1 #include <darwintest.h>
2
3 #include <errno.h>
4 #include <fcntl.h>
5 #include <signal.h>
6 #include <spawn.h>
7 #include <spawn_private.h>
8 #include <stdbool.h>
9 #include <stdint.h>
10 #include <stdio.h>
11 #include <stdlib.h>
12 #include <string.h>
13 #include <sys/spawn_internal.h>
14 #include <sys/sysctl.h>
15 #include <sys/syslimits.h>
16 #include <sys/reason.h>
17 #include <sysexits.h>
18 #include <unistd.h>
19 #include <signal.h>
20 #include <libproc.h>
21
22 #include <mach-o/dyld.h>
23 #include <mach-o/dyld_priv.h>
24 #include <dlfcn.h>
25
26 #define SHARED_CACHE_HELPER "get_shared_cache_address"
27 #define DO_RUSAGE_CHECK "check_rusage_flag"
28 #define DO_DUMMY "dummy"
29 #define ADDRESS_OUTPUT_SIZE 12L
30
31 #ifndef _POSIX_SPAWN_RESLIDE
32 #define _POSIX_SPAWN_RESLIDE 0x0800
33 #endif
34
35 #ifndef OS_REASON_FLAG_SHAREDREGION_FAULT
36 #define OS_REASON_FLAG_SHAREDREGION_FAULT 0x400
37 #endif
38
39 T_GLOBAL_META(
40 T_META_RADAR_COMPONENT_NAME("xnu"),
41 T_META_RADAR_COMPONENT_VERSION("VM"),
42 T_META_OWNER("eperla"),
43 T_META_RUN_CONCURRENTLY(true));
44
45 #if (__arm64e__) && (TARGET_OS_IOS || TARGET_OS_OSX)
46 static void *
get_current_slide_address(bool reslide)47 get_current_slide_address(bool reslide)
48 {
49 pid_t pid;
50 int pipefd[2];
51 posix_spawnattr_t attr;
52 posix_spawn_file_actions_t action;
53 uintptr_t addr;
54
55 T_ASSERT_POSIX_SUCCESS(posix_spawnattr_init(&attr), "posix_spawnattr_init");
56 /* spawn the helper requesting a reslide */
57 if (reslide) {
58 T_ASSERT_POSIX_SUCCESS(posix_spawnattr_setflags(&attr, _POSIX_SPAWN_RESLIDE), "posix_spawnattr_setflags");
59 }
60
61 T_ASSERT_POSIX_SUCCESS(pipe(pipefd), "pipe");
62 T_ASSERT_POSIX_ZERO(posix_spawn_file_actions_init(&action), "posix_spawn_fileactions_init");
63 T_ASSERT_POSIX_ZERO(posix_spawn_file_actions_addclose(&action, pipefd[0]), "posix_spawn_file_actions_addclose");
64 T_ASSERT_POSIX_ZERO(posix_spawn_file_actions_adddup2(&action, pipefd[1], 1), "posix_spawn_file_actions_addup2");
65 T_ASSERT_POSIX_ZERO(posix_spawn_file_actions_addclose(&action, pipefd[1]), "posix_spawn_file_actions_addclose");
66
67 char *argvs[3];
68 argvs[0] = SHARED_CACHE_HELPER;
69 argvs[1] = reslide ? DO_RUSAGE_CHECK : DO_DUMMY;
70 argvs[2] = NULL;
71 char *const envps[] = {NULL};
72
73 T_ASSERT_POSIX_ZERO(posix_spawn(&pid, SHARED_CACHE_HELPER, &action, &attr, argvs, envps), "helper posix_spawn");
74 T_ASSERT_POSIX_SUCCESS(close(pipefd[1]), "close child end of the pipe");
75
76 char buf[ADDRESS_OUTPUT_SIZE] = {0};
77
78 ssize_t read_bytes = 0;
79 do {
80 if (read_bytes == -1) {
81 T_LOG("reading off get_shared_cache_address got interrupted");
82 }
83 read_bytes = read(pipefd[0], buf, sizeof(buf));
84 } while (read_bytes == -1 && errno == EINTR);
85
86 T_ASSERT_EQ_LONG(ADDRESS_OUTPUT_SIZE, read_bytes, "read helper output");
87
88 int status = 0;
89 int waitpid_result = waitpid(pid, &status, 0);
90 T_ASSERT_POSIX_SUCCESS(waitpid_result, "waitpid");
91 T_ASSERT_EQ(waitpid_result, pid, "waitpid should return child we spawned");
92 T_ASSERT_EQ(WIFEXITED(status), 1, "child should have exited normally");
93 T_ASSERT_EQ(WEXITSTATUS(status), EX_OK, "child should have exited with success");
94
95 addr = strtoul(buf, NULL, 16);
96 T_ASSERT_GE_LONG(addr, 0L, "convert address to uintptr_t");
97
98 return (void *)addr;
99 }
100
101 /*
102 * build_faulting_shared_cache_address creates a pointer to an address that is
103 * within the shared_cache range but that is guaranteed to not be mapped.
