busybox/loginutils/sulogin.c

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/* vi: set sw=4 ts=4: */
/*
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* Mini sulogin implementation for busybox
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config SULOGIN
//config: bool "sulogin"
//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:/* Needs to be run by root or be suid root - needs to change uid and gid: */
//applet:IF_SULOGIN(APPLET(sulogin, BB_DIR_SBIN, BB_SUID_DROP))
//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;
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int sulogin_main(int argc UNUSED_PARAM, char **argv)
{
int timeout = 0;
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struct passwd *pwd;
const char *shell;
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logmode = LOGMODE_BOTH;
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openlog(applet_name, 0, LOG_AUTH);
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opt_complementary = "t+"; /* -t N */
getopt32(argv, "t:", &timeout);
argv += optind;
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if (argv[0]) {
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close(0);
close(1);
dup(xopen(argv[0], O_RDWR));
close(2);
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dup(0);
}
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/* Malicious use like "sulogin /dev/sda"? */
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if (!isatty(0) || !isatty(1) || !isatty(2)) {
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logmode = LOGMODE_SYSLOG;
bb_error_msg_and_die("not a tty");
}
/* Clear dangerous stuff, set PATH */
sanitize_env_if_suid();
pwd = getpwuid(0);
if (!pwd) {
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goto auth_error;
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}
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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 */
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bb_info_msg("Normal startup");
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return 0;
}
if (r > 0) {
break;
}
bb_do_delay(LOGIN_FAIL_DELAY);
bb_info_msg("Login incorrect");
}
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bb_info_msg("System Maintenance Mode");
IF_SELINUX(renew_current_security_context());
shell = getenv("SUSHELL");
if (!shell)
shell = getenv("sushell");
if (!shell)
shell = pwd->pw_shell;
/* Exec login shell with no additional parameters. Never returns. */
run_shell(shell, 1, NULL, NULL);
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auth_error:
bb_error_msg_and_die("no password entry for root");
}