libgocryptfs/internal/fusefrontend/node_dir_ops.go

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package fusefrontend
import (
"context"
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"fmt"
"io"
"runtime"
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"syscall"
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"golang.org/x/sys/unix"
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"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/internal/configfile"
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"github.com/rfjakob/gocryptfs/internal/cryptocore"
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"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const dsStoreName = ".DS_Store"
// haveDsstore return true if one of the entries in "names" is ".DS_Store".
func haveDsstore(entries []fuse.DirEntry) bool {
for _, e := range entries {
if e.Name == dsStoreName {
return true
}
}
return false
}
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// mkdirWithIv - create a new directory and corresponding diriv file. dirfd
// should be a handle to the parent directory, cName is the name of the new
// directory and mode specifies the access permissions to use.
// If DeterministicNames is set, the diriv file is NOT created.
func (n *Node) mkdirWithIv(dirfd int, cName string, mode uint32, context *fuse.Context) error {
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rn := n.rootNode()
if rn.args.DeterministicNames {
return syscallcompat.MkdiratUser(dirfd, cName, mode, context)
}
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// Between the creation of the directory and the creation of gocryptfs.diriv
// the directory is inconsistent. Take the lock to prevent other readers
// from seeing it.
rn.dirIVLock.Lock()
defer rn.dirIVLock.Unlock()
err := syscallcompat.MkdiratUser(dirfd, cName, mode, context)
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if err != nil {
return err
}
dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_DIRECTORY|syscall.O_NOFOLLOW|syscallcompat.O_PATH, 0)
if err == nil {
// Create gocryptfs.diriv
err = nametransform.WriteDirIVAt(dirfd2)
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syscall.Close(dirfd2)
}
if err != nil {
// Delete inconsistent directory (missing gocryptfs.diriv!)
err2 := syscallcompat.Unlinkat(dirfd, cName, unix.AT_REMOVEDIR)
if err2 != nil {
tlog.Warn.Printf("mkdirWithIv: rollback failed: %v", err2)
}
}
return err
}
// Mkdir - FUSE call. Create a directory at "newPath" with permissions "mode".
//
// Symlink-safe through use of Mkdirat().
func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.EntryOut) (*fs.Inode, syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return nil, errno
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}
defer syscall.Close(dirfd)
rn := n.rootNode()
var context *fuse.Context
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if rn.args.PreserveOwner {
context = toFuseCtx(ctx)
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}
var st syscall.Stat_t
if rn.args.PlaintextNames {
err := syscallcompat.MkdiratUser(dirfd, cName, mode, context)
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if err != nil {
return nil, fs.ToErrno(err)
}
var ust unix.Stat_t
err = syscallcompat.Fstatat(dirfd, cName, &ust, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
return nil, fs.ToErrno(err)
}
st = syscallcompat.Unix2syscall(ust)
// Create child node & return
ch := n.newChild(ctx, &st, out)
return ch, 0
}
// We need write and execute permissions to create gocryptfs.diriv.
// Also, we need read permissions to open the directory (to avoid
// race-conditions between getting and setting the mode).
origMode := mode
mode = mode | 0700
// Handle long file name
if nametransform.IsLongContent(cName) {
// Create ".name"
err := rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
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if err != nil {
return nil, fs.ToErrno(err)
}
// Create directory & rollback .name file on error
err = rn.mkdirWithIv(dirfd, cName, mode, context)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
return nil, fs.ToErrno(err)
}
} else {
err := rn.mkdirWithIv(dirfd, cName, mode, context)
if err != nil {
return nil, fs.ToErrno(err)
}
}
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// Fill `st`
fd, err := syscallcompat.Openat(dirfd, cName,
syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Openat failed: %v", cName, err)
return nil, fs.ToErrno(err)
}
defer syscall.Close(fd)
err = syscall.Fstat(fd, &st)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fstat failed: %v", cName, err)
return nil, fs.ToErrno(err)
}
// Fix permissions
if origMode != mode {
// Preserve SGID bit if it was set due to inheritance.
origMode = uint32(st.Mode&^0777) | origMode
err = syscall.Fchmod(fd, origMode)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchmod %#o -> %#o failed: %v", cName, mode, origMode, err)
}
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}
// Create child node & return
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ch := n.newChild(ctx, &st, out)
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return ch, 0
}
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// Readdir - FUSE call.
