1 /*
2 * Copyright 2006, The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #define LOG_TAG "crasher"
18
19 #include <assert.h>
20 #include <dirent.h>
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <pthread.h>
24 #include <signal.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <sys/mman.h>
29 #include <sys/prctl.h>
30 #include <unistd.h>
31
32 // We test both kinds of logging.
33 #include <android-base/logging.h>
34 #include <log/log.h>
35
36 #include "seccomp_policy.h"
37
38 #if defined(STATIC_CRASHER)
39 #include "debuggerd/handler.h"
40 #endif
41
42 #if defined(__arm__)
43 // See https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt for details.
44 #define __kuser_helper_version (*(int32_t*) 0xffff0ffc)
45 typedef void * (__kuser_get_tls_t)(void);
46 #define __kuser_get_tls (*(__kuser_get_tls_t*) 0xffff0fe0)
47 typedef int (__kuser_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
48 #define __kuser_cmpxchg (*(__kuser_cmpxchg_t*) 0xffff0fc0)
49 typedef void (__kuser_dmb_t)(void);
50 #define __kuser_dmb (*(__kuser_dmb_t*) 0xffff0fa0)
51 typedef int (__kuser_cmpxchg64_t)(const int64_t*, const int64_t*, volatile int64_t*);
52 #define __kuser_cmpxchg64 (*(__kuser_cmpxchg64_t*) 0xffff0f60)
53 #endif
54
55 #define noinline __attribute__((__noinline__))
56
57 // Avoid name mangling so that stacks are more readable.
58 extern "C" {
59
60 void crash1(void);
61 void crashnostack(void);
62
63 int do_action(const char* arg);
64
maybe_abort()65 noinline void maybe_abort() {
66 if (time(0) != 42) {
67 abort();
68 }
69 }
70
71 char* smash_stack_dummy_buf;
smash_stack_dummy_function(volatile int * plen)72 noinline void smash_stack_dummy_function(volatile int* plen) {
73 smash_stack_dummy_buf[*plen] = 0;
74 }
75
76 // This must be marked with "__attribute__ ((noinline))", to ensure the
77 // compiler generates the proper stack guards around this function.
78 // Assign local array address to global variable to force stack guards.
79 // Use another noinline function to corrupt the stack.
smash_stack(volatile int * plen)80 noinline int smash_stack(volatile int* plen) {
81 printf("%s: deliberately corrupting stack...\n", getprogname());
82
83 char buf[128];
84 smash_stack_dummy_buf = buf;
85 // This should corrupt stack guards and make process abort.
86 smash_stack_dummy_function(plen);
87 return 0;
88 }
89
90 #pragma clang diagnostic push
91 #pragma clang diagnostic ignored "-Winfinite-recursion"
92
93 void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.
94
overflow_stack(void * p)95 noinline void overflow_stack(void* p) {
96 void* buf[1];
97 buf[0] = p;
98 global = buf;
99 overflow_stack(&buf);
100 }
101
102 #pragma clang diagnostic pop
103
thread_callback(void * raw_arg)104 noinline void* thread_callback(void* raw_arg) {
105 const char* arg = reinterpret_cast<const char*>(raw_arg);
106 return reinterpret_cast<void*>(static_cast<uintptr_t>(do_action(arg)));
107 }
108
do_action_on_thread(const char * arg)109 noinline int do_action_on_thread(const char* arg) {
110 pthread_t t;
111 pthread_create(&t, nullptr, thread_callback, const_cast<char*>(arg));
112 void* result = nullptr;
113 pthread_join(t, &result);
114 return reinterpret_cast<uintptr_t>(result);
115 }
116
crash3(int a)117 noinline int crash3(int a) {
118 *reinterpret_cast<int*>(0xdead) = a;
119 return a*4;
120 }
121
crash2(int a)122 noinline int crash2(int a) {
123 a = crash3(a) + 2;
124 return a*3;
125 }
126
crash(int a)127 noinline int crash(int a) {
128 a = crash2(a) + 1;
129 return a*2;
130 }
131
abuse_heap()132 noinline void abuse_heap() {
133 char buf[16];
134 free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
135 }
136
sigsegv_non_null()137 noinline void sigsegv_non_null() {
