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/* eaccess.c - eaccess replacement for the shell, plus other access functions. */
/* Copyright (C) 2006-2020 Free Software Foundation, Inc.
This file is part of GNU Bash, the Bourne Again SHell.
Bash 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 3 of the License, or
(at your option) any later version.
Bash 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 Bash. If not, see <http://www.gnu.org/licenses/>.
*/
#if defined (HAVE_CONFIG_H)
# include <config.h>
#endif
#include <stdio.h>
#include "bashtypes.h"
#if defined (HAVE_UNISTD_H)
# include <unistd.h>
#endif
#include "bashansi.h"
#include <errno.h>
#if !defined (errno)
extern int errno;
#endif /* !errno */
#if !defined (_POSIX_VERSION) && defined (HAVE_SYS_FILE_H)
# include <sys/file.h>
#endif /* !_POSIX_VERSION */
#include "posixstat.h"
#include "filecntl.h"
#include "shell.h"
#if !defined (R_OK)
#define R_OK 4
#define W_OK 2
#define X_OK 1
#define F_OK 0
#endif /* R_OK */
static int path_is_devfd PARAMS((const char *));
static int sh_stataccess PARAMS((const char *, int));
#if HAVE_DECL_SETREGID
static int sh_euidaccess PARAMS((const char *, int));
#endif
static int
path_is_devfd (path)
const char *path;
{
if (path[0] == '/' && path[1] == 'd' && strncmp (path, "/dev/fd/", 8) == 0)
return 1;
else if (STREQN (path, "/dev/std", 8))
{
if (STREQ (path+8, "in") || STREQ (path+8, "out") || STREQ (path+8, "err"))
return 1;
else
return 0;
}
else
return 0;
}
/* A wrapper for stat () which disallows pathnames that are empty strings
and handles /dev/fd emulation on systems that don't have it. */
int
sh_stat (path, finfo)
const char *path;
struct stat *finfo;
{
static char *pbuf = 0;
if (*path == '\0')
{
errno = ENOENT;
return (-1);
}
if (path[0] == '/' && path[1] == 'd' && strncmp (path, "/dev/fd/", 8) == 0)
{
/* If stating /dev/fd/n doesn't produce the same results as fstat of
FD N, then define DEV_FD_STAT_BROKEN */
#if !defined (HAVE_DEV_FD) || defined (DEV_FD_STAT_BROKEN)
intmax_t fd;
int r;
if (legal_number (path + 8, &fd) && fd == (int)fd)
{
r = fstat ((int)fd, finfo);
if (r == 0 || errno != EBADF)
return (r);
}
errno = ENOENT;
return (-1);
#else
/* If HAVE_DEV_FD is defined, DEV_FD_PREFIX is defined also, and has a
trailing slash. Make sure /dev/fd/xx really uses DEV_FD_PREFIX/xx.
On most systems, with the notable exception of linux, this is
effectively a no-op. */
pbuf = xrealloc (pbuf, sizeof (DEV_FD_PREFIX) + strlen (path + 8));
strcpy (pbuf, DEV_FD_PREFIX);
strcat (pbuf, path + 8);
return (stat (pbuf, finfo));
#endif /* !HAVE_DEV_FD */
}
#if !defined (HAVE_DEV_STDIN)
else if (STREQN (path, "/dev/std", 8))
{
if (STREQ (path+8, "in"))
return (fstat (0, finfo));
else if (STREQ (path+8, "out"))
return (fstat (1, finfo));
else if (STREQ (path+8, "err"))
return (fstat (2, finfo));
else
return (stat (path, finfo));
}
#endif /* !HAVE_DEV_STDIN */
return (stat (path, finfo));
}
/* Do the same thing access(2) does, but use the effective uid and gid,
and don't make the mistake of telling root that any file is
executable. This version uses stat(2). */
static int
sh_stataccess (path, mode)
const char *path;
int mode;
{
struct stat st;
if (sh_stat (path, &st) < 0)
return (-1);
if (current_user.euid == 0)
{
/* Root can read or write any file. */
if ((mode & X_OK) == 0)
return (0);
/* Root can execute any file that has any one of the execute
bits set. */
if (st.st_mode & S_IXUGO)
return (0);
}
if (st.st_uid == current_user.euid) /* owner */
mode <<= 6;
else if (group_member (st.st_gid))
mode <<= 3;
if (st.st_mode & mode)
return (0);
errno = EACCES;
return (-1);
}
#if HAVE_DECL_SETREGID
/* Version to call when uid != euid or gid != egid. We temporarily swap
the effective and real uid and gid as appropriate. */
static int
sh_euidaccess (path, mode)
const char *path;
int mode;
{
int r, e;
if (current_user.uid != current_user.euid)
setreuid (current_user.euid, current_user.uid);
if (current_user.gid != current_user.egid)
setregid (current_user.egid, current_user.gid);
r = access (path, mode);
e = errno;
if (current_user.uid != current_user.euid)
setreuid (current_user.uid, current_user.euid);
if (current_user.gid != current_user.egid)
setregid (current_user.gid, current_user.egid);
errno = e;
return r;
}
#endif
int
sh_eaccess (path, mode)
const char *path;
int mode;
{
int ret;
if (path_is_devfd (path))
return (sh_stataccess (path, mode));
#if (defined (HAVE_FACCESSAT) && defined (AT_EACCESS)) || defined (HAVE_EACCESS)
# if defined (HAVE_FACCESSAT) && defined (AT_EACCESS)
ret = faccessat (AT_FDCWD, path, mode, AT_EACCESS);
# else /* HAVE_EACCESS */ /* FreeBSD */
ret = eaccess (path, mode); /* XXX -- not always correct for X_OK */
# endif /* HAVE_EACCESS */
# if defined (__FreeBSD__) || defined (SOLARIS) || defined (_AIX)
if (ret == 0 && current_user.euid == 0 && mode == X_OK)
return (sh_stataccess (path, mode));
# endif /* __FreeBSD__ || SOLARIS || _AIX */
return ret;
#elif defined (EFF_ONLY_OK) /* SVR4(?), SVR4.2 */
return access (path, mode|EFF_ONLY_OK);
#else
if (mode == F_OK)
return (sh_stataccess (path, mode));
# if HAVE_DECL_SETREGID
if (current_user.uid != current_user.euid || current_user.gid != current_user.egid)
return (sh_euidaccess (path, mode));
# endif
if (current_user.uid == current_user.euid && current_user.gid == current_user.egid)
{
ret = access (path, mode);
#if defined (__FreeBSD__) || defined (SOLARIS)
if (ret == 0 && current_user.euid == 0 && mode == X_OK)
return (sh_stataccess (path, mode));
#endif
return ret;
}
return (sh_stataccess (path, mode));
#endif
}
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