141 lines
3.3 KiB
C
141 lines
3.3 KiB
C
/* @(#)openat.c 1.2 11/10/22 Copyright 2011 J. Schilling */
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/*
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* Emulate the behavior of openat(fd, name, flag, mode)
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*
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* Note that emulation methods that do not use the /proc filesystem are
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* not MT safe. In the non-MT-safe case, we do:
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*
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* savewd()/fchdir()/open(name)/restorewd()
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*
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* Errors may force us to abort the program as our caller is not expected
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* to know that we do more than a simple open() here and that the
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* working directory may be changed by us.
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*
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* Copyright (c) 2011 J. Schilling
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*/
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/*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* See the file CDDL.Schily.txt in this distribution for details.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file CDDL.Schily.txt from this distribution.
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*/
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#include <schily/unistd.h>
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#include <schily/types.h>
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#include <schily/fcntl.h>
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#include <schily/varargs.h>
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#include <schily/maxpath.h>
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#include <schily/errno.h>
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#include <schily/standard.h>
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#include <schily/schily.h>
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#include "at-defs.h"
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#ifndef HAVE_OPENAT
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#ifndef ENAMETOOLONG
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#define ENAMETOOLONG EINVAL
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#endif
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/* VARARGS3 */
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#ifdef PROTOTYPES
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EXPORT int
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openat(int fd, const char *name, int oflag, ...)
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#else
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EXPORT int
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openat(fd, name, oflag, va_alist)
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int fd;
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const char *name;
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int oflag;
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va_dcl
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#endif
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{
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va_list args;
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mode_t omode = 0;
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int n;
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int ret;
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char buf[PATH_MAX];
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char *proc_name;
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struct save_wd save_wd;
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if (oflag & O_CREAT) {
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#ifdef PROTOTYPES
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va_start(args, oflag);
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#else
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va_start(args);
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#endif
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/*
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* If sizeof (mode_t) is < sizeof (int) and used with va_arg(),
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* GCC4 will abort the code. So we need to use the promoted
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* size.
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*/
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omode = va_arg(args, PROMOTED_MODE_T);
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va_end(args);
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}
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if (fd == AT_FDCWD || ABS_NAME(name))
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return (open(name, oflag, omode));
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if ((proc_name = proc_fd2name(buf, fd, name)) != NULL) {
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ret = open(proc_name, oflag, omode);
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if (ret >= 0 || NON_PROCFS_ERRNO(errno))
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return (ret);
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} else if (geterrno() == ENAMETOOLONG) {
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return (-1);
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}
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if (savewd(&save_wd) < 0) {
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/*
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* We abort here as the caller may not know that we are forced
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* to savewd/fchdir/restorewd here and misinterpret errno.
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*/
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savewd_abort(geterrno());
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/* NOTREACHED */
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return (-1);
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}
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if (fd >= 0 && save_wd.fd == fd) {
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/*
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* If we just opened "fd" with the same number in savewd(), fd
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* must have been illegal when calling openat();
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*/
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closewd(&save_wd);
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seterrno(EBADF);
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return (-1);
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}
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if ((n = fchdir(fd)) < 0) {
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int err = geterrno();
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/*
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* In case that fchdir() is emulated via chdir() and we use a
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* multi hop chdir(), we may be on an undefined intermediate
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* directory. Try to return to last working directory and if
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* this fails, abort for security.
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*/
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if (n == -2 && restorewd(&save_wd) < 0) {
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restorewd_abort(geterrno());
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}
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closewd(&save_wd);
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seterrno(err);
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return (-1);
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}
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ret = open(name, oflag, omode); /* The actual open() */
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if (restorewd(&save_wd) < 0) {
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int err = geterrno();
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close(ret);
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closewd(&save_wd);
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restorewd_abort(err);
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seterrno(err);
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return (-1);
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}
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closewd(&save_wd);
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return (ret);
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}
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#endif /* HAVE_OPENAT */
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