lib/env.c

   1 /*
   2  * Security checks of environment
   3  * Added from shadow-utils package
   4  * by Arkadiusz Mi¶kiewicz <misiek@pld.ORG.PL>
   5  *
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #ifdef HAVE_SYS_PRCTL_H
  12 #include <sys/prctl.h>
  13 #else
  14 #define PR_GET_DUMPABLE 3
  15 #endif
  16 #if (!defined(HAVE_PRCTL) && defined(linux))
  17 #include <sys/syscall.h>
  18 #endif
  19 #include <unistd.h>
  20 #include <sys/types.h>
  21
  22 #include "env.h"
  23
  24 #ifndef HAVE_ENVIRON_DECL
  25 extern char **environ;
  26 #endif
  27
  28 static char * const forbid[] = {
  29         "_RLD_=",
  30         "BASH_ENV=",    /* GNU creeping featurism strikes again... */
  31         "ENV=",
  32         "HOME=",
  33         "IFS=",
  34         "KRB_CONF=",
  35         "LD_",          /* anything with the LD_ prefix */
  36         "LIBPATH=",
  37         "MAIL=",
  38         "NLSPATH=",
  39         "PATH=",
  40         "SHELL=",
  41         "SHLIB_PATH=",
  42         (char *) 0
  43 };
  44
  45 /* these are allowed, but with no slashes inside
  46    (to work around security problems in GNU gettext) */
  47 static char * const noslash[] = {
  48         "LANG=",
  49         "LANGUAGE=",
  50         "LC_",          /* anything with the LC_ prefix */
  51         (char *) 0
  52 };
  53
  54 void
  55 sanitize_env(void)
  56 {
  57         char **envp = environ;
  58         char * const *bad;
  59         char **cur;
  60         char **move;
  61
  62         for (cur = envp; *cur; cur++) {
  63                 for (bad = forbid; *bad; bad++) {
  64                         if (strncmp(*cur, *bad, strlen(*bad)) == 0) {
  65                                 for (move = cur; *move; move++)
  66                                         *move = *(move + 1);
  67                                 cur--;
  68                                 break;
  69                         }
  70                 }
  71         }
  72
  73         for (cur = envp; *cur; cur++) {
  74                 for (bad = noslash; *bad; bad++) {
  75                         if (strncmp(*cur, *bad, strlen(*bad)) != 0)
  76                                 continue;
  77                         if (!strchr(*cur, '/'))
  78                                 continue;  /* OK */
  79                         for (move = cur; *move; move++)
  80                                 *move = *(move + 1);
  81                         cur--;
  82                         break;
  83                 }
  84         }
  85 }
  86
  87
  88 char *safe_getenv(const char *arg)
  89 {
  90         uid_t ruid = getuid();
  91
  92         if (ruid != 0 || (ruid != geteuid()) || (getgid() != getegid()))
  93                 return NULL;
  94 #ifdef HAVE_PRCTL
  95         if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
  96                 return NULL;
  97 #else
  98 #if (defined(linux) && defined(SYS_prctl))
  99         if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
 100                 return NULL;
 101 #endif
 102 #endif
 103
 104 #ifdef HAVE___SECURE_GETENV
 105         return __secure_getenv(arg);
 106 #else
 107         return getenv(arg);
 108 #endif
 109 }