libgocryptfs/pathfs_frontend/file.go

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package pathfs_frontend
import (
"io"
"bytes"
"fmt"
"os"
"sync"
"syscall"
"time"
"github.com/hanwen/go-fuse/fuse"
"github.com/hanwen/go-fuse/fuse/nodefs"
"github.com/rfjakob/gocryptfs/cryptfs"
)
// File - based on loopbackFile in go-fuse/fuse/nodefs/files.go
type file struct {
fd *os.File
// os.File is not threadsafe. Although fd themselves are
// constant during the lifetime of an open file, the OS may
// reuse the fd number after it is closed. When open races
// with another close, they may lead to confusion as which
// file gets written in the end.
lock sync.Mutex
// Was the file opened O_WRONLY?
writeOnly bool
// Parent CryptFS
cfs *cryptfs.CryptFS
}
func NewFile(fd *os.File, writeOnly bool, cfs *cryptfs.CryptFS) nodefs.File {
return &file{
fd: fd,
writeOnly: writeOnly,
cfs: cfs,
}
}
func (f *file) InnerFile() nodefs.File {
return nil
}
func (f *file) SetInode(n *nodefs.Inode) {
}
func (f *file) String() string {
return fmt.Sprintf("cryptFile(%s)", f.fd.Name())
}
// Called by Read() and for RMW in Write()
func (f *file) doRead(off uint64, length uint64) ([]byte, fuse.Status) {
// Read the backing ciphertext in one go
alignedOffset, alignedLength, skip := f.cfs.CiphertextRange(off, length)
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cryptfs.Debug.Printf("CiphertextRange(%d, %d) -> %d, %d, %d\n", off, length, alignedOffset, alignedLength, skip)
ciphertext := make([]byte, int(alignedLength))
f.lock.Lock()
n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
f.lock.Unlock()
ciphertext = ciphertext[0:n]
if err != nil && err != io.EOF {
cryptfs.Warn.Printf("read: ReadAt: %s\n", err.Error())
return nil, fuse.ToStatus(err)
}
cryptfs.Debug.Printf("ReadAt length=%d offset=%d -> n=%d len=%d\n", alignedLength, alignedOffset, n, len(ciphertext))
// Decrypt it
plaintext, err := f.cfs.DecryptBlocks(ciphertext)
if err != nil {
cryptfs.Warn.Printf("read: DecryptBlocks: %s\n", err.Error())
return nil, fuse.EIO
}
// Crop down to the relevant part
var out []byte
lenHave := len(plaintext)
lenWant := skip + int(length)
if lenHave > lenWant {
out = plaintext[skip:skip + int(length)]
} else if lenHave > 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) {
cryptfs.Debug.Printf("Read: offset=%d length=%d\n", len(buf), off)
if f.writeOnly {
cryptfs.Warn.Printf("Tried to read from write-only file\n")
return nil, fuse.EBADF
}
out, status := f.doRead(uint64(off), uint64(len(buf)))
if status != fuse.OK {
return nil, status
}
cryptfs.Debug.Printf("Read: returning %d bytes\n", len(out))
return fuse.ReadResultData(out), status
}
// Write - FUSE call
func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) {
cryptfs.Debug.Printf("Write: offset=%d length=%d\n", off, len(data))
var written uint32
var status fuse.Status
dataBuf := bytes.NewBuffer(data)
blocks := f.cfs.SplitRange(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()
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oldData, status := f.doRead(o, f.cfs.PlainBS())
if status != fuse.OK {
cryptfs.Warn.Printf("RMW read failed: %s\n", status.String())
return written, status
}
// Modify
blockData = f.cfs.MergeBlocks(oldData, blockData, int(b.Offset))
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cryptfs.Debug.Printf("len(oldData)=%d len(blockData)=%d\n", len(oldData), len(blockData))
}
// Write
blockOffset, _ := b.CiphertextRange()
blockData = f.cfs.EncryptBlock(blockData)
cryptfs.Debug.Printf("WriteAt offset=%d length=%d\n", blockOffset, len(blockData))
f.lock.Lock()
_, err := f.fd.WriteAt(blockData, int64(blockOffset))
f.lock.Unlock()
if err != nil {
cryptfs.Warn.Printf("Write failed: %s\n", err.Error())
status = fuse.ToStatus(err)
break
}
written += uint32(b.Length)
}
return written, status
}
// Release - FUSE call, forget file
func (f *file) Release() {
f.lock.Lock()
f.fd.Close()
f.lock.Unlock()
}
// Flush - FUSE call
func (f *file) Flush() fuse.Status {
f.lock.Lock()
// 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()))
f.lock.Unlock()
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.lock.Lock()
r := fuse.ToStatus(syscall.Fsync(int(f.fd.Fd())))
f.lock.Unlock()
return r
}
func (f *file) Truncate(size uint64) fuse.Status {
f.lock.Lock()
r := fuse.ToStatus(syscall.Ftruncate(int(f.fd.Fd()), int64(size)))
f.lock.Unlock()
return r
}
func (f *file) Chmod(mode uint32) fuse.Status {
f.lock.Lock()
r := fuse.ToStatus(f.fd.Chmod(os.FileMode(mode)))
f.lock.Unlock()
return r
}
func (f *file) Chown(uid uint32, gid uint32) fuse.Status {
f.lock.Lock()
r := fuse.ToStatus(f.fd.Chown(int(uid), int(gid)))
f.lock.Unlock()
return r
}
func (f *file) GetAttr(a *fuse.Attr) fuse.Status {
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cryptfs.Debug.Printf("file.GetAttr()\n")
st := syscall.Stat_t{}
f.lock.Lock()
err := syscall.Fstat(int(f.fd.Fd()), &st)
f.lock.Unlock()
if err != nil {
return fuse.ToStatus(err)
}
a.FromStat(&st)
a.Size = f.cfs.PlainSize(a.Size)
return fuse.OK
}
func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status {
f.lock.Lock()
err := syscall.Fallocate(int(f.fd.Fd()), mode, int64(off), int64(sz))
f.lock.Unlock()
if err != nil {
return fuse.ToStatus(err)
}
return fuse.OK
}
const _UTIME_NOW = ((1 << 30) - 1)
const _UTIME_OMIT = ((1 << 30) - 2)
func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status {
tv := make([]syscall.Timeval, 2)
if a == nil {
tv[0].Usec = _UTIME_OMIT
} else {
n := a.UnixNano()
tv[0] = syscall.NsecToTimeval(n)
}
if m == nil {
tv[1].Usec = _UTIME_OMIT
} else {
n := a.UnixNano()
tv[1] = syscall.NsecToTimeval(n)
}
f.lock.Lock()
err := syscall.Futimes(int(f.fd.Fd()), tv)
f.lock.Unlock()
return fuse.ToStatus(err)
}