package pathfs_frontend // FUSE operations on file handles import ( "bytes" "fmt" "io" "os" "sync" "syscall" "time" "github.com/hanwen/go-fuse/fuse" "github.com/hanwen/go-fuse/fuse/nodefs" "github.com/rfjakob/gocryptfs/cryptfs" ) // File - based on loopbackFile in go-fuse/fuse/nodefs/files.go type file struct { fd *os.File // os.File is not threadsafe. Although fd themselves are // constant during the lifetime of an open file, the OS may // reuse the fd number after it is closed. When open races // with another close, they may lead to confusion as which // file gets written in the end. fdLock sync.Mutex // Was the file opened O_WRONLY? writeOnly bool // Parent CryptFS cfs *cryptfs.CryptFS // Inode number ino uint64 // File header header *cryptfs.FileHeader } func NewFile(fd *os.File, writeOnly bool, cfs *cryptfs.CryptFS) nodefs.File { var st syscall.Stat_t syscall.Fstat(int(fd.Fd()), &st) return &file{ fd: fd, writeOnly: writeOnly, cfs: cfs, ino: st.Ino, } } func (f *file) InnerFile() nodefs.File { return nil } func (f *file) SetInode(n *nodefs.Inode) { } // Ensure that all modifications to the file contents are serialized and no // reads happen concurrently. // // This prevents several races: // * getFileId vs Truncate // * zeroPad vs Read // * RMW vs Write func (f *file) wlock() { } func (f *file) rlock() { } func (f *file) unlock() { } // readHeader - load the file header from disk // // Returns io.EOF if the file is empty func (f *file) readHeader() error { buf := make([]byte, cryptfs.HEADER_LEN) _, err := f.fd.ReadAt(buf, 0) if err != nil { return err } h, err := cryptfs.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 := cryptfs.RandomHeader() buf := h.Pack() // Prevent partially written (=corrupt) header by preallocating the space beforehand f.fdLock.Lock() defer f.fdLock.Unlock() err := fallocateRetry(int(f.fd.Fd()), FALLOC_FL_KEEP_SIZE, 0, cryptfs.HEADER_LEN) if err != nil { cryptfs.Warn.Printf("createHeader: fallocateRetry failed: %s\n", 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.cfs.ExplodePlainRange(off, length) alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks) skip := blocks[0].Skip cryptfs.Debug.Printf("JointCiphertextRange(%d, %d) -> %d, %d, %d\n", off, length, alignedOffset, alignedLength, skip) ciphertext := make([]byte, int(alignedLength)) f.fdLock.Lock() n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset)) f.fdLock.Unlock() if err != nil && err != io.EOF { cryptfs.Warn.Printf("read: ReadAt: %s\n", err.Error()) return nil, fuse.ToStatus(err) } // Truncate ciphertext buffer down to actually read bytes ciphertext = ciphertext[0:n] firstBlockNo := blocks[0].BlockNo cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, firstBlockNo, alignedLength, n) // Decrypt it plaintext, err := f.cfs.DecryptBlocks(ciphertext, firstBlockNo, f.header.Id) if err != nil { curruptBlockNo := firstBlockNo + f.cfs.PlainOffToBlockNo(uint64(len(plaintext))) cipherOff := f.cfs.BlockNoToCipherOff(curruptBlockNo) plainOff := f.cfs.BlockNoToPlainOff(curruptBlockNo) cryptfs.Warn.Printf("ino%d: doRead: corrupt block #%d (plainOff=%d, cipherOff=%d)\n", 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) { cryptfs.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d\n", f.ino, len(buf), off) if f.writeOnly { cryptfs.Warn.Printf("ino%d: Tried to read from write-only file\n", f.ino) return nil, fuse.EBADF } out, status := f.doRead(uint64(off), uint64(len(buf))) if status == fuse.EIO { cryptfs.Warn.Printf("ino%d: Read failed with EIO, offset=%d, length=%d\n", f.ino, len(buf), off) } if status != fuse.OK { return nil, status } cryptfs.Debug.Printf("ino%d: Read: status %v, returning %d bytes\n", f.ino, status, len(out)) return fuse.ReadResultData(out), status } // fallocateRetry - syscall.Fallocate() with retry for EINTR. func fallocateRetry(fd int, mode uint32, off int64, len int64) (err error) { for { err = syscall.Fallocate(fd, mode, off, len) if err == syscall.EINTR { continue } return err } } 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. 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.cfs.