/*
This program was contributed by Shane Watts
[modifications by AGM]

You need to add the following (or equivalent) to the /etc/pam.conf file.
# check authorization
check_user auth required /usr/lib/security/pam_unix_auth.so
check_user account required /usr/lib/security/pam_unix_acct.so
*/

#include <security/pam_appl.h>
#include <security/pam_misc.h>
#include <stdio.h>

static struct pam_conv conv = {
misc_conv,
NULL
};

int main(int argc, char *argv[])
{
pam_handle_t *pamh=NULL;
int retval;
const char *user="nobody";

if(argc == 2) {
user = argv[1];
}

if(argc > 2) {
fprintf(stderr, "Usage: check_user [username]\n");
exit(1);
}

retval = pam_start("check_user", user, &conv, &pamh);

if (retval == PAM_SUCCESS)
retval = pam_authenticate(pamh, 0); /* is user really user? */

if (retval == PAM_SUCCESS)
retval = pam_acct_mgmt(pamh, 0); /* permitted access? */

/* This is where we have been authorized or not. */

if (retval == PAM_SUCCESS) {
fprintf(stdout, "Authenticated\n");
} else {
fprintf(stdout, "Not Authenticated\n");
}

if (pam_end(pamh,retval) != PAM_SUCCESS) { /* close Linux-PAM */
pamh = NULL;
fprintf(stderr, "check_user: failed to release authenticator\n");
exit(1);
}

return ( retval == PAM_SUCCESS ? 0:1 ); /* indicate success */
}