Merge branch 'security-dos-issue-and-commit-comments-12-3' into '12-3-stable'

Fix invalid byte sequence

See merge request gitlab/gitlabhq!3549

changelogs/unreleased/security-dos-issue-and-commit-comments-master.yml

+---
+title: Fix 500 error caused by invalid byte sequences in links
+merge_request:
+author:
+type: security

lib/banzai/filter/relative_link_filter.rb

@@ -103,7 +103,7 @@ module Banzai
       end
       def relative_file_path(uri)
-        path = Addressable::URI.unescape(uri.path).delete("\0")
+        path = Addressable::URI.unescape(uri.path).scrub.delete("\0")
         request_path = Addressable::URI.unescape(context[:requested_path])
         nested_path = build_relative_path(path, request_path)
         file_exists?(nested_path) ? nested_path : path

spec/lib/banzai/filter/relative_link_filter_spec.rb

@@ -87,6 +87,11 @@ describe Banzai::Filter::RelativeLinkFilter do
     expect { filter(act) }.not_to raise_error
   end
+  it 'does not raise an exception on URIs containing invalid utf-8 byte sequences' do
+    act = link("%FF")
+    expect { filter(act) }.not_to raise_error
+  end
+
   it 'does not raise an exception with a garbled path' do
     act = link("open(/var/tmp/):%20/location%0Afrom:%20/test")
     expect { filter(act) }.not_to raise_error