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/* Test for access to file, relative to open directory. Linux version.
Copyright (C) 2006-2020 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
<https://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);
}
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