/*
* JBoss, Home of Professional Open Source.
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.security.srp;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import org.jboss.crypto.CryptoUtil;
import org.jboss.logging.Logger;
/** The client side logic to the SRP protocol. The class is intended to be used
* with a SRPServerSession object via the SRPServerInterface. The SRP algorithm
* using these classes consists of:
*
* 1. Get server, SRPServerInterface server = (SRPServerInterface) Naming.lookup(...);
* 2. Get SRP parameters, SRPParameters params = server.getSRPParameters(username);
* 3. Create a client session, SRPClientSession client = new SRPClientSession(username,
* password, params);
* 4. Exchange public keys, byte[] A = client.exponential();
* byte[] B = server.init(username, A);
* 5. Exchange challenges, byte[] M1 = client.response(B);
* byte[] M2 = server.verify(username, M1);
* 6. Verify the server response, if( client.verify(M2) == false )
* throw new SecurityException("Failed to validate server reply");
* 7. Validation complete
*
* Note that these steps are stateful. They must be performed in order and a
* step cannot be repeated to update the session state.
*
* This product uses the 'Secure Remote Password' cryptographic
* authentication system developed by Tom Wu (tjw@CS.Stanford.EDU).
*
* @author Scott.Stark@jboss.org
* @version $Revision: 81038 $
*/
public class SRPClientSession
{
private static Logger log = Logger.getLogger(SRPClientSession.class);
private SRPParameters params;
private BigInteger N;
private BigInteger g;
private BigInteger x;
private BigInteger v;
private byte[] s;
private BigInteger a;
private BigInteger A;
private byte[] K;
/** The M1 = H(H(N) xor H(g) | H(U) | s | A | B | K) hash */
private MessageDigest clientHash;
/** The M2 = H(A | M | K) hash */
private MessageDigest serverHash;
private static int A_LEN = 64;
/** Creates a new SRP server session object from the username, password
verifier,
@param username, the user ID
@param password, the user clear text password
@param params, the SRP parameters for the session
*/
public SRPClientSession(String username, char[] password, SRPParameters params)
{
this(username, password, params, null);
}
/** Creates a new SRP server session object from the username, password
verifier,
@param username, the user ID
@param password, the user clear text password
@param params, the SRP parameters for the session
@param abytes, the random exponent used in the A public key. This must be
8 bytes in length.
*/
public SRPClientSession(String username, char[] password, SRPParameters params,
byte[] abytes)
{
try
{
// Initialize the secure random number and message digests
CryptoUtil.init();
}
catch(NoSuchAlgorithmException e)
{
}
this.params = params;
this.g = new BigInteger(1, params.g);
this.N = new BigInteger(1, params.N);
if( abytes != null )
{
if( 8*abytes.length != A_LEN )
throw new IllegalArgumentException("The abytes param must be "
+(A_LEN/8)+" in length, abytes.length="+abytes.length);
this.a = new BigInteger(abytes);
}
if( log.isTraceEnabled() )
log.trace("g: "+CryptoUtil.tob64(params.g));
// Calculate x = H(s | H(U | ':' | password))
byte[] xb = CryptoUtil.calculatePasswordHash(username, password, params.s);
if( log.isTraceEnabled() )
log.trace("x: "+CryptoUtil.tob64(xb));
this.x = new BigInteger(1, xb);
this.v = g.modPow(x, N); // g^x % N
if( log.isTraceEnabled() )
log.trace("v: "+CryptoUtil.tob64(v.toByteArray()));
serverHash = CryptoUtil.newDigest();
clientHash = CryptoUtil.newDigest();
// H(N)
byte[] hn = CryptoUtil.newDigest().digest(params.N);
if( log.isTraceEnabled() )
log.trace("H(N): "+CryptoUtil.tob64(hn));
// H(g)
byte[] hg = CryptoUtil.newDigest().digest(params.g);
if( log.isTraceEnabled() )
log.trace("H(g): "+CryptoUtil.tob64(hg));
// clientHash = H(N) xor H(g)
byte[] hxg = CryptoUtil.xor(hn, hg, 20);
if( log.isTraceEnabled() )
log.trace("H(N) xor H(g): "+CryptoUtil.tob64(hxg));
clientHash.update(hxg);
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(clientHash);
log.trace("H[H(N) xor H(g)]: "+CryptoUtil.tob64(tmp.digest()));
}
// clientHash = H(N) xor H(g) | H(U)
clientHash.update(CryptoUtil.newDigest().digest(username.getBytes()));
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(clientHash);
log.trace("H[H(N) xor H(g) | H(U)]: "+CryptoUtil.tob64(tmp.digest()));
}
// clientHash = H(N) xor H(g) | H(U) | s
clientHash.update(params.s);
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(clientHash);
log.trace("H[H(N) xor H(g) | H(U) | s]: "+CryptoUtil.tob64(tmp.digest()));
}
K = null;
}
/**
* @returns The exponential residue (parameter A) to be sent to the server.
