pam-naming is a pam module that allows you to match usernames against Perl regular expressions using the pcre library. This can be helpful if you want to ensure that usernames are e.g. all lowercase although pam_ldap would accept uppercase usernames (due to the used ldap schema on the server).
The source code is available via:
git clone https://git.sigxcpu.org/cgit/pam-naming
and can be browsed here.
pam-naming was written by Guido Günther <firstname.lastname@example.org>.