Kerberos 5 SU Authentication Module

The Kerberos 5 SU authentication component provides functions to verify the identity of a user (pam_sm_authenticate()), and determine whether or not the user is authorized to obtain the privileges of the target account. If the target account is “root”, then the Kerberos 5 principal used for authentication and authorization will be the “root” instance of the current user, e.g. “user/root@REAL.M”. Otherwise, the principal will simply be the current user's default principal, e.g. “user@REAL.M”.

The user is prompted for a password if necessary. Authorization is performed by comparing the Kerberos 5 principal with those listed in the .k5login file in the target account's home directory (e.g. /root/.k5login for root).

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.