Added steam auth using encrypted application tickets

Not tested working though yet

src/Adapters/Auth/index.js

@@ -23,6 +23,7 @@ import oauth2 from './oauth2';
 const phantauth = require('./phantauth');
 import qq from './qq';
 import spotify from './spotify';
+const steam = require("./steam");
 import twitter from './twitter';
 const vkontakte = require('./vkontakte');
 import wechat from './wechat';
@@ -50,6 +51,7 @@ const providers = {
   google,
   github,
   twitter,
+  steam,
   spotify,
   anonymous,
   digits,

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();
+}