Right now, only a small number of possible error cases is rescue inside the AuthSourceLdap model are rescued, namely errors happening on the LDAP protocol itself. This results in plain (and not really helpful) 500 errors on login for many common transient network errors, including an unstable connection between the app and the LDAP server, TLS certificate issues, DNS issues, changed firewalls...

The attached patch against current trunk at r14793 provides a list of exceptions that are explicitly rescued to show a nice error message to the user instead of just failing with an HTTP 500. This should result in much more pleasant experience for people using LDAP auth.

This patch was extracted from "Planio":https://plan.io/redmine-hosting.