*/
public byte[] exponential()
{
byte[] Abytes = null;
if(A == null)
{
/* If the random component of A has not been specified use a random
number */
if( a == null )
{
BigInteger one = BigInteger.ONE;
do
{
a = new BigInteger(A_LEN, CryptoUtil.getPRNG());
} while(a.compareTo(one) <= 0);
}
A = g.modPow(a, N);
Abytes = CryptoUtil.trim(A.toByteArray());
// clientHash = H(N) xor H(g) | H(U) | A
clientHash.update(Abytes);
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(clientHash);
log.trace("H[H(N) xor H(g) | H(U) | s | A]: "+CryptoUtil.tob64(tmp.digest()));
}
// serverHash = A
serverHash.update(Abytes);
}
return Abytes;
}
/**
@returns M1 = H(H(N) xor H(g) | H(U) | s | A | B | K)
@exception NoSuchAlgorithmException thrown if the session key
MessageDigest algorithm cannot be found.
*/
public byte[] response(byte[] Bbytes) throws NoSuchAlgorithmException
{
// clientHash = H(N) xor H(g) | H(U) | s | A | B
clientHash.update(Bbytes);
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(clientHash);
log.trace("H[H(N) xor H(g) | H(U) | s | A | B]: "+CryptoUtil.tob64(tmp.digest()));
}
// Calculate u as the first 32 bits of H(B)
byte[] hB = CryptoUtil.newDigest().digest(Bbytes);
byte[] ub =
{hB[0], hB[1], hB[2], hB[3]};
// Calculate S = (B - g^x) ^ (a + u * x) % N
BigInteger B = new BigInteger(1, Bbytes);
if( log.isTraceEnabled() )
log.trace("B: "+CryptoUtil.tob64(B.toByteArray()));
if( B.compareTo(v) < 0 )
B = B.add(N);
if( log.isTraceEnabled() )
log.trace("B': "+CryptoUtil.tob64(B.toByteArray()));
if( log.isTraceEnabled() )
log.trace("v: "+CryptoUtil.tob64(v.toByteArray()));
BigInteger u = new BigInteger(1, ub);
if( log.isTraceEnabled() )
log.trace("u: "+CryptoUtil.tob64(u.toByteArray()));
BigInteger B_v = B.subtract(v);
if( log.isTraceEnabled() )
log.trace("B - v: "+CryptoUtil.tob64(B_v.toByteArray()));
BigInteger a_ux = a.add(u.multiply(x));
if( log.isTraceEnabled() )
log.trace("a + u * x: "+CryptoUtil.tob64(a_ux.toByteArray()));
BigInteger S = B_v.modPow(a_ux, N);
if( log.isTraceEnabled() )
log.trace("S: "+CryptoUtil.tob64(S.toByteArray()));
// K = SessionHash(S)
MessageDigest sessionDigest = MessageDigest.getInstance(params.hashAlgorithm);
K = sessionDigest.digest(S.toByteArray());
if( log.isTraceEnabled() )
log.trace("K: "+CryptoUtil.tob64(K));
// clientHash = H(N) xor H(g) | H(U) | A | B | K
clientHash.update(K);
byte[] M1 = clientHash.digest();
if( log.isTraceEnabled() )
log.trace("M1: H[H(N) xor H(g) | H(U) | s | A | B | K]: "+CryptoUtil.tob64(M1));
serverHash.update(M1);
serverHash.update(K);
if( log.isTraceEnabled() )
{
MessageDigest tmp = CryptoUtil.copy(serverHash);
log.trace("H[A | M1 | K]: "+CryptoUtil.tob64(tmp.digest()));
}
return M1;
}
/**
* @param M2 The server's response to the client's challenge
* @returns True if and only if the server's response was correct.
*/
public boolean verify(byte[] M2)
{
// M2 = H(A | M1 | K)
byte[] myM2 = serverHash.digest();
boolean valid = Arrays.equals(M2, myM2);
if( log.isTraceEnabled() )
{
log.trace("verify serverM2: "+CryptoUtil.tob64(M2));
log.trace("verify M2: "+CryptoUtil.tob64(myM2));
}
return valid;
}
/** Returns the negotiated session K, K = SHA_Interleave(S)
@return the private session K byte[]
@throws SecurityException - if the current thread does not have an
getSessionKey SRPPermission.
*/
public byte[] getSessionKey() throws SecurityException
{
SecurityManager sm = System.getSecurityManager();
if( sm != null )
{
SRPPermission p = new SRPPermission("getSessionKey");
sm.checkPermission(p);
}
return K;
}
}