1 | /* Test for access to file, relative to open directory. Linux version. |
2 | Copyright (C) 2006-2016 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <errno.h> |
20 | #include <fcntl.h> |
21 | #include <stddef.h> |
22 | #include <stdio.h> |
23 | #include <string.h> |
24 | #include <unistd.h> |
25 | #include <sys/types.h> |
26 | #include <alloca.h> |
27 | #include <sysdep.h> |
28 | |
29 | |
30 | int |
31 | faccessat (int fd, const char *file, int mode, int flag) |
32 | { |
33 | if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS)) |
34 | return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL); |
35 | |
36 | if ((flag == 0 || ((flag & ~AT_EACCESS) == 0 && ! __libc_enable_secure))) |
37 | return INLINE_SYSCALL (faccessat, 3, fd, file, mode); |
38 | |
39 | struct stat64 stats; |
40 | if (__fxstatat64 (_STAT_VER, fd, file, &stats, flag & AT_SYMLINK_NOFOLLOW)) |
41 | return -1; |
42 | |
43 | mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */ |
44 | #if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH |
45 | # error Oops, portability assumptions incorrect. |
46 | #endif |
47 | |
48 | if (mode == F_OK) |
49 | return 0; /* The file exists. */ |
50 | |
51 | uid_t uid = (flag & AT_EACCESS) ? __geteuid () : __getuid (); |
52 | |
53 | /* The super-user can read and write any file, and execute any file |
54 | that anyone can execute. */ |
55 | if (uid == 0 && ((mode & X_OK) == 0 |
56 | || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)))) |
57 | return 0; |
58 | |
59 | int granted = (uid == stats.st_uid |
60 | ? (unsigned int) (stats.st_mode & (mode << 6)) >> 6 |
61 | : (stats.st_gid == ((flag & AT_EACCESS) |
62 | ? __getegid () : __getgid ()) |
63 | || __group_member (stats.st_gid)) |
64 | ? (unsigned int) (stats.st_mode & (mode << 3)) >> 3 |
65 | : (stats.st_mode & mode)); |
66 | |
67 | if (granted == mode) |
68 | return 0; |
69 | |
70 | return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES); |
71 | } |
72 | |