104 */
105 static char *
build_faulting_shared_cache_address(bool tbi)106 build_faulting_shared_cache_address(bool tbi)
107 {
108 uintptr_t fault_address;
109
110 // Grab currently mapped shared cache location and size
111 size_t shared_cache_len = 0;
112 const void *shared_cache_location = _dyld_get_shared_cache_range(&shared_cache_len);
113 if (shared_cache_location == NULL || shared_cache_len == 0) {
114 return NULL;
115 }
116
117 // Locate a mach_header in the shared cache
118 Dl_info info;
119 if (dladdr((const void *)fork, &info) == 0) {
120 return NULL;
121 }
122
123 const struct mach_header *mh = info.dli_fbase;
124 uintptr_t slide = (uintptr_t)_dyld_get_image_slide(mh);
125
126 if (slide == 0) {
127 fault_address = (uintptr_t)shared_cache_location + shared_cache_len + PAGE_SIZE;
128 } else {
129 fault_address = (uintptr_t)shared_cache_location - PAGE_SIZE;
130 }
131
132 if (tbi) {
133 fault_address |= 0x2000000000000000;
134 }
135
136 return (char *)fault_address;
137 }
138
139 static void
induce_crash(volatile char * ptr)140 induce_crash(volatile char *ptr)
141 {
142 pid_t child = fork();
143 T_ASSERT_POSIX_SUCCESS(child, "fork");
144
145 if (child == 0) {
146 ptr[1];
147 } else {
148 sleep(1);
149 struct proc_exitreasonbasicinfo exit_reason = {0};
150 T_ASSERT_POSIX_SUCCESS(proc_pidinfo(child, PROC_PIDEXITREASONBASICINFO, 1, &exit_reason, sizeof(exit_reason)), "basic exit reason");
151
152 int status = 0;
153 int waitpid_result;
154 do {
155 waitpid_result = waitpid(child, &status, 0);
156 } while (waitpid_result < 0 && errno == EINTR);
157 T_QUIET; T_ASSERT_POSIX_SUCCESS(waitpid_result, "waitpid");
158 T_ASSERT_EQ(waitpid_result, child, "waitpid should return forked child");
159 T_ASSERT_EQ(exit_reason.beri_namespace, OS_REASON_SIGNAL, "child should have exited with a signal");
160
161 if (ptr) {
162 T_ASSERT_EQ_ULLONG(exit_reason.beri_code, (unsigned long long)SIGSEGV, "child should have received SIGSEGV");
163 T_ASSERT_NE((int)(exit_reason.beri_flags & OS_REASON_FLAG_SHAREDREGION_FAULT), 0, "should detect shared cache fault");
164 } else {
165 T_ASSERT_EQ((int)(exit_reason.beri_flags & OS_REASON_FLAG_SHAREDREGION_FAULT), 0, "should not detect shared cache fault");
166 }
167 }
168 }
169
170 static int saved_status;
171 static void
cleanup_sysctl(void)172 cleanup_sysctl(void)
173 {
174 int ret;
175
176 if (saved_status == 0) {
177 ret = sysctlbyname("vm.vm_shared_region_reslide_aslr", NULL, NULL, &saved_status, sizeof(saved_status));
178 T_QUIET; T_EXPECT_POSIX_SUCCESS(ret, "set shared region resliding back off");
179 }
180 }
181 #endif /* arm64e && (TARGET_OS_IOS || TARGET_OS_OSX) */
182
183 T_DECL(reslide_sharedcache, "crash induced reslide of the shared cache",
184 T_META_CHECK_LEAKS(false), T_META_IGNORECRASHES(".*shared_cache_reslide_test.*"),
185 T_META_ASROOT(true))
186 {
187 #if (__arm64e__) && (TARGET_OS_IOS || TARGET_OS_OSX)
188 void *system_address;
189 void *reslide_address;
190 void *confirm_address;
191 char *ptr;
192 int on = 1;
193 size_t size = sizeof(saved_status);
194
195 /* Force resliding on */
