/*

 * Copyright 2003 Sun Microsystems, Inc.  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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.security.pkcs11;

import java.util.*;

import java.security.*;

import sun.security.pkcs11.wrapper.*;

import sun.security.pkcs11.wrapper.PKCS11Constants.*;

/**

 * SecureRandom implementation class. Some tokens support only

 * C_GenerateRandom() and not C_SeedRandom(). In order not to lose an

 * application specified seed, we create a SHA1PRNG that we mix with in that

 * case.

 *

 * Note that since SecureRandom is thread safe, we only need one

 * instance per PKCS#11 token instance. It is created on demand and cached

 * in the SunPKCS11 class.

 *

 * Also note that we obtain the PKCS#11 session on demand, no need to tie one

 * up.

 *

 * @author  Andreas Sterbenz

 * @since   1.5

 */

final class P11SecureRandom extends SecureRandomSpi {

    private static final long serialVersionUID = -8939510236124553291L;

    // token instance

    private final Token token;

    // PRNG for mixing, non-null if active (i.e. setSeed() has been called)

    private volatile SecureRandom mixRandom;

    // buffer, if mixing is used

    private byte[] mixBuffer;

    // bytes remaining in buffer, if mixing is used

    private int buffered;

    P11SecureRandom(Token token) {

        this.token = token;

    }

    // see JCA spec

    protected synchronized void engineSetSeed(byte[] seed) {

        if (seed == null) {

            throw new NullPointerException("seed must not be null");

        }

        Session session = null;

        try {

            session = token.getOpSession();

            token.p11.C_SeedRandom(session.id(), seed);

        } catch (PKCS11Exception e) {

            // cannot set seed

            // let a SHA1PRNG use that seed instead

            SecureRandom random = mixRandom;

            if (random != null) {

                random.setSeed(seed);

            } else {

                try {

                    mixBuffer = new byte[20];

                    random = SecureRandom.getInstance("SHA1PRNG");

                    // initialize object before assigning to class field

                    random.setSeed(seed);

                    mixRandom = random;

                } catch (NoSuchAlgorithmException ee) {

                    throw new ProviderException(ee);

                }

            }

        } finally {

            token.releaseSession(session);

        }

    }

    // see JCA spec

    protected void engineNextBytes(byte[] bytes) {

        if ((bytes == null) || (bytes.length == 0)) {

            return;

        }

        Session session = null;

        try {

            session = token.getOpSession();

            token.p11.C_GenerateRandom(session.id(), bytes);

            mix(bytes);

        } catch (PKCS11Exception e) {

            throw new ProviderException("nextBytes() failed", e);

        } finally {

            token.releaseSession(session);

        }

    }

    // see JCA spec

    protected byte[] engineGenerateSeed(int numBytes) {

        byte[] b = new byte[numBytes];

        engineNextBytes(b);

        return b;

    }

    private void mix(byte[] b) {

        SecureRandom random = mixRandom;

        if (random == null) {

            // avoid mixing if setSeed() has never been called

            return;

        }

        synchronized (this) {

            int ofs = 0;

            int len = b.length;

            while (len-- > 0) {

                if (buffered == 0) {

                    random.nextBytes(mixBuffer);

                    buffered = mixBuffer.length;

                }

                b[ofs++] ^= mixBuffer[mixBuffer.length - buffered];

                buffered--;

            }

        }

    }

}