prevent decrypt error and recover access_token correctly

app/controllers/oauth/geo_auth_controller.rb

@@ -35,7 +35,10 @@ class Oauth::GeoAuthController < ActionController::Base
 
   def logout
     oauth = Gitlab::Geo::OauthSession.new(state: params[:state])
-    access_token = oauth.extract_logout_token
+    token_string = oauth.extract_logout_token
+
+    access_token_error('invalid') unless token_string.is_utf8?
+    access_token = Doorkeeper::AccessToken.by_token(token_string)
     access_token_status = Oauth2::AccessTokenValidationService.validate(access_token)
 
     if access_token_status == Oauth2::AccessTokenValidationService::VALID

lib/gitlab/geo/oauth_session.rb

@@ -66,7 +66,8 @@ module Gitlab
         cipher = OpenSSL::Cipher::AES.new(128, :CBC)
         cipher.send(operation)
         cipher.iv = salt
-        cipher.key = Gitlab::Application.secrets.secret_key_base
+        cipher.key = Gitlab::Application.secrets.db_key_base
+        cipher.auth_data = ''
         cipher
       end