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f9efe8694a
This function removes all environment variables except
the ones listed on a "whitelist."
The function accepts two whitelist arguments.
If the first is NULL, a built-in default list will be
used. This allows callers to get a variety of behaviors:
* Default screening: provide NULL for both lists
* Custom screening: provide a custom list for the first argument
* Modified default screening: provide NULL for first arg,
list of additional variables to preserve in the second arg
Idea from: Jacques Vidrine
MFC after: 2 weeks
121 lines
3.8 KiB
C
121 lines
3.8 KiB
C
/*-
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* Copyright (c) 2004 Tim Kientzle
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <string.h>
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#include "libutil.h"
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static int env_var_in_list(const char * const *list, char *var, size_t len);
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/*
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* Default whitelist of "known safe" environment variables.
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*/
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static const char *default_whitelist[] = {
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/* List from SUS "Environment Variables" Appendix */
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"ARFLAGS", "CC", "CDPATH", "CFLAGS", "CHARSET", "COLUMNS",
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"DATEMSK", "DEAD", "EDITOR", "ENV", "EXINIT", "FC", "FCEDIT",
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"FFLAGS", "GET", "GFLAGS", "HISTFILE", "HISTORY", "HISTSIZE",
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"HOME", "IFS", "LANG", "LC_ALL", "LC_COLLATE", "LC_CTYPE",
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"LC_MESSAGES", "LC_MONETARY", "LC_NUMERIC", "LC_TIME", "LDFLAGS",
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"LEX", "LFLAGS", "LINENO", "LINES", "LISTER", "LOGNAME", "LPDEST",
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"MAIL", "MAILCHECK", "MAILER", "MAILPATH", "MAILRC", "MAKEFLAGS",
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"MAKESHELL", "MANPATH", "MBOX", "MORE", "MSGVERB", "NLSPATH",
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"NPROC", "OLDPWD", "OPTARG", "OPTERR", "OPTIND", "PAGER", "PATH",
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"PPID", "PRINTER", "PROCLANG", "PROJECTDIR", "PS1", "PS2", "PS3",
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"PS4", "PWD", "RANDOM", "SECONDS", "SHELL", "TERM", "TERMCAP",
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"TERMINFO", "TMPDIR", "TZ", "USER", "VISUAL", "YACC", "YFLAGS",
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/* Additional Environment Variables */
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"KRB5CCNAME", "LOGIN", "MAILDIR", "SSH_AGENT_PID", "SSH_AUTH_SOCK",
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/* Terminating NULL */
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NULL
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};
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static int
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env_var_in_list(const char * const *list, char *var, size_t len)
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{
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if (list == NULL)
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return (0);
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while (*list != NULL) {
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if (strncmp(var, *list, len) == 0 &&
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len == strlen(*list))
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return (1);
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list++;
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}
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return (0);
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}
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/*
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* Scrub the environment by applying a "whitelist" of safe variables
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* and a "blacklist" of known dangerous variables. Each environment
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* variable is examined and is retained only if it appears in a whitelist
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* and does not appear in the blacklist.
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*
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* If the first argument is NULL, a built-in whitelist will be used.
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* The second and third arguments allow clients to adjust the built-in
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* whitelist without having to replicate it.
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*
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*/
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void
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clean_environment(const char * const *whitelist,
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const char * const *extra_whitelist)
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{
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extern char **environ;
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char *p, **new, **old;
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int len;
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int safe;
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old = environ;
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new = environ;
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if (whitelist == NULL)
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whitelist = default_whitelist;
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while (*old != NULL) {
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safe = 0;
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p = strchr(*old, '=');
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if (p != NULL)
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len = p - *old;
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else
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len = strlen(*old);
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if (env_var_in_list(whitelist, *old, len) ||
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env_var_in_list(extra_whitelist, *old, len))
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*new++ = *old;
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old++;
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}
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while (*new != NULL)
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*new++ = NULL;
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}
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