Commit | Line | Data |
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d03ab969 | 1 | /* -*-c-*- |
d03ab969 | 2 | * |
099355bc | 3 | * Acquisition of environmental noise (Unix-specific) |
d03ab969 | 4 | * |
5 | * (c) 1998 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
d03ab969 | 9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
45c0fd36 | 16 | * |
d03ab969 | 17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
45c0fd36 | 21 | * |
d03ab969 | 22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
d03ab969 | 28 | /*----- Header files ------------------------------------------------------*/ |
29 | ||
178220b3 | 30 | #include "config.h" |
d03ab969 | 31 | |
baf5b59c | 32 | #include <errno.h> |
25f654a7 | 33 | #include <setjmp.h> |
93f563bf | 34 | #include <signal.h> |
d03ab969 | 35 | #include <stdio.h> |
df40b082 | 36 | #include <stdlib.h> |
d03ab969 | 37 | #include <string.h> |
8039afaf | 38 | #include <time.h> |
d03ab969 | 39 | |
40 | #include <sys/types.h> | |
41 | #include <sys/time.h> | |
42 | #include <sys/wait.h> | |
43 | ||
44 | #include <fcntl.h> | |
45 | #include <unistd.h> | |
46 | ||
47 | #ifdef HAVE_SETGROUPS | |
48 | # include <grp.h> | |
49 | #endif | |
50 | ||
baf5b59c MW |
51 | #if defined(HAVE_LINUX_RANDOM_H) |
52 | # include <linux/random.h> | |
53 | # include <sys/syscall.h> | |
54 | #endif | |
55 | ||
d03ab969 | 56 | #include <mLib/bits.h> |
cbc993ef | 57 | #include <mLib/mdup.h> |
6b837b22 | 58 | #include <mLib/sel.h> |
d03ab969 | 59 | #include <mLib/tv.h> |
60 | ||
61 | #include "noise.h" | |
62 | #include "paranoia.h" | |
63 | #include "rand.h" | |
64 | ||
65 | /*----- Magical numbers ---------------------------------------------------*/ | |
66 | ||
67 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ | |
70221324 | 68 | |
8039afaf MW |
69 | #if HAVE_CLOCK_GETTIME && _POSIX_TIMERS > 0 |
70 | # define TIMESTRUCT timespec | |
71 | # define tv_SEC tv_sec | |
72 | # define tv_FRAC tv_nsec | |
73 | # define TIMERES 1000000000 | |
74 | # if _POSIX_MONOTONIC_CLOCK > 0 | |
75 | # define GETTIME(tv) (clock_gettime(CLOCK_MONOTONIC, (tv))) | |
76 | # else | |
77 | # define GETTIME(tv) (clock_gettime(CLOCK_REALTIME, (tv))) | |
78 | # endif | |
79 | # define TOTIMEVAL(tv, xx) \ | |
80 | ((tv)->tv_sec = (xx)->tv_sec, \ | |
81 | (tv)->tv_usec = ((xx)->tv_nsec + 500)/1000) | |
82 | #else | |
70221324 MW |
83 | # define TIMESTRUCT timeval |
84 | # define tv_SEC tv_sec | |
85 | # define tv_FRAC tv_usec | |
86 | # define TIMERES 1000000 | |
87 | # define GETTIME(tv) (gettimeofday((tv), 0)) | |
88 | # define TOTIMEVAL(tv, xx) (*(tv) = *(xx)) | |
8039afaf | 89 | #endif |
d03ab969 | 90 | |
91 | /*----- Noise source definition -------------------------------------------*/ | |
92 | ||
4e66da02 | 93 | const rand_source noise_source = { noise_acquire, noise_timer }; |
d03ab969 | 94 | |
95 | /*----- Static variables --------------------------------------------------*/ | |
96 | ||
97 | /* --- Timer differences --- */ | |
98 | ||
99 | static unsigned long noise_last; /* Last time recorded */ | |
100 | static unsigned long noise_diff; /* Last first order difference */ | |
101 | ||
102 | /* --- Setuid program handling --- */ | |
103 | ||
178220b3 | 104 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
105 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ | |
d03ab969 | 106 | |
107 | /*----- Main code ---------------------------------------------------------*/ | |
