NAME

       pam - Pluggable Authentication Modules Library

SYNOPSIS

       #include <security/pam_appl.h>

       #include <security/pam_modules.h>

       #include <security/pam_ext.h>

DESCRIPTION

       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 Upon return the handle pamh is no longer valid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

       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

       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

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