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 (17 kb)"
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_NOEXEC(sulogin, sulogin, BB_DIR_SBIN, BB_SUID_DROP, sulogin))
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;
sulogin_main(int argc UNUSED_PARAM,char ** argv)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 /* Note: sulogin is not a suid app. It is meant to be run by init
36 * for single user / emergency mode. init starts it as root.
37 * Normal users (potentially malicious ones) can only run it under
38 * their UID, therefore no paranoia here is warranted:
39 * $LD_LIBRARY_PATH in env, TTY = /dev/sda
40 * are no more dangerous here than in e.g. cp applet.
41 */
42
43 logmode = LOGMODE_BOTH;
44 openlog(applet_name, 0, LOG_AUTH);
45
46 getopt32(argv, "t:+", &timeout);
47 argv += optind;
48
49 if (argv[0]) {
50 close(0);
51 close(1);
52 dup(xopen(argv[0], O_RDWR));
53 close(2);
54 dup(0);
55 }
56
57 pwd = getpwuid(0);
58 if (!pwd) {
59 bb_simple_error_msg_and_die("no password entry for root");
60 }
61
62 while (1) {
63 int r;
64
65 r = ask_and_check_password_extended(pwd, timeout,
66 "Give root password for system maintenance\n"
67 "(or type Control-D for normal startup):"
68 );
69 if (r < 0) {
70 /* ^D, ^C, timeout, or read error */
71 bb_simple_info_msg("normal startup");
72 return 0;
73 }
74 if (r > 0) {
75 break;
76 }
77 pause_after_failed_login();
78 bb_simple_info_msg("Login incorrect");
79 }
80
81 bb_simple_info_msg("starting shell for system maintenance");
82
83 IF_SELINUX(renew_current_security_context());
84
85 shell = getenv("SUSHELL");
86 if (!shell)
87 shell = getenv("sushell");
88 if (!shell)
89 shell = pwd->pw_shell;
90
91 /* Exec login shell with no additional parameters. Never returns. */
92 exec_login_shell(shell);
93 }
94