Added steam auth using encrypted application tickets

Not tested working though yet

package.json

@@ -38,6 +38,7 @@
     "redis": "2.8.0",
     "request": "2.85.0",
     "semver": "5.5.0",
+    "steam-appticket": "1.0.1",
     "tv4": "1.3.0",
     "uuid": "^3.1.0",
     "winston": "2.4.1",

src/Adapters/Auth/index.js

@@ -16,6 +16,7 @@ const vkontakte = require("./vkontakte");
 const qq = require("./qq");
 const wechat = require("./wechat");
 const weibo = require("./weibo");
+const steam = require("./steam");
 
 const anonymous = {
   validateAuthData: () => {
@@ -43,7 +44,8 @@ const providers = {
   vkontakte,
   qq,
   wechat,
-  weibo
+  weibo,
+  steam
 }
 function authDataValidator(adapter, appIds, options) {
   return function(authData) {

src/Adapters/Auth/steam.js

@@ -0,0 +1,36 @@
+var Parse = require('parse/node').Parse;
+const AppTicket = require('steam-appticket');
+
+// todo move these to a config file.
+const decryptionKey = '3e3e2a3cbd54dc6c7cb5e51520dfa819dd7f9c12d062d54a1f8c14ddd231377f';
+const appId = '3414340';
+
+// Returns a promise that fulfills iff this application ticket is valid
+function validateAuthData(authData) {
+    var encrypted_ticket = Buffer.from(authData.app_ticket, 'hex');
+    var ticket = AppTicket.parseEncryptedAppTicket(encrypted_ticket, decryptionKey)
+    if (ticket === null) {
+        throw new Parse.Error(
+            Parse.Error.OBJECT_NOT_FOUND,
+            'Steam auth is invalid for this user.');
+    }
+    var user_id = authData.id;
+    if (user_id != ticket.steamID.accountid) {
+        throw new Parse.Error(
+            Parse.Error.OBJECT_NOT_FOUND,
+            'The provided application ticket does not match the given user id'
+        );
+    }
+    if (appId !== ticket.appID && demoAppId != ticket.appID) {
+        throw new Parse.Error(
+            Parse.Error.OBJECT_NOT_FOUND,
+            'The provided application ticket does not match the Kami 2 or Kami 2 Demo application ids'
+        );
+    }
+    return Promise.resolve();
+}
+
+// steam auth bundles the app id in the auth data so don't validate seperately
+function validateAppId() {
+  return Promise.resolve();
+}