Two things:
First, documentation for /auth/multiple should be updated so that the auth.ini file is like the following:
ldap_search_attr[] = sn
ldap_search_attr[] = givenname
ldap_search_attr[] = mail
I initially went
ldap_search_attr[] = sn,givenname,mail
which didn't load them into an array as it should've.
I also added two new properties
ldap_bind_as_user = true
ldap_bind_as_user_usernamedomain = "@cgustudent.cgu.edu"
and the code in auth/ldap/lib.php so that it can try logging into ldap as the current user instead of having hardcoded information. lib.php is attached, with my modified sections clearly marked (lines 78-87, 234-239)