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/* SRPClient.java --

   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or (at

your option) any later version.

GNU Classpath 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 for more details.

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

along with GNU Classpath; if not, write to the Free Software

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

USA

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version.  */

package gnu.javax.crypto.sasl.srp;

import gnu.java.lang.CPStringBuilder;

import gnu.java.security.Configuration;

import gnu.java.security.Registry;

import gnu.java.security.hash.MD5;

import gnu.java.security.util.PRNG;

import gnu.java.security.util.Util;

import gnu.javax.crypto.assembly.Direction;

import gnu.javax.crypto.cipher.CipherFactory;

import gnu.javax.crypto.cipher.IBlockCipher;

import gnu.javax.crypto.key.IKeyAgreementParty;

import gnu.javax.crypto.key.IncomingMessage;

import gnu.javax.crypto.key.KeyAgreementException;

import gnu.javax.crypto.key.KeyAgreementFactory;

import gnu.javax.crypto.key.OutgoingMessage;

import gnu.javax.crypto.key.srp6.SRP6KeyAgreement;

import gnu.javax.crypto.sasl.ClientMechanism;

import gnu.javax.crypto.sasl.IllegalMechanismStateException;

import gnu.javax.crypto.sasl.InputBuffer;

import gnu.javax.crypto.sasl.IntegrityException;

import gnu.javax.crypto.sasl.OutputBuffer;

import gnu.javax.security.auth.Password;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.math.BigInteger;

import java.security.NoSuchAlgorithmException;

import java.util.Arrays;

import java.util.HashMap;

import java.util.StringTokenizer;

import java.util.logging.Logger;

import javax.security.auth.DestroyFailedException;

import javax.security.auth.callback.Callback;

import javax.security.auth.callback.NameCallback;

import javax.security.auth.callback.PasswordCallback;

import javax.security.auth.callback.UnsupportedCallbackException;

import javax.security.sasl.AuthenticationException;

import javax.security.sasl.SaslClient;

import javax.security.sasl.SaslException;

/**

 * The SASL-SRP client-side mechanism.

 */

public class SRPClient

    extends ClientMechanism

    implements SaslClient

{

  private static final Logger log = Logger.getLogger(SRPClient.class.getName());

  private String uid; // the unique key for this type of client

  private String U; // the authentication identity

  BigInteger N, g, A, B;

  private Password password; // the authentication credentials

  private byte[] s; // the user's salt

  private byte[] cIV, sIV; // client+server IVs, when confidentiality is on

  private byte[] M1, M2; // client+server evidences

  private byte[] cn, sn; // client's and server's nonce

  private SRP srp; // SRP algorithm instance used by this client

  private byte[] sid; // session ID when re-used

  private int ttl; // session time-to-live in seconds

  private byte[] sCB; // the peer's channel binding data

  private String L; // available options

  private String o;

  private String chosenIntegrityAlgorithm;

  private String chosenConfidentialityAlgorithm;

  private int rawSendSize = Registry.SASL_BUFFER_MAX_LIMIT;

  private byte[] K; // shared session key

  private boolean replayDetection = true; // whether Replay Detection is on

  private int inCounter = 0; // messages sequence numbers

  private int outCounter = 0;

  private IALG inMac, outMac; // if !null, use for integrity

  private CALG inCipher, outCipher; // if !null, use for confidentiality

  private IKeyAgreementParty clientHandler =

      KeyAgreementFactory.getPartyAInstance(Registry.SRP_SASL_KA);

  /** Our default source of randomness. */

  private PRNG prng = null;

  public SRPClient()

  {

    super(Registry.SASL_SRP_MECHANISM);

  }

  protected void initMechanism() throws SaslException

  {

    // we shall keep track of the sid (and the security context of this SRP

    // client) based on the initialisation parameters of an SRP session.

    // we shall compute a unique key for those parameters and key the sid

    // (and the security context) accordingly.

    // 1. compute the mapping key. use MD5 (the fastest) for this purpose

    final MD5 md = new MD5();

    byte[] b;

    b = authorizationID.getBytes();

    md.update(b, 0, b.length);

    b = serverName.getBytes();

    md.update(b, 0, b.length);

    b = protocol.getBytes();

    md.update(b, 0, b.length);

    if (channelBinding.length > 0)

      md.update(channelBinding, 0, channelBinding.length);

    uid = Util.toBase64(md.digest());

    if (ClientStore.instance().isAlive(uid))

      {

        final SecurityContext ctx = ClientStore.instance().restoreSession(uid);

        srp = SRP.instance(ctx.getMdName());

        sid = ctx.getSID();

