Source for gnu.javax.crypto.key.srp6.SRP6Host

   1: /* SRP6Host.java --
   2:    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2 of the License, or (at
   9: your option) any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: USA
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version.  */
  37: 
  38: 
  39: package gnu.javax.crypto.key.srp6;
  40: 
  41: import gnu.java.security.Registry;
  42: import gnu.java.security.hash.IMessageDigest;
  43: import gnu.java.security.util.Util;
  44: import gnu.javax.crypto.key.KeyAgreementException;
  45: import gnu.javax.crypto.key.IncomingMessage;
  46: import gnu.javax.crypto.key.OutgoingMessage;
  47: import gnu.javax.crypto.sasl.srp.SRP;
  48: import gnu.javax.crypto.sasl.srp.SRPAuthInfoProvider;
  49: import gnu.javax.crypto.sasl.srp.SRPRegistry;
  50: 
  51: import java.io.IOException;
  52: import java.math.BigInteger;
  53: import java.security.KeyPair;
  54: import java.security.SecureRandom;
  55: import java.util.HashMap;
  56: import java.util.Map;
  57: 
  58: /**
  59:  * The implementation of the Host in the SRP-6 key agreement protocol.
  60:  * <p>
  61:  * Reference:
  62:  * <ol>
  63:  * <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
  64:  * Thomas J. Wu.</li>
  65:  * </ol>
  66:  */
  67: public class SRP6Host
  68:     extends SRP6KeyAgreement
  69: {
  70:   /** The user's ephemeral key pair. */
  71:   private KeyPair hostKeyPair;
  72: 
  73:   /** The SRP password database. */
  74:   private SRPAuthInfoProvider passwordDB;
  75: 
  76:   // default 0-arguments constructor
  77: 
  78:   protected void engineInit(final Map attributes) throws KeyAgreementException
  79:   {
  80:     rnd = (SecureRandom) attributes.get(SOURCE_OF_RANDOMNESS);
  81:     N = (BigInteger) attributes.get(SHARED_MODULUS);
  82:     if (N == null)
  83:       throw new KeyAgreementException("missing shared modulus");
  84:     g = (BigInteger) attributes.get(GENERATOR);
  85:     if (g == null)
  86:       throw new KeyAgreementException("missing generator");
  87:     final String md = (String) attributes.get(HASH_FUNCTION);
  88:     if (md == null || md.trim().length() == 0)
  89:       throw new KeyAgreementException("missing hash function");
  90:     srp = SRP.instance(md);
  91:     passwordDB = (SRPAuthInfoProvider) attributes.get(HOST_PASSWORD_DB);
  92:     if (passwordDB == null)
  93:       throw new KeyAgreementException("missing SRP password database");
  94:   }
  95: 
  96:   protected OutgoingMessage engineProcessMessage(final IncomingMessage in)
  97:       throws KeyAgreementException
  98:   {
  99:     switch (step)
 100:       {
 101:       case 0:
 102:         return computeSharedSecret(in);
 103:       default:
 104:         throw new IllegalStateException("unexpected state");
 105:       }
 106:   }
 107: 
 108:   protected void engineReset()
 109:   {
 110:     hostKeyPair = null;
 111:     super.engineReset();
 112:   }
 113: 
 114:   private OutgoingMessage computeSharedSecret(final IncomingMessage in)
 115:       throws KeyAgreementException
 116:   {
 117:     final String I = in.readString();
 118:     final BigInteger A = in.readMPI();
 119:     // get s and v for user identified by I
 120:     // ----------------------------------------------------------------------
 121:     final Map credentials;
 122:     try
 123:       {
 124:         final Map userID = new HashMap();
 125:         userID.put(Registry.SASL_USERNAME, I);
 126:         userID.put(SRPRegistry.MD_NAME_FIELD, srp.getAlgorithm());
 127:         credentials = passwordDB.lookup(userID);
 128:       }
 129:     catch (IOException x)
 130:       {
 131:         throw new KeyAgreementException("computeSharedSecret()", x);
 132:       }
 133:     final BigInteger s = new BigInteger(
 134:         1,Util.fromBase64((String) credentials.get(SRPRegistry.SALT_FIELD)));
 135:     final BigInteger v = new BigInteger(
 136:         1, Util.fromBase64((String) credentials.get(SRPRegistry.USER_VERIFIER_FIELD)));
 137:     final SRPKeyPairGenerator kpg = new SRPKeyPairGenerator();
 138:     final Map attributes = new HashMap();
 139:     if (rnd != null)
 140:       attributes.put(SRPKeyPairGenerator.SOURCE_OF_RANDOMNESS, rnd);
 141:     attributes.put(SRPKeyPairGenerator.SHARED_MODULUS, N);
 142:     attributes.put(SRPKeyPairGenerator.GENERATOR, g);
 143:     attributes.put(SRPKeyPairGenerator.USER_VERIFIER, v);
 144:     kpg.setup(attributes);
 145:     hostKeyPair = kpg.generate();
 146:     final BigInteger B = ((SRPPublicKey) hostKeyPair.getPublic()).getY();
 147:     final BigInteger u = uValue(A, B); // u = H(A | B)
 148:     // compute S = (Av^u) ^ b
 149:     final BigInteger b = ((SRPPrivateKey) hostKeyPair.getPrivate()).getX();
 150:     final BigInteger S = A.multiply(v.modPow(u, N)).modPow(b, N);
 151:     final byte[] sBytes = Util.trim(S);
 152:     final IMessageDigest hash = srp.newDigest();
 153:     hash.update(sBytes, 0, sBytes.length);
 154:     K = new BigInteger(1, hash.digest());
 155:     final OutgoingMessage result = new OutgoingMessage();
 156:     result.writeMPI(s);
 157:     result.writeMPI(B);
 158:     complete = true;
 159:     return result;
 160:   }
 161: }