1/* $NetBSD: t_mprotect.c,v 1.3 2011/07/20 22:53:44 jym Exp $ */
2
3/*-
4 * Copyright (c) 2011 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jukka Ruohonen.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31#include <sys/cdefs.h>
32__RCSID("$NetBSD: t_mprotect.c,v 1.3 2011/07/20 22:53:44 jym Exp $");
33
34#include <sys/param.h>
35#include <sys/mman.h>
36#include <sys/sysctl.h>
37#include <sys/wait.h>
38
39#include <errno.h>
40#include <fcntl.h>
41#include <stdlib.h>
42#include <string.h>
43#include <unistd.h>
44
45#include <atf-c.h>
46
47#ifdef __NetBSD__
48#include "../common/exec_prot.h"
49#endif
50
51static long	page = 0;
52static int	pax_global = -1;
53static int	pax_enabled = -1;
54static char	path[] = "mmap";
55
56static void	sighandler(int);
57static bool	paxinit(void);
58static bool	paxset(int, int);
59
60static void
61sighandler(int signo)
62{
63	_exit(signo);
64}
65
66static bool
67paxinit(void)
68{
69	size_t len = sizeof(int);
70	int rv;
71
72	rv = sysctlbyname("security.pax.mprotect.global",
73	    &pax_global, &len, NULL, 0);
74
75	if (rv != 0)
76		return false;
77
78	rv = sysctlbyname("security.pax.mprotect.enabled",
79	    &pax_enabled, &len, NULL, 0);
80
81	if (rv != 0)
82		return false;
83
84	return paxset(1, 1);
85}
86
87static bool
88paxset(int global, int enabled)
89{
90	size_t len = sizeof(int);
91	int rv;
92
93	rv = sysctlbyname("security.pax.mprotect.global",
94	    NULL, NULL, &global, len);
95
96	if (rv != 0)
97		return false;
98
99	rv = sysctlbyname("security.pax.mprotect.enabled",
100	    NULL, NULL, &enabled, len);
101
102	if (rv != 0)
103		return false;
104
105	return true;
106}
107
108
109ATF_TC_WITH_CLEANUP(mprotect_access);
110ATF_TC_HEAD(mprotect_access, tc)
111{
112	atf_tc_set_md_var(tc, "descr", "Test for EACCES from mprotect(2)");
113}
114
115ATF_TC_BODY(mprotect_access, tc)
116{
117	int prot[2] = { PROT_NONE, PROT_READ };
118	void *map;
119	size_t i;
120	int fd;
121
122	fd = open(path, O_RDONLY | O_CREAT);
123	ATF_REQUIRE(fd >= 0);
124
125	/*
126	 * The call should fail with EACCES if we try to mark
127	 * a PROT_NONE or PROT_READ file/section as PROT_WRITE.
128	 */
129	for (i = 0; i < __arraycount(prot); i++) {
130
131		map = mmap(NULL, page, prot[i], MAP_SHARED, fd, 0);
132
133		if (map == MAP_FAILED)
134			continue;
135
136		errno = 0;
137
138		ATF_REQUIRE(mprotect(map, page, PROT_WRITE) != 0);
139		ATF_REQUIRE(errno == EACCES);
140		ATF_REQUIRE(munmap(map, page) == 0);
141	}
142
143	ATF_REQUIRE(close(fd) == 0);
144}
145
146ATF_TC_CLEANUP(mprotect_access, tc)
147{
148	(void)unlink(path);
149}
150
151ATF_TC(mprotect_err);
152ATF_TC_HEAD(mprotect_err, tc)
153{
154	atf_tc_set_md_var(tc, "descr", "Test error conditions of mprotect(2)");
155}
156
157ATF_TC_BODY(mprotect_err, tc)
158{
159	errno = 0;
160
161	ATF_REQUIRE(mprotect((char *)-1, 1, PROT_READ) != 0);
162	ATF_REQUIRE(errno == EINVAL);
163}
164
165#ifdef __NetBSD__
166ATF_TC(mprotect_exec);
167ATF_TC_HEAD(mprotect_exec, tc)
168{
169	atf_tc_set_md_var(tc, "descr",
170	    "Test mprotect(2) executable space protections");
171}
172
173/*
174 * Trivial function -- should fit into a page
175 */
176ATF_TC_BODY(mprotect_exec, tc)
177{
178	pid_t pid;
179	void *map;
180	int sta, xp_support;
181
182	xp_support = exec_prot_support();
183
184	switch (xp_support) {
185	case NOTIMPL:
186		atf_tc_skip(
187		    "Execute protection callback check not implemented");
188		break;
189	case NO_XP:
190		atf_tc_skip(
191		    "Host does not support executable space protection");
192		break;
193	case PARTIAL_XP: case PERPAGE_XP: default:
194		break;
195	}
196
197	/*
198	 * Map a page read/write and copy a trivial assembly function inside.
199	 * We will then change the mapping rights:
200	 * - first by setting the execution right, and check that we can
201	 *   call the code found in the allocated page.
202	 * - second by removing the execution right. This should generate
203	 *   a SIGSEGV on architectures that can enforce --x permissions.
