1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Mini sulogin implementation for busybox
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4 | *
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5 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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6 | */
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7 | //config:config SULOGIN
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8 | //config: bool "sulogin"
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9 | //config: default y
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10 | //config: select FEATURE_SYSLOG
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11 | //config: help
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12 | //config: sulogin is invoked when the system goes into single user
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13 | //config: mode (this is done through an entry in inittab).
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14 |
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15 | //applet:IF_SULOGIN(APPLET(sulogin, BB_DIR_SBIN, BB_SUID_DROP))
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16 |
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17 | //kbuild:lib-$(CONFIG_SULOGIN) += sulogin.o
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18 |
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19 | //usage:#define sulogin_trivial_usage
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20 | //usage: "[-t N] [TTY]"
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21 | //usage:#define sulogin_full_usage "\n\n"
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22 | //usage: "Single user login\n"
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23 | //usage: "\n -t N Timeout"
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24 |
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25 | #include "libbb.h"
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26 | #include <syslog.h>
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27 |
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28 | int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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29 | int sulogin_main(int argc UNUSED_PARAM, char **argv)
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30 | {
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31 | int timeout = 0;
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32 | struct passwd *pwd;
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33 | const char *shell;
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34 |
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35 | /* Note: sulogin is not a suid app. It is meant to be run by init
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36 | * for single user / emergency mode. init starts it as root.
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37 | * Normal users (potentially malisious ones) can only run it under
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38 | * their UID, therefore no paranoia here is warranted:
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39 | * $LD_LIBRARY_PATH in env, TTY = /dev/sda
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40 | * are no more dangerous here than in e.g. cp applet.
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41 | */
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42 |
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43 | logmode = LOGMODE_BOTH;
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44 | openlog(applet_name, 0, LOG_AUTH);
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45 |
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46 | opt_complementary = "t+"; /* -t N */
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47 | getopt32(argv, "t:", &timeout);
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48 | argv += optind;
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49 |
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50 | if (argv[0]) {
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51 | close(0);
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52 | close(1);
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53 | dup(xopen(argv[0], O_RDWR));
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54 | close(2);
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55 | dup(0);
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56 | }
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57 |
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58 | pwd = getpwuid(0);
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59 | if (!pwd) {
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60 | bb_error_msg_and_die("no password entry for root");
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61 | }
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62 |
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63 | while (1) {
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64 | int r;
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65 |
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66 | r = ask_and_check_password_extended(pwd, timeout,
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67 | "Give root password for system maintenance\n"
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68 | "(or type Control-D for normal startup):"
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69 | );
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70 | if (r < 0) {
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71 | /* ^D, ^C, timeout, or read error */
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72 | bb_error_msg("normal startup");
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73 | return 0;
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74 | }
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75 | if (r > 0) {
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76 | break;
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77 | }
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78 | bb_do_delay(LOGIN_FAIL_DELAY);
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79 | bb_error_msg("Login incorrect");
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80 | }
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81 |
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82 | bb_error_msg("starting shell for system maintenance");
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83 |
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84 | IF_SELINUX(renew_current_security_context());
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85 |
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86 | shell = getenv("SUSHELL");
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87 | if (!shell)
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88 | shell = getenv("sushell");
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89 | if (!shell)
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90 | shell = pwd->pw_shell;
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91 |
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92 | /* Exec login shell with no additional parameters. Never returns. */
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93 | run_shell(shell, 1, NULL, NULL);
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94 | }
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