2f32114bd3
At the moment, FUSE writes to a single file are serialized by the kernel. However, it is unclear if this is guaranteed behaviour or may change in the future. This patch adds our own per-inode write lock to rule out races regardless of kernel behavoir.
486 lines
12 KiB
Go
486 lines
12 KiB
Go
package pathfs_frontend
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// FUSE operations on file handles
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import (
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"bytes"
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"fmt"
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"io"
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"os"
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"sync"
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"syscall"
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"time"
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"github.com/hanwen/go-fuse/fuse"
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"github.com/hanwen/go-fuse/fuse/nodefs"
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"github.com/rfjakob/gocryptfs/cryptfs"
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)
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// File - based on loopbackFile in go-fuse/fuse/nodefs/files.go
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type file struct {
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fd *os.File
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// os.File is not threadsafe. Although fd themselves are
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// constant during the lifetime of an open file, the OS may
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// reuse the fd number after it is closed. When open races
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// with another close, they may lead to confusion as which
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// file gets written in the end.
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fdLock sync.Mutex
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// Was the file opened O_WRONLY?
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writeOnly bool
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// Parent CryptFS
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cfs *cryptfs.CryptFS
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// Inode number
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ino uint64
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// File header
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header *cryptfs.FileHeader
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}
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func NewFile(fd *os.File, writeOnly bool, cfs *cryptfs.CryptFS) nodefs.File {
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var st syscall.Stat_t
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syscall.Fstat(int(fd.Fd()), &st)
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wlock.register(st.Ino)
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return &file{
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fd: fd,
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writeOnly: writeOnly,
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cfs: cfs,
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ino: st.Ino,
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}
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}
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func (f *file) InnerFile() nodefs.File {
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return nil
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}
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func (f *file) SetInode(n *nodefs.Inode) {
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}
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// readHeader - load the file header from disk
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//
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// Returns io.EOF if the file is empty
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func (f *file) readHeader() error {
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buf := make([]byte, cryptfs.HEADER_LEN)
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_, err := f.fd.ReadAt(buf, 0)
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if err != nil {
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return err
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}
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h, err := cryptfs.ParseHeader(buf)
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if err != nil {
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return err
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}
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f.header = h
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return nil
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}
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// createHeader - create a new random header and write it to disk
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func (f *file) createHeader() error {
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h := cryptfs.RandomHeader()
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buf := h.Pack()
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// Prevent partially written (=corrupt) header by preallocating the space beforehand
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f.fdLock.Lock()
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defer f.fdLock.Unlock()
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err := prealloc(int(f.fd.Fd()), 0, cryptfs.HEADER_LEN)
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if err != nil {
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cryptfs.Warn.Printf("createHeader: fallocateRetry failed: %s\n", err.Error())
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return err
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}
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// Actually write header
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_, err = f.fd.WriteAt(buf, 0)
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if err != nil {
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return err
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}
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f.header = h
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return nil
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}
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func (f *file) String() string {
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return fmt.Sprintf("cryptFile(%s)", f.fd.Name())
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}
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// doRead - returns "length" plaintext bytes from plaintext offset "off".
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// Arguments "length" and "off" do not have to be block-aligned.
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//
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// doRead reads the corresponding ciphertext blocks from disk, decrypts them and
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// returns the requested part of the plaintext.
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//
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// Called by Read() for normal reading,
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// by Write() and Truncate() for Read-Modify-Write
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func (f *file) doRead(off uint64, length uint64) ([]byte, fuse.Status) {
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// Read file header
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if f.header == nil {
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err := f.readHeader()
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if err == io.EOF {
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return nil, fuse.OK
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}
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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}
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// Read the backing ciphertext in one go
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blocks := f.cfs.ExplodePlainRange(off, length)
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alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
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skip := blocks[0].Skip
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cryptfs.Debug.Printf("JointCiphertextRange(%d, %d) -> %d, %d, %d", off, length, alignedOffset, alignedLength, skip)
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ciphertext := make([]byte, int(alignedLength))
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f.fdLock.Lock()
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n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
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f.fdLock.Unlock()
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if err != nil && err != io.EOF {
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cryptfs.Warn.Printf("read: ReadAt: %s", err.Error())
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return nil, fuse.ToStatus(err)
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}
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// Truncate ciphertext buffer down to actually read bytes
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ciphertext = ciphertext[0:n]
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firstBlockNo := blocks[0].BlockNo
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cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d", alignedOffset, firstBlockNo, alignedLength, n)
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// Decrypt it
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plaintext, err := f.cfs.DecryptBlocks(ciphertext, firstBlockNo, f.header.Id)
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if err != nil {
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curruptBlockNo := firstBlockNo + f.cfs.PlainOffToBlockNo(uint64(len(plaintext)))
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cipherOff := f.cfs.BlockNoToCipherOff(curruptBlockNo)
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plainOff := f.cfs.BlockNoToPlainOff(curruptBlockNo)
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cryptfs.Warn.Printf("ino%d: doRead: corrupt block #%d (plainOff=%d, cipherOff=%d)",
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f.ino, curruptBlockNo, plainOff, cipherOff)
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return nil, fuse.EIO
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}
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// Crop down to the relevant part
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var out []byte
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lenHave := len(plaintext)
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lenWant := int(skip + length)
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if lenHave > lenWant {
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out = plaintext[skip:lenWant]
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} else if lenHave > int(skip) {
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out = plaintext[skip:lenHave]
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}
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// else: out stays empty, file was smaller than the requested offset
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return out, fuse.OK
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}
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// Read - FUSE call
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func (f *file) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fuse.Status) {
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cryptfs.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.ino, len(buf), off)
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if f.writeOnly {
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cryptfs.Warn.Printf("ino%d: Tried to read from write-only file", f.ino)
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return nil, fuse.EBADF
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}
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out, status := f.doRead(uint64(off), uint64(len(buf)))
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if status == fuse.EIO {
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cryptfs.Warn.Printf("ino%d: Read failed with EIO, offset=%d, length=%d", f.ino, len(buf), off)
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}
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if status != fuse.OK {
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return nil, status
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}
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cryptfs.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.ino, status, len(out))
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return fuse.ReadResultData(out), status
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}
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const FALLOC_FL_KEEP_SIZE = 0x01
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// doWrite - encrypt "data" and write it to plaintext offset "off"
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//
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// Arguments do not have to be block-aligned, read-modify-write is
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// performed internally as neccessary
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//
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// Called by Write() for normal writing,
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// and by Truncate() to rewrite the last file block.