        K = ctx.getK();

        cIV = ctx.getClientIV();

        sIV = ctx.getServerIV();

        replayDetection = ctx.hasReplayDetection();

        inCounter = ctx.getInCounter();

        outCounter = ctx.getOutCounter();

        inMac = ctx.getInMac();

        outMac = ctx.getOutMac();

        inCipher = ctx.getInCipher();

        outCipher = ctx.getOutCipher();

      }

    else

      {

        sid = new byte[0];

        ttl = 0;

        K = null;

        cIV = null;

        sIV = null;

        cn = null;

        sn = null;

      }

  }

  protected void resetMechanism() throws SaslException

  {

    try

      {

        password.destroy();

      }

    catch (DestroyFailedException dfe)

      {

        SaslException se = new SaslException("resetMechanism()");

        se.initCause(dfe);

        throw se;

      }

    password = null;

    M1 = null;

    K = null;

    cIV = null;

    sIV = null;

    inMac = outMac = null;

    inCipher = outCipher = null;

    sid = null;

    ttl = 0;

    cn = null;

    sn = null;

  }

  public boolean hasInitialResponse()

  {

    return true;

  }

  public byte[] evaluateChallenge(final byte[] challenge) throws SaslException

  {

    switch (state)

      {

      case 0:

        state++;

        return sendIdentities();

      case 1:

        state++;

        final byte[] result = sendPublicKey(challenge);

        try

          {

            password.destroy(); //don't need further this session

          }

        catch (DestroyFailedException x)

          {

            SaslException se = new SaslException("sendPublicKey()");

            se.initCause(se);

            throw se;

          }

        return result;

      case 2: // should only occur if session re-use was rejected

        if (! complete)

          {

            state++;

            return receiveEvidence(challenge);

          }

      // else fall through

      default:

        throw new IllegalMechanismStateException("evaluateChallenge()");

      }

  }

  protected byte[] engineUnwrap(final byte[] incoming, final int offset,

                                final int len) throws SaslException

  {

    if (Configuration.DEBUG)

      log.entering(this.getClass().getName(), "engineUnwrap");

    if (inMac == null && inCipher == null)

      throw new IllegalStateException("connection is not protected");

    // at this point one, or both, of confidentiality and integrity protection

    // services are active.

    final byte[] result;

    try

      {

        if (inMac != null)

          { // integrity bytes are at the end of the stream

            final int macBytesCount = inMac.length();

            final int payloadLength = len - macBytesCount;

            final byte[] received_mac = new byte[macBytesCount];

            System.arraycopy(incoming, offset + payloadLength, received_mac, 0,

                             macBytesCount);

            if (Configuration.DEBUG)

              log.fine("Got C (received MAC): " + Util.dumpString(received_mac));

            inMac.update(incoming, offset, payloadLength);

            if (replayDetection)

              {

                inCounter++;

                if (Configuration.DEBUG)

                  log.fine("inCounter=" + inCounter);

                inMac.update(new byte[] {

                    (byte)(inCounter >>> 24),

                    (byte)(inCounter >>> 16),

                    (byte)(inCounter >>> 8),

                    (byte) inCounter });

              }

            final byte[] computed_mac = inMac.doFinal();

            if (Configuration.DEBUG)

              log.fine("Computed MAC: " + Util.dumpString(computed_mac));

            if (! Arrays.equals(received_mac, computed_mac))

              throw new IntegrityException("engineUnwrap()");

            // deal with the payload, which can be either plain or encrypted

            if (inCipher != null)

              result = inCipher.doFinal(incoming, offset, payloadLength);

            else

              {

                result = new byte[len - macBytesCount];

                System.arraycopy(incoming, offset, result, 0, result.length);

              }

          }

        else // no integrity protection; just confidentiality

          result = inCipher.doFinal(incoming, offset, len);

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

        throw new SaslException("engineUnwrap()", x);

      }

    if (Configuration.DEBUG)

      log.exiting(this.getClass().getName(), "engineUnwrap");

    return result;

  }

  protected byte[] engineWrap(final byte[] outgoing, final int offset,

                              final int len) throws SaslException

  {

    if (Configuration.DEBUG)

      log.entering(this.getClass().getName(), "engineWrap");

    if (outMac == null && outCipher == null)

      throw new IllegalStateException("connection is not protected");

    // at this point one, or both, of confidentiality and integrity protection

    // services are active.

    byte[] result;

    try

      {

        final ByteArrayOutputStream out = new ByteArrayOutputStream();

        // Process the data

        if (outCipher != null)

          {

            result = outCipher.doFinal(outgoing, offset, len);

            if (Configuration.DEBUG)

              log.fine("Encoding c (encrypted plaintext): "

                       + Util.dumpString(result));

            out.write(result);

            if (outMac != null)

              {

                outMac.update(result);

                if (replayDetection)

