Closes #15811: Note potential incompatibilities for remote auth heade…

…rs containing underscores

contrib/gunicorn.py

@@ -14,3 +14,7 @@
 # The maximum number of requests a worker can handle before being respawned
 max_requests = 5000
 max_requests_jitter = 500
+
+# Uncomment this line to accept HTTP headers containing underscores, e.g. for remote
+# authentication support. See https://docs.gunicorn.org/en/stable/settings.html#header-map
+# header-map = 'dangerous'

docs/administration/authentication/overview.md

@@ -26,7 +26,10 @@ REMOTE_AUTH_BACKEND = 'netbox.authentication.RemoteUserBackend'
 
 Another option for remote authentication in NetBox is to enable HTTP header-based user assignment. The front end HTTP server (e.g. nginx or Apache) performs client authentication as a process external to NetBox, and passes information about the authenticated user via HTTP headers. By default, the user is assigned via the `REMOTE_USER` header, but this can be customized via the `REMOTE_AUTH_HEADER` configuration parameter.
 
-Optionally, user profile information can be supplied by `REMOTE_USER_FIRST_NAME`, `REMOTE_USER_LAST_NAME` and `REMOTE_USER_EMAIL` headers. These are saved to the users profile during the authentication process. These headers can be customized like the `REMOTE_USER` header.
+Optionally, user profile information can be supplied by `REMOTE_USER_FIRST_NAME`, `REMOTE_USER_LAST_NAME` and `REMOTE_USER_EMAIL` headers. These are saved to the user's profile during the authentication process. These headers can be customized like the `REMOTE_USER` header.
+
+!!! warning Verify Header Compatibility
+    Some WSGI servers may drop headers which contain unsupported characters. For instance, gunicorn v22.0 and later silently drops HTTP headers containing underscores. This behavior can be disabled by changing gunicorn's [`header_map`](https://docs.gunicorn.org/en/stable/settings.html#header-map) setting to `dangerous`.
 
 ### Single Sign-On (SSO)
 

docs/configuration/remote-authentication.md

@@ -85,6 +85,9 @@ Default: `'HTTP_REMOTE_USER'`
 
 When remote user authentication is in use, this is the name of the HTTP header which informs NetBox of the currently authenticated user. For example, to use the request header `X-Remote-User` it needs to be set to `HTTP_X_REMOTE_USER`. (Requires `REMOTE_AUTH_ENABLED`.)
 
+!!! warning Verify Header Compatibility
+    Some WSGI servers may drop headers which contain unsupported characters. For instance, gunicorn v22.0 and later silently drops HTTP headers containing underscores. This behavior can be disabled by changing gunicorn's [`header_map`](https://docs.gunicorn.org/en/stable/settings.html#header-map) setting to `dangerous`.
+
 ---
 
 ## REMOTE_AUTH_USER_EMAIL