/* Check if effective user id can access file

   Copyright (C) 1990-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library 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.

   The GNU C Library 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 the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

/* Written by David MacKenzie and Torbjorn Granlund.

   Adapted for GNU C library by Roland McGrath.  */

#ifdef HAVE_CONFIG_H

# include <config.h>

#endif

#include <sys/types.h>

#include <sys/stat.h>

#ifdef S_IEXEC

# ifndef S_IXUSR

#  define S_IXUSR S_IEXEC

# endif

# ifndef S_IXGRP

#  define S_IXGRP (S_IEXEC >> 3)

# endif

# ifndef S_IXOTH

#  define S_IXOTH (S_IEXEC >> 6)

# endif

#endif /* S_IEXEC */

#if defined HAVE_UNISTD_H || defined _LIBC

# include <unistd.h>

#endif

#ifndef _POSIX_VERSION

uid_t getuid ();

gid_t getgid ();

uid_t geteuid ();

gid_t getegid ();

#endif /* not POSIX_VERSION */

#include <errno.h>

#ifndef errno

extern int errno;

#endif

#ifndef __set_errno

# define __set_errno(val) errno = (val)

#endif

#if defined EACCES && !defined EACCESS

# define EACCESS EACCES

#endif

#ifndef F_OK

# define F_OK 0

# define X_OK 1

# define W_OK 2

# define R_OK 4

#endif

#if !defined S_IROTH && defined R_OK

# define S_IROTH R_OK

#endif

#if !defined S_IWOTH && defined W_OK

# define S_IWOTH W_OK

#endif

#if !defined S_IXOTH && defined X_OK

# define S_IXOTH X_OK

#endif

#ifdef _LIBC

# define group_member __group_member

# define euidaccess __euidaccess

#else

/* The user's real user id. */

static uid_t uid;

/* The user's real group id. */

static gid_t gid;

/* The user's effective user id. */

static uid_t euid;

/* The user's effective group id. */

static gid_t egid;

/* Nonzero if UID, GID, EUID, and EGID have valid values. */

static int have_ids;

# ifdef HAVE_GETGROUPS

int group_member ();

# else

#  define group_member(gid)	0

# endif

#endif

/* Return 0 if the user has permission of type MODE on file PATH;

   otherwise, return -1 and set `errno' to EACCESS.

   Like access, except that it uses the effective user and group

   id's instead of the real ones, and it does not check for read-only

   filesystem, text busy, etc. */

int

euidaccess (const char *path, int mode)

{

  struct stat64 stats;

  int granted;

#ifdef	_LIBC

  uid_t euid;

  gid_t egid;

#else

  if (have_ids == 0)

    {

      have_ids = 1;

      uid = getuid ();

      gid = getgid ();

      euid = geteuid ();

      egid = getegid ();

    }

  if (uid == euid && gid == egid)

    /* If we are not set-uid or set-gid, access does the same.  */

    return access (path, mode);

#endif

  if (stat64 (path, &stats))

    return -1;

  mode &= (X_OK | W_OK | R_OK);	/* Clear any bogus bits. */

#if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH

  ?error Oops, portability assumptions incorrect.

#endif

  if (mode == F_OK)

    return 0;			/* The file exists. */

#ifdef	_LIBC

  /* Now we need the IDs.  */

  euid = __geteuid ();

  egid = __getegid ();

  if (__getuid () == euid && __getgid () == egid)

    /* If we are not set-uid or set-gid, access does the same.  */

    return __access (path, mode);

#endif

  /* The super-user can read and write any file, and execute any file

     that anyone can execute. */

  if (euid == 0 && ((mode & X_OK) == 0

		    || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))

    return 0;

  if (euid == stats.st_uid)

    granted = (unsigned int) (stats.st_mode & (mode << 6)) >> 6;

  else if (egid == stats.st_gid || group_member (stats.st_gid))

    granted = (unsigned int) (stats.st_mode & (mode << 3)) >> 3;

  else

    granted = (stats.st_mode & mode);

  /* XXX Add support for ACLs.  */

  if (granted == mode)

    return 0;

  __set_errno (EACCESS);

  return -1;

}

#undef euidaccess

#undef eaccess

#ifdef weak_alias

weak_alias (__euidaccess, euidaccess)

weak_alias (__euidaccess, eaccess)

#endif

#ifdef TEST

# include <stdio.h>

# include <errno.h>

# include "error.h"

char *program_name;

int

main (int argc, char **argv)

{

  char *file;

  int mode;

  int err;

  program_name = argv[0];

  if (argc < 3)

    abort ();

  file = argv[1];

  mode = atoi (argv[2]);

  err = euidaccess (file, mode);

  printf ("%d\n", err);

  if (err != 0)

    error (0, errno, "%s", file);

  exit (0);

}

#endif