refactor: separate calculations from session

7 files changed, 165 insertions, 123 deletions

diff --git a/spec/constants_spec.js b/spec/constants_spec.js
new file mode 100644
index 0000000..a8aa7fd
--- /dev/null
+++ b/spec/constants_spec.js
@@ -0,0 +1,35 @@
+describe("Constants", function() {
+  
+  beforeEach(function() {
+    constants = new srp.Constants();
+  });
+
+  // login attempt with correct password that failed never the less:
+  var compare = {
+    username: "blues",
+    password: "justtest",
+    salt: "6a6ef9ce5cb998eb",
+      v: "a5da6d376d503e22d93385db0244c382d1413d9f721ad9866dfc5e895cf2a3331514ceec5f48aceab58b260651cc9ee1ba96d906f67a6b4a7414c82d1333607ebe96403ecc86050224dc4c17b1d30efdbb451a68d1b6a25cce10f0e844082329d3cb46e1c3d46298a0de2cd3b8c6acc1a80c206f0f10ec8cd3c050babdf338ba",
+    aa: "4decb8543891f5a744b1e9b5bc375a474bfe3c5417e1db176cefcc7ba915338a14f309f8e0a4c7641bc9c9b9bd2e91c4d1beda1772c30d0350c9ba44f7c5911dfe6bb593ac2a2b30f1f6e5ec8a656cb4947c1907cf62f8d7283cbe32eb44b02158b51091ae130afa6063bb28cdea9ae159d4f222571e146f8715bfa31af09868",
+    a: "d498c3d024ec17689b5320e33fc349a3f3f91320384155b3043fa410c90eab71",
+    bb: "dee64fd54daafc18b338c5783ade3ff4275dfee8c97008e2d9fb445880a2e1d452c822a35e8e3f012bc6facaa28022f8de3fb1d632667d635abde0afc0ca4ed06c9197ea88f379042b10bc7b7f816a1ec14fefe6e9adef4ab904315b3a3f36749f3f6d1083b0eb0029173770f8e9342b098298389ba49a88d4ea6b78a7f576a4",
+    s: "50973f6e8134f95bd04f54f522e6e57d957d0640f91f0a989ff775712b81d5856ae3bdd2aa9c5eda8019e9db18065519c99c33a62c7f12f98e7aed60b153feee9ab73ba1272b4d76aa002da8cd47c6da733c88a0e70d4c3d6752fd366d66efe40870d26fd5d1755883b9489721e1881376628bf6ef89902f35e5e7e31227e2f",
+    k: "dd93e648abfe2ac6c6d46e062ded60b31ec043e55ceca1946ec29508f4c68461",
+    m: "ccf0c492f715484dc8343e22cd5967c2c5d01de743c5f0a9c5cfd017db1804c"
+  };
+  
+  it("calculates the proper A", function() {
+    expect(constants.calcA(compare.a)).toBe(compare.aa);
+  });
+  
+  it("calculates the right x", function() {
+    x = constants.calcX("testuser","password","7686acb8")
+    expect(x).toBe('84d6bb567ddf584b1d8c8728289644d45dbfbb02deedd05c0f64db96740f0398');
+  });
+
+  it("calculates the right verifier", function() {
+    x = constants.calcX(compare.username, compare.password, compare.salt)
+    expect(constants.calcV(x)).toBe(compare.v);
+  });
+  
+});
diff --git a/spec/login_spec.js b/spec/login_spec.js
index 8f54a1e..7c47528 100644
--- a/spec/login_spec.js
+++ b/spec/login_spec.js
@@ -32,10 +32,6 @@ describe("Login with srp var", function() {
       expect(A_).toBe(A);
     });
 
-    it("calculates the same verifier", function(){
-      expect(srp.session.getV(salt).toString(16)).toBe(V);
-    });
-
     it("calculates the same key", function(){
       srp.session.calculations(salt, B);
       expect(srp.session.key()).toBe(K);
diff --git a/spec/runner.html b/spec/runner.html
index 5f4727c..e94cd24 100644
--- a/spec/runner.html
+++ b/spec/runner.html
@@ -23,12 +23,14 @@
   <script type="text/javascript" src="../lib/jsbn2.js"></script>
   <script type="text/javascript" src="../src/srp.js"></script>
   <script type="text/javascript" src="../src/jqueryRest.js"></script>
+  <script type="text/javascript" src="../src/srp_constants.js"></script>
   <script type="text/javascript" src="../src/srp_session.js"></script>
   
   <!-- include spec files here... -->
   <script type="text/javascript" src="helper.js"></script>
   <script type="text/javascript" src="signup_spec.js"></script>
   <script type="text/javascript" src="login_spec.js"></script>
+  <script type="text/javascript" src="constants_spec.js"></script>
   <script type="text/javascript" src="session_spec.js"></script>
 
   <script type="text/javascript">
diff --git a/spec/session_spec.js b/spec/session_spec.js
index acfe0be..5802283 100644
--- a/spec/session_spec.js
+++ b/spec/session_spec.js
@@ -36,14 +36,6 @@ describe("Session", function() {
     expect(session.getI()).toBe(compare.username);
   });
 
