1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2020 ARM Limited
3
4 #define _GNU_SOURCE
5
6 #include <sys/auxv.h>
7 #include <sys/types.h>
8 #include <sys/wait.h>
9 #include <signal.h>
10 #include <setjmp.h>
11 #include <sched.h>
12
13 #include "../../kselftest_harness.h"
14 #include "helper.h"
15
16 #define PAC_COLLISION_ATTEMPTS 10
17 /*
18 * The kernel sets TBID by default. So bits 55 and above should remain
19 * untouched no matter what.
20 * The VA space size is 48 bits. Bigger is opt-in.
21 */
22 #define PAC_MASK (~0xff80ffffffffffff)
23 #define ARBITRARY_VALUE (0x1234)
24 #define ASSERT_PAUTH_ENABLED() \
25 do { \
26 unsigned long hwcaps = getauxval(AT_HWCAP); \
27 /* data key instructions are not in NOP space. This prevents a SIGILL */ \
28 if (!(hwcaps & HWCAP_PACA)) \
29 SKIP(return, "PAUTH not enabled"); \
30 } while (0)
31 #define ASSERT_GENERIC_PAUTH_ENABLED() \
32 do { \
33 unsigned long hwcaps = getauxval(AT_HWCAP); \
34 /* generic key instructions are not in NOP space. This prevents a SIGILL */ \
35 if (!(hwcaps & HWCAP_PACG)) \
36 SKIP(return, "Generic PAUTH not enabled"); \
37 } while (0)
38
sign_specific(struct signatures * sign,size_t val)39 void sign_specific(struct signatures *sign, size_t val)
40 {
41 sign->keyia = keyia_sign(val);
42 sign->keyib = keyib_sign(val);
43 sign->keyda = keyda_sign(val);
44 sign->keydb = keydb_sign(val);
45 }
46
sign_all(struct signatures * sign,size_t val)47 void sign_all(struct signatures *sign, size_t val)
48 {
49 sign->keyia = keyia_sign(val);
50 sign->keyib = keyib_sign(val);
51 sign->keyda = keyda_sign(val);
52 sign->keydb = keydb_sign(val);
53 sign->keyg = keyg_sign(val);
54 }
55
n_same(struct signatures * old,struct signatures * new,int nkeys)56 int n_same(struct signatures *old, struct signatures *new, int nkeys)
57 {
58 int res = 0;
59
60 res += old->keyia == new->keyia;
61 res += old->keyib == new->keyib;
62 res += old->keyda == new->keyda;
63 res += old->keydb == new->keydb;
64 if (nkeys == NKEYS)
65 res += old->keyg == new->keyg;
66
67 return res;
68 }
69
n_same_single_set(struct signatures * sign,int nkeys)70 int n_same_single_set(struct signatures *sign, int nkeys)
71 {
72 size_t vals[nkeys];
73 int same = 0;
74
75 vals[0] = sign->keyia & PAC_MASK;
76 vals[1] = sign->keyib & PAC_MASK;
77 vals[2] = sign->keyda & PAC_MASK;
78 vals[3] = sign->keydb & PAC_MASK;
79
80 if (nkeys >= 4)
81 vals[4] = sign->keyg & PAC_MASK;
82
83 for (int i = 0; i < nkeys - 1; i++) {
84 for (int j = i + 1; j < nkeys; j++) {
85 if (vals[i] == vals[j])
86 same += 1;
87 }
88 }
89 return same;
90 }
91
exec_sign_all(struct signatures * signed_vals,size_t val)92 int exec_sign_all(struct signatures *signed_vals, size_t val)
93 {
94 int new_stdin[2];
95 int new_stdout[2];
96 int status;
97 int i;
98 ssize_t ret;
99 pid_t pid;
100 cpu_set_t mask;
101
102 ret = pipe(new_stdin);
103 if (ret == -1) {
104 perror("pipe returned error");
105 return -1;
106 }
107
108 ret = pipe(new_stdout);
109 if (ret == -1) {
110 perror("pipe returned error");
111 return -1;
112 }
113
114 /*
115 * pin this process and all its children to a single CPU, so it can also
116 * guarantee a context switch with its child
117 */
118 sched_getaffinity(0, sizeof(mask), &mask);
119
120 for (i = 0; i < sizeof(cpu_set_t); i++)
121 if (CPU_ISSET(i, &mask))
122 break;
123
124 CPU_ZERO(&mask);
125 CPU_SET(i, &mask);
126 sched_setaffinity(0, sizeof(mask), &mask);
127
128 pid = fork();
129 // child
130 if (pid == 0) {
131 dup2(new_stdin[0], STDIN_FILENO);
132 if (ret == -1) {
133 perror("dup2 returned error");
134 exit(1);
135 }
136
137 dup2(new_stdout[1], STDOUT_FILENO);
138 if (ret == -1) {
139 perror("dup2 returned error");
140 exit(1);
141 }
142
143 close(new_stdin[0]);
