NEMO User (null) with SSO issue

[Hydrozyk]

Hi all,

Was wondering if there are any information on why NEMO-ce and authenticating via Okta SSO is throwing User (null) attempted to authenticate with RemoteUserAuthenticationBackend error? Most users are fine but for some it shows that error. Verified that users do exist in NEMO Db and are active

settings.py
AUTHENTICATION_BACKENDS = ['NEMO.views.authentication.RemoteUserAuthenticationBackend',]

Error log:

Backend, but that username does not exist in the database. The user was denied access.
[27/Jan/2025 14:27:23] NEMO.views.authentication WARNING User (null) attempted to authenticate with RemoteUserAuthenticationBackend, but that username does not exist in the database. The user was denied access.
[27/Jan/2025 14:27:29] NEMO.views.authentication WARNING User (null) attempted to authenticate with RemoteUserAuthenticationBackend, but that username does not exist in the database. The user was denied access.

[rptmat57]

Not quite sure, it might have to do with how you are sending that remote_user variable to NEMO and the OKTA/SAML configuration

[Hydrozyk]

We are using Shibboleth with Apache server and it works just fine. In Apache the logs I see the remote_user var propagating and NEMO is picking it then authenticates. We have 170 users and and it only happens with 2-3 users for some reason. I wonder why it shows as User (null)?

[rptmat57]

what's odd is that the log line in NEMO's code is:
User {username} attempted to authenticate with {type(backend).__name__}, but that username does not exist in the database. The user was denied access.

Which means the username sent to NEMO is (null), including the parentheses. NEMO being written in python, null doesn't exists, it's None in python, which leads me to think something else is setting this username before it gets to NEMO