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/* SRPServer.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.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.IllegalMechanismStateException;

import gnu.javax.crypto.sasl.InputBuffer;

import gnu.javax.crypto.sasl.IntegrityException;

import gnu.javax.crypto.sasl.OutputBuffer;

import gnu.javax.crypto.sasl.ServerMechanism;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.math.BigInteger;

import java.util.Arrays;

import java.util.HashMap;

import java.util.StringTokenizer;

import java.util.logging.Logger;

import javax.security.sasl.AuthenticationException;

import javax.security.sasl.SaslException;

import javax.security.sasl.SaslServer;

/**

 * The SASL-SRP server-side mechanism.

 */

public class SRPServer

    extends ServerMechanism

    implements SaslServer

{

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

  private String U = null; // client's username

  private BigInteger N, g, A, B;

  private byte[] s; // salt

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

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

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

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

  private int ttl = 360; // session time-to-live in seconds

  private byte[] cCB; // peer's channel binding'

  private String mandatory; // List of available options

  private String L = null;

  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 serverHandler =

      KeyAgreementFactory.getPartyBInstance(Registry.SRP_SASL_KA);

  /** Our default source of randomness. */

  private PRNG prng = null;

  public SRPServer()

  {

    super(Registry.SASL_SRP_MECHANISM);

  }

  protected void initMechanism() throws SaslException

  {

    // TODO:

    // we must have a means to map a given username to a preferred

    // SRP hash algorithm; otherwise we end up using _always_ SHA.

    // for the time being get it from the mechanism properties map

    // and apply it for all users.

    final String mda = (String) properties.get(SRPRegistry.SRP_HASH);

    srp = SRP.instance(mda == null ? SRPRegistry.SRP_DEFAULT_DIGEST_NAME : mda);

  }

  protected void resetMechanism() throws SaslException

  {

    s = null;

    A = B = null;

    K = null;

    inMac = outMac = null;

    inCipher = outCipher = null;

    sid = null;

  }

  public byte[] evaluateResponse(final byte[] response) throws SaslException

  {

    switch (state)

      {

      case 0:

        if (response == null)

          return null;

        state++;

        return sendProtocolElements(response);

      case 1:

        if (! complete)

          {

            state++;

            return sendEvidence(response);

          }

      // else fall through

      default:

        throw new IllegalMechanismStateException("evaluateResponse()");

      }

  }

  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");

    if (Configuration.DEBUG)

      log.fine("Incoming buffer (before security): "

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

    // 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=" + String.valueOf(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[payloadLength];

                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.fine("Incoming buffer (after security): " + Util.dumpString(result));

        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");

    if (Configuration.DEBUG)

      {

        log.fine("Outgoing buffer (before security) (hex): "

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

        log.fine("Outgoing buffer (before security) (str): \""

                 + new String(outgoing, offset, len) + "\"");

      }

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

    // services are active.

    byte[] result;

    try

      {

        final ByteArrayOutputStream out = new ByteArrayOutputStream();

        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 ciphertext 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[] sendProtocolElements(final byte[] input) throws SaslException

  {

    if (Configuration.DEBUG)

      {

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

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

      }

    // Client send U, I, sid, cn

    final InputBuffer frameIn = new InputBuffer(input);

    try

      {

        U = frameIn.getText(); // Extract username

        if (Configuration.DEBUG)

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

        authorizationID = frameIn.getText(); // Extract authorisation ID

        if (Configuration.DEBUG)

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

        sid = frameIn.getEOS();

        if (Configuration.DEBUG)

          log.fine("Got sid (session ID): " + new String(sid));

        cn = frameIn.getOS();

        if (Configuration.DEBUG)

          log.fine("Got cn (client nonce): " + Util.dumpString(cn));

        cCB = frameIn.getEOS();

        if (Configuration.DEBUG)

          log.fine("Got cCB (client channel binding): " + Util.dumpString(cCB));

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

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

      }

    // do/can we re-use?

    if (ServerStore.instance().isAlive(sid))

      {

        final SecurityContext ctx = ServerStore.instance().restoreSession(sid);

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

        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();

        if (sn == null || sn.length != 16)

          sn = new byte[16];

        getDefaultPRNG().nextBytes(sn);

        setupSecurityServices(false);

        final OutputBuffer frameOut = new OutputBuffer();

        try

          {

            frameOut.setScalar(1, 0xFF);

            frameOut.setOS(sn);

            frameOut.setEOS(channelBinding);

          }

        catch (IOException x)

