From 2263abad65b92ef26c8e67097bbcfeb6988ab8fd Mon Sep 17 00:00:00 2001
From: Azul <azul@riseup.net>
Date: Sun, 14 Oct 2012 16:24:10 +0200
Subject: calculating the right M and M2!

still missing some error handling, this in Django specs and the right http verbs
---
 spec/restful/login.js |  7 ++++++-
 src/srp_session.js    | 47 ++++++++++++++++++++++++++++++++++-------------
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/spec/restful/login.js b/spec/restful/login.js
index 8da6cfd..3bf9dda 100644
--- a/spec/restful/login.js
+++ b/spec/restful/login.js
@@ -16,6 +16,7 @@ describe("Login", function() {
     var b = '6aa5c88d1877af9907ccefad31083e1102a7121dc04706f681f66c8680fb7f05'; 
     var B = 'd56a80aaafdf9f70598b5d1184f122f326a333fafd37ab76d6f7fba4a9c4ee59545be056335150bd64f04880bc8e76949469379fe9de17cf6f36f3ee11713d05f63050486bc73c545163169999ff01b55c0ca4e90d8856a6e3d3a6ffc70b70d993a5308a37a5c2399874344e083e72b3c9afa083d312dfe9096ea9a65023f135';
     var salt = '628365a0';
+    var K = 'db6ec0bdab81742315861a828323ff492721bdcd114077a4124bc425e4bf328b';
     var M = '640e51d5ac5461591c31811221261f0e0eae7c08ce43c85e9556adbd94ed8c26';
     var M2 = '49e48f8ac8c4da0e8a7374f73eeedbee2266e123d23fc1be1568523fc9c24b1e';
     var A_, callback;
@@ -38,6 +39,11 @@ describe("Login", function() {
       expect(A_).toBe(A);
     });
 
+    it("calculates the right key", function(){
+      this.srp.session.calculations(salt, B);
+      expect(this.srp.session.key()).toBe(K);
+    });
+
     it("works with JSON responses", function(){
       this.srp.identify();
 
@@ -63,4 +69,3 @@ describe("Login", function() {
 
 
 });
-
diff --git a/src/srp_session.js b/src/srp_session.js
index afd653a..07c1e25 100644
--- a/src/srp_session.js
+++ b/src/srp_session.js
@@ -66,9 +66,9 @@ SRP.prototype.Session = function() {
   };
 
   // Calculates the X value and return it as a BigInteger
-  this.calcX = function(s)
+  this.calcX = function(salt)
   {
-    return new BigInteger(SHA256(hex2a(s + SHA256(I + ":" + pass))), 16);
+    return new BigInteger(SHA256(hex2a(salt + SHA256(I + ":" + pass))), 16);
   };
 
   this.getV = function(salt)
@@ -85,18 +85,30 @@ SRP.prototype.Session = function() {
     var B = new BigInteger(ephemeral, 16); 
     var Bstr = ephemeral;
     // u = H(A,B)
-    var u = new BigInteger(SHA256(Astr + Bstr), 16); 
+    var u = new BigInteger(SHA256(hex2a(Astr + Bstr)), 16); 
     // x = H(s, H(I:p))
-    var x = new BigInteger(SHA256(salt + SHA256(I + ":" + pass)), 16);
+    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); 
-    // M = H(H(N) xor H(g), H(I), s, A, B, K)
-    var Mstr = A.toString(16) + B.toString(16) + S.toString(16); 
-    M = SHA256(Mstr);
-    M2 = SHA256(A.toString(16) + M + S.toString(16)); 
+    K = SHA256(hex2a(S.toString(16)));
+    this.calcM(salt, A.toString(16), B.toString(16));
+  };
+
+  // M = H(H(N) xor H(g), H(I), s, A, B, K)
+  this.calcM = function(salt, Astr, Bstr) {
+    var hashN = SHA256(hex2a(N.toString(16)))
+    var hashG = SHA256(hex2a(g.toString(16)))
+    var hexString = hexXor(hashN, hashG);
+    hexString += SHA256(I);
+    hexString += salt;
+    hexString += Astr;
+    hexString += Bstr;
+    hexString += K
+    M = SHA256(hex2a(hexString));
     //M2 = H(A, M, K)
+    M2 = SHA256(hex2a(Astr + M + K));
   };
 
   this.getM = function() {
@@ -112,13 +124,11 @@ SRP.prototype.Session = function() {
   // access the key with this function.
   this.key = function()
   {
-    if(K) return K;
-    if(authenticated) {
-      K = SHA256(S.toString(16));
+    if(K) {
       return K;
-    }
-    else
+    } else {
       this.onError("User has not been authenticated.");
+    }
   };
 
   // Encrypt plaintext using slowAES
@@ -143,4 +153,15 @@ SRP.prototype.Session = function() {
     return str;
   }
 
+  function hexXor(a, b) {
+    var str = '';
+    for (var i = 0; i < a.length; i += 2) {
+      var xor = parseInt(a.substr(i, 2), 16) ^ parseInt(b.substr(i, 2), 16)
+      xor = xor.toString(16);
+      str += (xor.length == 1) ? ("0" + xor) : xor
+    }
+    return str;
+  }
+
+
 }
-- 
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