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package se.leap.leapclient;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import org.jboss.security.Util;
import org.jboss.security.srp.SRPClientSession;
import org.jboss.security.srp.SRPParameters;
import org.jboss.security.srp.SRPPermission;
public class LeapSRPSession {
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;
/** 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 LeapSRPSession(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 LeapSRPSession(String username, char[] password, SRPParameters params,
byte[] abytes)
{
try
{
// Initialize the secure random number and message digests
Util.init();
}
catch(NoSuchAlgorithmException e)
{
}
this.params = params;
this.g = new BigInteger(1, params.g);
this.N = new BigInteger(1, params.N);
if( abytes != null )
{
A_LEN = 8*abytes.length;
/* TODO Why did they put this condition?
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);
}
// Calculate x = H(s | H(U | ':' | password))
byte[] xb = Util.calculatePasswordHash(username, password, params.s);
this.x = new BigInteger(1, xb);
this.v = g.modPow(x, N); // g^x % N
serverHash = Util.newDigest();
clientHash = Util.newDigest();
// H(N)
byte[] hn = Util.newDigest().digest(params.N);
// H(g)
byte[] hg = Util.newDigest().digest(params.g);
// clientHash = H(N) xor H(g)
byte[] hxg = Util.xor(hn, hg, 20);
clientHash.update(hxg);
// clientHash = H(N) xor H(g) | H(U)
clientHash.update(Util.newDigest().digest(username.getBytes()));
// clientHash = H(N) xor H(g) | H(U) | s
clientHash.update(params.s);
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, Util.getPRNG());
} while(a.compareTo(one) <= 0);
}
A = g.modPow(a, N);
Abytes = Util.trim(A.toByteArray());
// clientHash = H(N) xor H(g) | H(U) | A
clientHash.update(Abytes);
// serverHash = A
serverHash.update(Abytes);
}
return Abytes;
}
public byte[] response(byte[] Bbytes) throws NoSuchAlgorithmException {
// clientHash = H(N) xor H(g) | H(U) | s | A | B
clientHash.update(Bbytes);
/*
var B = new BigInteger(ephemeral, 16);
var Bstr = ephemeral;
// u = H(A,B)
var u = new BigInteger(SHA256(hex2a(Astr + Bstr)), 16);
// x = H(s, H(I:p))
var x = this.calcX(salt);
//S = (B - kg^x) ^ (a + ux)
var kgx = k.multiply(g.modPow(x, N));
var aux = a.add(u.multiply(x));
S = B.subtract(kgx).modPow(aux, N);
K = SHA256(hex2a(S.toString(16)));
*/
byte[] hA = Util.newDigest().digest(A.toByteArray());
MessageDigest u_digest = Util.newDigest();
u_digest.update(A.toByteArray());
u_digest.update(Bbytes);
clientHash.update(u_digest.digest());
byte[] ub = new BigInteger(clientHash.digest()).toByteArray();
// Calculate S = (B - g^x) ^ (a + u * x) % N
BigInteger B = new BigInteger(1, Bbytes);
if( B.compareTo(v) < 0 )
B = B.add(N);
BigInteger u = new BigInteger(1, ub);
BigInteger B_v = B.subtract(v);
BigInteger a_ux = a.add(u.multiply(x));
BigInteger S = B_v.modPow(a_ux, N);
// K = SessionHash(S)
MessageDigest sessionDigest = MessageDigest.getInstance(params.hashAlgorithm);
K = sessionDigest.digest(S.toByteArray());
// clientHash = H(N) xor H(g) | H(U) | A | B | K
clientHash.update(K);
byte[] M1 = clientHash.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);
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;
}
}
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