[Bug]: Theming is not applied on SSO user disabled error page

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

In NC27 with activated theming app and custom logo and backgroud I am getting the default theming if a saml user is deactivated and tries to login.

Steps to reproduce

1. Have SAML enabled and configured
2. Have the user already known in Nextcloud
3. Disable the user in Nextcloud
4. Login as this user per SAML
5. bam!

Analysis:

In base.php handleLogin() is called, and inside there OC_User::handleApacheAuth() is called. Which again calls its own method loginWithApache(). There we have a check whether the user is enabled: if ($userSession->getUser() && !$userSession->getUser()->isEnabled()) {

In our case they are not enable and so a LoginException is thrown with the translated message "User disabled".

This then is only caught in index.php where it prints the error page. OC_Template::printErrorPage() is utilized. It actually would load theming, if it is not already, provided it is enabled for the user! But without a user – login refused - this check returns false and so we have not theming in that case.

Expected behavior

Theming applies

Installation method

None

Nextcloud Server version

27

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start with base.php and follow handleLogin() through OC_User::handleApacheAuth() and loginWithApache(), then inspect the exception handling in index.php and OC_Template::printErrorPage(). Reproduce the disabled SSO-user login case and verify that the configured theming is applied to the resulting User disabled error page.