-  it("calculates the proper verifier", function() {
-    expect(session.getV(compare.salt).toString(16)).toBe(compare.v);
-  });
-
-  it("calculates the proper A", function() {
-    expect(session.calculateAndSetA(compare.a)).toBe(compare.aa);
-  });
-
   it("calculates the proper M", function() {
     session.calculateAndSetA(compare.a);
     session.calculations(compare.salt, compare.bb);
diff --git a/spec/signup_spec.js b/spec/signup_spec.js
index 72689b1..70c6823 100644
--- a/spec/signup_spec.js
+++ b/spec/signup_spec.js
@@ -3,17 +3,15 @@ describe("Loading SRP", function() {
     expect(typeof srp.signup).toBe('function');
   });
 
-  it("provides session which calculates the right x", function(){
-    srp.session = new srp.Session();
-    expect(srp.session.calcX("7686acb8").toString(16)).toBe('84d6bb567ddf584b1d8c8728289644d45dbfbb02deedd05c0f64db96740f0398');
-  });
 });
 
 describe("Signup with srp var", function() {
   
   beforeEach(function() {
     specHelper.setupFakeXHR.apply(this);
-    srp.session = new srp.Session();
+    constants = new srp.Constants();
+    constants.randomSalt = function() {return "4c78c3f8"};
+    srp.session = new srp.Session(undefined, undefined, constants);
   });
 
   afterEach(function() {
@@ -23,7 +21,6 @@ describe("Signup with srp var", function() {
   it("identifies after successful registration (INTEGRATION)", function(){
     var callback = sinon.spy();
     srp.signedUp = callback;
-    srp.session.getSalt = function() {return "4c78c3f8"};
     srp.signup();
     this.expectRequest('/users.json', "user[login]=testuser&user[password_salt]=4c78c3f8&user[password_verifier]=474c26aa42d11f20544a00f7bf9711c4b5cf7aab95ed448df82b95521b96668e7480b16efce81c861870302560ddf6604c67df54f1d04b99d5bb9d0f02c6051ada5dc9d594f0d4314e12f876cfca3dcd99fc9c98c2e6a5e04298b11061fb8549a22cde0564e91514080df79bca1c38c682214d65d590f66b3719f954b078b83c", 'POST')
     this.respondJSON({password_salt: "4c78c3f8", login: "testuser", ok: "true"});
diff --git a/src/srp_constants.js b/src/srp_constants.js
new file mode 100644
index 0000000..3d7ec85
--- /dev/null
+++ b/src/srp_constants.js
@@ -0,0 +1,101 @@
+srp.Constants = function() {
+
+  // Variables used in the SRP protocol
+  var Nstr = "eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c256576d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089dad15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e57ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb06e3";
+  var N = new BigInteger(Nstr, 16);
+  var g = new BigInteger("2");
+  var k = new BigInteger("bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0", 16);
+  var rng = new SecureRandom();
+
+  this.calcA = function(_a) { 
+    a = new BigInteger(_a, 16);
+    return g.modPow(a, N).toString(16);
+  };
+
+  // Calculates the X value
+  // x = H(s, H(I:p))
+  this.calcX = function(login, password, salt) {
+    var salted = salt + SHA256(login + ":" + password)
+    return SHA256(hex2a(salted));
+  };
+
+  this.calcV = this.calcA;
+
+  // u = H(A,B)
+  this.calcU = function(A, B) {
+    return SHA256(hex2a(A + B)); 
+  };
+
+  //S = (B - kg^x) ^ (a + ux)
+  this.calcS = function(_a, _A, _B, _x) {
+    var a = new BigInteger(_a, 16);
+    var x = new BigInteger(_x, 16);
+    var u = new BigInteger(this.calcU(_A, _B), 16);
+    var B = new BigInteger(_B, 16);
+    
+    var kgx = k.multiply(g.modPow(x, N));  
+    var aux = a.add(u.multiply(x)); 
+    
+    return B.subtract(kgx).modPow(aux, N).toString(16); 
+  }
+
+  this.calcK = function(_S) {
+    return SHA256(hex2a(_S));
+  }
+
+  this.nXorG = function() {
+    var hashN = SHA256(hex2a(Nstr));
+    var hashG = SHA256(hex2a(g.toString(16)));
+    return hexXor(hashN, hashG);
+  };
+
+  this.hash = function(hexString) {
+    return removeLeading0(SHA256(hex2a(hexString)));
+  };
+
+  this.isInvalidEphemeral = function(a) {
+    return (g.modPow(a, N) == 0);
+  };
+
+  this.randomEphemeral = function() {
+    var a = new BigInteger(32, rng);
+    while(this.isInvalidEphemeral(a))
+    {
+      a = new BigInteger(32, rng);
+    }
+    return a.toString(16);
+  };
+  
+  // some 16 byte random number
+  this.randomSalt = function() {
+    return new BigInteger(64, rng).toString(16);
+  }
+
+  function hex2a(hex) {
+    var str = '';
+    if(hex.length % 2) {
+      hex = "0" + hex;
+    }
+    for (var i = 0; i < hex.length; i += 2)
+      str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
+    return str;
+  }
+
+  function removeLeading0(hex) {
+    if (hex[0] == "0") {
+      return hex.substr(1);
+    } else {
+      return hex;
+    }
+  }
+
+  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;
+  }
+};
diff --git a/src/srp_session.js b/src/srp_session.js
index f895f4a..babb96a 100644
--- a/src/srp_session.js
+++ b/src/srp_session.js
@@ -1,20 +1,9 @@
-srp.Session = function(login, password) {
+srp.Session = function(login, password, constants) {
   
