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/* vi: set sw=4 ts=4: */
/*
* Mini sulogin implementation for busybox
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config SULOGIN
//config: bool "sulogin (18 kb)"
//config: default y
//config: select FEATURE_SYSLOG
//config: help
//config: sulogin is invoked when the system goes into single user
//config: mode (this is done through an entry in inittab).
//applet:IF_SULOGIN(APPLET_NOEXEC(sulogin, sulogin, BB_DIR_SBIN, BB_SUID_DROP, sulogin))
//kbuild:lib-$(CONFIG_SULOGIN) += sulogin.o
//usage:#define sulogin_trivial_usage
//usage: "[-t N] [TTY]"
//usage:#define sulogin_full_usage "\n\n"
//usage: "Single user login\n"
//usage: "\n -p Start a login shell"
//usage: "\n -t SEC Timeout"
#include "libbb.h"
#include <syslog.h>
int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sulogin_main(int argc UNUSED_PARAM, char **argv)
{
int tsid;
int timeout = 0;
unsigned opts;
struct passwd *pwd;
const char *shell;
/* Note: sulogin is not a suid app. It is meant to be run by init
* for single user / emergency mode. init starts it as root.
* Normal users (potentially malicious ones) can only run it under
* their UID, therefore no paranoia here is warranted:
* $LD_LIBRARY_PATH in env, TTY = /dev/sda
* are no more dangerous here than in e.g. cp applet.
*/
logmode = LOGMODE_BOTH;
openlog(applet_name, 0, LOG_AUTH);
opts = getopt32(argv, "pt:+", &timeout);
argv += optind;
if (argv[0]) {
close(0);
close(1);
dup(xopen(argv[0], O_RDWR));
close(2);
dup(0);
}
pwd = getpwuid(0);
if (!pwd) {
bb_simple_error_msg_and_die("no password entry for root");
}
while (1) {
int r;
r = ask_and_check_password_extended(pwd, timeout,
"Give root password for maintenance\n"
"(or type Ctrl-D to continue): "
);
if (r < 0) {
/* ^D, ^C, timeout, or read error */
/* util-linux 2.36.1 compat: no message */
/*bb_simple_info_msg("normal startup");*/
return 0;
}
if (r > 0) {
break;
}
pause_after_failed_login();
bb_simple_error_msg("Login incorrect");
}
/* util-linux 2.36.1 compat: no message */
/*bb_simple_info_msg("starting shell for system maintenance");*/
IF_SELINUX(renew_current_security_context());
shell = getenv("SUSHELL");
if (!shell)
shell = getenv("sushell");
if (!shell)
shell = pwd->pw_shell;
/* util-linux 2.36.1 compat: cd to root's HOME, set a few envvars */
setup_environment(shell, 0
+ SETUP_ENV_CHANGEENV_LOGNAME
+ SETUP_ENV_CHDIR
, pwd);
// no SETUP_ENV_CLEARENV
// SETUP_ENV_CHANGEENV_LOGNAME - set HOME, SHELL, USER,and LOGNAME
// SETUP_ENV_CHDIR - cd to $HOME
/* util-linux 2.36.1 compat: steal ctty if we don't have it yet
* (yes, util-linux uses force=1) */
tsid = tcgetsid(STDIN_FILENO);
if (tsid < 0 || getpid() != tsid) {
if (ioctl(STDIN_FILENO, TIOCSCTTY, /*force:*/ (long)1) != 0) {
// bb_perror_msg("TIOCSCTTY1 tsid:%d", tsid);
if (setsid() > 0) {
// bb_error_msg("done setsid()");
/* If it still does not work, ignore */
if (ioctl(STDIN_FILENO, TIOCSCTTY, /*force:*/ (long)1) != 0) {
// bb_perror_msg("TIOCSCTTY2 tsid:%d", tsid);
}
}
}
}
/*
* Note: login does this. util-linux's sulogin does NOT.
* But it's rather unpleasant to have non-functioning ^C in a shell,
* and surprisingly, there is no easy way to remove SIG_IGN from ^C
* in the shell. So, we are doing it:
*/
signal(SIGINT, SIG_DFL);
/* Exec shell with no additional parameters. Never returns. */
exec_shell(shell, /* -p? then shell is login:*/(opts & 1), NULL);
}
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