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
33 extern "C" int __faccessat(int, const char*, int);
34
faccessat(int dirfd,const char * pathname,int mode,int flags)35 int 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 // More details at http://permalink.gmane.org/gmane.linux.lib.musl.general/6952
49 //
50 // AT_EACCESS isn't supported either. Android doesn't have setuid
51 // programs, and never runs code with euid!=uid.
52 //
53 // We could use faccessat2(2) from Linux 5.8, but since we don't want the
54 // first feature and don't need the second, we just reject such requests.
55 errno = EINVAL;
56 return -1;
57 }
58
59 return __faccessat(dirfd, pathname, mode);
60 }
61