1 /* $OpenBSD: getentropy_aix.c,v 1.7 2020/05/17 14:44:20 deraadt Exp $ */
2
3 /*
4 * Copyright (c) 2015 Michael Felt <aixtools@gmail.com>
5 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
6 * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
7 *
8 * Permission to use, copy, modify, and distribute this software for any
9 * purpose with or without fee is hereby granted, provided that the above
10 * copyright notice and this permission notice appear in all copies.
11 *
12 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
13 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
14 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
15 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
16 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
17 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
18 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
19 *
20 * Emulation of getentropy(2) as documented at:
21 * http://man.openbsd.org/getentropy.2
22 */
23 /*
24 * -lperfstat is needed for the psuedo entropy data
25 */
26
27 #include <sys/mman.h>
28 #include <sys/procfs.h>
29 #include <sys/protosw.h>
30 #include <sys/resource.h>
31 #include <sys/socket.h>
32 #include <sys/stat.h>
33 #include <sys/statvfs.h>
34 #include <sys/timers.h>
35 #include <errno.h>
36 #include <fcntl.h>
37 #include <signal.h>
38 #include <stdio.h>
39 #include <string.h>
40 #include <termios.h>
41
42 #include <openssl/sha.h>
43
44 #include <libperfstat.h>
45
46 #define REPEAT 5
47 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b))
48
49 #define HX(a, b) \
50 do { \
51 if ((a)) \
52 HD(errno); \
53 else \
54 HD(b); \
55 } while (0)
56
57 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
58 #define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
59 #define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
60
61 int getentropy(void *buf, size_t len);
62
63 static int getentropy_urandom(void *buf, size_t len, const char *path,
64 int devfscheck);
65 static int getentropy_fallback(void *buf, size_t len);
66
67 int
getentropy(void * buf,size_t len)68 getentropy(void *buf, size_t len)
69 {
70 int ret = -1;
71
72 if (len > 256) {
73 errno = EIO;
74 return (-1);
75 }
76
77 /*
78 * Try to get entropy with /dev/urandom
79 */
80 ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
81 if (ret != -1)
82 return (ret);
83
84 /*
85 * Entropy collection via /dev/urandom has failed.
86 *
87 * No other API exists for collecting entropy, and we have
88 * no failsafe way to get it on AIX that is not sensitive
89 * to resource exhaustion.
90 *
91 * We have very few options:
92 * - Even syslog_r is unsafe to call at this low level, so
93 * there is no way to alert the user or program.
94 * - Cannot call abort() because some systems have unsafe
95 * corefiles.
96 * - Could raise(SIGKILL) resulting in silent program termination.
97 * - Return EIO, to hint that arc4random's stir function
98 * should raise(SIGKILL)
99 * - Do the best under the circumstances....
100 *
101 * This code path exists to bring light to the issue that AIX
102 * does not provide a failsafe API for entropy collection.
103 *
104 * We hope this demonstrates that AIX should consider
105 * providing a new failsafe API which works in a chroot or
106 * when file descriptors are exhausted.
