Difference between revisions of "LDAP authentication"
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| − | [[Category:Networking]] [[Category:Security]] | + | [[Category:Networking]] |
| + | [[Category:Security]] | ||
| + | {{Related articles start}} | ||
| + | {{Related|OpenLDAP}} | ||
| + | {{Related|LDAP Hosts}} | ||
| + | {{Related articles end}} | ||
| + | |||
== Introduction and Concepts == | == Introduction and Concepts == | ||
This is a guide on how to configure an Arch Linux installation to authenticate against an LDAP directory. This LDAP directory can be either local (installed on the same computer) or network (e.g. in a lab environment where central authentication is desired). | This is a guide on how to configure an Arch Linux installation to authenticate against an LDAP directory. This LDAP directory can be either local (installed on the same computer) or network (e.g. in a lab environment where central authentication is desired). | ||
| − | The guide | + | The guide is divided into two parts. The first part deals with how to setup an [[OpenLDAP]] server that hosts the authentication directory. The second part deals with how to setup the NSS and PAM modules that are required for the authentication scheme to work on the client computers. If you just want to configure Arch to authenticate against an already existing LDAP server, you can skip to the second part. |
=== NSS and PAM === | === NSS and PAM === | ||
| Line 18: | Line 24: | ||
You can read about installation and basic configuration in the [[OpenLDAP]] article. After you have completed that, return here. | You can read about installation and basic configuration in the [[OpenLDAP]] article. After you have completed that, return here. | ||
| + | |||
| + | === Set up access controls === | ||
| + | |||
| + | To make sure that no-one can read the (encrypted) passwords from the LDAP server, but a user can edit their own password, add the following to {{ic|/etc/openldap/slapd.conf}} and restart {{ic|slapd.service}} afterwards: | ||
| + | |||
| + | {{hc|slapd.conf|2= | ||
| + | access to attrs=userPassword | ||
| + | by self write | ||
| + | by anonymous auth | ||
| + | by * none | ||
| + | |||
| + | access to * | ||
| + | by self write | ||
| + | by * read | ||
| + | }} | ||
=== Populate LDAP Tree with Base Data === | === Populate LDAP Tree with Base Data === | ||
| − | Create a file called {{ic|base.ldif}} with the following text | + | Create a temporarily file called {{ic|base.ldif}} with the following text. |
| + | {{note|If you have a different domain name then alter "example" and "org" to your needs}} | ||
{{hc|base.ldif|<nowiki> | {{hc|base.ldif|<nowiki> | ||
# example.org | # example.org | ||
dn: dc=example,dc=org | dn: dc=example,dc=org | ||
| + | dc: example | ||
| + | o: Example Organization | ||
objectClass: dcObject | objectClass: dcObject | ||
objectClass: organization | objectClass: organization | ||
| − | |||
| − | |||
# Manager, example.org | # Manager, example.org | ||
| Line 35: | Line 57: | ||
cn: Manager | cn: Manager | ||
description: LDAP administrator | description: LDAP administrator | ||
| − | |||
objectClass: organizationalRole | objectClass: organizationalRole | ||
objectClass: top | objectClass: top | ||
| + | roleOccupant: dc=example,dc=org | ||
# People, example.org | # People, example.org | ||
| Line 45: | Line 67: | ||
objectClass: organizationalUnit | objectClass: organizationalUnit | ||
| − | # | + | # Groups, example.org |
| − | dn: ou= | + | dn: ou=Groups,dc=example,dc=org |
| − | ou: | + | ou: Groups |
objectClass: top | objectClass: top | ||
objectClass: organizationalUnit | objectClass: organizationalUnit | ||
| Line 62: | Line 84: | ||
=== Adding users === | === Adding users === | ||
To manually add a user, create an {{ic|.ldif}} file like this: | To manually add a user, create an {{ic|.ldif}} file like this: | ||
| − | {{hc| | + | {{hc|user_joe.ldif|<nowiki> |
dn: uid=johndoe,ou=People,dc=example,dc=org | dn: uid=johndoe,ou=People,dc=example,dc=org | ||
objectClass: top | objectClass: top | ||
| Line 87: | Line 109: | ||
</nowiki>}} | </nowiki>}} | ||
| − | + | The {{ic|xxxxxxxxxx}} in the {{ic|userPassword}} entry should be replaced with the value in {{ic|/etc/shadow}} or use the {{ic|slappasswd}} command. Now add the user: | |
| − | You can automatically migrate all of your local accounts (and groups, etc.) to the LDAP directory using PADL Software's [http://www.padl.com/OSS/MigrationTools.html Migration Tools]. | + | $ ldapadd -D "cn=Manager,dc=example,dc=org" -W -f user_joe.ldif |
| + | |||
