source: trunk/minix/commands/simple/getty.c@ 16

/* getty - get tty speed                        Author: Fred van Kempen */

/*
 * GETTY  -     Initialize and serve a login-terminal for INIT.
 *              Also, select the correct speed. The STTY() code
 *              was taken from stty(1).c; which was written by
 *              Andrew S. Tanenbaum.
 *
 * Usage:       getty [-c filename] [-h] [-k] [-t] line [speed]
 *
 * Version:     3.4     02/17/90
 *
 * Author:      F. van Kempen, MicroWalt Corporation
 *
 * Modifications:
 *              All the good stuff removed to get a minimal getty, because
 *              many modems don't like all that fancy speed detection stuff.
 *              03/03/91        Kees J. Bot (kjb@cs.vu.nl)
 *
 *              Uname(), termios.  More nonsense removed.  (The result has
 *              only 10% of the original functionality, but a 10x chance of
 *              working.)
 *              12/12/92        Kees J. Bot
 *
 *              Customizable login banner.
 *              11/13/95        Kees J. Bot
 *
 *              Suspend/resume signals removed.
 *              2001-04-04      Kees J. Bot
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/utsname.h>

char LOGIN[] =          "/usr/bin/login";
char SHELL[] =          "/bin/sh";

char *tty_name;                 /* name of the line */

/* Crude indication of a tty being physically secure: */
#define securetty(dev)          ((unsigned) ((dev) - 0x0400) < (unsigned) 8)

void std_out(char *s)
{
  write(1, s, strlen(s));
}

/* Read one character from stdin.
 */
int readch(void)
{
  int st;
  char ch1;

  /* read character from TTY */
  st = read(0, &ch1, 1);
  if (st == 0) {
        std_out("\n");
        exit(0);
  }
  if (st < 0) {
        std_out("getty: ");
        std_out(tty_name);
        std_out(": read error\n");
        exit(1);
  }
  return(ch1 & 0xFF);
}


/* Handle the process of a GETTY.
 */
void do_getty(char *name, size_t len, char **args, char *ttyname)
{
  register char *np, *s, *s0;
  int ch;
  struct utsname utsname;
  char **banner, *t;
  static char *def_banner[] = { "%s  Release %r Version %v  (%t)\n\n%n login: ", 0 };

  /* Clean up tty name. */
  if((t = strrchr(ttyname, '/'))) ttyname = t + 1;

  /* Default banner? */
  if (args[0] == NULL) args = def_banner;

  /* Display prompt. */
  ch = ' ';
  *name = '\0';
  while (ch != '\n') {
        /* Get data about this machine. */
        uname(&utsname);

        /* Print the banner. */
        for (banner = args; *banner != NULL; banner++) {
                std_out(banner == args ? "\n" : " ");
                s0 = *banner;
                for (s = *banner; *s != 0; s++) {
                        if (*s == '\\') {
                                write(1, s0, s-s0);
                                s0 = s+2;
                                switch (*++s) {
                                case 'n':  std_out("\n"); break;
                                case 's':  std_out(" "); break;
                                case 't':  std_out("\t"); break;
                                case 0:    goto leave;
                                default:   s0 = s;
                                }
                        } else
                        if (*s == '%') {
                                write(1, s0, s-s0);
                                s0 = s+2;
                                switch (*++s) {
                                case 's':  std_out(utsname.sysname); break;
                                case 'n':  std_out(utsname.nodename); break;
                                case 'r':  std_out(utsname.release); break;
                                case 'v':  std_out(utsname.version); break;
                                case 'm':  std_out(utsname.machine); break;
                                case 'p':  std_out(utsname.arch); break;
                                case 't':  std_out(ttyname); break;
#if __minix_vmd
                                case 'k':  std_out(utsname.kernel); break;
                                case 'h':  std_out(utsname.hostname); break;
                                case 'b':  std_out(utsname.bus); break;
#endif
                                case 0:    goto leave;
                                default:   s0 = s-1;
                                }
                        }
                }
            leave:
                write(1, s0, s-s0);
        }

        np = name;
        while ((ch = readch()) != '\n') {
                if (np < name + len) *np++ = ch;
        }
        *np = '\0';
        if (*name == '\0') ch = ' ';    /* blank line typed! */
  }
}


/* Execute the login(1) command with the current
 * username as its argument. It will reply to the
 * calling user by typing "Password: "...
 */
void do_login(char *name)
{ 
  struct stat st;

  execl(LOGIN, LOGIN, name, (char *) NULL);
  /* Failed to exec login.  Impossible, but true.  Try a shell, but only if
   * the terminal is more or less secure, because it will be a root shell.
   */
  std_out("getty: can't exec ");
  std_out(LOGIN);
  std_out("\n");
  if (fstat(0, &st) == 0 && S_ISCHR(st.st_mode) && securetty(st.st_rdev)) {
        execl(SHELL, SHELL, (char *) NULL);
  }
}


int main(int argc, char **argv)
{
  register char *s;
  char name[30];
  struct sigaction sa;

  /* Don't let QUIT dump core. */
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = 0;
  sa.sa_handler = exit;
  sigaction(SIGQUIT, &sa, NULL);

  tty_name = ttyname(0);
  if (tty_name == NULL) {
        std_out("getty: tty name unknown\n");
        pause();
        return(1);
  }

  chown(tty_name, 0, 0);        /* set owner of TTY to root */
  chmod(tty_name, 0600);        /* mode to max secure */

  do_getty(name, sizeof(name), argv+1, tty_name);       /* handle getty() */
  name[29] = '\0';              /* make sure the name fits! */

  do_login(name);               /* and call login(1) if OK */

  return(1);                    /* never executed */
}