1 /* euidaccess -- check if effective user id can access file
3 Copyright (C) 1990, 1991, 1995, 1998, 2000, 2003, 2004, 2005, 2006
4 Free 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. */
26 # include "euidaccess.h"
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 # include "group-member.h"
72 /* Return 0 if the user has permission of type MODE on FILE;
73 otherwise, return -1 and set `errno'.
74 Like access, except that it uses the effective user and group
75 id's instead of the real ones, and it does not always check for read-only
76 file system, text busy, etc. */
79 euidaccess (const char *file, int mode)
81 #if defined EFF_ONLY_OK
82 return access (file, mode | EFF_ONLY_OK);
83 #elif defined ACC_SELF
84 return accessx (file, mode, ACC_SELF);
86 return eaccess (file, mode);
89 uid_t uid = getuid ();
90 gid_t gid = getgid ();
91 uid_t euid = geteuid ();
92 gid_t egid = getegid ();
95 # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS
97 /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to
98 return the correct result even if this would make it
99 nonreentrant. Define this only if your entire application is
100 safe even if the uid or gid might temporarily change. If your
101 application uses signal handlers or threads it is probably not
105 return stat (file, &stats);
112 setreuid (euid, uid);
114 setregid (egid, gid);
116 result = access (file, mode);
121 setreuid (uid, euid);
123 setregid (gid, egid);
131 /* The following code assumes the traditional Unix model, and is not
132 correct on systems that have ACLs or the like. However, it's
133 better than nothing, and it is reentrant. */
135 unsigned int granted;
136 if (uid == euid && gid == egid)
137 /* If we are not set-uid or set-gid, access does the same. */
138 return access (file, mode);
140 if (stat (file, &stats) != 0)
143 /* The super-user can read and write any file, and execute any file
144 that anyone can execute. */
145 if (euid == 0 && ((mode & X_OK) == 0
146 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
149 /* Convert the mode to traditional form, clearing any bogus bits. */
150 if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
153 mode = ((mode & R_OK ? 4 : 0)
154 + (mode & W_OK ? 2 : 0)
155 + (mode & X_OK ? 1 : 0));
158 return 0; /* The file exists. */
160 /* Convert the file's permission bits to traditional form. */
161 if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6)
162 && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3)
163 && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0))
164 granted = stats.st_mode;
166 granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0)
167 + (stats.st_mode & S_IWUSR ? 2 << 6 : 0)
168 + (stats.st_mode & S_IXUSR ? 1 << 6 : 0)
169 + (stats.st_mode & S_IRGRP ? 4 << 3 : 0)
170 + (stats.st_mode & S_IWGRP ? 2 << 3 : 0)
171 + (stats.st_mode & S_IXGRP ? 1 << 3 : 0)
172 + (stats.st_mode & S_IROTH ? 4 << 0 : 0)
173 + (stats.st_mode & S_IWOTH ? 2 << 0 : 0)
174 + (stats.st_mode & S_IXOTH ? 1 << 0 : 0));
176 if (euid == stats.st_uid)
178 else if (egid == stats.st_gid || group_member (stats.st_gid))
181 if ((mode & ~granted) == 0)
183 __set_errno (EACCESS);
191 weak_alias (__euidaccess, euidaccess)
202 main (int argc, char **argv)
208 program_name = argv[0];
212 mode = atoi (argv[2]);
214 err = euidaccess (file, mode);
215 printf ("%d\n", err);
217 error (0, errno, "%s", file);