blob: 2e32e2bbdff1fd9de04fc93a08c6c23196a6c364
| 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 | /* 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 malisious 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_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_error_msg("normal startup"); |
| 72 | return 0; |
| 73 | } |
| 74 | if (r > 0) { |
| 75 | break; |
| 76 | } |
| 77 | bb_do_delay(LOGIN_FAIL_DELAY); |
| 78 | bb_error_msg("Login incorrect"); |
| 79 | } |
| 80 | |
| 81 | bb_error_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 | run_shell(shell, 1, NULL); |
| 93 | } |
| 94 |