1 files changed, 501 insertions, 0 deletions
diff --git a/internal/fusefrontend/file.go b/internal/fusefrontend/file.go
new file mode 100644
index 0000000..2e0b504
--- /dev/null
+++ b/internal/fusefrontend/file.go
@@ -0,0 +1,501 @@
+package fusefrontend
+
+// 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/internal/contentenc"
+	"github.com/rfjakob/gocryptfs/internal/toggledlog"
+)
+
+// File - based on loopbackFile in go-fuse/fuse/nodefs/files.go
+type file struct {
+	fd *os.File
+
+	// 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, hence has to acquire an exclusive lock.
+	fdLock sync.RWMutex
+
+	// Was the file opened O_WRONLY?
+	writeOnly bool
+
+	// Content encryption helper
+	contentEnc *contentenc.ContentEnc
+
+	// Inode number
+	ino uint64
+
+	// File header
+	header *contentenc.FileHeader
+
+	forgotten bool
+}
+
+func NewFile(fd *os.File, writeOnly bool, contentEnc *contentenc.ContentEnc) nodefs.File {
+	var st syscall.Stat_t
+	syscall.Fstat(int(fd.Fd()), &st)
+	wlock.register(st.Ino)
+
+	return &file{
+		fd:        fd,
+		writeOnly: writeOnly,
+		contentEnc: contentEnc,
+		ino:       st.Ino,
+	}
+}
+
+// intFd - return the backing file descriptor as an integer. Used for debug
+// messages.
+func (f *file) intFd() int {
+	return int(f.fd.Fd())
+}
+
+func (f *file) InnerFile() nodefs.File {
+	return nil
+}
+
+func (f *file) SetInode(n *nodefs.Inode) {
+}
+
+// readHeader - load the file header from disk
+//
+// Returns io.EOF if the file is empty
+func (f *file) readHeader() error {
+	buf := make([]byte, contentenc.HEADER_LEN)
+	_, err := f.fd.ReadAt(buf, 0)
+	if err != nil {
+		return err
+	}
+	h, err := contentenc.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 := contentenc.RandomHeader()
+	buf := h.Pack()
+
+	// Prevent partially written (=corrupt) header by preallocating the space beforehand
+	err := prealloc(int(f.fd.Fd()), 0, contentenc.HEADER_LEN)
+	if err != nil {
+		toggledlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.ino, 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.contentEnc.ExplodePlainRange(off, length)
+	alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
+	skip := blocks[0].Skip
+	toggledlog.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))
+	if err != nil && err != io.EOF {
+		toggledlog.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
+	toggledlog.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, f.header.Id)
+	if err != nil {
+		curruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext)))
+		cipherOff := f.contentEnc.BlockNoToCipherOff(curruptBlockNo)
+		plainOff := f.contentEnc.BlockNoToPlainOff(curruptBlockNo)
+		toggledlog.Warn.Printf("ino%d: doRead: corrupt block #%d (plainOff=%d, cipherOff=%d)",
+			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) {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	toggledlog.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.ino, len(buf), off)
+
+	if f.writeOnly {
+		toggledlog.Warn.Printf("ino%d: Tried to read from write-only file", f.ino)
+		return nil, fuse.EBADF
+	}
+
+	out, status := f.doRead(uint64(off), uint64(len(buf)))
+
+	if status == fuse.EIO {
+		toggledlog.Warn.Printf("ino%d: Read failed with EIO, offset=%d, length=%d", f.ino, len(buf), off)
+	}
+	if status != fuse.OK {
+		return nil, status
+	}
+
+	toggledlog.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.ino, status, len(out))
+	return fuse.ReadResultData(out), status
+}
+
+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.contentEnc.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.contentEnc.PlainBS())
+			if status != fuse.OK {
+				toggledlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.ino, f.intFd(), status.String())
+				return written, status
+			}
+			// Modify
+			blockData = f.contentEnc.MergeBlocks(oldData, blockData, int(b.Skip))
+			toggledlog.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData))
+		}
+
+		// Encrypt
+		blockOffset, blockLen := b.CiphertextRange()
+		blockData = f.contentEnc.EncryptBlock(blockData, b.BlockNo, f.header.Id)
+		toggledlog.Debug.Printf("ino%d: Writing %d bytes to block #%d",
+			f.ino, uint64(len(blockData))-f.contentEnc.BlockOverhead(), b.BlockNo)
+
