1 /* euidaccess -- check if effective user id can access file
3 Copyright (C) 1990-1991, 1995, 1998, 2000, 2003-2006, 2008-2011 Free
4 Software Foundation, Inc.
6 This file is part of the GNU C Library.
8 This program is free software: you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program. If not, see <http://www.gnu.org/licenses/>. */
21 /* Written by David MacKenzie and Torbjorn Granlund.
22 Adapted for GNU C library by Roland McGrath. */
29 #include <sys/types.h>
39 # define __set_errno(val) errno = (val)
42 #if defined EACCES && !defined EACCESS
43 # define EACCESS EACCES
56 # define access __access
57 # define getuid __getuid
58 # define getgid __getgid
59 # define geteuid __geteuid
60 # define getegid __getegid
61 # define group_member __group_member
62 # define euidaccess __euidaccess
68 /* Return 0 if the user has permission of type MODE on FILE;
69 otherwise, return -1 and set `errno'.
70 Like access, except that it uses the effective user and group
71 id's instead of the real ones, and it does not always check for read-only
72 file system, text busy, etc. */
75 euidaccess (const char *file, int mode)
77 #if HAVE_FACCESSAT /* glibc */
78 return faccessat (AT_FDCWD, file, mode, AT_EACCESS);
79 #elif defined EFF_ONLY_OK /* IRIX, OSF/1, Interix */
80 return access (file, mode | EFF_ONLY_OK);
81 #elif defined ACC_SELF /* AIX */
82 return accessx (file, mode, ACC_SELF);
83 #elif HAVE_EACCESS /* FreeBSD */
84 return eaccess (file, mode);
85 #else /* MacOS X, NetBSD, OpenBSD, HP-UX, Solaris, Cygwin, mingw, BeOS */
87 uid_t uid = getuid ();
88 gid_t gid = getgid ();
89 uid_t euid = geteuid ();
90 gid_t egid = getegid ();
93 # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS
95 /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to
96 return the correct result even if this would make it
97 nonreentrant. Define this only if your entire application is
98 safe even if the uid or gid might temporarily change. If your
99 application uses signal handlers or threads it is probably not
103 return stat (file, &stats);
110 setreuid (euid, uid);
112 setregid (egid, gid);
114 result = access (file, mode);
119 setreuid (uid, euid);
121 setregid (gid, egid);
129 /* The following code assumes the traditional Unix model, and is not
130 correct on systems that have ACLs or the like. However, it's
131 better than nothing, and it is reentrant. */
133 unsigned int granted;
134 if (uid == euid && gid == egid)
135 /* If we are not set-uid or set-gid, access does the same. */
136 return access (file, mode);
138 if (stat (file, &stats) != 0)
141 /* The super-user can read and write any file, and execute any file
142 that anyone can execute. */
143 if (euid == 0 && ((mode & X_OK) == 0
144 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
147 /* Convert the mode to traditional form, clearing any bogus bits. */
148 if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
151 mode = ((mode & R_OK ? 4 : 0)
152 + (mode & W_OK ? 2 : 0)
153 + (mode & X_OK ? 1 : 0));
156 return 0; /* The file exists. */
158 /* Convert the file's permission bits to traditional form. */
159 if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6)
160 && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3)
161 && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0))
162 granted = stats.st_mode;
164 granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0)
165 + (stats.st_mode & S_IWUSR ? 2 << 6 : 0)
166 + (stats.st_mode & S_IXUSR ? 1 << 6 : 0)
167 + (stats.st_mode & S_IRGRP ? 4 << 3 : 0)
168 + (stats.st_mode & S_IWGRP ? 2 << 3 : 0)
169 + (stats.st_mode & S_IXGRP ? 1 << 3 : 0)
170 + (stats.st_mode & S_IROTH ? 4 << 0 : 0)
171 + (stats.st_mode & S_IWOTH ? 2 << 0 : 0)
172 + (stats.st_mode & S_IXOTH ? 1 << 0 : 0));
174 if (euid == stats.st_uid)
176 else if (egid == stats.st_gid || group_member (stats.st_gid))
179 if ((mode & ~granted) == 0)
181 __set_errno (EACCESS);
189 weak_alias (__euidaccess, euidaccess)
200 main (int argc, char **argv)
206 program_name = argv[0];
210 mode = atoi (argv[2]);
212 err = euidaccess (file, mode);
213 printf ("%d\n", err);
215 error (0, errno, "%s", file);