/* Test for access to file, relative to open directory.  Linux version.

   Copyright (C) 2006-2018 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/>.  */

#include <errno.h>

#include <fcntl.h>

#include <stddef.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <sys/types.h>

#include <alloca.h>

#include <sysdep.h>

int

faccessat (int fd, const char *file, int mode, int flag)

{

  if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS))

    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);

  if ((flag == 0 || ((flag & ~AT_EACCESS) == 0 && ! __libc_enable_secure)))

    return INLINE_SYSCALL (faccessat, 3, fd, file, mode);

  struct stat64 stats;

  if (__fxstatat64 (_STAT_VER, fd, file, &stats, flag & AT_SYMLINK_NOFOLLOW))

    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. */

  uid_t uid = (flag & AT_EACCESS) ? __geteuid () : __getuid ();

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

     that anyone can execute. */

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

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

    return 0;

  int granted = (uid == stats.st_uid

		 ? (unsigned int) (stats.st_mode & (mode << 6)) >> 6

		 : (stats.st_gid == ((flag & AT_EACCESS)

				     ? __getegid () : __getgid ())

		    || __group_member (stats.st_gid))

		 ? (unsigned int) (stats.st_mode & (mode << 3)) >> 3

		 : (stats.st_mode & mode));

  if (granted == mode)

    return 0;

  return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES);

}