package fusefrontend import ( "context" "fmt" "io" "path/filepath" "runtime" "syscall" "golang.org/x/sys/unix" "github.com/hanwen/go-fuse/v2/fs" "github.com/hanwen/go-fuse/v2/fuse" "github.com/rfjakob/gocryptfs/internal/configfile" "github.com/rfjakob/gocryptfs/internal/cryptocore" "github.com/rfjakob/gocryptfs/internal/nametransform" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) // mkdirWithIv - create a new directory and corresponding diriv file. dirfd // should be a handle to the parent directory, cName is the name of the new // directory and mode specifies the access permissions to use. func (n *Node) mkdirWithIv(dirfd int, cName string, mode uint32, caller *fuse.Caller) error { rn := n.rootNode() // Between the creation of the directory and the creation of gocryptfs.diriv // the directory is inconsistent. Take the lock to prevent other readers // from seeing it. rn.dirIVLock.Lock() defer rn.dirIVLock.Unlock() err := syscallcompat.MkdiratUser(dirfd, cName, mode, caller) if err != nil { return err } dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_DIRECTORY|syscall.O_NOFOLLOW|syscallcompat.O_PATH, 0) if err == nil { // Create gocryptfs.diriv err = nametransform.WriteDirIVAt(dirfd2) syscall.Close(dirfd2) } if err != nil { // Delete inconsistent directory (missing gocryptfs.diriv!) err2 := syscallcompat.Unlinkat(dirfd, cName, unix.AT_REMOVEDIR) if err2 != nil { tlog.Warn.Printf("mkdirWithIv: rollback failed: %v", err2) } } return err } // Mkdir - FUSE call. Create a directory at "newPath" with permissions "mode". // // Symlink-safe through use of Mkdirat(). func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.EntryOut) (*fs.Inode, syscall.Errno) { rn := n.rootNode() newPath := filepath.Join(n.path(), name) if rn.isFiltered(newPath) { return nil, syscall.EPERM } dirfd, cName, err := rn.openBackingDir(newPath) if err != nil { return nil, fs.ToErrno(err) } defer syscall.Close(dirfd) var caller *fuse.Caller if rn.args.PreserveOwner { caller, _ = fuse.FromContext(ctx) } if rn.args.PlaintextNames { err = syscallcompat.MkdiratUser(dirfd, cName, mode, caller) return nil, fs.ToErrno(err) } // We need write and execute permissions to create gocryptfs.diriv. // Also, we need read permissions to open the directory (to avoid // race-conditions between getting and setting the mode). origMode := mode mode = mode | 0700 // Handle long file name if nametransform.IsLongContent(cName) { // Create ".name" err = rn.nameTransform.WriteLongNameAt(dirfd, cName, newPath) if err != nil { return nil, fs.ToErrno(err) } // Create directory err = rn.mkdirWithIv(dirfd, cName, mode, caller) if err != nil { nametransform.DeleteLongNameAt(dirfd, cName) return nil, fs.ToErrno(err) } } else { err = rn.mkdirWithIv(dirfd, cName, mode, caller) if err != nil { return nil, fs.ToErrno(err) } } fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0) if err != nil { tlog.Warn.Printf("Mkdir %q: Openat failed: %v", cName, err) return nil, fs.ToErrno(err) } defer syscall.Close(fd) // Get unique inode number var st syscall.Stat_t err = syscall.Fstat(fd, &st) if err != nil { tlog.Warn.Printf("Mkdir %q: Fstat failed: %v", cName, err) return nil, fs.ToErrno(err) } // Create child node ch := n.newChild(ctx, &st, out) // Set mode if origMode != mode { // Preserve SGID bit if it was set due to inheritance. origMode = uint32(st.Mode&^0777) | origMode err = syscall.Fchmod(fd, origMode) if err != nil { tlog.Warn.Printf("Mkdir %q: Fchmod %#o -> %#o failed: %v", cName, mode, origMode, err) } } return ch, 0 } // Readdir - FUSE call. // // This function is symlink-safe through use of openBackingDir() and // ReadDirIVAt(). func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) { rn := n.rootNode() p := n.path() dirName := filepath.Base(p) parentDirFd, cDirName, err := rn.openBackingDir(p) if err != nil { return nil, fs.ToErrno(err) } defer syscall.Close(parentDirFd) // Read ciphertext directory var cipherEntries []fuse.DirEntry fd, err := syscallcompat.Openat(parentDirFd, cDirName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0) if err != nil { return nil, fs.ToErrno(err) } defer syscall.Close(fd) cipherEntries, err = syscallcompat.Getdents(fd) if err != nil { return nil, fs.ToErrno(err) } // Get DirIV (stays nil if PlaintextNames is used) var cachedIV []byte if !rn.args.PlaintextNames { // Read the DirIV from disk cachedIV, err = nametransform.ReadDirIVAt(fd) if err != nil { tlog.Warn.Printf("OpenDir %q: could not read %s: %v", cDirName, nametransform.DirIVFilename, err) return nil, syscall.EIO } } // Decrypted directory entries var plain []fuse.DirEntry // Filter and decrypt filenames for i := range cipherEntries { cName := cipherEntries[i].Name if dirName == "." && cName == configfile.ConfDefaultName { // silently ignore "gocryptfs.conf" in the top level dir continue } if rn.args.PlaintextNames { plain = append(plain, cipherEntries[i]) continue } if cName == nametransform.DirIVFilename { // silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled continue } // Handle long file name isLong := nametransform.LongNameNone if rn.args.LongNames { isLong = nametransform.NameType(cName) } if isLong == nametransform.LongNameContent { cNameLong, err := nametransform.ReadLongNameAt(fd, cName) if err != nil { tlog.Warn.Printf("OpenDir %q: invalid entry %q: Could not read .name: %v", cDirName, cName, err) rn.reportMitigatedCorruption(cName) continue } cName = cNameLong } else if isLong == nametransform.LongNameFilename { // ignore "gocryptfs.longname.