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
   8 //usage:#define sulogin_trivial_usage
   9 //usage:       "[-t N] [TTY]"
  10 //usage:#define sulogin_full_usage "\n\n"
  11 //usage:       "Single user login\n"
  12 //usage:     "\n        -t N    Timeout"
  13
  14 #include "libbb.h"
  15 #include <syslog.h>
  16
  17 //static void catchalarm(int UNUSED_PARAM junk)
  18 //{
  19 //      exit(EXIT_FAILURE);
  20 //}
  21
  22
  23 int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  24 int sulogin_main(int argc UNUSED_PARAM, char **argv)
  25 {
  26         char *cp;
  27         int timeout = 0;
  28         struct passwd *pwd;
  29         const char *shell;
  30 #if ENABLE_FEATURE_SHADOWPASSWDS
  31         /* Using _r function to avoid pulling in static buffers */
  32         char buffer[256];
  33         struct spwd spw;
  34 #endif
  35
  36         logmode = LOGMODE_BOTH;
  37         openlog(applet_name, 0, LOG_AUTH);
  38
  39         opt_complementary = "t+"; /* -t N */
  40         getopt32(argv, "t:", &timeout);
  41         argv += optind;
  42
  43         if (argv[0]) {
  44                 close(0);
  45                 close(1);
  46                 dup(xopen(argv[0], O_RDWR));
  47                 close(2);
  48                 dup(0);
  49         }
  50
  51         /* Malicious use like "sulogin /dev/sda"? */
  52         if (!isatty(0) || !isatty(1) || !isatty(2)) {
  53                 logmode = LOGMODE_SYSLOG;
  54                 bb_error_msg_and_die("not a tty");
  55         }
  56
  57         /* Clear dangerous stuff, set PATH */
  58         sanitize_env_if_suid();
  59
  60         pwd = getpwuid(0);
  61         if (!pwd) {
  62                 goto auth_error;
  63         }
  64
  65 #if ENABLE_FEATURE_SHADOWPASSWDS
  66         {
  67                 /* getspnam_r may return 0 yet set result to NULL.
  68                  * At least glibc 2.4 does this. Be extra paranoid here. */
  69                 struct spwd *result = NULL;
  70                 int r = getspnam_r(pwd->pw_name, &spw, buffer, sizeof(buffer), &result);
  71                 if (r || !result) {
  72                         goto auth_error;
  73                 }
  74                 pwd->pw_passwd = result->sp_pwdp;
  75         }
  76 #endif
  77
  78         while (1) {
  79                 char *encrypted;
  80                 int r;
  81
  82                 /* cp points to a static buffer that is zeroed every time */
  83                 cp = bb_ask(STDIN_FILENO, timeout,
  84                                 "Give root password for system maintenance\n"
  85                                 "(or type Control-D for normal startup):");
  86
  87                 if (!cp || !*cp) {
  88                         bb_info_msg("Normal startup");
  89                         return 0;
  90                 }
  91                 encrypted = pw_encrypt(cp, pwd->pw_passwd, 1);
  92                 r = strcmp(encrypted, pwd->pw_passwd);
  93                 free(encrypted);
  94                 if (r == 0) {
  95                         break;
  96                 }
  97                 bb_do_delay(LOGIN_FAIL_DELAY);
  98                 bb_info_msg("Login incorrect");
  99         }
 100         memset(cp, 0, strlen(cp));
 101 //      signal(SIGALRM, SIG_DFL);
 102
 103         bb_info_msg("System Maintenance Mode");
 104
 105         IF_SELINUX(renew_current_security_context());
 106
 107         shell = getenv("SUSHELL");
 108         if (!shell)
 109                 shell = getenv("sushell");
 110         if (!shell)
 111                 shell = pwd->pw_shell;
 112
 113         /* Exec login shell with no additional parameters. Never returns. */
 114         run_shell(shell, 1, NULL, NULL);
 115
 116  auth_error:
 117         bb_error_msg_and_die("no password entry for root");
 118 }