| + | {{Note|You can automatically migrate all of your local accounts (and groups, etc.) to the LDAP directory using PADL Software's [http://www.padl.com/OSS/MigrationTools.html Migration Tools].}} | ||
== Client Setup == | == Client Setup == | ||
| Line 108: | Line 132: | ||
Edit {{ic|/etc/nslcd.conf}} and change the {{ic|base}} and {{ic|uri}} lines to fit your ldap server setup. | Edit {{ic|/etc/nslcd.conf}} and change the {{ic|base}} and {{ic|uri}} lines to fit your ldap server setup. | ||
| − | + | Start {{ic|nslcd.service}} using systemd. | |
You now should see your LDAP users when running {{ic|getent passwd}} on the client. | You now should see your LDAP users when running {{ic|getent passwd}} on the client. | ||
| Line 124: | Line 148: | ||
{{Tip|If you want to prevent UID clashes with local users on your system, you might want to include {{ic|minimum_uid=10000}} or similar on the end of the {{ic|pam_ldap.so}} lines. You'll have to make sure the LDAP server returns uidNumber fields that match the restriction.}} | {{Tip|If you want to prevent UID clashes with local users on your system, you might want to include {{ic|minimum_uid=10000}} or similar on the end of the {{ic|pam_ldap.so}} lines. You'll have to make sure the LDAP server returns uidNumber fields that match the restriction.}} | ||
| − | {{Note|Each facility (auth, session, password, account) forms a separate chain and the order matters. | + | {{Note|Each facility (auth, session, password, account) forms a separate chain and the order matters. Sufficient lines will sometimes "short circuit" and skip the rest of the section, so the rule of thumb for ''auth'', ''password'', and ''account'' is ''sufficient'' lines before ''required'', but after required lines for the ''session'' section; ''optional'' can almost always go at the end. When adding your {{ic|pam_ldap.so}} lines, don't change the relative order of the other lines without good reason! Simply insert LDAP within the chain.}} |
First edit {{ic|/etc/pam.d/system-auth}}. This file is included in most of the other files in {{ic|pam.d}}, so changes here propagate nicely. Updates to {{pkg|pambase}} may change this file. | First edit {{ic|/etc/pam.d/system-auth}}. This file is included in most of the other files in {{ic|pam.d}}, so changes here propagate nicely. Updates to {{pkg|pambase}} may change this file. | ||
| Line 168: | Line 192: | ||
}} | }} | ||
| − | To enable | + | To enable users to edit their password, edit {{ic|/etc/pam.d/passwd}}: |
| − | {{hc|/etc/pam.d/ | + | |
| + | {{hc|/etc/pam.d/passwd|2= | ||
#%PAM-1.0 | #%PAM-1.0 | ||
| − | ''' | + | '''password sufficient pam_ldap.so''' |
| − | + | #password required pam_cracklib.so difok=2 minlen=8 dcredit=2 ocredit=2 retry=3 | |
| − | + | #password required pam_unix.so sha512 shadow use_authtok | |
| + | password required pam_unix.so sha512 shadow nullok | ||
}} | }} | ||
| − | If you want home folders to be created at login (eg: if you aren't using NFS to store home folders), edit {{ic|/etc/pam.d/system-login}} and {{ic| | + | ==== Create home folders at login ==== |
| + | |||
| + | If you want home folders to be created at login (eg: if you aren't using NFS to store home folders), edit {{ic|/etc/pam.d/system-login}} and add {{ic|pam_mkhomedir.so}} to the ''session'' section above any "sufficient" items. This will cause home folder creation when logging in at a tty, from ssh, xdm, kdm, gdm, etc. You might choose to edit additional files in the same way, such as {{ic|/etc/pam.d/su}} and {{ic|/etc/pam.d/su-l}} to enable it for {{ic|su}} and {{ic|su --login}}. If you don't want to do this for ssh logins, edit {{ic|system-local-login}} instead of {{ic|system-login}}, etc. | ||
{{hc|/etc/pam.d/system-login| | {{hc|/etc/pam.d/system-login| | ||
| Line 194: | Line 222: | ||
session sufficient pam_ldap.so | session sufficient pam_ldap.so | ||
session required pam_unix.so | session required pam_unix.so | ||
| + | }} | ||
| + | |||
| + | ==== Enable sudo ==== | ||
| + | |||
| + | To enable sudo from an LDAP user, edit {{ic|/etc/pam.d/sudo}}. You'll also need to modify sudoers accordingly. | ||
| + | {{hc|/etc/pam.d/sudo| | ||
| + | #%PAM-1.0 | ||
| + | '''auth sufficient pam_ldap.so''' | ||
| + | auth required pam_unix.so '''try_first_pass''' | ||
| + | auth required pam_nologin.so | ||
}} | }} | ||
Revision as of 22:09, 12 January 2014
Related articles
Introduction and Concepts
This is a guide on how to configure an Arch Linux installation to authenticate against an LDAP directory. This LDAP directory can be either local (installed on the same computer) or network (e.g. in a lab environment where central authentication is desired).
