lib/secure_getenv.c

   1 /* Look up an environment variable, returning NULL in insecure situations.
   2
   3    Copyright 2013-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 #include <stdlib.h>
  21
  22 #if !HAVE___SECURE_GETENV
  23 # if HAVE_ISSETUGID || (HAVE_GETUID && HAVE_GETEUID && HAVE_GETGID && HAVE_GETEGID)
  24 #  include <unistd.h>
  25 # endif
  26 #endif
  27
  28 char *
  29 secure_getenv (char const *name)
  30 {
  31 #if HAVE___SECURE_GETENV /* glibc */
  32   return __secure_getenv (name);
  33 #elif HAVE_ISSETUGID /* musl, OS X, FreeBSD, NetBSD, OpenBSD, Solaris, Minix */
  34   if (issetugid ())
  35     return NULL;
  36   return getenv (name);
  37 #elif HAVE_GETUID && HAVE_GETEUID && HAVE_GETGID && HAVE_GETEGID /* other Unix */
  38   if (geteuid () != getuid () || getegid () != getgid ())
  39     return NULL;
  40   return getenv (name);
  41 #elif defined _WIN32 && ! defined __CYGWIN__ /* native Windows */
  42   /* On native Windows, there is no such concept as setuid or setgid binaries.
  43      - Programs launched as system services have high privileges, but they don't
  44        inherit environment variables from a user.
  45      - Programs launched by a user with "Run as Administrator" have high
  46        privileges and use the environment variables, but the user has been asked
  47        whether he agrees.
  48      - Programs launched by a user without "Run as Administrator" cannot gain
  49        high privileges, therefore there is no risk. */
  50   return getenv (name);
  51 #else
  52   return NULL;
  53 #endif
  54 }