/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package keywhiz.auth.cookie;

import java.security.SecureRandom;
import javax.crypto.AEADBadTagException;
import keywhiz.FakeRandom;
import org.junit.Before;
import org.junit.Test;

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.assertj.core.api.Assertions.assertThat;

public class GCMEncryptorTest {
  final byte[] testMessage = "encryption works".getBytes(UTF_8);

  GCMEncryptor encryptor;

  @Before
  public void setup() throws Exception {
    SecureRandom fakeRandom = FakeRandom.create();
    byte[] key = new byte[32];
    fakeRandom.nextBytes(key);
    encryptor = new GCMEncryptor(key, fakeRandom);
  }

  @Test
  public void encryptsAndDecrypts() throws Exception {
    byte[] ciphertext = encryptor.encrypt(testMessage);

    assertThat(ciphertext).isNotEqualTo(testMessage);

    byte[] result = encryptor.decrypt(ciphertext);

    assertThat(testMessage).isEqualTo(result);
  }

  @Test(expected = AEADBadTagException.class)
  public void failsWhenMacIsIncorrect() throws Exception {
    byte[] ciphertext = encryptor.encrypt(testMessage);
    int flipIndex = ciphertext.length - 2;
    byte flipped = (byte)((int)ciphertext[flipIndex] ^ 1);
    ciphertext[flipIndex] = flipped;
    encryptor.decrypt(ciphertext);
  }

  @Test
  public void generatesUniqueNonces() throws Exception {
    byte[] ciphertext = encryptor.encrypt(testMessage);
    byte[] firstIV = GCMEncryptor.getNonce(ciphertext);
    ciphertext = encryptor.encrypt(testMessage);
    byte[] secondIV = GCMEncryptor.getNonce(ciphertext);

    assertThat(firstIV).isNotEqualTo(secondIV);
  }
}