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/* Check if effective user id can access file
Copyright (C) 1990-2025 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/>. */
/* 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_t64 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_time64 (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
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