/*

 * Copyright (c) 2013, 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.

 *

 * 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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 * questions.

 */

/**

 * @test

 * @bug 6425477

 * @summary Better support for generation of high entropy random numbers

 * @run main/othervm StrongSeedReader

 */

import java.io.*;

import java.net.*;

import java.security.SecureRandom;

/**

 * A simple test which takes into account knowledge about the underlying

 * implementation. This may change if the implementations change.

 *

 * Create a new EGD file with known bytes, then set the EGD System property. The

 * data read should be the same as what was written.

 */

public class StrongSeedReader {

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

        // Skip Windows, the SHA1PRNG uses CryptGenRandom.

        if (System.getProperty("os.name", "unknown").startsWith("Windows")) {

            return;

        }

        File file = null;

        try {

            file = new File(System.getProperty("java.io.tmpdir"),

                    "StrongSeedReader.tmpdata");

            // write a bunch of 0's to the file.

            FileOutputStream fos = new FileOutputStream(file);

            fos.write(new byte[2048]);

            System.setProperty("java.security.egd", file.toURI().toString());

            testSeed("NativePRNG");

            testSeed("SHA1PRNG");

        } finally {

            if (file != null) {

                file.delete();

            }

        }

    }

    private static void testSeed(String alg) throws Exception {

        System.out.println("Testing: " + alg);

        SecureRandom sr = SecureRandom.getInstance(alg);

        byte[] ba = sr.generateSeed(20);

        // We should get back a bunch of zeros from the file.

        for (byte b : ba) {

            if (b != 0) {

                throw new Exception("Byte != 0");

            }

        }

    }

}