Fix sign_in on secondary with relative URL

Relative URL wasn't handled correctly

ee/app/controllers/ee/sessions_controller.rb

@@ -14,7 +14,9 @@ module EE
       return super if signed_in?
 
       if ::Gitlab::Geo.secondary_with_primary?
-        redirect_to oauth_geo_auth_url(host: GeoNode.current_node_url, state: geo_login_state.encode)
+        current_node_uri = URI(GeoNode.current_node_url)
+        state = geo_login_state.encode
+        redirect_to oauth_geo_auth_url(host: current_node_uri.host, port: current_node_uri.port, state: state)
       else
         super
       end

ee/changelogs/geo-fix-oauth-redirect.yml

+---
+title: 'Geo: Fix sign in on secondary with relative URL'
+merge_request: 37445
+author:
+type: fixed

ee/spec/controllers/ee/sessions_controller_spec.rb

@@ -32,6 +32,18 @@ RSpec.describe SessionsController, :geo do
         end
       end
 
+      context 'when relative URL is configured' do
+        before do
+          host = 'http://this.is.my.host/secondary-relative-url-part'
+
+          stub_config_setting(url: host, https: false)
+          stub_default_url_options(host: "this.is.my.host", script_name: '/secondary-relative-url-part')
+          request.headers['HOST'] = host
+        end
+
+        it_behaves_like 'a valid oauth authentication redirect'
+      end
+
       context 'with a tampered HOST header' do
         before do
           request.headers['HOST'] = 'http://this.is.not.my.host'

spec/support/helpers/stub_configuration.rb

@@ -33,8 +33,8 @@ module StubConfiguration
     allow(Gitlab.config).to receive_messages(to_settings(messages))
   end
 
-  def stub_default_url_options(host: "localhost", protocol: "http")
-    url_options = { host: host, protocol: protocol }
+  def stub_default_url_options(host: "localhost", protocol: "http", script_name: nil)
+    url_options = { host: host, protocol: protocol, script_name: script_name }
     allow(Rails.application.routes).to receive(:default_url_options).and_return(url_options)
   end