/* Program ax25login. (c) Petr Bravenec.
 * Free software, GPL License
 * prelozit prikazem:
 *  cc -Wall -o ax25login ax25login.c
 *  chmod 100 ax25login
 */

#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

#define PSWDLEN 5

void sigchld (int s) { exit(0); }

int main (int argc, char **argv) {
    char ptyn[20] ;
    int  pty_s, pty_m, f;
    char buf[1024];
    /* Tady je sifrovaci tabulka pro heslo. Na vyzvu opiste pismenko
     * ze spodniho radku, ktere odpovida pismenku (ve vyzve) z radku
     * horniho */
    char *ps="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    char *pw="Zvoltesi za vlasni HesLo neco UPLNE JINEHO,aby_vam_to_ncmajzli";
    int i, ix[PSWDLEN];
    srand(time(NULL));
    printf ("Heslo ");
    for (i=0; i<PSWDLEN; i++) {
        ix[i] = (int) ((double)strlen(pw) * rand() / (RAND_MAX+1.0));
        printf ("%1c",ps[ix[i]]);
        }
    printf (": \n");
    fflush (stdout);
    fgets  (buf, PSWDLEN+1, stdin);
    for (i=0; i<PSWDLEN; i++) 
        if (pw[ix[i]] != buf[i]) {
            printf("Chybne zadane heslo!\n");
            exit(1);
            }
    printf ("Dekuji. Heslo je v poradku\n");
    fflush (stdout);
    /* Potrebujeme otevrit pseudoterminal. Shell ma problemy fungovat 
     * pres pipu, tak mu predhodime neco jineho. Prvni musime
     * nejakou volnou pseudoterminalovou linku najit... */
    for (i='a'; i<'z'; i++) {
        sprintf (ptyn, "/dev/ptys%1c",i);
        pty_m = open (ptyn,O_RDWR);
        if (pty_m > 0) break;
        }
    if (pty_m < 0) {
        printf ("Nezdarilo se otevrit terminal\n");
        exit(1);
        }
    sprintf (ptyn, "/dev/ttys%1c",i);
    pty_s = open (ptyn,O_RDWR);
    /* Nastartovani dalsiho programu. Rodicovska cast bude pouze 
     * zprostredkovavat spojeni s ax25d a protistanici. */
    f = fork ();
    if (-1==f) {
        printf ("Nezdarilo se nastartovat proces\n");
        exit(1);
        }
    if (f>0) { /* rodicovska cast */
        int    rc;
        fd_set rfds;
        struct timeval tv;
        signal (SIGCHLD, sigchld);
        for (;;) {
            FD_ZERO(&rfds); FD_SET(0,&rfds); FD_SET(pty_m,&rfds);
            tv.tv_sec = 0; tv.tv_usec=10000;
            rc = select (pty_m+1, &rfds, NULL, NULL, &tv);
            if (rc<=0) continue;
            if (FD_ISSET(0,&rfds)) {
                i = read (0, buf, 1024); 
                if (i>0) 
                    write (pty_m, buf, i);
                }
            if (FD_ISSET(pty_m,&rfds)) {
                i = read (pty_m, buf, 1024); 
                if (i>0) 
                    write (0, buf, i);
                }
            }
        }
    /* V casti potomka nastartujeme shell */
    close(0);
    close(1);
    close(2);
    dup2 (pty_s, 0);
    dup2 (pty_s, 1);
    dup2 (pty_s, 2); 
    chdir ("/root");
    execl ("/bin/bash","-bash",NULL);
    printf ("Chyba pri startu shellu\n");
    exit (1);
}