                  {

                    outCounter++;

                    if (Configuration.DEBUG)

                      log.fine("outCounter=" + outCounter);

                    outMac.update(new byte[] {

                        (byte)(outCounter >>> 24),

                        (byte)(outCounter >>> 16),

                        (byte)(outCounter >>> 8),

                        (byte) outCounter });

                  }

                final byte[] C = outMac.doFinal();

                out.write(C);

                if (Configuration.DEBUG)

                  log.fine("Encoding C (integrity checksum): " + Util.dumpString(C));

              }

            // else confidentiality only; do nothing

          }

        else // no confidentiality; just integrity [+ replay detection]

          {

            if (Configuration.DEBUG)

              log.fine("Encoding p (plaintext): "

                       + Util.dumpString(outgoing, offset, len));

            out.write(outgoing, offset, len);

            outMac.update(outgoing, offset, len);

            if (replayDetection)

              {

                outCounter++;

                if (Configuration.DEBUG)

                  log.fine("outCounter=" + outCounter);

                outMac.update(new byte[] {

                    (byte)(outCounter >>> 24),

                    (byte)(outCounter >>> 16),

                    (byte)(outCounter >>> 8),

                    (byte) outCounter });

              }

            final byte[] C = outMac.doFinal();

            out.write(C);

            if (Configuration.DEBUG)

              log.fine("Encoding C (integrity checksum): " + Util.dumpString(C));

          }

        result = out.toByteArray();

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

        throw new SaslException("engineWrap()", x);

      }

    if (Configuration.DEBUG)

      log.exiting(this.getClass().getName(), "engineWrap");

    return result;

  }

  protected String getNegotiatedQOP()

  {

    if (inMac != null)

      {

        if (inCipher != null)

          return Registry.QOP_AUTH_CONF;

        return Registry.QOP_AUTH_INT;

      }

    return Registry.QOP_AUTH;

  }

  protected String getNegotiatedStrength()

  {

    if (inMac != null)

      {

        if (inCipher != null)

          return Registry.STRENGTH_HIGH;

        return Registry.STRENGTH_MEDIUM;

      }

    return Registry.STRENGTH_LOW;

  }

  protected String getNegotiatedRawSendSize()

  {

    return String.valueOf(rawSendSize);

  }

  protected String getReuse()

  {

    return Registry.REUSE_TRUE;

  }

  private byte[] sendIdentities() throws SaslException

  {

    if (Configuration.DEBUG)

      log.entering(this.getClass().getName(), "sendIdentities");

    // If necessary, prompt the client for the username and password

    getUsernameAndPassword();

    if (Configuration.DEBUG)

      {

        log.fine("Password: \"" + new String(password.getPassword()) + "\"");

        log.fine("Encoding U (username): \"" + U + "\"");

        log.fine("Encoding I (userid): \"" + authorizationID + "\"");

      }

    // if session re-use generate new 16-byte nonce

    if (sid.length != 0)

      {

        cn = new byte[16];

        getDefaultPRNG().nextBytes(cn);

      }

    else

      cn = new byte[0];

    final OutputBuffer frameOut = new OutputBuffer();

    try

      {

        frameOut.setText(U);

        frameOut.setText(authorizationID);

        frameOut.setEOS(sid); // session ID to re-use

        frameOut.setOS(cn); // client nonce

        frameOut.setEOS(channelBinding);

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

        throw new AuthenticationException("sendIdentities()", x);

      }

    final byte[] result = frameOut.encode();

    if (Configuration.DEBUG)

      {

        log.fine("C: " + Util.dumpString(result));

        log.fine("  U = " + U);

        log.fine("  I = " + authorizationID);

        log.fine("sid = " + new String(sid));

        log.fine(" cn = " + Util.dumpString(cn));

        log.fine("cCB = " + Util.dumpString(channelBinding));

        log.exiting(this.getClass().getName(), "sendIdentities");

      }

    return result;

  }

  private byte[] sendPublicKey(final byte[] input) throws SaslException

  {

    if (Configuration.DEBUG)

      {

        log.entering(this.getClass().getName(), "sendPublicKey");

        log.fine("S: " + Util.dumpString(input));

      }

    // Server sends [00], N, g, s, B, L

    // or [FF], sn, sCB

    final InputBuffer frameIn = new InputBuffer(input);

    final int ack;

    try

      {

        ack = (int) frameIn.getScalar(1);

        if (ack == 0x00) // new session

          {

            N = frameIn.getMPI();

            if (Configuration.DEBUG)

              log.fine("Got N (modulus): " + Util.dump(N));

            g = frameIn.getMPI();

            if (Configuration.DEBUG)

              log.fine("Got g (generator): " + Util.dump(g));

            s = frameIn.getOS();

            if (Configuration.DEBUG)

              log.fine("Got s (salt): " + Util.dumpString(s));

