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 2, or (at your option)
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 along
19 with this program; if not, write to the Free Software Foundation,
20 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
22 /* Written by David MacKenzie and Torbjorn Granlund.
23 Adapted for GNU C library by Roland McGrath. */
27 # include "euidaccess.h"
30 #include <sys/types.h>
40 # define __set_errno(val) errno = (val)
43 #if defined EACCES && !defined EACCESS
44 # define EACCESS EACCES
57 # define access __access
58 # define getuid __getuid
59 # define getgid __getgid
60 # define geteuid __geteuid
61 # define getegid __getegid
62 # define group_member __group_member
63 # define euidaccess __euidaccess
69 # include "group-member.h"
73 /* Return 0 if the user has permission of type MODE on FILE;
74 otherwise, return -1 and set `errno'.
75 Like access, except that it uses the effective user and group
76 id's instead of the real ones, and it does not always check for read-only
77 file system, text busy, etc. */
80 euidaccess (const char *file, int mode)
82 #if defined EFF_ONLY_OK
83 return access (file, mode | EFF_ONLY_OK);
84 #elif defined ACC_SELF
85 return accessx (file, mode, ACC_SELF);
87 return eaccess (file, mode);
90 uid_t uid = getuid ();
91 gid_t gid = getgid ();
92 uid_t euid = geteuid ();
93 gid_t egid = getegid ();
96 # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS
98 /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to
99 return the correct result even if this would make it
100 nonreentrant. Define this only if your entire application is
101 safe even if the uid or gid might temporarily change. If your
102 application uses signal handlers or threads it is probably not
106 return stat (file, &stats);
113 setreuid (euid, uid);
115 setregid (egid, gid);
117 result = access (file, mode);
122 setreuid (uid, euid);
124 setregid (gid, egid);
132 /* The following code assumes the traditional Unix model, and is not
133 correct on systems that have ACLs or the like. However, it's
134 better than nothing, and it is reentrant. */
136 unsigned int granted;
137 if (uid == euid && gid == egid)
138 /* If we are not set-uid or set-gid, access does the same. */
139 return access (file, mode);
141 if (stat (file, &stats) != 0)
144 /* The super-user can read and write any file, and execute any file
145 that anyone can execute. */
146 if (euid == 0 && ((mode & X_OK) == 0
147 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
150 /* Convert the mode to traditional form, clearing any bogus bits. */
151 if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
154 mode = ((mode & R_OK ? 4 : 0)
155 + (mode & W_OK ? 2 : 0)
156 + (mode & X_OK ? 1 : 0));
159 return 0; /* The file exists. */
161 /* Convert the file's permission bits to traditional form. */
162 if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6)
163 && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3)
164 && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0))
165 granted = stats.st_mode;
167 granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0)
168 + (stats.st_mode & S_IWUSR ? 2 << 6 : 0)
169 + (stats.st_mode & S_IXUSR ? 1 << 6 : 0)
170 + (stats.st_mode & S_IRGRP ? 4 << 3 : 0)
171 + (stats.st_mode & S_IWGRP ? 2 << 3 : 0)
172 + (stats.st_mode & S_IXGRP ? 1 << 3 : 0)
173 + (stats.st_mode & S_IROTH ? 4 << 0 : 0)
174 + (stats.st_mode & S_IWOTH ? 2 << 0 : 0)
175 + (stats.st_mode & S_IXOTH ? 1 << 0 : 0));
177 if (euid == stats.st_uid)
179 else if (egid == stats.st_gid || group_member (stats.st_gid))
182 if ((mode & ~granted) == 0)
184 __set_errno (EACCESS);
192 weak_alias (__euidaccess, euidaccess)
203 main (int argc, char **argv)
209 program_name = argv[0];
213 mode = atoi (argv[2]);
215 err = euidaccess (file, mode);
216 printf ("%d\n", err);
218 error (0, errno, "%s", file);