1 files changed, 315 insertions, 0 deletions
diff --git a/src/se/leap/leapclient/LeapSRPSession.java b/src/se/leap/leapclient/LeapSRPSession.java
new file mode 100644
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+++ b/src/se/leap/leapclient/LeapSRPSession.java
@@ -0,0 +1,315 @@
+package se.leap.leapclient;
+
+import java.io.UnsupportedEncodingException;
+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 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);
+		byte[] N_bytes = Util.trim(params.N);
+		this.N = new BigInteger(1, N_bytes);
+
+		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[] salt_bytes = Util.trim(params.s);
+		byte[] xb = calculatePasswordHash(username, password, salt_bytes);
+		this.x = new BigInteger(1, xb);
+
+		// Calculate v = kg^x mod N
+		String k_string = "bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0";
+		this.v = calculateV(k_string);
+		//String v_string = v.toString(16);
+
+		serverHash = newDigest();
+		clientHash = newDigest();
+
+		// H(N)
+		byte[] digest_of_n = newDigest().digest(N_bytes);
+		
+		// H(g)
+		byte[] digest_of_g = newDigest().digest(params.g);
+		
+		// clientHash = H(N) xor H(g)
+		byte[] xor_digest = xor(digest_of_n, digest_of_g, digest_of_g.length);
+		//String hxg_string = new BigInteger(1, xor_digest).toString(16);
+		clientHash.update(xor_digest);
+		
+		// clientHash = H(N) xor H(g) | H(U)
+		byte[] username_digest = newDigest().digest(Util.trim(username.getBytes()));
+		username_digest = Util.trim(username_digest);
+		//String username_digest_string = new BigInteger(1, username_digest).toString(16);
+		clientHash.update(username_digest);
+		
+		// clientHash = H(N) xor H(g) | H(U) | s
+		//String salt_string = new BigInteger(1, salt_bytes).toString(16);
+		clientHash.update(salt_bytes);
+		
+		K = null;
+	}
+
+	/**
+	 * Calculates the parameter x of the SRP-6a algorithm.
+	 * @param username
+	 * @param password
+	 * @param salt the salt of the user
+	 * @return x
+	 */
+	public byte[] calculatePasswordHash(String username, char[] password, byte[] salt)
+	{
+		// Calculate x = H(s | H(U | ':' | password))
+		MessageDigest x_digest = newDigest();
+		
+		// Try to convert the username to a byte[] using UTF-8
+		byte[] user = null;
+		byte[] colon = {};
+		try {
+			user = Util.trim(username.getBytes("UTF-8"));
+			colon = Util.trim(":".getBytes("UTF-8"));
+		}
+		catch(UnsupportedEncodingException e) {
+			// Use the default platform encoding
+			user = Util.trim(username.getBytes());
+			colon = Util.trim(":".getBytes());
+		}
+
+		byte[] passBytes = new byte[2*password.length];
+		int passBytesLength = 0;
+		for(int p = 0; p < password.length; p++) {
+			int c = (password[p] & 0x00FFFF);
+			// The low byte of the char
+			byte b0 = (byte) (c & 0x0000FF);
+			// The high byte of the char
+			byte b1 = (byte) ((c & 0x00FF00) >> 8);
+			passBytes[passBytesLength ++] = b0;
+			// Only encode the high byte if c is a multi-byte char
+			if( c > 255 )
+				passBytes[passBytesLength ++] = b1;
+		}
+	
+		// Build the hash
+		x_digest.update(user);
+		x_digest.update(colon);
+		x_digest.update(passBytes, 0, passBytesLength);
+		byte[] h = x_digest.digest();
+		//h = Util.trim(h);
+		
+		x_digest.reset();
+		x_digest.update(salt);
+		x_digest.update(h);
+		byte[] x_digest_bytes = Util.trim(x_digest.digest());
+
+		return x_digest_bytes;
+	}
+
+	/**
+	 * Calculates the parameter V of the SRP-6a algorithm.
+	 * @param k_string constant k predefined by the SRP server implementation.
