libgocryptfs/internal/fusefrontend/fs.go
Jakob Unterwurzacher 5da292828c fusefrontend: fix chown on dangling symlinks
We (actually, go-fuse) used to call Chown() instead of Lchown()
which meant that the operation would fail on dangling symlinks.

Fix this by calling os.Lchown() ourself. Also add a test case
for this.
2016-06-08 00:32:44 +02:00

501 lines
13 KiB
Go

package fusefrontend
// FUSE operations on paths
import (
"encoding/base64"
"os"
"path/filepath"
"sync"
"syscall"
"time"
"github.com/hanwen/go-fuse/fuse"
"github.com/hanwen/go-fuse/fuse/nodefs"
"github.com/hanwen/go-fuse/fuse/pathfs"
"github.com/rfjakob/gocryptfs/internal/contentenc"
"github.com/rfjakob/gocryptfs/internal/cryptocore"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/toggledlog"
)
type FS struct {
pathfs.FileSystem // loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
args Args // Stores configuration arguments
// dirIVLock: Lock()ed if any "gocryptfs.diriv" file is modified
// Readers must RLock() it to prevent them from seeing intermediate
// states
dirIVLock sync.RWMutex
// Filename encryption helper
nameTransform *nametransform.NameTransform
// Content encryption helper
contentEnc *contentenc.ContentEnc
}
// Encrypted FUSE overlay filesystem
func NewFS(args Args) *FS {
cryptoCore := cryptocore.New(args.Masterkey, args.OpenSSL, args.GCMIV128)
contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS)
nameTransform := nametransform.New(cryptoCore, args.EMENames, args.LongNames)
return &FS{
FileSystem: pathfs.NewLoopbackFileSystem(args.Cipherdir),
args: args,
nameTransform: nameTransform,
contentEnc: contentEnc,
}
}
func (fs *FS) GetAttr(name string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
toggledlog.Debug.Printf("FS.GetAttr('%s')", name)
if fs.isFiltered(name) {
return nil, fuse.EPERM
}
cName, err := fs.encryptPath(name)
if err != nil {
return nil, fuse.ToStatus(err)
}
a, status := fs.FileSystem.GetAttr(cName, context)
if a == nil {
toggledlog.Debug.Printf("FS.GetAttr failed: %s", status.String())
return a, status
}
if a.IsRegular() {
a.Size = fs.contentEnc.CipherSizeToPlainSize(a.Size)
} else if a.IsSymlink() {
target, _ := fs.Readlink(name, context)
a.Size = uint64(len(target))
}
return a, status
}
// We always need read access to do read-modify-write cycles
func (fs *FS) mangleOpenFlags(flags uint32) (newFlags int, writeOnly bool) {
newFlags = int(flags)
if newFlags&os.O_WRONLY > 0 {
writeOnly = true
newFlags = newFlags ^ os.O_WRONLY | os.O_RDWR
}
// We also cannot open the file in append mode, we need to seek back for RMW
newFlags = newFlags &^ os.O_APPEND
return newFlags, writeOnly
}
func (fs *FS) Open(path string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
if fs.isFiltered(path) {
return nil, fuse.EPERM
}
iflags, writeOnly := fs.mangleOpenFlags(flags)
cPath, err := fs.getBackingPath(path)
if err != nil {
toggledlog.Debug.Printf("Open: getBackingPath: %v", err)
return nil, fuse.ToStatus(err)
}
toggledlog.Debug.Printf("Open: %s", cPath)
f, err := os.OpenFile(cPath, iflags, 0666)
if err != nil {
return nil, fuse.ToStatus(err)
}
return NewFile(f, writeOnly, fs.contentEnc)
}
func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Context) (fuseFile nodefs.File, code fuse.Status) {
if fs.isFiltered(path) {
return nil, fuse.EPERM
}
iflags, writeOnly := fs.mangleOpenFlags(flags)
cPath, err := fs.getBackingPath(path)
if err != nil {
return nil, fuse.ToStatus(err)
}
var fd *os.File
cName := filepath.Base(cPath)
// Handle long file name
if nametransform.IsLongContent(cName) {
var dirfd *os.File
dirfd, err = os.Open(filepath.Dir(cPath))
if err != nil {
return nil, fuse.ToStatus(err)
}
defer dirfd.Close()
// Create ".name"
err = fs.nameTransform.WriteLongName(dirfd, cName, path)
if err != nil {
return nil, fuse.ToStatus(err)
}
// Create content
var fdRaw int
fdRaw, err = syscall.Openat(int(dirfd.Fd()), cName, iflags|os.O_CREATE, mode)
if err != nil {
nametransform.DeleteLongName(dirfd, cName)
return nil, fuse.ToStatus(err)
