Add a feature flag to disable user creation

endpoints/callbacks.py

@@ -26,7 +26,8 @@ def render_ologin_error(service_name,
                         error_message='Could not load user data. The token may have expired.'):
   return render_page_template('ologinerror.html', service_name=service_name,
                               error_message=error_message,
-                              service_url=get_app_url())
+                              service_url=get_app_url(),
+                              user_creation=features.USER_CREATION)
 
 def exchange_code_for_token(code, service_name='GITHUB', for_login=True, form_encode=False,
                             redirect_suffix=''):
@@ -85,7 +86,12 @@ def get_google_user(token):
 def conduct_oauth_login(service_name, user_id, username, email, metadata={}):
   to_login = model.verify_federated_login(service_name.lower(), user_id)
   if not to_login:
-    # try to create the user
+    # See if we can create a new user.
+    if not features.USER_CREATION:
+      error_message = 'User creation is disabled. Please contact your administrator'
+      return render_ologin_error(service_name, error_message)
+
+    # Try to create the user
     try:
       valid = next(generate_valid_usernames(username))
       to_login = model.create_federated_user(valid, email, service_name.lower(),
@@ -147,7 +153,7 @@ def github_oauth_callback():
 
   token = exchange_code_for_token(request.args.get('code'), service_name='GITHUB')
   user_data = get_github_user(token)
-  if not user_data:
+  if not user_data or not 'login' in user_data:
     return render_ologin_error('GitHub')
 
   username = user_data['login']