// Copyright 2017 Google 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 com.google.crypto.tink.subtle;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThrows;

import java.security.GeneralSecurityException;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Unit tests for {@link Hkdf}. */
@RunWith(JUnit4.class)
public class HkdfTest {

  @Test
  public void testNullSaltOrInfo() throws Exception {
    byte[] ikm = Random.randBytes(20);
    byte[] info = Random.randBytes(20);
    int size = 40;

    byte[] hkdfWithNullSalt = Hkdf.computeHkdf("HmacSha256", ikm, null, info, size);
    byte[] hkdfWithEmptySalt =  Hkdf.computeHkdf("HmacSha256", ikm, new byte[0], info, size);
    assertArrayEquals(hkdfWithNullSalt, hkdfWithEmptySalt);

    byte[] salt = Random.randBytes(20);
    byte[] hkdfWithNullInfo = Hkdf.computeHkdf("HmacSha256", ikm, salt, null, size);
    byte[] hkdfWithEmptyInfo =  Hkdf.computeHkdf("HmacSha256", ikm, salt, new byte[0], size);
    assertArrayEquals(hkdfWithNullInfo, hkdfWithEmptyInfo);
  }

  @Test
  public void testInvalidCodeSize() throws Exception {
    assertThrows(
        GeneralSecurityException.class,
        () -> Hkdf.computeHkdf("HmacSha256", new byte[0], new byte[0], new byte[0], 32 * 256));
  }

  /**
   * Tests the implementation against the test vectors from RFC 5869.
   */
  @Test
  public void testVectors() throws Exception {
    // Test case 1
    assertEquals(
        "3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf34007208d5b887185865",
        computeHkdfHex("HmacSha256",
          "0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b",
          "000102030405060708090a0b0c",
          "f0f1f2f3f4f5f6f7f8f9",
          42));

    // Test case 2
    assertEquals(
        "b11e398dc80327a1c8e7f78c596a49344f012eda2d4efad8a050cc4c19afa97c"
        + "59045a99cac7827271cb41c65e590e09da3275600c2f09b8367793a9aca3db71"
        + "cc30c58179ec3e87c14c01d5c1f3434f1d87",
        computeHkdfHex("HmacSha256",
          "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f"
          + "202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"
          + "404142434445464748494a4b4c4d4e4f",
          "606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f"
          + "808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f"
          + "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf",
          "b0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
          + "d0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeef"
          + "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff",
          82));

    // Test case 3: salt is empty
    assertEquals(
        "8da4e775a563c18f715f802a063c5a31b8a11f5c5ee1879ec3454e5f3c738d2d"
        + "9d201395faa4b61a96c8",
        computeHkdfHex("HmacSha256", "0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b", "", "", 42));

    // Test Case 4
    assertEquals(
        "085a01ea1b10f36933068b56efa5ad81a4f14b822f5b091568a9cdd4f155fda2c22e422478d305f3f896",
        computeHkdfHex(
            "HmacSha1",
            "0b0b0b0b0b0b0b0b0b0b0b",
            "000102030405060708090a0b0c",
            "f0f1f2f3f4f5f6f7f8f9",
            42));

    // Test Case 5
    assertEquals(
        "0bd770a74d1160f7c9f12cd5912a06ebff6adcae899d92191fe4305673ba2ffe"
        + "8fa3f1a4e5ad79f3f334b3b202b2173c486ea37ce3d397ed034c7f9dfeb15c5e"
        + "927336d0441f4c4300e2cff0d0900b52d3b4",
        computeHkdfHex(
            "HmacSha1",
            "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f"
            + "202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"
            + "404142434445464748494a4b4c4d4e4f",
            "606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f"
            + "808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f"
            + "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf",
            "b0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
            + "d0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeef"
            + "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff",
            82));

    // Test Case 6: salt is empty
    assertEquals(
        "0ac1af7002b3d761d1e55298da9d0506b9ae52057220a306e07b6b87e8df21d0"
        + "ea00033de03984d34918",
        computeHkdfHex("HmacSha1", "0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b", "", "", 42));

    // Test Case 7
    assertEquals(
        "2c91117204d745f3500d636a62f64f0ab3bae548aa53d423b0d1f27ebba6f5e5"
        + "673a081d70cce7acfc48",
        computeHkdfHex("HmacSha1", "0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c", "", "", 42));
  }



  /**
   * Test version of Hkdf where all inputs and outputs are hexadecimal.
   */
  private String computeHkdfHex(String macAlgorithm, String ikmHex, String saltHex, String infoHex,
      int size) throws GeneralSecurityException {
    return Hex.encode(
        Hkdf.computeHkdf(
            macAlgorithm, Hex.decode(ikmHex), Hex.decode(saltHex), Hex.decode(infoHex), size));
  }
}