PAM / LDAP authentication with Ubuntu 10.04

Question

I can't wrap my brain around the new pam.d configuration syntax used in Ubuntu 10.04. How do I setup PAM so that it allows users stored in my LDAP database to login.

I already configured nscd, so id <user> or getent passwd are already listing my LDAP users, but PAM doesn't work, whether the normal shell login nor su.

Update June, 17th 2010 18:45

LDAP is already working. I can list all accounts by executing getent passwd, but my PAM configuration is still not working.

The listing below shows my /etc/pam.d/login

#
# The PAM configuration file for the Shadow `login' service
#

# Enforce a minimal delay in case of failure (in microseconds).
# (Replaces the `FAIL_DELAY' setting from login.defs)
# Note that other modules may require another minimal delay. (for example,
# to disable any delay, you should add the nodelay option to pam_unix)
auth       optional   pam_faildelay.so  delay=3000000

# Outputs an issue file prior to each login prompt (Replaces the
# ISSUE_FILE option from login.defs). Uncomment for use
# auth       required   pam_issue.so issue=/etc/issue

# Disallows root logins except on tty's listed in /etc/securetty
# (Replaces the `CONSOLE' setting from login.defs)
# Note that it is included as a "required" module. root will be
# prompted for a password on insecure ttys.
# If you change it to a "requisite" module, make sure this does not leak
# user name information.
auth       required  pam_securetty.so

# Disallows other than root logins when /etc/nologin exists
# (Replaces the `NOLOGINS_FILE' option from login.defs)
auth       requisite  pam_nologin.so

# SELinux needs to be the first session rule. This ensures that any 
# lingering context has been cleared. Without out this it is possible 
# that a module could execute code in the wrong domain.
# When the module is present, "required" would be sufficient (When SELinux
# is disabled, this returns success.)
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so close

# This module parses environment configuration file(s)
# and also allows you to use an extended config
# file /etc/security/pam_env.conf.
# 
# parsing /etc/environment needs "readenv=1"
session       required   pam_env.so readenv=1
# locale variables are also kept into /etc/default/locale in etch
# reading this file *in addition to /etc/environment* does not hurt
session       required   pam_env.so readenv=1 envfile=/etc/default/locale

# Standard Un*x authentication.
@include common-auth

# This allows certain extra groups to be granted to a user
# based on things like time of day, tty, service, and user.
# Please edit /etc/security/group.conf to fit your needs
# (Replaces the `CONSOLE_GROUPS' option in login.defs)
auth       optional   pam_group.so

# Uncomment and edit /etc/security/time.conf if you need to set
# time restrainst on logins.
# (Replaces the `PORTTIME_CHECKS_ENAB' option from login.defs
# as well as /etc/porttime)
# account    requisite  pam_time.so

# Uncomment and edit /etc/security/access.conf if you need to
# set access limits.
# (Replaces /etc/login.access file)
# account  required       pam_access.so

# Sets up user limits according to /etc/security/limits.conf
# (Replaces the use of /etc/limits in old login)
session    required   pam_limits.so

# Prints the last login info upon succesful login
# (Replaces the `LASTLOG_ENAB' option from login.defs)
session    optional   pam_lastlog.so

# Prints the motd upon succesful login
# (Replaces the `MOTD_FILE' option in login.defs)
session    optional   pam_motd.so

# Prints the status of the user's mailbox upon succesful login
# (Replaces the `MAIL_CHECK_ENAB' option from login.defs). 
#
# This also defines the MAIL environment variable
# However, userdel also needs MAIL_DIR and MAIL_FILE variables
# in /etc/login.defs to make sure that removing a user 
# also removes the user's mail spool file.
# See comments in /etc/login.defs
session    optional   pam_mail.so standard

# Standard Un*x account and session
@include common-account
@include common-session
@include common-password

# SELinux needs to intervene at login time to ensure that the process
# starts in the proper default security context. Only sessions which are
# intended to run in the user's context should be run after this.
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so open
# When the module is present, "required" would be sufficient (When SELinux
# is disabled, this returns success.)

The listing below shows my /etc/pam.d/common-auth

#
# /etc/pam.d/common-auth - authentication settings common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of the authentication modules that define
# the central authentication scheme for use on the system
# (e.g., /etc/shadow, LDAP, Kerberos, etc.).  The default is to use the
# traditional Unix authentication mechanisms.
#
# As of pam 1.0.1-6, this file is managed by pam-auth-update by default.
# To take advantage of this, it is recommended that you configure any
# local modules either before or after the default block, and use
# pam-auth-update to manage selection of other modules.  See
# pam-auth-update(8) for details.

# here are the per-package modules (the "Primary" block)
auth    [success=2 default=ignore]  pam_unix.so nullok_secure
auth    [success=1 default=ignore]  pam_ldap.so use_first_pass
# here's the fallback if no module succeeds
auth    requisite           pam_deny.so
# prime the stack with a positive return value if there isn't one already;
# this avoids us returning an error just because nothing sets a success code
# since the modules above will each just jump around
auth    required            pam_permit.so
# and here are more per-package modules (the "Additional" block)
# end of pam-auth-update config

Solution 1

Restore you pam files to the original versions. Install the libnss-ldap package which will integrate ldap access into pam. You may also want to install nscd.

Configure your server in /etc/ldap.conf.

Edit /etc/nsswitch.conf adding ldap to the end of the lines for passwd group and shadow.

passwd:         compat ldap
group:          compat ldap
shadow:         compat ldap 

Check to see if 'sudo getent shadow' is working for ldap entries. Check that you can get an authenticated connection using ldap-search from ldap-utils using your /etc/ldap.conf connection data.

Depending on your configuration you will also have to configure ssl values in /etc/ldap.conf.

Solution 2

• Firstly, you'll need to open up your favourite package manager and install libpam-ldap
  • Once the packages start being unpacked you'll be hit up for a few questions about:
    . IP address/hostname of the LDAP server
    . The search base of your LDAP domain etc...
  • Now you need to customise PAM to make it use LDAP for authentication:
    sudo vi /etc/pam.d/login
  • you need to add one line above the existing line:
    

auth sufficient pam_ldap.so
auth required pam_unix.so try_first_pass

Or modified the common-auth file

Comments

[Shtééf]

Your common-auth looks correct. Perhaps the problem is somewhere else? Is there anything in /var/log/auth.log? Check some other logs too, such as syslog, messages, user.log and daemon.log. Are there any other LDAP-related files you've edited? Did you configure any authentication or access control on the LDAP server?

[t6d]

I guess I messed up my configuration. I tried again by installing the packages and configuring /etc/nsswitch.conf, and see, it works! Great, thanks a lot.