196 T_ASSERT_POSIX_SUCCESS(sysctlbyname("vm.vm_shared_region_reslide_aslr", &saved_status, &size, &on, sizeof(on)), "force enable reslide");
197 T_ATEND(cleanup_sysctl);
198
199 system_address = get_current_slide_address(false);
200 confirm_address = get_current_slide_address(false);
201 T_ASSERT_EQ_PTR(system_address, confirm_address, "system and current addresses should not diverge %p %p", system_address, confirm_address);
202
203 reslide_address = get_current_slide_address(true);
204 confirm_address = get_current_slide_address(true);
205 T_ASSERT_NE_PTR(system_address, reslide_address, "system and reslide addresses should diverge %p %p", system_address, reslide_address);
206 T_ASSERT_EQ_PTR(reslide_address, confirm_address, "reslide and another reslide (no crash) shouldn't diverge %p %p", reslide_address, confirm_address);
207
208 /* Crash into the shared cache area */
209 ptr = build_faulting_shared_cache_address(false);
210 T_ASSERT_NOTNULL(ptr, "faulting on %p in the shared region", (void *)ptr);
211 induce_crash(ptr);
212 reslide_address = get_current_slide_address(true);
213 T_ASSERT_NE_PTR(system_address, reslide_address, "system and reslide should diverge (after crash) %p %p", system_address, reslide_address);
214 T_ASSERT_NE_PTR(confirm_address, reslide_address, "reslide and another reslide should diverge (after crash) %p %p", confirm_address, reslide_address);
215
216 confirm_address = get_current_slide_address(true);
217 T_ASSERT_EQ_PTR(reslide_address, confirm_address, "reslide and another reslide shouldn't diverge (no crash) %p %p", reslide_address, confirm_address);
218
219 /* Crash somewhere else */
220 ptr = NULL;
221 induce_crash(ptr);
222 confirm_address = get_current_slide_address(true);
223 T_ASSERT_EQ_PTR(reslide_address, confirm_address, "reslide and another reslide after a non-tracked crash shouldn't diverge %p %p", reslide_address, confirm_address);
224
225 /* Ensure we still get the system address */
226 confirm_address = get_current_slide_address(false);
227 T_ASSERT_EQ_PTR(system_address, confirm_address, "system address and new process without resliding shouldn't diverge %p %p", system_address, confirm_address);
228
229 /* Ensure we detect a crash into the shared area with a TBI tagged address */
230 ptr = build_faulting_shared_cache_address(true);
231 T_ASSERT_NOTNULL(ptr, "faulting on %p in the shared region", (void *)ptr);
232 confirm_address = get_current_slide_address(true);
233 induce_crash(ptr);
234 reslide_address = get_current_slide_address(true);
235 T_ASSERT_NE_PTR(system_address, reslide_address, "system and reslide should diverge (after crash, TBI test) %p %p", system_address, reslide_address);
236 T_ASSERT_NE_PTR(confirm_address, reslide_address, "reslide and another reslide should diverge (after crash, TBI test) %p %p", confirm_address, reslide_address);
237 #else /* __arm64e__ && (TARGET_OS_IOS || TARGET_OS_OSX) */
238 T_SKIP("shared cache reslide is currently only supported on arm64e iPhones and Apple Silicon Macs");
239 #endif /* __arm64e__ && (TARGET_OS_IOS || TARGET_OS_OSX) */
240 }
241