, Mimetype: d}
+		st := Stat{FileInfo: info, Mimetype: d}
 		if m != nil {
 			st.Mimetype = m.String()
 		}
-			out[idx] = st
+		return st, nil
-		}(i, file)
+	})
+	if err != nil {
+		return nil, err
 	}
 
-	wg.Wait()
+	// Sort entries alphabetically.
-
+	slices.SortStableFunc(out, func(a, b Stat) int {
-	// Sort the output alphabetically to begin with since we've run the output
+		switch {
-	// through an asynchronous process and the order is gonna be very random.
+		case a.Name() == b.Name():
-	sort.SliceStable(out, func(i, j int) bool {
+			return 0
-		if out[i].Name() == out[j].Name() || out[i].Name() > out[j].Name() {
+		case a.Name() > b.Name():
-			return true
+			return 1
+		default:
+			return -1
 		}
-		return false
 	})
 
-	// Then, sort it so that directories are listed first in the output. Everything
+	// Sort folders before other file types.
-	// will continue to be alphabetized at this point.
+	slices.SortStableFunc(out, func(a, b Stat) int {
-	sort.SliceStable(out, func(i, j int) bool {
+		switch {
-		return out[i].IsDir()
+		case a.IsDir() && b.IsDir():
+			return 0
+		case a.IsDir():
+			return 1
+		default:
+			return -1
+		}
 	})
 
 	return out, nil
 }
 
 func (fs *Filesystem) Chtimes(path string, atime, mtime time.Time) error {
-	cleaned, err := fs.SafePath(path)
-	if err != nil {
-		return err
-	}
-
 	if fs.isTest {
 		return nil
 	}
-
+	return fs.unixFS.Chtimes(path, atime, mtime)
-	if err := os.Chtimes(cleaned, atime, mtime); err != nil {
-		return err
-	}
-
-	return nil
 }

server/filesystem/filesystem_test.go

@@ -7,12 +7,13 @@ import (
 	"math/rand"
 	"os"
 	"path/filepath"
-	"sync/atomic"
 	"testing"
 	"unicode/utf8"
 
 	. "github.com/franela/goblin"
 
+	"github.com/pterodactyl/wings/internal/ufs"
+
 	"github.com/pterodactyl/wings/config"
 )
 
@@ -28,15 +29,23 @@ func NewFs() (*Filesystem, *rootFs) {
 	tmpDir, err := os.MkdirTemp(os.TempDir(), "pterodactyl")
 	if err != nil {
 		panic(err)
+		return nil, nil
 	}
-	// defer os.RemoveAll(tmpDir)
 
 	rfs := rootFs{root: tmpDir}
 
-	rfs.reset()
+	p := filepath.Join(tmpDir, "server")
+	if err := os.Mkdir(p, 0o755); err != nil {
+		panic(err)
+		return nil, nil
+	}
 
-	fs := New(filepath.Join(tmpDir, "/server"), 0, []string{})
+	fs, _ := New(p, 0, []string{})
 	fs.isTest = true
+	if err := fs.TruncateRootDirectory(); err != nil {
+		panic(err)
+		return nil, nil
+	}
 
 	return fs, &rfs
 }
@@ -45,7 +54,7 @@ type rootFs struct {
 	root string
 }
 
-func getFileContent(file *os.File) string {
+func getFileContent(file ufs.File) string {
 	var w bytes.Buffer
 	if _, err := bufio.NewReader(file).WriteTo(&w); err != nil {
 		panic(err)
@@ -54,11 +63,11 @@ func getFileContent(file *os.File) string {
 }
 
 func (rfs *rootFs) CreateServerFile(p string, c []byte) error {
-	f, err := os.Create(filepath.Join(rfs.root, "/server", p))
+	f, err := os.Create(filepath.Join(rfs.root, "server", p))
 
 	if err == nil {
-		f.Write(c)
+		_, _ = f.Write(c)
-		f.Close()
+		_ = f.Close()
 	}
 
 	return err
@@ -69,19 +78,7 @@ func (rfs *rootFs) CreateServerFileFromString(p string, c string) error {
 }
 
 func (rfs *rootFs) StatServerFile(p string) (os.FileInfo, error) {
-	return os.Stat(filepath.Join(rfs.root, "/server", p))
+	return os.Stat(filepath.Join(rfs.root, "server", p))
-}
-
-func (rfs *rootFs) reset() {
-	if err := os.RemoveAll(filepath.Join(rfs.root, "/server")); err != nil {
-		if !os.IsNotExist(err) {
-			panic(err)
-		}
-	}
-
-	if err := os.Mkdir(filepath.Join(rfs.root, "/server"), 0o755); err != nil {
-		panic(err)
-	}
 }
 
 func TestFilesystem_Openfile(t *testing.T) {
@@ -93,7 +90,8 @@ func TestFilesystem_Openfile(t *testing.T) {
 			_, _, err := fs.File("foo/bar.txt")
 
