pam_authenticate(3)

NAME
pam_authenticate - perform authentication within the PAM framework

SYNOPSIS

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

#include <security/pam_appl.h>

int pam_authenticate(pam_handle_t *pamh, int flags);

DESCRIPTION
pam_authenticate() is called to authenticate the current user. The user is usually required to enter a password or similar authentication token depending upon the authentication service configured within the system. The user in question should have been specified by a prior call to pam_start() or pam_set_item(). The following flags may be set in the flags field:

    PAM_SILENT
        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

NOTES

In the case of authentication failures due to an incorrect username or password, it is the responsibility of the application to retry pam_authenticate() and to maintain the retry count. An authentication service module may implement an internal retry count and return an error PAM_MAXTRIES if the module does not want the application to retry.

If the PAM framework can not load the authentication module, then it will return PAM_ABORT. This indicates a serious failure and that the application should not attempt to retry the authentication.

For security reasons, the location of authentication failures is hidden from the user. Thus, if several authentication services are stacked and a single service fails, pam_authenticate() requires that the user re-authenticate to all the services.

A null authentication token in the authentication database will result in successful authentication unless PAM_DISALLOW_NULL_AUTHTOK was specified. In such cases, there will not be any prompting for the user to enter an authentication token.

RETURN VALUES

Upon successful completion, PAM_SUCCESS is returned. In addition to the error return values described in pam(3), the following values may be returned:

    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 the underlying authentication module

    PAM_MAXTRIES
        An authentication service has maintained a retry count which has been reached. No further retries should be attempted.

SEE ALSO
pam(3), pam_start(3), pam_open_session(3), pam_setcred(3)