loginutils/sulogin.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini sulogin implementation for busybox
   4  *
   5  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   6  */
   7 //config:config SULOGIN
   8 //config:       bool "sulogin"
   9 //config:       default y
  10 //config:       select FEATURE_SYSLOG
  11 //config:       help
  12 //config:         sulogin is invoked when the system goes into single user
  13 //config:         mode (this is done through an entry in inittab).
  14
  15 //applet:IF_SULOGIN(APPLET(sulogin, BB_DIR_SBIN, BB_SUID_DROP))
  16
  17 //kbuild:lib-$(CONFIG_SULOGIN) += sulogin.o
  18
  19 //usage:#define sulogin_trivial_usage
  20 //usage:       "[-t N] [TTY]"
  21 //usage:#define sulogin_full_usage "\n\n"
  22 //usage:       "Single user login\n"
  23 //usage:     "\n        -t N    Timeout"
  24
  25 #include "libbb.h"
  26 #include <syslog.h>
  27
  28 int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  29 int sulogin_main(int argc UNUSED_PARAM, char **argv)
  30 {
  31         int timeout = 0;
  32         struct passwd *pwd;
  33         const char *shell;
  34
  35         logmode = LOGMODE_BOTH;
  36         openlog(applet_name, 0, LOG_AUTH);
  37
  38         opt_complementary = "t+"; /* -t N */
  39         getopt32(argv, "t:", &timeout);
  40         argv += optind;
  41
  42         if (argv[0]) {
  43                 close(0);
  44                 close(1);
  45                 dup(xopen(argv[0], O_RDWR));
  46                 close(2);
  47                 dup(0);
  48         }
  49
  50         /* Malicious use like "sulogin /dev/sda"? */
  51         if (!isatty(0) || !isatty(1) || !isatty(2)) {
  52                 logmode = LOGMODE_SYSLOG;
  53                 bb_error_msg_and_die("not a tty");
  54         }
  55
  56         /* Clear dangerous stuff, set PATH */
  57         sanitize_env_if_suid();
  58
  59         pwd = getpwuid(0);
  60         if (!pwd) {
  61                 goto auth_error;
  62         }
  63
  64         while (1) {
  65                 int r;
  66
  67                 r = ask_and_check_password_extended(pwd, timeout,
  68                         "Give root password for system maintenance\n"
  69                         "(or type Control-D for normal startup):"
  70                 );
  71                 if (r < 0) {
  72                         /* ^D, ^C, timeout, or read error */
  73                         bb_info_msg("Normal startup");
  74                         return 0;
  75                 }
  76                 if (r > 0) {
  77                         break;
  78                 }
  79                 bb_do_delay(LOGIN_FAIL_DELAY);
  80                 bb_info_msg("Login incorrect");
  81         }
  82
  83         bb_info_msg("System Maintenance Mode");
  84
  85         IF_SELINUX(renew_current_security_context());
  86
  87         shell = getenv("SUSHELL");
  88         if (!shell)
  89                 shell = getenv("sushell");
  90         if (!shell)
  91                 shell = pwd->pw_shell;
  92
  93         /* Exec login shell with no additional parameters. Never returns. */
  94         run_shell(shell, 1, NULL, NULL);
  95
  96  auth_error:
  97         bb_error_msg_and_die("no password entry for root");
  98 }