//
// This function is symlink-safe through use of openBackingDir() and
// ReadDirIVAt().
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func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
parentDirFd, cDirName, errno := n.prepareAtSyscallMyself()
if errno != 0 {
return nil, errno
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}
defer syscall.Close(parentDirFd)
// Read ciphertext directory
fd, err := syscallcompat.Openat(parentDirFd, cDirName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
return nil, fs.ToErrno(err)
}
defer syscall.Close(fd)
cipherEntries, specialEntries, err := syscallcompat.GetdentsSpecial(fd)
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if err != nil {
return nil, fs.ToErrno(err)
}
// Get DirIV (stays nil if PlaintextNames is used)
var cachedIV []byte
rn := n.rootNode()
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if !rn.args.PlaintextNames {
// Read the DirIV from disk
cachedIV, err = rn.nameTransform.ReadDirIVAt(fd)
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if err != nil {
tlog.Warn.Printf("OpenDir %q: could not read %s: %v", cDirName, nametransform.DirIVFilename, err)
return nil, syscall.EIO
}
}
// Decrypted directory entries
var plain []fuse.DirEntry
// Add "." and ".."
plain = append(plain, specialEntries...)
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// Filter and decrypt filenames
for i := range cipherEntries {
cName := cipherEntries[i].Name
if n.IsRoot() && cName == configfile.ConfDefaultName {
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// silently ignore "gocryptfs.conf" in the top level dir
continue
}
if rn.args.PlaintextNames {
plain = append(plain, cipherEntries[i])
continue
}
if !rn.args.DeterministicNames && cName == nametransform.DirIVFilename {
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// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
continue
}
// Handle long file name
isLong := nametransform.LongNameNone
if rn.args.LongNames {
isLong = nametransform.NameType(cName)
}
if isLong == nametransform.LongNameContent {
cNameLong, err := nametransform.ReadLongNameAt(fd, cName)
if err != nil {
tlog.Warn.Printf("OpenDir %q: invalid entry %q: Could not read .name: %v",
cDirName, cName, err)
rn.reportMitigatedCorruption(cName)
continue
}
cName = cNameLong
} else if isLong == nametransform.LongNameFilename {
// ignore "gocryptfs.longname.*.name"
continue
}
name, err := rn.nameTransform.DecryptName(cName, cachedIV)
if err != nil {
tlog.Warn.Printf("OpenDir %q: invalid entry %q: %v",
cDirName, cName, err)
rn.reportMitigatedCorruption(cName)
continue
}
// Override the ciphertext name with the plaintext name but reuse the rest
// of the structure
cipherEntries[i].Name = name
plain = append(plain, cipherEntries[i])
}
return fs.NewListDirStream(plain), 0
}
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// Rmdir - FUSE call.
//
// Symlink-safe through Unlinkat() + AT_REMOVEDIR.
func (n *Node) Rmdir(ctx context.Context, name string) (code syscall.Errno) {
rn := n.rootNode()
parentDirFd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return errno
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}
defer syscall.Close(parentDirFd)
if rn.args.PlaintextNames {
// Unlinkat with AT_REMOVEDIR is equivalent to Rmdir
err := unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
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return fs.ToErrno(err)
}
if rn.args.DeterministicNames {
if err := unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR); err != nil {
return fs.ToErrno(err)
}
if nametransform.IsLongContent(cName) {
nametransform.DeleteLongNameAt(parentDirFd, cName)
}
return 0
}
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// Unless we are running as root, we need read, write and execute permissions
// to handle gocryptfs.diriv.
permWorkaround := false
var origMode uint32
if !rn.args.PreserveOwner {
var st unix.Stat_t
err := syscallcompat.Fstatat(parentDirFd, cName, &st, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
return fs.ToErrno(err)
}
if st.Mode&0700 != 0700 {
tlog.Debug.Printf("Rmdir: permWorkaround")
permWorkaround = true
// This cast is needed on Darwin, where st.Mode is uint16.
