Add state generation and check

authorization_code/app.js

@@ -10,17 +10,39 @@
 var express = require('express'); // Express web server framework
 var request = require('request'); // "Request" library
 var querystring = require('querystring');
+var cookieParser = require('cookie-parser');
 
 var client_id = '03ffe0cac0a0401aa6673c3cf6d02ced'; // Your client id
 var client_secret = 'a57c43efb9644574a96d6623fb8bfbc2'; // Your client secret
 var redirect_uri = 'http://localhost:8888/callback'; // Your redirect uri
 
+/**
+ * Generates a random string containing numbers and letters
+ * @param  {number} length The length of the string
+ * @return {string} The generated string
+ */
+var generateRandomString = function(length) {
+  var text = '';
+  var possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+
+  for (var i = 0; i < length; i++) {
+    text += possible.charAt(Math.floor(Math.random() * possible.length));
+  }
+  return text;
+};
+
+var stateKey = 'spotify_auth_state';
+
 var app = express();
 
-app.use(express.static(__dirname + '/public'));
+app.use(express.static(__dirname + '/public'))
+   .use(cookieParser());
 
 app.get('/login', function(req, res) {
 
+  var state = generateRandomString(16);
+  res.cookie(stateKey, state);
+
   // your application requests authorization
   var scope = 'user-read-private user-read-email';
   res.redirect('https://accounts.spotify.com/authorize?' +
@@ -28,14 +50,27 @@ app.get('/login', function(req, res) {
       response_type: 'code',
       client_id: client_id,
       scope: scope,
-      redirect_uri: redirect_uri
+      redirect_uri: redirect_uri,
+      state: state
     }));
 });
 
 app.get('/callback', function(req, res) {
 
   // your application requests refresh and access tokens
-  var code = req.query.code;
+  // after checking the state parameter
+
+  var code = req.query.code || null;
+  var state = req.query.state || null;
+  var storedState = req.cookies ? req.cookies[stateKey] : null;
+
+  if (state === null || state !== storedState) {
+    res.redirect('/#' +
+      querystring.stringify({
+        error: 'state_mismatch'
+      }));
+  } else {
+    res.clearCookie(stateKey);
     var authOptions = {
       url: 'https://accounts.spotify.com/api/token',
       form: {
@@ -71,8 +106,14 @@ app.get('/callback', function(req, res) {
             access_token: access_token,
             refresh_token: refresh_token
           }));
+      } else {
+        res.redirect('/#' +
+          querystring.stringify({
+            error: 'invalid_token'
+          }));
       }
     });
+  }
 });
 
 app.get('/refresh_token', function(req, res) {

authorization_code/public/index.html

@@ -89,8 +89,12 @@
         var params = getHashParams();
 
         var access_token = params.access_token
-            refresh_token = params.refresh_token;
+            refresh_token = params.refresh_token,
+            error = params.error;
 
+        if (error) {
+          alert('There was an error during the authentication');
+        } else {
           oauthPlaceholder.innerHTML = oauthTemplate({
             access_token: access_token,
             refresh_token: refresh_token
@@ -128,7 +132,7 @@
               });
             });
           }, false);
-
+        }
       })();
     </script>
 </html>

implicit_grant/public/index.html

@@ -62,6 +62,8 @@
     <script>
       (function() {
 
+        var stateKey = 'spotify_auth_state';
+
         /**
          * Obtains parameters from the hash of the URL
          * @return Object
@@ -76,6 +78,21 @@
           return hashParams;
         }
 
+        /**
+         * Generates a random string containing numbers and letters
+         * @param  {number} length The length of the string
+         * @return {string} The generated string
+         */
+        function generateRandomString(length) {
+          var text = '';
+          var possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+
+          for (var i = 0; i < length; i++) {
+            text += possible.charAt(Math.floor(Math.random() * possible.length));
+          }
+          return text;
+        };
+
         var userProfileSource = document.getElementById('user-profile-template').innerHTML,
             userProfileTemplate = Handlebars.compile(userProfileSource),
             userProfilePlaceholder = document.getElementById('user-profile');
@@ -86,12 +103,14 @@
 
         var params = getHashParams();
 
-        var access_token = params.access_token;
-
-        oauthPlaceholder.innerHTML = oauthTemplate({
-          access_token: access_token
-        });
+        var access_token = params.access_token,
+            state = params.state,
+            storedState = localStorage.getItem(stateKey);
 
+        if (access_token && (state == null || state !== storedState)) {
+          alert('There was an error during the authentication');
+        } else {
+          localStorage.removeItem(stateKey);
           if (access_token) {
             $.ajax({
                 url: 'https://api.spotify.com/v1/me',
@@ -115,6 +134,9 @@
             var client_id = '03ffe0cac0a0401aa6673c3cf6d02ced'; // Your client id
             var redirect_uri = 'http://localhost:8888/'; // Your redirect uri
 
+            var state = generateRandomString(16);
+
+            localStorage.setItem(stateKey, state);
             var scope = 'user-read-private user-read-email';
 
             var url = 'https://accounts.spotify.com/authorize';
@@ -122,10 +144,11 @@
             url += '&client_id=' + encodeURIComponent(client_id);
             url += '&scope=' + encodeURIComponent(scope);
             url += '&redirect_uri=' + encodeURIComponent(redirect_uri);
+            url += '&state=' + encodeURIComponent(state);
 
             window.location = url;
           }, false);
-
+        }
       })();
     </script>
 </html>

package.json

@@ -5,8 +5,9 @@
   "version": "0.0.1",
   "main": "app.js",
   "dependencies": {
+    "cookie-parser": "1.3.2",
     "express": "~4.0.0",
-    "request": "~2.34.0",
-    "querystring": "~0.2.0"
+    "querystring": "~0.2.0",
+    "request": "~2.34.0"
   }
 }