382 lines
11 KiB
Go
382 lines
11 KiB
Go
package pathfs_frontend
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// FUSE operations on paths
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import (
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"encoding/base64"
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"os"
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"path/filepath"
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"sync"
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"syscall"
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"time"
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"github.com/hanwen/go-fuse/fuse"
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"github.com/hanwen/go-fuse/fuse/nodefs"
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"github.com/hanwen/go-fuse/fuse/pathfs"
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"github.com/rfjakob/gocryptfs/internal/toggledlog"
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"github.com/rfjakob/gocryptfs/internal/cryptocore"
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"github.com/rfjakob/gocryptfs/internal/nametransform"
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"github.com/rfjakob/gocryptfs/internal/contentenc"
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"github.com/rfjakob/gocryptfs/internal/configfile"
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)
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const plainBS = 4096
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type FS struct {
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pathfs.FileSystem // loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
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args Args // Stores configuration arguments
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// dirIVLock: Lock()ed if any "gocryptfs.diriv" file is modified
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// Readers must RLock() it to prevent them from seeing intermediate
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// states
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dirIVLock sync.RWMutex
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// Filename encryption helper
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nameTransform *nametransform.NameTransform
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// Content encryption helper
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contentEnc *contentenc.ContentEnc
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}
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// Encrypted FUSE overlay filesystem
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func NewFS(args Args) *FS {
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cryptoCore := cryptocore.New(args.Masterkey, args.OpenSSL, args.GCMIV128)
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contentEnc := contentenc.New(cryptoCore, plainBS)
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nameTransform := nametransform.New(cryptoCore, args.EMENames)
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return &FS{
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FileSystem: pathfs.NewLoopbackFileSystem(args.Cipherdir),
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args: args,
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nameTransform: nameTransform,
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contentEnc: contentEnc,
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}
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}
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// GetBackingPath - get the absolute encrypted path of the backing file
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// from the relative plaintext path "relPath"
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func (fs *FS) getBackingPath(relPath string) (string, error) {
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cPath, err := fs.encryptPath(relPath)
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if err != nil {
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return "", err
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}
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cAbsPath := filepath.Join(fs.args.Cipherdir, cPath)
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toggledlog.Debug.Printf("getBackingPath: %s + %s -> %s", fs.args.Cipherdir, relPath, cAbsPath)
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return cAbsPath, nil
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}
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func (fs *FS) GetAttr(name string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
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toggledlog.Debug.Printf("FS.GetAttr('%s')", name)
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if fs.isFiltered(name) {
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return nil, fuse.EPERM
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}
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cName, err := fs.encryptPath(name)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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a, status := fs.FileSystem.GetAttr(cName, context)
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if a == nil {
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toggledlog.Debug.Printf("FS.GetAttr failed: %s", status.String())
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return a, status
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}
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if a.IsRegular() {
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a.Size = fs.contentEnc.CipherSizeToPlainSize(a.Size)
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} else if a.IsSymlink() {
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target, _ := fs.Readlink(name, context)
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a.Size = uint64(len(target))
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}
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return a, status
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}
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func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
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toggledlog.Debug.Printf("OpenDir(%s)", dirName)
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cDirName, err := fs.encryptPath(dirName)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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// Read ciphertext directory
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cipherEntries, status := fs.FileSystem.OpenDir(cDirName, context)
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if cipherEntries == nil {
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return nil, status
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}
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// Get DirIV (stays nil if DirIV if off)
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var cachedIV []byte
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if fs.args.DirIV {
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// Read the DirIV once and use it for all later name decryptions
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cDirAbsPath := filepath.Join(fs.args.Cipherdir, cDirName)
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cachedIV, err = fs.nameTransform.ReadDirIV(cDirAbsPath)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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}
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// Filter and decrypt filenames
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var plain []fuse.DirEntry
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for i := range cipherEntries {
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cName := cipherEntries[i].Name
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if dirName == "" && cName == configfile.ConfDefaultName {
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// silently ignore "gocryptfs.conf" in the top level dir
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continue
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}
