fusefrontend: implement path decryption via ctlsock

Closes https://github.com/rfjakob/gocryptfs/issues/84 .

internal/fusefrontend/ctlsock_interface.go

@@ -1,9 +1,12 @@
 package fusefrontend
 
 import (
-	"errors"
+	"fmt"
+	"path"
+	"strings"
 
 	"github.com/rfjakob/gocryptfs/internal/ctlsock"
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
 )
 
 var _ ctlsock.Interface = &FS{} // Verify that interface is implemented.
@@ -15,5 +18,33 @@ func (fs *FS) EncryptPath(plainPath string) (string, error) {
 
 // DecryptPath implements ctlsock.Backend
 func (fs *FS) DecryptPath(cipherPath string) (string, error) {
-	return "", errors.New("Forward mode does not have path decryption implemented")
+	if fs.args.PlaintextNames || cipherPath == "" {
+		return cipherPath, nil
+	}
+	plainPath := ""
+	parts := strings.Split(cipherPath, "/")
+	wd := fs.args.Cipherdir
+	for _, part := range parts {
+		dirIV, err := nametransform.ReadDirIV(wd)
+		if err != nil {
+			fmt.Printf("ReadDirIV: %v\n", err)
+			return "", err
+		}
+		longPart := part
+		if nametransform.IsLongContent(part) {
+			longPart, err = nametransform.ReadLongName(wd + "/" + part)
+			if err != nil {
+				fmt.Printf("ReadLongName: %v\n", err)
+				return "", err
+			}
+		}
+		name, err := fs.nameTransform.DecryptName(longPart, dirIV)
+		if err != nil {
+			fmt.Printf("DecryptName: %v\n", err)
+			return "", err
+		}
+		plainPath = path.Join(plainPath, name)
+		wd = path.Join(wd, part)
+	}
+	return plainPath, nil
 }

tests/defaults/ctlsock_test.go

@@ -0,0 +1,98 @@
+package defaults
+
+import (
+	"os"
+	"syscall"
+	"testing"
+
+	"github.com/rfjakob/gocryptfs/internal/ctlsock"
+	"github.com/rfjakob/gocryptfs/tests/test_helpers"
+)
+
+func TestCtlSock(t *testing.T) {
+	cDir := test_helpers.InitFS(t)
+	pDir := cDir + ".mnt"
+	sock := cDir + ".sock"
+	test_helpers.MountOrFatal(t, cDir, pDir, "-ctlsock="+sock, "-extpass", "echo test")
+	defer test_helpers.UnmountPanic(pDir)
+	req := ctlsock.RequestStruct{
+		EncryptPath: "foobar",
+	}
+	response := test_helpers.QueryCtlSock(t, sock, req)
+	if response.Result == "" || response.ErrNo != 0 {
+		t.Errorf("got an error reply: %+v", response)
+	}
+	req.EncryptPath = "not-existing-dir/xyz"
+	response = test_helpers.QueryCtlSock(t, sock, req)
+	if response.ErrNo != int32(syscall.ENOENT) || response.Result != "" {
+		t.Errorf("incorrect error handling: %+v", response)
+	}
+	// Strange paths should not cause a crash
+	crashers := []string{"/foo", "foo/", "/foo/", ".", "/////", "/../../."}
+	for _, c := range crashers {
+		req.EncryptPath = c
+		// QueryCtlSock calls t.Fatal if it gets EOF when gocryptfs panics
+		response = test_helpers.QueryCtlSock(t, sock, req)
+		if response.WarnText == "" {
+			t.Errorf("We should get a warning about non-canonical paths here")
+		}
+	}
+}
+
+func TestCtlSockDecrypt(t *testing.T) {
+	cDir := test_helpers.InitFS(t)
+	pDir := cDir + ".mnt"
+	sock := cDir + ".sock"
+	test_helpers.MountOrFatal(t, cDir, pDir, "-ctlsock="+sock, "-extpass", "echo test")
+	defer test_helpers.UnmountPanic(pDir)
+
+	paths := []string{
+		"xxxxxxx123456789",
+		"foo/bar/baz",
+		test_helpers.X255,
+		"123/" + test_helpers.X255,
+		"123/" + test_helpers.X255 + "/456",
+	}
+
+	for _, p := range paths {
+		// Create path
+		err := os.MkdirAll(pDir+"/"+p, 0700)
+		if err != nil {
+			t.Fatal(err)
+		}
+		// Encrypt the path through the ctlsock
+		req := ctlsock.RequestStruct{
+			EncryptPath: p,
+		}
+		response := test_helpers.QueryCtlSock(t, sock, req)
+		if response.Result == "" || response.ErrNo != 0 {
+			t.Fatalf("got an error reply: %+v", response)
+		}
+		// Check if the encrypted path actually exists
+		cPath := response.Result
+		_, err = os.Stat(cDir + "/" + cPath)
+		if err != nil {
+			t.Fatal(err)
+		}
+		// Decrypt the path through the ctlsock and see if we get the original path
+		req = ctlsock.RequestStruct{
+			DecryptPath: cPath,
+		}
+		response = test_helpers.QueryCtlSock(t, sock, req)
+		if response.Result == "" || response.ErrNo != 0 {
+			t.Errorf("query=%+v, response=%+v", req, response)
+			continue
+		}
+		if response.Result != p {
+			t.Errorf("want=%q got=%q", p, response.Result)
+		}
+	}
+}
+
+func TestCtlSockDecryptCrash(t *testing.T) {
+	cDir := test_helpers.InitFS(t)
+	pDir := cDir + ".mnt"
+	sock := cDir + ".sock"
+	test_helpers.MountOrFatal(t, cDir, pDir, "-ctlsock="+sock, "-extpass", "echo test")
+	defer test_helpers.UnmountPanic(pDir)
+}