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrNotExist)).IsTrue()
+			// TODO
+			//g.Assert(IsErrorCode(err, ErrNotExist)).IsTrue()
 		})
 
 		g.It("returns file stat information", func() {
@@ -108,14 +106,14 @@ func TestFilesystem_Openfile(t *testing.T) {
 		})
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
 		})
 	})
 }
 
 func TestFilesystem_Writefile(t *testing.T) {
 	g := Goblin(t)
-	fs, rfs := NewFs()
+	fs, _ := NewFs()
 
 	g.Describe("Open and WriteFile", func() {
 		buf := &bytes.Buffer{}
@@ -125,22 +123,22 @@ func TestFilesystem_Writefile(t *testing.T) {
 		g.It("can create a new file", func() {
 			r := bytes.NewReader([]byte("test file content"))
 
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(int64(0))
+			g.Assert(fs.CachedUsage()).Equal(int64(0))
 
-			err := fs.Writefile("test.txt", r)
+			err := fs.Write("test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			f, _, err := fs.File("test.txt")
 			g.Assert(err).IsNil()
 			defer f.Close()
 			g.Assert(getFileContent(f)).Equal("test file content")
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(r.Size())
+			g.Assert(fs.CachedUsage()).Equal(r.Size())
 		})
 
 		g.It("can create a new file inside a nested directory with leading slash", func() {
 			r := bytes.NewReader([]byte("test file content"))
 
-			err := fs.Writefile("/some/nested/test.txt", r)
+			err := fs.Write("/some/nested/test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			f, _, err := fs.File("/some/nested/test.txt")
@@ -152,7 +150,7 @@ func TestFilesystem_Writefile(t *testing.T) {
 		g.It("can create a new file inside a nested directory without a trailing slash", func() {
 			r := bytes.NewReader([]byte("test file content"))
 
-			err := fs.Writefile("some/../foo/bar/test.txt", r)
+			err := fs.Write("some/../foo/bar/test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			f, _, err := fs.File("foo/bar/test.txt")
@@ -164,13 +162,13 @@ func TestFilesystem_Writefile(t *testing.T) {
 		g.It("cannot create a file outside the root directory", func() {
 			r := bytes.NewReader([]byte("test file content"))
 
-			err := fs.Writefile("/some/../foo/../../test.txt", r)
+			err := fs.Write("/some/../foo/../../test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("cannot write a file that exceeds the disk limits", func() {
-			atomic.StoreInt64(&fs.diskLimit, 1024)
+			fs.SetDiskLimit(1024)
 
 			b := make([]byte, 1025)
 			_, err := rand.Read(b)
@@ -178,18 +176,18 @@ func TestFilesystem_Writefile(t *testing.T) {
 			g.Assert(len(b)).Equal(1025)
 
 			r := bytes.NewReader(b)
-			err = fs.Writefile("test.txt", r)
+			err = fs.Write("test.txt", r, int64(len(b)), 0o644)
 			g.Assert(err).IsNotNil()
 			g.Assert(IsErrorCode(err, ErrCodeDiskSpace)).IsTrue()
 		})
 
 		g.It("truncates the file when writing new contents", func() {
 			r := bytes.NewReader([]byte("original data"))
-			err := fs.Writefile("test.txt", r)
+			err := fs.Write("test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			r = bytes.NewReader([]byte("new data"))
-			err = fs.Writefile("test.txt", r)
+			err = fs.Write("test.txt", r, r.Size(), 0o644)
 			g.Assert(err).IsNil()
 
 			f, _, err := fs.File("test.txt")
@@ -200,10 +198,7 @@ func TestFilesystem_Writefile(t *testing.T) {
 
 		g.AfterEach(func() {
 			buf.Truncate(0)
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
-
-			atomic.StoreInt64(&fs.diskUsed, 0)
-			atomic.StoreInt64(&fs.diskLimit, 0)
 		})
 	})
 }
@@ -236,17 +231,17 @@ func TestFilesystem_CreateDirectory(t *testing.T) {
 		g.It("should not allow the creation of directories outside the root", func() {
 			err := fs.CreateDirectory("test", "e/../../something")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("should not increment the disk usage", func() {
 			err := fs.CreateDirectory("test", "/")
 			g.Assert(err).IsNil()
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(int64(0))
+			g.Assert(fs.CachedUsage()).Equal(int64(0))
 		})
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
 		})
 	})
 }
@@ -268,25 +263,25 @@ func TestFilesystem_Rename(t *testing.T) {
 
 			err = fs.Rename("source.txt", "target.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrExist)).IsTrue("err is not ErrExist")
 		})
 
 		g.It("returns an error if the final destination is the root directory", func() {
 			err := fs.Rename("source.txt", "/")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("returns an error if the source destination is the root directory", func() {
-			err := fs.Rename("source.txt", "/")
+			err := fs.Rename("/", "target.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("does not allow renaming to a location outside the root", func() {
 			err := fs.Rename("source.txt", "../target.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("does not allow renaming from a location outside the root", func() {
@@ -294,7 +289,7 @@ func TestFilesystem_Rename(t *testing.T) {
 
 			err = fs.Rename("/../ext-source.txt", "target.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("allows a file to be renamed", func() {
@@ -303,7 +298,7 @@ func TestFilesystem_Rename(t *testing.T) {
 
