busybox/libbb/run_shell.c

/* vi: set sw=4 ts=4: */
/*
 * Copyright 1989 - 1991, Julianne Frances Haugh <jockgrrl@austin.rr.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Julianne F. Haugh nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ''AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#include "libbb.h"
#if ENABLE_SELINUX
#include <selinux/selinux.h>  /* for setexeccon  */
#endif

#if ENABLE_SELINUX
static security_context_t current_sid;

void FAST_FUNC renew_current_security_context(void)
{
	freecon(current_sid);  /* Release old context  */
	getcon(&current_sid);  /* update */
}
void FAST_FUNC set_current_security_context(security_context_t sid)
{
	freecon(current_sid);  /* Release old context  */
	current_sid = sid;
}

#endif

/* Exec SHELL, or DEFAULT_SHELL if SHELL is "" or NULL.
 * If ADDITIONAL_ARGS is not NULL, pass them to the shell.
 */
void FAST_FUNC exec_shell(const char *shell, int loginshell, const char **additional_args)
{
	const char **args;

	args = additional_args;
	while (args && *args)
		args++;

	args = xzalloc(sizeof(args[0]) * (2 + (args - additional_args)));

	if (!shell || !shell[0])
		shell = DEFAULT_SHELL;

	args[0] = bb_get_last_path_component_nostrip(shell);
	if (loginshell)
		args[0] = xasprintf("-%s", args[0]);
	/*args[1] = NULL; - already is */
	if (additional_args) {
		int cnt = 0;
		while (*additional_args)
			args[++cnt] = *additional_args++;
	}

#if ENABLE_SELINUX
	if (current_sid)
		setexeccon(current_sid);
	if (ENABLE_FEATURE_CLEAN_UP)
		freecon(current_sid);
#endif
	execv(shell, (char **) args);
	bb_perror_msg_and_die("can't execute '%s'", shell);
}

void FAST_FUNC exec_login_shell(const char *shell)
{
	exec_shell(shell, 1, NULL);
}

/* Typical idiom for applets which exec *optional* PROG [ARGS] */
void FAST_FUNC exec_prog_or_SHELL(char **argv)
{
	if (argv[0]) {
		BB_EXECVP_or_die(argv);
	}
	/* Both users (nsenter and unshare) do indeed exec
	 * a _login_ shell (with dash in argv[0])!
	 */
	exec_login_shell(getenv("SHELL"));
}