package fusefrontend // FUSE operations on file handles import ( "bytes" "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/openfiletable" "github.com/rfjakob/gocryptfs/internal/serialize_reads" "github.com/rfjakob/gocryptfs/internal/stupidgcm" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) var _ nodefs.File = &file{} // Verify that interface is implemented. // 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 // Content encryption helper contentEnc *contentenc.ContentEnc // Device and inode number uniquely identify the backing file qIno openfiletable.QIno // Entry in the open file table fileTableEntry *openfiletable.Entry // go-fuse nodefs.loopbackFile loopbackFile nodefs.File // Store where the last byte was written lastWrittenOffset int64 // The opCount is used to judge whether "lastWrittenOffset" is still // guaranteed to be correct. lastOpCount uint64 // Parent filesystem fs *FS // We embed a nodefs.NewDefaultFile() that returns ENOSYS for every operation we // have not implemented. This prevents build breakage when the go-fuse library // adds new methods to the nodefs.File interface. nodefs.File } // NewFile returns a new go-fuse File instance. func NewFile(fd *os.File, fs *FS) (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) } qi := openfiletable.QInoFromStat(&st) e := openfiletable.Register(qi) return &file{ fd: fd, contentEnc: fs.contentEnc, qIno: qi, fileTableEntry: e, loopbackFile: nodefs.NewLoopbackFile(fd), fs: fs, File: nodefs.NewDefaultFile(), }, 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()) } // readFileID loads the file header from disk and extracts the file ID. // Returns io.EOF if the file is empty. func (f *file) readFileID() ([]byte, error) { // We read +1 byte to determine if the file has actual content // and not only the header. A header-only file will be considered empty. // This makes File ID poisoning more difficult. readLen := contentenc.HeaderLen + 1 buf := make([]byte, readLen) n, err := f.fd.ReadAt(buf, 0) if err != nil { if err == io.EOF && n != 0 { tlog.Warn.Printf("ino%d: readFileID: incomplete file, got %d instead of %d bytes", f.qIno.Ino, n, readLen) } return nil, err } buf = buf[:contentenc.HeaderLen] h, err := contentenc.ParseHeader(buf) if err != nil { return nil, err } return h.ID, nil } // createHeader creates a new random header and writes it to disk. // Returns the new file ID. // The caller must hold fileIDLock.Lock(). func (f *file) createHeader() (fileID []byte, err error) { h := contentenc.RandomHeader() buf := h.Pack() // Prevent partially written (=corrupt) header by preallocating the space beforehand if !f.fs.args.NoPrealloc { err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), 0, contentenc.HeaderLen) if err != nil { tlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.qIno.Ino, err.Error()) return nil, err } } // Actually write header _, err = f.fd.WriteAt(buf, 0) if err != nil { return nil, err } return h.ID, err } // 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) { // Make sure we have the file ID. f.fileTableEntry.HeaderLock.RLock() if f.fileTableEntry.ID == nil { f.fileTableEntry.HeaderLock.RUnlock() // Yes, somebody else may take the lock before we can. This will get // the header read twice, but causes no harm otherwise. f.fileTableEntry.HeaderLock.Lock() tmpID, err := f.readFileID() if err == io.EOF { f.fileTableEntry.HeaderLock.Unlock() return nil, fuse.OK } if err != nil { f.fileTableEntry.HeaderLock.Unlock() return nil, fuse.ToStatus(err) } f.fileTableEntry.ID = tmpID // Downgrade the lock. f.fileTableEntry.HeaderLock.Unlock() // The file ID may change in here. This does no harm because we // re-read it after the RLock(). f.fileTableEntry.HeaderLock.RLock() } fileID := f.fileTableEntry.ID // 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)) // We don't care if the file ID changes after we have read the data. Drop the lock. f.fileTableEntry.HeaderLock.RUnlock() 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, fileID) if err != nil { if f.fs.args.ForceDecode && err == stupidgcm.ErrAuth { // We do not have the information which block was corrupt here anymore, // but DecryptBlocks() has already logged it anyway. tlog.Warn.Printf("ino%d: doRead off=%d len=%d: returning corrupt data due to forcedecode", f.qIno.Ino, off, length) } else { curruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext))) tlog.Warn.Printf("ino%d: doRead: corrupt block #%d: %v", f.qIno.Ino, curruptBlockNo, err) 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.qIno.Ino, len(buf), off) if f.fs.args.SerializeReads { serialize_reads.Wait(off, len(buf)) } out, status := f.doRead(uint64(off), uint64(len(buf))) if f.fs.args.SerializeReads { serialize_reads.Done() } if status == fuse.EIO { tlog.Warn.Printf("ino%d: Read: returning EIO, offset=%d, length=%d", f.qIno.Ino, len(buf), off) } if status != fuse.OK { return nil, status } tlog.