}
fd = os.NewFile(uintptr(fdRaw), cName)
} else {
// Normal (short) file name
fd, err = os.OpenFile(cPath, iflags|os.O_CREATE, os.FileMode(mode))
if err != nil {
return nil, fuse.ToStatus(err)
}
}
return NewFile(fd, writeOnly, fs.contentEnc)
}
func (fs *FS) Chmod(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.encryptPath(path)
if err != nil {
return fuse.ToStatus(err)
}
return fs.FileSystem.Chmod(cPath, mode, context)
}
func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.getBackingPath(path)
if err != nil {
return fuse.ToStatus(err)
}
return fuse.ToStatus(os.Lchown(cPath, int(uid), int(gid)))
}
func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.encryptPath(path)
if err != nil {
return fuse.ToStatus(err)
}
// Handle long file name
cName := filepath.Base(cPath)
if nametransform.IsLongContent(cName) {
dirfd, err := os.Open(filepath.Dir(cPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
// Create ".name"
err = fs.nameTransform.WriteLongName(dirfd, cName, path)
if err != nil {
return fuse.ToStatus(err)
}
// Create device node
err = syscall.Mknodat(int(dirfd.Fd()), cName, uint32(mode), int(dev))
if err != nil {
nametransform.DeleteLongName(dirfd, cName)
}
return fuse.ToStatus(err)
}
return fs.FileSystem.Mknod(cPath, mode, dev, context)
}
// Only warn once
var truncateWarnOnce sync.Once
func (fs *FS) Truncate(path string, offset uint64, context *fuse.Context) (code fuse.Status) {
truncateWarnOnce.Do(func() {
toggledlog.Warn.Printf("truncate(2) is not supported, returning ENOSYS - use ftruncate(2)")
})
return fuse.ENOSYS
}
func (fs *FS) Utimens(path string, Atime *time.Time, Mtime *time.Time, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.encryptPath(path)
if err != nil {
return fuse.ToStatus(err)
}
return fs.FileSystem.Utimens(cPath, Atime, Mtime, context)
}
func (fs *FS) StatFs(path string) *fuse.StatfsOut {
if fs.isFiltered(path) {
return nil
}
cPath, err := fs.encryptPath(path)
if err != nil {
return nil
}
return fs.FileSystem.StatFs(cPath)
}
func (fs *FS) Readlink(path string, context *fuse.Context) (out string, status fuse.Status) {
cPath, err := fs.encryptPath(path)
if err != nil {
return "", fuse.ToStatus(err)
}
cTarget, status := fs.FileSystem.Readlink(cPath, context)
if status != fuse.OK {
return "", status
}
// Old filesystem: symlinks are encrypted like paths (CBC)
if !fs.args.DirIV {
var target string
target, err = fs.decryptPath(cTarget)
if err != nil {
toggledlog.Warn.Printf("Readlink: CBC decryption failed: %v", err)
return "", fuse.EIO
}
return target, fuse.OK
}
// Since gocryptfs v0.5 symlinks are encrypted like file contents (GCM)
cBinTarget, err := base64.URLEncoding.DecodeString(cTarget)
if err != nil {
toggledlog.Warn.Printf("Readlink: %v", err)
return "", fuse.EIO
}
target, err := fs.contentEnc.DecryptBlock([]byte(cBinTarget), 0, nil)
if err != nil {
toggledlog.Warn.Printf("Readlink: %v", err)
return "", fuse.EIO
}
return string(target), fuse.OK
}
func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.getBackingPath(path)
if err != nil {
return fuse.ToStatus(err)
}
cName := filepath.Base(cPath)
if nametransform.IsLongContent(cName) {
var dirfd *os.File
dirfd, err = os.Open(filepath.Dir(cPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
// Delete content
err = syscall.Unlinkat(int(dirfd.Fd()), cName)
if err != nil {
return fuse.ToStatus(err)
}
// Delete ".name"
err = nametransform.DeleteLongName(dirfd, cName)
if err != nil {
toggledlog.Warn.Printf("Unlink: could not delete .name file: %v", err)
}
return fuse.ToStatus(err)
}
err = syscall.Unlink(cPath)
return fuse.ToStatus(err)
}
func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (code fuse.Status) {
toggledlog.Debug.Printf("Symlink(\"%s\", \"%s\")", target, linkName)
if fs.isFiltered(linkName) {
return fuse.EPERM
}
cPath, err := fs.getBackingPath(linkName)
if err != nil {
return fuse.ToStatus(err)
}
// Before v0.5, symlinks were encrypted like paths (CBC)
// TODO drop compatibility and simplify code?
