$ cat /etc/pam.d/proftpd
#%PAM-1.0
auth required pam_listfile.so item=user sense=deny file=/etc/ftpusers onerr=succeed
auth required pam_stack.so service=system-auth
auth required pam_shells.so
account required pam_stack.so service=system-auth
session required pam_stack.so service=system-auth

$ grep ldap /etc/pam.d/system-auth
auth sufficient /lib/security/$ISA/pam_ldap.so use_first_pass
account [default=bad success=ok user_unknown=ignore] /lib/security/$ISA/pam_ldap.so
password sufficient /lib/security/$ISA/pam_ldap.so use_authtok
session optional /lib/security/$ISA/pam_ldap.so