x/crypto/scrypt: add compareHashAndPassword

scrypt/scrypt.go

@@ -210,3 +210,16 @@ func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error) {
 
 	return pbkdf2.Key(password, b, 1, keyLen, sha256.New), nil
 }
+
+// CompareHashAndPassword compares a scrypt hashed password with its possible
+// plaintext equivalent. Returns nil on success, or an error on failure.
+func CompareHashAndPassword(hashedPassword, password, salt []byte, N, r, p, keyLen int) error{
+	pass, err := scrypt.Key(password, salt, N, r, p, keyLen)
+	if err != nil {
+		return err
+	}
+	if subtle.ConstantTimeCompare(hashedPassword, pass) == 1 {
+		return nil
+	}
+	return errors.New("crypto/scrypt: hashedPassword is not the hash of the given password")
+}

scrypt/scrypt_test.go

@@ -109,23 +109,6 @@ var good = []testVector{
 			0x87,
 		},
 	},
-	/*
-		// Disabled: needs 1 GiB RAM and takes too long for a simple test.
-		{
-			"pleaseletmein", "SodiumChloride",
-			1048576, 8, 1,
-			[]byte{
-				0x21, 0x01, 0xcb, 0x9b, 0x6a, 0x51, 0x1a, 0xae, 0xad,
-				0xdb, 0xbe, 0x09, 0xcf, 0x70, 0xf8, 0x81, 0xec, 0x56,
-				0x8d, 0x57, 0x4a, 0x2f, 0xfd, 0x4d, 0xab, 0xe5, 0xee,
-				0x98, 0x20, 0xad, 0xaa, 0x47, 0x8e, 0x56, 0xfd, 0x8f,
-				0x4b, 0xa5, 0xd0, 0x9f, 0xfa, 0x1c, 0x6d, 0x92, 0x7c,
-				0x40, 0xf4, 0xc3, 0x37, 0x30, 0x40, 0x49, 0xe8, 0xa9,
-				0x52, 0xfb, 0xcb, 0xf4, 0x5c, 0x6f, 0xa7, 0x7a, 0x41,
-				0xa4,
-			},
-		},
-	*/
 }
 
 var bad = []testVector{
@@ -135,6 +118,41 @@ var bad = []testVector{
 	{"p", "s", 16, maxInt / 2, maxInt / 2, nil}, // p * r too large
 }
 
+var mismatchedCases = []testVector{
+	{
+		"password",
+		"NaCl",
+		1024,8, 16,
+		[]byte{
+			0x70, 0x23, 0xbd, 0xcb, 0x3a, 0xfd, 0x73, 0x48, 0x46,
+			0x1c, 0x06, 0xcd, 0x81, 0xfd, 0x38, 0xeb, 0xfd, 0xa8,
+			0xfb, 0xba, 0x90, 0x4f, 0x8e, 0x3e, 0xa9, 0xb5, 0x43,
+			0xf6, 0x54, 0x5d, 0xa1, 0xf2, 0xd5, 0x43, 0x29, 0x55,
+			0x61, 0x3f, 0x0f, 0xcf, 0x62, 0xd4, 0x97, 0x05, 0x24,
+			0x2a, 0x9a, 0xf9, 0xe6, 0x1e, 0x85, 0xdc, 0x0d, 0x65,
+			0x1e, 0x40, 0xdf, 0xcf, 0x01, 0x7b, 0x45, 0x57, 0x58,
+			0x87,
+		},
+
+	},
+	{
+		"pleaseletmein", "SodiumChloride",
+		16384, 8, 1,
+		[]byte{
+			0xfd, 0xba, 0xbe, 0x1c, 0x9d, 0x34, 0x72, 0x00, 0x78,
+			0x56, 0xe7, 0x19, 0x0d, 0x01, 0xe9, 0xfe, 0x7c, 0x6a,
+			0xd7, 0xcb, 0xc8, 0x23, 0x78, 0x30, 0xe7, 0x73, 0x76,
+			0x63, 0x4b, 0x37, 0x31, 0x62, 0x2e, 0xaf, 0x30, 0xd9,
+			0x2e, 0x22, 0xa3, 0x88, 0x6f, 0xf1, 0x09, 0x27, 0x9d,
+			0x98, 0x30, 0xda, 0xc7, 0x27, 0xaf, 0xb9, 0x4a, 0x83,
+			0xee, 0x6d, 0x83, 0x60, 0xcb, 0xdf, 0xa2, 0xcc, 0x06,
+			0x40,
+		},
+	},
+
+
+}
+
 func TestKey(t *testing.T) {
 	for i, v := range good {
 		k, err := Key([]byte(v.password), []byte(v.salt), v.N, v.r, v.p, len(v.output))
@@ -153,10 +171,35 @@ func TestKey(t *testing.T) {
 	}
 }
 
+func TestCompareHashAndPassword(t *testing.T) {
+	for i, v := range good {
+		err := CompareHashAndPassword(v.output, []byte(v.password), []byte(v.salt), v.N, v.r, v.p, len(v.output))
+		if err != nil {
+			t.Errorf("%d: %v should be matched %s", i, v.output, v.password)
+		}
+	}
+	for i, v := range mismatchedCases {
+		err := CompareHashAndPassword(v.output, []byte(v.password), []byte(v.salt), v.N, v.r, v.p, len(v.output))
+		if err == nil {
+			t.Errorf("%d: expected error, got nil", i)
+		}
+	}
+}
+
 var sink []byte
 
 func BenchmarkKey(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		sink, _ = Key([]byte("password"), []byte("salt"), 1<<15, 8, 1, 64)
 	}
 }
+
+func BenchmarkEqual(b *testing.B) {
+	b.StopTimer()
+	passwd := []byte("somepassword")
+	hash, _ := Key(passwd, "NaCl", 1024, 10, 16, 32)
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		CompareHashAndPassword(hash, passwd, "NaCl", 1024, 10, 16, 32)
+	}
+}