1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2019 The FreeBSD Foundation
5 *
6 * This software was developed by BFF Storage Systems, LLC under sponsorship
7 * from the FreeBSD Foundation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 * $FreeBSD: stable/12/tests/sys/fs/fusefs/allow_other.cc 368596 2020-12-12 22:57:28Z asomers $
31 */
32
33 /*
34 * Tests for the "allow_other" mount option. They must be in their own
35 * file so they can be run as root
36 */
37
38 extern "C" {
39 #include <sys/types.h>
40 #include <sys/extattr.h>
41 #include <sys/wait.h>
42 #include <fcntl.h>
43 #include <unistd.h>
44 }
45
46 #include "mockfs.hh"
47 #include "utils.hh"
48
49 using namespace testing;
50
51 const static char FULLPATH[] = "mountpoint/some_file.txt";
52 const static char RELPATH[] = "some_file.txt";
53
54 class NoAllowOther: public FuseTest {
55
56 public:
57 /* Unprivileged user id */
58 int m_uid;
59
SetUp()60 virtual void SetUp() {
61 if (geteuid() != 0) {
62 GTEST_SKIP() << "This test must be run as root";
63 }
64
65 FuseTest::SetUp();
66 }
67 };
68
69 class AllowOther: public NoAllowOther {
70
71 public:
SetUp()72 virtual void SetUp() {
73 m_allow_other = true;
74 NoAllowOther::SetUp();
75 }
76 };
77
TEST_F(AllowOther,allowed)78 TEST_F(AllowOther, allowed)
79 {
80 int status;
81
82 fork(true, &status, [&] {
83 uint64_t ino = 42;
84
85 expect_lookup(RELPATH, ino, S_IFREG | 0644, 0, 1);
86 expect_open(ino, 0, 1);
87 expect_flush(ino, 1, ReturnErrno(0));
88 expect_release(ino, FH);
89 }, []() {
90 int fd;
91
92 fd = open(FULLPATH, O_RDONLY);
93 if (fd < 0) {
94 perror("open");
95 return(1);
96 }
97 return 0;
98 }
99 );
100 ASSERT_EQ(0, WEXITSTATUS(status));
101 }
102
103 /* Check that fusefs uses the correct credentials for FUSE operations */
TEST_F(AllowOther,creds)104 TEST_F(AllowOther, creds)
105 {
106 int status;
107 uid_t uid;
108 gid_t gid;
109
110 get_unprivileged_id(&uid, &gid);
111 fork(true, &status, [=] {
112 EXPECT_CALL(*m_mock, process( ResultOf([=](auto in) {
113 return (in.header.opcode == FUSE_LOOKUP &&
114 in.header.uid == uid &&
115 in.header.gid == gid);
116 }, Eq(true)),
117 _)
118 ).Times(1)
119 .WillOnce(Invoke(ReturnErrno(ENOENT)));
120 }, []() {
121 eaccess(FULLPATH, F_OK);
122 return 0;
123 }
124 );
125 ASSERT_EQ(0, WEXITSTATUS(status));
126 }
127
128 /*
129 * A variation of the Open.multiple_creds test showing how the bug can lead to a
130 * privilege elevation. The first process is privileged and opens a file only
131 * visible to root. The second process is unprivileged and shouldn't be able
132 * to open the file, but does thanks to the bug
133 */
TEST_F(AllowOther,privilege_escalation)134 TEST_F(AllowOther, privilege_escalation)
135 {
136 int fd1, status;
137 const static uint64_t ino = 42;
138 const static uint64_t fh = 100;
139
140 /* Fork a child to open the file with different credentials */
141 fork(true, &status, [&] {
142
143 expect_lookup(RELPATH, ino, S_IFREG | 0600, 0, 2);
144 EXPECT_CALL(*m_mock, process(
145 ResultOf([=](auto in) {
146 return (in.header.opcode == FUSE_OPEN &&
147 in.header.pid == (uint32_t)getpid() &&
148 in.header.uid == (uint32_t)geteuid() &&
149 in.header.nodeid == ino);
150 }, Eq(true)),
151 _)
152 ).WillOnce(Invoke(
153 ReturnImmediate([](auto in __unused, auto& out) {
154 out.body.open.fh = fh;
155 out.header.len = sizeof(out.header);
156 SET_OUT_HEADER_LEN(out, open);
157 })));
158
159 EXPECT_CALL(*m_mock, process(
160 ResultOf([=](auto in) {
161 return (in.header.opcode == FUSE_OPEN &&
162 in.header.pid != (uint32_t)getpid() &&
163 in.header.uid != (uint32_t)geteuid() &&
164 in.header.nodeid == ino);
