libgocryptfs/internal/fusefrontend/node.go
2020-09-09 11:17:19 +02:00

525 lines
14 KiB
Go

package fusefrontend
import (
"context"
"os"
"syscall"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// Node is a file or directory in the filesystem tree
// in a gocryptfs mount.
type Node struct {
fs.Inode
}
// Lookup - FUSE call for discovering a file.
func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Get device number and inode number into `st`
st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
return nil, fs.ToErrno(err)
}
// Create new inode and fill `out`
ch = n.newChild(ctx, st, out)
// Translate ciphertext size in `out.Attr.Size` to plaintext size
n.translateSize(dirfd, cName, &out.Attr)
return ch, 0
}
// GetAttr - FUSE call for stat()ing a file.
//
// GetAttr is symlink-safe through use of openBackingDir() and Fstatat().
func (n *Node) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) (errno syscall.Errno) {
// If the kernel gives us a file handle, use it.
if f != nil {
return f.(fs.FileGetattrer).Getattr(ctx, out)
}
dirfd, cName, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
return fs.ToErrno(err)
}
// Fix inode number
rn := n.rootNode()
rn.inoMap.TranslateStat(st)
out.Attr.FromStat(st)
// Translate ciphertext size in `out.Attr.Size` to plaintext size
n.translateSize(dirfd, cName, &out.Attr)
if rn.args.ForceOwner != nil {
out.Owner = *rn.args.ForceOwner
}
return 0
}
// Create - FUSE call. Creates a new file.
//
// Symlink-safe through the use of Openat().
func (n *Node) Create(ctx context.Context, name string, flags uint32, mode uint32, out *fuse.EntryOut) (inode *fs.Inode, fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
var err error
fd := -1
// Make sure context is nil if we don't want to preserve the owner
rn := n.rootNode()
if !rn.args.PreserveOwner {
ctx = nil
}
newFlags := rn.mangleOpenFlags(flags)
// Handle long file name
ctx2 := toFuseCtx(ctx)
if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
// Create ".name"
err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
if err != nil {
return nil, nil, 0, fs.ToErrno(err)
}
// Create content
fd, err = syscallcompat.OpenatUser(dirfd, cName, newFlags|syscall.O_CREAT|syscall.O_EXCL, mode, ctx2)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create content, normal (short) file name
fd, err = syscallcompat.OpenatUser(dirfd, cName, newFlags|syscall.O_CREAT|syscall.O_EXCL, mode, ctx2)
}
if err != nil {
// xfstests generic/488 triggers this
if err == syscall.EMFILE {
var lim syscall.Rlimit
syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
tlog.Warn.Printf("Create %q: too many open files. Current \"ulimit -n\": %d", cName, lim.Cur)
}
return nil, nil, 0, fs.ToErrno(err)
}
// Get device number and inode number into `st`
var st syscall.Stat_t
err = syscall.Fstat(fd, &st)
if err != nil {
errno = fs.ToErrno(err)
return
}
ch := n.newChild(ctx, &st, out)
f := os.NewFile(uintptr(fd), cName)
return ch, NewFile(f, rn, &st), 0, 0
}
// Unlink - FUSE call. Delete a file.
//
// Symlink-safe through use of Unlinkat().
func (n *Node) Unlink(ctx context.Context, name string) (errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Delete content
err := syscallcompat.Unlinkat(dirfd, cName, 0)
if err != nil {
return fs.ToErrno(err)
}
// Delete ".name" file
if !n.rootNode().args.PlaintextNames && nametransform.IsLongContent(cName) {
err = nametransform.DeleteLongNameAt(dirfd, cName)
if err != nil {
tlog.Warn.Printf("Unlink: could not delete .name file: %v", err)
}
}
return fs.ToErrno(err)
}
// Readlink - FUSE call.
//
// Symlink-safe through openBackingDir() + Readlinkat().
func (n *Node) Readlink(ctx context.Context) (out []byte, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
return n.readlink(dirfd, cName)
}
// Open - FUSE call. Open already-existing file.
