com.yubico.yubikit.fido.ctap.PinUvAuthProtocolV2 Maven / Gradle / Ivy

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This module provides FIDO support for the YubiKit SDK.
There is a newer version: 2.7.0
/*
 * Copyright (C) 2023 Yubico.
 *
 * 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.yubico.yubikit.fido.ctap;

import com.yubico.yubikit.core.util.RandomUtils;

import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.Mac;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * Implements PIN/UV Auth Protocol 2
 *
 * @see authenticatorClientPIN.
 * @see PIN/UV Auth Protocol Two.
 */

public class PinUvAuthProtocolV2 extends PinUvAuthProtocolV1 {
    public static final int VERSION = 2;

    private static final String HKDF_ALG = "HmacSHA256";
    private static final byte[] HKDF_SALT = new byte[32];
    private static final byte[] HKDF_INFO_HMAC = "CTAP2 HMAC key".getBytes(StandardCharsets.UTF_8);
    private static final byte[] HKDF_INFO_AES = "CTAP2 AES key".getBytes(StandardCharsets.UTF_8);
    private static final int HKDF_LENGTH = 32;

    @Override
    public int getVersion() {
        return VERSION;
    }

    @Override
    public byte[] kdf(byte[] z) {
        byte[] hmacKey = null;
        byte[] aesKey = null;
        try {
            hmacKey = new Hkdf(HKDF_ALG).digest(
                    z,
                    HKDF_SALT,
                    HKDF_INFO_HMAC,
                    HKDF_LENGTH);

            aesKey = new Hkdf(HKDF_ALG).digest(
                    z,
                    HKDF_SALT,
                    HKDF_INFO_AES,
                    HKDF_LENGTH);

            return ByteBuffer.allocate(hmacKey.length + aesKey.length)
                    .put(hmacKey)
                    .put(aesKey)
                    .array();
        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new IllegalStateException(e);
        } finally {
            if (hmacKey != null) {
                Arrays.fill(hmacKey, (byte) 0);
            }
            if (aesKey != null) {
                Arrays.fill(aesKey, (byte) 0);
            }
        }
    }

    @Override
    public byte[] encrypt(byte[] key, byte[] plaintext) {
        byte[] aesKey = null;
        try {
            aesKey = Arrays.copyOfRange(key, 32, key.length);
            byte[] iv = RandomUtils.getRandomBytes(16);

            final byte[] ciphertext =
                    getCipher(Cipher.ENCRYPT_MODE, aesKey, iv)
                            .doFinal(plaintext);
            return ByteBuffer.allocate(iv.length + ciphertext.length)
                    .put(iv)
                    .put(ciphertext)
                    .array();
        } catch (IllegalBlockSizeException | BadPaddingException e) {
            throw new IllegalStateException(e);
        } finally {
            if (aesKey != null) {
                Arrays.fill(aesKey, (byte) 0);
            }
        }
    }

    @Override
    public byte[] decrypt(byte[] key, byte[] ciphertext) {
        byte[] aesKey = null;
        try {
            aesKey = Arrays.copyOfRange(key, 32, key.length);
            byte[] iv = Arrays.copyOf(ciphertext, 16);
            byte[] ct = Arrays.copyOfRange(ciphertext, 16, ciphertext.length);
            return getCipher(Cipher.DECRYPT_MODE, aesKey, iv).doFinal(ct);
        } catch (BadPaddingException | IllegalBlockSizeException e) {
            throw new IllegalStateException(e);
        } finally {
            if (aesKey != null) {
                Arrays.fill(aesKey, (byte) 0);
            }
        }
    }

    @Override
    public byte[] authenticate(byte[] key, byte[] message) {
        final String MAC_ALG = "HmacSHA256";
        byte[] hmacKey = Arrays.copyOf(key, 32);
        Mac mac;
        try {
            mac = Mac.getInstance(MAC_ALG);
            mac.init(new SecretKeySpec(hmacKey, MAC_ALG));
        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new RuntimeException(e);
        }
        return mac.doFinal(message);
    }

    private Cipher getCipher(int mode, byte[] secret, byte[] iv) {
        try {
            Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
            cipher.init(
                    mode,
                    new SecretKeySpec(secret, "AES"),
                    new IvParameterSpec(iv));
            return cipher;
        } catch (NoSuchPaddingException |
                 NoSuchAlgorithmException |
                 InvalidAlgorithmParameterException |
                 InvalidKeyException e) {
            throw new IllegalStateException(e);
        }
    }
}