107 */
108 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
109 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
110 raise(SIGKILL);
111 #endif
112 ret = getentropy_fallback(buf, len);
113 if (ret != -1)
114 return (ret);
115
116 errno = EIO;
117 return (ret);
118 }
119
120 static int
getentropy_urandom(void * buf,size_t len,const char * path,int devfscheck)121 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
122 {
123 struct stat st;
124 size_t i;
125 int fd, flags;
126 int save_errno = errno;
127
128 start:
129
130 flags = O_RDONLY;
131 #ifdef O_NOFOLLOW
132 flags |= O_NOFOLLOW;
133 #endif
134 #ifdef O_CLOEXEC
135 flags |= O_CLOEXEC;
136 #endif
137 fd = open(path, flags, 0);
138 if (fd == -1) {
139 if (errno == EINTR)
140 goto start;
141 goto nodevrandom;
142 }
143 #ifndef O_CLOEXEC
144 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
145 #endif
146
147 /* Lightly verify that the device node looks sane */
148 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
149 close(fd);
150 goto nodevrandom;
151 }
152 for (i = 0; i < len; ) {
153 size_t wanted = len - i;
154 ssize_t ret = read(fd, (char *)buf + i, wanted);
155
156 if (ret == -1) {
157 if (errno == EAGAIN || errno == EINTR)
158 continue;
159 close(fd);
160 goto nodevrandom;
161 }
162 i += ret;
163 }
164 close(fd);
165 errno = save_errno;
166 return (0); /* satisfied */
167 nodevrandom:
168 errno = EIO;
169 return (-1);
170 }
171
172 static const int cl[] = {
173 CLOCK_REALTIME,
174 #ifdef CLOCK_MONOTONIC
175 CLOCK_MONOTONIC,
176 #endif
177 #ifdef CLOCK_MONOTONIC_RAW
178 CLOCK_MONOTONIC_RAW,
179 #endif
180 #ifdef CLOCK_TAI
181 CLOCK_TAI,
182 #endif
183 #ifdef CLOCK_VIRTUAL
184 CLOCK_VIRTUAL,
185 #endif
186 #ifdef CLOCK_UPTIME
187 CLOCK_UPTIME,
188 #endif
189 #ifdef CLOCK_PROCESS_CPUTIME_ID
190 CLOCK_PROCESS_CPUTIME_ID,
191 #endif
192 #ifdef CLOCK_THREAD_CPUTIME_ID
193 CLOCK_THREAD_CPUTIME_ID,
194 #endif
195 };
196
197 static int
getentropy_fallback(void * buf,size_t len)198 getentropy_fallback(void *buf, size_t len)
199 {
200 uint8_t results[SHA512_DIGEST_LENGTH];
201 int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
202 static int cnt;
203 struct timespec ts;
204 struct timeval tv;
205 perfstat_cpu_total_t cpustats;
206 #ifdef _AIX61
207 perfstat_cpu_total_wpar_t cpustats_wpar;
208 #endif
209 perfstat_partition_total_t lparstats;
210 perfstat_disk_total_t diskinfo;
211 perfstat_netinterface_total_t netinfo;
212 struct rusage ru;
213 sigset_t sigset;
214 struct stat st;
215 SHA512_CTX ctx;
216 static pid_t lastpid;
217 pid_t pid;
218 size_t i, ii, m;
219 char *p;
220
221 pid = getpid();
222 if (lastpid == pid) {
223 faster = 1;
224 repeat = 2;
225 } else {
226 faster = 0;
227 lastpid = pid;
228 repeat = REPEAT;
229 }
230 for (i = 0; i < len; ) {
231 int j;
232 SHA512_Init(&ctx);
233 for (j = 0; j < repeat; j++) {
234 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
235 if (e != -1) {
236 cnt += (int)tv.tv_sec;
237 cnt += (int)tv.tv_usec;
238 }
239
240 HX(perfstat_cpu_total(NULL, &cpustats,
241 sizeof(cpustats), 1) == -1, cpustats);
242
243 #ifdef _AIX61
244 HX(perfstat_cpu_total_wpar(NULL, &cpustats_wpar,
245 sizeof(cpustats_wpar), 1) == -1, cpustats_wpar);
246 #endif
247
248 HX(perfstat_partition_total(NULL, &lparstats,
249 sizeof(lparstats), 1) == -1, lparstats);
250
251 HX(perfstat_disk_total(NULL, &diskinfo,
252 sizeof(diskinfo), 1) == -1, diskinfo);
253
254 HX(perfstat_netinterface_total(NULL, &netinfo,
255 sizeof(netinfo), 1) == -1, netinfo);
256
257 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
258 HX(clock_gettime(cl[ii], &ts) == -1, ts);
259
260 HX((pid = getpid()) == -1, pid);
261 HX((pid = getsid(pid)) == -1, pid);
262 HX((pid = getppid()) == -1, pid);
263 HX((pid = getpgid(0)) == -1, pid);
264 HX((e = getpriority(0, 0)) == -1, e);
265
266 if (!faster) {
267 ts.tv_sec = 0;
268 ts.tv_nsec = 1;
269 (void) nanosleep(&ts, NULL);
270 }
271
272 HX(sigpending(&sigset) == -1, sigset);
273 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
274 sigset);
275
276 HF(getentropy); /* an addr in this library */
277 HF(printf); /* an addr in libc */
278 p = (char *)&p;
279 HD(p); /* an addr on stack */
280 p = (char *)&errno;
281 HD(p); /* the addr of errno */
282
283 if (i == 0) {
284 struct sockaddr_storage ss;
285 struct statvfs stvfs;
286 struct termios tios;
287 socklen_t ssl;
288 off_t off;
289
290 /*
291 * Prime-sized mappings encourage fragmentation;
292 * thus exposing some address entropy.
