Pam unix vs. pam ldap
From Brandonhutchinson.com
(Difference between revisions)
(→''pam_ldap'') |
(→Authentication walk-through) |
||
| Line 34: | Line 34: | ||
=== ''pam_unix'' === | === ''pam_unix'' === | ||
| - | + | With ''pam_unix'': | |
| - | *An LDAP search is performed in the ''ou=people'' container for an entry that contains ''objectClass=shadowAccount'' and ''uid=user''. The search base is the value of ''NS_LDAP_SEARCH_BASEDN'' from ''/var/ldap/ldap_client_file''. | + | * An LDAP search is performed in the ''ou=people'' container for an entry that contains ''objectClass=shadowAccount'' and ''uid=user''. The search base is the value of ''NS_LDAP_SEARCH_BASEDN'' from ''/var/ldap/ldap_client_file''. |
* If an entry is found, the password specified on the command line is hashed with ''crypt()'' and compared with the ''userPassword'' attribute. If the values match, the user is authenticated. | * If an entry is found, the password specified on the command line is hashed with ''crypt()'' and compared with the ''userPassword'' attribute. If the values match, the user is authenticated. | ||
=== ''pam_ldap'' === | === ''pam_ldap'' === | ||
| - | + | With ''pam_ldap'': | |
* An LDAP search is performed in the ''ou=people'' container for an entry that contains ''object=posixAccount'' and ''uid=user''. The search base is the value of ''NS_LDAP_SEARCH_BASEDN'' from ''/var/ldap/ldap_client_file''. | * An LDAP search is performed in the ''ou=people'' container for an entry that contains ''object=posixAccount'' and ''uid=user''. The search base is the value of ''NS_LDAP_SEARCH_BASEDN'' from ''/var/ldap/ldap_client_file''. | ||
* If an entry is found, the client attempts to bind to the LDAP server using the Distinguished Name (DN) (e.g., uid=user,ou=people,dc=example,dc=com) and password specified on the command line. If the client is able to bind, the user is authenticated. | * If an entry is found, the client attempts to bind to the LDAP server using the Distinguished Name (DN) (e.g., uid=user,ou=people,dc=example,dc=com) and password specified on the command line. If the client is able to bind, the user is authenticated. | ||
Revision as of 22:17, 14 December 2007
Contents |
Overview
The following notes list some differences between pam_unix and pam_ldap authentication.
pam_unix
With pam_unix:
- The userPassword attribute must be non-null.
- Passwords must be stored in {crypt} format on the LDAP server.
- The proxy agent (e.g., cn=proxyagent,ou=profile,dc=example,dc=com) must have read and search privileges for the userPassword attribute.
- ldaplist -l passwd will return all password hashes, similar to ypcat passwd in a NIS environment.
- The entered password is not sent to the LDAP server.
- The default /etc/pam.conf file is configured for pam_unix (at least on Solaris 8).
Given the severe limitation of ldaplist -l password returning all password hashes, pam_ldap should be used if possible.
pam_ldap
With pam_ldap:
- The proxy agent (e.g., cn=proxyagent,ou=profile,dc=example,dc=com) does not need read and search privileges for the userPassword attribute.
- If the LDAP server is properly configured, ldaplist -l passwd will not return all user password hashes.
- The entered password is sent to the LDAP server, so encryption (e.g., TLS:Simple) should be used.
- The default /etc/pam.conf will have to be modified.
Authentication walk-through
A user attempts to login to a host using ssh and is prompted for a password:
$ ssh user@host Password:
What happens next?
pam_unix
With pam_unix:
- An LDAP search is performed in the ou=people container for an entry that contains objectClass=shadowAccount and uid=user. The search base is the value of NS_LDAP_SEARCH_BASEDN from /var/ldap/ldap_client_file.
- If an entry is found, the password specified on the command line is hashed with crypt() and compared with the userPassword attribute. If the values match, the user is authenticated.
pam_ldap
With pam_ldap:
- An LDAP search is performed in the ou=people container for an entry that contains object=posixAccount and uid=user. The search base is the value of NS_LDAP_SEARCH_BASEDN from /var/ldap/ldap_client_file.
- If an entry is found, the client attempts to bind to the LDAP server using the Distinguished Name (DN) (e.g., uid=user,ou=people,dc=example,dc=com) and password specified on the command line. If the client is able to bind, the user is authenticated.
