Reuses `InternalRedirect` when possible

`InternalRedirect` prevents Open redirect issues by only allowing
redirection to paths on the same host.

It cleans up any unwanted strings from the path that could point to
another host (fe. //about.gitlab.com/hello). While preserving the
querystring and fragment of the uri.

It is already used by:

- `TermsController`
- `ContinueParams`
  - `ImportsController`
  - `ForksController`
- `SessionsController`: Only for verifying the host in CE. EE allows
   redirecting to a different instance using Geo.

2 files changed, 4 insertions, 9 deletions

diff --git a/app/controllers/concerns/continue_params.rb b/app/controllers/concerns/continue_params.rb
index eb3a623acdd..8b7355974df 100644
--- a/app/controllers/concerns/continue_params.rb
+++ b/app/controllers/concerns/continue_params.rb
@@ -1,4 +1,5 @@
 module ContinueParams
+  include InternalRedirect
   extend ActiveSupport::Concern
 
   def continue_params
@@ -6,8 +7,7 @@ module ContinueParams
     return nil unless continue_params
 
     continue_params = continue_params.permit(:to, :notice, :notice_now)
-    return unless continue_params[:to] && continue_params[:to].start_with?('/')
-    return if continue_params[:to].start_with?('//')
+    continue_params[:to] = safe_redirect_path(continue_params[:to])
 
     continue_params
   end
diff --git a/app/controllers/sessions_controller.rb b/app/controllers/sessions_controller.rb
index f3a4aa849c7..1a339f76d26 100644
--- a/app/controllers/sessions_controller.rb
+++ b/app/controllers/sessions_controller.rb
@@ -1,4 +1,5 @@
 class SessionsController < Devise::SessionsController
+  include InternalRedirect
   include AuthenticatesWithTwoFactor
   include Devise::Controllers::Rememberable
   include Recaptcha::ClientHelper
@@ -102,18 +103,12 @@ class SessionsController < Devise::SessionsController
     # we should never redirect to '/users/sign_in' after signing in successfully.
     return true if redirect_uri.path == new_user_session_path
 
-    redirect_to = redirect_uri.to_s if redirect_allowed_to?(redirect_uri)
+    redirect_to = redirect_uri.to_s if host_allowed?(redirect_uri)
 
     @redirect_to = redirect_to
     store_location_for(:redirect, redirect_to)
   end
 
-  # Overridden in EE
-  def redirect_allowed_to?(uri)
-    uri.host == Gitlab.config.gitlab.host &&
-      uri.port == Gitlab.config.gitlab.port
-  end
-
   def two_factor_enabled?
     find_user&.two_factor_enabled?
   end