package fusefrontend // FUSE operations on file handles import ( "bytes" "fmt" "io" "log" "os" "sync" "syscall" "time" "github.com/hanwen/go-fuse/fuse" "github.com/hanwen/go-fuse/fuse/nodefs" "github.com/rfjakob/gocryptfs/internal/contentenc" "github.com/rfjakob/gocryptfs/internal/tlog" ) // File - based on loopbackFile in go-fuse/fuse/nodefs/files.go type file struct { fd *os.File // Has Release() already been called on this file? This also means that the // wlock entry has been freed, so let's not crash trying to access it. // Due to concurrency, Release can overtake other operations. These will // return EBADF in that case. released bool // fdLock prevents the fd to be closed while we are in the middle of // an operation. // Every FUSE entrypoint should RLock(). The only user of Lock() is // Release(), which closes the fd and sets "released" to true. fdLock sync.RWMutex // Was the file opened O_WRONLY? writeOnly bool // Content encryption helper contentEnc *contentenc.ContentEnc // Inode number ino uint64 // File header header *contentenc.FileHeader } func NewFile(fd *os.File, writeOnly bool, contentEnc *contentenc.ContentEnc) (nodefs.File, fuse.Status) { var st syscall.Stat_t err := syscall.Fstat(int(fd.Fd()), &st) if err != nil { tlog.Warn.Printf("NewFile: Fstat on fd %d failed: %v\n", fd.Fd(), err) return nil, fuse.ToStatus(err) } wlock.register(st.Ino) return &file{ fd: fd, writeOnly: writeOnly, contentEnc: contentEnc, ino: st.Ino, }, fuse.OK } // intFd - return the backing file descriptor as an integer. Used for debug // messages. func (f *file) intFd() int { return int(f.fd.Fd()) } func (f *file) InnerFile() nodefs.File { return nil } func (f *file) SetInode(n *nodefs.Inode) { } // readHeader - load the file header from disk // // Returns io.EOF if the file is empty func (f *file) readHeader() error { buf := make([]byte, contentenc.HEADER_LEN) _, err := f.fd.ReadAt(buf, 0) if err != nil { return err } h, err := contentenc.ParseHeader(buf) if err != nil { return err } f.header = h return nil } // createHeader - create a new random header and write it to disk func (f *file) createHeader() error { h := contentenc.RandomHeader() buf := h.Pack() // Prevent partially written (=corrupt) header by preallocating the space beforehand err := prealloc(int(f.fd.Fd()), 0, contentenc.HEADER_LEN) if err != nil { tlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.ino, err.Error()) return err } // Actually write header _, err = f.fd.WriteAt(buf, 0) if err != nil { return err } f.header = h return nil } func (f *file) String() string { return fmt.Sprintf("cryptFile(%s)", f.fd.Name()) } // doRead - returns "length" plaintext bytes from plaintext offset "off". // Arguments "length" and "off" do not have to be block-aligned. // // doRead reads the corresponding ciphertext blocks from disk, decrypts them and // returns the requested part of the plaintext. // // Called by Read() for normal reading, // by Write() and Truncate() for Read-Modify-Write func (f *file) doRead(off uint64, length uint64) ([]byte, fuse.Status) { // Read file header if f.header == nil { err := f.readHeader() if err == io.EOF { return nil, fuse.OK } if err != nil { return nil, fuse.ToStatus(err) } } // Read the backing ciphertext in one go blocks := f.contentEnc.ExplodePlainRange(off, length) alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks) skip := blocks[0].Skip tlog.Debug.Printf("JointCiphertextRange(%d, %d) -> %d, %d, %d", off, length, alignedOffset, alignedLength, skip) ciphertext := make([]byte, int(alignedLength)) n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset)) if err != nil && err != io.EOF { tlog.Warn.Printf("read: ReadAt: %s", err.Error()) return nil, fuse.ToStatus(err) } // Truncate ciphertext buffer down to actually read bytes ciphertext = ciphertext[0:n] firstBlockNo := blocks[0].BlockNo tlog.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d", alignedOffset, firstBlockNo, alignedLength, n) // Decrypt it plaintext, err := f.contentEnc.DecryptBlocks(ciphertext, firstBlockNo, f.header.Id) if err != nil { curruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext))) cipherOff := f.contentEnc.BlockNoToCipherOff(curruptBlockNo) plainOff := f.contentEnc.BlockNoToPlainOff(curruptBlockNo) tlog.Warn.Printf("ino%d: doRead: corrupt block #%d (plainOff=%d, cipherOff=%d)", f.ino, curruptBlockNo, plainOff, cipherOff) return nil, fuse.EIO } // Crop down to the relevant part var out []byte lenHave := len(plaintext) lenWant := int(skip + length) if lenHave > lenWant { out = plaintext[skip:lenWant] } else if lenHave > int(skip) { out = plaintext[skip:lenHave] } // else: out stays empty, file was smaller than the requested offset return out, fuse.OK } // Read - FUSE call func (f *file) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fuse.Status) { f.fdLock.RLock() defer f.fdLock.RUnlock() tlog.