pam_sm_authenticate(3)

NAME
pam_sm_authenticate - Service provider implementation for pam_authenticate

SYNOPSIS

cc [ flag ... ] file ... -lpam [ library ... ]

#include <security/pam_appl.h>
#include <security/pam_modules.h>

int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv);

DESCRIPTION
In response to a call to pam_authenticate(3), the PAM framework calls pam_sm_authenticate() from the modules listed in the pam.conf(4) file. The authentication provider supplies the back-end functionality for this interface function.

The function, pam_sm_authenticate(), is called to verify the identity of the current user. The user is usually required to enter a password or similar authentication token depending upon the authentication scheme configured within the system. The user in question is specified by a prior call to pam_start(), and is referenced by the authentication handle, pamh.

If the user is unknown to the authentication service, the service module should mask this error and continue to prompt the user for a password. It should then return the error, PAM_USER_UNKNOWN.

The following flag may be passed in to pam_sm_authenticate():

    PAM_SILENT
        The authentication service should not generate any messages

    PAM_DISALLOW_NULL_AUTHTOK
        The authentication service should return PAM_AUTH_ERROR if the user has a null authentication token

The argc argument represents the number of module options passed in from the configuration file pam.conf(4). argv specifies the module options, which are interpreted and processed by the authentication service. Please refer to the specific module man pages for the various available options. If any unknown option is passed in, the module should log the error and ignore the option.

Before returning, pam_sm_authenticate() should call pam_get_item() and retrieve PAM_AUTHTOK. If it has not been set before (ie. the value is NULL), pam_sm_authenticate() should set it to the password entered by the user using pam_set_item().

An authentication module may save the authentication status (success or reason for failure) as state in the authentication handle using pam_set_data(3). This information is intended for use by pam_setcred().

NOTES
Modules should not retry the authentication in the event of a failure. Applications handle authentication retries and maintain the retry count. To limit the number of retries, the module can return a PAM_MAXTRIES error.

RETURN VALUES

Upon successful completion, PAM_SUCCESS must be returned. In addition, the following values may be returned:

    PAM_MAXTRIES
        Maximum number of authentication attempts exceeded

    PAM_AUTH_ERR
        Authentication failure

    PAM_CRED_INSUFFICIENT
        Can not access authentication data due to insufficient credentials

    PAM_AUTHINFO_UNAVAIL
        Underlying authentication service can not retrieve authentication information

    PAM_USER_UNKNOWN
        User not known to underlying authentication module

    PAM_IGNORE
        Ignore underlying authentication module regardless of whether the control flag is required, optional or sufficient

SEE ALSO
pam(3), pam_authenticate(3), pam.conf(4)