libgocryptfs/internal/fusefrontend/fs.go

368 lines
10 KiB
Go

package fusefrontend
// FUSE operations on paths
import (
"encoding/base64"
"os"
"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), fuse.OK
}
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)
}
// Create .name file to store the long file name if needed
if !fs.args.PlaintextNames {
err = fs.nameTransform.WriteLongName(cPath, path)
if err != nil {
return nil, fuse.ToStatus(err)
}
}
f, err := os.OpenFile(cPath, iflags|os.O_CREATE, os.FileMode(mode))
if err != nil {
return nil, fuse.ToStatus(err)
}
return NewFile(f, writeOnly, fs.contentEnc), fuse.OK
}
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.encryptPath(path)
if err != nil {
return fuse.ToStatus(err)
}
return fs.FileSystem.Chown(cPath, uid, gid, context)
}
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)
}
if !fs.args.PlaintextNames {
// Create .name file to store the long file name if needed
err = fs.nameTransform.WriteLongName(cPath, path)
if err != nil {
return fuse.ToStatus(err)
}
}
return fs.FileSystem.Mknod(cPath, mode, dev, context)
}
var truncateWarned bool
func (fs *FS) Truncate(path string, offset uint64, context *fuse.Context) (code fuse.Status) {
// Only warn once
if !truncateWarned {
toggledlog.Warn.Printf("truncate(2) is not supported, returning ENOSYS - use ftruncate(2)")
truncateWarned = true
}
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) 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 {
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)
}
err = syscall.Unlink(cPath)
// Delete .name file
if err == nil && !fs.args.PlaintextNames {
nametransform.DeleteLongName(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)
}
// Old filesystem: symlinks are encrypted like paths (CBC)
// TODO drop compatibility and simplify code
if !fs.args.DirIV {
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)
}
// Since gocryptfs v0.5 symlinks are encrypted like file contents (GCM)
cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil)
cTarget := base64.URLEncoding.EncodeToString(cBinTarget)
if !fs.args.PlaintextNames {
// Create .name file to store the long file name if needed
err = fs.nameTransform.WriteLongName(cPath, linkName)
if err != nil {
return fuse.ToStatus(err)
}
}
err = os.Symlink(cTarget, cPath)
toggledlog.Debug.Printf("Symlink: os.Symlink(%s, %s) = %v", cTarget, cPath, err)
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()
if !fs.args.PlaintextNames {
// Create .name file to store the new long file name if needed
err = fs.nameTransform.WriteLongName(cNewPath, newPath)
if err != nil {
return fuse.ToStatus(err)
}
}
// Actual rename
err = os.Rename(cOldPath, cNewPath)
if lerr, ok := err.(*os.LinkError); ok && lerr.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 = os.Rename(cOldPath, cNewPath)
}
}
if err == nil {
// Rename succeeded - delete old long name file
nametransform.DeleteLongName(cOldPath)
} else {
// Rename has failed - undo long name file creation
nametransform.DeleteLongName(cNewPath)
}
return fuse.ToStatus(err)
}
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)
}
if !fs.args.PlaintextNames {
// Create .name file to store the long file name if needed
err = fs.nameTransform.WriteLongName(cNewPath, newPath)
if err != nil {
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
}