v2api: implement Create

1 files changed, 476 insertions, 0 deletions

diff --git a/internal/fusefrontend/file2.go b/internal/fusefrontend/file2.go
new file mode 100644
index 0000000..2882732
--- /dev/null
+++ b/internal/fusefrontend/file2.go
@@ -0,0 +1,476 @@
+package fusefrontend
+
+// FUSE operations on file handles
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/hanwen/go-fuse/v2/fuse"
+	"github.com/hanwen/go-fuse/v2/fuse/nodefs"
+
+	"github.com/rfjakob/gocryptfs/internal/contentenc"
+	"github.com/rfjakob/gocryptfs/internal/inomap"
+	"github.com/rfjakob/gocryptfs/internal/openfiletable"
+	"github.com/rfjakob/gocryptfs/internal/serialize_reads"
+	"github.com/rfjakob/gocryptfs/internal/stupidgcm"
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+var _ nodefs.File = &File{} // Verify that interface is implemented.
+
+// File - based on loopbackFile in go-fuse/fuse/nodefs/files.go
+type File2 struct {
+	fd *os.File
+	// Has Release() already been called on this file? This also means that the
+	// wlock entry has been freed, so let's not crash trying to access it.
+	// Due to concurrency, Release can overtake other operations. These will
+	// return EBADF in that case.
+	released bool
+	// 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 and sets "released" to true.
+	fdLock sync.RWMutex
+	// Content encryption helper
+	contentEnc *contentenc.ContentEnc
+	// Device and inode number uniquely identify the backing file
+	qIno inomap.QIno
+	// Entry in the open file table
+	fileTableEntry *openfiletable.Entry
+	// Store where the last byte was written
+	lastWrittenOffset int64
+	// The opCount is used to judge whether "lastWrittenOffset" is still
+	// guaranteed to be correct.
+	lastOpCount uint64
+	// Parent filesystem
+	rootNode *RootNode
+	// We embed a nodefs.NewDefaultFile() that returns ENOSYS for every operation we
+	// have not implemented. This prevents build breakage when the go-fuse library
+	// adds new methods to the nodefs.File interface.
+	nodefs.File
+}
+
+// NewFile returns a new go-fuse File instance.
+func NewFile2(fd *os.File, rn *RootNode, st *syscall.Stat_t) *File2 {
+	qi := inomap.QInoFromStat(st)
+	e := openfiletable.Register(qi)
+
+	return &File2{
+		fd:             fd,
+		contentEnc:     rn.contentEnc,
+		qIno:           qi,
+		fileTableEntry: e,
+		rootNode:       rn,
+		File:           nodefs.NewDefaultFile(),
+	}
+}
+
+// intFd - return the backing file descriptor as an integer.
+func (f *File2) intFd() int {
+	return int(f.fd.Fd())
+}
+
+// readFileID loads the file header from disk and extracts the file ID.
+// Returns io.EOF if the file is empty.
+func (f *File2) readFileID() ([]byte, error) {
+	// We read +1 byte to determine if the file has actual content
+	// and not only the header. A header-only file will be considered empty.
+	// This makes File ID poisoning more difficult.
+	readLen := contentenc.HeaderLen + 1
+	buf := make([]byte, readLen)
+	n, err := f.fd.ReadAt(buf, 0)
+	if err != nil {
+		if err == io.EOF && n != 0 {
+			tlog.Warn.Printf("readFileID %d: incomplete file, got %d instead of %d bytes",
+				f.qIno.Ino, n, readLen)
+			f.rootNode.reportMitigatedCorruption(fmt.Sprint(f.qIno.Ino))
+		}
+		return nil, err
+	}
+	buf = buf[:contentenc.HeaderLen]
+	h, err := contentenc.ParseHeader(buf)
+	if err != nil {
+		return nil, err
+	}
+	return h.ID, nil
+}
+
+// createHeader creates a new random header and writes it to disk.
+// Returns the new file ID.
+// The caller must hold fileIDLock.Lock().