138 int* a = (int *)(&do_action);
139 *a = 42;
140 }
141
fprintf_null()142 noinline void fprintf_null() {
143 fprintf(nullptr, "oops");
144 }
145
readdir_null()146 noinline void readdir_null() {
147 readdir(nullptr);
148 }
149
strlen_null()150 noinline int strlen_null() {
151 char* sneaky_null = nullptr;
152 return strlen(sneaky_null);
153 }
154
usage()155 static int usage() {
156 fprintf(stderr, "usage: %s KIND\n", getprogname());
157 fprintf(stderr, "\n");
158 fprintf(stderr, "where KIND is:\n");
159 fprintf(stderr, " smash-stack overwrite a -fstack-protector guard\n");
160 fprintf(stderr, " stack-overflow recurse until the stack overflows\n");
161 fprintf(stderr, " nostack crash with a NULL stack pointer\n");
162 fprintf(stderr, "\n");
163 fprintf(stderr, " heap-corruption cause a libc abort by corrupting the heap\n");
164 fprintf(stderr, " heap-usage cause a libc abort by abusing a heap function\n");
165 fprintf(stderr, "\n");
166 fprintf(stderr, " abort call abort()\n");
167 fprintf(stderr, " assert call assert() without a function\n");
168 fprintf(stderr, " assert2 call assert() with a function\n");
169 fprintf(stderr, " exit call exit(1)\n");
170 fprintf(stderr, "\n");
171 fprintf(stderr, " fortify fail a _FORTIFY_SOURCE check\n");
172 fprintf(stderr, " seccomp fail a seccomp check\n");
173 #if defined(__arm__)
174 fprintf(stderr, " kuser_helper_version call kuser_helper_version\n");
175 fprintf(stderr, " kuser_get_tls call kuser_get_tls\n");
176 fprintf(stderr, " kuser_cmpxchg call kuser_cmpxchg\n");
177 fprintf(stderr, " kuser_memory_barrier call kuser_memory_barrier\n");
178 fprintf(stderr, " kuser_cmpxchg64 call kuser_cmpxchg64\n");
179 #endif
180 fprintf(stderr, "\n");
181 fprintf(stderr, " LOG_ALWAYS_FATAL call liblog LOG_ALWAYS_FATAL\n");
182 fprintf(stderr, " LOG_ALWAYS_FATAL_IF call liblog LOG_ALWAYS_FATAL_IF\n");
183 fprintf(stderr, " LOG-FATAL call libbase LOG(FATAL)\n");
184 fprintf(stderr, "\n");
185 fprintf(stderr, " SIGFPE cause a SIGFPE\n");
186 fprintf(stderr, " SIGSEGV cause a SIGSEGV at address 0x0 (synonym: crash)\n");
187 fprintf(stderr, " SIGSEGV-non-null cause a SIGSEGV at a non-zero address\n");
188 fprintf(stderr, " SIGSEGV-unmapped mmap/munmap a region of memory and then attempt to access it\n");
189 fprintf(stderr, " SIGTRAP cause a SIGTRAP\n");
190 fprintf(stderr, "\n");
191 fprintf(stderr, " fprintf-NULL pass a null pointer to fprintf\n");
192 fprintf(stderr, " readdir-NULL pass a null pointer to readdir\n");
193 fprintf(stderr, " strlen-NULL pass a null pointer to strlen\n");
194 fprintf(stderr, " pthread_join-NULL pass a null pointer to pthread_join\n");
195 fprintf(stderr, "\n");
196 fprintf(stderr, " no_new_privs set PR_SET_NO_NEW_PRIVS and then abort\n");
197 fprintf(stderr, "\n");
198 fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n");
199 fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
200 fprintf(stderr, "all available file descriptors before crashing.\n");
201 fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n");
202
203 return EXIT_FAILURE;
204 }
205
do_action(const char * arg)206 noinline int do_action(const char* arg) {
207 // Prefixes.
208 if (!strncmp(arg, "wait-", strlen("wait-"))) {
209 char buf[1];
210 TEMP_FAILURE_RETRY(read(STDIN_FILENO, buf, sizeof(buf)));
211 return do_action(arg + strlen("wait-"));
212 } else if (!strncmp(arg, "exhaustfd-", strlen("exhaustfd-"))) {
213 errno = 0;
214 while (errno != EMFILE) {
215 open("/dev/null", O_RDONLY);
216 }
217 return do_action(arg + strlen("exhaustfd-"));
218 } else if (!strncmp(arg, "thread-", strlen("thread-"))) {
219 return do_action_on_thread(arg + strlen("thread-"));
220 }
221
222 // Actions.