//
// Symlink-safe through Openat().
func (n *Node) Open(ctx context.Context, flags uint32) (fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
rn := n.rootNode()
newFlags := rn.mangleOpenFlags(flags)
// Taking this lock makes sure we don't race openWriteOnlyFile()
rn.openWriteOnlyLock.RLock()
defer rn.openWriteOnlyLock.RUnlock()
// Open backing file
fd, err := syscallcompat.Openat(dirfd, cName, newFlags, 0)
// Handle a few specific errors
if err != nil {
if err == syscall.EMFILE {
var lim syscall.Rlimit
syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
tlog.Warn.Printf("Open %q: too many open files. Current \"ulimit -n\": %d", cName, lim.Cur)
}
if err == syscall.EACCES && (int(flags)&syscall.O_ACCMODE) == syscall.O_WRONLY {
fd, err = rn.openWriteOnlyFile(dirfd, cName, newFlags)
}
}
// Could not handle the error? Bail out
if err != nil {
errno = fs.ToErrno(err)
return
}
var st syscall.Stat_t
err = syscall.Fstat(fd, &st)
if err != nil {
errno = fs.ToErrno(err)
return
}
f := os.NewFile(uintptr(fd), cName)
fh = NewFile(f, rn, &st)
return
}
// Setattr - FUSE call. Called for chmod, truncate, utimens, ...
func (n *Node) Setattr(ctx context.Context, f fs.FileHandle, in *fuse.SetAttrIn, out *fuse.AttrOut) (errno syscall.Errno) {
// Use the fd if the kernel gave us one
if f != nil {
f2 := f.(*File)
return f2.Setattr(ctx, in, out)
}
dirfd, cName, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// chmod(2)
if mode, ok := in.GetMode(); ok {
errno = fs.ToErrno(syscallcompat.FchmodatNofollow(dirfd, cName, mode))
if errno != 0 {
return errno
}
}
// chown(2)
uid32, uOk := in.GetUID()
gid32, gOk := in.GetGID()
if uOk || gOk {
uid := -1
gid := -1
if uOk {
uid = int(uid32)
}
if gOk {
gid = int(gid32)
}
errno = fs.ToErrno(syscallcompat.Fchownat(dirfd, cName, uid, gid, unix.AT_SYMLINK_NOFOLLOW))
if errno != 0 {
return errno
}
}
// utimens(2)
mtime, mok := in.GetMTime()
atime, aok := in.GetATime()
if mok || aok {
ap := &atime
mp := &mtime
if !aok {
ap = nil
}
if !mok {
mp = nil
}
errno = fs.ToErrno(syscallcompat.UtimesNanoAtNofollow(dirfd, cName, ap, mp))
if errno != 0 {
return errno
}
}
// For truncate, the user has to have write permissions. That means we can
// depend on opening a RDWR fd and letting the File handle truncate.
if sz, ok := in.GetSize(); ok {
f, _, errno := n.Open(ctx, syscall.O_RDWR)
if errno != 0 {
return errno
}
f2 := f.(*File)
defer f2.Release(ctx)
errno = syscall.Errno(f2.truncate(sz))
if errno != 0 {
return errno
}
return f2.Getattr(ctx, out)
}
return n.Getattr(ctx, nil, out)
}
// StatFs - FUSE call. Returns information about the filesystem.
//
// Symlink-safe because the path is ignored.
func (n *Node) Statfs(ctx context.Context, out *fuse.StatfsOut) syscall.Errno {
p := n.rootNode().args.Cipherdir
var st syscall.Statfs_t
err := syscall.Statfs(p, &st)
if err != nil {
return fs.ToErrno(err)
}
out.FromStatfsT(&st)
return 0
}
// Mknod - FUSE call. Create a device file.
//
// Symlink-safe through use of Mknodat().
func (n *Node) Mknod(ctx context.Context, name string, mode, rdev uint32, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Make sure context is nil if we don't want to preserve the owner
rn := n.rootNode()
if !rn.args.PreserveOwner {
ctx = nil
}
// Create ".name" file to store long file name (except in PlaintextNames mode)
var err error
ctx2 := toFuseCtx(ctx)
if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
err := rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
if err != nil {
errno = fs.ToErrno(err)
return
}
// Create "gocryptfs.longfile." device node
err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create regular device node
err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
}
if err != nil {
errno = fs.ToErrno(err)
return
}
st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
errno = fs.ToErrno(err)
return
}
inode = n.newChild(ctx, st, out)
return inode, 0
}
// Link - FUSE call. Creates a hard link at "newPath" pointing to file
// "oldPath".
