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