1 /* $NetBSD: t_ptrace.c,v 1.18 2017/01/13 21:30:41 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2016 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __RCSID("$NetBSD: t_ptrace.c,v 1.18 2017/01/13 21:30:41 christos Exp $");
31
32 #include <sys/param.h>
33 #include <sys/types.h>
34 #include <sys/ptrace.h>
35 #include <sys/stat.h>
36 #include <sys/sysctl.h>
37 #include <err.h>
38 #include <errno.h>
39 #include <unistd.h>
40
41 #include <atf-c.h>
42
43 #include "h_macros.h"
44
45 /*
46 * A child process cannot call atf functions and expect them to magically
47 * work like in the parent.
48 * The printf(3) messaging from a child will not work out of the box as well
49 * without estabilishing a communication protocol with its parent. To not
50 * overcomplicate the tests - do not log from a child and use err(3)/errx(3)
51 * wrapped with FORKEE_ASSERT()/FORKEE_ASSERTX() as that is guaranteed to work.
52 */
53 #define FORKEE_ASSERTX(x) \
54 do { \
55 int ret = (x); \
56 if (!ret) \
57 errx(EXIT_FAILURE, "%s:%d %s(): Assertion failed for: %s", \
58 __FILE__, __LINE__, __func__, #x); \
59 } while (0)
60
61 #define FORKEE_ASSERT(x) \
62 do { \
63 int ret = (x); \
64 if (!ret) \
65 err(EXIT_FAILURE, "%s:%d %s(): Assertion failed for: %s", \
66 __FILE__, __LINE__, __func__, #x); \
67 } while (0)
68
69 ATF_TC(attach_pid0);
ATF_TC_HEAD(attach_pid0,tc)70 ATF_TC_HEAD(attach_pid0, tc)
71 {
72 atf_tc_set_md_var(tc, "descr",
73 "Assert that a debugger cannot attach to PID 0");
74 }
75
ATF_TC_BODY(attach_pid0,tc)76 ATF_TC_BODY(attach_pid0, tc)
77 {
78 errno = 0;
79 ATF_REQUIRE_ERRNO(EPERM, ptrace(PT_ATTACH, 0, NULL, 0) == -1);
80 }
81
82 ATF_TC(attach_pid1);
ATF_TC_HEAD(attach_pid1,tc)83 ATF_TC_HEAD(attach_pid1, tc)
84 {
85 atf_tc_set_md_var(tc, "descr",
86 "Assert that a debugger cannot attach to PID 1 (as non-root)");
87
88 atf_tc_set_md_var(tc, "require.user", "unprivileged");
89 }
90
ATF_TC_BODY(attach_pid1,tc)91 ATF_TC_BODY(attach_pid1, tc)
92 {
93 ATF_REQUIRE_ERRNO(EPERM, ptrace(PT_ATTACH, 1, NULL, 0) == -1);
94 }
95
96 ATF_TC(attach_pid1_securelevel);
ATF_TC_HEAD(attach_pid1_securelevel,tc)97 ATF_TC_HEAD(attach_pid1_securelevel, tc)
98 {
99 atf_tc_set_md_var(tc, "descr",
100 "Assert that a debugger cannot attach to PID 1 with "
101 "securelevel >= 1 (as root)");
102
103 atf_tc_set_md_var(tc, "require.user", "root");
104 }
105
ATF_TC_BODY(attach_pid1_securelevel,tc)106 ATF_TC_BODY(attach_pid1_securelevel, tc)
107 {
108 int level;
109 size_t len = sizeof(level);
110
111 ATF_REQUIRE(sysctlbyname("kern.securelevel", &level, &len, NULL, 0)
112 != -1);
113
114 if (level < 1) {
115 atf_tc_skip("Test must be run with securelevel >= 1");
116 }
117
118 ATF_REQUIRE_ERRNO(EPERM, ptrace(PT_ATTACH, 1, NULL, 0) == -1);