+func (f *File2) createHeader() (fileID []byte, err error) {
+	h := contentenc.RandomHeader()
+	buf := h.Pack()
+	// Prevent partially written (=corrupt) header by preallocating the space beforehand
+	if !f.rootNode.args.NoPrealloc {
+		err = syscallcompat.EnospcPrealloc(f.intFd(), 0, contentenc.HeaderLen)
+		if err != nil {
+			if !syscallcompat.IsENOSPC(err) {
+				tlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.qIno.Ino, err.Error())
+			}
+			return nil, err
+		}
+	}
+	// Actually write header
+	_, err = f.fd.WriteAt(buf, 0)
+	if err != nil {
+		return nil, err
+	}
+	return h.ID, err
+}
+
+// doRead - read "length" plaintext bytes from plaintext offset "off" and append
+// to "dst".
+// 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() via doWrite() for Read-Modify-Write.
+func (f *File2) doRead(dst []byte, off uint64, length uint64) ([]byte, fuse.Status) {
+	// Get the file ID, either from the open file table, or from disk.
+	var fileID []byte
+	f.fileTableEntry.IDLock.Lock()
+	if f.fileTableEntry.ID != nil {
+		// Use the cached value in the file table
+		fileID = f.fileTableEntry.ID
+	} else {
+		// Not cached, we have to read it from disk.
+		var err error
+		fileID, err = f.readFileID()
+		if err != nil {
+			f.fileTableEntry.IDLock.Unlock()
+			if err == io.EOF {
+				// Empty file
+				return nil, fuse.OK
+			}
+			buf := make([]byte, 100)
+			n, _ := f.fd.ReadAt(buf, 0)
+			buf = buf[:n]
+			hexdump := hex.EncodeToString(buf)
+			tlog.Warn.Printf("doRead %d: corrupt header: %v\nFile hexdump (%d bytes): %s",
+				f.qIno.Ino, err, n, hexdump)
+			return nil, fuse.EIO
+		}
+		// Save into the file table
+		f.fileTableEntry.ID = fileID
+	}
+	f.fileTableEntry.IDLock.Unlock()
+	if fileID == nil {
+		log.Panicf("fileID=%v", fileID)
+	}
+	// Read the backing ciphertext in one go
+	blocks := f.contentEnc.ExplodePlainRange(off, length)
+	alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
+	skip := blocks[0].Skip
+	tlog.Debug.Printf("doRead: off=%d len=%d -> off=%d len=%d skip=%d\n",
+		off, length, alignedOffset, alignedLength, skip)
+
+	ciphertext := f.rootNode.contentEnc.CReqPool.Get()
+	ciphertext = ciphertext[:int(alignedLength)]
+	n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
+	if err != nil && err != io.EOF {
+		tlog.Warn.Printf("read: ReadAt: %s", err.Error())
+		return nil, fuse.ToStatus(err)
+	}
+	// The ReadAt came back empty. We can skip all the decryption and return early.
+	if n == 0 {
+		f.rootNode.contentEnc.CReqPool.Put(ciphertext)
+		return dst, fuse.OK
+	}
+	// Truncate ciphertext buffer down to actually read bytes
+	ciphertext = ciphertext[0:n]
+
+	firstBlockNo := blocks[0].BlockNo
+	tlog.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, fileID)
+	f.rootNode.contentEnc.CReqPool.Put(ciphertext)
+	if err != nil {
+		if f.rootNode.args.ForceDecode && err == stupidgcm.ErrAuth {
+			// We do not have the information which block was corrupt here anymore,
+			// but DecryptBlocks() has already logged it anyway.
+			tlog.Warn.Printf("doRead %d: off=%d len=%d: returning corrupt data due to forcedecode",
+				f.qIno.Ino, off, length)
+		} else {
+			curruptBlockNo := firstBlockNo + f.contentEnc.PlainOffToBlockNo(uint64(len(plaintext)))
+			tlog.Warn.Printf("doRead %d: corrupt block #%d: %v", f.qIno.Ino, curruptBlockNo, err)
+			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
+
+	out = append(dst, out...)
