Backport InternalRedirect#sanitize_redirect

app/controllers/concerns/internal_redirect.rb

@@ -23,6 +23,10 @@ module InternalRedirect
     nil
   end
 
+  def sanitize_redirect(url_or_path)
+    safe_redirect_path(url_or_path) || safe_redirect_path_for_url(url_or_path)
+  end
+
   def host_allowed?(uri)
     uri.host == request.host &&
       uri.port == request.port

spec/controllers/concerns/internal_redirect_spec.rb

@@ -54,6 +54,31 @@ describe InternalRedirect do
     end
   end
 
+  describe '#sanitize_redirect' do
+    let(:valid_path) { '/hello/world?hello=world' }
+    let(:valid_url) { "http://test.host#{valid_path}" }
+
+    it 'returns `nil` for invalid paths' do
+      invalid_path = '//not/valid'
+
+      expect(controller.sanitize_redirect(invalid_path)).to eq nil
+    end
+
+    it 'returns `nil` for invalid urls' do
+      input = 'http://test.host:3000/invalid'
+
+      expect(controller.sanitize_redirect(input)).to eq nil
+    end
+
+    it 'returns input for valid paths' do
+      expect(controller.sanitize_redirect(valid_path)).to eq valid_path
+    end
+
+    it 'returns path for valid urls' do
+      expect(controller.sanitize_redirect(valid_url)).to eq valid_path
+    end
+  end
+
   describe '#host_allowed?' do
     it 'allows uris with the same host and port' do
       expect(controller.host_allowed?(URI('http://test.host/test'))).to be(true)