204	 */
205
206	map = mmap(NULL, page, PROT_WRITE|PROT_READ, MAP_ANON, -1, 0);
207	ATF_REQUIRE(map != MAP_FAILED);
208
209	memcpy(map, (void *)return_one,
210	    (uintptr_t)return_one_end - (uintptr_t)return_one);
211
212	/* give r-x rights then call code in page */
213	ATF_REQUIRE(mprotect(map, page, PROT_EXEC|PROT_READ) == 0);
214	ATF_REQUIRE(((int (*)(void))map)() == 1);
215
216	/* remove --x right */
217	ATF_REQUIRE(mprotect(map, page, PROT_READ) == 0);
218
219	pid = fork();
220	ATF_REQUIRE(pid >= 0);
221
222	if (pid == 0) {
223		ATF_REQUIRE(signal(SIGSEGV, sighandler) != SIG_ERR);
224		ATF_CHECK(((int (*)(void))map)() == 1);
225		_exit(0);
226	}
227
228	(void)wait(&sta);
229
230	ATF_REQUIRE(munmap(map, page) == 0);
231
232	ATF_REQUIRE(WIFEXITED(sta) != 0);
233
234	switch (xp_support) {
235	case PARTIAL_XP:
236		/* Partial protection might fail; skip the test when it does */
237		if (WEXITSTATUS(sta) != SIGSEGV) {
238			atf_tc_skip("Host only supports "
239			    "partial executable space protection");
240		}
241		break;
242	case PERPAGE_XP: default:
243		/* Per-page --x protection should not fail */
244		ATF_REQUIRE(WEXITSTATUS(sta) == SIGSEGV);
245		break;
246	}
247}
248#endif
249
250ATF_TC(mprotect_pax);
251ATF_TC_HEAD(mprotect_pax, tc)
252{
253	atf_tc_set_md_var(tc, "descr", "PaX restrictions and mprotect(2)");
254	atf_tc_set_md_var(tc, "require.user", "root");
255}
256
257ATF_TC_BODY(mprotect_pax, tc)
258{
259	const int prot[4] = { PROT_NONE, PROT_READ, PROT_WRITE };
260	const char *str = NULL;
261	void *map;
262	size_t i;
263	int rv;
264
265	if (paxinit() != true)
266		return;
267
268	/*
269	 * As noted in the original PaX documentation [1],
270	 * the following restrictions should apply:
271	 *
272	 *   (1) creating executable anonymous mappings
273	 *
274	 *   (2) creating executable/writable file mappings
275	 *
276	 *   (3) making a non-executable mapping executable
277	 *
278	 *   (4) making an executable/read-only file mapping
279	 *       writable except for performing relocations
280	 *       on an ET_DYN ELF file (non-PIC shared library)
281	 *
282	 *  The following will test only the case (3).
283	 *
284	 * [1] http://pax.grsecurity.net/docs/mprotect.txt
285	 *
286	 *     (Sun Apr 3 11:06:53 EEST 2011.)
287	 */
288	for (i = 0; i < __arraycount(prot); i++) {
289
290		map = mmap(NULL, page, prot[i], MAP_ANON, -1, 0);
291
292		if (map == MAP_FAILED)
293			continue;
294
295		rv = mprotect(map, 1, prot[i] | PROT_EXEC);
296
297		(void)munmap(map, page);
298
299		if (rv == 0) {
300			str = "non-executable mapping made executable";
301			goto out;
302		}
303	}
304
305out:
306	if (pax_global != -1 && pax_enabled != -1)
307		(void)paxset(pax_global, pax_enabled);
308
309	if (str != NULL)
310		atf_tc_fail("%s", str);
311}
312
313ATF_TC(mprotect_write);
314ATF_TC_HEAD(mprotect_write, tc)
315{
316	atf_tc_set_md_var(tc, "descr", "Test mprotect(2) write protections");
317}
318
319ATF_TC_BODY(mprotect_write, tc)
320{
321	pid_t pid;
322	void *map;
323	int sta;
324
325	/*
326	 * Map a page read/write, change the protection
327	 * to read-only with mprotect(2), and try to write
328	 * to the page. This should generate a SIGSEGV.
329	 */
330	map = mmap(NULL, page, PROT_WRITE|PROT_READ, MAP_ANON, -1, 0);
331	ATF_REQUIRE(map != MAP_FAILED);
332
333	ATF_REQUIRE(strlcpy(map, "XXX", 3) == 3);
334	ATF_REQUIRE(mprotect(map, page, PROT_READ) == 0);
335
336	pid = fork();
337	ATF_REQUIRE(pid >= 0);
338
339	if (pid == 0) {
340		ATF_REQUIRE(signal(SIGSEGV, sighandler) != SIG_ERR);
341		ATF_REQUIRE(strlcpy(map, "XXX", 3) == 0);
342	}
343
344	(void)wait(&sta);
345
346	ATF_REQUIRE(WIFEXITED(sta) != 0);
347	ATF_REQUIRE(WEXITSTATUS(sta) == SIGSEGV);
348	ATF_REQUIRE(munmap(map, page) == 0);
349}
350
351ATF_TP_ADD_TCS(tp)
352{
353	page = sysconf(_SC_PAGESIZE);
354	ATF_REQUIRE(page >= 0);
355
356	ATF_TP_ADD_TC(tp, mprotect_access);
357	ATF_TP_ADD_TC(tp, mprotect_err);
358#ifdef __NetBSD__
359	ATF_TP_ADD_TC(tp, mprotect_exec);
360#endif
361	ATF_TP_ADD_TC(tp, mprotect_pax);
362	ATF_TP_ADD_TC(tp, mprotect_write);
363
364	return atf_no_error();
365}
366