Implement -deterministic-names: extended -zerodiriv

-deterministc-names uses all-zero dirivs but does not write
them to disk anymore.

8 files changed, 95 insertions, 69 deletions

diff --git a/internal/fusefrontend/args.go b/internal/fusefrontend/args.go
index 02ffddb..e20987b 100644
--- a/internal/fusefrontend/args.go
+++ b/internal/fusefrontend/args.go
@@ -53,6 +53,6 @@ type Args struct {
 	// like rsync's `--one-file-system` does.
 	// Only applicable to reverse mode.
 	OneFileSystem bool
-	// ZeroDirIV creates diriv files as all-zero files
-	ZeroDirIV bool
+	// DeterministicNames disables gocryptfs.diriv files
+	DeterministicNames bool
 }
diff --git a/internal/fusefrontend/ctlsock_interface.go b/internal/fusefrontend/ctlsock_interface.go
index 9e8cffc..87f0dc3 100644
--- a/internal/fusefrontend/ctlsock_interface.go
+++ b/internal/fusefrontend/ctlsock_interface.go
@@ -32,7 +32,7 @@ func (rn *RootNode) EncryptPath(plainPath string) (cipherPath string, err error)
 	parts := strings.Split(plainPath, "/")
 	wd := dirfd
 	for i, part := range parts {
-		dirIV, err := nametransform.ReadDirIVAt(wd)
+		dirIV, err := rn.nameTransform.ReadDirIVAt(wd)
 		if err != nil {
 			return "", err
 		}
@@ -78,7 +78,7 @@ func (rn *RootNode) DecryptPath(cipherPath string) (plainPath string, err error)
 	parts := strings.Split(cipherPath, "/")
 	wd := dirfd
 	for i, part := range parts {
-		dirIV, err := nametransform.ReadDirIVAt(wd)
+		dirIV, err := rn.nameTransform.ReadDirIVAt(wd)
 		if err != nil {
 			return "", err
 		}
diff --git a/internal/fusefrontend/node_dir_ops.go b/internal/fusefrontend/node_dir_ops.go
index b43a4e4..c4ab861 100644
--- a/internal/fusefrontend/node_dir_ops.go
+++ b/internal/fusefrontend/node_dir_ops.go
@@ -34,9 +34,14 @@ func haveDsstore(entries []fuse.DirEntry) bool {
 // 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 {
-
 	rn := n.rootNode()
+
+	if rn.args.DeterministicNames {
+		return syscallcompat.MkdiratUser(dirfd, cName, mode, context)
+	}
+
 	// 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.
@@ -49,7 +54,7 @@ func (n *Node) mkdirWithIv(dirfd int, cName string, mode uint32, context *fuse.C
 	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, !rn.args.ZeroDirIV)
+		err = nametransform.WriteDirIVAt(dirfd2)
 		syscall.Close(dirfd2)
 	}
 	if err != nil {
@@ -90,62 +95,67 @@ func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.En
 			return nil, fs.ToErrno(err)
 		}
 		st = syscallcompat.Unix2syscall(ust)
-	} else {
-		// 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)
-			if err != nil {
-				return nil, fs.ToErrno(err)
-			}
+		// Create child node & return
+		ch := n.newChild(ctx, &st, out)
+		return ch, 0
 
-			// Create directory
-			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)
-			}
-		}
+	}
+
+	// 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
 
-		fd, err := syscallcompat.Openat(dirfd, cName,
-			syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
+	// Handle long file name
+	if nametransform.IsLongContent(cName) {
+		// Create ".name"
+		err := rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
 		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)
+		// 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 {
-			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)
-			}
+	// 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)
 		}
+
 	}
 
-	// Create child node
+	// Create child node & return
 	ch := n.newChild(ctx, &st, out)
-
 	return ch, 0
 }
 