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if fs.args.DirIV && cName == nametransform.DirIVFilename {
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// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
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continue
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}
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var name string = cName
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if !fs.args.PlaintextNames {
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name, err = fs.nameTransform.DecryptName(cName, cachedIV)
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if err != nil {
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toggledlog.Warn.Printf("Invalid name \"%s\" in dir \"%s\": %s", cName, cDirName, err)
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continue
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}
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}
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cipherEntries[i].Name = name
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plain = append(plain, cipherEntries[i])
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}
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return plain, status
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}
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// We always need read access to do read-modify-write cycles
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func (fs *FS) mangleOpenFlags(flags uint32) (newFlags int, writeOnly bool) {
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newFlags = int(flags)
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if newFlags&os.O_WRONLY > 0 {
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writeOnly = true
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newFlags = newFlags ^ os.O_WRONLY | os.O_RDWR
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}
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// We also cannot open the file in append mode, we need to seek back for RMW
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newFlags = newFlags &^ os.O_APPEND
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return newFlags, writeOnly
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}
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func (fs *FS) Open(path string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
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if fs.isFiltered(path) {
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return nil, fuse.EPERM
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}
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iflags, writeOnly := fs.mangleOpenFlags(flags)
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cPath, err := fs.getBackingPath(path)
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if err != nil {
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toggledlog.Debug.Printf("Open: getBackingPath: %v", err)
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return nil, fuse.ToStatus(err)
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}
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toggledlog.Debug.Printf("Open: %s", cPath)
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f, err := os.OpenFile(cPath, iflags, 0666)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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return NewFile(f, writeOnly, fs.contentEnc), fuse.OK
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}
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func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Context) (fuseFile nodefs.File, code fuse.Status) {
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if fs.isFiltered(path) {
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return nil, fuse.EPERM
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}
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iflags, writeOnly := fs.mangleOpenFlags(flags)
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cPath, err := fs.getBackingPath(path)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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f, err := os.OpenFile(cPath, iflags|os.O_CREATE, os.FileMode(mode))
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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return NewFile(f, writeOnly, fs.contentEnc), fuse.OK
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}
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func (fs *FS) Chmod(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.encryptPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fs.FileSystem.Chmod(cPath, mode, context)
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}
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func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.encryptPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fs.FileSystem.Chown(cPath, uid, gid, context)
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}
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func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.encryptPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fs.FileSystem.Mknod(cPath, mode, dev, context)
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}
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var truncateWarned bool
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func (fs *FS) Truncate(path string, offset uint64, context *fuse.Context) (code fuse.Status) {
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// Only warn once
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if !truncateWarned {
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toggledlog.Warn.Printf("truncate(2) is not supported, returning ENOSYS - use ftruncate(2)")
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truncateWarned = true
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}
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return fuse.ENOSYS
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}
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func (fs *FS) Utimens(path string, Atime *time.Time, Mtime *time.Time, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.encryptPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fs.FileSystem.Utimens(cPath, Atime, Mtime, context)
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}
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func (fs *FS) Readlink(path string, context *fuse.Context) (out string, status fuse.Status) {
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cPath, err := fs.encryptPath(path)
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if err != nil {
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return "", fuse.ToStatus(err)
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}
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cTarget, status := fs.FileSystem.Readlink(cPath, context)
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if status != fuse.OK {
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return "", status
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}
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// Old filesystem: symlinks are encrypted like paths (CBC)
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if !fs.args.DirIV {
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target, err := fs.decryptPath(cTarget)
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if err != nil {
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toggledlog.Warn.Printf("Readlink: CBC decryption failed: %v", err)
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return "", fuse.EIO
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}
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return target, fuse.OK
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}
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// Since gocryptfs v0.5 symlinks are encrypted like file contents (GCM)
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cBinTarget, err := base64.URLEncoding.DecodeString(cTarget)
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if err != nil {
