1 files changed, 381 insertions, 0 deletions
diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
new file mode 100644
index 0000000..0331215
--- /dev/null
+++ b/internal/fusefrontend/fs.go
@@ -0,0 +1,381 @@
+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/toggledlog"
+	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
+	"github.com/rfjakob/gocryptfs/internal/contentenc"
+	"github.com/rfjakob/gocryptfs/internal/configfile"
+)
+
+const plainBS = 4096
+
+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, plainBS)
+	nameTransform := nametransform.New(cryptoCore, args.EMENames)
+
+	return &FS{
+		FileSystem: pathfs.NewLoopbackFileSystem(args.Cipherdir),
+		args:       args,
+		nameTransform: nameTransform,
+		contentEnc: contentEnc,
+	}
+}
+
+// GetBackingPath - get the absolute encrypted path of the backing file
+// from the relative plaintext path "relPath"
+func (fs *FS) getBackingPath(relPath string) (string, error) {
+	cPath, err := fs.encryptPath(relPath)
+	if err != nil {
+		return "", err
+	}
+	cAbsPath := filepath.Join(fs.args.Cipherdir, cPath)
+	toggledlog.Debug.Printf("getBackingPath: %s + %s -> %s", fs.args.Cipherdir, relPath, cAbsPath)
+	return cAbsPath, nil
+}
+
+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
+}
+
+func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
+	toggledlog.Debug.Printf("OpenDir(%s)", dirName)
+	cDirName, err := fs.encryptPath(dirName)
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	// Read ciphertext directory
+	cipherEntries, status := fs.FileSystem.OpenDir(cDirName, context)
+	if cipherEntries == nil {
+		return nil, status
+	}
+	// Get DirIV (stays nil if DirIV if off)
+	var cachedIV []byte
+	if fs.args.DirIV {
+		// Read the DirIV once and use it for all later name decryptions
+		cDirAbsPath := filepath.Join(fs.args.Cipherdir, cDirName)
+		cachedIV, err = fs.nameTransform.ReadDirIV(cDirAbsPath)
+		if err != nil {
+			return nil, fuse.ToStatus(err)
+		}
+	}
+	// Filter and decrypt filenames
+	var plain []fuse.DirEntry
+	for i := range cipherEntries {
+		cName := cipherEntries[i].Name
+		if dirName == "" && cName == configfile.ConfDefaultName {
+			// silently ignore "gocryptfs.conf" in the top level dir
+			continue
+		}
+		if fs.args.DirIV && cName == nametransform.DirIVFilename {
+			// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
+			continue
+		}
+		var name string = cName
+		if !fs.args.PlaintextNames {
+			name, err = fs.nameTransform.DecryptName(cName, cachedIV)
+			if err != nil {
+				toggledlog.Warn.Printf("Invalid name \"%s\" in dir \"%s\": %s", cName, cDirName, err)
+				continue
+			}
+		}
+		cipherEntries[i].Name = name
+		plain = append(plain, cipherEntries[i])
+	}
+	return plain, 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)
+	}
+	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)
+	}
+	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)
+	}
+	return fuse.ToStatus(syscall.Unlink(cPath))
+}
+
+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)
+	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)
+
+	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()
+
+	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)
+		}
+	}
+
+	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)
+	}
+	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
+}