+		// Prevent partially written (=corrupt) blocks by preallocating the space beforehand
+		err := prealloc(int(f.fd.Fd()), int64(blockOffset), int64(blockLen))
+		if err != nil {
+			toggledlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %s", f.ino, f.intFd(), err.Error())
+			status = fuse.ToStatus(err)
+			break
+		}
+
+		// Write
+		_, err = f.fd.WriteAt(blockData, int64(blockOffset))
+
+		if err != nil {
+			toggledlog.Warn.Printf("doWrite: Write failed: %s", 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) {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+	wlock.lock(f.ino)
+	defer wlock.unlock(f.ino)
+
+	toggledlog.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.ino, off, len(data))
+
+	fi, err := f.fd.Stat()
+	if err != nil {
+		toggledlog.Warn.Printf("Write: Fstat failed: %v", err)
+		return 0, fuse.ToStatus(err)
+	}
+	plainSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size()))
+	if f.createsHole(plainSize, off) {
+		status := f.zeroPad(plainSize)
+		if status != fuse.OK {
+			toggledlog.Warn.Printf("zeroPad returned error %v", status)
+			return 0, status
+		}
+	}
+	return f.doWrite(data, off)
+}
+
+// Release - FUSE call, close file
+func (f *file) Release() {
+	f.fdLock.Lock()
+	defer f.fdLock.Unlock()
+
+	f.fd.Close()
+	f.forgotten = true
+}
+
+// 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())))
+}
+
+// Truncate - FUSE call
+func (f *file) Truncate(newSize uint64) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+	wlock.lock(f.ino)
+	defer wlock.unlock(f.ino)
+
+	if f.forgotten {
+		toggledlog.Warn.Printf("ino%d fh%d: Truncate on forgotten file", f.ino, f.intFd())
+	}
+
+	// Common case first: Truncate to zero
+	if newSize == 0 {
+		err := syscall.Ftruncate(int(f.fd.Fd()), 0)
+		if err != nil {
+			toggledlog.Warn.Printf("ino%d fh%d: Ftruncate(fd, 0) returned error: %v", f.ino, f.intFd(), err)
+			return fuse.ToStatus(err)
+		}
+		// 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 {
+		toggledlog.Warn.Printf("ino%d fh%d: Truncate: Fstat failed: %v", f.ino, f.intFd(), err)
+		return fuse.ToStatus(err)
+	}
+	oldSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size()))
+	{
+		oldB := float32(oldSize) / float32(f.contentEnc.PlainBS())
+		newB := float32(newSize) / float32(f.contentEnc.PlainBS())
+		toggledlog.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)", f.ino, oldB, newB, oldSize, newSize)
+	}
+
+	// File size stays the same - nothing to do
+	if newSize == oldSize {
+		return fuse.OK
+	}
+
+	// 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.contentEnc.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()
+				err := syscall.Ftruncate(int(f.fd.Fd()), int64(off+length))
+				if err != nil {
+					toggledlog.Warn.Printf("grow Ftruncate returned error: %v", err)
+					return fuse.ToStatus(err)
+				}
+			}
+		}
+		return fuse.OK
+	} else {
+		// File shrinks
+		blockNo := f.contentEnc.PlainOffToBlockNo(newSize)
+		cipherOff := f.contentEnc.BlockNoToCipherOff(blockNo)
+		plainOff := f.contentEnc.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 {
+				toggledlog.Warn.Printf("shrink doRead returned error: %v", err)
+				return status
+			}
+		}
+		// Truncate down to last complete block
+		err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
+		if err != nil {
+			toggledlog.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.RLock()
+	defer f.fdLock.RUnlock()
+
+	return fuse.ToStatus(f.fd.Chmod(os.FileMode(mode)))
+}
+
+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()
+
+	toggledlog.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)
+
+	return fuse.OK
+}
+
+// Allocate - FUSE call, fallocate(2)
+var allocateWarned bool
+
+func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status {
+	// Only warn once
+	if !allocateWarned {
+		toggledlog.Warn.Printf("fallocate(2) is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1")
+		allocateWarned = true
+	}
+	return fuse.ENOSYS
+}
+
+const _UTIME_OMIT = ((1 << 30) - 2)
+
+func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	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()
+	}
+
+	fn := fmt.Sprintf("/proc/self/fd/%d", f.fd.Fd())
+	return fuse.ToStatus(syscall.UtimesNano(fn, ts))
+}