#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <strings.h>
#include <signal.h>
#include <pwd.h>
#include <errno.h>
#include <security/pam_appl.h>
extern int pam_tty_conv(int num_msg, struct pam_message **msg,struct pam_response **response, void *appdata_ptr);
/* Disable keyboard interrupts (Ctrl-C, Ctrl-Z, Ctrl-\) */
static void disable_kbd_signals(void)
{(void) signal(SIGINT, SIG_IGN);
(void) signal(SIGTSTP, SIG_IGN);
(void) signal(SIGQUIT, SIG_IGN);
}
/* Terminate current user session, i.e., logout */
static void logout()
{
    pid_t pgroup = getpgrp();
    (void) signal(SIGTERM, SIG_IGN);
    (void) fprintf(stderr, "Sorry, your session can't be restored.\n");
    (void) fprintf(stderr, "Press return to terminate this session.\n");
    (void) getchar();
    (void) kill(-pgroup, SIGTERM);
    (void) sleep(2);
    (void) kill(-pgroup, SIGKILL);
    exit(-1);
}
int main(int argc, char *argv)
{
    struct pam_conv conv = { pam_tty_conv, NULL };
    pam_handle_t *pamh;
    struct passwd *pw;
    int err;
    disable_kbd_signals();
    if ((pw = getpwuid(getuid())) == NULL) {
        (void) fprintf(stderr, "plock: Can't get username: %s\n",
            strerror(errno));
        exit(1);
    }
    /* Initialize PAM framework */
    err = pam_start("plock", pw->pw_name, &conv, &pamh);
    if (err != PAM_SUCCESS) {
        (void) fprintf(stderr, "plock: pam_start failed: %s\n",
        pam_strerror(pamh, err));
        exit(1);
    }
    /* Authenticate user in order to unlock screen */
    do {
    (void) fprintf(stderr, "Terminal locked for %s. ", pw->pw_name);
        err = pam_authenticate(pamh, 0);
        if (err == PAM_USER_UNKNOWN)
            logout();
        else if (err != PAM_SUCCESS) {
            (void) fprintf(stderr, "Invalid password.\n");
        }
    } while (err != PAM_SUCCESS);
    /* Make sure account and password are still valid */
    switch (err = pam_acct_mgmt(pamh, 0)) {
    case PAM_USER_UNKNOWN:
    case PAM_ACCT_EXPIRED:

        /* User not allowed in anymore */
        logout();
        break;
    case PAM_NEW_AUTHTOK_REQD:
        /* The user's password has expired. Get a new one */
        do {
        err = pam_chauthtok(pamh, 0);
        } while (err == PAM_AUTHTOK_ERR);
        if (err != PAM_SUCCESS)
            logout();
        break;
    }
if (pam_setcred(pamh, PAM_REFRESH_CRED)!= PAM_SUCCESS)
{
    logout();
}
    (void) pam_end(pamh, 0);
    exit(0);
}