OpenID Connect Client returns 'Not Found' for private files created via the Webform module (and other modules).

Problem/Motivation

OpenID Connect Client returns 'Not Found' for private files created via the Webform module (and other modules).

Steps to reproduce

• Create a plain vanilla Drupal site. ddev drush site-install;
• Enable private file access. Add $settings['file_private_path'] = 'sites/default/files/private'; to settings.php
• Install the Webform module ddev composer require 'drupal/webform:^6.3@beta'; ddev drush en -y webform webform_ui;
• Create a webform with a file upload.
  

  </code></li>
    <li>Upload a file, goto to the webform's results and confirm you can access the private file.</li>
    <li>Install the oidc module. <code>ddev drush en -y oidc;</cpde></li>
    <li>Confirm that the private file  now returns 'Not Found'</li>
  </ul>
  
  <h3 id="summary-proposed-resolution">Proposed resolution</h3>
  
  The issue is that \Drupal\oidc\EventSubscriber\RequestSubscriber::getRouteMatch is calling <code>$this->requestMatcher->matchRequest($request)

  which sets the 'file' query parameters but does update the request path. When route is finally processed, \Drupal\system\PathProcessor\PathProcessorFiles::processInbound does NOT alter the $path as expected.

  The Redirect module ran into a similar issue via #2985288: Cannot redirect from a private file path. We should follow their approach and handle specific requests system/files.

  Remaining tasks

  • Replicate the issue
  • Review the patch
  • Write tests if needed
  • Commit the patch

  User interface changes

  N/A

  API changes

  Private files won't be able to redirect users to login.

  Data model changes

  N/A