268e0484e2
We cannot return less data than requested to the kernel!
From https://libfuse.github.io/doxygen/structfuse__operations.html:
Read should return exactly the number of bytes
requested except on EOF or error, otherwise the
rest of the data will be substituted with
zeroes.
Reverts commit 3009ec9852 minus
the formatting improvements we want to keep.
Fixes https://github.com/rfjakob/gocryptfs/issues/147
Reopens https://github.com/rfjakob/gocryptfs/issues/145
456 lines
14 KiB
Go
456 lines
14 KiB
Go
package fusefrontend
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// FUSE operations on file handles
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import (
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"bytes"
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"io"
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"log"
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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/internal/contentenc"
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"github.com/rfjakob/gocryptfs/internal/openfiletable"
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"github.com/rfjakob/gocryptfs/internal/serialize_reads"
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"github.com/rfjakob/gocryptfs/internal/stupidgcm"
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"github.com/rfjakob/gocryptfs/internal/syscallcompat"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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var _ nodefs.File = &file{} // Verify that interface is implemented.
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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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// Has Release() already been called on this file? This also means that the
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// wlock entry has been freed, so let's not crash trying to access it.
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// Due to concurrency, Release can overtake other operations. These will
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// return EBADF in that case.
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released bool
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// fdLock prevents the fd to be closed while we are in the middle of
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// an operation.
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// Every FUSE entrypoint should RLock(). The only user of Lock() is
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// Release(), which closes the fd and sets "released" to true.
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fdLock sync.RWMutex
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// Content encryption helper
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contentEnc *contentenc.ContentEnc
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// Device and inode number uniquely identify the backing file
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qIno openfiletable.QIno
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// Entry in the open file table
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fileTableEntry *openfiletable.Entry
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// go-fuse nodefs.loopbackFile
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loopbackFile nodefs.File
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// Store where the last byte was written
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lastWrittenOffset int64
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// The opCount is used to judge whether "lastWrittenOffset" is still
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// guaranteed to be correct.
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lastOpCount uint64
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// Parent filesystem
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fs *FS
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// We embed a nodefs.NewDefaultFile() that returns ENOSYS for every operation we
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// have not implemented. This prevents build breakage when the go-fuse library
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// adds new methods to the nodefs.File interface.
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nodefs.File
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}
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// NewFile returns a new go-fuse File instance.
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func NewFile(fd *os.File, fs *FS) (nodefs.File, fuse.Status) {
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var st syscall.Stat_t
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err := syscall.Fstat(int(fd.Fd()), &st)
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if err != nil {
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tlog.Warn.Printf("NewFile: Fstat on fd %d failed: %v\n", fd.Fd(), err)
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return nil, fuse.ToStatus(err)
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}
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qi := openfiletable.QInoFromStat(&st)
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e := openfiletable.Register(qi)
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return &file{
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fd: fd,
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contentEnc: fs.contentEnc,
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qIno: qi,
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fileTableEntry: e,
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loopbackFile: nodefs.NewLoopbackFile(fd),
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fs: fs,
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File: nodefs.NewDefaultFile(),
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}, fuse.OK
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}
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// intFd - return the backing file descriptor as an integer. Used for debug
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// messages.
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func (f *file) intFd() int {
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return int(f.fd.Fd())
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}
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// readFileID loads the file header from disk and extracts the file ID.
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// Returns io.EOF if the file is empty.
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func (f *file) readFileID() ([]byte, error) {
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// We read +1 byte to determine if the file has actual content
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// and not only the header. A header-only file will be considered empty.
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// This makes File ID poisoning more difficult.
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readLen := contentenc.HeaderLen + 1
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buf := make([]byte, readLen)
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n, err := f.fd.ReadAt(buf, 0)
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if err != nil {
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if err == io.EOF && n != 0 {
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tlog.Warn.Printf("ino%d: readFileID: incomplete file, got %d instead of %d bytes",
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f.qIno.Ino, n, readLen)
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}
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return nil, err
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}
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buf = buf[:contentenc.HeaderLen]
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h, err := contentenc.ParseHeader(buf)
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if err != nil {
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return nil, err
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}
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return h.ID, nil
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}
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// createHeader creates a new random header and writes it to disk.
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// Returns the new file ID.
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// The caller must hold fileIDLock.Lock().
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func (f *file) createHeader() (fileID []byte, err error) {
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h := contentenc.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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if !f.fs.args.NoPrealloc {
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err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), 0, contentenc.HeaderLen)
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if err != nil {
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tlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.qIno.Ino, err.Error())
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return nil, err
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}
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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 nil, err
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}
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return h.ID, err
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}
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// doRead - read "length" plaintext bytes from plaintext offset "off" and append
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// to "dst".