223 if (!strcasecmp(arg, "SIGSEGV-non-null")) {
224 sigsegv_non_null();
225 } else if (!strcasecmp(arg, "smash-stack")) {
226 volatile int len = 128;
227 return smash_stack(&len);
228 } else if (!strcasecmp(arg, "stack-overflow")) {
229 overflow_stack(nullptr);
230 } else if (!strcasecmp(arg, "nostack")) {
231 crashnostack();
232 } else if (!strcasecmp(arg, "exit")) {
233 exit(1);
234 } else if (!strcasecmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) {
235 return crash(42);
236 } else if (!strcasecmp(arg, "abort")) {
237 maybe_abort();
238 } else if (!strcasecmp(arg, "assert")) {
239 __assert("some_file.c", 123, "false");
240 } else if (!strcasecmp(arg, "assert2")) {
241 __assert2("some_file.c", 123, "some_function", "false");
242 } else if (!strcasecmp(arg, "fortify")) {
243 char buf[10];
244 __read_chk(-1, buf, 32, 10);
245 while (true) pause();
246 } else if (!strcasecmp(arg, "LOG(FATAL)")) {
247 LOG(FATAL) << "hello " << 123;
248 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL")) {
249 LOG_ALWAYS_FATAL("hello %s", "world");
250 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL_IF")) {
251 LOG_ALWAYS_FATAL_IF(true, "hello %s", "world");
252 } else if (!strcasecmp(arg, "SIGFPE")) {
253 raise(SIGFPE);
254 return EXIT_SUCCESS;
255 } else if (!strcasecmp(arg, "SIGTRAP")) {
256 raise(SIGTRAP);
257 return EXIT_SUCCESS;
258 } else if (!strcasecmp(arg, "fprintf-NULL")) {
259 fprintf_null();
260 } else if (!strcasecmp(arg, "readdir-NULL")) {
261 readdir_null();
262 } else if (!strcasecmp(arg, "strlen-NULL")) {
263 return strlen_null();
264 } else if (!strcasecmp(arg, "pthread_join-NULL")) {
265 return pthread_join(0, nullptr);
266 } else if (!strcasecmp(arg, "heap-usage")) {
267 abuse_heap();
268 } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) {
269 char* map = reinterpret_cast<char*>(mmap(nullptr, sizeof(int), PROT_READ | PROT_WRITE,
270 MAP_SHARED | MAP_ANONYMOUS, -1, 0));
271 munmap(map, sizeof(int));
272 map[0] = '8';
273 } else if (!strcasecmp(arg, "seccomp")) {
274 set_seccomp_filter();
275 syscall(99999);
276 #if defined(__arm__)
277 } else if (!strcasecmp(arg, "kuser_helper_version")) {
278 return __kuser_helper_version;
279 } else if (!strcasecmp(arg, "kuser_get_tls")) {
280 return !__kuser_get_tls();
281 } else if (!strcasecmp(arg, "kuser_cmpxchg")) {
282 return __kuser_cmpxchg(0, 0, 0);
283 } else if (!strcasecmp(arg, "kuser_memory_barrier")) {
284 __kuser_dmb();
285 } else if (!strcasecmp(arg, "kuser_cmpxchg64")) {
286 return __kuser_cmpxchg64(0, 0, 0);
287 #endif
288 } else if (!strcasecmp(arg, "no_new_privs")) {
289 if (prctl(PR_SET_NO_NEW_PRIVS, 1) != 0) {
290 fprintf(stderr, "prctl(PR_SET_NO_NEW_PRIVS, 1) failed: %s\n", strerror(errno));
291 return EXIT_SUCCESS;
292 }
293 abort();
294 } else {
295 return usage();
296 }
297
298 fprintf(stderr, "%s: exiting normally!\n", getprogname());
299 return EXIT_SUCCESS;
300 }
301
main(int argc,char ** argv)302 int main(int argc, char** argv) {
303 #if defined(STATIC_CRASHER)
304 debuggerd_callbacks_t callbacks = {
305 .get_abort_message = []() {
306 static struct {
307 size_t size;
308 char msg[32];
309 } msg;
310
311 msg.size = strlen("dummy abort message");
312 memcpy(msg.msg, "dummy abort message", strlen("dummy abort message"));
313 return reinterpret_cast<abort_msg_t*>(&msg);
314 },
315 .post_dump = nullptr
316 };
317 debuggerd_init(&callbacks);
318 #endif
319
320 if (argc == 1) crash1();
321 else if (argc == 2) return do_action(argv[1]);
322
323 return usage();
324 }
325
326 };
327