tests/defaults/main_test.go

@@ -8,10 +8,8 @@ import (
 	"os/exec"
 	"runtime"
 	"sync"
-	"syscall"
 	"testing"
 
-	"github.com/rfjakob/gocryptfs/internal/ctlsock"
 	"github.com/rfjakob/gocryptfs/tests/test_helpers"
 )
 
@@ -42,36 +40,6 @@ func Test1980Tar(t *testing.T) {
 	}
 }
 
-func TestCtlSock(t *testing.T) {
-	cDir := test_helpers.InitFS(t)
-	pDir := cDir + ".mnt"
-	sock := cDir + ".sock"
-	test_helpers.MountOrFatal(t, cDir, pDir, "-ctlsock="+sock, "-extpass", "echo test")
-	defer test_helpers.UnmountPanic(pDir)
-	req := ctlsock.RequestStruct{
-		EncryptPath: "foobar",
-	}
-	response := test_helpers.QueryCtlSock(t, sock, req)
-	if response.Result == "" || response.ErrNo != 0 {
-		t.Errorf("got an error reply: %+v", response)
-	}
-	req.EncryptPath = "not-existing-dir/xyz"
-	response = test_helpers.QueryCtlSock(t, sock, req)
-	if response.ErrNo != int32(syscall.ENOENT) || response.Result != "" {
-		t.Errorf("incorrect error handling: %+v", response)
-	}
-	// Strange paths should not cause a crash
-	crashers := []string{"/foo", "foo/", "/foo/", ".", "/////", "/../../."}
-	for _, c := range crashers {
-		req.EncryptPath = c
-		// QueryCtlSock calls t.Fatal if it gets EOF when gocryptfs panics
-		response = test_helpers.QueryCtlSock(t, sock, req)
-		if response.WarnText == "" {
-			t.Errorf("We should get a warning about non-canonical paths here")
-		}
-	}
-}
-
 // In gocryptfs before v1.2, the file header was only read once for each
 // open. But truncating a file to zero will generate a new random file ID.
 // The sequence below caused an I/O error to be returned.

tests/test_helpers/helpers.go

@@ -1,6 +1,7 @@
 package test_helpers
 
 import (
+	"bytes"
 	"crypto/md5"
 	"encoding/hex"
 	"encoding/json"
@@ -27,6 +28,9 @@ const GocryptfsBinary = "../../gocryptfs"
 // UnmountScript is the fusermount/umount compatibility wrapper script
 const UnmountScript = "../fuse-unmount.bash"
 
+// X255 contains 255 uppercase "X". This can be used as a maximum-length filename.
+var X255 string
+
 // TmpDir is a unique temporary directory. "go test" runs package tests in parallel. We create a
 // unique TmpDir in init() so the tests do not interfere.
 var TmpDir string
@@ -38,6 +42,8 @@ var DefaultPlainDir string
 var DefaultCipherDir string
 
 func init() {
+	X255 = string(bytes.Repeat([]byte("X"), 255))
+
 	os.MkdirAll(testParentDir, 0700)
 	var err error
 	TmpDir, err = ioutil.TempDir(testParentDir, "")