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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(dst []byte, off uint64, length uint64) ([]byte, fuse.Status) {
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// Make sure we have the file ID.
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f.fileTableEntry.HeaderLock.RLock()
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if f.fileTableEntry.ID == nil {
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f.fileTableEntry.HeaderLock.RUnlock()
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// Yes, somebody else may take the lock before we can. This will get
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// the header read twice, but causes no harm otherwise.
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f.fileTableEntry.HeaderLock.Lock()
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tmpID, err := f.readFileID()
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if err == io.EOF {
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f.fileTableEntry.HeaderLock.Unlock()
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return nil, fuse.OK
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}
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if err != nil {
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f.fileTableEntry.HeaderLock.Unlock()
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return nil, fuse.ToStatus(err)
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}
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f.fileTableEntry.ID = tmpID
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// Downgrade the lock.
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f.fileTableEntry.HeaderLock.Unlock()
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// The file ID may change in here. This does no harm because we
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// re-read it after the RLock().
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f.fileTableEntry.HeaderLock.RLock()
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}
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fileID := f.fileTableEntry.ID
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// Read the backing ciphertext in one go
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blocks := f.contentEnc.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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tlog.Debug.Printf("doRead: off=%d len=%d -> off=%d len=%d skip=%d\n",
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off, length, alignedOffset, alignedLength, skip)
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ciphertext := f.fs.contentEnc.CReqPool.Get()
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ciphertext = ciphertext[:int(alignedLength)]
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n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
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// We don't care if the file ID changes after we have read the data. Drop the lock.
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f.fileTableEntry.HeaderLock.RUnlock()
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if err != nil && err != io.EOF {
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tlog.Warn.Printf("read: ReadAt: %s", err.Error())
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return nil, fuse.ToStatus(err)
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}
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// The ReadAt came back empty. We can skip all the decryption and return early.
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if n == 0 {
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f.fs.contentEnc.CReqPool.Put(ciphertext)
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return dst, fuse.OK
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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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tlog.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.contentEnc.DecryptBlocks(ciphertext, firstBlockNo, fileID)
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f.fs.contentEnc.CReqPool.Put(ciphertext)
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if err != nil {
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if f.fs.args.ForceDecode && err == stupidgcm.ErrAuth {
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// We do not have the information which block was corrupt here anymore,
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// but DecryptBlocks() has already logged it anyway.
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tlog.Warn.Printf("ino%d: doRead off=%d len=%d: returning corrupt data due to forcedecode",
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f.qIno.Ino, off, length)
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} else {
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curruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext)))
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tlog.Warn.Printf("ino%d: doRead: corrupt block #%d: %v", f.qIno.Ino, curruptBlockNo, err)
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return nil, fuse.EIO
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}
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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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out = append(dst, out...)
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f.fs.contentEnc.PReqPool.Put(plaintext)
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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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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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tlog.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.qIno.Ino, len(buf), off)
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if f.fs.args.SerializeReads {
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serialize_reads.Wait(off, len(buf))
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}
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out, status := f.doRead(buf[:0], uint64(off), uint64(len(buf)))
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if f.fs.args.SerializeReads {
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serialize_reads.Done()
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}
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if status == fuse.EIO {
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tlog.Warn.Printf("ino%d: Read: returning EIO, offset=%d, length=%d", f.qIno.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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tlog.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.qIno.Ino, status, len(out))
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return fuse.ReadResultData(out), status
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}
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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 necessary
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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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//
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// Empty writes do nothing and are allowed.
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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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f.fileTableEntry.HeaderLock.RLock()
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if f.fileTableEntry.ID == nil {
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f.fileTableEntry.HeaderLock.RUnlock()
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// Somebody else may write the header here, but this would do no harm.
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f.fileTableEntry.HeaderLock.Lock()
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tmpID, err := f.readFileID()
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if err == io.EOF {
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tmpID, err = f.createHeader()
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}
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if err != nil {
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f.fileTableEntry.HeaderLock.Unlock()
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return 0, fuse.ToStatus(err)
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}
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f.fileTableEntry.ID = tmpID
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f.fileTableEntry.HeaderLock.Unlock()
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// The file ID may change in here. This does no harm because we
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// re-read it after the RLock().