144 close(new_stdin[1]);
145 close(new_stdout[0]);
146 close(new_stdout[1]);
147
148 ret = execl("exec_target", "exec_target", (char *)NULL);
149 if (ret == -1) {
150 perror("exec returned error");
151 exit(1);
152 }
153 }
154
155 close(new_stdin[0]);
156 close(new_stdout[1]);
157
158 ret = write(new_stdin[1], &val, sizeof(size_t));
159 if (ret == -1) {
160 perror("write returned error");
161 return -1;
162 }
163
164 /*
165 * wait for the worker to finish, so that read() reads all data
166 * will also context switch with worker so that this function can be used
167 * for context switch tests
168 */
169 waitpid(pid, &status, 0);
170 if (WIFEXITED(status) == 0) {
171 fprintf(stderr, "worker exited unexpectedly\n");
172 return -1;
173 }
174 if (WEXITSTATUS(status) != 0) {
175 fprintf(stderr, "worker exited with error\n");
176 return -1;
177 }
178
179 ret = read(new_stdout[0], signed_vals, sizeof(struct signatures));
180 if (ret == -1) {
181 perror("read returned error");
182 return -1;
183 }
184
185 return 0;
186 }
187
188 sigjmp_buf jmpbuf;
pac_signal_handler(int signum,siginfo_t * si,void * uc)189 void pac_signal_handler(int signum, siginfo_t *si, void *uc)
190 {
191 if (signum == SIGSEGV || signum == SIGILL)
192 siglongjmp(jmpbuf, 1);
193 }
194
195 /* check that a corrupted PAC results in SIGSEGV or SIGILL */
TEST(corrupt_pac)196 TEST(corrupt_pac)
197 {
198 struct sigaction sa;
199
200 ASSERT_PAUTH_ENABLED();
201 if (sigsetjmp(jmpbuf, 1) == 0) {
202 sa.sa_sigaction = pac_signal_handler;
203 sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
204 sigemptyset(&sa.sa_mask);
205
206 sigaction(SIGSEGV, &sa, NULL);
207 sigaction(SIGILL, &sa, NULL);
208
209 pac_corruptor();
210 ASSERT_TRUE(0) TH_LOG("SIGSEGV/SIGILL signal did not occur");
211 }
212 }
213
214 /*
215 * There are no separate pac* and aut* controls so checking only the pac*
216 * instructions is sufficient
217 */
TEST(pac_instructions_not_nop)218 TEST(pac_instructions_not_nop)
219 {
220 size_t keyia = 0;
221 size_t keyib = 0;
222 size_t keyda = 0;
223 size_t keydb = 0;
224
225 ASSERT_PAUTH_ENABLED();
226
227 for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
228 keyia |= keyia_sign(i) & PAC_MASK;
229 keyib |= keyib_sign(i) & PAC_MASK;
230 keyda |= keyda_sign(i) & PAC_MASK;
231 keydb |= keydb_sign(i) & PAC_MASK;
232 }
233
234 ASSERT_NE(0, keyia) TH_LOG("keyia instructions did nothing");
235 ASSERT_NE(0, keyib) TH_LOG("keyib instructions did nothing");
236 ASSERT_NE(0, keyda) TH_LOG("keyda instructions did nothing");
237 ASSERT_NE(0, keydb) TH_LOG("keydb instructions did nothing");
238 }
239
TEST(pac_instructions_not_nop_generic)240 TEST(pac_instructions_not_nop_generic)
241 {
242 size_t keyg = 0;
243
244 ASSERT_GENERIC_PAUTH_ENABLED();
245
246 for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++)
247 keyg |= keyg_sign(i) & PAC_MASK;
248
249 ASSERT_NE(0, keyg) TH_LOG("keyg instructions did nothing");
250 }
251
TEST(single_thread_different_keys)252 TEST(single_thread_different_keys)
253 {
254 int same = 10;
255 int nkeys = NKEYS;
256 int tmp;
257 struct signatures signed_vals;
258 unsigned long hwcaps = getauxval(AT_HWCAP);
259
260 /* generic and data key instructions are not in NOP space. This prevents a SIGILL */
261 ASSERT_PAUTH_ENABLED();
262 if (!(hwcaps & HWCAP_PACG)) {
263 TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
264 nkeys = NKEYS - 1;
265 }
266
267 /*
268 * In Linux the PAC field can be up to 7 bits wide. Even if keys are
269 * different, there is about 5% chance for PACs to collide with
270 * different addresses. This chance rapidly increases with fewer bits
271 * allocated for the PAC (e.g. wider address). A comparison of the keys
272 * directly will be more reliable.
