Comment 0 for bug 951343

Linux clients that use ldap authentication with nslcd and a long pam_authz_search filter will see authentication fail silently

reproduction steps:

modify entry for 127.0.1.1 in /etc/hosts so the example.com dc is used by slapd
EX:
x.x.x.x server1
change to:
x.x.x.x server1.example.com server1

apt-get install nslcd # set search base "dc=example,dc=com". then select all for services use ldap lookups when configuring libnss-ldapd.
apt-get install slapd
dpkg-reconfigure slapd # dns name "example.com"
apt-get install migrationtools

turn on ldap authentication using pam-auth-update

stop nslcd and slapd. We'll start them in debug mode

/etc/init.d/nslcd stop
/etc/init.d/slapd stop

migrate users to ldap. edit /etc/migrationtools/migrate_common.ph and change:
$DEFAULT_MAIL_DOMAIN = "example.com";
$DEFAULT_BASE = "dc=example,dc=com";

then run commands to create ldif exports of group and passwd
/usr/share/migrationtools/migrate_group.pl /etc/group ~/group.ldif
/usr/share/migrationtools/migrate_passwd.pl /etc/passwd ~/passwd.ldif

edit ~/people_group.ldif adding contents:
dn: ou=People, dc=example, dc=com
ou: People
objectclass: organizationalUnit

dn: ou=Group, dc=example, dc=com
ou: Group
objectclass: organizationalUnit

import data into ldap:
ldapadd -x -W -D "cn=admin,dc=example,dc=com" -f ~/people_group.ldif
ldapadd -x -W -D "cn=admin,dc=example,dc=com" -f ~/group.ldif
ldapadd -x -W -D "cn=admin,dc=example,dc=com" -f ~/passwd.ldif

edit /etc/nslcd.conf adding pam_authz_search filter
pam_authz_search (&(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount)(objectClass=posixAccount))

open 2 new terminals and become root

in one terminal run nslcd in debug mode:
nslcd -d

in second terminal run slapd in debug mode:
slapd -d -1

in your original terminal attempt to sudo to a user other than root and watch the debug output in the slapd and nslcd terminals:

sudo su ubuntu

look for output in nslcd terminal "DEBUG: trying pam_authz_search" in nslcd terminal indicating filter is being used

increase search string beyond 1024 buffer and note that we're no longer seeing "Trying pam_authz_search" in the nslcd output and that authentication fails silently