busybox/loginutils/sulogin.c
Denys Vlasenko 68b402ee51 ash: ^C with SIG_INGed SIGINT should not exit the shell
function                                             old     new   delta
__pgetc                                              501     522     +21

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2022-01-13 01:15:10 +01:00

122 lines
3.2 KiB
C

/* 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 (17 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 -t N 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;
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);
getopt32(argv, "t:+", &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 system maintenance\n"
"(or type Control-D for normal startup):"
);
if (r < 0) {
/* ^D, ^C, timeout, or read error */
bb_simple_info_msg("normal startup");
return 0;
}
if (r > 0) {
break;
}
pause_after_failed_login();
bb_simple_info_msg("Login incorrect");
}
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, SETUP_ENV_CHANGEENV | SETUP_ENV_CHANGEENV_LOGNAME, pwd);
// no SETUP_ENV_CLEARENV
// SETUP_ENV_CHANGEENV[+LOGNAME] - set HOME, SHELL, USER,and LOGNAME
// no SETUP_ENV_NO_CHDIR - IOW: 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 (should we do it too?):
*/
/*signal(SIGINT, SIG_DFL);*/
/* Exec login shell with no additional parameters. Never returns. */
exec_login_shell(shell);
}