 			_, err = rfs.StatServerFile("source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 
 			st, err := rfs.StatServerFile("target.txt")
 			g.Assert(err).IsNil()
@@ -320,7 +315,7 @@ func TestFilesystem_Rename(t *testing.T) {
 
 			_, err = rfs.StatServerFile("source_dir")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 
 			st, err := rfs.StatServerFile("target_dir")
 			g.Assert(err).IsNil()
@@ -330,7 +325,7 @@ func TestFilesystem_Rename(t *testing.T) {
 		g.It("returns an error if the source does not exist", func() {
 			err := fs.Rename("missing.txt", "target.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 		})
 
 		g.It("creates directories if they are missing", func() {
@@ -343,7 +338,7 @@ func TestFilesystem_Rename(t *testing.T) {
 		})
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
 		})
 	})
 }
@@ -358,13 +353,13 @@ func TestFilesystem_Copy(t *testing.T) {
 				panic(err)
 			}
 
-			atomic.StoreInt64(&fs.diskUsed, int64(utf8.RuneCountInString("test content")))
+			fs.unixFS.SetUsage(int64(utf8.RuneCountInString("test content")))
 		})
 
 		g.It("should return an error if the source does not exist", func() {
 			err := fs.Copy("foo.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 		})
 
 		g.It("should return an error if the source is outside the root", func() {
@@ -372,11 +367,11 @@ func TestFilesystem_Copy(t *testing.T) {
 
 			err = fs.Copy("../ext-source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("should return an error if the source directory is outside the root", func() {
-			err := os.MkdirAll(filepath.Join(rfs.root, "/nested/in/dir"), 0o755)
+			err := os.MkdirAll(filepath.Join(rfs.root, "nested/in/dir"), 0o755)
 			g.Assert(err).IsNil()
 
 			err = rfs.CreateServerFileFromString("/../nested/in/dir/ext-source.txt", "external content")
@@ -384,28 +379,28 @@ func TestFilesystem_Copy(t *testing.T) {
 
 			err = fs.Copy("../nested/in/dir/ext-source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 
 			err = fs.Copy("nested/in/../../../nested/in/dir/ext-source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("should return an error if the source is a directory", func() {
-			err := os.Mkdir(filepath.Join(rfs.root, "/server/dir"), 0o755)
+			err := os.Mkdir(filepath.Join(rfs.root, "server/dir"), 0o755)
 			g.Assert(err).IsNil()
 
 			err = fs.Copy("dir")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 		})
 
 		g.It("should return an error if there is not space to copy the file", func() {
-			atomic.StoreInt64(&fs.diskLimit, 2)
+			fs.SetDiskLimit(2)
 
 			err := fs.Copy("source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodeDiskSpace)).IsTrue()
+			g.Assert(IsErrorCode(err, ErrCodeDiskSpace)).IsTrue("err is not ErrCodeDiskSpace")
 		})
 
 		g.It("should create a copy of the file and increment the disk used", func() {
@@ -433,7 +428,7 @@ func TestFilesystem_Copy(t *testing.T) {
 				g.Assert(err).IsNil()
 			}
 
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(int64(utf8.RuneCountInString("test content")) * 3)
+			g.Assert(fs.CachedUsage()).Equal(int64(utf8.RuneCountInString("test content")) * 3)
 		})
 
 		g.It("should create a copy inside of a directory", func() {
@@ -454,10 +449,7 @@ func TestFilesystem_Copy(t *testing.T) {
 		})
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
-
-			atomic.StoreInt64(&fs.diskUsed, 0)
-			atomic.StoreInt64(&fs.diskLimit, 0)
 		})
 	})
 }
@@ -472,7 +464,7 @@ func TestFilesystem_Delete(t *testing.T) {
 				panic(err)
 			}
 
-			atomic.StoreInt64(&fs.diskUsed, int64(utf8.RuneCountInString("test content")))
+			fs.unixFS.SetUsage(int64(utf8.RuneCountInString("test content")))
 		})
 
 		g.It("does not delete files outside the root directory", func() {
@@ -480,13 +472,13 @@ func TestFilesystem_Delete(t *testing.T) {
 
 			err = fs.Delete("../ext-source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("does not allow the deletion of the root directory", func() {
 			err := fs.Delete("/")
 			g.Assert(err).IsNotNil()
-			g.Assert(err.Error()).Equal("cannot delete root server directory")
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("does not return an error if the target does not exist", func() {
@@ -504,9 +496,9 @@ func TestFilesystem_Delete(t *testing.T) {
 