@@ -175,7 +185,7 @@ func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
 	rn := n.rootNode()
 	if !rn.args.PlaintextNames {
 		// Read the DirIV from disk
-		cachedIV, err = nametransform.ReadDirIVAt(fd)
+		cachedIV, err = rn.nameTransform.ReadDirIVAt(fd)
 		if err != nil {
 			tlog.Warn.Printf("OpenDir %q: could not read %s: %v", cDirName, nametransform.DirIVFilename, err)
 			return nil, syscall.EIO
@@ -196,7 +206,7 @@ func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
 			plain = append(plain, cipherEntries[i])
 			continue
 		}
-		if cName == nametransform.DirIVFilename {
+		if !rn.args.DeterministicNames && cName == nametransform.DirIVFilename {
 			// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
 			continue
 		}
@@ -249,6 +259,15 @@ func (n *Node) Rmdir(ctx context.Context, name string) (code syscall.Errno) {
 		err := unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
 		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
+	}
 	// Unless we are running as root, we need read, write and execute permissions
 	// to handle gocryptfs.diriv.
 	permWorkaround := false
diff --git a/internal/fusefrontend/node_prepare_syscall.go b/internal/fusefrontend/node_prepare_syscall.go
index 0894379..8a0e75c 100644
--- a/internal/fusefrontend/node_prepare_syscall.go
+++ b/internal/fusefrontend/node_prepare_syscall.go
@@ -8,7 +8,6 @@ import (
 
 	"github.com/hanwen/go-fuse/v2/fs"
 
-	"github.com/rfjakob/gocryptfs/internal/nametransform"
 	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 )
 
@@ -73,7 +72,7 @@ func (n *Node) prepareAtSyscall(child string) (dirfd int, cName string, errno sy
 	// Cache store
 	if !rn.args.PlaintextNames {
 		var err error
-		iv, err = nametransform.ReadDirIVAt(dirfd)
+		iv, err = rn.nameTransform.ReadDirIVAt(dirfd)
 		if err != nil {
 			syscall.Close(dirfd)
 			return -1, "", fs.ToErrno(err)
diff --git a/internal/fusefrontend/xattr_unit_test.go b/internal/fusefrontend/xattr_unit_test.go
index c48781c..397e3ef 100644
--- a/internal/fusefrontend/xattr_unit_test.go
+++ b/internal/fusefrontend/xattr_unit_test.go
@@ -19,7 +19,7 @@ func newTestFS(args Args) *RootNode {
 	key := make([]byte, cryptocore.KeyLen)
 	cCore := cryptocore.New(key, cryptocore.BackendGoGCM, contentenc.DefaultIVBits, true, false)
 	cEnc := contentenc.New(cCore, contentenc.DefaultBS, false)
-	n := nametransform.New(cCore.EMECipher, true, true, nil)
+	n := nametransform.New(cCore.EMECipher, true, true, nil, false)
 	rn := NewRootNode(args, cEnc, n)
 	oneSec := time.Second
 	options := &fs.Options{
diff --git a/internal/nametransform/diriv.go b/internal/nametransform/diriv.go
index a288aa5..3a80baa 100644
--- a/internal/nametransform/diriv.go
+++ b/internal/nametransform/diriv.go
@@ -1,6 +1,7 @@
 package nametransform
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -22,7 +23,11 @@ const (
 // ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
 // Using the dirfd makes it immune to concurrent renames of the directory.
 // Retries on EINTR.
-func ReadDirIVAt(dirfd int) (iv []byte, err error) {
+// If deterministicNames is set it returns an all-zero slice.
+func (n *NameTransform) ReadDirIVAt(dirfd int) (iv []byte, err error) {
+	if n.deterministicNames {
+		return make([]byte, DirIVLen), nil
+	}
 	fdRaw, err := syscallcompat.Openat(dirfd, DirIVFilename,
 		syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
 	if err != nil {
@@ -33,6 +38,9 @@ func ReadDirIVAt(dirfd int) (iv []byte, err error) {
 	return fdReadDirIV(fd)
 }
 
