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-rw-r--r--internal/fusefrontend/file.go443
1 files changed, 443 insertions, 0 deletions
diff --git a/internal/fusefrontend/file.go b/internal/fusefrontend/file.go
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+++ 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
+}