if !fs.args.DirIV {
var cTarget string
cTarget, err = fs.encryptPath(target)
if err != nil {
toggledlog.Warn.Printf("Symlink: BUG: we should not get an error here: %v", err)
return fuse.ToStatus(err)
}
err = os.Symlink(cTarget, cPath)
return fuse.ToStatus(err)
}
cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil)
cTarget := base64.URLEncoding.EncodeToString(cBinTarget)
// Handle long file name
cName := filepath.Base(cPath)
if nametransform.IsLongContent(cName) {
var dirfd *os.File
dirfd, err = os.Open(filepath.Dir(cPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
// Create ".name"
err = fs.nameTransform.WriteLongName(dirfd, cName, linkName)
if err != nil {
return fuse.ToStatus(err)
}
// Create symlink
// TODO use syscall.Symlinkat once it is available in Go
err = syscall.Symlink(cTarget, cPath)
if err != nil {
nametransform.DeleteLongName(dirfd, cName)
}
return fuse.ToStatus(err)
}
err = os.Symlink(cTarget, cPath)
return fuse.ToStatus(err)
}
func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(newPath) {
return fuse.EPERM
}
cOldPath, err := fs.getBackingPath(oldPath)
if err != nil {
return fuse.ToStatus(err)
}
cNewPath, err := fs.getBackingPath(newPath)
if err != nil {
return fuse.ToStatus(err)
}
// The Rename may cause a directory to take the place of another directory.
// That directory may still be in the DirIV cache, clear it.
fs.nameTransform.DirIVCache.Clear()
// Handle long source file name
var oldDirFd *os.File
var finalOldDirFd int
var finalOldPath = cOldPath
cOldName := filepath.Base(cOldPath)
if nametransform.IsLongContent(cOldName) {
oldDirFd, err = os.Open(filepath.Dir(cOldPath))
if err != nil {
return fuse.ToStatus(err)
}
defer oldDirFd.Close()
finalOldDirFd = int(oldDirFd.Fd())
finalOldPath = cOldName
}
// Handle long destination file name
var newDirFd *os.File
var finalNewDirFd int
var finalNewPath = cNewPath
cNewName := filepath.Base(cNewPath)
if nametransform.IsLongContent(cNewName) {
newDirFd, err = os.Open(filepath.Dir(cNewPath))
if err != nil {
return fuse.ToStatus(err)
}
defer newDirFd.Close()
finalNewDirFd = int(newDirFd.Fd())
finalNewPath = cNewName
// Create destination .name file
err = fs.nameTransform.WriteLongName(newDirFd, cNewName, newPath)
if err != nil {
return fuse.ToStatus(err)
}
}
// Actual rename
err = syscall.Renameat(finalOldDirFd, finalOldPath, finalNewDirFd, finalNewPath)
if err == syscall.ENOTEMPTY {
// If an empty directory is overwritten we will always get ENOTEMPTY as
// the "empty" directory will still contain gocryptfs.diriv.
// Handle that case by removing the target directory and trying again.
toggledlog.Debug.Printf("Rename: Handling ENOTEMPTY")
if fs.Rmdir(newPath, context) == fuse.OK {
err = syscall.Renameat(finalOldDirFd, finalOldPath, finalNewDirFd, finalNewPath)
}
}
if err != nil {
if newDirFd != nil {
// Roll back .name creation
nametransform.DeleteLongName(newDirFd, cNewName)
}
return fuse.ToStatus(err)
}
if oldDirFd != nil {
nametransform.DeleteLongName(oldDirFd, cOldName)
}
return fuse.OK
}
func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(newPath) {
return fuse.EPERM
}
cOldPath, err := fs.getBackingPath(oldPath)
if err != nil {
return fuse.ToStatus(err)
}
cNewPath, err := fs.getBackingPath(newPath)
if err != nil {
return fuse.ToStatus(err)
}
// Handle long file name
cNewName := filepath.Base(cNewPath)
if nametransform.IsLongContent(cNewName) {
dirfd, err := os.Open(filepath.Dir(cNewPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
err = fs.nameTransform.WriteLongName(dirfd, cNewName, newPath)
if err != nil {
return fuse.ToStatus(err)
}
// TODO Use syscall.Linkat once it is available in Go (it is not in Go
// 1.6).
err = syscall.Link(cOldPath, cNewPath)
if err != nil {
nametransform.DeleteLongName(dirfd, cNewName)
return fuse.ToStatus(err)
}
}
return fuse.ToStatus(os.Link(cOldPath, cNewPath))
}
func (fs *FS) Access(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
return fuse.EPERM
}
cPath, err := fs.getBackingPath(path)
if err != nil {
return fuse.ToStatus(err)
}
return fuse.ToStatus(syscall.Access(cPath, mode))
}
func (fs *FS) GetXAttr(name string, attr string, context *fuse.Context) ([]byte, fuse.Status) {
return nil, fuse.ENOSYS
}
func (fs *FS) SetXAttr(name string, attr string, data []byte, flags int, context *fuse.Context) fuse.Status {
return fuse.ENOSYS
}
func (fs *FS) ListXAttr(name string, context *fuse.Context) ([]string, fuse.Status) {
return nil, fuse.ENOSYS
}
func (fs *FS) RemoveXAttr(name string, attr string, context *fuse.Context) fuse.Status {
return fuse.ENOSYS
}