Your software
My Mautic version is: v2.15.3
My PHP version is: 7.0.33-0ubuntu0.16.04.7
Your problem
My problem is: SSO stoped working. This has happened before where mautic redirects to the login page and fails to authenticate on submit. Previous way to resolve this was to update the SSO settings. In the current version of Mautic this is not possible as updating the FederationMetadata.xml results in a 500 Internal Server Error, when saving the settings.
These errors are showing in the log:
[2019-12-18 14:58:16] mautic.CRITICAL: Uncaught PHP Exception Exception: "Serialization of 'Symfony\Component\HttpFoundation\File\UploadedFile' is not allowed" at /srv/example.com/html/app/bundles/CoreBundle/Doctrine/Type/ArrayType.php line 43 {"exception":"[object] (Exception(code: 0): Serialization of 'Symfony\\Component\\HttpFoundation\\File\\UploadedFile' is not allowed at /srv/example.com/html/app/bundles/CoreBundle/Doctrine/Type/ArrayType.php:43)"} []
Steps I have tried to fix the problem:
Tried clearing cache
Deleting the setting, save, re-edit page with new setting - saving fails.
Maybe if you can try to apply this PR, and see if it fixes the problem? If so, please report it as a successful test by going to the PR, clicking on ‘files changed’, click ‘review changes’, add a comment and select approve changes.
Some weeks back, we experienced the same issue as the OP while integrating Mautic with SAASPASS for 2FA. Using the pull request you linked above @rcheesley we were able to work around the issue and successfully connect Mautic with the SAML provider, and redirect the login page to the SSO challenge.