wings/server/filesystem/errors.go

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package filesystem
import (
"fmt"
"os"
"path/filepath"
"strings"
"emperror.dev/errors"
"github.com/apex/log"
)
type ErrorCode string
const (
ErrCodeIsDirectory ErrorCode = "E_ISDIR"
ErrCodeDiskSpace ErrorCode = "E_NODISK"
ErrCodeUnknownArchive ErrorCode = "E_UNKNFMT"
ErrCodePathResolution ErrorCode = "E_BADPATH"
ErrCodeDenylistFile ErrorCode = "E_DENYLIST"
ErrCodeUnknownError ErrorCode = "E_UNKNOWN"
)
type Error struct {
code ErrorCode
// Contains the underlying error leading to this. This value may or may not be
// present, it is entirely dependent on how this error was triggered.
err error
// This contains the value of the final destination that triggered this specific
// error event.
resolved string
// This value is generally only present on errors stemming from a path resolution
// error. For everything else you should be setting and reading the resolved path
// value which will be far more useful.
path string
}
// newFilesystemError returns a new error instance with a stack trace associated.
func newFilesystemError(code ErrorCode, err error) error {
if err != nil {
return errors.WithStackDepth(&Error{code: code, err: err}, 1)
}
return errors.WithStackDepth(&Error{code: code}, 1)
}
// Code returns the ErrorCode for this specific error instance.
func (e *Error) Code() ErrorCode {
return e.code
}
// Returns a human-readable error string to identify the Error by.
func (e *Error) Error() string {
switch e.code {
case ErrCodeIsDirectory:
return fmt.Sprintf("filesystem: cannot perform action: [%s] is a directory", e.resolved)
case ErrCodeDiskSpace:
return "filesystem: not enough disk space"
case ErrCodeUnknownArchive:
return "filesystem: unknown archive format"
case ErrCodeDenylistFile:
r := e.resolved
if r == "" {
r = "<empty>"
}
return fmt.Sprintf("filesystem: file access prohibited: [%s] is on the denylist", r)
case ErrCodePathResolution:
r := e.resolved
if r == "" {
r = "<empty>"
}
return fmt.Sprintf("filesystem: server path [%s] resolves to a location outside the server root: %s", e.path, r)
case ErrCodeUnknownError:
fallthrough
default:
return fmt.Sprintf("filesystem: an error occurred: %s", e.Unwrap())
}
}
// Unwrap returns the underlying cause of this filesystem error. In some causes
// there may not be a cause present, in which case nil will be returned.
func (e *Error) Unwrap() error {
return e.err
}
// 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)
}
// 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.
func (fs *Filesystem) handleWalkerError(err error, f os.FileInfo) error {
if !IsErrorCode(err, ErrCodePathResolution) {
return err
}
if f != nil && f.IsDir() {
return filepath.SkipDir
}
return nil
}
// IsFilesystemError checks if the given error is one of the Filesystem errors.
func IsFilesystemError(err error) bool {
var fserr *Error
if err != nil && errors.As(err, &fserr) {
return true
}
return false
}
// IsErrorCode checks if "err" is a filesystem Error type. If so, it will then
// drop in and check that the error code is the same as the provided ErrorCode
// passed in "code".
func IsErrorCode(err error, code ErrorCode) bool {
var fserr *Error
if err != nil && errors.As(err, &fserr) {
return fserr.code == code
}
return false
}
// IsUnknownArchiveFormatError checks if the error is due to the archive being
// in an unexpected file format.
func IsUnknownArchiveFormatError(err error) bool {
if err != nil && strings.HasPrefix(err.Error(), "format ") {
return true
}
return false
}
// NewBadPathResolution returns a new BadPathResolution error.
func NewBadPathResolution(path string, resolved string) error {
return errors.WithStackDepth(&Error{code: ErrCodePathResolution, path: path, resolved: resolved}, 1)
}
// wrapError wraps the provided error as a Filesystem error and attaches the
// provided resolved source to it. If the error is already a Filesystem error
// no action is taken.
func wrapError(err error, resolved string) error {
if err == nil || IsFilesystemError(err) {
return err
}
return errors.WithStackDepth(&Error{code: ErrCodeUnknownError, err: err, resolved: resolved}, 1)
}