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.ino, len(buf), off) if f.writeOnly { tlog.Warn.Printf("ino%d: Tried to read from write-only file", f.ino) return nil, fuse.EBADF } out, status := f.doRead(uint64(off), uint64(len(buf))) if status == fuse.EIO { tlog.Warn.Printf("ino%d: Read failed with EIO, offset=%d, length=%d", f.ino, len(buf), off) } if status != fuse.OK { return nil, status } tlog.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.ino, status, len(out)) return fuse.ReadResultData(out), status } const FALLOC_FL_KEEP_SIZE = 0x01 // doWrite - encrypt "data" and write it to plaintext offset "off" // // Arguments do not have to be block-aligned, read-modify-write is // performed internally as neccessary // // Called by Write() for normal writing, // and by Truncate() to rewrite the last file block. // // Empty writes do nothing and are allowed. func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) { // Read header from disk, create a new one if the file is empty if f.header == nil { err := f.readHeader() if err == io.EOF { err = f.createHeader() } if err != nil { return 0, fuse.ToStatus(err) } } var written uint32 status := fuse.OK dataBuf := bytes.NewBuffer(data) blocks := f.contentEnc.ExplodePlainRange(uint64(off), uint64(len(data))) for _, b := range blocks { blockData := dataBuf.Next(int(b.Length)) // Incomplete block -> Read-Modify-Write if b.IsPartial() { // Read o := b.BlockPlainOff() var oldData []byte oldData, status = f.doRead(o, f.contentEnc.PlainBS()) if status != fuse.OK { tlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.ino, f.intFd(), status.String()) return written, status } // Modify blockData = f.contentEnc.MergeBlocks(oldData, blockData, int(b.Skip)) tlog.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData)) } // Encrypt blockOffset := b.BlockCipherOff() blockData = f.contentEnc.EncryptBlock(blockData, b.BlockNo, f.header.Id) tlog.Debug.Printf("ino%d: Writing %d bytes to block #%d", f.ino, uint64(len(blockData))-f.contentEnc.BlockOverhead(), b.BlockNo) // Prevent partially written (=corrupt) blocks by preallocating the space beforehand err := prealloc(int(f.fd.Fd()), int64(blockOffset), int64(len(blockData))) if err != nil { tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %s", f.ino, f.intFd(), err.Error()) status = fuse.ToStatus(err) break } // Write _, err = f.fd.WriteAt(blockData, int64(blockOffset)) if err != nil { tlog.Warn.Printf("doWrite: Write failed: %s", err.Error()) status = fuse.ToStatus(err) break } written += uint32(b.Length) } return written, status } // Write - FUSE call // // If the write creates a hole, pads the file to the next block boundary. func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) { f.fdLock.RLock() defer f.fdLock.RUnlock() if f.released { // The file descriptor has been closed concurrently, which also means // the wlock has been freed. Exit here so we don't crash trying to access // it. tlog.Warn.Printf("ino%d fh%d: Write on released file", f.ino, f.intFd()) return 0, fuse.EBADF } wlock.lock(f.ino) defer wlock.unlock(f.ino) tlog.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.ino, off, len(data)) fi, err := f.fd.Stat() if err != nil { tlog.Warn.Printf("Write: Fstat failed: %v", err) return 0, fuse.ToStatus(err) } plainSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size())) if f.createsHole(plainSize, off) { status := f.zeroPad(plainSize) if status != fuse.OK { tlog.Warn.Printf("zeroPad returned error %v", status) return 0, status } } return f.doWrite(data, off) } // Release - FUSE call, close file func (f *file) Release() { f.fdLock.Lock() if f.released { log.Panicf("ino%d fh%d: double release", f.ino, f.intFd()) } f.fd.Close() f.released = true f.fdLock.Unlock() wlock.unregister(f.ino) } // Flush - FUSE call func (f *file) Flush() fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() // Since Flush() may be called for each dup'd fd, we don't // want to really close the file, we just want to flush. This // is achieved by closing a dup'd fd. newFd, err := syscall.Dup(int(f.fd.Fd())) if err != nil { return fuse.ToStatus(err) } err = syscall.Close(newFd) return fuse.ToStatus(err) } func (f *file) Fsync(flags int) (code fuse.Status) { f.fdLock.RLock() defer f.fdLock.RUnlock() return