origMode = uint32(st.Mode)
err = syscallcompat.FchmodatNofollow(parentDirFd, cName, origMode|0700)
if err != nil {
tlog.Debug.Printf("Rmdir: permWorkaround: chmod failed: %v", err)
return fs.ToErrno(err)
}
}
}
dirfd, err := syscallcompat.Openat(parentDirFd, cName,
syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
tlog.Debug.Printf("Rmdir: Open: %v", err)
return fs.ToErrno(err)
}
defer syscall.Close(dirfd)
// Undo the chmod if removing the directory failed. This must run before
// closing dirfd, so defer it after (defer is LIFO).
if permWorkaround {
defer func() {
if code != 0 {
err = unix.Fchmod(dirfd, origMode)
if err != nil {
tlog.Warn.Printf("Rmdir: permWorkaround: rollback failed: %v", err)
}
}
}()
}
retry:
// Check directory contents
children, err := syscallcompat.Getdents(dirfd)
if err == io.EOF {
// The directory is empty
tlog.Warn.Printf("Rmdir: %q: %s is missing", cName, nametransform.DirIVFilename)
err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
return fs.ToErrno(err)
}
if err != nil {
tlog.Warn.Printf("Rmdir: Getdents: %v", err)
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return fs.ToErrno(err)
}
// MacOS sprinkles .DS_Store files everywhere. This is hard to avoid for
// users, so handle it transparently here.
if runtime.GOOS == "darwin" && len(children) <= 2 && haveDsstore(children) {
err = unix.Unlinkat(dirfd, dsStoreName, 0)
if err != nil {
tlog.Warn.Printf("Rmdir: failed to delete blocking file %q: %v", dsStoreName, err)
return fs.ToErrno(err)
}
tlog.Warn.Printf("Rmdir: had to delete blocking file %q", dsStoreName)
goto retry
}
// If the directory is not empty besides gocryptfs.diriv, do not even
// attempt the dance around gocryptfs.diriv.
if len(children) > 1 {
return fs.ToErrno(syscall.ENOTEMPTY)
}
// Move "gocryptfs.diriv" to the parent dir as "gocryptfs.diriv.rmdir.XYZ"
tmpName := fmt.Sprintf("%s.rmdir.%d", nametransform.DirIVFilename, cryptocore.RandUint64())
tlog.Debug.Printf("Rmdir: Renaming %s to %s", nametransform.DirIVFilename, tmpName)
// The directory is in an inconsistent state between rename and rmdir.
// Protect against concurrent readers.
rn.dirIVLock.Lock()
defer rn.dirIVLock.Unlock()
err = syscallcompat.Renameat(dirfd, nametransform.DirIVFilename,
parentDirFd, tmpName)
if err != nil {
tlog.Warn.Printf("Rmdir: Renaming %s to %s failed: %v",
nametransform.DirIVFilename, tmpName, err)
return fs.ToErrno(err)
}
// Actual Rmdir
err = syscallcompat.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
if err != nil {
// This can happen if another file in the directory was created in the
// meantime, undo the rename
err2 := syscallcompat.Renameat(parentDirFd, tmpName,
dirfd, nametransform.DirIVFilename)
if err2 != nil {
tlog.Warn.Printf("Rmdir: Rename rollback failed: %v", err2)
}
return fs.ToErrno(err)
}
// Delete "gocryptfs.diriv.rmdir.XYZ"
err = syscallcompat.Unlinkat(parentDirFd, tmpName, 0)
if err != nil {
tlog.Warn.Printf("Rmdir: Could not clean up %s: %v", tmpName, err)
}
// Delete .name file
if nametransform.IsLongContent(cName) {
nametransform.DeleteLongNameAt(parentDirFd, cName)
}
return 0
}
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// Opendir is a FUSE call to check if the directory can be opened.
func (n *Node) Opendir(ctx context.Context) (errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscallMyself()
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if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Open backing directory
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fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
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if err != nil {
return fs.ToErrno(err)
}
syscall.Close(fd)
return 0
}