The SAMPLE service module for PAM is divided into four components: authentication, account management, password management, and session management. The sample module is a shared object that is dynamically loaded to provide the necessary functionality.

The SAMPLE authentication module, typically /usr/lib/security/pam_sample.so.1, provides functions to test the PAM framework functionality using the pam_sm_authenticate(3PAM) call. The SAMPLE module implementation of the pam_sm_authenticate(3PAM) function compares the user entered password with the password set in the pam.conf(4) file, or the string "test" if a default test password has not been set. The following options may be passed in to the SAMPLE Authentication module:

debug

Syslog debugging information at the LOG_DEBUG level.

passwd=newone

Sets the password to be "newone."

first_pass_good

The first password is always good when used with the use_first_pass or try_first_pass option.

first_pass_bad

The first password is always bad when used with the use_first_pass or try_first_pass option.

always_fail

Always returns PAM_AUTH_ERR.

always_succeed

Always returns PAM_SUCCESS.

always_ignore

Always returns PAM_IGNORE.

use_first_pass

Use the user's initial password (entered when the user is authenticated to the first authentication module in the stack) to authenticate with the SAMPLE module. If the passwords do not match, or if this is the first authentication module in the stack, quit and do not prompt the user for a password. It is recommended that this option only be used if the SAMPLE authentication module is designated as optional in the pam.conf configuration file.

try_first_pass

Use the user's initial password (entered when the user is authenticated to the first authentication module in the stack) to authenticate with the SAMPLE module. If the passwords do not match, or if this is the first authentication module in the stack, prompt the user for a password. The SAMPLE module pam_sm_setcred(3PAM) function always returns PAM_SUCCESS.

The SAMPLE Account Management Component, typically pam_sample.so.1, implements a simple access control scheme that limits machine access to a list of authorized users. The list of authorized users is supplied as option arguments to the entry for the SAMPLE account management PAM module in the pam.conf file. Note that the module always permits access to the root super user.

The option field syntax to limit access is shown below: allow= name[,name] allow= name [allow=name]

The example pam.conf show below permits only larry to login directly. rlogin is allowed only for don and larry. Once a user is logged in, the user can use su if the user are sam or eric.

The debug and nowarn options are also supported.

The SAMPLE Password Management Component function ( pam_sm_chauthtok(3PAM)), always returns PAM_SUCCESS.

The SAMPLE Session Management Component functions ( pam_sm_open_session(3PAM), pam_sm_close_session(3PAM)) always return PAM_SUCCESS.

See attributes(5) for description of the following attributes:

pam(3PAM), pam_sm_authenticate(3PAM), pam_sm_chauthtok(3PAM), pam_sm_close_session(3PAM), pam_sm_open_session(3PAM), pam_sm_setcred(3PAM), libpam(3LIB), pam.conf(4), attributes(5)

The interfaces in libpam() are MT-Safe only if each thread within the multi-threaded application uses its own PAM handle.