fuse.ToStatus(syscall.Fsync(int(f.fd.Fd()))) } // Truncate - FUSE call func (f *file) Truncate(newSize uint64) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() if f.released { // The file descriptor has been closed concurrently. tlog.Warn.Printf("ino%d fh%d: Truncate on released file", f.ino, f.intFd()) return fuse.EBADF } wlock.lock(f.ino) defer wlock.unlock(f.ino) var err error // Common case first: Truncate to zero if newSize == 0 { err = syscall.Ftruncate(int(f.fd.Fd()), 0) if err != nil { tlog.Warn.Printf("ino%d fh%d: Ftruncate(fd, 0) returned error: %v", f.ino, f.intFd(), err) return fuse.ToStatus(err) } // Truncate to zero kills the file header f.header = nil return fuse.OK } // We need the old file size to determine if we are growing or shrinking // the file fi, err := f.fd.Stat() if err != nil { tlog.Warn.Printf("ino%d fh%d: Truncate: Fstat failed: %v", f.ino, f.intFd(), err) return fuse.ToStatus(err) } oldSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size())) { oldB := float32(oldSize) / float32(f.contentEnc.PlainBS()) newB := float32(newSize) / float32(f.contentEnc.PlainBS()) tlog.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)", f.ino, oldB, newB, oldSize, newSize) } // File size stays the same - nothing to do if newSize == oldSize { return fuse.OK } // File grows if newSize > oldSize { // File was empty, create new header if oldSize == 0 { err = f.createHeader() if err != nil { return fuse.ToStatus(err) } } // New blocks to add addBlocks := f.contentEnc.ExplodePlainRange(oldSize, newSize-oldSize) if len(addBlocks) >= 2 { f.zeroPad(oldSize) } lastBlock := addBlocks[len(addBlocks)-1] if lastBlock.IsPartial() { off := lastBlock.BlockPlainOff() _, status := f.doWrite(make([]byte, lastBlock.Length), int64(off+lastBlock.Skip)) return status } else { off := lastBlock.BlockCipherOff() err = syscall.Ftruncate(f.intFd(), int64(off+f.contentEnc.CipherBS())) if err != nil { tlog.Warn.Printf("Truncate: grow Ftruncate returned error: %v", err) } return fuse.ToStatus(err) } } else { // File shrinks blockNo := f.contentEnc.PlainOffToBlockNo(newSize) cipherOff := f.contentEnc.BlockNoToCipherOff(blockNo) plainOff := f.contentEnc.BlockNoToPlainOff(blockNo) lastBlockLen := newSize - plainOff var data []byte if lastBlockLen > 0 { var status fuse.Status data, status = f.doRead(plainOff, lastBlockLen) if status != fuse.OK { tlog.Warn.Printf("Truncate: shrink doRead returned error: %v", err) return status } } // Truncate down to the last complete block err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff)) if err != nil { tlog.Warn.Printf("Truncate: shrink Ftruncate returned error: %v", err) return fuse.ToStatus(err) } // Append partial block if lastBlockLen > 0 { _, status := f.doWrite(data, int64(plainOff)) return status } return fuse.OK } } func (f *file) Chmod(mode uint32) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() // os.File.Chmod goes through the "syscallMode" translation function that messes // up the suid and sgid bits. So use syscall.Fchmod directly. err := syscall.Fchmod(f.intFd(), mode) return fuse.ToStatus(err) } func (f *file) Chown(uid uint32, gid uint32) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() return fuse.ToStatus(f.fd.Chown(int(uid), int(gid))) } func (f *file) GetAttr(a *fuse.Attr) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() tlog.Debug.Printf("file.GetAttr()") st := syscall.Stat_t{} err := syscall.Fstat(int(f.fd.Fd()), &st) if err != nil { return fuse.ToStatus(err) } a.FromStat(&st) a.Size = f.contentEnc.CipherSizeToPlainSize(a.Size) return fuse.OK } // Only warn once var allocateWarnOnce sync.Once // Allocate - FUSE call, fallocate(2) // This is not implemented yet in gocryptfs, but it is neither in EncFS. This // suggests that the user demand is low. func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status { allocateWarnOnce.Do(func() { tlog.Warn.Printf("fallocate(2) is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1") }) return fuse.ENOSYS } const _UTIME_OMIT = ((1 << 30) - 2) func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() ts := make([]syscall.Timespec, 2) if a == nil { ts[0].Nsec = _UTIME_OMIT } else { ts[0].Sec = a.Unix() } if m == nil { ts[1].Nsec = _UTIME_OMIT } else { ts[1].Sec = m.Unix() } fn := fmt.Sprintf("/proc/self/fd/%d", f.fd.Fd()) err := syscall.UtimesNano(fn, ts) if err != nil { tlog.Debug.Printf("UtimesNano on %q failed: %v", fn, err) } if err == syscall.ENOENT { // If /proc/self/fd/X did not exist, the actual error is that the file // descriptor was invalid. return fuse.EBADF } return fuse.ToStatus(err) }