Add FS logic for determining folder size as well as safe path resolution

go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/onsi/gomega v1.5.0 // indirect
 	github.com/opencontainers/go-digest v1.0.0-rc1 // indirect
 	github.com/opencontainers/image-spec v1.0.1 // indirect
+	github.com/patrickmn/go-cache v2.1.0+incompatible
 	github.com/pkg/errors v0.8.0
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/remeh/sizedwaitgroup v0.0.0-20180822144253-5e7302b12cce

go.sum

@@ -44,6 +44,8 @@ github.com/opencontainers/go-digest v1.0.0-rc1 h1:WzifXhOVOEOuFYOJAW6aQqW0TooG2i
 github.com/opencontainers/go-digest v1.0.0-rc1/go.mod h1:cMLVZDEM3+U2I4VmLI6N8jQYUd2OVphdqWwCJHrFt2s=
 github.com/opencontainers/image-spec v1.0.1 h1:JMemWkRwHx4Zj+fVxWoMCFm/8sYGGrUVojFA6h/TRcI=
 github.com/opencontainers/image-spec v1.0.1/go.mod h1:BtxoFyWECRxE4U/7sNtV5W15zMzWCbyJoFRP3s7yZA0=
+github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
+github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
 github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

server/filesystem.go

@@ -1,6 +1,18 @@
 package server
 
-import "path"
+import (
+	"errors"
+	"go.uber.org/zap"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Error returned when there is a bad path provided to one of the FS calls.
+var InvalidPathResolution = errors.New("invalid path resolution")
 
 type Filesystem struct {
 	// The root directory where all of the server data is contained. By default
@@ -13,10 +25,146 @@ type Filesystem struct {
 
 // Returns the root path that contains all of a server's data.
 func (fs *Filesystem) Path() string {
-	return path.Join(fs.Root, fs.Server.Uuid)
+	return filepath.Join(fs.Root, fs.Server.Uuid)
 }
 
-// Returns a safe path for a server object.
-func (fs *Filesystem) SafePath(p string) string {
-	return fs.Path()
+// 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) {
+	var nonExistentPathResolution string
+
+	// Calling filpath.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.
+	r := filepath.Clean(filepath.Join(fs.Path(), p))
+
+	// At the same time, evaluate the symlink status and determine where this file or folder
+	// is truly pointing to.
+	p, err := filepath.EvalSymlinks(r)
+	if err != nil && !os.IsNotExist(err) {
+		return "", err
+	} else if os.IsNotExist(err) {
+		// The requested 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(r), "/")
+
+		var try string
+		// Range over all of the path parts and form directory pathings 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 !strings.HasPrefix(try, fs.Path()) {
+				break
+			}
+
+			t, err := filepath.EvalSymlinks(try)
+			if err == nil {
+				nonExistentPathResolution = t
+				break
+			}
+		}
+	}
+
+	// If the new path doesn't start with their root directory there is clearly an escape
+	// attempt going on, and we should NOT resolve this path for them.
+	if nonExistentPathResolution != "" {
+		if !strings.HasPrefix(nonExistentPathResolution, fs.Path()) {
+			return "", InvalidPathResolution
+		}
+
+		// If the nonExistentPathResoltion variable is not empty then the initial path requested
+		// did not exist and we looped through the pathway until we found a match. At this point
+		// we've confirmed the first matched pathway exists in the root server directory, so we
+		// can go ahead and just return the path that was requested initially.
+		return r, nil
+	}
+
+	// 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 strings.HasPrefix(p, fs.Path()) {
+		return p, nil
+	}
+
+	return "", InvalidPathResolution
+}
+
+// Determines if the directory a file is trying to be added to has enough space available
+// for the file to be written to.
+//
+// Because determining the amount of space being used by a server is a taxing operation we
+// will load it all up into a cache and pull from that as long as the key is not expired.
+func (fs *Filesystem) HasSpaceAvailable() bool {
+	var space = fs.Server.Build.DiskSpace
+
+	// If space is -1 or 0 just return true, means they're allowed unlimited.
+	if space <= 0 {
+		return true
+	}
+
+	var size int64
+	if x, exists := fs.Server.Cache().Get("disk_used"); exists {
+		size = x.(int64)
+	}
+
+	// If there is no size its either because there is no data (in which case running this function
+	// will have effectively no impact), or there is nothing in the cache, in which case we need to
+	// grab the size of their data directory. This is a taxing operation, so we want to store it in
+	// the cache once we've gotten it.
+	if size == 0 {
+		if size, err := fs.DirectorySize("/"); err != nil {
+			zap.S().Warnw("failed to determine directory size", zap.String("server", fs.Server.Uuid), zap.Error(err))
+		} else {
+			fs.Server.Cache().Set("disk_used", size, time.Minute * 5)
+		}
+	}
+
+	// Determine if their folder size, in bytes, is smaller than the amount of space they've
+	// been allocated.
+	return (size / 1024.0 / 1024.0) <= space
+}
+
+// Determines the directory size of a given location by running parallel tasks to iterate
+// through all of the folders. Returns the size in bytes. This can be a fairly taxing operation
+// on locations with tons of files, so it is recommended that you cache the output.
+func (fs *Filesystem) DirectorySize(dir string) (int64, error) {
+	var size int64
+	var wg sync.WaitGroup
+
+	cleaned, err := fs.SafePath(dir)
+	if err != nil {
+		return 0, err
+	}
+
+	files, err := ioutil.ReadDir(cleaned)
+	if err != nil {
+		return 0, err
+	}
+
+	// Iterate over all of the files and directories. If it is a file, immediately add its size
+	// to the total size being returned. If we're dealing with a directory, call this function
+	// on a seperate thread until we have gotten the size of everything nested within the given
+	// directory.
+	for _, f := range files {
+		if f.IsDir() {
+			wg.Add(1)
+
+			go func(p string) {
+				defer wg.Done()
+
+				s, _ := fs.DirectorySize(p)
+				size += s
+			}(filepath.Join(cleaned, f.Name()))
+		} else {
+			size += f.Size()
+		}
+	}
+
+	wg.Wait()
+
+	return size, nil
 }

server/server.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"github.com/patrickmn/go-cache"
 	"github.com/pterodactyl/wings/config"
 	"github.com/remeh/sizedwaitgroup"
 	"go.uber.org/zap"
@@ -9,6 +10,7 @@ import (
 	"os"
 	"path"
 	"strings"
+	"time"
 )
 
 // High level definition for a server instance being controlled by Wings.
@@ -43,6 +45,10 @@ type Server struct {
 	environment Environment
 
 	fs *Filesystem
+
+	// Server cache used to store frequently requested information in memory and make
+	// certain long operations return faster. For example, FS disk space usage.
+	cache *cache.Cache
 }
 
 // The build settings for a given server that impact docker container creation and
@@ -187,7 +193,7 @@ func FromConfiguration(data []byte, cfg *config.SystemConfiguration) (*Server, e
 	}
 
 	s.environment = env
-
+	s.cache = cache.New(time.Minute * 10, time.Minute * 15)
 	s.fs = &Filesystem{
 		Root:   cfg.Data,
 		Server: s,
@@ -209,6 +215,10 @@ func (s *Server) Filesystem() *Filesystem {
 	return s.fs
 }
 
+func (s *Server) Cache() *cache.Cache {
+	return s.cache
+}
+
 // Determine if the server is bootable in it's current state or not. This will not
 // indicate why a server is not bootable, only if it is.
 func (s *Server) IsBootable() bool {