Remote Auth does not sanitize usernames

[D3luxee]

NetBox version

v3.2.2

Python version

3.10

Steps to Reproduce

1. Setup netbox with remote auth based on netbox.authentication.RemoteUserBackend / Header
2. Auto Create User must be enabled, see configuration example below
3. Now open netbox and set the define AUTH_HEADER to a username that contains invalid characters like : which is used for example by Google IAP
4. This creates a new user in netbox, now open the admin interface of netbox and try to change anything in the user (/admin/auth/user/)
5. The user edit dialog validates the username if you change something, the frontend does not allow saving any changes there because of an invalid character in the username.

REMOTE_AUTH_ENABLED: true
REMOTE_AUTH_BACKEND: "netbox.authentication.RemoteUserBackend"
REMOTE_AUTH_HEADER: "HTTP_X_GOOG_AUTHENTICATED_USER_EMAIL"
REMOTE_AUTH_AUTO_CREATE_USER: true                                                                                                                                                                                                                                                                                                                                                 

Expected Behavior

Netbox should sanitize the usernames that are provided via REMOTE_AUTH_HEADER to create valid usernames.

Observed Behavior

Google IAPs headers have a value of: accounts.google.com:example@gmail.com and it creates a new user based on this in netbox.
But the admin dialogs to change or update those user accounts validates the username and rejects any changes because of invalid characters in the username:

Enter a valid username. This value may contain only letters, numbers, and @/./+/-/_ characters.

[jeremystretch]

Thank you for opening a bug report. Unfortunately, the information you have provided is not sufficient for someone else to attempt to reproduce the reported behavior. Remember, each bug report must include detailed steps that someone else can follow on a clean, empty NetBox installation to reproduce the exact problem you're experiencing. These instructions should include the creation of any involved objects, any configuration changes, and complete accounting of the actions being taken. Also be sure that your report does not reference data on the public NetBox demo, as that is subject to change at any time by an outside party and cannot be relied upon for bug reports.

[D3luxee]

Hi @jeremystretch
i updated the steps to reproduce, bascially the issue is that the remote auth based on the header is able to create users with usernames that are not possible to create via the frontend and therefor youre not able to edit those users via the admin ui.

[github-actions]

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