 			_, err = rfs.StatServerFile("source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(int64(0))
+			g.Assert(fs.CachedUsage()).Equal(int64(0))
 		})
 
 		g.It("deletes all items inside a directory if the directory is deleted", func() {
@@ -524,16 +516,16 @@ func TestFilesystem_Delete(t *testing.T) {
 				g.Assert(err).IsNil()
 			}
 
-			atomic.StoreInt64(&fs.diskUsed, int64(utf8.RuneCountInString("test content")*3))
+			fs.unixFS.SetUsage(int64(utf8.RuneCountInString("test content") * 3))
 
 			err = fs.Delete("foo")
 			g.Assert(err).IsNil()
-			g.Assert(atomic.LoadInt64(&fs.diskUsed)).Equal(int64(0))
+			g.Assert(fs.unixFS.Usage()).Equal(int64(0))
 
 			for _, s := range sources {
 				_, err = rfs.StatServerFile(s)
 				g.Assert(err).IsNotNil()
-				g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+				g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 			}
 		})
 
@@ -589,7 +581,7 @@ func TestFilesystem_Delete(t *testing.T) {
 			// Delete a file inside the symlinked directory.
 			err = fs.Delete("symlink/source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 
 			// Ensure the file outside the root directory still exists.
 			_, err = os.Lstat(filepath.Join(rfs.root, "foo/source.txt"))
@@ -608,14 +600,11 @@ func TestFilesystem_Delete(t *testing.T) {
 			// Delete a file inside the symlinked directory.
 			err = fs.Delete("symlink/source.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.AfterEach(func() {
-			rfs.reset()
+			_ = fs.TruncateRootDirectory()
-
-			atomic.StoreInt64(&fs.diskUsed, 0)
-			atomic.StoreInt64(&fs.diskLimit, 0)
 		})
 	})
 }

server/filesystem/path.go

@@ -1,71 +1,28 @@
 package filesystem
 
 import (
-	"context"
-	iofs "io/fs"
-	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 
 	"emperror.dev/errors"
-	"golang.org/x/sync/errgroup"
 )
 
 // Checks if the given file or path is in the server's file denylist. If so, an Error
 // is returned, otherwise nil is returned.
 func (fs *Filesystem) IsIgnored(paths ...string) error {
 	for _, p := range paths {
-		sp, err := fs.SafePath(p)
+		//sp, err := fs.SafePath(p)
-		if err != nil {
+		//if err != nil {
-			return err
+		//	return err
-		}
+		//}
-		if fs.denylist.MatchesPath(sp) {
+		// TODO: update logic to use unixFS
-			return errors.WithStack(&Error{code: ErrCodeDenylistFile, path: p, resolved: sp})
+		if fs.denylist.MatchesPath(p) {
+			return errors.WithStack(&Error{code: ErrCodeDenylistFile, path: p, resolved: p})
 		}
 	}
 	return nil
 }
 