-  // Variables session will be used in the SRP protocol
-  var Nstr = "eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c256576d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089dad15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e57ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb06e3";
-  var N = new BigInteger(Nstr, 16);
-  var g = new BigInteger("2");
-  var k = new BigInteger("bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0", 16);
-
-  var rng = new SecureRandom();
-  var a = new BigInteger(32, rng);
-  var A = g.modPow(a, N);
-  while(A.mod(N) == 0)
-  {
-    a = new BigInteger(32, rng);
-    A = g.modPow(a, N);
-  }
-  var Astr = A.toString(16);
+
+  var constants = constants || new srp.Constants();
+  var a = constants.randomEphemeral();
+  var A = constants.calcA(a);
   var S = null;
   var K = null;
   var M = null;
@@ -28,30 +17,30 @@ srp.Session = function(login, password) {
   // allows setting the random number A for testing
 
   this.calculateAndSetA = function(_a) {
-    a = new BigInteger(_a, 16);
-    A = g.modPow(a, N);
-    Astr = A.toString(16);
-    return Astr;
+    a = _a;
+    A = constants.calcA(_a);
+    return A;
   };
 
   this.signup = function() {
-    var salt = this.getSalt();
+    var salt = constants.randomSalt();
+    var x = constants.calcX(this.getI(), this.getPass(), salt);
     return {
       login: this.getI(),
       password_salt: salt,
-      password_verifier: this.getV(salt).toString(16)
+      password_verifier: constants.calcV(x)
     };
   };
 
   this.handshake = function() {
     return { 
       login: this.getI(), 
-      A: this.getAstr()
+      A: this.getA()
     };
   };
 
-  this.getAstr = function() {
-    return Astr;
+  this.getA = function() {
+    return A;
   }
 
   // Returns the user's identity
@@ -66,66 +55,24 @@ srp.Session = function(login, password) {
     return pass;
   };
 
-  // some 16 byte random number
-  this.getSalt = function() {
-    return new BigInteger(64, rng).toString(16);
-  }
-
-  // Returns the BigInteger, g
-  this.getg = function() {
-    return g;
-  };
-
-  // Returns the BigInteger, N
-  this.getN = function() {
-    return N;
-  };
-
-  // Calculates the X value and return it as a BigInteger
-  this.calcX = function(salt) {
-    var inner = salt + SHA256(this.getI() + ":" + this.getPass())
-    return new BigInteger(SHA256(hex2a(inner)), 16);
-  };
-
-  this.getV = function(salt)
-  {
-    return this.getg().modPow(this.calcX(salt), this.getN());
-  }
-
   // Calculate S, M, and M2
   // This is the client side of the SRP specification
   this.calculations = function(salt, ephemeral)
   {    
     //S -> C: s | B
-    var B = new BigInteger(ephemeral, 16); 
-    var Bstr = ephemeral;
-    // u = H(A,B)
-    var u = new BigInteger(SHA256(hex2a(Astr + Bstr)), 16); 
-    // x = H(s, H(I:p))
-    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); 
-    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 = removeLeading0(SHA256(hex2a(hexString)));
+    var B = ephemeral;
+    var x = constants.calcX(this.getI(), this.getPass(), salt);
+    S = constants.calcS(a, A, B, x);
+    K = constants.calcK(S);
+    
+    // M = H(H(N) xor H(g), H(I), s, A, B, K)
+    var xor = constants.nXorG();
+    M = constants.hash(xor + SHA256(I) + salt + A + B + K);
     //M2 = H(A, M, K)
-    M2 = removeLeading0(SHA256(hex2a(Astr + M + K)));
+    M2 = constants.hash(A + M + K);
   };
 
+
   this.getS = function() {
     return S;
   }
@@ -164,33 +111,5 @@ srp.Session = function(login, password) {
       retstring = retstring.replace("+", "_");
     return retstring;
   };
-
-  function removeLeading0(hex) {
-    if (hex[0] == "0") {
-      return hex.substr(1);
-    } else {
-      return hex;
-    }
-  }
-
-  function hex2a(hex) {
-    var str = '';
-    if(hex.length % 2) {
-      hex = "0" + hex;
-    }
-    for (var i = 0; i < hex.length; i += 2)
-      str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
-    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;
-  }
 };