The guide is divided into two parts. The first part deals with how to setup an OpenLDAP server that hosts the authentication directory. The second part deals with how to setup the NSS and PAM modules that are required for the authentication scheme to work on the client computers. If you just want to configure Arch to authenticate against an already existing LDAP server, you can skip to the second part.
NSS and PAM
NSS (which stands for Name Service Switch) is a system mechanism to configure different sources for common configuration databases. For example, /etc/passwd is a file type source for the passwd database.
PAM (which stands for Pluggable Authentication Module) is a mechanism used by Linux (and most *nixes) to extend its authentication schemes based on different plugins.
So to summarize, we need to configure NSS to use the OpenLDAP server as a source for the passwd, shadow and other configuration databases and then configure PAM to use these sources to authenticate it's users.
LDAP Server Setup
Installation
You can read about installation and basic configuration in the OpenLDAP article. After you have completed that, return here.
Set up access controls
To make sure that no-one can read the (encrypted) passwords from the LDAP server, but a user can edit their own password, add the following to /etc/openldap/slapd.conf and restart slapd.service afterwards:
slapd.conf
access to attrs=userPassword
by self write
by anonymous auth
by * none
access to *
by self write
by * read
Populate LDAP Tree with Base Data
Create a temporarily file called base.ldif with the following text.
base.ldif
# example.org dn: dc=example,dc=org dc: example o: Example Organization objectClass: dcObject objectClass: organization # Manager, example.org dn: cn=Manager,dc=example,dc=org cn: Manager description: LDAP administrator objectClass: organizationalRole objectClass: top roleOccupant: dc=example,dc=org # People, example.org dn: ou=People,dc=example,dc=org ou: People objectClass: top objectClass: organizationalUnit # Groups, example.org dn: ou=Groups,dc=example,dc=org ou: Groups objectClass: top objectClass: organizationalUnit
Add it to your OpenLDAP Tree:
$ ldapadd -D "cn=Manager,dc=example,dc=org" -W -f base.ldif
Test to make sure the data was imported:
$ ldapsearch -x -b 'dc=example,dc=org' '(objectclass=*)'
Adding users
To manually add a user, create an .ldif file like this:
user_joe.ldif
dn: uid=johndoe,ou=People,dc=example,dc=org
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: shadowAccount
uid: johndoe
cn: John Doe
sn: Doe
givenName: John
title: Guinea Pig
telephoneNumber: +0 000 000 0000
mobile: +0 000 000 0000
postalAddress: AddressLine1$AddressLine2$AddressLine3
userPassword: {CRYPT}xxxxxxxxxx
labeledURI: https://archlinux.org/
loginShell: /bin/bash
uidNumber: 9999
gidNumber: 9999
homeDirectory: /home/johndoe/
description: This is an example user
The xxxxxxxxxx in the userPassword entry should be replaced with the value in /etc/shadow or use the slappasswd command. Now add the user:
$ ldapadd -D "cn=Manager,dc=example,dc=org" -W -f user_joe.ldif
Client Setup
Install the OpenLDAP client as described in OpenLDAP. Make sure you can query the server with ldapsearch.
Next, install nss-pam-ldapdAUR from the official repositories.
