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/* euidaccess -- check if effective user id can access file
Copyright (C) 1990, 1991 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Written by David MacKenzie and Torbjorn Granlund. */
#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 */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef _POSIX_VERSION
#include <limits.h>
#if !defined(NGROUPS_MAX) || NGROUPS_MAX < 1
#undef NGROUPS_MAX
#define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
#endif /* NGROUPS_MAX */
#else /* not _POSIX_VERSION */
uid_t getuid ();
gid_t getgid ();
uid_t geteuid ();
gid_t getegid ();
#include <sys/param.h>
#if !defined(NGROUPS_MAX) && defined(NGROUPS)
#define NGROUPS_MAX NGROUPS
#endif /* not NGROUPS_MAX and NGROUPS */
#endif /* not POSIX_VERSION */
#include <errno.h>
#ifndef errno
extern int errno;
#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
/* 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;
int group_member ();
/* Nonzero if UID, GID, EUID, and EGID have valid values. */
static int have_ids = 0;
/* Like euidaccess, except that a pointer to a filled-in stat structure
describing the file is provided instead of a filename.
Because this function is almost guaranteed to fail on systems that
use ACLs, a third argument *PATH may be used. If it is non-NULL,
it is assumed to be the name of the file corresponding to STATP.
Then, if the user is not running set-uid or set-gid, use access
instead of attempting a manual and non-portable comparison. */
static int
eaccess_stat (statp, mode, path)
const struct stat *statp;
int mode;
const char *path;
{
int granted;
mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
if (mode == F_OK)
return 0; /* The file exists. */
if (have_ids == 0)
{
have_ids = 1;
uid = getuid ();
gid = getgid ();
euid = geteuid ();
egid = getegid ();
}
if (path && uid == euid && gid == egid)
{
return access (path, mode);
}
/* The super-user can read and write any file, and execute any file
that anyone can execute. */
if (euid == 0 && ((mode & X_OK) == 0
|| (statp->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
return 0;
if (euid == statp->st_uid)
granted = (unsigned) (statp->st_mode & (mode << 6)) >> 6;
else if (egid == statp->st_gid
#ifdef HAVE_GETGROUPS
|| group_member (statp->st_gid)
#endif
)
granted = (unsigned) (statp->st_mode & (mode << 3)) >> 3;
else
granted = (statp->st_mode & mode);
if (granted == mode)
return 0;
errno = EACCESS;
return -1;
}
/* 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 (path, mode)
const char *path;
int mode;
{
struct stat stats;
if (have_ids == 0)
{
have_ids = 1;
uid = getuid ();
gid = getgid ();
euid = geteuid ();
egid = getegid ();
}
if (uid == euid && gid == egid)
{
return access (path, mode);
}
if (stat (path, &stats))
return -1;
return eaccess_stat (&stats, mode, path);
}
#ifdef TEST
#include <stdio.h>
#include <errno.h>
void error ();
char *program_name;
int
main (argc, argv)
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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