PAM_SM_AUTHENTICATE(3PAM) PAM Library Functions PAM_SM_AUTHENTICATE(3PAM)

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(3PAM), the PAM framework calls
pam_sm_authenticate() from the modules listed in the pam.conf(5) file.
The authentication provider supplies the back-end functionality for this
interface function.


The pam_sm_authenticate() function 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 flags 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_ERR
The user has a null authentication token.


The argc argument represents the number of module options passed in from
the configuration file pam.conf(5). 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 and 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(3PAM). This information is intended for use by
pam_setcred().

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
Cannot 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.

ATTRIBUTES

See attributes(7) for description of the following attributes:


+--------------------+-------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------------+
|Interface Stability | Stable |
+--------------------+-------------------------+
|MT-Level | MT-Safe with exceptions |
+--------------------+-------------------------+

SEE ALSO

libpam(3LIB), pam(3PAM), pam_authenticate(3PAM), pam_get_item(3PAM),
pam_set_data(3PAM), pam_set_item(3PAM), pam_setcred(3PAM),
pam_start(3PAM), pam.conf(5), attributes(7)

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.


The interfaces in libpam(3LIB) are MT-Safe only if each thread within the
multithreaded application uses its own PAM handle.


If the PAM_REPOSITORY item_type is set and a service module does not
recognize the type, the service module does not process any information,
and returns PAM_IGNORE. If the PAM_REPOSITORY item_type is not set, a
service module performs its default action.

August 19, 2023 PAM_SM_AUTHENTICATE(3PAM)