libgocryptfs/pathfs_frontend/file.go
Jakob Unterwurzacher fa3a382aa4 Handle ENOSPC errors better by preallocating the space before writing
Prevent the case that we run out of space in the middle of
writing a block - that would leave a corrupt block behind.
2015-11-08 22:36:29 +01:00

476 lines
12 KiB
Go

package pathfs_frontend
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/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.
fdLock sync.Mutex
// Was the file opened O_WRONLY?
writeOnly bool
// Parent CryptFS
cfs *cryptfs.CryptFS
// Inode number
ino uint64
// File header
header *cryptfs.FileHeader
}
func NewFile(fd *os.File, writeOnly bool, cfs *cryptfs.CryptFS) nodefs.File {
var st syscall.Stat_t
syscall.Fstat(int(fd.Fd()), &st)
return &file{
fd: fd,
writeOnly: writeOnly,
cfs: cfs,
ino: st.Ino,
}
}
func (f *file) InnerFile() nodefs.File {
return nil
}
func (f *file) SetInode(n *nodefs.Inode) {
}
// Ensure that all modifications to the file contents are serialized and no
// reads happen concurrently.
//
// This prevents several races:
// * getFileId vs Truncate
// * zeroPad vs Read
// * RMW vs Write
func (f *file) wlock() {
}
func (f *file) rlock() {
}
func (f *file) unlock() {
}
// readHeader - load the file header from disk
//
// Returns io.EOF if the file is empty
func (f *file) readHeader() error {
buf := make([]byte, cryptfs.HEADER_LEN)
_, err := f.fd.ReadAt(buf, 0)
if err != nil {
return err
}
h, err := cryptfs.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 := cryptfs.RandomHeader()
buf := h.Pack()
_, 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.cfs.ExplodePlainRange(off, length)
alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
skip := blocks[0].Skip
cryptfs.Debug.Printf("JointCiphertextRange(%d, %d) -> %d, %d, %d\n", off, length, alignedOffset, alignedLength, skip)
ciphertext := make([]byte, int(alignedLength))
f.fdLock.Lock()
n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
f.fdLock.Unlock()
if err != nil && err != io.EOF {
cryptfs.Warn.Printf("read: ReadAt: %s\n", err.Error())
return nil, fuse.ToStatus(err)
}
// Truncate ciphertext buffer down to actually read bytes
ciphertext = ciphertext[0:n]
firstBlockNo := blocks[0].BlockNo
cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, firstBlockNo, alignedLength, n)
// Decrypt it
plaintext, err := f.cfs.DecryptBlocks(ciphertext, firstBlockNo, f.header.Id)
if err != nil {
curruptBlockNo := firstBlockNo + f.cfs.PlainOffToBlockNo(uint64(len(plaintext)))
cipherOff := f.cfs.BlockNoToCipherOff(curruptBlockNo)
plainOff := f.cfs.BlockNoToPlainOff(curruptBlockNo)
cryptfs.Warn.Printf("ino%d: doRead: corrupt block #%d (plainOff=%d, cipherOff=%d)\n",
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) {
cryptfs.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d\n", f.ino, len(buf), off)
if f.writeOnly {
cryptfs.Warn.Printf("ino%d: Tried to read from write-only file\n", f.ino)
return nil, fuse.EBADF
}
out, status := f.doRead(uint64(off), uint64(len(buf)))
if status == fuse.EIO {
cryptfs.Warn.Printf("ino%d: Read failed with EIO, offset=%d, length=%d\n", f.ino, len(buf), off)
}
if status != fuse.OK {
return nil, status
}
cryptfs.Debug.Printf("ino%d: Read: status %v, returning %d bytes\n", 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.cfs.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.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.Skip))
cryptfs.Debug.Printf("len(oldData)=%d len(blockData)=%d\n", len(oldData), len(blockData))
}
// Write
blockOffset, blockLen := b.CiphertextRange()
blockData = f.cfs.EncryptBlock(blockData, b.BlockNo, f.header.Id)
cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d, md5=%s\n",
f.ino, len(blockData)-cryptfs.BLOCK_OVERHEAD, b.BlockNo, cryptfs.Debug.Md5sum(blockData))
// Prevent partially written (=corrupt) blocks by preallocating the space beforehand
f.fdLock.Lock()
