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 tarball for details.
   6  */
   7
   8 #include <syslog.h>
   9
  10 #include "busybox.h"
  11
  12 static const char * const forbid[] = {
  13         "ENV",
  14         "BASH_ENV",
  15         "HOME",
  16         "IFS",
  17         "PATH",
  18         "SHELL",
  19         "LD_LIBRARY_PATH",
  20         "LD_PRELOAD",
  21         "LD_TRACE_LOADED_OBJECTS",
  22         "LD_BIND_NOW",
  23         "LD_AOUT_LIBRARY_PATH",
  24         "LD_AOUT_PRELOAD",
  25         "LD_NOWARN",
  26         "LD_KEEPDIR",
  27         (char *) 0
  28 };
  29
  30
  31 static void catchalarm(int ATTRIBUTE_UNUSED junk)
  32 {
  33         exit(EXIT_FAILURE);
  34 }
  35
  36
  37 int sulogin_main(int argc, char **argv)
  38 {
  39         char *cp;
  40         int timeout = 0;
  41         char *timeout_arg;
  42         const char * const *p;
  43         struct passwd *pwd;
  44         const char *shell;
  45
  46         logmode = LOGMODE_BOTH;
  47         openlog(applet_name, 0, LOG_AUTH);
  48
  49         if (getopt32(argc, argv, "t:", &timeout_arg)) {
  50                 timeout = xatoi_u(timeout_arg);
  51         }
  52
  53         if (argv[optind]) {
  54                 close(0);
  55                 close(1);
  56                 dup(xopen(argv[optind], O_RDWR));
  57                 close(2);
  58                 dup(0);
  59         }
  60
  61         if (!isatty(0) || !isatty(1) || !isatty(2)) {
  62                 logmode = LOGMODE_SYSLOG;
  63                 bb_error_msg_and_die("not a tty");
  64         }
  65
  66         /* Clear out anything dangerous from the environment */
  67         for (p = forbid; *p; p++)
  68                 unsetenv(*p);
  69
  70         signal(SIGALRM, catchalarm);
  71
  72         pwd = getpwuid(0);
  73         if (!pwd) {
  74                 goto auth_error;
  75         }
  76
  77 #if ENABLE_FEATURE_SHADOWPASSWDS
  78         {
  79                 struct spwd *spwd = getspnam(pwd->pw_name);
  80                 if (!spwd) {
  81                         goto auth_error;
  82                 }
  83                 pwd->pw_passwd = spwd->sp_pwdp;
  84         }
  85 #endif
  86
  87         while (1) {
  88                 /* cp points to a static buffer that is zeroed every time */
  89                 cp = bb_askpass(timeout,
  90                                 "Give root password for system maintenance\n"
  91                                 "(or type Control-D for normal startup):");
  92
  93                 if (!cp || !*cp) {
  94                         bb_info_msg("Normal startup");
  95                         return 0;
  96                 }
  97                 if (strcmp(pw_encrypt(cp, pwd->pw_passwd), pwd->pw_passwd) == 0) {
  98                         break;
  99                 }
 100                 bb_do_delay(FAIL_DELAY);
 101                 bb_error_msg("login incorrect");
 102         }
 103         memset(cp, 0, strlen(cp));
 104         signal(SIGALRM, SIG_DFL);
 105
 106         bb_info_msg("System Maintenance Mode");
 107
 108         USE_SELINUX(renew_current_security_context());
 109
 110         shell = getenv("SUSHELL");
 111         if (!shell) shell = getenv("sushell");
 112         if (!shell) {
 113                 shell = "/bin/sh";
 114                 if (pwd->pw_shell[0])
 115                         shell = pwd->pw_shell;
 116         }
 117         run_shell(shell, 1, 0, 0);
 118         /* never returns */
 119
 120 auth_error:
 121         bb_error_msg_and_die("no password entry for 'root'");
 122 }