1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <fcntl.h>
30#include <unistd.h>
31#include <errno.h>
32
33extern "C" int ___faccessat(int, const char*, int);
34
35int faccessat(int dirfd, const char* pathname, int mode, int flags) {
36  // "The mode specifies the accessibility check(s) to be performed,
37  // and is either the value F_OK, or a mask consisting of the
38  // bitwise OR of one or more of R_OK, W_OK, and X_OK."
39  if ((mode != F_OK) && ((mode & ~(R_OK | W_OK | X_OK)) != 0) &&
40      ((mode & (R_OK | W_OK | X_OK)) == 0)) {
41    errno = EINVAL;
42    return -1;
43  }
44
45  if (flags != 0) {
46    // We deliberately don't support AT_SYMLINK_NOFOLLOW, a glibc
47    // only feature which is error prone and dangerous.
48    //
49    // AT_EACCESS isn't supported either. Android doesn't have setuid
50    // programs, and never runs code with euid!=uid. It could be
51    // implemented in an expensive way, following the model at
52    // https://gitlab.com/bminor/musl/commit/0a05eace163cee9b08571d2ff9d90f5e82d9c228
53    // but not worth it.
54    errno = EINVAL;
55    return -1;
56  }
57
58  return ___faccessat(dirfd, pathname, mode);
59}
60