Merge branch 'fix/token-timing-attack' into 'master'

fix token issue - timing attack

Updates token comparisons to use a secure version instead of `==`

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/13617

See merge request !3062

app/models/project.rb

@@ -930,13 +930,13 @@ class Project < ActiveRecord::Base
   end
 
   def valid_runners_token? token
-    self.runners_token && self.runners_token == token
+    self.runners_token && ActiveSupport::SecurityUtils.variable_size_secure_compare(token, self.runners_token)
   end
 
   # TODO (ayufan): For now we use runners_token (backward compatibility)
   # In 8.4 every build will have its own individual token valid for time of build
   def valid_build_token? token
-    self.builds_enabled? && self.runners_token && self.runners_token == token
+    self.builds_enabled? && self.runners_token && ActiveSupport::SecurityUtils.variable_size_secure_compare(token, self.runners_token)
   end
 
   def build_coverage_enabled?

app/models/project_services/ci_service.rb

@@ -26,7 +26,7 @@ class CiService < Service
   default_value_for :category, 'ci'
 
   def valid_token?(token)
-    self.respond_to?(:token) && self.token.present? && self.token == token
+    self.respond_to?(:token) && self.token.present? && ActiveSupport::SecurityUtils.variable_size_secure_compare(token, self.token)
   end
 
   def supported_events