pam.conf(4) pam.conf(4)
NAME
pam.conf - configuration file for pluggable authentication modules
SYNOPSIS
/etc/pam.conf
DESCRIPTION
pam.conf is the configuration file for the Pluggable Authentication
Module architecture, or PAM. A PAM module provides functionality for
one or more of four possible services: authentication, account
management, session management, and password management.
An authentication service module provides functionality to
authenticate a user and set up user credentials. A account management
module provides functionality to determine if the current user's
account is valid. This includes checking for password and account
expiration, as well as verifying access hour restrictions. A session
management module provides functionality to set up and terminate login
sessions. A password management module provides functionality to
change a user's authentication token or password.
Simplified PAM.CONF configuration file
The pam.conf file contains a listing of services. Each service is
paired with a corresponding service module. When a service is
requested, its associated module is invoked. Each entry has the
following format:
service_name module_type control_flag module_path options
Below is an example of the pam.conf configuration file with support
for authentication, account management, and session management
modules.
login auth required /usr/lib/security/libpam_unix.1 debug
login session required /usr/lib/security/libpam_unix.1
login account required /usr/lib/security/libpam_unix.1
dtlogin session required /usr/lib/security/libpam_unix.1
other auth required /usr/lib/security/libpam_unix.1
other password required /usr/lib/security/libpam_unix.1
service_name The service_name denotes the service (for example,
login, or dtlogin). The keyword, other, indicates the
module all other applications which have not been
specified should use. The other keyword can also be
used if all services of the same module_type have the
same requirements. In the example above, since all of
the services use the same session module, they could
have been replaced by a single other line.
module_type module_type denotes the service module type:
authentication (auth), account management (account),
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session management (session), or password management
(password).
control_flag The control_flag field determines the behavior of
stacking, and will be discussed in more detail below.
module_path The module_path field specifies the pathname to a
shared library object which implements the service
functionality. If the pathname is not absolute, it is
assumed to be relative to /usr/lib/security.
options The options field is used by the PAM framework layer to
pass module specific options to the modules. It is up
to the module to parse and interpret the options. This
field can be used by the modules to turn on debugging
or to pass any module specific parameters such as a
TIMEOUT value. It can also be used to support unified
login. The options supported by the modules are
documented in their respective manual pages. For
example, pam_unix(5) lists the options accepted by the
UNIX module.
Integrating Multiple Authentication Services With Stacking
When a service_name of the same module_type is defined more than once,
the service is said to be stacked. Each module referenced in the
module_path for that service is then processed in the order that it
occurs in the configuration file. The control_flag field specifies
the continuation and failure semantics of the modules, and may be
required, optional, or sufficient.
The PAM framework processes each service module in the stack. If all
required modules in the stack succeed, then success is returned
(optional and sufficient error values are ignored). If one or more
required modules fail, then the error value from the first required
module that failed is returned.
If none of the service modules in the stack are designated as
required, then the PAM framework requires that at least one optional
or sufficient module succeed. If all fail then the error value from
the first service module in the stack is returned.
The only exception to the above is caused by the sufficient flag. If
a service module that is designated as sufficient succeeds, then the
PAM framework immediately returns success to the application (all
subsequent services modules, even required ones, in the stack are
ignored), given that all prior required modules had also succeeded.
If a prior required module failed, then the error value from that
module is returned.
If a module does not exist or can not be opened, then the pam.conf
entry is ignored and an error will be logged through syslog(3C) at the
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LOG_CRIT level.
Below is a sample configuration file that stacks the login, and
dtlogin services.
login auth required /usr/lib/security/libpam_unix.1. debug
login auth optional /usr/lib/security/libpam_inhouse.1
dtlogin auth sufficient /usr/lib/security/libpam_unix.1 debug
dtlogin auth required /usr/lib/security/libpam_inhouse.1
In the case of login, the user is authenticated by the UNIX and
inhouse authentication modules. The required keyword for control_flag
requires that the user be allowed to login only if the user is
authenticated by the UNIX service module. Inhouse authentication is
optional by virtue of the optional keyword in the control_flag field.
The user can still log in even if inhouse authentication fails.
In the case of dtlogin, the sufficient keyword for control_flag
specifies that if the UNIX authentication check succeeds, then PAM
should return success to dtlogin. The inhouse authentication module
(the next module in the stack) will only be invoked if the UNIX
authentication check fails.
Some modules may return PAM_IGNORE in certain situations. In these
cases the PAM framework ignores the entire entry in pam.conf
regardless of whether or not it is required, optional or sufficient.