-// Normalizes a directory being passed in to ensure the user is not able to escape
-// from their data directory. After normalization if the directory is still within their home
-// path it is returned. If they managed to "escape" an error will be returned.
-//
-// This logic is actually copied over from the SFTP server code. Ideally that eventually
-// either gets ported into this application, or is able to make use of this package.
-func (fs *Filesystem) SafePath(p string) (string, error) {
-	// Start with a cleaned up path before checking the more complex bits.
-	r := fs.unsafeFilePath(p)
-
-	// At the same time, evaluate the symlink status and determine where this file or folder
-	// is truly pointing to.
-	ep, err := filepath.EvalSymlinks(r)
-	if err != nil && !os.IsNotExist(err) {
-		return "", errors.Wrap(err, "server/filesystem: failed to evaluate symlink")
-	} else if os.IsNotExist(err) {
-		// The target of one of the symlinks (EvalSymlinks is recursive) does not exist.
-		// So we get what target path does not exist and check if it's within the data
-		// directory. If it is, we return the original path, otherwise we return an error.
-		pErr, ok := err.(*iofs.PathError)
-		if !ok {
-			return "", errors.Wrap(err, "server/filesystem: failed to evaluate symlink")
-		}
-		ep = pErr.Path
-	}
-
-	// If the requested directory from EvalSymlinks begins with the server root directory go
-	// ahead and return it. If not we'll return an error which will block any further action
-	// on the file.
-	if fs.unsafeIsInDataDirectory(ep) {
-		// Returning the original path here instead of the resolved path ensures that
-		// whatever the user is trying to do will work as expected. If we returned the
-		// resolved path, the user would be unable to know that it is in fact a symlink.
-		return r, nil
-	}
-
-	return "", NewBadPathResolution(p, r)
-}
-
 // Generate a path to the file by cleaning it up and appending the root server path to it. This
 // DOES NOT guarantee that the file resolves within the server data directory. You'll want to use
 // the fs.unsafeIsInDataDirectory(p) function to confirm.
@@ -84,51 +41,3 @@ func (fs *Filesystem) unsafeFilePath(p string) string {
 func (fs *Filesystem) unsafeIsInDataDirectory(p string) bool {
 	return strings.HasPrefix(strings.TrimSuffix(p, "/")+"/", strings.TrimSuffix(fs.Path(), "/")+"/")
 }
-
-// Executes the fs.SafePath function in parallel against an array of paths. If any of the calls
-// fails an error will be returned.
-func (fs *Filesystem) ParallelSafePath(paths []string) ([]string, error) {
-	var cleaned []string
-
-	// Simple locker function to avoid racy appends to the array of cleaned paths.
-	m := new(sync.Mutex)
-	push := func(c string) {
-		m.Lock()
-		cleaned = append(cleaned, c)
-		m.Unlock()
-	}
-
-	// Create an error group that we can use to run processes in parallel while retaining
-	// the ability to cancel the entire process immediately should any of it fail.
-	g, ctx := errgroup.WithContext(context.Background())
-
-	// Iterate over all of the paths and generate a cleaned path, if there is an error for any
-	// of the files, abort the process.
-	for _, p := range paths {
-		// Create copy so we can use it within the goroutine correctly.
-		pi := p
-
-		// Recursively call this function to continue digging through the directory tree within
-		// a separate goroutine. If the context is canceled abort this process.
-		g.Go(func() error {
-			select {
-			case <-ctx.Done():
-				return ctx.Err()
-			default:
-				// If the callback returns true, go ahead and keep walking deeper. This allows
-				// us to programmatically continue deeper into directories, or stop digging
-				// if that pathway knows it needs nothing else.
-				if c, err := fs.SafePath(pi); err != nil {
-					return err
-				} else {
-					push(c)
-				}
-
-				return nil
-			}
-		})
-	}
-
-	// Block until all of the routines finish and have returned a value.
-	return cleaned, g.Wait()
-}

server/filesystem/path_test.go

@@ -8,6 +8,8 @@ import (
 
 	"emperror.dev/errors"
 	. "github.com/franela/goblin"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 func TestFilesystem_Path(t *testing.T) {
@@ -21,80 +23,6 @@ func TestFilesystem_Path(t *testing.T) {
 	})
 }
 
-func TestFilesystem_SafePath(t *testing.T) {
-	g := Goblin(t)
-	fs, rfs := NewFs()
-	prefix := filepath.Join(rfs.root, "/server")
-
-	g.Describe("SafePath", func() {
-		g.It("returns a cleaned path to a given file", func() {
-			p, err := fs.SafePath("test.txt")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/test.txt")
-
-			p, err = fs.SafePath("/test.txt")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/test.txt")
-
-			p, err = fs.SafePath("./test.txt")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/test.txt")
-
-			p, err = fs.SafePath("/foo/../test.txt")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/test.txt")
-
-			p, err = fs.SafePath("/foo/bar")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/foo/bar")
-		})
-
-		g.It("handles root directory access", func() {
-			p, err := fs.SafePath("/")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix)
-
-			p, err = fs.SafePath("")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix)
-		})
-
-		g.It("removes trailing slashes from paths", func() {
-			p, err := fs.SafePath("/foo/bar/")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/foo/bar")
-		})
-
-		g.It("handles deeply nested directories that do not exist", func() {
-			p, err := fs.SafePath("/foo/bar/baz/quaz/../../ducks/testing.txt")
-			g.Assert(err).IsNil()
-			g.Assert(p).Equal(prefix + "/foo/bar/ducks/testing.txt")
-		})
-
-		g.It("blocks access to files outside the root directory", func() {
-			p, err := fs.SafePath("../test.txt")
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
-			g.Assert(p).Equal("")
-
-			p, err = fs.SafePath("/../test.txt")
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
-			g.Assert(p).Equal("")
-
-			p, err = fs.SafePath("./foo/../../test.txt")
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
-			g.Assert(p).Equal("")
-
-			p, err = fs.SafePath("..")
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
-			g.Assert(p).Equal("")
-		})
-	})
-}
-
 // We test against accessing files outside the root directory in the tests, however it
 // is still possible for someone to mess up and not properly use this safe path call. In
 // order to truly confirm this, we'll try to pass in a symlinked malicious file to all of
@@ -133,7 +61,7 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 
 			err := fs.Writefile("symlinked.txt", r)
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("cannot write to a non-existent file symlinked outside the root", func() {
@@ -141,7 +69,7 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 
 			err := fs.Writefile("symlinked_does_not_exist.txt", r)
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("cannot write to chained symlinks with target that does not exist outside the root", func() {
@@ -149,7 +77,7 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 
 			err := fs.Writefile("symlinked_does_not_exist2.txt", r)
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrBadPathResolution)).IsTrue("err is not ErrBadPathResolution")
 		})
 
 		g.It("cannot write a file to a directory symlinked outside the root", func() {
@@ -157,7 +85,7 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 
 			err := fs.Writefile("external_dir/foo.txt", r)
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotDirectory)).IsTrue("err is not ErrNotDirectory")
 		})
 	})
 
