busybox/libbb/setup_environment.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"

/* util-linux manpage says /sbin:/bin:/usr/sbin:/usr/bin,
 * but I want to save a few bytes here */
static const char DEFAULT_ROOT_LOGIN_PATH[] = "/sbin:/usr/sbin:/bin:/usr/bin";
#define DEFAULT_LOGIN_PATH (DEFAULT_ROOT_LOGIN_PATH + sizeof("/sbin:/usr/sbin"))

void setup_environment(const char *shell, int loginshell, int changeenv, const struct passwd *pw)
{
	if (loginshell) {
		const char *term;

		/* Change the current working directory to be the home directory
		 * of the user.  It is a fatal error for this process to be unable
		 * to change to that directory.  There is no "default" home
		 * directory.
		 * Some systems default to HOME=/
		 */
		if (chdir(pw->pw_dir)) {
			xchdir("/");
			fputs("warning: cannot change to home directory\n", stderr);
		}

		/* Leave TERM unchanged.  Set HOME, SHELL, USER, LOGNAME, PATH.
		   Unset all other environment variables.  */
		term = getenv("TERM");
		clearenv();
		if (term)
			xsetenv("TERM", term);
		xsetenv("HOME",    pw->pw_dir);
		xsetenv("SHELL",   shell);
		xsetenv("USER",    pw->pw_name);
		xsetenv("LOGNAME", pw->pw_name);
		xsetenv("PATH",   (pw->pw_uid ? DEFAULT_LOGIN_PATH : DEFAULT_ROOT_LOGIN_PATH));
	}
	else if (changeenv) {
		/* Set HOME, SHELL, and if not becoming a super-user,
		   USER and LOGNAME.  */
		xsetenv("HOME",  pw->pw_dir);
		xsetenv("SHELL", shell);
		if (pw->pw_uid) {
			xsetenv("USER",    pw->pw_name);
			xsetenv("LOGNAME", pw->pw_name);
		}
	}
}