119 }
120
121 ATF_TC(attach_self);
ATF_TC_HEAD(attach_self,tc)122 ATF_TC_HEAD(attach_self, tc)
123 {
124 atf_tc_set_md_var(tc, "descr",
125 "Assert that a debugger cannot attach to self (as it's nonsense)");
126 }
127
ATF_TC_BODY(attach_self,tc)128 ATF_TC_BODY(attach_self, tc)
129 {
130 ATF_REQUIRE_ERRNO(EINVAL, ptrace(PT_ATTACH, getpid(), NULL, 0) == -1);
131 }
132
133 ATF_TC(attach_chroot);
ATF_TC_HEAD(attach_chroot,tc)134 ATF_TC_HEAD(attach_chroot, tc)
135 {
136 atf_tc_set_md_var(tc, "descr",
137 "Assert that a debugger cannot trace another process unless the "
138 "process's root directory is at or below the tracing process's "
139 "root");
140
141 atf_tc_set_md_var(tc, "require.user", "root");
142 }
143
ATF_TC_BODY(attach_chroot,tc)144 ATF_TC_BODY(attach_chroot, tc)
145 {
146 char buf[PATH_MAX];
147 pid_t child;
148 int fds_toparent[2], fds_fromparent[2];
149 int rv;
150 uint8_t msg = 0xde; /* dummy message for IPC based on pipe(2) */
151
152 (void)memset(buf, '\0', sizeof(buf));
153 ATF_REQUIRE(getcwd(buf, sizeof(buf)) != NULL);
154 (void)strlcat(buf, "/dir", sizeof(buf));
155
156 ATF_REQUIRE(mkdir(buf, 0500) == 0);
157 ATF_REQUIRE(chdir(buf) == 0);
158
159 ATF_REQUIRE(pipe(fds_toparent) == 0);
160 ATF_REQUIRE(pipe(fds_fromparent) == 0);
161 child = atf_utils_fork();
162 if (child == 0) {
163 FORKEE_ASSERT(close(fds_toparent[0]) == 0);
164 FORKEE_ASSERT(close(fds_fromparent[1]) == 0);
165
166 FORKEE_ASSERT(chroot(buf) == 0);
167
168 rv = write(fds_toparent[1], &msg, sizeof(msg));
169 FORKEE_ASSERTX(rv == sizeof(msg));
170
171 ATF_REQUIRE_ERRNO(EPERM,
172 ptrace(PT_ATTACH, getppid(), NULL, 0) == -1);
173
174 rv = read(fds_fromparent[0], &msg, sizeof(msg));
175 FORKEE_ASSERTX(rv == sizeof(msg));
176
177 _exit(0);
178 }
179 ATF_REQUIRE(close(fds_toparent[1]) == 0);
180 ATF_REQUIRE(close(fds_fromparent[0]) == 0);
181
182 printf("Waiting for chrooting of the child PID %d", child);
183 rv = read(fds_toparent[0], &msg, sizeof(msg));
184 ATF_REQUIRE(rv == sizeof(msg));
185
186 printf("Child is ready, it will try to PT_ATTACH to parent\n");
187 rv = write(fds_fromparent[1], &msg, sizeof(msg));
188 ATF_REQUIRE(rv == sizeof(msg));
189
190 printf("fds_fromparent is no longer needed - close it\n");
191 ATF_REQUIRE(close(fds_fromparent[1]) == 0);
192
193 printf("fds_toparent is no longer needed - close it\n");
194 ATF_REQUIRE(close(fds_toparent[0]) == 0);
195 }
196
ATF_TP_ADD_TCS(tp)197 ATF_TP_ADD_TCS(tp)
198 {
199 setvbuf(stdout, NULL, _IONBF, 0);
200 setvbuf(stderr, NULL, _IONBF, 0);
201 ATF_TP_ADD_TC(tp, attach_pid0);
202 ATF_TP_ADD_TC(tp, attach_pid1);
203 ATF_TP_ADD_TC(tp, attach_pid1_securelevel);
204 ATF_TP_ADD_TC(tp, attach_self);
205 ATF_TP_ADD_TC(tp, attach_chroot);
206
207 return atf_no_error();
208 }
209