273 * All signed values need to be different at least once out of n
274 * attempts to be certain that the keys are different
275 */
276 for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
277 if (nkeys == NKEYS)
278 sign_all(&signed_vals, i);
279 else
280 sign_specific(&signed_vals, i);
281
282 tmp = n_same_single_set(&signed_vals, nkeys);
283 if (tmp < same)
284 same = tmp;
285 }
286
287 ASSERT_EQ(0, same) TH_LOG("%d keys clashed every time", same);
288 }
289
290 /*
291 * fork() does not change keys. Only exec() does so call a worker program.
292 * Its only job is to sign a value and report back the resutls
293 */
TEST(exec_changed_keys)294 TEST(exec_changed_keys)
295 {
296 struct signatures new_keys;
297 struct signatures old_keys;
298 int ret;
299 int same = 10;
300 int nkeys = NKEYS;
301 unsigned long hwcaps = getauxval(AT_HWCAP);
302
303 /* generic and data key instructions are not in NOP space. This prevents a SIGILL */
304 ASSERT_PAUTH_ENABLED();
305 if (!(hwcaps & HWCAP_PACG)) {
306 TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
307 nkeys = NKEYS - 1;
308 }
309
310 for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
311 ret = exec_sign_all(&new_keys, i);
312 ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
313
314 if (nkeys == NKEYS)
315 sign_all(&old_keys, i);
316 else
317 sign_specific(&old_keys, i);
318
319 ret = n_same(&old_keys, &new_keys, nkeys);
320 if (ret < same)
321 same = ret;
322 }
323
324 ASSERT_EQ(0, same) TH_LOG("exec() did not change %d keys", same);
325 }
326
TEST(context_switch_keep_keys)327 TEST(context_switch_keep_keys)
328 {
329 int ret;
330 struct signatures trash;
331 struct signatures before;
332 struct signatures after;
333
334 ASSERT_PAUTH_ENABLED();
335
336 sign_specific(&before, ARBITRARY_VALUE);
337
338 /* will context switch with a process with different keys at least once */
339 ret = exec_sign_all(&trash, ARBITRARY_VALUE);
340 ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
341
342 sign_specific(&after, ARBITRARY_VALUE);
343
344 ASSERT_EQ(before.keyia, after.keyia) TH_LOG("keyia changed after context switching");
345 ASSERT_EQ(before.keyib, after.keyib) TH_LOG("keyib changed after context switching");
346 ASSERT_EQ(before.keyda, after.keyda) TH_LOG("keyda changed after context switching");
347 ASSERT_EQ(before.keydb, after.keydb) TH_LOG("keydb changed after context switching");
348 }
349
TEST(context_switch_keep_keys_generic)350 TEST(context_switch_keep_keys_generic)
351 {
352 int ret;
353 struct signatures trash;
354 size_t before;
355 size_t after;
356
357 ASSERT_GENERIC_PAUTH_ENABLED();
358
359 before = keyg_sign(ARBITRARY_VALUE);
360
361 /* will context switch with a process with different keys at least once */
362 ret = exec_sign_all(&trash, ARBITRARY_VALUE);
363 ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
364
365 after = keyg_sign(ARBITRARY_VALUE);
366
367 ASSERT_EQ(before, after) TH_LOG("keyg changed after context switching");
368 }
369
370 TEST_HARNESS_MAIN
371