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func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
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// Read header from disk, create a new one if the file is empty
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if f.header == nil {
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err := f.readHeader()
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if err == io.EOF {
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err = f.createHeader()
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}
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if err != nil {
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return 0, fuse.ToStatus(err)
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}
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}
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var written uint32
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status := fuse.OK
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dataBuf := bytes.NewBuffer(data)
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blocks := f.cfs.ExplodePlainRange(uint64(off), uint64(len(data)))
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for _, b := range blocks {
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blockData := dataBuf.Next(int(b.Length))
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// Incomplete block -> Read-Modify-Write
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if b.IsPartial() {
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// Read
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o, _ := b.PlaintextRange()
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oldData, status := f.doRead(o, f.cfs.PlainBS())
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if status != fuse.OK {
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cryptfs.Warn.Printf("RMW read failed: %s", status.String())
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return written, status
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}
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// Modify
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blockData = f.cfs.MergeBlocks(oldData, blockData, int(b.Skip))
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cryptfs.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData))
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}
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// Encrypt
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blockOffset, blockLen := b.CiphertextRange()
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blockData = f.cfs.EncryptBlock(blockData, b.BlockNo, f.header.Id)
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cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d",
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f.ino, uint64(len(blockData))-f.cfs.BlockOverhead(), b.BlockNo)
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// Prevent partially written (=corrupt) blocks by preallocating the space beforehand
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f.fdLock.Lock()
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err := prealloc(int(f.fd.Fd()), int64(blockOffset), int64(blockLen))
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f.fdLock.Unlock()
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if err != nil {
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cryptfs.Warn.Printf("doWrite: fallocateRetry failed: %s", err.Error())
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status = fuse.ToStatus(err)
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break
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}
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// Write
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f.fdLock.Lock()
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_, err = f.fd.WriteAt(blockData, int64(blockOffset))
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f.fdLock.Unlock()
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if err != nil {
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cryptfs.Warn.Printf("doWrite: Write failed: %s", err.Error())
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status = fuse.ToStatus(err)
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break
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}
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written += uint32(b.Length)
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}
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return written, status
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}
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// Write - FUSE call
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func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) {
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cryptfs.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.ino, off, len(data))
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wlock.lock(f.ino)
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defer wlock.unlock(f.ino)
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fi, err := f.fd.Stat()
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if err != nil {
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cryptfs.Warn.Printf("Write: Fstat failed: %v", err)
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return 0, fuse.ToStatus(err)
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}
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plainSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size()))
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if f.createsHole(plainSize, off) {
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status := f.zeroPad(plainSize)
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if status != fuse.OK {
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cryptfs.Warn.Printf("zeroPad returned error %v", status)
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return 0, status
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}
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}
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return f.doWrite(data, off)
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}
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// Release - FUSE call, forget file
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func (f *file) Release() {
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f.fdLock.Lock()
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f.fd.Close()
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f.fdLock.Unlock()
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wlock.unregister(f.ino)
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}
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// Flush - FUSE call
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func (f *file) Flush() fuse.Status {
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f.fdLock.Lock()
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// Since Flush() may be called for each dup'd fd, we don't
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// want to really close the file, we just want to flush. This
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// is achieved by closing a dup'd fd.