165 }, Eq(true)),
166 _)
167 ).Times(AnyNumber())
168 .WillRepeatedly(Invoke(ReturnErrno(EPERM)));
169
170 fd1 = open(FULLPATH, O_RDONLY);
171 ASSERT_LE(0, fd1) << strerror(errno);
172 }, [] {
173 int fd0;
174
175 fd0 = open(FULLPATH, O_RDONLY);
176 if (fd0 >= 0) {
177 fprintf(stderr, "Privilege escalation!\n");
178 return 1;
179 }
180 if (errno != EPERM) {
181 fprintf(stderr, "Unexpected error %s\n",
182 strerror(errno));
183 return 1;
184 }
185 leak(fd0);
186 return 0;
187 }
188 );
189 ASSERT_EQ(0, WEXITSTATUS(status));
190 leak(fd1);
191 }
192
TEST_F(NoAllowOther,disallowed)193 TEST_F(NoAllowOther, disallowed)
194 {
195 int status;
196
197 fork(true, &status, [] {
198 }, []() {
199 int fd;
200
201 fd = open(FULLPATH, O_RDONLY);
202 if (fd >= 0) {
203 fprintf(stderr, "open should've failed\n");
204 return(1);
205 } else if (errno != EPERM) {
206 fprintf(stderr, "Unexpected error: %s\n",
207 strerror(errno));
208 return(1);
209 }
210 return 0;
211 }
212 );
213 ASSERT_EQ(0, WEXITSTATUS(status));
214 }
215
216 /*
217 * When -o allow_other is not used, users other than the owner aren't allowed
218 * to open anything inside of the mount point, not just the mountpoint itself
219 * This is a regression test for bug 237052
220 */
TEST_F(NoAllowOther,disallowed_beneath_root)221 TEST_F(NoAllowOther, disallowed_beneath_root)
222 {
223 const static char RELPATH2[] = "other_dir";
224 const static uint64_t ino = 42;
225 const static uint64_t ino2 = 43;
226 int dfd, status;
227
228 expect_lookup(RELPATH, ino, S_IFDIR | 0755, 0, 1);
229 EXPECT_LOOKUP(ino, RELPATH2)
230 .WillRepeatedly(Invoke(ReturnImmediate([=](auto in __unused, auto& out) {
231 SET_OUT_HEADER_LEN(out, entry);
232 out.body.entry.attr.mode = S_IFREG | 0644;
233 out.body.entry.nodeid = ino2;
234 out.body.entry.attr.nlink = 1;
235 out.body.entry.attr_valid = UINT64_MAX;
236 })));
237 expect_opendir(ino);
238 dfd = open(FULLPATH, O_DIRECTORY);
239 ASSERT_LE(0, dfd) << strerror(errno);
240
241 fork(true, &status, [] {
242 }, [&]() {
243 int fd;
244
245 fd = openat(dfd, RELPATH2, O_RDONLY);
246 if (fd >= 0) {
247 fprintf(stderr, "openat should've failed\n");
248 return(1);
249 } else if (errno != EPERM) {
250 fprintf(stderr, "Unexpected error: %s\n",
251 strerror(errno));
252 return(1);
253 }
254 return 0;
255 }
256 );
257 ASSERT_EQ(0, WEXITSTATUS(status));
258
259 leak(dfd);
260 }
261
262 /*
263 * Provide coverage for the extattr methods, which have a slightly different
264 * code path
265 */
TEST_F(NoAllowOther,setextattr)266 TEST_F(NoAllowOther, setextattr)
267 {
268 int ino = 42, status;
269
270 fork(true, &status, [&] {
271 EXPECT_LOOKUP(FUSE_ROOT_ID, RELPATH)
272 .WillOnce(Invoke(
273 ReturnImmediate([=](auto in __unused, auto& out) {
274 SET_OUT_HEADER_LEN(out, entry);
275 out.body.entry.attr_valid = UINT64_MAX;
276 out.body.entry.entry_valid = UINT64_MAX;
277 out.body.entry.attr.mode = S_IFREG | 0644;
278 out.body.entry.nodeid = ino;
279 })));
280
281 /*
282 * lookup the file to get it into the cache.
283 * Otherwise, the unprivileged lookup will fail with
284 * EACCES
285 */
286 ASSERT_EQ(0, access(FULLPATH, F_OK)) << strerror(errno);
287 }, [&]() {
288 const char value[] = "whatever";
289 ssize_t value_len = strlen(value) + 1;
290 int ns = EXTATTR_NAMESPACE_USER;
291 ssize_t r;
292
293 r = extattr_set_file(FULLPATH, ns, "foo",
294 (const void*)value, value_len);
295 if (r >= 0) {
296 fprintf(stderr, "should've failed\n");
297 return(1);
298 } else if (errno != EPERM) {
299 fprintf(stderr, "Unexpected error: %s\n",
300 strerror(errno));
301 return(1);
302 }
303 return 0;
304 }
305 );
306 ASSERT_EQ(0, WEXITSTATUS(status));
307 }
308