loginutils/sulogin.c

/* vi: set sw=4 ts=4: */
/*
 * Mini sulogin implementation for busybox
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//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>

//static void catchalarm(int UNUSED_PARAM junk)
//{
//	exit(EXIT_FAILURE);
//}


int sulogin_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sulogin_main(int argc UNUSED_PARAM, char **argv)
{
	char *cp;
	int timeout = 0;
	struct passwd *pwd;
	const char *shell;
#if ENABLE_FEATURE_SHADOWPASSWDS
	/* Using _r function to avoid pulling in static buffers */
	char buffer[256];
	struct spwd spw;
#endif

	logmode = LOGMODE_BOTH;
	openlog(applet_name, 0, LOG_AUTH);

	opt_complementary = "t+"; /* -t N */
	getopt32(argv, "t:", &timeout);
	argv += optind;

	if (argv[0]) {
		close(0);
		close(1);
		dup(xopen(argv[0], O_RDWR));
		close(2);
		dup(0);
	}

	/* Malicious use like "sulogin /dev/sda"? */
	if (!isatty(0) || !isatty(1) || !isatty(2)) {
		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) {
		goto auth_error;
	}

#if ENABLE_FEATURE_SHADOWPASSWDS
	{
		/* getspnam_r may return 0 yet set result to NULL.
		 * At least glibc 2.4 does this. Be extra paranoid here. */
		struct spwd *result = NULL;
		int r = getspnam_r(pwd->pw_name, &spw, buffer, sizeof(buffer), &result);
		if (r || !result) {
			goto auth_error;
		}
		pwd->pw_passwd = result->sp_pwdp;
	}
#endif

	while (1) {
		char *encrypted;
		int r;

		/* cp points to a static buffer that is zeroed every time */
		cp = bb_ask(STDIN_FILENO, timeout,
				"Give root password for system maintenance\n"
				"(or type Control-D for normal startup):");

		if (!cp || !*cp) {
			bb_info_msg("Normal startup");
			return 0;
		}
		encrypted = pw_encrypt(cp, pwd->pw_passwd, 1);
		r = strcmp(encrypted, pwd->pw_passwd);
		free(encrypted);
		if (r == 0) {
			break;
		}
		bb_do_delay(LOGIN_FAIL_DELAY);
		bb_info_msg("Login incorrect");
	}
	memset(cp, 0, strlen(cp));
//	signal(SIGALRM, SIG_DFL);

	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);

 auth_error:
	bb_error_msg_and_die("no password entry for root");
}