pkg/cryptstate: add NULL crypto mode.

pkg/cryptstate/cryptstate.go

@@ -55,6 +55,8 @@ func createMode(mode string) (CryptoMode, error) {
 		return &ocb2Mode{}, nil
 	case "XSalsa20-Poly1305":
 		return &secretBoxMode{}, nil
+	case "NULL":
+		return &nullMode{}, nil
 	}
 	return nil, errors.New("cryptstate: no such CryptoMode")
 }

pkg/cryptstate/cryptstate_test.go

@@ -68,7 +68,10 @@ func TestOCB2AES128Decrypt(t *testing.T) {
 	cs := CryptState{}
 	out := make([]byte, 15)
 	cs.SetKey("OCB2-AES128", key[:], div[:], eiv[:])
-	cs.Decrypt(out, crypted[:])
+	err := cs.Decrypt(out, crypted[:])
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
 
 	if !bytes.Equal(out, expected[:]) {
 		t.Errorf("Mismatch in output")
@@ -146,11 +149,40 @@ func TestXSalsa20Poly1305Decrypt(t *testing.T) {
 	}
 
 	message, _ := hex.DecodeString("028442bc313f4626f1359e3b50122b6ce6fe66ddfe7d39d14e637eb4fd5b45beadab55198df6ab5368439792a23c87db70acb6156dc5ef957ac04f6276cf6093b84be77ff0849cc33e34b7254d5a8f65ad")
-	cs.SetKey("XSalsa20-Poly1305", key[:], div[:], eiv[:])
+	cs.SetKey("XSalsa20-Poly1305", key[:], eiv[:], div[:])
 	dst := make([]byte, len(message)-cs.Overhead())
-	cs.Decrypt(dst, message[:])
+	err := cs.Decrypt(dst, message[:])
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
 
 	if !bytes.Equal(dst, expected[:]) {
 		t.Fatalf("mismatch! got\n%x\n, expected\n%x", dst, expected)
 	}
+}
+
+func TestNullEncrypt(t *testing.T) {
+	cs := CryptState{}
+	cs.SetKey("NULL", []byte{}, []byte{1}, []byte{1})
+	msg := []byte("HelloWorld")
+	dst := make([]byte, len(msg)+cs.Overhead())
+	cs.Encrypt(dst, msg)
+	if !bytes.Equal(dst[1:], msg) {
+		t.Fatalf("mismatch! got\n%x\n, expected\n%x", dst, msg)
+	}
+}
+
+func TestNullDecrypt(t *testing.T) {
+	cs := CryptState{}
+	cs.SetKey("NULL", []byte{}, []byte{1}, []byte{1})
+	msg := []byte{2}
+	msg = append(msg, []byte("HelloWorld")...)
+	dst := make([]byte, len(msg)-cs.Overhead())
+	err := cs.Decrypt(dst, msg)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	if !bytes.Equal(dst, msg[1:]) {
+		t.Fatalf("mismatch! got\n%x\n, expected\n%x", dst, msg)
+	}
 }

pkg/cryptstate/mode_null.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2012 The Grumble Authors
+// The use of this source code is goverened by a BSD-style
+// license that can be found in the LICENSE-file.
+
+package cryptstate
+
+// nullMode implements the NULL CryptoMode
+type nullMode struct {}
+
+// NonceSize returns the nonce size to be used with NULL.
+func (n *nullMode) NonceSize() int {
+	return 1
+}
+
+// KeySize returns the key size to be used with NULL.
+func (n *nullMode) KeySize() int {
+	return 0
+}
+
+// Overhead returns the overhead that a ciphertext has over a plaintext.
+func (n *nullMode) Overhead() int {
+	return 0
+}
+
+// SetKey sets a new key. The key must have a length equal to KeySize().
+func (n *nullMode) SetKey(key []byte) {
+}
+
+// Encrypt encrypts a message using NULL and outputs it to dst.
+func (n *nullMode) Encrypt(dst []byte, src []byte, nonce []byte) {
+	copy(dst, src)
+}
+
+// Decrypt decrypts a message using NULL and outputs it to dst.
+func (n *nullMode) Decrypt(dst []byte, src []byte, nonce []byte) bool {
+	copy(dst, src)
+	return true
+}