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 28int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 29int 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