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Operating Systems Linux Red Hat PAM configuration: Kerberos authentication and NIS authorization problem Post 302386263 by geek.ksa on Tuesday 12th of January 2010 02:53:06 AM
Old 01-12-2010
PAM configuration: Kerberos authentication and NIS authorization problem

Hi,

I've configured two linux boxes to authenticate against Windows Active Directory using Kerberos while retrieving authorization data (uids, gids ,,,)from NIS.

The problem I ran into with my PAM configuration is that all authentication attempts succeed in order.i.e. if someone tried his NIS credentials he will be granted access!!

What I want is this: Kerberos authentication is tried first; if it fails, local files authentication ONLY is tried.

here's my PAM configuration from system-auth pam configuration file which is included by all systems pam-aware services:

Code:
auth        required      pam_env.so
auth        sufficient    pam_krb5.so debug
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

The issue here: I think the pam_unix module somehow contacts NIS for authentication if Kerberos fails. But, I had updated my sswitch.conf to look like:

Code:
passwd:     files nis
shadow:     files
group:      files nis

I thought the pam_unix.so module references this file to see where to look up passwords.

Please note that I can't remove nis form passwd and group sections because this is needed to get authorization (uid,gid) data from NIS.

The point is, above nsswitch.conf didn't resolve the issue, users are still able to log in using their NIS credentials!

Please help me figure out what is wrong here.
 

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PAM_UNIX(8)						    BSD System Manager's Manual 					       PAM_UNIX(8)

NAME
pam_unix -- UNIX PAM module SYNOPSIS
[service-name] module-type control-flag pam_unix [options] DESCRIPTION
The UNIX authentication service module for PAM provides functionality for two PAM categories: authentication and account management. In terms of the module-type parameter, they are the ``auth'' and ``account'' features. It also provides a null function for session management. UNIX Authentication Module The UNIX authentication component provides functions to verify the identity of a user (pam_sm_authenticate()), which obtains the relevant passwd(5) entry. It prompts the user for a password and verifies that this is correct with crypt(3). The following options may be passed to the authentication module: debug syslog(3) debugging information at LOG_DEBUG level. use_first_pass If the authentication module is not the first in the stack, and a previous module obtained the user's password, that password is used to authenticate the user. If this fails, the authentication module returns failure without prompting the user for a password. This option has no effect if the authentication module is the first in the stack, or if no previous modules obtained the user's password. try_first_pass This option is similar to the use_first_pass option, except that if the previously obtained password fails, the user is prompted for another password. auth_as_self This option will require the user to authenticate himself as the user given by getlogin(2), not as the account they are attempting to access. This is primarily for services like su(1), where the user's ability to retype their own password might be deemed sufficient. nullok If the password database has no password for the entity being authenticated, then this option will forgo password prompting, and silently allow authentication to succeed. UNIX Account Management Module The UNIX account management component provides a function to perform account management, pam_sm_acct_mgmt(). The function verifies that the authenticated user is allowed to login to the local user account by checking the password expiry date. The following options may be passed to the management module: debug syslog(3) debugging information at LOG_DEBUG level. UNIX Password Management Module The UNIX password management component provides a function to perform account management, pam_sm_chauthtok(). The function changes the user's password. The following options may be passed to the password module: debug syslog(3) debugging information at LOG_DEBUG level. no_warn suppress warning messages to the user. These messages include reasons why the user's authentication attempt was declined. passwd_db=name Change the user's password only the specified password database. Valid password database names are: files local password file nis NIS password database FILES
/etc/master.passwd default UNIX password database. SEE ALSO
passwd(1), getlogin(2), crypt(3), getpwent(3), syslog(3), nsswitch.conf(5), passwd(5), nis(8), pam(8) BSD
February 26, 2005 BSD
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