*.name" continue } name, err := rn.nameTransform.DecryptName(cName, cachedIV) if err != nil { tlog.Warn.Printf("OpenDir %q: invalid entry %q: %v", cDirName, cName, err) rn.reportMitigatedCorruption(cName) continue } // Override the ciphertext name with the plaintext name but reuse the rest // of the structure cipherEntries[i].Name = name plain = append(plain, cipherEntries[i]) } return fs.NewListDirStream(plain), 0 } // Rmdir - FUSE call. // // Symlink-safe through Unlinkat() + AT_REMOVEDIR. func (n *Node) Rmdir(ctx context.Context, name string) (code syscall.Errno) { rn := n.rootNode() p := filepath.Join(n.path(), name) parentDirFd, cName, err := rn.openBackingDir(p) if err != nil { return fs.ToErrno(err) } defer syscall.Close(parentDirFd) if rn.args.PlaintextNames { // Unlinkat with AT_REMOVEDIR is equivalent to Rmdir err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR) return fs.ToErrno(err) } // Unless we are running as root, we need read, write and execute permissions // to handle gocryptfs.diriv. permWorkaround := false var origMode uint32 if !rn.args.PreserveOwner { var st unix.Stat_t err = syscallcompat.Fstatat(parentDirFd, cName, &st, unix.AT_SYMLINK_NOFOLLOW) if err != nil { return fs.ToErrno(err) } if st.Mode&0700 != 0700 { tlog.Debug.Printf("Rmdir: permWorkaround") permWorkaround = true // This cast is needed on Darwin, where st.Mode is uint16. origMode = uint32(st.Mode) err = syscallcompat.FchmodatNofollow(parentDirFd, cName, origMode|0700) if err != nil { tlog.Debug.Printf("Rmdir: permWorkaround: chmod failed: %v", err) return fs.ToErrno(err) } } } dirfd, err := syscallcompat.Openat(parentDirFd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0) if err != nil { tlog.Debug.Printf("Rmdir: Open: %v", err) return fs.ToErrno(err) } defer syscall.Close(dirfd) // Undo the chmod if removing the directory failed. This must run before // closing dirfd, so defer it after (defer is LIFO). if permWorkaround { defer func() { if code != 0 { err = unix.Fchmod(dirfd, origMode) if err != nil { tlog.Warn.Printf("Rmdir: permWorkaround: rollback failed: %v", err) } } }() } retry: // Check directory contents children, err := syscallcompat.Getdents(dirfd) if err == io.EOF { // The directory is empty tlog.Warn.Printf("Rmdir: %q: %s is missing", cName, nametransform.DirIVFilename) err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR) return fs.ToErrno(err) } if err != nil { tlog.Warn.Printf("Rmdir: Readdirnames: %v", err) return fs.ToErrno(err) } // MacOS sprinkles .DS_Store files everywhere. This is hard to avoid for // users, so handle it transparently here. if runtime.GOOS == "darwin" && len(children) <= 2 && haveDsstore(children) { err = unix.Unlinkat(dirfd, dsStoreName, 0) if err != nil { tlog.Warn.Printf("Rmdir: failed to delete blocking file %q: %v", dsStoreName, err) return fs.ToErrno(err) } tlog.Warn.Printf("Rmdir: had to delete blocking file %q", dsStoreName) goto retry } // If the directory is not empty besides gocryptfs.diriv, do not even // attempt the dance around gocryptfs.diriv. if len(children) > 1 { return fs.ToErrno(syscall.ENOTEMPTY) } // Move "gocryptfs.diriv" to the parent dir as "gocryptfs.diriv.rmdir.XYZ" tmpName := fmt.Sprintf("%s.rmdir.%d", nametransform.DirIVFilename, cryptocore.RandUint64()) tlog.Debug.Printf("Rmdir: Renaming %s to %s", nametransform.DirIVFilename, tmpName) // The directory is in an inconsistent state between rename and rmdir. // Protect against concurrent readers. rn.dirIVLock.Lock() defer rn.dirIVLock.Unlock() err = syscallcompat.Renameat(dirfd, nametransform.DirIVFilename, parentDirFd, tmpName) if err != nil { tlog.Warn.Printf("Rmdir: Renaming %s to %s failed: %v", nametransform.DirIVFilename, tmpName, err) return fs.ToErrno(err) } // Actual Rmdir err = syscallcompat.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR) if err != nil { // This can happen if another file in the directory was created in the // meantime, undo the rename err2 := syscallcompat.Renameat(parentDirFd, tmpName, dirfd, nametransform.DirIVFilename) if err2 != nil { tlog.Warn.Printf("Rmdir: Rename rollback failed: %v", err2) } return fs.ToErrno(err) } // Delete "gocryptfs.diriv.rmdir.XYZ" err = syscallcompat.Unlinkat(parentDirFd, tmpName, 0) if err != nil { tlog.Warn.Printf("Rmdir: Could not clean up %s: %v", tmpName, err) } // Delete .name file if nametransform.IsLongContent(cName) { nametransform.DeleteLongNameAt(parentDirFd, cName) } return 0 } // Opendir is a FUSE call to check if the directory can be opened. func (n *Node) Opendir(ctx context.Context) (errno syscall.Errno) { dirfd, cName, errno := n.prepareAtSyscall("") if errno != 0 { return } defer syscall.Close(dirfd) // Open backing directory fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0) if err != nil { return fs.ToErrno(err) } syscall.Close(fd) return 0 }