/* Look up an environment variable, returning NULL in insecure situations.

   Copyright 2013-2020 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify it

   under the terms of the GNU Lesser General Public License as published

   by the Free Software Foundation; either version 2.1 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

#include <stdlib.h>

#if !HAVE___SECURE_GETENV

# if HAVE_ISSETUGID || (HAVE_GETUID && HAVE_GETEUID && HAVE_GETGID && HAVE_GETEGID)

#  include <unistd.h>

# endif

#endif

char *

secure_getenv (char const *name)

{

#if HAVE___SECURE_GETENV /* glibc */

  return __secure_getenv (name);

#elif HAVE_ISSETUGID /* OS X, FreeBSD, NetBSD, OpenBSD */

  if (issetugid ())

    return NULL;

  return getenv (name);

#elif HAVE_GETUID && HAVE_GETEUID && HAVE_GETGID && HAVE_GETEGID /* other Unix */

  if (geteuid () != getuid () || getegid () != getgid ())

    return NULL;

  return getenv (name);

#elif defined _WIN32 && ! defined __CYGWIN__ /* native Windows */

  /* On native Windows, there is no such concept as setuid or setgid binaries.

     - Programs launched as system services have high privileges, but they don't

       inherit environment variables from a user.

     - Programs launched by a user with "Run as Administrator" have high

       privileges and use the environment variables, but the user has been asked

       whether he agrees.

     - Programs launched by a user without "Run as Administrator" cannot gain

       high privileges, therefore there is no risk. */

  return getenv (name);

#else

  return NULL;

#endif

}