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 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * 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 sun.security.util.HexDumpEncoder;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public abstract class AbstractHashDrbg extends AbstractDrbg {

    protected int outLen;
    protected int seedLen;

    private static int alg2strength(String algorithm) {
        switch (algorithm.toUpperCase(Locale.ROOT)) {
            case "SHA-224":
            case "SHA-512/224":
                return 192;
            case "SHA-256":
            case "SHA-512/256":
            case "SHA-384":
            case "SHA-512":
                return 256;
            default:
                throw new IllegalArgumentException(algorithm +
                        " not supported in Hash_DBRG");
        }
    }

    protected void chooseAlgorithmAndStrength() {
        if (requestedAlgorithm != null) {
            algorithm = requestedAlgorithm.toUpperCase(Locale.ROOT);
            int supportedStrength = alg2strength(algorithm);
            if (requestedInstantiationSecurityStrength >= 0) {
                int tryStrength = getStandardStrength(
                        requestedInstantiationSecurityStrength);
                if (tryStrength > supportedStrength) {
                    throw new IllegalArgumentException(algorithm +
                            " does not support strength " +
                            requestedInstantiationSecurityStrength);
                }
                this.securityStrength = tryStrength;
            } else {
                this.securityStrength = DEFAULT_STRENGTH > supportedStrength ?
                        supportedStrength : DEFAULT_STRENGTH;
            }
        } else {
            int tryStrength = (requestedInstantiationSecurityStrength < 0) ?
                    DEFAULT_STRENGTH : requestedInstantiationSecurityStrength;
            tryStrength = getStandardStrength(tryStrength);
            // The default algorithm which is enough for all strengths.
            // Remember to sync with "securerandom.drbg.config" in java.security
            algorithm = "SHA-256";
            this.securityStrength = tryStrength;
        }
        switch (algorithm.toUpperCase(Locale.ROOT)) {
            case "SHA-224":
            case "SHA-512/224":
                this.seedLen = 440 / 8;
                this.outLen = 224 / 8;
                break;
            case "SHA-256":
            case "SHA-512/256":
                this.seedLen = 440 / 8;
                this.outLen = 256 / 8;
                break;
            case "SHA-384":
                this.seedLen = 888 / 8;
                this.outLen = 384 / 8;
                break;
            case "SHA-512":
                this.seedLen = 888 / 8;
                this.outLen = 512 / 8;
                break;
            default:
                throw new IllegalArgumentException(algorithm +
                        " not supported in Hash_DBRG");
        }
        this.minLength = this.securityStrength / 8;
    }

    @Override
    public void instantiateAlgorithm(byte[] entropy) {
        if (debug != null) {
            debug.println(this, "instantiate");
        }

        // 800-90Ar1 10.1.1.2: Hash_DRBG Instantiate Process.
        // 800-90Ar1 10.1.2.3: Hmac_DRBG Instantiate Process.

        // Step 1: entropy_input || nonce || personalization_string.
        List<byte[]> inputs = new ArrayList<>(3);
        inputs.add(entropy);
        inputs.add(nonce);
        if (personalizationString != null) {
            inputs.add(personalizationString);
        }
        hashReseedInternal(inputs);
    }

    @Override
    protected void reseedAlgorithm(
            byte[] ei,
            byte[] additionalInput) {
        if (debug != null) {
            debug.println(this, "reseedAlgorithm\n" +
                    new HexDumpEncoder().encodeBuffer(ei) + "\n" +
                    ((additionalInput == null) ? "" :
                        new HexDumpEncoder().encodeBuffer(additionalInput)));
        }

        // 800-90Ar1 10.1.1.3: Hash_DRBG Reseed Process.
        // 800-90Ar1 10.1.2.4: Hmac_DRBG Reseed Process.

        // Step 1: entropy_input || additional_input.
        List<byte[]> inputs = new ArrayList<>(2);
        inputs.add(ei);
        if (additionalInput != null) {
            inputs.add(additionalInput);
        }
        hashReseedInternal(inputs);
    }

    
Operates on multiple inputs.
Params:
inputs – not null, each element neither null/**
     * Operates on multiple inputs.
     * @param inputs not null, each element neither null
     */
    protected abstract void hashReseedInternal(List<byte[]> inputs);
}