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toggledlog.Warn.Printf("Readlink: %v", err)
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return "", fuse.EIO
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}
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target, err := fs.contentEnc.DecryptBlock([]byte(cBinTarget), 0, nil)
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if err != nil {
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toggledlog.Warn.Printf("Readlink: %v", err)
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return "", fuse.EIO
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}
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return string(target), fuse.OK
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}
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func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.getBackingPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fuse.ToStatus(syscall.Unlink(cPath))
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}
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func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (code fuse.Status) {
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toggledlog.Debug.Printf("Symlink(\"%s\", \"%s\")", target, linkName)
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if fs.isFiltered(linkName) {
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return fuse.EPERM
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}
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cPath, err := fs.getBackingPath(linkName)
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if err != nil {
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return fuse.ToStatus(err)
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}
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// Old filesystem: symlinks are encrypted like paths (CBC)
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if !fs.args.DirIV {
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cTarget, err := fs.encryptPath(target)
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if err != nil {
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toggledlog.Warn.Printf("Symlink: BUG: we should not get an error here: %v", err)
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return fuse.ToStatus(err)
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}
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err = os.Symlink(cTarget, cPath)
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return fuse.ToStatus(err)
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}
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// Since gocryptfs v0.5 symlinks are encrypted like file contents (GCM)
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cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil)
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cTarget := base64.URLEncoding.EncodeToString(cBinTarget)
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err = os.Symlink(cTarget, cPath)
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toggledlog.Debug.Printf("Symlink: os.Symlink(%s, %s) = %v", cTarget, cPath, err)
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return fuse.ToStatus(err)
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}
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func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(newPath) {
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return fuse.EPERM
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}
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cOldPath, err := fs.getBackingPath(oldPath)
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if err != nil {
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return fuse.ToStatus(err)
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}
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cNewPath, err := fs.getBackingPath(newPath)
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if err != nil {
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return fuse.ToStatus(err)
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}
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// The Rename may cause a directory to take the place of another directory.
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// That directory may still be in the DirIV cache, clear it.
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fs.nameTransform.DirIVCache.Clear()
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err = os.Rename(cOldPath, cNewPath)
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if lerr, ok := err.(*os.LinkError); ok && lerr.Err == syscall.ENOTEMPTY {
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// If an empty directory is overwritten we will always get
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// ENOTEMPTY as the "empty" directory will still contain gocryptfs.diriv.
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// Handle that case by removing the target directory and trying again.
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toggledlog.Debug.Printf("Rename: Handling ENOTEMPTY")
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if fs.Rmdir(newPath, context) == fuse.OK {
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err = os.Rename(cOldPath, cNewPath)
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}
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}
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return fuse.ToStatus(err)
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}
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func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(newPath) {
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return fuse.EPERM
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}
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cOldPath, err := fs.getBackingPath(oldPath)
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if err != nil {
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return fuse.ToStatus(err)
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}
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cNewPath, err := fs.getBackingPath(newPath)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fuse.ToStatus(os.Link(cOldPath, cNewPath))
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}
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func (fs *FS) Access(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
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if fs.isFiltered(path) {
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return fuse.EPERM
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}
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cPath, err := fs.getBackingPath(path)
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if err != nil {
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return fuse.ToStatus(err)
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}
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return fuse.ToStatus(syscall.Access(cPath, mode))
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}
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func (fs *FS) GetXAttr(name string, attr string, context *fuse.Context) ([]byte, fuse.Status) {
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return nil, fuse.ENOSYS
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}
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func (fs *FS) SetXAttr(name string, attr string, data []byte, flags int, context *fuse.Context) fuse.Status {
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return fuse.ENOSYS
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}
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func (fs *FS) ListXAttr(name string, context *fuse.Context) ([]string, fuse.Status) {
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return nil, fuse.ENOSYS
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}
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func (fs *FS) RemoveXAttr(name string, attr string, context *fuse.Context) fuse.Status {
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return fuse.ENOSYS
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}
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