4 files changed, 35 insertions, 16 deletions

diff --git a/cryptfs/config_file.go b/cryptfs/config_file.go
index f258a5e..1e7e3b3 100644
--- a/cryptfs/config_file.go
+++ b/cryptfs/config_file.go
@@ -4,14 +4,18 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
+	"log"
 )
 import "os"
 
 const (
 	// The dot "." is not used in base64url (RFC4648), hence
 	// we can never clash with an encrypted file.
-	ConfDefaultName    = "gocryptfs.conf"
+	ConfDefaultName = "gocryptfs.conf"
+	// Understood Feature Flags
+	// Also teach isFeatureFlagKnown() about any additions
 	FlagPlaintextNames = "PlaintextNames"
+	FlagDirIV          = "DirIV"
 )
 
 type ConfFile struct {
@@ -78,12 +82,8 @@ func LoadConfFile(filename string, password string) ([]byte, *ConfFile, error) {
 		return nil, nil, fmt.Errorf("Unsupported on-disk format %d\n", cf.Version)
 	}
 
-	// Verify that we know all feature flags
 	for _, flag := range cf.FeatureFlags {
-		switch flag {
-		case FlagPlaintextNames:
-			continue
-		default:
+		if cf.isFeatureFlagKnown(flag) == false {
 			return nil, nil, fmt.Errorf("Unsupported feature flag %s\n", flag)
 		}
 	}
@@ -151,8 +151,21 @@ func (cf *ConfFile) WriteFile() error {
 	return nil
 }
 
+// Verify that we understand a feature flag
+func (cf *ConfFile) isFeatureFlagKnown(flag string) bool {
+	switch flag {
+	case FlagPlaintextNames, FlagDirIV:
+		return true
+	default:
+		return false
+	}
+}
+
 // isFeatureFlagSet - is the feature flag "flagWant" enabled?
-func (cf *ConfFile) isFeatureFlagSet(flagWant string) bool {
+func (cf *ConfFile) IsFeatureFlagSet(flagWant string) bool {
+	if !cf.isFeatureFlagKnown(flagWant) {
+		log.Panicf("BUG: Tried to use unsupported feature flag %s", flagWant)
+	}
 	for _, flag := range cf.FeatureFlags {
 		if flag == flagWant {
 			return true
@@ -160,7 +173,3 @@ func (cf *ConfFile) isFeatureFlagSet(flagWant string) bool {
 	}
 	return false
 }
-
-func (cf *ConfFile) PlaintextNames() bool {
-	return cf.isFeatureFlagSet(FlagPlaintextNames)
-}
diff --git a/cryptfs/config_test.go b/cryptfs/config_test.go
index cd8ed2f..e052428 100644
--- a/cryptfs/config_test.go
+++ b/cryptfs/config_test.go
@@ -69,3 +69,16 @@ func TestCreateConfFile(t *testing.T) {
 	}
 
 }
+
+func TestIsFeatureFlagKnown(t *testing.T) {
+	var cf ConfFile
+	if !cf.isFeatureFlagKnown(FlagDirIV) {
+		t.Errorf("This flag should be known")
+	}
+	if !cf.isFeatureFlagKnown(FlagPlaintextNames) {
+		t.Errorf("This flag should be known")
+	}
+	if cf.isFeatureFlagKnown("StrangeFeatureFlag") {
+		t.Errorf("This flag should be NOT known")
+	}
+}
diff --git a/cryptfs/cryptfs_names.go b/cryptfs/cryptfs_names.go
index 37a769f..2a5f158 100644
--- a/cryptfs/cryptfs_names.go
+++ b/cryptfs/cryptfs_names.go
@@ -65,7 +65,6 @@ func (be *CryptFS) encryptName(plainName string, iv []byte) string {
 	return cipherName64
 }
 
-
 // TranslatePathZeroIV - encrypt or decrypt path using CBC with a constant all-zero IV.
 // Just splits the string on "/" and hands the parts to encryptName() / decryptName()
 func (be *CryptFS) TranslatePathZeroIV(path string, op int) (string, error) {
@@ -155,5 +154,3 @@ func (be *CryptFS) unPad16(orig []byte) ([]byte, error) {
 	}
 	return orig[0:newLen], nil
 }
-
-
diff --git a/cryptfs/names_diriv.go b/cryptfs/names_diriv.go
index 1415bcb..46e2bfd 100644
--- a/cryptfs/names_diriv.go
+++ b/cryptfs/names_diriv.go
@@ -1,9 +1,9 @@
 package cryptfs
 
 import (
-	"path/filepath"
-	"io/ioutil"
 	"fmt"
+	"io/ioutil"
+	"path/filepath"
 	"strings"
 )