summaryrefslogtreecommitdiff
path: root/app/src/main/java/se/leap/bitmaskclient/LeapSRPSession.java
blob: a953a710625555f747e6c3be16642f0e1c538458 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
/**
 * 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 {
	
	private static String token = "";
	
	final public static String SALT = "salt";
	final public static String M1 = "M1";
	final public static String M2 = "M2";
	final public static String TOKEN = "token";
	final public static String AUTHORIZATION_HEADER= "Authorization";
    	final public static String TAG= "Leap SRP session class tag";
	
	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)
	{
		this(username, password, 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, byte[] abytes) {
	    
	    params = new SRPParameters(new BigInteger(ConfigHelper.NG_1024, 16).toByteArray(), ConfigHelper.G.toByteArray(), BigInteger.ZERO.toByteArray(), "SHA-256");
		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;
	}

    public byte[] calculateNewSalt() {
	try {
	    BigInteger salt = new BigInteger(64, SecureRandom.getInstance("SHA1PRNG"));
	    return ConfigHelper.trim(salt.toByteArray());
	} catch(NoSuchAlgorithmException e) {
	    e.printStackTrace();
	}
	return null;
    }
	/**
	 * Calculates the parameter V of the SRP-6a algorithm.
	 * @return the value of V
	 */
    public BigInteger calculateV(String username, String password, byte[] salt) {
		byte[] x_bytes = calculatePasswordHash(username, password, ConfigHelper.trim(salt));
		x = new BigInteger(1, x_bytes);
		BigInteger v = 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) {
		// Calculate x = H(s | H(U | ':' | password))
		byte[] M1 = null;
		if(new BigInteger(1, Bbytes).mod(new BigInteger(1, N_bytes)) != BigInteger.ZERO) {
		    this.v = calculateV(username, password, salt_bytes);
			// 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)
			MessageDigest sessionDigest = newDigest();
			K = ConfigHelper.trim(sessionDigest.digest(S_bytes));

			// clientHash = H(N) xor H(g) | H(U) | A | B | K
			clientHash.update(K);

			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);
		String k_string = "bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0";
		BigInteger k = new BigInteger(k_string, 16);
		BigInteger B_minus_v = B.subtract(k.multiply(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;
	}
	
	protected static void setToken(String token) {
		LeapSRPSession.token = token;
	}
	
	protected static String getToken() {
		return token;
	}

	/**
	 * @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;
	}

    public byte[] getK() {
	return K;
    }
}