293 */
294 struct mm {
295 size_t npg;
296 void *p;
297 } mm[] = {
298 { 17, MAP_FAILED }, { 3, MAP_FAILED },
299 { 11, MAP_FAILED }, { 2, MAP_FAILED },
300 { 5, MAP_FAILED }, { 3, MAP_FAILED },
301 { 7, MAP_FAILED }, { 1, MAP_FAILED },
302 { 57, MAP_FAILED }, { 3, MAP_FAILED },
303 { 131, MAP_FAILED }, { 1, MAP_FAILED },
304 };
305
306 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
307 HX(mm[m].p = mmap(NULL,
308 mm[m].npg * pgs,
309 PROT_READ|PROT_WRITE,
310 MAP_PRIVATE|MAP_ANON, -1,
311 (off_t)0), mm[m].p);
312 if (mm[m].p != MAP_FAILED) {
313 size_t mo;
314
315 /* Touch some memory... */
316 p = mm[m].p;
317 mo = cnt %
318 (mm[m].npg * pgs - 1);
319 p[mo] = 1;
320 cnt += (int)((long)(mm[m].p)
321 / pgs);
322 }
323
324 /* Check cnts and times... */
325 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
326 ii++) {
327 HX((e = clock_gettime(cl[ii],
328 &ts)) == -1, ts);
329 if (e != -1)
330 cnt += (int)ts.tv_nsec;
331 }
332
333 HX((e = getrusage(RUSAGE_SELF,
334 &ru)) == -1, ru);
335 if (e != -1) {
336 cnt += (int)ru.ru_utime.tv_sec;
337 cnt += (int)ru.ru_utime.tv_usec;
338 }
339 }
340
341 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
342 if (mm[m].p != MAP_FAILED)
343 munmap(mm[m].p, mm[m].npg * pgs);
344 mm[m].p = MAP_FAILED;
345 }
346
347 HX(stat(".", &st) == -1, st);
348 HX(statvfs(".", &stvfs) == -1, stvfs);
349
350 HX(stat("/", &st) == -1, st);
351 HX(statvfs("/", &stvfs) == -1, stvfs);
352
353 HX((e = fstat(0, &st)) == -1, st);
354 if (e == -1) {
355 if (S_ISREG(st.st_mode) ||
356 S_ISFIFO(st.st_mode) ||
357 S_ISSOCK(st.st_mode)) {
358 HX(fstatvfs(0, &stvfs) == -1,
359 stvfs);
360 HX((off = lseek(0, (off_t)0,
361 SEEK_CUR)) < 0, off);
362 }
363 if (S_ISCHR(st.st_mode)) {
364 HX(tcgetattr(0, &tios) == -1,
365 tios);
366 } else if (S_ISSOCK(st.st_mode)) {
367 memset(&ss, 0, sizeof ss);
368 ssl = sizeof(ss);
369 HX(getpeername(0,
370 (void *)&ss, &ssl) == -1,
371 ss);
372 }
373 }
374
375 HX((e = getrusage(RUSAGE_CHILDREN,
376 &ru)) == -1, ru);
377 if (e != -1) {
378 cnt += (int)ru.ru_utime.tv_sec;
379 cnt += (int)ru.ru_utime.tv_usec;
380 }
381 } else {
382 /* Subsequent hashes absorb previous result */
383 HD(results);
384 }
385
386 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
387 if (e != -1) {
388 cnt += (int)tv.tv_sec;
389 cnt += (int)tv.tv_usec;
390 }
391
392 HD(cnt);
393 }
394 SHA512_Final(results, &ctx);
395 memcpy((char *)buf + i, results, MINIMUM(sizeof(results), len - i));
396 i += MINIMUM(sizeof(results), len - i);
397 }
398 explicit_bzero(&ctx, sizeof ctx);
399 explicit_bzero(results, sizeof results);
400 errno = save_errno;
401 return (0); /* satisfied */
402 }
403