lib/env.c

   1 /*
   2  * Security checks of environment
   3  * Added from shadow-utils package
   4  * by Arkadiusz Miśkiewicz <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         "BASH_ENV=",    /* GNU creeping featurism strikes again... */
  30         "ENV=",
  31         "HOME=",
  32         "IFS=",
  33         "KRB_CONF=",
  34         "LD_",          /* anything with the LD_ prefix */
  35         "LIBPATH=",
  36         "MAIL=",
  37         "NLSPATH=",
  38         "PATH=",
  39         "SHELL=",
  40         "SHLIB_PATH=",
  41         (char *) 0
  42 };
  43
  44 /* these are allowed, but with no slashes inside
  45    (to work around security problems in GNU gettext) */
  46 static char * const noslash[] = {
  47         "LANG=",
  48         "LANGUAGE=",
  49         "LC_",          /* anything with the LC_ prefix */
  50         (char *) 0
  51 };
  52
  53 void
  54 sanitize_env(void)
  55 {
  56         char **envp = environ;
  57         char * const *bad;
  58         char **cur;
  59         char **move;
  60
  61         for (cur = envp; *cur; cur++) {
  62                 for (bad = forbid; *bad; bad++) {
  63                         if (strncmp(*cur, *bad, strlen(*bad)) == 0) {
  64                                 for (move = cur; *move; move++)
  65                                         *move = *(move + 1);
  66                                 cur--;
  67                                 break;
  68                         }
  69                 }
  70         }
  71
  72         for (cur = envp; *cur; cur++) {
  73                 for (bad = noslash; *bad; bad++) {
  74                         if (strncmp(*cur, *bad, strlen(*bad)) != 0)
  75                                 continue;
  76                         if (!strchr(*cur, '/'))
  77                                 continue;  /* OK */
  78                         for (move = cur; *move; move++)
  79                                 *move = *(move + 1);
  80                         cur--;
  81                         break;
  82                 }
  83         }
  84 }
  85
  86
  87 char *safe_getenv(const char *arg)
  88 {
  89         uid_t ruid = getuid();
  90
  91         if (ruid != 0 || (ruid != geteuid()) || (getgid() != getegid()))
  92                 return NULL;
  93 #ifdef HAVE_PRCTL
  94         if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
  95                 return NULL;
  96 #else
  97 #if (defined(linux) && defined(SYS_prctl))
  98         if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
  99                 return NULL;
 100 #endif
 101 #endif
 102 #ifdef HAVE_SECURE_GETENV
 103 return secure_getenv(arg);
 104 #elif HAVE___SECURE_GETENV
 105         return __secure_getenv(arg);
 106 #else
 107         return getenv(arg);
 108 #endif
 109 }