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/*******************************************************************************
* rungetty.c
* This is rungetty, a small console getty that allows for execution of
* arbitrary programs.
*
* Copyright (C) 1999 Jakob 'sparky' Kaivo
* jake@nodomainname.net
*
* Based on code from mingetty by Florian La Roche. See the
* file mingetty.comments for original text.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
******************************************************************************/
#define DEBUG_THIS 0
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <string.h>
#include <time.h>
#include <utmp.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/signal.h>
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/types.h>
#include <sys/utsname.h>
#ifndef _PATH_LOGIN
#define _PATH_LOGIN "/bin/login"
#endif
#ifdef linux
#include <sys/param.h>
#define USE_SYSLOG
#endif
/* If USE_SYSLOG is undefined all diagnostics go directly to /dev/console. */
#ifdef USE_SYSLOG
#include <syslog.h>
#endif
#define ISSUE "/etc/issue" /* displayed before the login prompt */
#define LOGIN " login: " /* login prompt */
#define PROMPT_RETURN "Press return to activate " /* when --prompt specified */
/* name of this program (argv[0]) */
static char *progname;
/* path of working directory for program */
static char *progpath = NULL;
/* 'nice' level of the program */
static int priority = 0;
/* on which tty line are we sitting? (e.g. tty1) */
static char *tty;
/* and what program do we run? */
static char *program_run;
/* some information about this host */
static struct utsname uts;
/* the hostname */
static char hn[MAXHOSTNAMELEN + 1];
/* process ID of this program */
static pid_t pid;
/* current time */
static time_t cur_time;
/* do not send a reset string to the terminal ? */
static int noclear = 0;
/* Print the whole string of gethostname() instead of just until the next "." */ static int longhostname = 0;
/* The user to run as */
static struct passwd *user;
/* The group */
static struct group *u_group;
/* set to wait for return before doing anything */
static int prompt_return = 0;
/* time to wait, seconds */
static int delay = 0;
/* AUTO_LAST points to a timestamp file used to limit autologins to
immediately after system boot. */
#define AUTO_LAST "/var/log/autologin"
/* AUTO_TTY is the tty on which autologins will be accepted. If set
to an empty string, autologins will be accepted on any tty. */
#define AUTO_TTY ""
/* If supplied, attempt an automatic login with this username. */
static char *autologin_name = NULL;
/* Prompt for use with --prompt */
static char *prompt;
/*
* output error messages
*/
static void
error (const char *fmt,...)
{
va_list va_alist;
char buf[256], *bp;
#ifdef USE_SYSLOG
buf[0] = '\0';
bp = buf;
#else /* !USE_SYSLOG */
int fd;
strcpy (buf, progname);
strcat (buf, ": ");
bp = buf + strlen (buf);
#endif /* USE_SYSLOG */
va_start (va_alist, fmt);
vsprintf (bp, fmt, va_alist);
va_end (va_alist);
#ifdef USE_SYSLOG
openlog (progname, LOG_PID, LOG_AUTH);
syslog (LOG_ERR, buf);
closelog ();
#else /* !USE_SYSLOG */
strcat (bp, "\r\n");
if ((fd = open ("/dev/console", 1)) >= 0)
{
write (fd, buf, strlen (buf));
close (fd);
}
#endif /* USE_SYSLOG */
exit (1);
}
/*
* update_utmp - update our utmp entry
*
* The utmp file holds miscellaneous information about things started by
* /sbin/init and other system-related events. Our purpose is to update
* the utmp entry for the current process, in particular the process
* type and the tty line we are listening to. Return successfully only
* if the utmp file can be opened for update, and if we are able to find
* our entry in the utmp file.