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newFd, err := syscall.Dup(int(f.fd.Fd()))
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f.fdLock.Unlock()
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if err != nil {
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return fuse.ToStatus(err)
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}
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err = syscall.Close(newFd)
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return fuse.ToStatus(err)
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}
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func (f *file) Fsync(flags int) (code fuse.Status) {
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f.fdLock.Lock()
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r := fuse.ToStatus(syscall.Fsync(int(f.fd.Fd())))
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f.fdLock.Unlock()
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return r
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}
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// Truncate - FUSE call
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func (f *file) Truncate(newSize uint64) fuse.Status {
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wlock.lock(f.ino)
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defer wlock.unlock(f.ino)
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// Common case first: Truncate to zero
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if newSize == 0 {
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f.fdLock.Lock()
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err := syscall.Ftruncate(int(f.fd.Fd()), 0)
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f.fdLock.Unlock()
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if err != nil {
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cryptfs.Warn.Printf("Ftruncate(fd, 0) returned error: %v", err)
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return fuse.ToStatus(err)
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}
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// Truncate to zero kills the file header
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f.header = nil
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return fuse.OK
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}
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// We need the old file size to determine if we are growing or shrinking
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// the file
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fi, err := f.fd.Stat()
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if err != nil {
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cryptfs.Warn.Printf("Truncate: Fstat failed: %v", err)
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return fuse.ToStatus(err)
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}
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oldSize := f.cfs.CipherSizeToPlainSize(uint64(fi.Size()))
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{
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oldB := float32(oldSize) / float32(f.cfs.PlainBS())
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newB := float32(newSize) / float32(f.cfs.PlainBS())
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cryptfs.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)", f.ino, oldB, newB, oldSize, newSize)
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}
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// File grows
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if newSize > oldSize {
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// File was empty, create new header
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if oldSize == 0 {
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err := f.createHeader()
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if err != nil {
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return fuse.ToStatus(err)
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}
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}
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blocks := f.cfs.ExplodePlainRange(oldSize, newSize-oldSize)
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for _, b := range blocks {
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// First and last block may be partial
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if b.IsPartial() {
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off, _ := b.PlaintextRange()
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off += b.Skip
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_, status := f.doWrite(make([]byte, b.Length), int64(off))
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if status != fuse.OK {
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return status
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}
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} else {
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off, length := b.CiphertextRange()
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f.fdLock.Lock()
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err := syscall.Ftruncate(int(f.fd.Fd()), int64(off+length))
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f.fdLock.Unlock()
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if err != nil {
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cryptfs.Warn.Printf("grow Ftruncate returned error: %v", err)
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return fuse.ToStatus(err)
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}
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}
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}
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return fuse.OK
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} else {
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// File shrinks
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blockNo := f.cfs.PlainOffToBlockNo(newSize)
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cipherOff := f.cfs.BlockNoToCipherOff(blockNo)
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plainOff := f.cfs.BlockNoToPlainOff(blockNo)
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lastBlockLen := newSize - plainOff
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var data []byte
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if lastBlockLen > 0 {
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var status fuse.Status
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data, status = f.doRead(plainOff, lastBlockLen)
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if status != fuse.OK {
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cryptfs.Warn.Printf("shrink doRead returned error: %v", err)
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return status
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}
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}
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// Truncate down to last complete block
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f.fdLock.Lock()
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err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
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f.fdLock.Unlock()
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if err != nil {
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cryptfs.Warn.Printf("shrink Ftruncate returned error: %v", err)
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return fuse.ToStatus(err)
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}
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// Append partial block
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if lastBlockLen > 0 {
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_, status := f.doWrite(data, int64(plainOff))
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return status
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}
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return fuse.OK
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}
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}
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func (f *file) Chmod(mode uint32) fuse.Status {
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f.fdLock.Lock()
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r := fuse.ToStatus(f.fd.Chmod(os.FileMode(mode)))
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f.fdLock.Unlock()
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return r
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}
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func (f *file) Chown(uid uint32, gid uint32) fuse.Status {
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f.fdLock.Lock()
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r := fuse.ToStatus(f.fd.Chown(int(uid), int(gid)))
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f.fdLock.Unlock()
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return r
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}
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func (f *file) GetAttr(a *fuse.Attr) fuse.Status {
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cryptfs.Debug.Printf("file.GetAttr()")
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st := syscall.Stat_t{}
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f.fdLock.Lock()
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err := syscall.Fstat(int(f.fd.Fd()), &st)
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f.fdLock.Unlock()
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if err != nil {
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return fuse.ToStatus(err)
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}
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a.FromStat(&st)
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a.Size = f.cfs.CipherSizeToPlainSize(a.Size)
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return fuse.OK
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}
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// Allocate - FUSE call, fallocate(2)
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func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status {
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cryptfs.Warn.Printf("Fallocate is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1")
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return fuse.ENOSYS
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}
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const _UTIME_OMIT = ((1 << 30) - 2)
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func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status {
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ts := make([]syscall.Timespec, 2)
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if a == nil {
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ts[0].Nsec = _UTIME_OMIT
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} else {
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ts[0].Sec = a.Unix()
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}
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if m == nil {
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ts[1].Nsec = _UTIME_OMIT
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} else {
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ts[1].Sec = m.Unix()
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}
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f.fdLock.Lock()
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fn := fmt.Sprintf("/proc/self/fd/%d", f.fd.Fd())
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err := syscall.UtimesNano(fn, ts)
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f.fdLock.Unlock()
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return fuse.ToStatus(err)
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}
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