Configuration Per User
pam.conf contains information to configure all the users on a system.
But sometimes it is necessary to configure user by user. A user
policy definition is made through a specific module named
libpam_updbe.1. This module reads a file named /etc/pam_user.conf
which describes the user's configurations.
Below is a sample configuration file (/etc/pam.conf) that uses the
module libpam_updbe.1.
login auth required /usr/lib/security/libpam_updbe.1
login auth required /usr/lib/security/libpam_unix.1
su auth required /usr/lib/security/libpam_updbe.1
su auth required /usr/lib/security/libpam_unix.1
OTHER auth required /usr/lib/security/libpam_unix.1
login password required /usr/lib/security/libpam_updbe.1
login password required /usr/lib/security/libpam_unix.1
passwd password required /usr/lib/security/libpam_updbe.1
passwd password required /usr/lib/security/libpam_unix.1
OTHER password required /usr/lib/security/libpam_unix.1
The module libpam_updbe.1 searches the configuration file
/etc/pam_user.conf and reads the configuration associated with the
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login name of the current user. If there is no configuration
concerning the current user in the pam_user.conf file, the PAM
framework ignores the line containing libpam_updbe.1. The pam.conf
applies for those users who are not configured in pam_user.conf.
NOTES
If an error is found in an entry due to invalid service_name,
module_type, or control_flag, then the entry is ignored. If there are
no valid entries for the given module_type, the PAM framework returns
an error to the application.
EXAMPLES
The following is a sample pam.conf configuration file. Lines that
begin with the # symbol are treated as comments, and therefore
ignored.
#
# PAM configuration
#
# Authentication management for login service is stacked.
# Both UNIX and inhouse authentication functions are invoked.
login auth required /usr/lib/security/libpam_unix.1
login auth required /usr/lib/security/libpam_inhouse.1 try_first_pass
dtlogin auth required /usr/lib/security/libpam_unix.1
dtlogin auth required /usr/lib/security/libpam_inhouse.1 try_first_pass
#
# Other services use UNIX authentication
other auth required /usr/lib/security/libpam_unix.1
#
# Account management for login service is stacked.
# UNIX account management is required; inhouse account management is optional
login account required /usr/lib/security/libpam_unix.1
login account optional /usr/lib/security/libpam_inhouse.1
dtlogin account required /usr/lib/security/libpam_unix.1
dtlogin account optional /usr/lib/security/libpam_inhouse.1
other account required /usr/lib/security/libpam_unix.1
#
# Session management
other session required /usr/lib/security/libpam_unix.1
#
# Password management
other password required /usr/lib/security/libpam_unix.1
The following is a sample pam.conf configuration which uses the
libpam_updbe.1 module to configure a user. Lines that begin with the
# symbol are treated as comments, and therefore ignored.
#
# PAM configuration
#
# Authentication management for login service is stacked.
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# Both UNIX and inhouse authentication functions are invoked.
login auth required /usr/lib/security/libpam_updbe.1
login auth required /usr/lib/security/libpam_unix.1
login auth required /usr/lib/security/libpam_inhouse.1 try_first_pass
dtlogin auth required /usr/lib/security/libpam_updbe.1
dtlogin auth required /usr/lib/security/libpam_unix.1
dtlogin auth required /usr/lib/security/libpam_inhouse.1 try_first_pass
#
# Other services use UNIX authentication
other auth required /usr/lib/security/pam_unix.so.1
#
# Account management for login service is stacked.
# UNIX account management is required; inhouse account management is optional
login account required /usr/lib/security/libpam_unix.1
login account optional /usr/lib/security/libpam_inhouse.1
dtlogin account required /usr/lib/security/libpam_unix.1
dtlogin account optional /usr/lib/security/libpam_inhouse.1
other account required /usr/lib/security/libpam_unix.1
#
# Session management
other session required /usr/lib/security/libpam_unix.1
#
# Password management
passwd password required /usr/lib/security/libpam_updbe.1
passwd password required /usr/lib/security/libpam_unix.1
other password required /usr/lib/security/libpam_unix.1
Utilities and Files
A list of utilities that are known to use PAM include: login, passwd,
su, and dtlogin.
The PAM configuration file does not dictate either the name or the
location of the service specific modules. The convention, however, is
the following:
/usr/lib/security/libpam_service_name.x
Implements various function of specific authentication
services.
/etc/pam.conf
Configuration file.
/usr/lib/libpam.1
Implements the PAM framework library.
SEE ALSO
dtlogin(1), login(1), passwd(1), su(1), pam(3).
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