Initial cut at a hooks implementation. The plugin can register
hooks for getenv, putenv, setenv and unsetenv. This makes it possible for the plugin to trap changes to the environment made by authentication methods such as PAM or BSD auth so that such changes are reflected in the environment passed back to sudo for execve().
This commit is contained in:
Todd C. Miller
298
src/env_hooks.c
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298
src/env_hooks.c
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/*
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* Copyright (c) 2010, 2012 Todd C. Miller <Todd.Miller@courtesan.com>
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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 <config.h>
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#include <sys/types.h>
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#include <stdio.h>
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#ifdef STDC_HEADERS
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# include <stdlib.h>
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# include <stddef.h>
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#else
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# ifdef HAVE_STDLIB_H
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# include <stdlib.h>
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# endif
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#endif /* STDC_HEADERS */
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif /* HAVE_STRING_H */
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#ifdef HAVE_STRINGS_H
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# include <strings.h>
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#endif /* HAVE_STRINGS_H */
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#if defined(HAVE_MALLOC_H) && !defined(STDC_HEADERS)
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# include <malloc.h>
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#endif /* HAVE_MALLOC_H && !STDC_HEADERS */
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#include <errno.h>
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#ifdef HAVE_DLOPEN
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# include <dlfcn.h>
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#else
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# include "compat/dlfcn.h"
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#endif
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#include "sudo.h"
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#include "sudo_plugin.h"
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extern char **environ; /* global environment pointer */
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static char **priv_environ; /* private environment pointer */
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static char *
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rpl_getenv(const char *name)
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{
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char **ep, *val = NULL;
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size_t namelen = 0;
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/* For BSD compatibility, treat '=' in name like end of string. */
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while (name[namelen] != '\0' && name[namelen] != '=')
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namelen++;
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for (ep = environ; *ep != NULL; ep++) {
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if (strncmp(*ep, name, namelen) == 0 && (*ep)[namelen] == '=') {
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val = *ep + namelen + 1;
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break;
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}
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}
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return val;
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}
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char *
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getenv(const char *name)
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{
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char *val = NULL;
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switch (process_hooks_getenv(name, &val)) {
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case SUDO_HOOK_RET_STOP:
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return val;
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case SUDO_HOOK_RET_ERROR:
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return NULL;
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default: {
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#if defined(HAVE_DLOPEN)
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char * (*fn)(const char *);
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fn = dlsym(RTLD_NEXT, "getenv");
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if (fn != NULL)
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return fn(name);
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#endif /* HAVE_DLOPEN */
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return rpl_getenv(name);
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}
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}
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}
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static int
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rpl_putenv(PUTENV_CONST char *string)
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{
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char **ep;
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size_t len;
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bool found = false;
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/* Look for existing entry. */
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len = (strchr(string, '=') - string) + 1;
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for (ep = environ; *ep != NULL; ep++) {
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if (strncmp(string, *ep, len) == 0) {
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*ep = string;
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found = true;
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break;
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}
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}
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/* Prune out duplicate variables. */
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if (found) {
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while (*ep != NULL) {
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if (strncmp(string, *ep, len) == 0) {
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char **cur = ep;
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while ((*cur = *(cur + 1)) != NULL)
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cur++;
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} else {
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ep++;
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}
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}
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}
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/* Append at the end if not already found. */
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if (!found) {
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size_t env_len = (size_t)(ep - environ);
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char **envp = erealloc3(priv_environ, env_len + 2, sizeof(char *));
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if (environ != priv_environ)
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memcpy(envp, environ, env_len * sizeof(char *));
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envp[env_len++] = string;
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envp[env_len] = NULL;
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priv_environ = environ = envp;
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}
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return 0;
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}
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int
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putenv(PUTENV_CONST char *string)
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{
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switch (process_hooks_putenv((char *)string)) {
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case SUDO_HOOK_RET_STOP:
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return 0;
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case SUDO_HOOK_RET_ERROR:
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return -1;
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default: {
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#if defined(HAVE_DLOPEN)
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int (*fn)(PUTENV_CONST char *);
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fn = dlsym(RTLD_NEXT, "putenv");
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if (fn != NULL)
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return fn(string);
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#endif /* HAVE_DLOPEN */
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return rpl_putenv(string);
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}
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}
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}
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static int
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rpl_setenv(const char *var, const char *val, int overwrite)
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{
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char *envstr, *dst;
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const char *src;
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size_t esize;
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if (!var || *var == '\0') {
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errno = EINVAL;
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return -1;
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}
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/*
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* POSIX says a var name with '=' is an error but BSD
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* just ignores the '=' and anything after it.
