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 *

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

 * accompanied this code).

 *

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

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import sun.security.provider.AbstractDrbg;

import sun.security.provider.EntropySource;

import java.lang.reflect.Field;

import java.lang.reflect.Modifier;

import java.security.DrbgParameters;

import java.security.SecureRandom;

import java.security.Security;

/**

 * @test

 * @bug 8051408

 * @modules java.base/sun.security.provider

 * @run main/othervm CommonSeeder

 * @summary check entropy reading of DRBGs

 */

public class CommonSeeder {

    static class MyES implements EntropySource {

        int count = 100;

        int lastCount = 100;

        @Override

        public byte[] getEntropy(int minEntropy, int minLength,

                                 int maxLength, boolean pr) {

            count--;

            return new byte[minLength];

        }

        /**

         * Confirms genEntropy() has been called {@code less} times

         * since last check.

         */

        public void checkUsage(int less) throws Exception {

            if (lastCount != count + less) {

                throw new Exception(String.format(

                        "lastCount = %d, count = %d, less = %d",

                        lastCount, count, less));

            }

            lastCount = count;

        }

    }

    public static void main(String[] args) throws Exception {

        byte[] result = new byte[10];

        MyES es = new MyES();

        // Set es as the default entropy source, overriding SeedGenerator.

        setDefaultSeeder(es);

        // Nothing happened yet

        es.checkUsage(0);

        SecureRandom sr;

        sr = SecureRandom.getInstance("DRBG");

        // No entropy reading if only getInstance

        es.checkUsage(0);

        // Entropy is read at 1st nextBytes of the 1st DRBG

        sr.nextInt();

        es.checkUsage(1);

        for (String mech : new String[]{"Hash_DRBG", "HMAC_DRBG", "CTR_DRBG"}) {

            System.out.println("Testing " + mech + "...");

            // DRBG with pr_false will never read entropy again no matter

            // if nextBytes or reseed is called.

            Security.setProperty("securerandom.drbg.config", mech);

            sr = SecureRandom.getInstance("DRBG");

            sr.nextInt();

            sr.reseed();

            es.checkUsage(0);

            // DRBG with pr_true always read from default entropy, and

            // its nextBytes always reseed itself

            Security.setProperty("securerandom.drbg.config",

                    mech + ",pr_and_reseed");

            sr = SecureRandom.getInstance("DRBG");

            sr.nextInt();

            es.checkUsage(2); // one instantiate, one reseed

            sr.nextInt();

            es.checkUsage(1); // one reseed in nextBytes

            sr.reseed();

            es.checkUsage(1); // one reseed

            sr.nextBytes(result, DrbgParameters.nextBytes(-1, false, null));

            es.checkUsage(0); // pr_false for this call

            sr.nextBytes(result, DrbgParameters.nextBytes(-1, true, null));

            es.checkUsage(1); // pr_true for this call

            sr.reseed(DrbgParameters.reseed(true, null));

            es.checkUsage(1); // reseed from es

            sr.reseed(DrbgParameters.reseed(false, null));

            es.checkUsage(0); // reseed from AbstractDrbg.SeederHolder.seeder

        }

    }

    static void setDefaultSeeder(EntropySource es) throws Exception {

        Field f = AbstractDrbg.class.getDeclaredField("defaultES");

        f.setAccessible(true);  // no more private

        Field f2 = Field.class.getDeclaredField("modifiers");

        f2.setAccessible(true);

        f2.setInt(f, f2.getInt(f) - Modifier.FINAL);    // no more final

        f.set(null, es);

    }

}