Merge branch 'release-0.2.1'0.2.1

1 files changed, 326 insertions, 0 deletions

diff --git a/src/se/leap/bitmaskclient/LeapSRPSession.java b/src/se/leap/bitmaskclient/LeapSRPSession.java
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+++ b/src/se/leap/bitmaskclient/LeapSRPSession.java
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+/**
+ * Copyright (c) 2013 LEAP Encryption Access Project and contributers
+ * 
+ * This program 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+ package se.leap.bitmaskclient;
+
+import java.io.UnsupportedEncodingException;
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.Arrays;
+
+import org.jboss.security.srp.SRPParameters;
+
+/**
+ * Implements all SRP algorithm logic.
+ * 
+ * It's derived from JBoss implementation, with adjustments to make it work with LEAP platform.
+ * 
+ * @author parmegv
+ *
+ */
+public class LeapSRPSession {
+	
+	final public static String SALT = "salt";
+	final public static String M1 = "M1";
+	final public static String M2 = "M2";
+
+	private SRPParameters params;
+	private String username;
+	private String password;
+	private BigInteger N;
+	private byte[] N_bytes;
+	private BigInteger g;
+	private BigInteger x;
+	private BigInteger v;
+	private BigInteger a;
+	private BigInteger A;
+	private byte[] K;
+	private SecureRandom pseudoRng;
+	/** 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, String 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
+	 */
+	public LeapSRPSession(String username, String password, SRPParameters params,
+			byte[] abytes) {
+		this.params = params;
+		this.g = new BigInteger(1, params.g);
+		N_bytes = ConfigHelper.trim(params.N);
+		this.N = new BigInteger(1, N_bytes);
+		this.username = username;
+		this.password = password;
+		
+		try {
+			pseudoRng = SecureRandom.getInstance("SHA1PRNG");
+		} catch (NoSuchAlgorithmException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		}
+		
+		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);
+		}
+		else
+			A_LEN = 64;
+
+		serverHash = newDigest();
+		clientHash = newDigest();
+	}
+
+	/**
+	 * 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, String password, byte[] salt)
+	{
+		//password = password.replaceAll("\\\\", "\\\\\\\\");
+		// Calculate x = H(s | H(U | ':' | password))
+		MessageDigest x_digest = newDigest();
+		// Try to convert the username to a byte[] using ISO-8859-1
+		byte[] user = null;
+		byte[] password_bytes = null;
+		byte[] colon = {};
+		String encoding = "ISO-8859-1";
+		try {
+			user = ConfigHelper.trim(username.getBytes(encoding));
+			colon = ConfigHelper.trim(":".getBytes(encoding));
+			password_bytes = ConfigHelper.trim(password.getBytes(encoding));
+		}
+		catch(UnsupportedEncodingException e) {
+			// Use the default platform encoding
+			user = ConfigHelper.trim(username.getBytes());
+			colon = ConfigHelper.trim(":".getBytes());
+			password_bytes = ConfigHelper.trim(password.getBytes());
+		}
+		
+		// Build the hash
+		x_digest.update(user);
+		x_digest.update(colon);
+		x_digest.update(password_bytes);
+		byte[] h = x_digest.digest();
+		
+		x_digest.reset();
+		x_digest.update(salt);
+		x_digest.update(h);
+		byte[] x_digest_bytes = 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);
+		BigInteger v = k.multiply(g.modPow(x, N));  // g^x % N
+		return v;
+	}
+
+	/**
+	 * Calculates the trimmed xor from two BigInteger numbers
+	 * @param b1 the positive source to build first BigInteger
+	 * @param b2 the positive source to build second BigInteger
+	 * @param length 
+	 * @return
+	 */
+	public byte[] xor(byte[] b1, byte[] b2)
+	{
+		//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 ConfigHelper.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, pseudoRng);
+				} while(a.compareTo(one) <= 0);
+			}
+			A = g.modPow(a, N);
+			Abytes = ConfigHelper.trim(A.toByteArray());
+		}
+		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.
+	 * It uses a predefined k.
+	 * @param salt_bytes
+	 * @param Bbytes the parameter received from the server, in bytes
+	 * @return the parameter M1
+	 * @throws NoSuchAlgorithmException
+	 */
+	public byte[] response(byte[] salt_bytes, byte[] Bbytes) throws NoSuchAlgorithmException {
+		// Calculate x = H(s | H(U | ':' | password))
+		byte[] xb = calculatePasswordHash(username, password, ConfigHelper.trim(salt_bytes));
+		this.x = new BigInteger(1, xb);
+
+		// Calculate v = kg^x mod N
+		String k_string = "bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0";
+		this.v = calculateV(k_string);
+
+		// 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);
+		clientHash.update(xor_digest);
+		
+		// clientHash = H(N) xor H(g) | H(U)
+		byte[] username_digest = newDigest().digest(ConfigHelper.trim(username.getBytes()));
+		username_digest = ConfigHelper.trim(username_digest);
+		clientHash.update(username_digest);
+		
+		// clientHash = H(N) xor H(g) | H(U) | s
+		clientHash.update(ConfigHelper.trim(salt_bytes));
+		
+		K = null;
+
+		// clientHash = H(N) xor H(g) | H(U) | A
+		byte[] Abytes = ConfigHelper.trim(A.toByteArray());
+		clientHash.update(Abytes);
+		
+		// clientHash = H(N) xor H(g) | H(U) | s | A | B
+		Bbytes = ConfigHelper.trim(Bbytes);
+		clientHash.update(Bbytes);
+		
+		// Calculate S = (B - kg^x) ^ (a + u * x) % N
+		BigInteger S = calculateS(Bbytes);
+		byte[] S_bytes = ConfigHelper.trim(S.toByteArray());
+
+		// K = SessionHash(S)
+		String hash_algorithm = params.hashAlgorithm;
+		MessageDigest sessionDigest = MessageDigest.getInstance(hash_algorithm);
+		K = ConfigHelper.trim(sessionDigest.digest(S_bytes));
+		
+		// clientHash = H(N) xor H(g) | H(U) | A | B | K
+		clientHash.update(K);
+		
+		byte[] M1 = ConfigHelper.trim(clientHash.digest());
+		
+		// serverHash = Astr + M + K
+		serverHash.update(Abytes);
+		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 = ConfigHelper.trim(A.toByteArray());
+		Bbytes = ConfigHelper.trim(Bbytes);
+		byte[] u_bytes = getU(Abytes, Bbytes);
+		
+		BigInteger B = new BigInteger(1, Bbytes);
+		BigInteger u = new BigInteger(1, u_bytes);
+		
+		BigInteger B_minus_v = B.subtract(v);
+		BigInteger a_ux = a.add(u.multiply(x));
+		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(ConfigHelper.trim(Abytes));
+		u_digest.update(ConfigHelper.trim(Bbytes));
+		byte[] u_digest_bytes = u_digest.digest();
+		return ConfigHelper.trim(new BigInteger(1, u_digest_bytes).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)
+		M2 = ConfigHelper.trim(M2);
+		byte[] myM2 = ConfigHelper.trim(serverHash.digest());
+		boolean valid = Arrays.equals(M2, myM2);
+		return valid;
+	}
+
+	/**
+	 * @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;
+	}
+}