//
// Symlink-safe through use of Linkat().
func (n *Node) Link(ctx context.Context, target fs.InodeEmbedder, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
n2 := toNode(target)
dirfd2, cName2, errno := n2.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd2)
// Handle long file name (except in PlaintextNames mode)
rn := n.rootNode()
var err error
if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
if err != nil {
errno = fs.ToErrno(err)
return
}
// Create "gocryptfs.longfile." link
err = syscallcompat.Linkat(dirfd2, cName2, dirfd, cName, 0)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create regular link
err = syscallcompat.Linkat(dirfd2, cName2, dirfd, cName, 0)
}
if err != nil {
errno = fs.ToErrno(err)
return
}
st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
errno = fs.ToErrno(err)
return
}
inode = n.newChild(ctx, st, out)
return inode, 0
}
// Symlink - FUSE call. Create a symlink.
//
// Symlink-safe through use of Symlinkat.
func (n *Node) Symlink(ctx context.Context, target, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Make sure context is nil if we don't want to preserve the owner
rn := n.rootNode()
if !rn.args.PreserveOwner {
ctx = nil
}
cTarget := target
if !rn.args.PlaintextNames {
// Symlinks are encrypted like file contents (GCM) and base64-encoded
cTarget = rn.encryptSymlinkTarget(target)
}
// Create ".name" file to store long file name (except in PlaintextNames mode)
var err error
ctx2 := toFuseCtx(ctx)
if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
if err != nil {
errno = fs.ToErrno(err)
return
}
// Create "gocryptfs.longfile." symlink
err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create symlink
err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
}
st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
errno = fs.ToErrno(err)
return
}
inode = n.newChild(ctx, st, out)
return inode, 0
}
// Rename - FUSE call.
// This function is called on the PARENT DIRECTORY of `name`.
//
// Symlink-safe through Renameat().
func (n *Node) Rename(ctx context.Context, name string, newParent fs.InodeEmbedder, newName string, flags uint32) (errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
n2 := toNode(newParent)
dirfd2, cName2, errno := n2.prepareAtSyscall(newName)
if errno != 0 {
return
}
defer syscall.Close(dirfd2)
// Easy case.
rn := n.rootNode()
if rn.args.PlaintextNames {
return fs.ToErrno(syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags)))
}
// Long destination file name: create .name file
nameFileAlreadyThere := false
var err error
if nametransform.IsLongContent(cName2) {
err = rn.nameTransform.WriteLongNameAt(dirfd2, cName2, newName)
// Failure to write the .name file is expected when the target path already
// exists. Since hashes are pretty unique, there is no need to modify the
// .name file in this case, and we ignore the error.
if err == syscall.EEXIST {
nameFileAlreadyThere = true
} else if err != nil {
return fs.ToErrno(err)
}
}
// Actual rename
tlog.Debug.Printf("Renameat %d/%s -> %d/%s\n", dirfd, cName, dirfd2, cName2)
err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
if (flags&syscallcompat.RENAME_NOREPLACE == 0) && (err == syscall.ENOTEMPTY || err == syscall.EEXIST) {
// If an empty directory is overwritten we will always get an error as
// the "empty" directory will still contain gocryptfs.diriv.
// Interestingly, ext4 returns ENOTEMPTY while xfs returns EEXIST.
// We handle that by trying to fs.Rmdir() the target directory and trying
// again.
tlog.Debug.Printf("Rename: Handling ENOTEMPTY")
if n2.Rmdir(ctx, newName) == 0 {
err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
}
}
if err != nil {
if nametransform.IsLongContent(cName2) && nameFileAlreadyThere == false {
// Roll back .name creation unless the .name file was already there
nametransform.DeleteLongNameAt(dirfd2, cName2)
}
return fs.ToErrno(err)
}
if nametransform.IsLongContent(cName) {
nametransform.DeleteLongNameAt(dirfd, cName)
}
return 0
}