shadow/libmisc/env.c

/*
 * Copyright (c) 1989 - 1992, Julianne Frances Haugh
 * Copyright (c) 1996 - 1999, Marek Michałkiewicz
 * Copyright (c) 2003 - 2005, Tomasz Kłoczko
 * Copyright (c) 2008       , Nicolas François
 * 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. The name of the copyright holders or contributors may not be used to
 *    endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 THE COPYRIGHT
 * HOLDERS 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 <config.h>

#ident "$Id$"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "prototypes.h"
#include "defines.h"
/*
 * NEWENVP_STEP must be a power of two.  This is the number
 * of (char *) pointers to allocate at a time, to avoid using
 * realloc() too often.
 */
#define NEWENVP_STEP 16
size_t newenvc = 0;
char **newenvp = NULL;
extern char **environ;

static const char *forbid[] = {
	"_RLD_=",
	"BASH_ENV=",		/* GNU creeping featurism strikes again... */
	"ENV=",
	"HOME=",
	"IFS=",
	"KRB_CONF=",
	"LD_",			/* anything with the LD_ prefix */
	"LIBPATH=",
	"MAIL=",
	"NLSPATH=",
	"PATH=",
	"SHELL=",
	"SHLIB_PATH=",
	(char *) 0
};

/* these are allowed, but with no slashes inside
   (to work around security problems in GNU gettext) */
static const char *noslash[] = {
	"LANG=",
	"LANGUAGE=",
	"LC_",			/* anything with the LC_ prefix */
	(char *) 0
};

/*
 * initenv() must be called once before using addenv().
 */
void initenv (void)
{
	newenvp = (char **) xmalloc (NEWENVP_STEP * sizeof (char *));
	*newenvp = NULL;
}


void addenv (const char *string, const char *value)
{
	char *cp, *newstring;
	size_t i;
	size_t n;

	if (value) {
		newstring = xmalloc (strlen (string) + strlen (value) + 2);
		sprintf (newstring, "%s=%s", string, value);
	} else {
		newstring = xstrdup (string);
	}

	/*
	 * Search for a '=' character within the string and if none is found
	 * just ignore the whole string.
	 */

	cp = strchr (newstring, '=');
	if (!cp) {
		free (newstring);
		return;
	}

	n = (size_t) (cp - newstring);

	for (i = 0; i < newenvc; i++) {
		if (strncmp (newstring, newenvp[i], n) == 0 &&
		    (newenvp[i][n] == '=' || newenvp[i][n] == '\0'))
			break;
	}

	if (i < newenvc) {
		free (newenvp[i]);
		newenvp[i] = newstring;
		return;
	}

	newenvp[newenvc++] = newstring;

	/*
	 * Check whether newenvc is a multiple of NEWENVP_STEP.
	 * If so we have to resize the vector.
	 * the expression (newenvc & (NEWENVP_STEP - 1)) == 0
	 * is equal to    (newenvc %  NEWENVP_STEP) == 0
	 * as long as NEWENVP_STEP is a power of 2.
	 */

	if ((newenvc & (NEWENVP_STEP - 1)) == 0) {
		char **__newenvp;
		size_t newsize;

		/*
		 * If the resize operation succeds we can
		 * happily go on, else print a message.
		 */

		newsize = (newenvc + NEWENVP_STEP) * sizeof (char *);
		__newenvp = (char **) realloc (newenvp, newsize);

		if (__newenvp) {
			/*
			 * If this is our current environment, update
			 * environ so that it doesn't point to some
			 * free memory area (realloc() could move it).
			 */
			if (environ == newenvp)
				environ = __newenvp;
			newenvp = __newenvp;
		} else {
			fputs (_("Environment overflow\n"), stderr);
			free (newenvp[--newenvc]);
		}
	}

	/*
	 * The last entry of newenvp must be NULL
	 */

	newenvp[newenvc] = NULL;
}


/*
 * set_env - copy command line arguments into the environment
 */
void set_env (int argc, char *const *argv)
{
	int noname = 1;
	char variable[1024];
	char *cp;

	for (; argc > 0; argc--, argv++) {
		if (strlen (*argv) >= sizeof variable)
			continue;	/* ignore long entries */

		if (!(cp = strchr (*argv, '='))) {
			snprintf (variable, sizeof variable, "L%d", noname++);
			addenv (variable, *argv);
		} else {
			const char **p;

			for (p = forbid; *p; p++)
				if (strncmp (*argv, *p, strlen (*p)) == 0)
					break;

			if (*p) {
				strncpy (variable, *argv, cp - *argv);
				variable[cp - *argv] = '\0';
				printf (_("You may not change $%s\n"),
					variable);
				continue;
			}

			addenv (*argv, NULL);
		}
	}
}

/*
 * sanitize_env - remove some nasty environment variables
 * If you fall into a total paranoia, you should call this
 * function for any root-setuid program or anything the user
 * might change the environment with. 99% useless as almost
 * all modern Unixes will handle setuid executables properly,
 * but... I feel better with that silly precaution. -j.
 */

void sanitize_env (void)
{
	char **envp = environ;
	const char **bad;
	char **cur;
	char **move;

	for (cur = envp; *cur; cur++) {
		for (bad = forbid; *bad; bad++) {
			if (strncmp (*cur, *bad, strlen (*bad)) == 0) {
				for (move = cur; *move; move++)
					*move = *(move + 1);
				cur--;
				break;
			}
		}
	}

	for (cur = envp; *cur; cur++) {
		for (bad = noslash; *bad; bad++) {
			if (strncmp (*cur, *bad, strlen (*bad)) != 0)
				continue;
			if (!strchr (*cur, '/'))
				continue;	/* OK */
			for (move = cur; *move; move++)
				*move = *(move + 1);
			cur--;
			break;
		}
	}
}