+	f.rootNode.contentEnc.PReqPool.Put(plaintext)
+
+	return out, fuse.OK
+}
+
+// Read - FUSE call
+func (f *File2) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fuse.Status) {
+	if len(buf) > fuse.MAX_KERNEL_WRITE {
+		// This would crash us due to our fixed-size buffer pool
+		tlog.Warn.Printf("Read: rejecting oversized request with EMSGSIZE, len=%d", len(buf))
+		return nil, fuse.Status(syscall.EMSGSIZE)
+	}
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	f.fileTableEntry.ContentLock.RLock()
+	defer f.fileTableEntry.ContentLock.RUnlock()
+
+	tlog.Debug.Printf("ino%d: FUSE Read: offset=%d length=%d", f.qIno.Ino, off, len(buf))
+	if f.rootNode.args.SerializeReads {
+		serialize_reads.Wait(off, len(buf))
+	}
+	out, status := f.doRead(buf[:0], uint64(off), uint64(len(buf)))
+	if f.rootNode.args.SerializeReads {
+		serialize_reads.Done()
+	}
+	if status != fuse.OK {
+		return nil, status
+	}
+	tlog.Debug.Printf("ino%d: Read: status %v, returning %d bytes", f.qIno.Ino, status, len(out))
+	return fuse.ReadResultData(out), status
+}
+
+// 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 necessary
+//
+// Called by Write() for normal writing,
+// and by Truncate() to rewrite the last file block.
+//
+// Empty writes do nothing and are allowed.
+func (f *File2) doWrite(data []byte, off int64) (uint32, fuse.Status) {
+	fileWasEmpty := false
+	// Get the file ID, create a new one if it does not exist yet.
+	var fileID []byte
+	// The caller has exclusively locked ContentLock, which blocks all other
+	// readers and writers. No need to take IDLock.
+	if f.fileTableEntry.ID != nil {
+		fileID = f.fileTableEntry.ID
+	} else {
+		// If the file ID is not cached, read it from disk
+		var err error
+		fileID, err = f.readFileID()
+		// Write a new file header if the file is empty
+		if err == io.EOF {
+			fileID, err = f.createHeader()
+			fileWasEmpty = true
+		}
+		if err != nil {
+			return 0, fuse.ToStatus(err)
+		}
+		f.fileTableEntry.ID = fileID
+	}
+	// Handle payload data
+	dataBuf := bytes.NewBuffer(data)
+	blocks := f.contentEnc.ExplodePlainRange(uint64(off), uint64(len(data)))
+	toEncrypt := make([][]byte, len(blocks))
+	for i, b := range blocks {
+		blockData := dataBuf.Next(int(b.Length))
+		// Incomplete block -> Read-Modify-Write
+		if b.IsPartial() {
+			// Read
+			oldData, status := f.doRead(nil, b.BlockPlainOff(), f.contentEnc.PlainBS())
+			if status != fuse.OK {
+				tlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.qIno.Ino, f.intFd(), status.String())
+				return 0, status
+			}
+			// Modify
+			blockData = f.contentEnc.MergeBlocks(oldData, blockData, int(b.Skip))
+			tlog.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData))
+		}
+		tlog.Debug.Printf("ino%d: Writing %d bytes to block #%d",
+			f.qIno.Ino, len(blockData), b.BlockNo)
+		// Write into the to-encrypt list
+		toEncrypt[i] = blockData
+	}
+	// Encrypt all blocks
+	ciphertext := f.contentEnc.EncryptBlocks(toEncrypt, blocks[0].BlockNo, f.fileTableEntry.ID)
+	// Preallocate so we cannot run out of space in the middle of the write.
+	// This prevents partially written (=corrupt) blocks.
+	var err error
+	cOff := int64(blocks[0].BlockCipherOff())
+	if !f.rootNode.args.NoPrealloc {
+		err = syscallcompat.EnospcPrealloc(f.intFd(), cOff, int64(len(ciphertext)))
+		if err != nil {
+			if !syscallcompat.IsENOSPC(err) {
+				tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %v", f.qIno.Ino, f.intFd(), err)
+			}
+			if fileWasEmpty {
+				// Kill the file header again
+				f.fileTableEntry.ID = nil
+				err2 := syscall.Ftruncate(f.intFd(), 0)
+				if err2 != nil {
+					tlog.Warn.Printf("ino%d fh%d: doWrite: rollback failed: %v", f.qIno.Ino, f.intFd(), err2)
+				}
+			}
+			return 0, fuse.ToStatus(err)
+		}
+	}
+	// Write
+	_, err = f.fd.WriteAt(ciphertext, cOff)
+	// Return memory to CReqPool
+	f.rootNode.contentEnc.CReqPool.Put(ciphertext)
+	if err != nil {
+		tlog.Warn.Printf("ino%d fh%d: doWrite: WriteAt off=%d len=%d failed: %v",
+			f.qIno.Ino, f.intFd(), cOff, len(ciphertext), err)
+		return 0, fuse.ToStatus(err)
+	}
+	return uint32(len(data)), fuse.OK
+}
+
+// isConsecutiveWrite returns true if the current write
+// directly (in time and space) follows the last write.
