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function SRP(username, password, ser, base_url)
{
// Variables that will be used in the SRP protocol
var Nstr = "115b8b692e0e045692cf280b436735c77a5a9e8a9e7ed56c965f87db5b2a2ece3";
var N = new BigInteger(Nstr, 16);
var g = new BigInteger("2");
var k = new BigInteger("c46d46600d87fef149bd79b81119842f3c20241fda67d06ef412d8f6d9479c58", 16);
var rng = new SecureRandom();
var a = new BigInteger(32, rng);
var A = g.modPow(a, N);
var Astr = A.toString(16);
var B = null;
var Bstr = null;
var I = username;
var u = null;
var p = password;
var x = null;
var S = null;
var K = null;
var M = null;
var M2 = null;
var xhr = null;
var url = base_url;
var server = ser;
var that = this;
var authenticated = false;
var hash_import = false;
function paths(str)
{
// For now, str will be the django path
// This function will translate for other backends.
if(server == "django")
{
return str;
}
};
// Perform ajax requests at the specified url, with the specified parameters
// Calling back the specified function.
function ajaxRequest(full_url, params, callback)
{
if( window.XMLHttpRequest)
xhr = new XMLHttpRequest();
else if (window.ActiveXObject){
try{
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}catch (e){}
}
else
{
that.error_message("Ajax not supported.");
return;
}
if(xhr){
xhr.onreadystatechange = callback;
xhr.open("POST", full_url, true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.setRequestHeader("Content-length", params.length);
xhr.setRequestHeader("Connection", "close");
xhr.send(params);
}
else
{
that.error_message("Ajax failed.");
}
};
// Get the text content of an XML node
function innerxml (node)
{
return node.firstChild.nodeValue;
};
// Check whether or not a variable is defined
function isdefined ( variable)
{
return (typeof(window[variable]) != "undefined");
};
// Initiate the registration process
this.register = function()
{
var handshake_url = url + paths("register/salt/");
var params = "I="+I;
ajaxRequest(handshake_url, params, register_receive_salt);
};
// Receive the salt for registration
function register_receive_salt()
{
if(xhr.readyState == 4 && xhr.status == 200) {
if(xhr.responseXML.getElementsByTagName("salt").length > 0)
{
var s = innerxml(xhr.responseXML.getElementsByTagName("salt")[0]);
x = new BigInteger(SHA256(s + SHA256(I + ":" + p)), 16);
var v = g.modPow(x, N);
register_send_verifier(v.toString(16));
}
else if(xhr.responseXML.getElementsByTagName("error").length > 0)
{
that.error_message(innerxml(xhr.responseXML.getElementsByTagName("error")[0]));
}
}
};
// Send the verifier to the server
function register_send_verifier(v)
{
var params = "v="+v;
var auth_url = url + paths("register/user/");
ajaxRequest(auth_url, params, register_user);
};
// The user has been registered successfully, now login
function register_user()
{
if(xhr.readyState == 4 && xhr.status == 200) {
if(xhr.responseXML.getElementsByTagName("ok").length > 0)
{
that.identify();
}
}
};
// Start the login process by identifying the user
this.identify = function()
{
var handshake_url = url + paths("handshake/");
var params = "I="+I+"&A="+Astr;
ajaxRequest(handshake_url, params, receive_salts);
};
// Receive login salts from the server, start calculations
function receive_salts()
{
if(xhr.readyState == 4 && xhr.status == 200) {
if(xhr.responseXML.getElementsByTagName("r").length > 0)
{
var response = xhr.responseXML.getElementsByTagName("r")[0];
calculations(response.getAttribute("s"), response.getAttribute("B"));
}
else if(xhr.responseXML.getElementsByTagName("error").length > 0)
{
// This probably means A % N == 0, which means we need to generate
// a new A and reidentify.
that.identify();
}
}
};
// Calculate S, M, and M2
function calculations(s, ephemeral)
{
//S -> C: s | B
B = new BigInteger(ephemeral, 16);
Bstr = ephemeral;
// u = H(A,B)
u = new BigInteger(SHA256(Astr + Bstr), 16);
// x = H(s, H(I:p))
x = new BigInteger(SHA256(s + SHA256(I + ":" + p)), 16);
//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));
send_hash(M);
//M2 = H(A, M, K)
};
// Send M to the server
function send_hash(M)
{
var params = "M="+M;
var auth_url = url+paths("authenticate/");
ajaxRequest(auth_url, params, confirm_authentication);
};
// Receive M2 from the server and verify it
function confirm_authentication()
{
if(xhr.readyState == 4 && xhr.status == 200) {
if(xhr.responseXML.getElementsByTagName("M").length > 0)
{
if(innerxml(xhr.responseXML.getElementsByTagName("M")[0]) == M2)
{
alert(that.srpPath);
that.success();
authenticated = true;
}
else
that.error_message("Server key does not match");
}
else if (xhr.responseXML.getElementsByTagName("error").length > 0)
{
that.error_message(innerxml(xhr.responseXML.getElementsByTagName("error")[0]));
}
}
};
// If we need SHA1 or MD5, we need to load the javascript files
function import_hashes()
{
// First check that the functions aren't already loaded
if(that.isdefined("SHA1") && that.isdefined("MD5")) return;
// Get the directory that this javascript file was loaded from
var arr=that.srpPath.split("/");
var path = arr.slice(0, arr.length-1).join("/");
// If this file is called srp.min.js, we will load the packed hash file
if(arr[arr.length-1] == "srp.min.js")
{
var scriptElt = document.createElement('script');
scriptElt.type = 'text/javascript';
scriptElt.src = path+"/hash.min.js";
document.getElementsByTagName('head')[0].appendChild(scriptElt);
}
// Otherwise, this file is presumably srp.js, and we will load individual hash files
else
{
var scriptElt = document.createElement('script');
scriptElt.type = 'text/javascript';
scriptElt.src = path +"/MD5.js";
document.getElementsByTagName('head')[0].appendChild(scriptElt);
scriptElt = document.createElement('script');
scriptElt.type = 'text/javascript';
scriptElt.src = path +"/SHA1.js";
document.getElementsByTagName('head')[0].appendChild(scriptElt);
}
}
// If someone wants to use the session key for encrypting traffic, they can
// access the key with this function.
this.key = function()
{
if(K == null)
if(authenticated)
{
K = SHA256(S);
return K;
}
else
that.error_message("User has not been authenticated.");
else
return K;
};
// This function is called when authentication is successful.
// Developers can set this to other functions in specific implementations
// and change the functionality.
this.success = function()
{
alert("Authentication successful.");
};
// If an error occurs, raise it as an alert.
// Developers can set this to an alternative function to handle erros differently.
this.error_message = function(t)
{
alert(t);
};
};
// This line is run while the document is loading
// It gets a list of all <script> tags and finds the last instance.
// The path to this script is the "src" attribute of that tag.
SRP.prototype.srpPath = document.getElementsByTagName('script')[document.getElementsByTagName('script').length-1].getAttribute("src");
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