          {

            if (x instanceof SaslException)

              throw (SaslException) x;

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

          }

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

        if (Configuration.DEBUG)

          {

            log.fine("Old session...");

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

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

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

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

          }

        return result;

      }

    else

      { // new session

        authenticator.activate(properties);

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

        final HashMap mapB = new HashMap();

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

        mapB.put(SRP6KeyAgreement.HOST_PASSWORD_DB, authenticator);

        try

          {

            serverHandler.init(mapB);

            OutgoingMessage out = new OutgoingMessage();

            out.writeString(U);

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

            out = serverHandler.processMessage(in);

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

            N = in.readMPI();

            g = in.readMPI();

            s = in.readMPI().toByteArray();

            B = in.readMPI();

          }

        catch (KeyAgreementException x)

          {

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

          }

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

        if (Configuration.DEBUG)

          {

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

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

            log.fine("Encoding s (client's salt): " + Util.dumpString(s));

            log.fine("Encoding B (server ephemeral public key): " + Util.dump(B));

          }

        // The server creates an options list (L), which consists of a

        // comma-separated list of option strings that specify the security

        // service options the server supports.

        L = createL();

        if (Configuration.DEBUG)

          {

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

            log.fine("Encoding sIV (server IV): " + Util.dumpString(sIV));

          }

        final OutputBuffer frameOut = new OutputBuffer();

        try

          {

            frameOut.setScalar(1, 0x00);

            frameOut.setMPI(N);

            frameOut.setMPI(g);

            frameOut.setOS(s);

            frameOut.setMPI(B);

            frameOut.setText(L);

          }

        catch (IOException x)

          {

            if (x instanceof SaslException)

              throw (SaslException) x;

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

          }

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

        if (Configuration.DEBUG)

          {

            log.fine("New session...");

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

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

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

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

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

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

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

          }

        return result;

      }

  }

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

  {

    if (Configuration.DEBUG)

      {

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

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

      }

    // Client send A, M1, o, cIV

    final InputBuffer frameIn = new InputBuffer(input);

    final byte[] M1;

    try

      {

        A = frameIn.getMPI(); // Extract client's ephemeral public key

        if (Configuration.DEBUG)

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

        M1 = frameIn.getOS(); // Extract evidence

        if (Configuration.DEBUG)

          log.fine("Got M1 (client evidence): " + Util.dumpString(M1));

        o = frameIn.getText(); // Extract client's options list

        if (Configuration.DEBUG)

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

        cIV = frameIn.getOS(); // Extract client's IV

        if (Configuration.DEBUG)

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

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

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

      }

    // Parse client's options and set security layer variables

    parseO(o);

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

    try

      {

        final OutgoingMessage out = new OutgoingMessage();

        out.writeMPI(A);

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

        serverHandler.processMessage(in);

        K = serverHandler.getSharedSecret();

      }

    catch (KeyAgreementException x)

      {

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

      }

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

    if (Configuration.DEBUG)

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

    final byte[] expected;

    try

      {

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

                                  cCB);

      }

    catch (UnsupportedEncodingException x)

      {

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

      }

    // Verify client evidence

    if (! Arrays.equals(M1, expected))

      throw new AuthenticationException("M1 mismatch");

    setupSecurityServices(true);

    final byte[] M2;

    try

      {

        M2 = srp.generateM2(A, M1, K, U, authorizationID, o, sid, ttl, cIV,

                            sIV, channelBinding);

      }

    catch (UnsupportedEncodingException x)

      {

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

      }

    final OutputBuffer frameOut = new OutputBuffer();

    try

      {

        frameOut.setOS(M2);

        frameOut.setOS(sIV);

        frameOut.setEOS(sid);

        frameOut.setScalar(4, ttl);

        frameOut.setEOS(channelBinding);

      }

    catch (IOException x)

      {

        if (x instanceof SaslException)

          throw (SaslException) x;

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

      }

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

    if (Configuration.DEBUG)

      {

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

        log.fine("  M2 = " + Util.dumpString(M2));

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

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

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

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

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

      }

    return result;

  }

  private String createL()

  {

    if (Configuration.DEBUG)

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

    String s = (String) properties.get(SRPRegistry.SRP_MANDATORY);

    if (s == null)

      s = SRPRegistry.DEFAULT_MANDATORY;

    if (! SRPRegistry.MANDATORY_NONE.equals(s)

        && ! SRPRegistry.OPTION_REPLAY_DETECTION.equals(s)

        && ! SRPRegistry.OPTION_INTEGRITY.equals(s)