diff options
Diffstat (limited to 'internal/fusefrontend/file.go')
| -rw-r--r-- | internal/fusefrontend/file.go | 443 |
1 files changed, 443 insertions, 0 deletions
diff --git a/internal/fusefrontend/file.go b/internal/fusefrontend/file.go new file mode 100644 index 0000000..66b3e24 --- /dev/null +++ b/internal/fusefrontend/file.go @@ -0,0 +1,443 @@ +package fusefrontend + +// FUSE operations on file handles + +import ( + "bytes" + "context" + "encoding/hex" + "fmt" + "io" + "log" + "os" + "sync" + "syscall" + + "github.com/hanwen/go-fuse/v2/fs" + "github.com/hanwen/go-fuse/v2/fuse" + + "github.com/rfjakob/gocryptfs/internal/contentenc" + "github.com/rfjakob/gocryptfs/internal/inomap" + "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" +) + +// 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. +func NewFile(fd *os.File, rn *RootNode, st *syscall.Stat_t) *File { + qi := inomap.QInoFromStat(st) + e := openfiletable.Register(qi) + + return &File{ + fd: fd, + contentEnc: rn.contentEnc, + qIno: qi, + fileTableEntry: e, + rootNode: rn, + } +} + +// 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 { + 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) + 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 { + if f.rootNode.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("doRead %d: 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("doRead %d: corrupt block #%d: %v", f.qIno.Ino, curruptBlockNo, 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)) + if f.rootNode.args.SerializeReads { + serialize_reads.Wait(off, len(buf)) + } + out, errno := f.doRead(buf[:0], uint64(off), uint64(len(buf))) + if f.rootNode.args.SerializeReads { + serialize_reads.Done() + } + 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 + // Get the file ID, create a new one if it does not exist yet. + var fileID []byte + // The caller has exclusively locked ContentLock, which blocks all other + // readers and writers. No need to take IDLock. + if f.fileTableEntry.ID != nil { + fileID = f.fileTableEntry.ID + } else { + // If the file ID is not cached, read it from disk + 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 + } + 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 := int64(blocks[0].BlockCipherOff()) + if !f.rootNode.args.NoPrealloc { + err = syscallcompat.EnospcPrealloc(f.intFd(), 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, 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) + f.fd.Close() + f.fdLock.Unlock() + return 0 +} + +// Flush - FUSE call +func (f *File) Flush(ctx context.Context) syscall.Errno { + 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(f.intFd()) + + if err != nil { + return fs.ToErrno(err) + } + err = syscall.Close(newFd) + return fs.ToErrno(err) +} + +// Fsync FUSE call +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 +} |