NSS Configuration
NSS is a system facility which manages different sources as configuration databases. For example, /etc/passwd is a file type source for the passwd database, which stores the user accounts.
Edit /etc/nsswitch.conf which is the central configuration file for NSS. It tells NSS which sources to use for which system databases. We need to add the ldap directive to the passwd, group and shadow databases, so be sure your file looks like this:
passwd: files ldap group: files ldap shadow: files ldap
Edit /etc/nslcd.conf and change the base and uri lines to fit your ldap server setup.
Start nslcd.service using systemd.
You now should see your LDAP users when running getent passwd on the client.
Name Service Cache Daemon
You can optionally run NSCD. This is a daemon that NSS uses to cache lookups and queries for network backends. This way you can login when the LDAP server is down, it will also reduce load on the LDAP server.
Start nscd.service using systemd.
PAM Configuration
The basic rule of thumb for PAM configuration is to include pam_ldap.so wherever pam_unix.so is included. Arch moving to pambase has helped decrease the amount of edits required. For more details about configuring pam, the RedHat Documentation is quite good. You might also want the upstream documentation for nss-pam-ldapd.
First edit /etc/pam.d/system-auth. This file is included in most of the other files in pam.d, so changes here propagate nicely. Updates to pambase may change this file.
Make pam_ldap.so sufficient at the top of each section, except in the session section, where we make it optional.
/etc/pam.d/system-auth
auth sufficient pam_ldap.so auth required pam_unix.so try_first_pass nullok auth optional pam_permit.so auth required pam_env.so account sufficient pam_ldap.so account required pam_unix.so account optional pam_permit.so account required pam_time.so password sufficient pam_ldap.so password required pam_unix.so try_first_pass nullok sha512 shadow password optional pam_permit.so session required pam_limits.so session required pam_unix.so session optional pam_ldap.so session optional pam_permit.so
Then edit both /etc/pam.d/su and /etc/pam.d/su-l identically. The su-l file is used when the user runs su --login.
Make pam_ldap.so sufficient at the top of each section, and add use_first_pass to pam_unix in the auth section.
/etc/pam.d/su
#%PAM-1.0 auth sufficient pam_ldap.so auth sufficient pam_rootok.so # Uncomment the following line to implicitly trust users in the "wheel" group. #auth sufficient pam_wheel.so trust use_uid # Uncomment the following line to require a user to be in the "wheel" group. #auth required pam_wheel.so use_uid auth required pam_unix.so use_first_pass account sufficient pam_ldap.so account required pam_unix.so session sufficient pam_ldap.so session required pam_unix.so
To enable users to edit their password, edit /etc/pam.d/passwd:
/etc/pam.d/passwd
#%PAM-1.0 password sufficient pam_ldap.so #password required pam_cracklib.so difok=2 minlen=8 dcredit=2 ocredit=2 retry=3 #password required pam_unix.so sha512 shadow use_authtok password required pam_unix.so sha512 shadow nullok
Create home folders at login
If you want home folders to be created at login (eg: if you aren't using NFS to store home folders), edit /etc/pam.d/system-login and add pam_mkhomedir.so to the session section above any "sufficient" items. This will cause home folder creation when logging in at a tty, from ssh, xdm, kdm, gdm, etc. You might choose to edit additional files in the same way, such as /etc/pam.d/su and /etc/pam.d/su-l to enable it for su and su --login. If you don't want to do this for ssh logins, edit system-local-login instead of system-login, etc.
/etc/pam.d/system-login
...top of file not shown... session optional pam_loginuid.so session include system-auth session optional pam_motd.so motd=/etc/motd session optional pam_mail.so dir=/var/spool/mail standard quiet -session optional pam_systemd.so session required pam_env.so session required pam_mkhomedir.so skel=/etc/skel umask=0022
/etc/pam.d/su-l
...top of file not shown... session required pam_mkhomedir.so skel=/etc/skel umask=0022 session sufficient pam_ldap.so session required pam_unix.so
Enable sudo
To enable sudo from an LDAP user, edit /etc/pam.d/sudo. You'll also need to modify sudoers accordingly.
/etc/pam.d/sudo
#%PAM-1.0 auth sufficient pam_ldap.so auth required pam_unix.so try_first_pass auth required pam_nologin.so
Resources
The official page of the nss-pam-ldapd packet
The PAM and NSS page at the Debian Wiki 1 2
Using LDAP for single authentication