1 /* euidaccess -- check if effective user id can access file
3 Copyright (C) 1990, 1991, 1995, 1998, 2000, 2003, 2004, 2005, 2006, 2008
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. */
28 #include <sys/types.h>
38 # define __set_errno(val) errno = (val)
41 #if defined EACCES && !defined EACCESS
42 # define EACCESS EACCES
55 # define access __access
56 # define getuid __getuid
57 # define getgid __getgid
58 # define geteuid __geteuid
59 # define getegid __getegid
60 # define group_member __group_member
61 # define euidaccess __euidaccess
67 # include "group-member.h"
71 /* Return 0 if the user has permission of type MODE on FILE;
72 otherwise, return -1 and set `errno'.
73 Like access, except that it uses the effective user and group
74 id's instead of the real ones, and it does not always check for read-only
75 file system, text busy, etc. */
78 euidaccess (const char *file, int mode)
80 #if defined EFF_ONLY_OK
81 return access (file, mode | EFF_ONLY_OK);
82 #elif defined ACC_SELF
83 return accessx (file, mode, ACC_SELF);
85 return eaccess (file, mode);
88 uid_t uid = getuid ();
89 gid_t gid = getgid ();
90 uid_t euid = geteuid ();
91 gid_t egid = getegid ();
94 # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS
96 /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to
97 return the correct result even if this would make it
98 nonreentrant. Define this only if your entire application is
99 safe even if the uid or gid might temporarily change. If your
100 application uses signal handlers or threads it is probably not
104 return stat (file, &stats);
111 setreuid (euid, uid);
113 setregid (egid, gid);
115 result = access (file, mode);
120 setreuid (uid, euid);
122 setregid (gid, egid);
130 /* The following code assumes the traditional Unix model, and is not
131 correct on systems that have ACLs or the like. However, it's
132 better than nothing, and it is reentrant. */
134 unsigned int granted;
135 if (uid == euid && gid == egid)
136 /* If we are not set-uid or set-gid, access does the same. */
137 return access (file, mode);
139 if (stat (file, &stats) != 0)
142 /* The super-user can read and write any file, and execute any file
143 that anyone can execute. */
144 if (euid == 0 && ((mode & X_OK) == 0
145 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
148 /* Convert the mode to traditional form, clearing any bogus bits. */
149 if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
152 mode = ((mode & R_OK ? 4 : 0)
153 + (mode & W_OK ? 2 : 0)
154 + (mode & X_OK ? 1 : 0));
157 return 0; /* The file exists. */
159 /* Convert the file's permission bits to traditional form. */
160 if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6)
161 && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3)
162 && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0))
163 granted = stats.st_mode;
165 granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0)
166 + (stats.st_mode & S_IWUSR ? 2 << 6 : 0)
167 + (stats.st_mode & S_IXUSR ? 1 << 6 : 0)
168 + (stats.st_mode & S_IRGRP ? 4 << 3 : 0)
169 + (stats.st_mode & S_IWGRP ? 2 << 3 : 0)
170 + (stats.st_mode & S_IXGRP ? 1 << 3 : 0)
171 + (stats.st_mode & S_IROTH ? 4 << 0 : 0)
172 + (stats.st_mode & S_IWOTH ? 2 << 0 : 0)
173 + (stats.st_mode & S_IXOTH ? 1 << 0 : 0));
175 if (euid == stats.st_uid)
177 else if (egid == stats.st_gid || group_member (stats.st_gid))
180 if ((mode & ~granted) == 0)
182 __set_errno (EACCESS);
190 weak_alias (__euidaccess, euidaccess)
201 main (int argc, char **argv)
207 program_name = argv[0];
211 mode = atoi (argv[2]);
213 err = euidaccess (file, mode);
214 printf ("%d\n", err);
216 error (0, errno, "%s", file);