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f.fileTableEntry.HeaderLock.RLock()
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}
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defer f.fileTableEntry.HeaderLock.RUnlock()
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// Handle payload data
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dataBuf := bytes.NewBuffer(data)
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blocks := f.contentEnc.ExplodePlainRange(uint64(off), uint64(len(data)))
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toEncrypt := make([][]byte, len(blocks))
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for i, 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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oldData, status := f.doRead(nil, b.BlockPlainOff(), f.contentEnc.PlainBS())
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if status != fuse.OK {
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tlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.qIno.Ino, f.intFd(), status.String())
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return 0, status
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}
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// Modify
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blockData = f.contentEnc.MergeBlocks(oldData, blockData, int(b.Skip))
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tlog.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData))
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}
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tlog.Debug.Printf("ino%d: Writing %d bytes to block #%d",
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f.qIno.Ino, uint64(len(blockData))-f.contentEnc.BlockOverhead(), b.BlockNo)
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// Write into the to-encrypt list
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toEncrypt[i] = blockData
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}
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// Encrypt all blocks
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ciphertext := f.contentEnc.EncryptBlocks(toEncrypt, blocks[0].BlockNo, f.fileTableEntry.ID)
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// Preallocate so we cannot run out of space in the middle of the write.
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// This prevents partially written (=corrupt) blocks.
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var err error
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cOff := int64(blocks[0].BlockCipherOff())
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if !f.fs.args.NoPrealloc {
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err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), cOff, int64(len(ciphertext)))
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if err != nil {
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tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %s", f.qIno.Ino, f.intFd(), err.Error())
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return 0, fuse.ToStatus(err)
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}
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}
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// Write
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_, err = f.fd.WriteAt(ciphertext, cOff)
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// Return memory to CReqPool
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f.fs.contentEnc.CReqPool.Put(ciphertext)
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if err != nil {
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tlog.Warn.Printf("doWrite: Write failed: %s", err.Error())
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return 0, fuse.ToStatus(err)
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}
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return uint32(len(data)), fuse.OK
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}
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// isConsecutiveWrite returns true if the current write
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// directly (in time and space) follows the last write.
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// This is an optimisation for streaming writes on NFS where a
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// Stat() call is very expensive.
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// The caller must "wlock.lock(f.devIno.ino)" otherwise this check would be racy.
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func (f *file) isConsecutiveWrite(off int64) bool {
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opCount := openfiletable.WriteOpCount()
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return opCount == f.lastOpCount+1 && off == f.lastWrittenOffset+1
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}
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// Write - FUSE call
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//
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// If the write creates a hole, pads the file to the next block boundary.
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func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) {
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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if f.released {
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// The file descriptor has been closed concurrently, which also means
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// the wlock has been freed. Exit here so we don't crash trying to access
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// it.
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tlog.Warn.Printf("ino%d fh%d: Write on released file", f.qIno.Ino, f.intFd())
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return 0, fuse.EBADF
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}
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f.fileTableEntry.ContentLock.Lock()
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defer f.fileTableEntry.ContentLock.Unlock()
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tlog.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.qIno.Ino, off, len(data))
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// If the write creates a file hole, we have to zero-pad the last block.
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// But if the write directly follows an earlier write, it cannot create a
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// hole, and we can save one Stat() call.
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if !f.isConsecutiveWrite(off) {
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status := f.writePadHole(off)
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if !status.Ok() {
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return 0, status
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}
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}
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n, status := f.doWrite(data, off)
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if status.Ok() {
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f.lastOpCount = openfiletable.WriteOpCount()
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f.lastWrittenOffset = off + int64(len(data)) - 1
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}
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return n, status
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}
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// Release - FUSE call, close file
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func (f *file) Release() {
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f.fdLock.Lock()
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if f.released {
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log.Panicf("ino%d fh%d: double release", f.qIno.Ino, f.intFd())
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}
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f.fd.Close()
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f.released = true
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f.fdLock.Unlock()
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openfiletable.Unregister(f.qIno)
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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.RLock()
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defer f.fdLock.RUnlock()
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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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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.RLock()
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defer f.fdLock.RUnlock()
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return fuse.ToStatus(syscall.Fsync(int(f.fd.Fd())))
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}
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func (f *file) Chmod(mode uint32) fuse.Status {
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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// os.File.Chmod goes through the "syscallMode" translation function that messes
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// up the suid and sgid bits. So use syscall.Fchmod directly.
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err := syscall.Fchmod(f.intFd(), mode)
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return fuse.ToStatus(err)
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}
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func (f *file) Chown(uid uint32, gid uint32) fuse.Status {
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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return fuse.ToStatus(f.fd.Chown(int(uid), int(gid)))
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}
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func (f *file) GetAttr(a *fuse.Attr) fuse.Status {
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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tlog.Debug.Printf("file.GetAttr()")
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st := syscall.Stat_t{}
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err := syscall.Fstat(int(f.fd.Fd()), &st)
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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.contentEnc.CipherSizeToPlainSize(a.Size)
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if f.fs.args.ForceOwner != nil {
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a.Owner = *f.fs.args.ForceOwner
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}
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return fuse.OK
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}
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func (f *file) Utimens(a *time.Time, m *time.Time) fuse.Status {
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
|
|
return f.loopbackFile.Utimens(a, m)
|
|
}
|