97 lines
3.1 KiB
Groff
97 lines
3.1 KiB
Groff
.Sh DESCRIPTION
|
|
The Pluggable Authentication Modules (PAM) library abstracts a number
|
|
of common authentication-related operations and provides a framework
|
|
for dynamically loaded modules that implement these operations in
|
|
various ways.
|
|
.Ss Terminology
|
|
In PAM parlance, the application that uses PAM to authenticate a user
|
|
is the server, and is identified for configuration purposes by a
|
|
service name, which is often (but not necessarily) the program name.
|
|
.Pp
|
|
The user requesting authentication is called the applicant, while the
|
|
user (usually, root) charged with verifying his identity and granting
|
|
him the requested credentials is called the arbitrator.
|
|
.Pp
|
|
The sequence of operations the server goes through to authenticate a
|
|
user and perform whatever task he requested is a PAM transaction; the
|
|
context within which the server performs the requested task is called
|
|
a session.
|
|
.Pp
|
|
The functionality embodied by PAM is divided into six primitives
|
|
grouped into four facilities: authentication, account management,
|
|
session management and password management.
|
|
.Ss Conversation
|
|
The PAM library expects the application to provide a conversation
|
|
callback which it can use to communicate with the user.
|
|
Some modules may use specialized conversation functions to communicate
|
|
with special hardware such as cryptographic dongles or biometric
|
|
devices.
|
|
See
|
|
.Xr pam_conv 3
|
|
for details.
|
|
.Ss Initialization and Cleanup
|
|
The
|
|
.Fn pam_start
|
|
function initializes the PAM library and returns a handle which must
|
|
be provided in all subsequent function calls.
|
|
The transaction state is contained entirely within the structure
|
|
identified by this handle, so it is possible to conduct multiple
|
|
transactions in parallel.
|
|
.Pp
|
|
The
|
|
.Fn pam_end
|
|
function releases all resources associated with the specified context,
|
|
and can be called at any time to terminate a PAM transaction.
|
|
.Ss Storage
|
|
The
|
|
.Fn pam_set_item
|
|
and
|
|
.Fn pam_get_item
|
|
functions set and retrieve a number of predefined items, including the
|
|
service name, the names of the requesting and target users, the
|
|
conversation function, and prompts.
|
|
.Pp
|
|
The
|
|
.Fn pam_set_data
|
|
and
|
|
.Fn pam_get_data
|
|
functions manage named chunks of free-form data, generally used by
|
|
modules to store state from one invocation to another.
|
|
.Ss Authentication
|
|
There are two authentication primitives:
|
|
.Fn pam_authenticate
|
|
and
|
|
.Fn pam_setcred .
|
|
The former authenticates the user, while the latter manages his
|
|
credentials.
|
|
.Ss Account Management
|
|
The
|
|
.Fn pam_acct_mgmt
|
|
function enforces policies such as password expiry, account expiry,
|
|
time-of-day restrictions, and so forth.
|
|
.Ss Session Management
|
|
The
|
|
.Fn pam_open_session
|
|
and
|
|
.Fn pam_close_session
|
|
functions handle session setup and teardown.
|
|
.Ss Password Management
|
|
The
|
|
.Fn pam_chauthtok
|
|
function allows the server to change the user's password, either at
|
|
the user's request or because the password has expired.
|
|
.Ss Miscellaneous
|
|
The
|
|
.Fn pam_putenv ,
|
|
.Fn pam_getenv
|
|
and
|
|
.Fn pam_getenvlist
|
|
functions manage a private environment list in which modules can set
|
|
environment variables they want the server to export during the
|
|
session.
|
|
.Pp
|
|
The
|
|
.Fn pam_strerror
|
|
function returns a pointer to a string describing the specified PAM
|
|
error code.
|