+// This is an optimisation for streaming writes on NFS where a
+// Stat() call is very expensive.
+// The caller must "wlock.lock(f.devIno.ino)" otherwise this check would be racy.
+func (f *File2) isConsecutiveWrite(off int64) bool {
+	opCount := openfiletable.WriteOpCount()
+	return opCount == f.lastOpCount+1 && off == f.lastWrittenOffset+1
+}
+
+// Write - FUSE call
+//
+// If the write creates a hole, pads the file to the next block boundary.
+func (f *File2) Write(data []byte, off int64) (uint32, fuse.Status) {
+	if len(data) > fuse.MAX_KERNEL_WRITE {
+		// This would crash us due to our fixed-size buffer pool
+		tlog.Warn.Printf("Write: rejecting oversized request with EMSGSIZE, len=%d", len(data))
+		return 0, fuse.Status(syscall.EMSGSIZE)
+	}
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+	if f.released {
+		// The file descriptor has been closed concurrently
+		tlog.Warn.Printf("ino%d fh%d: Write on released file", f.qIno.Ino, f.intFd())
+		return 0, fuse.EBADF
+	}
+	f.fileTableEntry.ContentLock.Lock()
+	defer f.fileTableEntry.ContentLock.Unlock()
+	tlog.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.qIno.Ino, off, len(data))
+	// If the write creates a file hole, we have to zero-pad the last block.
+	// But if the write directly follows an earlier write, it cannot create a
+	// hole, and we can save one Stat() call.
+	if !f.isConsecutiveWrite(off) {
+		status := f.writePadHole(off)
+		if !status.Ok() {
+			return 0, status
+		}
+	}
+	n, status := f.doWrite(data, off)
+	if status.Ok() {
+		f.lastOpCount = openfiletable.WriteOpCount()
+		f.lastWrittenOffset = off + int64(len(data)) - 1
+	}
+	return n, status
+}
+
+// Release - FUSE call, close file
+func (f *File2) Release() {
+	f.fdLock.Lock()
+	if f.released {
+		log.Panicf("ino%d fh%d: double release", f.qIno.Ino, f.intFd())
+	}
+	f.released = true
+	openfiletable.Unregister(f.qIno)
+	f.fd.Close()
+	f.fdLock.Unlock()
+}
+
+// Flush - FUSE call
+func (f *File2) 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(f.intFd())
+
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	err = syscall.Close(newFd)
+	return fuse.ToStatus(err)
+}
+
+// Fsync FUSE call
+func (f *File2) Fsync(flags int) (code fuse.Status) {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	return fuse.ToStatus(syscall.Fsync(f.intFd()))
+}
+
+// Chmod FUSE call
+func (f *File2) Chmod(mode uint32) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	// os.File.Chmod goes through the "syscallMode" translation function that messes
+	// up the suid and sgid bits. So use syscall.Fchmod directly.
+	err := syscall.Fchmod(f.intFd(), mode)
+	return fuse.ToStatus(err)
+}
+
+// Chown FUSE call
+func (f *File2) Chown(uid uint32, gid uint32) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	return fuse.ToStatus(f.fd.Chown(int(uid), int(gid)))
+}
+
+// GetAttr FUSE call (like stat)
+func (f *File2) GetAttr(a *fuse.Attr) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+
+	tlog.Debug.Printf("file.GetAttr()")
+	st := syscall.Stat_t{}
+	err := syscall.Fstat(f.intFd(), &st)
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	f.rootNode.inoMap.TranslateStat(&st)
+	a.FromStat(&st)
+	a.Size = f.contentEnc.CipherSizeToPlainSize(a.Size)
+	if f.rootNode.args.ForceOwner != nil {
+		a.Owner = *f.rootNode.args.ForceOwner
+	}
+
+	return fuse.OK
+}
+
+// Utimens FUSE call
+func (f *File2) Utimens(a *time.Time, m *time.Time) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+	err := syscallcompat.FutimesNano(f.intFd(), a, m)
+	return fuse.ToStatus(err)
+}