tests/tests/identity/src/android/security/identity/cts/HkdfTest.java

/*
 * Copyright 2019 The Android Open Source Project
 *
 * 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 android.security.identity.cts;

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

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

import java.security.GeneralSecurityException;
import java.util.Random;

/*
 * This is based on https://github.com/google/tink/blob/master/java/src/test/java/com/google
 * /crypto/tink/subtle/HkdfTest.java
 * which is also Copyright (c) Google and licensed under the Apache 2 license.
 */
@RunWith(JUnit4.class)
public class HkdfTest {

    static Random sRandom = new Random();

    /** Encodes a byte array to hex. */
    static String hexEncode(final byte[] bytes) {
        String chars = "0123456789abcdef";
        StringBuilder result = new StringBuilder(2 * bytes.length);
        for (byte b : bytes) {
            // convert to unsigned
            int val = b & 0xff;
            result.append(chars.charAt(val / 16));
            result.append(chars.charAt(val % 16));
        }
        return result.toString();
    }

    /** Decodes a hex string to a byte array. */
    static byte[] hexDecode(String hex) {
        if (hex.length() % 2 != 0) {
            throw new IllegalArgumentException("Expected a string of even length");
        }
        int size = hex.length() / 2;
        byte[] result = new byte[size];
        for (int i = 0; i < size; i++) {
            int hi = Character.digit(hex.charAt(2 * i), 16);
            int lo = Character.digit(hex.charAt(2 * i + 1), 16);
            if ((hi == -1) || (lo == -1)) {
                throw new IllegalArgumentException("input is not hexadecimal");
            }
            result[i] = (byte) (16 * hi + lo);
        }
        return result;
    }

    static byte[] randBytes(int numBytes) {
        byte[] bytes = new byte[numBytes];
        sRandom.nextBytes(bytes);
        return bytes;
    }

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

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

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

    @Test
    public void testInvalidCodeSize() throws Exception {
        try {
            Util.computeHkdf("HmacSha256", new byte[0], new byte[0], new byte[0], 32 * 256);
            fail("Invalid size, should have thrown exception");
        } catch (RuntimeException expected) {

            // Expected
        }
    }

    /**
     * Tests the implementation against the test vectors from RFC 5869.
     */
    @Test
    public void testVectors() throws Exception {
        // Test case 1
        assertEquals(
                "3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf"
                + "1a5a4c5db02d56ecc4c5bf34007208d5b887185865",
                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(
                "085a01ea1b10f36933068b56efa5ad81a4f14b822f"
                + "5b091568a9cdd4f155fda2c22e422478d305f3f896",
                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 hexEncode(
                Util.computeHkdf(macAlgorithm, hexDecode(ikmHex), hexDecode(saltHex),
                        hexDecode(infoHex), size));
    }

}