@@ -165,55 +93,54 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 		g.It("cannot create a directory outside the root", func() {
 			err := fs.CreateDirectory("my_dir", "external_dir")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotDirectory)).IsTrue("err is not ErrNotDirectory")
 		})
 
 		g.It("cannot create a nested directory outside the root", func() {
 			err := fs.CreateDirectory("my/nested/dir", "external_dir/foo/bar")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotDirectory)).IsTrue("err is not ErrNotDirectory")
 		})
 
 		g.It("cannot create a nested directory outside the root", func() {
 			err := fs.CreateDirectory("my/nested/dir", "external_dir/server")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotDirectory)).IsTrue("err is not ErrNotDirectory")
 		})
 	})
 
 	g.Describe("Rename", func() {
-		g.It("cannot rename a file symlinked outside the directory root", func() {
+		g.It("can rename a file symlinked outside the directory root", func() {
-			err := fs.Rename("symlinked.txt", "foo.txt")
+			_, err := os.Lstat(filepath.Join(rfs.root, "server", "symlinked.txt"))
-			g.Assert(err).IsNotNil()
+			g.Assert(err).IsNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			err = fs.Rename("symlinked.txt", "foo.txt")
+			g.Assert(err).IsNil()
+			_, err = os.Lstat(filepath.Join(rfs.root, "server", "foo.txt"))
+			g.Assert(err).IsNil()
 		})
 
-		g.It("cannot rename a symlinked directory outside the root", func() {
+		g.It("can rename a symlinked directory outside the root", func() {
-			err := fs.Rename("external_dir", "foo")
+			_, err := os.Lstat(filepath.Join(rfs.root, "server", "external_dir"))
-			g.Assert(err).IsNotNil()
+			g.Assert(err).IsNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			err = fs.Rename("external_dir", "foo")
+			g.Assert(err).IsNil()
+			_, err = os.Lstat(filepath.Join(rfs.root, "server", "foo"))
+			g.Assert(err).IsNil()
 		})
 
 		g.It("cannot rename a file to a location outside the directory root", func() {
-			rfs.CreateServerFileFromString("my_file.txt", "internal content")
+			_ = rfs.CreateServerFileFromString("my_file.txt", "internal content")
+			t.Log(rfs.root)
 
-			err := fs.Rename("my_file.txt", "external_dir/my_file.txt")
+			st, err := os.Lstat(filepath.Join(rfs.root, "server", "foo"))
-			g.Assert(err).IsNotNil()
+			g.Assert(err).IsNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(st.Mode()&ufs.ModeSymlink != 0).IsTrue()
-		})
-	})
 
-	g.Describe("Chown", func() {
+			err = fs.Rename("my_file.txt", "foo/my_file.txt")
-		g.It("cannot chown a file symlinked outside the directory root", func() {
+			g.Assert(errors.Is(err, ufs.ErrNotDirectory)).IsTrue()
-			err := fs.Chown("symlinked.txt")
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
-		})
 
-		g.It("cannot chown a directory symlinked outside the directory root", func() {
+			st, err = os.Lstat(filepath.Join(rfs.root, "malicious_dir", "my_file.txt"))
-			err := fs.Chown("external_dir")
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue()
-			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
 		})
 	})
 
@@ -221,7 +148,7 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 		g.It("cannot copy a file symlinked outside the directory root", func() {
 			err := fs.Copy("symlinked.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(IsErrorCode(err, ErrCodePathResolution)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 		})
 	})
 
@@ -235,9 +162,9 @@ func TestFilesystem_Blocks_Symlinks(t *testing.T) {
 
 			_, err = rfs.StatServerFile("symlinked.txt")
 			g.Assert(err).IsNotNil()
-			g.Assert(errors.Is(err, os.ErrNotExist)).IsTrue()
+			g.Assert(errors.Is(err, ufs.ErrNotExist)).IsTrue("err is not ErrNotExist")
 		})
 	})
 
-	rfs.reset()
+	_ = fs.TruncateRootDirectory()
 }

server/filesystem/stat.go

@@ -1,16 +1,18 @@
 package filesystem
 
 import (
-	"os"
+	"encoding/json"
+	"io"
 	"strconv"
 	"time"
 