*/
static void
update_utmp (void)
{
struct utmp ut;
int ut_fd;
struct utmp *utp;
void locktimeout (int);
utmpname (_PATH_UTMP);
setutent ();
while ((utp = getutent ()))
if (utp->ut_type == INIT_PROCESS && utp->ut_pid == pid)
break;
if (utp)
{
memcpy (&ut, utp, sizeof (ut));
}
else
{
/* some inits don't initialize utmp... */
/* XXX we should print out a warning message */
memset (&ut, 0, sizeof (ut));
strncpy (ut.ut_id, tty + 3, sizeof (ut.ut_id));
}
endutent ();
strncpy (ut.ut_user, "LOGIN", sizeof (ut.ut_user));
strncpy (ut.ut_line, tty, sizeof (ut.ut_line));
ut.ut_time = cur_time;
ut.ut_type = LOGIN_PROCESS;
ut.ut_pid = pid;
pututline (&ut);
endutent ();
if ((ut_fd = open (_PATH_WTMP, O_APPEND | O_WRONLY)) >= 0)
{
(void) signal (SIGALRM, locktimeout);
(void) alarm (3);
flock (ut_fd, LOCK_EX);
(void) alarm (0);
write (ut_fd, &ut, sizeof (ut));
flock (ut_fd, LOCK_UN);
close (ut_fd);
}
}
static void
output_special_char (unsigned char c)
{
switch (c)
{
case 's':
printf ("%s", uts.sysname);
break;
case 'n':
printf ("%s", uts.nodename);
break;
case 'r':
printf ("%s", uts.release);
break;
case 'v':
printf ("%s", uts.version);
break;
case 'm':
printf ("%s", uts.machine);
break;
case 'o':
#ifdef __USE_GNU
printf ("%s", uts.domainname);
#else
printf ("%s", uts.__domainname);
#endif
break;
case 'd':
case 't':
{
char buff[20];
struct tm *tm = localtime (&cur_time);
strftime (buff, sizeof (buff), c == 'd' ? "%a %b %d %Y" : "%X", tm);
fputs (buff, stdout);
break;
}
case 'l':
printf ("%s", tty);
break;
case 'u':
case 'U':
{
int users = 0;
struct utmp *ut;
setutent ();
while ((ut = getutent ()))
if (ut->ut_type == USER_PROCESS)
users++;
endutent ();
printf ("%d", users);
if (c == 'U')
printf (" user%s", users == 1 ? "" : "s");
break;
}
default:
putchar (c);
}
}
/* do_prompt - show login prompt, optionally preceded by /etc/issue contents */
static void
do_prompt (void)
{
FILE *fd;
signed int c;
write (1, "\n", 1); /* start a new line */
if ((fd = fopen (ISSUE, "r")))
{
while ((c = getc (fd)) != EOF)
{
if (c == '\\')
output_special_char (getc (fd));
else
putchar (c);
}
fflush (stdout);
fclose (fd);
}
write (1, hn, strlen (hn));
write (1, LOGIN, sizeof (LOGIN) - 1);
}
/* get_logname - get user name, establish speed, erase, kill, eol */
static char *
get_logname (void)
{
static char logname[40];
char *bp;
unsigned char c;
ioctl (0, TCFLSH, 0); /* flush pending input */
for (*logname = 0; *logname == 0;)
{
do_prompt ();
for (bp = logname;;)
{
if (read (0, &c, 1) < 1)
{
if (errno == EINTR || errno == EIO || errno == ENOENT)
exit (0);
error ("%s: read: %s", tty, sys_errlist[errno]);
}
if (c == '\n' || c == '\r')
{
*bp = 0;
break;
}
else if (!isprint (c))
error ("%s: invalid character %c in login name", tty, c);
else if (bp - logname >= sizeof (logname) - 1)
error ("%s: too long login name", tty);
else
*bp++ = c;
}
}
return logname;
}
static struct option const long_options[] =
{
{"noclear", no_argument, &noclear, 1},
{"long-hostname", no_argument, &longhostname, 1},
{"autologin", required_argument, NULL, 'a'},
{"prompt", optional_argument, NULL, 'p'},
{"path", required_argument, NULL, 'w'},
{"nice", required_argument, &priority, 'n'},
{0, 0, 0, 0}
};
void
locktimeout (int dummy)
{
#ifdef USE_SYSLOG
openlog (progname, LOG_PID, LOG_AUTH);
syslog (LOG_ALERT, "Lock failed on wtmp");
closelog ();
#else
int fd;
char buf[] = "Lock failed on wtmp\n";
if ((fd = open ("/dev/console", 1)) >= 0)
{
write (fd, buf, strlen (buf));
close (fd);
}
#endif
}
/*
* autologin_ok -- returns 1 if it's okay to auto-login when:
* this login is from /dev/tty1; and
* there was a login name passed with the --autologin option; and
* the autologin_name contains only "nice" characters; and
* this is the first autologin attempt since the last boot;
* return 0 otherwise.
*/
static int
autologin_ok (void)
{
char c, *cp;
int stat_err, fd;
struct sysinfo info;
struct stat sbuf;
/* Autologins are restricted to AUTO_TTY if non-empty. */
if (AUTO_TTY[0] && strcmp (tty, AUTO_TTY))
return 0;
/* An all-alphanumeric autologin name must be supplied. */
if (autologin_name == NULL || autologin_name[0] == '\0')
return 0;
for (cp = autologin_name; (c = *cp); cp++)
if (!isalnum (c) && c != '_')
return 0;
/* Get the uptime in info.uptime, and the last autologin time
in sbuf.st_mtime. */
sysinfo (&info);
stat_err = stat (AUTO_LAST, &sbuf);
/* If a stat error other than "no such file" occurs, I don't
know what went wrong, so I'll proceed with caution by
denying the autologin request. */
if (stat_err && errno != ENOENT)
return 0;
/* If there's been an autologin granted since the last boot,
deny this and any subsequent attempts. Note that this test
is skipped if the AUTO_LAST file doesn't exist. */
if (!stat_err && time (NULL) - info.uptime < sbuf.st_mtime)
return 0;
/* Create the AUTO_LAST file. The mtime of this file provides
a persistent record of the last time that an autologin
request was granted. Deny the autologin request if either
the file open or file close fails. */
if ((fd = open (AUTO_LAST, O_WRONLY | O_CREAT | O_TRUNC, 0644)) < 0)
return 0;
if (close (fd) != 0)
return 0;
/* All tests are okay, so grant the autologin request. */
return 1;
}
void
mingetty_login (char *logname, char *tty)
{
if (autologin_ok ())
{
execl (_PATH_LOGIN, _PATH_LOGIN, "-f", autologin_name, NULL);
}
else
{
while ((logname = get_logname ()) == 0);
execl (_PATH_LOGIN, _PATH_LOGIN, "--", logname, NULL);
}
error ("%s: can't exec " _PATH_LOGIN ": %s", tty, sys_errlist[errno]);
exit (0);
}
/* open_tty - set up tty as standard { input, output, error } */
static void
open_tty (void)
{
struct sigaction sa;
char buf[20];
int fd;
/* Set up new standard input. */
strcpy (buf, "/dev/");
strcat (buf, tty);
if (chown (buf, 0, 0) || chmod (buf, 0600))
error ("%s: %s", buf, sys_errlist[errno]);
sa.sa_handler = SIG_IGN;
sa.sa_flags = 0;
sigemptyset (&sa.sa_mask);
sigaction (SIGHUP, &sa, NULL);
/* vhangup() will replace all open file descriptors that point to our
controlling tty by a dummy that will deny further reading/writing
to our device. It will also reset the tty to sane defaults, so we
don't have to modify the tty device for sane settings.