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.PlaintextRange() oldData, status := f.doRead(o, f.cfs.PlainBS()) if status != fuse.OK { cryptfs.Warn.Printf("RMW read failed: %s\n", status.String()) return written, status } // Modify blockData = f.cfs.MergeBlocks(oldData, blockData, int(b.Skip)) cryptfs.Debug.Printf("len(oldData)=%d len(blockData)=%d\n", len(oldData), len(blockData)) } blockOffset, blockLen := b.CiphertextRange() blockData = f.cfs.EncryptBlock(blockData, b.BlockNo, f.header.Id) cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d, md5=%s\n", f.ino, len(blockData)-cryptfs.BLOCK_OVERHEAD, b.BlockNo, cryptfs.Debug.Md5sum(blockData)) // Prevent partially written (=corrupt) blocks by preallocating the space beforehand f.fdLock.Lock() err := fallocateRetry(int(f.fd.Fd()), FALLOC_FL_KEEP_SIZE, int64(blockOffset), int64(blockLen)) f.fdLock.Unlock() if err != nil { cryptfs.Warn.Printf("doWrite: fallocateRetry failed: %s\n", err.Error()) status = fuse.ToStatus(err) break } // Write f.fdLock.Lock() _, err = f.fd.WriteAt(blockData, int64(blockOffset)) f.fdLock.Unlock() if err != nil { cryptfs.Warn.Printf("doWrite: Write failed: %s\n", err.Error()) status = fuse.ToStatus(err) break } written += uint32(b.Length) } return written, status } // Write - FUSE call func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) { cryptfs.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d\n", f.ino, off, len(data)) fi, err := f.fd.Stat() if err != nil { cryptfs.Warn.Printf("Write: Fstat failed: %v\n", err) return 0, fuse.ToStatus(err) } plainSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size())) if f.createsHole(plainSize, off) { status := f.zeroPad(plainSize) if status != fuse.OK { cryptfs.Warn.Printf("zeroPad returned error %v\n", status) return 0, status } } return f.doWrite(data, off) } // Release - FUSE call, forget file func (f *file) Release() { f.fdLock.Lock() f.fd.Close() f.fdLock.Unlock() } // Flush - FUSE call func (f *file) Flush() fuse.Status { f.fdLock.Lock() // 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())) f.fdLock.Unlock() 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.Lock() r := fuse.ToStatus(syscall.Fsync(int(f.fd.Fd()))) f.fdLock.Unlock() return r } func (f *file) Truncate(newSize uint64) fuse.Status { // Common case first: Truncate to zero if newSize == 0 { f.fdLock.Lock() err := syscall.Ftruncate(int(f.fd.Fd()), 0) f.fdLock.Unlock() if err != nil { cryptfs.Warn.Printf("Ftruncate(fd, 0) returned error: %v", err) return fuse.ToStatus(err) } // A 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 { cryptfs.Warn.Printf("Truncate: Fstat failed: %v\n", err) return fuse.ToStatus(err) } oldSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size())) { oldB := float32(oldSize) / float32(f.cfs.PlainBS()) newB := float32(newSize) / float32(f.cfs.PlainBS()) cryptfs.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)\n", f.ino, oldB, newB, oldSize, newSize) } // File grows if newSize > oldSize { // File was empty, create new header if oldSize == 0 { err := f.createHeader() if err != nil { return fuse.ToStatus(err) } } blocks := f.cfs.ExplodePlainRange(oldSize, newSize-oldSize) for _, b := range blocks { // First and last block may be partial if b.IsPartial() { off, _ := b.PlaintextRange() off += b.Skip _, status := f.doWrite(make([]byte, b.Length), int64(off)) if status != fuse.OK { return status } } else { off, length := b.CiphertextRange() f.fdLock.Lock() err := syscall.Ftruncate(int(f.fd.Fd()), int64(off+length)) f.fdLock.Unlock() if err != nil { cryptfs.Warn.Printf("grow Ftruncate returned error: %v", err) return fuse.ToStatus(err) } } } return fuse.OK } else { // File shrinks blockNo := f.cfs.PlainOffToBlockNo(newSize) cipherOff := f.cfs.BlockNoToCipherOff(blockNo) plainOff := f.cfs.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 { cryptfs.Warn.Printf("shrink doRead returned error: %v", err) return status } } // Truncate down to last complete block f.fdLock.Lock() err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff)) f.fdLock.Unlock() if err != nil { cryptfs.Warn.Printf("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.Lock() r := fuse.ToStatus(f.fd.Chmod(os.FileMode(mode))) f.fdLock.Unlock() return r } func (f *file) Chown(uid uint32, gid uint32) fuse.Status { f.fdLock.Lock() r := fuse.ToStatus(f.fd.Chown(int(uid), int(gid))) f.fdLock.Unlock() return r } func (f *file) GetAttr(a *fuse.Attr) fuse.Status { cryptfs.Debug.Printf("file.GetAttr()\n") st := syscall.Stat_t{} f.fdLock.Lock() err := syscall.Fstat(int(f.fd.Fd()), &st) f.fdLock.Unlock() if err != nil { return fuse.ToStatus(err) } a.FromStat(&st) a.Size = f.cfs.CipherSizeToPlainSize(a.Size) return fuse.OK } // Allocate - FUSE call, fallocate(2) func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status { cryptfs.Warn.Printf("Fallocate is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1\n") return fuse.ENOSYS } const _UTIME_OMIT = ((1 << 30) - 2) func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status { 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() } f.fdLock.Lock() fn := fmt.Sprintf("/proc/self/fd/%d", f.fd.Fd()) err := syscall.UtimesNano(fn, ts) f.fdLock.Unlock() return fuse.ToStatus(err) }