1 files changed, 361 insertions, 0 deletions
diff --git a/app/src/main/java/se/leap/bitmaskclient/providersetup/models/LeapSRPSession.java b/app/src/main/java/se/leap/bitmaskclient/providersetup/models/LeapSRPSession.java
new file mode 100644
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+++ b/app/src/main/java/se/leap/bitmaskclient/providersetup/models/LeapSRPSession.java
@@ -0,0 +1,361 @@
+/**
+ * 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.providersetup.models;
+
+
+import org.jboss.security.srp.SRPParameters;
+
+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 se.leap.bitmaskclient.base.utils.ConfigHelper;
+
+/**
+ * Implements all SRP algorithm logic.
+ * <p/>
+ * 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
+     */
+    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 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
+     * @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;
+    }
+
+    public static void setToken(String token) {
+        LeapSRPSession.token = token;
+    }
+
+    public static String getToken() {
+        return token;
+    }
+
+    public static boolean loggedIn() {
+        return !token.isEmpty();
+    }
+
+    /**
+     * @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;
+    }
+}