            B = frameIn.getMPI();

            if (Configuration.DEBUG)

              log.fine("Got B (server ephermeral public key): " + Util.dump(B));

            L = frameIn.getText();

            if (Configuration.DEBUG)

              log.fine("Got L (available options): \"" + L + "\"");

          }

        else if (ack == 0xFF) // session re-use

          {

            sn = frameIn.getOS();

            if (Configuration.DEBUG)

              log.fine("Got sn (server nonce): " + Util.dumpString(sn));

            sCB = frameIn.getEOS();

            if (Configuration.DEBUG)

              log.fine("Got sCB (server channel binding): " + Util.dumpString(sCB));

          }

        else // unexpected scalar

          throw new SaslException("sendPublicKey(): Invalid scalar (" + ack

                                  + ") in server's request");

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

        throw new SaslException("sendPublicKey()", x);

      }

    if (ack == 0x00)

      { // new session ---------------------------------------

        o = createO(L.toLowerCase()); // do this first to initialise the SRP hash

        final byte[] pBytes; // use ASCII encoding to inter-operate w/ non-java

        pBytes = password.getBytes();

        // ----------------------------------------------------------------------

        final HashMap mapA = new HashMap();

        mapA.put(SRP6KeyAgreement.HASH_FUNCTION, srp.getAlgorithm());

        mapA.put(SRP6KeyAgreement.USER_IDENTITY, U);

        mapA.put(SRP6KeyAgreement.USER_PASSWORD, pBytes);

        try

          {

            clientHandler.init(mapA);

            clientHandler.processMessage(null);

          }

        catch (KeyAgreementException x)

          {

            throw new SaslException("sendPublicKey()", x);

          }

        // -------------------------------------------------------------------

        try

          {

            OutgoingMessage out = new OutgoingMessage();

            out.writeMPI(N);

            out.writeMPI(g);

            out.writeMPI(new BigInteger(1, s));

            out.writeMPI(B);

            IncomingMessage in = new IncomingMessage(out.toByteArray());

            out = clientHandler.processMessage(in);

            in = new IncomingMessage(out.toByteArray());

            A = in.readMPI();

            K = clientHandler.getSharedSecret();

          }

        catch (KeyAgreementException x)

          {

            throw new SaslException("sendPublicKey()", x);

          }

        // -------------------------------------------------------------------

        if (Configuration.DEBUG)

          {

            log.fine("K: " + Util.dumpString(K));

            log.fine("Encoding A (client ephemeral public key): " + Util.dump(A));

          }

        try

          {

            M1 = srp.generateM1(N, g, U, s, A, B, K, authorizationID, L, cn,

                                channelBinding);

          }

        catch (UnsupportedEncodingException x)

          {

            throw new AuthenticationException("sendPublicKey()", x);

          }

        if (Configuration.DEBUG)

          {

            log.fine("Encoding o (client chosen options): \"" + o + "\"");

            log.fine("Encoding cIV (client IV): \"" + Util.dumpString(cIV) + "\"");

          }

        final OutputBuffer frameOut = new OutputBuffer();

        try

          {

            frameOut.setMPI(A);

            frameOut.setOS(M1);

            frameOut.setText(o);

            frameOut.setOS(cIV);

          }

        catch (IOException x)

          {

            if (x instanceof SaslException)

              throw (SaslException) x;

            throw new AuthenticationException("sendPublicKey()", x);

          }

        final byte[] result = frameOut.encode();

        if (Configuration.DEBUG)

          {

            log.fine("New session, or session re-use rejected...");

            log.fine("C: " + Util.dumpString(result));

            log.fine("  A = 0x" + A.toString(16));

            log.fine(" M1 = " + Util.dumpString(M1));

            log.fine("  o = " + o);

            log.fine("cIV = " + Util.dumpString(cIV));

            log.exiting(this.getClass().getName(), "sendPublicKey");

          }

        return result;

      }

    else // session re-use accepted -------------------------------------------

      {

        setupSecurityServices(true);

        if (Configuration.DEBUG)

          {

            log.fine("Session re-use accepted...");

            log.exiting(this.getClass().getName(), "sendPublicKey");

          }

        return null;

      }

  }

  private byte[] receiveEvidence(byte[] input) throws SaslException

  {

    if (Configuration.DEBUG)

      {

        log.entering(this.getClass().getName(), "receiveEvidence");

        log.fine("S: " + Util.dumpString(input));

      }

    // Server send M2, sIV, sCB, sid, ttl

    final InputBuffer frameIn = new InputBuffer(input);

    try

      {

        M2 = frameIn.getOS();