Fix OmniAuth OAuth2Generic strategy not loading

In https://github.com/rails/rails/commit/83b767ce, Rails 5.1 removed
support for using a String to specify a middleware. When the
strategy_class argument is passed from the GitLab YAML config to Devise,
Devise passes the string value straight through to Rails, and GitLab
would crash with a NoMethodError inside ActionDispatch::MiddlewareStack.

To make this OmniAuth strategy work again, we normalize the arguments by
converting the strategy_class value into an actual Class.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/62216

1 files changed, 14 insertions, 1 deletions

diff --git a/lib/gitlab/omniauth_initializer.rb b/lib/gitlab/omniauth_initializer.rb
index e0ac9eec1f2..2a2083ebae0 100644
--- a/lib/gitlab/omniauth_initializer.rb
+++ b/lib/gitlab/omniauth_initializer.rb
@@ -36,12 +36,25 @@ module Gitlab
         hash_arguments = provider['args'].merge(provider_defaults(provider))
 
         # A Hash from the configuration will be passed as is.
-        provider_arguments << hash_arguments.symbolize_keys
+        provider_arguments << normalize_hash_arguments(hash_arguments)
       end
 
       provider_arguments
     end
 
+    def normalize_hash_arguments(args)
+      args.symbolize_keys!
+
+      # Rails 5.1 deprecated the use of string names in the middleware
+      # (https://github.com/rails/rails/commit/83b767ce), so we need to
+      # pass in the actual class to Devise.
+      if args[:strategy_class].is_a?(String)
+        args[:strategy_class] = args[:strategy_class].constantize
+      end
+
+      args
+    end
+
     def provider_defaults(provider)
       case provider['name']
       when 'cas3'