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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.security.provider;

import javax.crypto.Mac;

import javax.crypto.spec.SecretKeySpec;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import java.security.NoSuchProviderException;

import java.security.SecureRandomParameters;

import java.util.Arrays;

import java.util.Collections;

import java.util.HexFormat;

import java.util.List;

public class HmacDrbg extends AbstractHashDrbg {

    private Mac mac;

    private String macAlg;

    private byte[] v;

    private byte[] k;

    public HmacDrbg(SecureRandomParameters params) {

        mechName = "HMAC_DRBG";

        configure(params);

    }

    private void status() {

        if (debug != null) {

            debug.println(this, "V = " + HexFormat.of().formatHex(v));

            debug.println(this, "Key = " + HexFormat.of().formatHex(k));

            debug.println(this, "reseed counter = " + reseedCounter);

        }

    }

    // 800-90Ar1 10.1.2.2: HMAC_DRBG Update Process

    private void update(List<byte[]> inputs) {

        try {

            // Step 1. K = HMAC (K, V || 0x00 || provided_data).

            mac.init(new SecretKeySpec(k, macAlg));

            mac.update(v);

            mac.update((byte) 0);

            for (byte[] input: inputs) {

                mac.update(input);

            }

            k = mac.doFinal();

            // Step 2. V = HMAC (K, V).

            mac.init(new SecretKeySpec(k, macAlg));

            v = mac.doFinal(v);

            if (!inputs.isEmpty()) {

                // Step 4. K = HMAC (K, V || 0x01 || provided_data).

                mac.update(v);

                mac.update((byte) 1);

                for (byte[] input: inputs) {

                    mac.update(input);

                }

                k = mac.doFinal();

                // Step 5. V=HMAC(K,V).

                mac.init(new SecretKeySpec(k, macAlg));

                v = mac.doFinal(v);

            } // else Step 3

            // Step 6. Return

        } catch (InvalidKeyException e) {

            throw new InternalError(e);

        }

    }

    /**

     * This call, used by the constructors, instantiates the digest.

     */

    @Override

    protected void initEngine() {

        macAlg = "HmacSHA" + algorithm.substring(4);

        try {

            /*

             * Use the local SunJCE implementation to avoid native

             * performance overhead.

             */

            mac = Mac.getInstance(macAlg, "SunJCE");

        } catch (NoSuchProviderException | NoSuchAlgorithmException e) {

            // Fallback to any available.

            try {

                mac = Mac.getInstance(macAlg);

            } catch (NoSuchAlgorithmException exc) {

                throw new InternalError(

                    "internal error: " + macAlg + " not available.", exc);

            }

        }

    }

    // This method is used by both instantiation and reseeding.

    @Override

    protected final synchronized void hashReseedInternal(List<byte[]> input) {

        // 800-90Ar1 10.1.2.3: Instantiate Process.

        // 800-90Ar1 10.1.2.4: Reseed Process.

        if (v == null) {

            k = new byte[outLen];

            v = new byte[outLen];

            Arrays.fill(v, (byte) 1);

        }

        // Step 2: HMAC_DRBG_Update

        update(input);

        // Step 3: reseed_counter = 1.

        reseedCounter = 1;

        //status();

        // Step 4: Return

    }

    /**

     * Generates a user-specified number of random bytes.

     *

     * @param result the array to be filled in with random bytes.

     */

    @Override

    public synchronized void generateAlgorithm(

            byte[] result, byte[] additionalInput) {

        if (debug != null) {

            debug.println(this, "generateAlgorithm");

        }

        // 800-90Ar1 10.1.2.5: HMAC_DRBG_Generate Process

        // Step 1: Check reseed_counter. Will not fail. Already checked in

        // AbstractDrbg#engineNextBytes.

        // Step 2. HMAC_DRBG_Update

        if (additionalInput != null) {

            update(Collections.singletonList(additionalInput));

        }

        // Step 3. temp = Null.

        int pos = 0;

        int len = result.length;

        // Step 4. Loop

        while (len > 0) {

            // Step 4.1 V = HMAC (Key, V).

            try {

                mac.init(new SecretKeySpec(k, macAlg));

            } catch (InvalidKeyException e) {

                throw new InternalError(e);

            }

            v = mac.doFinal(v);

            // Step 4.2 temp = temp || V.

            System.arraycopy(v, 0, result, pos,

                    len > outLen ? outLen : len);

            len -= outLen;

            if (len <= 0) {

                // shortcut, so that pos needn't be updated

                break;

            }

            pos += outLen;

        }

        // Step 5: No need to truncate

        // Step 6. HMAC_DRBG_Update (additional_input, Key, V).

        if (additionalInput != null) {

            update(Collections.singletonList(additionalInput));

        } else {

            update(Collections.emptyList());

        }

        // Step 7. reseed_counter = reseed_counter + 1.

        reseedCounter++;

        //status();

        // Step 8. Return

    }

}