+	 * @return the value of V
+	 */
+	private BigInteger calculateV(String k_string) {
+		BigInteger k = new BigInteger(k_string, 16);
+		return k.multiply(g.modPow(x, N));  // g^x % N
+	}
+
+	public byte[] xor(byte[] b1, byte[] b2, int length)
+	{
+		//TODO Check if length matters in the order, when b2 is smaller than b1 or viceversa
+		byte[] xor_digest = new BigInteger(1, b1).xor(new BigInteger(1, b2)).toByteArray();
+		return Util.trim(xor_digest);
+	}
+
+	/**
+	 * @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());
+			//String Abytes_string = new BigInteger(1, Abytes).toString(16);
+
+			// clientHash = H(N) xor H(g) | H(U) | A
+			clientHash.update(Abytes);
+			
+			// serverHash = A
+			serverHash.update(Abytes);
+		}
+		return Abytes;
+	}
+
+	/**
+	 * Calculates the parameter M1, to be sent to the SRP server.
+	 * It also updates hashes of client and server for further calculations in other methods.
+	 * @param Bbytes the parameter received from the server, in bytes
+	 * @return the parameter M1
+	 * @throws NoSuchAlgorithmException
+	 */
+	public byte[] response(byte[] Bbytes) throws NoSuchAlgorithmException {
+		// clientHash = H(N) xor H(g) | H(U) | s | A | B
+		Bbytes = Util.trim(Bbytes);
+		//String Bbytes_string = new BigInteger(1, Bbytes).toString(16);
+		clientHash.update(Bbytes);
+		
+		// Calculate S = (B - kg^x) ^ (a + u * x) % N
+		BigInteger S = calculateS(Bbytes);
+		byte[] S_bytes = Util.trim(S.toByteArray());
+		//String S_bytes_string = new BigInteger(1, S_bytes).toString(16);
+
+		// K = SessionHash(S)
+		String hash_algorithm = params.hashAlgorithm;
+		MessageDigest sessionDigest = MessageDigest.getInstance(hash_algorithm);
+		K = sessionDigest.digest(S_bytes);
+		//K = Util.trim(K);
+		//String K_bytes_string = new BigInteger(1, K).toString(16);
+		
+		// clientHash = H(N) xor H(g) | H(U) | A | B | K
+		clientHash.update(K);
+		byte[] M1 = clientHash.digest();
+		
+		// serverHash = Astr + M + K
+		serverHash.update(M1);
+		serverHash.update(K);
+		return M1;
+	}
+
+	/**
+	 * It calculates the parameter S used by response() to obtain session hash K.
+	 * @param Bbytes the parameter received from the server, in bytes
+	 * @return the parameter S
+	 */
+	private BigInteger calculateS(byte[] Bbytes) {
+		byte[] Abytes = Util.trim(A.toByteArray());
+		byte[] u_bytes = getU(Abytes, Bbytes);
+		//ub = Util.trim(ub);
+		
+		BigInteger B = new BigInteger(1, Bbytes);
+		BigInteger u = new BigInteger(1, u_bytes);
+		//String u_string = u.toString(16);
+		
+		BigInteger B_minus_v = B.subtract(v);
+		BigInteger a_ux = a.add(u.multiply(x));
+		//String a_ux_string = a_ux.toString(16);
+		BigInteger S = B_minus_v.modPow(a_ux, N);
+
+		return S;
+	}
+
+	/**
+	 * It calculates the parameter u used by calculateS to obtain S.
+	 * @param Abytes the exponential residue sent to the server
+	 * @param Bbytes the parameter received from the server, in bytes
+	 * @return
+	 */
+	public byte[] getU(byte[] Abytes, byte[] Bbytes) {
+		MessageDigest u_digest = newDigest();
+		u_digest.update(Abytes);
+		u_digest.update(Bbytes);
+		return new BigInteger(1, u_digest.digest()).toByteArray();
+	}
+
+	/**
+	 * @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
+	{
+		return K;
+	}
+
+	
+	/**
+	 * @return a new SHA-256 digest.
+	 */
+	public MessageDigest newDigest()
+	{
+		MessageDigest md = null;
+		try {
+			md = MessageDigest.getInstance("SHA-256");
+		} catch (NoSuchAlgorithmException e) {
+			e.printStackTrace();
+		}
+		return md;
+	}
+}