pam(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | NOTES | COLOPHON

PAM(3)                      Linux-PAM Manual                      PAM(3)

NAME         top

       pam - Pluggable Authentication Modules Library

SYNOPSIS         top

       #include <security/pam_appl.h>

       #include <security/pam_modules.h>

       #include <security/pam_ext.h>

DESCRIPTION         top

       PAM is a system of libraries that handle the authentication tasks
       of applications (services) on the system. The library provides a
       stable general interface (Application Programming Interface -
       API) that privilege granting programs (such as login(1) and
       su(1)) defer to to perform standard authentication tasks.

   Initialization and Cleanup
       The pam_start(3) function creates the PAM context and initiates
       the PAM transaction. It is the first of the PAM functions that
       needs to be called by an application. The transaction state is
       contained entirely within the structure identified by this
       handle, so it is possible to have multiple transactions in
       parallel. But it is not possible to use the same handle for
       different transactions, a new one is needed for every new
       context.

       The pam_end(3) function terminates the PAM transaction and is the
       last function an application should call in the PAM context. Upon
       return the handle pamh is no longer valid and all memory
       associated with it will be invalid. It can be called at any time
       to terminate a PAM transaction.

   Authentication
       The pam_authenticate(3) function is used to authenticate the
       user. The user is required to provide an authentication token
       depending upon the authentication service, usually this is a
       password, but could also be a finger print.

       The pam_setcred(3) function manages the user's credentials.

   Account Management
       The pam_acct_mgmt(3) function is used to determine if the user's
       account is valid. It checks for authentication token and account
       expiration and verifies access restrictions. It is typically
       called after the user has been authenticated.

   Password Management
       The pam_chauthtok(3) function is used to change the
       authentication token for a given user on request or because the
       token has expired.

   Session Management
       The pam_open_session(3) function sets up a user session for a
       previously successful authenticated user. The session should
       later be terminated with a call to pam_close_session(3).

   Conversation
       The PAM library uses an application-defined callback to allow a
       direct communication between a loaded module and the application.
       This callback is specified by the struct pam_conv passed to
       pam_start(3) at the start of the transaction. See pam_conv(3) for
       details.

   Data Objects
       The pam_set_item(3) and pam_get_item(3) functions allows
       applications and PAM service modules to set and retrieve PAM
       informations.

       The pam_get_user(3) function is the preferred method to obtain
       the username.

       The pam_set_data(3) and pam_get_data(3) functions allows PAM
       service modules to set and retrieve free-form data from one
       invocation to another.

   Environment and Error Management
       The pam_putenv(3), pam_getenv(3) and pam_getenvlist(3) functions
       are for maintaining a set of private environment variables.

       The pam_strerror(3) function returns a pointer to a string
       describing the given PAM error code.

RETURN VALUES         top

       The following return codes are known by PAM:

       PAM_ABORT
           Critical error, immediate abort.

       PAM_ACCT_EXPIRED
           User account has expired.

       PAM_AUTHINFO_UNAVAIL
           Authentication service cannot retrieve authentication info.

       PAM_AUTHTOK_DISABLE_AGING
           Authentication token aging disabled.

       PAM_AUTHTOK_ERR
           Authentication token manipulation error.

       PAM_AUTHTOK_EXPIRED
           Authentication token expired.

       PAM_AUTHTOK_LOCK_BUSY
           Authentication token lock busy.

       PAM_AUTHTOK_RECOVERY_ERR
           Authentication information cannot be recovered.

       PAM_AUTH_ERR
           Authentication failure.

       PAM_BUF_ERR
           Memory buffer error.

       PAM_CONV_ERR
           Conversation failure.

       PAM_CRED_ERR
           Failure setting user credentials.

       PAM_CRED_EXPIRED
           User credentials expired.

       PAM_CRED_INSUFFICIENT
           Insufficient credentials to access authentication data.

       PAM_CRED_UNAVAIL
           Authentication service cannot retrieve user credentials.

       PAM_IGNORE
           The return value should be ignored by PAM dispatch.

       PAM_MAXTRIES
           Have exhausted maximum number of retries for service.

       PAM_MODULE_UNKNOWN
           Module is unknown.

       PAM_NEW_AUTHTOK_REQD
           Authentication token is no longer valid; new one required.

       PAM_NO_MODULE_DATA
           No module specific data is present.

       PAM_OPEN_ERR
           Failed to load module.

       PAM_PERM_DENIED
           Permission denied.

       PAM_SERVICE_ERR
           Error in service module.

       PAM_SESSION_ERR
           Cannot make/remove an entry for the specified session.

       PAM_SUCCESS
           Success.

       PAM_SYMBOL_ERR
           Symbol not found.

       PAM_SYSTEM_ERR
           System error.

       PAM_TRY_AGAIN
           Failed preliminary check by password service.

       PAM_USER_UNKNOWN
           User not known to the underlying authentication module.

SEE ALSO         top

       pam_acct_mgmt(3), pam_authenticate(3), pam_chauthtok(3),
       pam_close_session(3), pam_conv(3), pam_end(3), pam_get_data(3),
       pam_getenv(3), pam_getenvlist(3), pam_get_item(3),
       pam_get_user(3), pam_open_session(3), pam_putenv(3),
       pam_set_data(3), pam_set_item(3), pam_setcred(3), pam_start(3),
       pam_strerror(3)

NOTES         top

       The libpam interfaces are only thread-safe if each thread within
       the multithreaded application uses its own PAM handle.

COLOPHON         top

       This page is part of the linux-pam (Pluggable Authentication
       Modules for Linux) project.  Information about the project can be
       found at ⟨http://www.linux-pam.org/⟩.  If you have a bug report
       for this manual page, see ⟨//www.linux-pam.org/⟩.  This page was
       obtained from the tarball Linux-PAM-1.3.0.tar.bz2 fetched from
       ⟨http://www.linux-pam.org/library/⟩ on 2020-12-18.  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Linux-PAM Manual               04/01/2016                         PAM(3)

Pages that refer to this page: pam_sm_acct_mgmt(3)pam_sm_authenticate(3)pam_sm_chauthtok(3)pam_sm_close_session(3)pam_sm_open_session(3)pam_sm_setcred(3)pam.conf(5)PAM(8)pam_filter(8)