package fusefrontend // FUSE operations on file handles import ( "bytes" "context" "encoding/hex" "fmt" "io" "log" "math" "os" "sync" "syscall" "github.com/hanwen/go-fuse/v2/fs" "github.com/hanwen/go-fuse/v2/fuse" "github.com/rfjakob/gocryptfs/v2/internal/contentenc" "github.com/rfjakob/gocryptfs/v2/internal/inomap" "github.com/rfjakob/gocryptfs/v2/internal/openfiletable" "github.com/rfjakob/gocryptfs/v2/internal/syscallcompat" "github.com/rfjakob/gocryptfs/v2/internal/tlog" ) // File implements the go-fuse v2 API (github.com/hanwen/go-fuse/v2/fs) 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 inomap.QIno // Entry in the open file table fileTableEntry *openfiletable.Entry // 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 rootNode *RootNode } // NewFile returns a new go-fuse File instance based on an already-open file // descriptor. NewFile internally calls Fstat() on the fd. The resulting Stat_t // is returned because node.Create() needs it. // // `cName` is only used for error logging and may be left blank. func NewFile(fd int, cName string, rn *RootNode) (f *File, st *syscall.Stat_t, errno syscall.Errno) { // Need device number and inode number for openfiletable locking st = &syscall.Stat_t{} if err := syscall.Fstat(fd, st); err != nil { errno = fs.ToErrno(err) return } qi := inomap.QInoFromStat(st) e := openfiletable.Register(qi) osFile := os.NewFile(uintptr(fd), cName) f = &File{ fd: osFile, contentEnc: rn.contentEnc, qIno: qi, fileTableEntry: e, rootNode: rn, } return f, st, 0 } // intFd - return the backing file descriptor as an integer. 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("readFileID %d: incomplete file, got %d instead of %d bytes", f.qIno.Ino, n, readLen) f.rootNode.reportMitigatedCorruption(fmt.Sprint(f.qIno.Ino)) } 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.rootNode.args.NoPrealloc && f.rootNode.quirks&syscallcompat.QuirkBrokenFalloc == 0 { err = syscallcompat.EnospcPrealloc(f.intFd(), 0, contentenc.HeaderLen) if err != nil { if !syscallcompat.IsENOSPC(err) { 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 - read "length" plaintext bytes from plaintext offset "off" and append // to "dst". // 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() via doWrite() for Read-Modify-Write. func (f *File) doRead(dst []byte, off uint64, length uint64) ([]byte, syscall.Errno) { // Get the file ID, either from the open file table, or from disk. var fileID []byte f.fileTableEntry.IDLock.Lock() if f.fileTableEntry.ID != nil { // Use the cached value in the file table fileID = f.fileTableEntry.ID } else { // Not cached, we have to read it from disk. var err error fileID, err = f.readFileID() if err != nil { f.fileTableEntry.IDLock.Unlock() if err == io.EOF { // Empty file return nil, 0 } buf := make([]byte, 100) n, _ := f.fd.ReadAt(buf, 0) buf = buf[:n] hexdump := hex.EncodeToString(buf) tlog.Warn.Printf("doRead %d: corrupt header: %v\nFile hexdump (%d bytes): %s", f.qIno.Ino, err, n, hexdump) return nil, syscall.EIO } // Save into the file table f.fileTableEntry.ID = fileID } f.fileTableEntry.IDLock.Unlock() if fileID == nil { log.Panicf("fileID=%v", fileID) } // Read the backing ciphertext in one go blocks := f.contentEnc.ExplodePlainRange(off, length) alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks) // f.fd.ReadAt takes an int64! if alignedOffset > math.MaxInt64 { return nil, syscall.EFBIG } skip := blocks[0].Skip tlog.Debug.Printf("doRead: off=%d len=%d -> off=%d len=%d skip=%d\n", off, length, alignedOffset, alignedLength, skip) ciphertext := f.rootNode.contentEnc.CReqPool.Get() ciphertext = ciphertext[: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, fs.ToErrno(err) } // The ReadAt came back empty. We can skip all the decryption and return early. if n == 0 { f.rootNode.contentEnc.CReqPool.Put(ciphertext) return dst, 0 } // 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) f.rootNode.contentEnc.CReqPool.Put(ciphertext) if err != nil { corruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext))) tlog.Warn.Printf("doRead %d: corrupt block #%d: %v", f.qIno.Ino, corruptBlockNo, err) return nil, syscall.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 out = append(dst, out...) f.rootNode.contentEnc.PReqPool.Put(plaintext) return out, 0 } // Read - FUSE call func (f *File) Read(ctx context.Context, buf []byte, off int64) (resultData fuse.ReadResult, errno syscall.Errno) { if len(buf) > fuse.MAX_KERNEL_WRITE { // This would crash us due to our fixed-size buffer pool tlog.Warn.Printf("Read: rejecting oversized request with EMSGSIZE, len=%d", len(buf)) return nil, syscall.EMSGSIZE } f.fdLock.RLock() defer f.fdLock.RUnlock() f.fileTableEntry.ContentLock.RLock() defer f.fileTableEntry.ContentLock.RUnlock() tlog.