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/*
* environ[] array cleanup code and getenv() wrappers
*
* No copyright is claimed. This code is in the public domain; do with
* it what you wish.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#else
#define PR_GET_DUMPABLE 3
#endif
#if (!defined(HAVE_PRCTL) && defined(linux))
#include <sys/syscall.h>
#endif
#include <unistd.h>
#include <sys/types.h>
#include "env.h"
#ifndef HAVE_ENVIRON_DECL
extern char **environ;
#endif
static char * const forbid[] = {
"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 char * const noslash[] = {
"LANG=",
"LANGUAGE=",
"LC_", /* anything with the LC_ prefix */
(char *) 0
};
struct ul_env_list {
char *env;
struct ul_env_list *next;
};
/*
* Saves @name env.variable to @ls, returns pointer to the new head of the list.
*/
static struct ul_env_list *env_list_add(struct ul_env_list *ls0, const char *str)
{
struct ul_env_list *ls;
char *p;
size_t sz = 0;
if (!str || !*str)
return ls0;
sz = strlen(str) + 1;
p = malloc(sizeof(struct ul_env_list) + sz);
if (!p)
return ls0;
ls = (struct ul_env_list *) p;
p += sizeof(struct ul_env_list);
memcpy(p, str, sz);
ls->env = p;
ls->next = ls0;
return ls;
}
/*
* Use setenv() for all stuff in @ls.
*
* It would be possible to use putenv(), but we want to keep @ls free()-able.
*/
int env_list_setenv(struct ul_env_list *ls)
{
int rc = 0;
while (ls && rc == 0) {
if (ls->env) {
char *val = strchr(ls->env, '=');
if (!val)
continue;
*val = '\0';
rc = setenv(ls->env, val + 1, 0);
*val = '=';
}
ls = ls->next;
}
return rc;
}
void env_list_free(struct ul_env_list *ls)
{
while (ls) {
struct ul_env_list *x = ls;
ls = ls->next;
free(x);
}
}
/*
* Removes unwanted variables from environ[]. If @org is not NULL than stores
* unwnated variables to the list.
*/
void __sanitize_env(struct ul_env_list **org)
{
char **envp = environ;
char * const *bad;
char **cur;
int last = 0;
for (cur = envp; *cur; cur++)
last++;
for (cur = envp; *cur; cur++) {
for (bad = forbid; *bad; bad++) {
if (strncmp(*cur, *bad, strlen(*bad)) == 0) {
if (org)
*org = env_list_add(*org, *cur);
last = remote_entry(envp, cur - envp, last);
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 */
if (org)
*org = env_list_add(*org, *cur);
last = remote_entry(envp, cur - envp, last);
cur--;
break;
}
}
}
void sanitize_env(void)
{
__sanitize_env(NULL);
}
char *safe_getenv(const char *arg)
{
uid_t ruid = getuid();
if (ruid != 0 || (ruid != geteuid()) || (getgid() != getegid()))
return NULL;
#ifdef HAVE_PRCTL
if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
return NULL;
#else
#if (defined(linux) && defined(SYS_prctl))
if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
return NULL;
#endif
#endif
#ifdef HAVE_SECURE_GETENV
return secure_getenv(arg);
#elif HAVE___SECURE_GETENV
return __secure_getenv(arg);
#else
return getenv(arg);
#endif
}
#ifdef TEST_PROGRAM
int main(void)
{
char *const *bad;
char copy[32];
char *p;
int retval = EXIT_SUCCESS;
struct ul_env_list *removed = NULL;
for (bad = forbid; *bad; bad++) {
strcpy(copy, *bad);
p = strchr(copy, '=');
if (p)
*p = '\0';
setenv(copy, copy, 1);
}
/* removed */
__sanitize_env(&removed);
/* check removal */
for (bad = forbid; *bad; bad++) {
strcpy(copy, *bad);
p = strchr(copy, '=');
if (p)
*p = '\0';
p = getenv(copy);
if (p) {
warnx("%s was not removed", copy);
retval = EXIT_FAILURE;
}
}
/* restore removed */
env_list_setenv(removed);
/* check restore */
for (bad = forbid; *bad; bad++) {
strcpy(copy, *bad);
p = strchr(copy, '=');
if (p)
*p = '\0';
p = getenv(copy);
if (!p) {
warnx("%s was not restored", copy);
retval = EXIT_FAILURE;
}
}
env_list_free(removed);
return retval;
}
#endif
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