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*/
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for (src = var; *src != '\0' && *src != '='; src++)
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;
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esize = (size_t)(src - var) + 2;
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if (val) {
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esize += strlen(val); /* glibc treats a NULL val as "" */
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}
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/* Allocate and fill in envstr. */
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if ((envstr = malloc(esize)) == NULL)
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return -1;
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for (src = var, dst = envstr; *src != '\0' && *src != '=';)
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*dst++ = *src++;
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*dst++ = '=';
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if (val) {
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for (src = val; *src != '\0';)
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*dst++ = *src++;
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}
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*dst = '\0';
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if (!overwrite && getenv(var) != NULL) {
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free(envstr);
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return 0;
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}
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return rpl_putenv(envstr);
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}
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int
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setenv(const char *var, const char *val, int overwrite)
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{
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switch (process_hooks_setenv(var, val, overwrite)) {
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case SUDO_HOOK_RET_STOP:
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return 0;
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case SUDO_HOOK_RET_ERROR:
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return -1;
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default: {
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#if defined(HAVE_SETENV) && defined(HAVE_DLOPEN)
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int (*fn)(const char *, const char *, int);
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fn = dlsym(RTLD_NEXT, "setenv");
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if (fn != NULL)
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return fn(var, val, overwrite);
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#endif /* HAVE_SETENV && HAVE_DLOPEN */
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return rpl_setenv(var, val, overwrite);
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}
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}
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}
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#ifdef UNSETENV_VOID
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static void
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#else
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int
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#endif
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rpl_unsetenv(const char *var)
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{
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char **ep = environ;
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size_t len;
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if (var == NULL || *var == '\0' || strchr(var, '=') != NULL) {
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errno = EINVAL;
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#ifdef UNSETENV_VOID
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return;
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#else
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return -1;
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#endif
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}
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len = strlen(var);
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while (*ep != NULL) {
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if (strncmp(var, *ep, len) == 0 && (*ep)[len] == '=') {
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/* Found it; shift remainder + NULL over by one. */
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char **cur = ep;
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while ((*cur = *(cur + 1)) != NULL)
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cur++;
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/* Keep going, could be multiple instances of the var. */
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} else {
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ep++;
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}
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}
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#ifndef UNSETENV_VOID
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return 0;
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#endif
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}
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#ifdef UNSETENV_VOID
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void
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unsetenv(const char *var)
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{
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switch (process_hooks_unsetenv(var)) {
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case SUDO_HOOK_RET_STOP:
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return 0;
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case SUDO_HOOK_RET_ERROR:
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return -1;
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default: {
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#if defined(HAVE_UNSETENV) && defined(HAVE_DLOPEN)
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void (*fn)(const char *);
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fn = dlsym(RTLD_NEXT, "unsetenv");
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if (fn != NULL)
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fn(var);
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else
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#endif /* HAVE_UNSETENV && HAVE_DLOPEN */
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rpl_unsetenv(var);
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}
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}
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}
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#else
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int
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unsetenv(const char *var)
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{
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switch (process_hooks_unsetenv(var)) {
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case SUDO_HOOK_RET_STOP:
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return 0;
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case SUDO_HOOK_RET_ERROR:
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return -1;
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default: {
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#if defined(HAVE_UNSETENV) && defined(HAVE_DLOPEN)
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int (*fn)(const char *);
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fn = dlsym(RTLD_NEXT, "unsetenv");
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if (fn != NULL)
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return fn(var);
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#endif /* HAVE_UNSETENV && HAVE_DLOPEN */
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return rpl_unsetenv(var);
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}
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}
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}
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#endif /* UNSETENV_VOID */
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Block a user