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.qIno.Ino, off, len(buf)) out, errno := f.doRead(buf[:0], uint64(off), uint64(len(buf))) if errno != 0 { return nil, errno } tlog.Debug.Printf("ino%d: Read: errno=%d, returning %d bytes", f.qIno.Ino, errno, len(out)) return fuse.ReadResultData(out), errno } // 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, syscall.Errno) { fileWasEmpty := false // The caller has exclusively locked ContentLock, which blocks all other // readers and writers. No need to take IDLock. // // If the file ID is not cached, read it from disk if f.fileTableEntry.ID == nil { var err error fileID, err := f.readFileID() // Write a new file header if the file is empty if err == io.EOF { fileID, err = f.createHeader() fileWasEmpty = true } else if err != nil { // Other errors mean readFileID() found a corrupt header tlog.Warn.Printf("doWrite %d: corrupt header: %v", f.qIno.Ino, err) return 0, syscall.EIO } if err != nil { return 0, fs.ToErrno(err) } f.fileTableEntry.ID = fileID } // 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, errno := f.doRead(nil, b.BlockPlainOff(), f.contentEnc.PlainBS()) if errno != 0 { tlog.Warn.Printf("ino%d fh%d: RMW read failed: errno=%d", f.qIno.Ino, f.intFd(), errno) return 0, errno } // 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, len(blockData), 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 := blocks[0].BlockCipherOff() // f.fd.WriteAt & syscallcompat.EnospcPrealloc take int64 offsets! if cOff > math.MaxInt64 { return 0, syscall.EFBIG } if !f.rootNode.args.NoPrealloc && f.rootNode.quirks&syscallcompat.QuirkBrokenFalloc == 0 { err = syscallcompat.EnospcPrealloc(f.intFd(), int64(cOff), int64(len(ciphertext))) if err != nil { if !syscallcompat.IsENOSPC(err) { tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %v", f.qIno.Ino, f.intFd(), err) } if fileWasEmpty { // Kill the file header again f.fileTableEntry.ID = nil err2 := syscall.Ftruncate(f.intFd(), 0) if err2 != nil { tlog.Warn.Printf("ino%d fh%d: doWrite: rollback failed: %v", f.qIno.Ino, f.intFd(), err2) } } return 0, fs.ToErrno(err) } } // Write _, err = f.fd.WriteAt(ciphertext, int64(cOff)) // Return memory to CReqPool f.rootNode.contentEnc.CReqPool.Put(ciphertext) if err != nil { tlog.Warn.Printf("ino%d fh%d: doWrite: WriteAt off=%d len=%d failed: %v", f.qIno.Ino, f.intFd(), cOff, len(ciphertext), err) return 0, fs.ToErrno(err) } return uint32(len(data)), 0 } // 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(ctx context.Context, data []byte, off int64) (uint32, syscall.Errno) { if len(data) > fuse.MAX_KERNEL_WRITE { // This would crash us due to our fixed-size buffer pool tlog.Warn.Printf("Write: rejecting oversized request with EMSGSIZE, len=%d", len(data)) return 0, syscall.EMSGSIZE } f.fdLock.RLock() defer f.fdLock.RUnlock() if f.released { // The file descriptor has been closed concurrently tlog.Warn.Printf("ino%d fh%d: Write on released file", f.qIno.Ino, f.intFd()) return 0, syscall.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) { errno := f.writePadHole(off) if errno != 0 { return 0, errno } } n, errno := f.doWrite(data, off) if errno == 0 { f.lastOpCount = openfiletable.WriteOpCount() f.lastWrittenOffset = off + int64(len(data)) - 1 } return n, errno } // Release - FUSE call, close file func (f *File) Release(ctx context.Context) syscall.Errno { f.fdLock.Lock() if f.released { log.Panicf("ino%d fh%d: double release", f.qIno.Ino, f.intFd()) } f.released = true openfiletable.Unregister(f.qIno) err := f.fd.Close() f.fdLock.Unlock() return fs.ToErrno(err) } // Flush - FUSE call func (f *File) Flush(ctx context.Context) syscall.Errno { f.fdLock.RLock() defer f.fdLock.RUnlock() err := syscallcompat.Flush(f.intFd()) return fs.ToErrno(err) } // Fsync: handles FUSE opcode FSYNC // // Unfortunately, as Node.Fsync is also defined and takes precedence, // File.Fsync is never called at the moment. func (f *File) Fsync(ctx context.Context, flags uint32) (errno syscall.Errno) { f.fdLock.RLock() defer f.fdLock.RUnlock() return fs.ToErrno(syscall.Fsync(f.intFd())) } // Getattr FUSE call (like stat) func (f *File) Getattr(ctx context.Context, a *fuse.AttrOut) syscall.Errno { f.fdLock.RLock() defer f.fdLock.RUnlock() tlog.Debug.Printf("file.GetAttr()") st := syscall.Stat_t{} err := syscall.Fstat(f.intFd(), &st) if err != nil { return fs.ToErrno(err) } f.rootNode.inoMap.TranslateStat(&st) a.FromStat(&st) a.Size = f.contentEnc.CipherSizeToPlainSize(a.Size) if f.rootNode.args.ForceOwner != nil { a.Owner = *f.rootNode.args.ForceOwner } return 0 }