+// allZeroDirIV is preallocated to quickly check if the data read from disk is all zero
+var allZeroDirIV = make([]byte, DirIVLen)
+
 // fdReadDirIV reads and verifies the DirIV from an opened gocryptfs.diriv file.
 func fdReadDirIV(fd *os.File) (iv []byte, err error) {
 	// We want to detect if the file is bigger than DirIVLen, so
@@ -46,6 +54,9 @@ func fdReadDirIV(fd *os.File) (iv []byte, err error) {
 	if len(iv) != DirIVLen {
 		return nil, fmt.Errorf("wanted %d bytes, got %d", DirIVLen, len(iv))
 	}
+	if bytes.Equal(iv, allZeroDirIV) {
+		return nil, fmt.Errorf("diriv is all-zero")
+	}
 	return iv, nil
 }
 
@@ -53,13 +64,8 @@ func fdReadDirIV(fd *os.File) (iv []byte, err error) {
 // "dirfd". On error we try to delete the incomplete file.
 // This function is exported because it is used from fusefrontend, main,
 // and also the automated tests.
-func WriteDirIVAt(dirfd int, randomInitialization bool) error {
-	var iv []byte
-	if randomInitialization {
-		iv = cryptocore.RandBytes(DirIVLen)
-	} else {
-		iv = make([]byte, DirIVLen)
-	}
+func WriteDirIVAt(dirfd int) error {
+	iv := cryptocore.RandBytes(DirIVLen)
 	// 0400 permissions: gocryptfs.diriv should never be modified after creation.
 	// Don't use "ioutil.WriteFile", it causes trouble on NFS:
 	// https://github.com/rfjakob/gocryptfs/commit/7d38f80a78644c8ec4900cc990bfb894387112ed
diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
index 74ddb07..bf8060b 100644
--- a/internal/nametransform/longnames.go
+++ b/internal/nametransform/longnames.go
@@ -114,7 +114,7 @@ func ReadLongNameAt(dirfd int, cName string) (string, error) {
 func DeleteLongNameAt(dirfd int, hashName string) error {
 	err := syscallcompat.Unlinkat(dirfd, hashName+LongNameSuffix, 0)
 	if err != nil {
-		tlog.Warn.Printf("DeleteLongName: %v", err)
+		tlog.Warn.Printf("DeleteLongNameAt: %v", err)
 	}
 	return err
 }
@@ -128,7 +128,7 @@ func (n *NameTransform) WriteLongNameAt(dirfd int, hashName string, plainName st
 	plainName = filepath.Base(plainName)
 
 	// Encrypt the basename
-	dirIV, err := ReadDirIVAt(dirfd)
+	dirIV, err := n.ReadDirIVAt(dirfd)
 	if err != nil {
 		return err
 	}
diff --git a/internal/nametransform/names.go b/internal/nametransform/names.go
index 566f0c7..412ccc0 100644
--- a/internal/nametransform/names.go
+++ b/internal/nametransform/names.go
@@ -25,11 +25,12 @@ type NameTransform struct {
 	// on the Raw64 feature flag
 	B64 *base64.Encoding
 	// Patterns to bypass decryption
-	badnamePatterns []string
+	badnamePatterns    []string
+	deterministicNames bool
 }
 
 // New returns a new NameTransform instance.
-func New(e *eme.EMECipher, longNames bool, raw64 bool, badname []string) *NameTransform {
+func New(e *eme.EMECipher, longNames bool, raw64 bool, badname []string, deterministicNames bool) *NameTransform {
 	tlog.Debug.Printf("nametransform.New: longNames=%v, raw64=%v, badname=%q",
 		longNames, raw64, badname)
 
@@ -38,10 +39,11 @@ func New(e *eme.EMECipher, longNames bool, raw64 bool, badname []string) *NameTr
 		b64 = base64.RawURLEncoding
 	}
 	return &NameTransform{
-		emeCipher:       e,
-		longNames:       longNames,
-		B64:             b64,
-		badnamePatterns: badname,
+		emeCipher:          e,
+		longNames:          longNames,
+		B64:                b64,
+		badnamePatterns:    badname,
+		deterministicNames: deterministicNames,
 	}
 }