 	"github.com/gabriel-vasile/mimetype"
-	"github.com/goccy/go-json"
+
+	"github.com/pterodactyl/wings/internal/ufs"
 )
 
 type Stat struct {
-	os.FileInfo
+	ufs.FileInfo
 	Mimetype string
 }
 
@@ -31,40 +33,31 @@ func (s *Stat) MarshalJSON() ([]byte, error) {
 		Created:  s.CTime().Format(time.RFC3339),
 		Modified: s.ModTime().Format(time.RFC3339),
 		Mode:     s.Mode().String(),
-		// Using `&os.ModePerm` on the file's mode will cause the mode to only have the permission values, and nothing else.
+		// Using `&ModePerm` on the file's mode will cause the mode to only have the permission values, and nothing else.
-		ModeBits:  strconv.FormatUint(uint64(s.Mode()&os.ModePerm), 8),
+		ModeBits:  strconv.FormatUint(uint64(s.Mode()&ufs.ModePerm), 8),
 		Size:      s.Size(),
 		Directory: s.IsDir(),
 		File:      !s.IsDir(),
-		Symlink:   s.Mode().Perm()&os.ModeSymlink != 0,
+		Symlink:   s.Mode().Perm()&ufs.ModeSymlink != 0,
 		Mime:      s.Mimetype,
 	})
 }
 
-// Stat stats a file or folder and returns the base stat object from go along
+func statFromFile(f ufs.File) (Stat, error) {
-// with the MIME data that can be used for editing files.
+	s, err := f.Stat()
-func (fs *Filesystem) Stat(p string) (Stat, error) {
-	cleaned, err := fs.SafePath(p)
 	if err != nil {
 		return Stat{}, err
 	}
-	return fs.unsafeStat(cleaned)
-}
-
-func (fs *Filesystem) unsafeStat(p string) (Stat, error) {
-	s, err := os.Stat(p)
-	if err != nil {
-		return Stat{}, err
-	}
-
 	var m *mimetype.MIME
 	if !s.IsDir() {
-		m, err = mimetype.DetectFile(p)
+		m, err = mimetype.DetectReader(f)
 		if err != nil {
 			return Stat{}, err
 		}
+		if _, err := f.Seek(0, io.SeekStart); err != nil {
+			return Stat{}, err
+		}
 	}
-
 	st := Stat{
 		FileInfo: s,
 		Mimetype: "inode/directory",
@@ -72,6 +65,20 @@ func (fs *Filesystem) unsafeStat(p string) (Stat, error) {
 	if m != nil {
 		st.Mimetype = m.String()
 	}
-
+	return st, nil
+}
+
+// Stat stats a file or folder and returns the base stat object from go along
+// with the MIME data that can be used for editing files.
+func (fs *Filesystem) Stat(p string) (Stat, error) {
+	f, err := fs.unixFS.Open(p)
+	if err != nil {
+		return Stat{}, err
+	}
+	defer f.Close()
+	st, err := statFromFile(f)
+	if err != nil {
+		return Stat{}, err
+	}
 	return st, nil
 }

server/filesystem/stat_darwin.go

@@ -1,13 +0,0 @@
-package filesystem
-
-import (
-	"syscall"
-	"time"
-)
-
-// CTime returns the time that the file/folder was created.
-func (s *Stat) CTime() time.Time {
-	st := s.Sys().(*syscall.Stat_t)
-
-	return time.Unix(st.Ctimespec.Sec, st.Ctimespec.Nsec)
-}

server/filesystem/stat_linux.go

@@ -3,12 +3,22 @@ package filesystem
 import (
 	"syscall"
 	"time"
+
+	"golang.org/x/sys/unix"
 )
 
-// Returns the time that the file/folder was created.
+// CTime returns the time that the file/folder was created.
+//
+// TODO: remove. Ctim is not actually ever been correct and doesn't actually
+// return the creation time.
 func (s *Stat) CTime() time.Time {
-	st := s.Sys().(*syscall.Stat_t)
+	if st, ok := s.Sys().(*unix.Stat_t); ok {
-
 		// Do not remove these "redundant" type-casts, they are required for 32-bit builds to work.
 		return time.Unix(int64(st.Ctim.Sec), int64(st.Ctim.Nsec))
 	}
+	if st, ok := s.Sys().(*syscall.Stat_t); ok {
+		// Do not remove these "redundant" type-casts, they are required for 32-bit builds to work.
+		return time.Unix(int64(st.Ctim.Sec), int64(st.Ctim.Nsec))
+	}
+	return time.Time{}
+}

server/filesystem/stat_windows.go

@@ -1,12 +0,0 @@
-package filesystem
-
-import (
-	"time"
-)
-
-// On linux systems this will return the time that the file was created.
-// However, I have no idea how to do this on windows, so we're skipping it
-// for right now.
-func (s *Stat) CTime() time.Time {
-	return s.ModTime()
-}

