1 /* Test for access to file, relative to open directory. Linux version.
2 Copyright (C) 2006-2022 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 <https://www.gnu.org/licenses/>. */
18
19 #include <fcntl.h>
20 #include <unistd.h>
21 #include <sys/types.h>
22 #include <sys/stat.h>
23 #include <sysdep.h>
24
25
26 int
__faccessat(int fd,const char * file,int mode,int flag)27 __faccessat (int fd, const char *file, int mode, int flag)
28 {
29 int ret = INLINE_SYSCALL_CALL (faccessat2, fd, file, mode, flag);
30 #if __ASSUME_FACCESSAT2
31 return ret;
32 #else
33 if (ret == 0 || errno != ENOSYS)
34 return ret;
35
36 if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS))
37 return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
38
39 if ((flag == 0 || ((flag & ~AT_EACCESS) == 0 && ! __libc_enable_secure)))
40 return INLINE_SYSCALL (faccessat, 3, fd, file, mode);
41
42 struct __stat64_t64 stats;
43 if (__fstatat64_time64 (fd, file, &stats, flag & AT_SYMLINK_NOFOLLOW))
44 return -1;
45
46 mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
47 # if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
48 # error Oops, portability assumptions incorrect.
49 # endif
50
51 if (mode == F_OK)
52 return 0; /* The file exists. */
53
54 uid_t uid = (flag & AT_EACCESS) ? __geteuid () : __getuid ();
55
56 /* The super-user can read and write any file, and execute any file
57 that anyone can execute. */
58 if (uid == 0 && ((mode & X_OK) == 0
59 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
60 return 0;
61
62 int granted = (uid == stats.st_uid
63 ? (unsigned int) (stats.st_mode & (mode << 6)) >> 6
64 : (stats.st_gid == ((flag & AT_EACCESS)
65 ? __getegid () : __getgid ())
66 || __group_member (stats.st_gid))
67 ? (unsigned int) (stats.st_mode & (mode << 3)) >> 3
68 : (stats.st_mode & mode));
69
70 if (granted == mode)
71 return 0;
72
73 return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES);
74 #endif /* !__ASSUME_FACCESSAT2 */
75 }
76 weak_alias (__faccessat, faccessat)
77