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.qIno.Ino, status, len(out)) return fuse.ReadResultData(out), status } // 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 necessary // // 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 f.fileTableEntry.HeaderLock.RLock() if f.fileTableEntry.ID == nil { f.fileTableEntry.HeaderLock.RUnlock() // Somebody else may write the header here, but this would do no harm. f.fileTableEntry.HeaderLock.Lock() tmpID, err := f.readFileID() if err == io.EOF { tmpID, err = f.createHeader() } if err != nil { f.fileTableEntry.HeaderLock.Unlock() return 0, fuse.ToStatus(err) } f.fileTableEntry.ID = tmpID f.fileTableEntry.HeaderLock.Unlock() // The file ID may change in here. This does no harm because we // re-read it after the RLock(). f.fileTableEntry.HeaderLock.RLock() } defer f.fileTableEntry.HeaderLock.RUnlock() // Handle payload data dataBuf := bytes.NewBuffer(data) blocks := f.contentEnc.ExplodePlainRange(uint64(off), uint64(len(data))) toEncrypt := make([][]byte, len(blocks)) for i, b := range blocks { blockData := dataBuf.Next(int(b.Length)) // Incomplete block -> Read-Modify-Write if b.IsPartial() { // Read oldData, status := f.doRead(b.BlockPlainOff(), f.contentEnc.PlainBS()) if status != fuse.OK { tlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.qIno.Ino, f.intFd(), status.String()) return 0, status } // Modify blockData = f.contentEnc.MergeBlocks(oldData, blockData, int(b.Skip)) tlog.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData)) } tlog.Debug.Printf("ino%d: Writing %d bytes to block #%d", f.qIno.Ino, uint64(len(blockData))-f.contentEnc.BlockOverhead(), b.BlockNo) // Write into the to-encrypt list toEncrypt[i] = blockData } // Encrypt all blocks ciphertext := f.contentEnc.EncryptBlocks(toEncrypt, blocks[0].BlockNo, f.fileTableEntry.ID) // Preallocate so we cannot run out of space in the middle of the write. // This prevents partially written (=corrupt) blocks. var err error cOff := int64(blocks[0].BlockCipherOff()) if !f.fs.args.NoPrealloc { err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), cOff, int64(len(ciphertext))) if err != nil { tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %s", f.qIno.Ino, f.intFd(), err.Error()) return 0, fuse.ToStatus(err) } } // Write _, err = f.fd.WriteAt(ciphertext, cOff) // Return memory to cWritePool f.fs.contentEnc.CWritePut(ciphertext) if err != nil { tlog.Warn.Printf("doWrite: Write failed: %s", err.Error()) return 0, fuse.ToStatus(err) } return uint32(len(data)), fuse.OK } // isConsecutiveWrite returns true if the current write // directly (in time and space) follows the last write. // This is an optimisation for streaming writes on NFS where a // Stat() call is very expensive. // The caller must "wlock.lock(f.devIno.ino)" otherwise this check would be racy. func (f *file) isConsecutiveWrite(off int64) bool { opCount := openfiletable.WriteOpCount() return opCount == f.lastOpCount+1 && off == f.lastWrittenOffset+1 } // 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.qIno.Ino, f.intFd()) return 0, fuse.EBADF } f.fileTableEntry.ContentLock.Lock() defer f.fileTableEntry.ContentLock.Unlock() tlog.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.qIno.Ino, off, len(data)) // If the write creates a file hole, we have to zero-pad the last block. // But if the write directly follows an earlier write, it cannot create a // hole, and we can save one Stat() call. if !f.isConsecutiveWrite(off) { status := f.writePadHole(off) if !status.Ok() { return 0, status } } n, status := f.doWrite(data, off) if status.Ok() { f.lastOpCount = openfiletable.WriteOpCount() f.lastWrittenOffset = off + int64(len(data)) - 1 } return n, status } // Release - FUSE call, close file func (f *file) Release() { f.fdLock.Lock() if f.released { log.Panicf("ino%d fh%d: double release", f.qIno.Ino, f.intFd()) } f.fd.Close() f.released = true f.fdLock.Unlock() openfiletable.Unregister(f.qIno) } // 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()))) } 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) if f.fs.args.ForceOwner != nil { a.Owner = *f.fs.args.ForceOwner } return fuse.OK } func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status { f.fdLock.RLock() defer f.fdLock.RUnlock() return f.loopbackFile.Utimens(a, m) }