server/install.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"bufio"
-	"bytes"
 	"context"
 	"html/template"
 	"io"
@@ -218,30 +217,18 @@ func (ip *InstallationProcess) tempDir() string {
 // can be properly mounted into the installation container and then executed.
 func (ip *InstallationProcess) writeScriptToDisk() error {
 	// Make sure the temp directory root exists before trying to make a directory within it. The
-	// ioutil.TempDir call expects this base to exist, it won't create it for you.
+	// os.TempDir call expects this base to exist, it won't create it for you.
 	if err := os.MkdirAll(ip.tempDir(), 0o700); err != nil {
 		return errors.WithMessage(err, "could not create temporary directory for install process")
 	}
-
 	f, err := os.OpenFile(filepath.Join(ip.tempDir(), "install.sh"), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o644)
 	if err != nil {
 		return errors.WithMessage(err, "failed to write server installation script to disk before mount")
 	}
 	defer f.Close()
-
+	if _, err := io.Copy(f, strings.NewReader(strings.ReplaceAll(ip.Script.Script, "\r\n", "\n"))); err != nil {
-	w := bufio.NewWriter(f)
-
-	scanner := bufio.NewScanner(bytes.NewReader([]byte(ip.Script.Script)))
-	for scanner.Scan() {
-		w.WriteString(scanner.Text() + "\n")
-	}
-
-	if err := scanner.Err(); err != nil {
 		return err
 	}
-
-	w.Flush()
-
 	return nil
 }
 

server/manager.go

@@ -196,7 +196,10 @@ func (m *Manager) InitServer(data remote.ServerConfigurationResponse) (*Server,
 		return nil, errors.WithStackIf(err)
 	}
 
-	s.fs = filesystem.New(filepath.Join(config.Get().System.Data, s.ID()), s.DiskSpace(), s.Config().Egg.FileDenylist)
+	s.fs, err = filesystem.New(filepath.Join(config.Get().System.Data, s.ID()), s.DiskSpace(), s.Config().Egg.FileDenylist)
+	if err != nil {
+		return nil, errors.WithStackIf(err)
+	}
 
 	// Right now we only support a Docker based environment, so I'm going to hard code
 	// this logic in. When we're ready to support other environment we'll need to make

server/transfer/archive.go

@@ -35,7 +35,7 @@ type Archive struct {
 func NewArchive(t *Transfer, size uint64) *Archive {
 	return &Archive{
 		archive: &filesystem.Archive{
-			BasePath: t.Server.Filesystem().Path(),
+			Filesystem: t.Server.Filesystem(),
 			Progress:   progress.NewProgress(size),
 		},
 	}

sftp/handler.go

@@ -2,7 +2,6 @@ package sftp
 
 import (
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -122,7 +121,7 @@ func (h *Handler) Filewrite(request *sftp.Request) (io.WriterAt, error) {
 	if !h.can(permission) {
 		return nil, sftp.ErrSSHFxPermissionDenied
 	}
-	f, err := h.fs.Touch(request.Filepath, os.O_RDWR|os.O_CREATE|os.O_TRUNC)
+	f, err := h.fs.Touch(request.Filepath, os.O_RDWR|os.O_TRUNC)
 	if err != nil {
 		l.WithField("flags", request.Flags).WithField("error", err).Error("failed to open existing file on system")
 		return nil, sftp.ErrSSHFxFailure
@@ -220,16 +219,8 @@ func (h *Handler) Filecmd(request *sftp.Request) error {
 		if !h.can(PermissionFileCreate) {
 			return sftp.ErrSSHFxPermissionDenied
 		}
-		source, err := h.fs.SafePath(request.Filepath)
+		if err := h.fs.Symlink(request.Filepath, request.Target); err != nil {
-		if err != nil {
+			l.WithField("target", request.Target).WithField("error", err).Error("failed to create symlink")
-			return sftp.ErrSSHFxNoSuchFile
-		}
-		target, err := h.fs.SafePath(request.Target)
-		if err != nil {
-			return sftp.ErrSSHFxNoSuchFile
-		}
-		if err := os.Symlink(source, target); err != nil {
-			l.WithField("target", target).WithField("error", err).Error("failed to create symlink")
 			return sftp.ErrSSHFxFailure
 		}
 		break
@@ -274,16 +265,12 @@ func (h *Handler) Filelist(request *sftp.Request) (sftp.ListerAt, error) {
 
 	switch request.Method {
 	case "List":
-		p, err := h.fs.SafePath(request.Filepath)
+		entries, err := h.fs.ReadDirStat(request.Filepath)
-		if err != nil {
-			return nil, sftp.ErrSSHFxNoSuchFile
-		}
-		files, err := ioutil.ReadDir(p)
 		if err != nil {
 			h.logger.WithField("source", request.Filepath).WithField("error", err).Error("error while listing directory")
 			return nil, sftp.ErrSSHFxFailure
 		}
-		return ListerAt(files), nil
+		return ListerAt(entries), nil
 	case "Stat":
 		st, err := h.fs.Stat(request.Filepath)
 		if err != nil {