err := syscall.Fallocate(int(f.fd.Fd()), FALLOC_FL_KEEP_SIZE, int64(blockOffset), int64(blockLen))
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("doWrite: Fallocate failed: %s\n", err.Error())
status = fuse.ToStatus(err)
break
}
f.fdLock.Lock()
_, err = f.fd.WriteAt(blockData, int64(blockOffset))
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("doWrite: Write failed: %s\n", 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) {
cryptfs.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d\n", f.ino, off, len(data))
fi, err := f.fd.Stat()
if err != nil {
cryptfs.Warn.Printf("Write: Fstat failed: %v\n", err)
return 0, fuse.ToStatus(err)
}
plainSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size()))
if f.createsHole(plainSize, off) {
status := f.zeroPad(plainSize)
if status != fuse.OK {
cryptfs.Warn.Printf("zeroPad returned error %v\n", status)
return 0, status
}
}
return f.doWrite(data, off)
}
// Release - FUSE call, forget file
func (f *file) Release() {
f.fdLock.Lock()
f.fd.Close()
f.fdLock.Unlock()
}
// Flush - FUSE call
func (f *file) Flush() fuse.Status {
f.fdLock.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.fdLock.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.fdLock.Lock()
r := fuse.ToStatus(syscall.Fsync(int(f.fd.Fd())))
f.fdLock.Unlock()
return r
}
func (f *file) Truncate(newSize uint64) fuse.Status {
// Common case first: Truncate to zero
if newSize == 0 {
f.fdLock.Lock()
err := syscall.Ftruncate(int(f.fd.Fd()), 0)
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("Ftruncate(fd, 0) returned error: %v", err)
return fuse.ToStatus(err)
}
// A 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 {
cryptfs.Warn.Printf("Truncate: Fstat failed: %v\n", err)
return fuse.ToStatus(err)
}
oldSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size()))
{
oldB := float32(oldSize) / float32(f.cfs.PlainBS())
newB := float32(newSize) / float32(f.cfs.PlainBS())
cryptfs.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)\n", f.ino, oldB, newB, oldSize, newSize)
}
// 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.cfs.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()
f.fdLock.Lock()
err := syscall.Ftruncate(int(f.fd.Fd()), int64(off+length))
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("grow Ftruncate returned error: %v", err)
return fuse.ToStatus(err)
}
}
}
return fuse.OK
} else {
// File shrinks
blockNo := f.cfs.PlainOffToBlockNo(newSize)
cipherOff := f.cfs.BlockNoToCipherOff(blockNo)
plainOff := f.cfs.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 {
cryptfs.Warn.Printf("shrink doRead returned error: %v", err)
return status
}
}
// Truncate down to last complete block
f.fdLock.Lock()
err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
f.fdLock.Unlock()
if err != nil {
cryptfs.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.Lock()
r := fuse.ToStatus(f.fd.Chmod(os.FileMode(mode)))
f.fdLock.Unlock()
return r
}
func (f *file) Chown(uid uint32, gid uint32) fuse.Status {
f.fdLock.Lock()
r := fuse.ToStatus(f.fd.Chown(int(uid), int(gid)))
f.fdLock.Unlock()
return r
}
func (f *file) GetAttr(a *fuse.Attr) fuse.Status {
cryptfs.Debug.Printf("file.GetAttr()\n")
st := syscall.Stat_t{}
f.fdLock.Lock()
err := syscall.Fstat(int(f.fd.Fd()), &st)
f.fdLock.Unlock()
if err != nil {
return fuse.ToStatus(err)
}
a.FromStat(&st)
a.Size = f.cfs.CipherSizeToPlainSize(a.Size)
return fuse.OK
}
// Allocate - FUSE call, fallocate(2)
func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status {
cryptfs.Warn.Printf("Fallocate is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1\n")
return fuse.ENOSYS
}
const _UTIME_OMIT = ((1 << 30) - 2)
func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status {
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()
}
f.fdLock.Lock()
fn := fmt.Sprintf("/proc/self/fd/%d", f.fd.Fd())
err := syscall.UtimesNano(fn, ts)
f.fdLock.Unlock()
return fuse.ToStatus(err)
}