We also get a SIGHUP/SIGCONT.
*/
if ((fd = open (buf, O_RDWR, 0)) < 0
|| ioctl (fd, TIOCSCTTY, (void *) 1) == -1)
error ("%s: cannot open tty: %s", buf, sys_errlist[errno]);
if (!isatty (fd))
error ("%s: not a tty", buf);
vhangup ();
/* Get rid of the present stdout/stderr. */
close (2);
close (1);
close (0);
close (fd);
/* ioctl (0, TIOCNOTTY, (char *)1); */
if (open (buf, O_RDWR, 0) != 0)
error ("%s: cannot open as standard input: %s", buf,
sys_errlist[errno]);
/* Set up standard output and standard error file descriptors. */
if (dup (0) != 1 || dup (0) != 2)
error ("%s: dup problem: %s", buf, sys_errlist[errno]);
/* Write a reset string to the terminal. This is very linux-specific
and should be checked for other systems. */
if (!noclear)
write (0, "\033[H\033[J", 6);
sa.sa_handler = SIG_DFL;
sa.sa_flags = 0;
sigemptyset (&sa.sa_mask);
sigaction (SIGHUP, &sa, NULL);
if (prompt_return)
{
write (1, prompt, strlen (prompt));
if (program_run)
{
write (1, "`", 1);
write (1, program_run, strlen (program_run));
write (1, "'", 1);
}
write (1, "\n", 1);
read (0, buf, 1);
}
#if DEBUG_THIS
printf ("session=%d, pid=%d, pgid=%d\n", getsid (0), getpid (), getpgid (0));
#endif
}
static void
usage (void)
{
error ("usage: '%s tty program'", progname);
}
/*
* main program
*/
int
main (int argc, char **argv)
{
char *logname, *s;
int c;
progname = argv[0];
uname (&uts);
gethostname (hn, MAXHOSTNAMELEN);
pid = getpid ();
time (&cur_time);
while ((c = getopt_long (argc, argv, "d:n:u:w:g:", long_options, (int *) 0)) != EOF)
{
switch (c)
{
case 0:
break;
case 'a':
autologin_name = optarg;
break;
case 'd':
delay = atoi (optarg);
break;
case 'g':
u_group = getgrnam (optarg);
break;
case 'n':
priority = atoi (optarg);
break;
case 'p':
if (optarg)
prompt = optarg;
else
prompt = PROMPT_RETURN;
prompt_return = 1;
break;
case 'u':
user = getpwnam (optarg);
break;
case 'w':
progpath = optarg;
break;
default:
usage ();
}
}
if (!longhostname && (s = strchr (hn, '.')))
*s = '\0';
if (!user)
user = getpwnam ("nobody");
if (!u_group)
u_group = getgrnam ("nogroup");
tty = argv[optind];
if (!tty)
usage ();
program_run = argv[optind + 1];
update_utmp ();
if (delay)
sleep (delay);
open_tty ();
#ifdef linux
putenv ("TERM=linux");
#else
putenv ("TERM=vt100");
#endif
/* disabled -- get path from init putenv ("PATH=/bin:/usr/bin:/usr/ucb:/usr/local/bin"); */
/* flush input and output queues, important for modems */
ioctl (0, TCFLSH, 2);
if (!program_run)
mingetty_login (logname, tty);
setgid (u_group->gr_gid);
initgroups (user->pw_name, user->pw_gid);
setuid (user->pw_uid);
if (progpath)
chdir (progpath);
nice (priority);
execvp (program_run, &argv[optind + 1]);
error ("%s: can't exec %s : %s", tty, program_run, sys_errlist[errno]);
exit (0);
}
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