busybox/libbb/change_identity.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"

/* Become the user and group(s) specified by PW.  */
void FAST_FUNC change_identity(const struct passwd *pw)
{
	int res;

	res = initgroups(pw->pw_name, pw->pw_gid);
	endgrent(); /* helps to close a fd used internally by libc */

	if (res != 0) {
		/*
		 * If initgroups() fails because a system call is unimplemented
		 * then we are running on a Linux kernel compiled without multiuser
		 * support (CONFIG_MULTIUSER is not defined).
		 *
		 * If we are running without multiuser support *and* the target uid
		 * already matches the current uid then we can skip the change of
		 * identity.
		 */
		if (errno == ENOSYS && pw->pw_uid == getuid()) {
			return;
		}

		bb_perror_msg_and_die("can't set groups");
	}

	xsetgid(pw->pw_gid);
	xsetuid(pw->pw_uid);
}