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https://github.com/slicer69/doas
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![Jesse Smith](/assets/img/avatar_default.png)
and PATH from the original user to the target user. This could cause files in the wrogn path or home directory to be read (or written to), which resulted in potential security problems. This has been changed so that only DISPLAY and TERM are passed to the new environment. This is fine for running command line programs. When GUI programs need to be run, "keepenv" can be added to the user's doas.conf entry. This results in variables like HOME being copied to the target user, allowing GUI programs to run. Many thanks to Sander Bos for reporting this issue and explaining how it can be exploited. This commit also adds the ability to pass a customized PATH to target users. The new PATH can be set at compile time in the Makefile. The default path is provided in the Makefile and commented out.
237 lines
4.9 KiB
C
237 lines
4.9 KiB
C
/* $OpenBSD: env.c,v 1.5 2016/09/15 00:58:23 deraadt Exp $ */
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/*
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* Copyright (c) 2016 Ted Unangst <tedu@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#ifndef linux
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#include <sys/tree.h>
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <pwd.h>
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#include <err.h>
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#include <unistd.h>
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#include <errno.h>
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#ifdef linux
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#include "tree.h"
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#endif
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#include "doas.h"
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struct envnode {
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RB_ENTRY(envnode) node;
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const char *key;
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const char *value;
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};
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struct env {
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RB_HEAD(envtree, envnode) root;
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u_int count;
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};
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int
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envcmp(struct envnode *a, struct envnode *b)
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{
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return strcmp(a->key, b->key);
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}
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#ifdef __DragonFly__
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RB_PROTOTYPE_STATIC(envtree, envnode, node, envcmp);
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#endif
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RB_GENERATE_STATIC(envtree, envnode, node, envcmp)
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static struct envnode *
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createnode(const char *key, const char *value)
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{
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struct envnode *node;
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node = malloc(sizeof(*node));
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if (!node)
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err(1, NULL);
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node->key = strdup(key);
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node->value = strdup(value);
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if (!node->key || !node->value)
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err(1, NULL);
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return node;
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}
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static void
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freenode(struct envnode *node)
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{
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free((char *)node->key);
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free((char *)node->value);
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free(node);
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}
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static void
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addnode(struct env *env, const char *key, const char *value)
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{
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struct envnode *node;
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node = createnode(key, value);
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RB_INSERT(envtree, &env->root, node);
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env->count++;
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}
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static struct env *
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createenv(struct rule *rule, struct passwd *original, struct passwd *target)
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{
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struct env *env;
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u_int i;
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env = malloc(sizeof(*env));
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if (!env)
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err(1, NULL);
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RB_INIT(&env->root);
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env->count = 0;
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addnode(env, "DOAS_USER", original->pw_name);
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addnode(env, "HOME", target->pw_dir);
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addnode(env, "LOGNAME", target->pw_name);
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addnode(env, "PATH", GLOBAL_PATH);
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addnode(env, "SHELL", target->pw_shell);
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addnode(env, "USER", target->pw_name);
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if (rule->options & KEEPENV) {
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#ifndef linux
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extern const char **environ;
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#endif
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for (i = 0; environ[i] != NULL; i++) {
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struct envnode *node;
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const char *e, *eq;
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size_t len;
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char name[1024];
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e = environ[i];
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/* ignore invalid or overlong names */
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if ((eq = strchr(e, '=')) == NULL || eq == e)
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continue;
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len = eq - e;
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if (len > sizeof(name) - 1)
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continue;
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memcpy(name, e, len);
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name[len] = '\0';
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node = createnode(name, eq + 1);
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if (RB_INSERT(envtree, &env->root, node)) {
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/* ignore any later duplicates */
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freenode(node);
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} else {
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env->count++;
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}
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}
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}
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return env;
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}
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static char **
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flattenenv(struct env *env)
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{
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char **envp;
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struct envnode *node;
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u_int i;
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envp = reallocarray(NULL, env->count + 1, sizeof(char *));
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if (!envp)
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err(1, NULL);
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i = 0;
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RB_FOREACH(node, envtree, &env->root) {
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if (asprintf(&envp[i], "%s=%s", node->key, node->value) == -1)
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err(1, NULL);
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i++;
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}
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envp[i] = NULL;
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return envp;
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}
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static void
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fillenv(struct env *env, const char **envlist)
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{
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struct envnode *node, key;
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const char *e, *eq;
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const char *val;
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char name[1024];
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u_int i;
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size_t len;
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for (i = 0; envlist[i]; i++) {
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e = envlist[i];
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/* parse out env name */
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if ((eq = strchr(e, '=')) == NULL)
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len = strlen(e);
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else
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len = eq - e;
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if (len > sizeof(name) - 1)
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continue;
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memcpy(name, e, len);
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name[len] = '\0';
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/* delete previous copies */
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key.key = name;
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if (*name == '-')
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key.key = name + 1;
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if ((node = RB_FIND(envtree, &env->root, &key))) {
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RB_REMOVE(envtree, &env->root, node);
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freenode(node);
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env->count--;
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}
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if (*name == '-')
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continue;
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/* assign value or inherit from environ */
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if (eq) {
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val = eq + 1;
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if (*val == '$')
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val = getenv(val + 1);
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} else {
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val = getenv(name);
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}
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/* at last, we have something to insert */
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if (val) {
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node = createnode(name, val);
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RB_INSERT(envtree, &env->root, node);
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env->count++;
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}
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}
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}
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char **
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prepenv(struct rule *rule, struct passwd *original, struct passwd *target)
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{
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static const char *safeset[] = {
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"DISPLAY", "TERM", NULL
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};
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struct env *env;
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env = createenv(rule, original, target);
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/* if we started with blank, fill some defaults then apply rules */
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if (!(rule->options & KEEPENV))
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fillenv(env, safeset);
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if (rule->envlist)
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fillenv(env, rule->envlist);
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return flattenenv(env);
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}
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