priv_vfs_chown.c revision 162271 
1/*-
2 * Copyright (c) 2006 nCircle Network Security, Inc.
3 * All rights reserved.
4 *
5 * This software was developed by Robert N. M. Watson for the TrustedBSD
6 * Project under contract to nCircle Network Security, Inc.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR, NCIRCLE NETWORK SECURITY,
21 * INC., OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
23 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
24 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
25 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
26 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * $FreeBSD: head/tools/regression/priv/priv_vfs_chown.c 162271 2006-09-13 09:05:39Z rwatson $
30 */
31
32/*
33 * Confirm that privilege is required in the cases using chown():
34 *
35 * - If the process euid does not match the file uid.
36 *
37 * - If the target uid is different than the current uid.
38 *
39 * - If the target gid changes and we the process is not a member of the new
40 *   group.
41 */
42
43#include <sys/types.h>
44#include <sys/stat.h>
45
46#include <err.h>
47#include <errno.h>
48#include <stdio.h>
49#include <unistd.h>
50
51#include "main.h"
52
53const gid_t gidset[] = {GID_WHEEL, GID_OWNER};
54
55void
56priv_vfs_chown(void)
57{
58	char fpath[1024];
59	int error;
60
61	assert_root();
62
63	/*
64	 * Before beginning, set up group set for process.  Place in wheel
65	 * and owner groups; don't put in other group so that when we chown
66	 * to the other group, it's as a non-member.
67	 */
68	if (setgroups(2, gidset) < 0)
69		err(-1, "setgroups(2, {%d, %d})", GID_WHEEL, GID_OWNER);
70
71	/*
72	 * In the first pass, confirm that all works as desired with
73	 * privilege.
74	 *
75	 * Check that chown when non-owner works fine.  Do a no-op change to
76	 * avoid other permission checks.  Note that we can't request
77	 * (-1, -1) and get an access control check, we have to request
78	 * specific uid/gid that are not the same.
79	 */
80	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
81	if (chown(fpath, -1, GID_OWNER) < 0) {
82		warn("chown(%s, -1, %d) as root", fpath, GID_OWNER);
83		goto out;
84	}
85	(void)unlink(fpath);
86
87	/*
88	 * Check that chown changing uid works with privilege.
89	 */
90	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
91	if (chown(fpath, UID_OTHER, -1) < 0) {
92		warn("chown(%s, %d, -1) as root", fpath, UID_OTHER);
93		goto out;
94	}
95	(void)unlink(fpath);
96
97	/*
98	 * Check that can change the file group to one we are not a member of
99	 * when running with privilege.
100	 */
101	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
102	if (chown(fpath, -1, GID_OTHER) < 0) {
103		warn("chown(%s, -1, %d) as root", fpath, GID_OTHER);
104		goto out;
105	}
106	(void)unlink(fpath);
107
108	/*
109	 * Now, the same again, but without privilege.
110	 *
111	 * Confirm that we can't chown a file we don't own, even as a no-op.
112	 */
113	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
114	set_euid(UID_OTHER);
115	error = chown(fpath, -1, GID_OWNER);
116	if (error == 0) {
117		warnx("chown(%s, -1, %d) succeeded as !root, non-owner",
118		    fpath, GID_OWNER);
119		goto out;
120	}
121	if (errno != EPERM) {
122		warn("chown(%s, -1, %d) wrong errno %d as !root, non-owner",
123		    fpath, GID_OWNER, errno);
124		goto out;
125	}
126	set_euid(UID_ROOT);
127	(void)unlink(fpath);
128
129	/*
130	 * Check that we can't change the uid of the file without privilege,
131	 * even though we own the file.
132	 */
133	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
134	set_euid(UID_OWNER);
135	error = chown(fpath, UID_OTHER, -1);
136	if (error == 0) {
137		warnx("chown(%s, %d, -1) succeeded as !root", fpath,
138		    UID_OTHER);
139		goto out;
140	}
141	if (errno != EPERM) {
142		warn("chown(%s, %d, -1) wrong errno %d as !root", fpath,
143		    UID_OTHER, errno);
144		goto out;
145	}
146	set_euid(UID_ROOT);
147	(void)unlink(fpath);
148
149	/*
150	 * Check that can't change the file group to one we are not a member
151	 * of when running without privilege.
152	 */
153	setup_file(fpath, UID_OWNER, GID_OWNER, 0600);
154	set_euid(UID_OWNER);
155	error = chown(fpath, -1, GID_OTHER);
156	if (error == 0) {
157		warn("chown(%s, -1, %d) succeeded as !root", fpath, GID_OTHER);
158		goto out;
159	}
160	if (errno != EPERM) {
161		warn("chown(%s, -1, %d) wrong errno %d as !root", fpath,
162		    errno, GID_OTHER);
163		goto out;
164	}
165	set_euid(UID_ROOT);
166	(void)unlink(fpath);
167out:
168	(void)seteuid(UID_ROOT);
169	(void)unlink(fpath);
170}
171