108 | ||
109 | /* --- @bitcount@ --- * | |
110 | * | |
111 | * Arguments: @unsigned long x@ = a word containing bits | |
112 | * | |
113 | * Returns: The number of bits set in the word. | |
114 | */ | |
115 | ||
116 | static int bitcount(unsigned long x) | |
117 | { | |
9332366e MW |
118 | static const char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, |
119 | 1, 2, 2, 3, 2, 3, 3, 4 }; | |
d03ab969 | 120 | int count = 0; |
121 | while (x) { | |
122 | count += ctab[x & 0xfu]; | |
123 | x >>= 4; | |
124 | } | |
125 | return (count); | |
126 | } | |
127 | ||
128 | /* --- @timer@ --- * | |
129 | * | |
130 | * Arguments: @rand_pool *r@ = pointer to randomness pool | |
70221324 | 131 | * @const struct TIMESTRUCT *tv@ = pointer to time block |
d03ab969 | 132 | * |
25f654a7 | 133 | * Returns: Nonzero if some randomness was contributed. |
d03ab969 | 134 | * |
135 | * Use: Low-level timer contributor. | |
136 | */ | |
137 | ||
70221324 | 138 | static int timer(rand_pool *r, const struct TIMESTRUCT *tv) |
d03ab969 | 139 | { |
140 | unsigned long x, d, dd; | |
141 | int de, dde; | |
142 | int ret; | |
45c0fd36 | 143 | |
70221324 | 144 | x = tv->tv_FRAC + TIMERES*tv->tv_SEC; |
d03ab969 | 145 | d = x ^ noise_last; |
146 | dd = d ^ noise_diff; | |
fc8f52d7 | 147 | noise_last = x; |
d03ab969 | 148 | noise_diff = d; |
149 | de = bitcount(d); | |
150 | dde = bitcount(dd); | |
151 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); | |
152 | ret = (de || dde); | |
153 | BURN(tv); x = d = dd = de = dde = 0; | |
154 | return (ret); | |
155 | } | |
156 | ||
157 | /* --- @noise_timer@ --- * | |
158 | * | |
159 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
160 | * | |
161 | * Returns: Nonzero if some randomness was contributed. | |
162 | * | |
163 | * Use: Contributes the current time to the randomness pool. | |
164 | * A guess at the number of useful bits contributed is made, | |
165 | * based on first and second order bit differences. This isn't | |
166 | * ever-so reliable, but it's better than nothing. | |
167 | */ | |
168 | ||
169 | int noise_timer(rand_pool *r) | |
170 | { | |
70221324 MW |
171 | struct TIMESTRUCT tv; |
172 | GETTIME(&tv); return (timer(r, &tv)); | |
d03ab969 | 173 | } |
174 | ||
175 | /* --- @noise_devrandom@ --- * | |
176 | * | |
177 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
178 | * | |
179 | * Returns: Nonzero if some randomness was contributed. | |
180 | * | |
181 | * Use: Attempts to obtain some randomness from the system entropy | |
182 | * pool. All bits from the device are assumed to be good. | |
183 | */ | |
184 | ||
185 | int noise_devrandom(rand_pool *r) | |
186 | { | |
c22fa0c9 | 187 | int fd = -1; |
d03ab969 | 188 | octet buf[RAND_POOLSZ]; |
189 | ssize_t len; | |
57354275 | 190 | size_t n = 0; |
d03ab969 | 191 | int ret = 0; |
ecc296eb MW |
192 | #ifdef __linux__ |
193 | fd_set infd; | |
194 | struct timeval tv = { 0, 0 }; | |
195 | #endif | |
6d4416cc MW |
196 | #ifdef HAVE_GETENTROPY |
197 | size_t nn; | |
198 | #endif | |
ecc296eb | 199 | |
baf5b59c MW |
200 | #if defined(HAVE_LINUX_RANDOM_H) && \ |
201 | defined(GRND_NONBLOCK) && \ | |
202 | defined(SYS_getrandom) | |
203 | /* --- Use the new shinies if available --- */ | |
204 | ||
205 | while (n < sizeof(buf)) { | |
206 | if ((len = syscall(SYS_getrandom, buf + n, sizeof(buf) - n, | |
207 | GRND_NONBLOCK)) <= 0) { | |
208 | if (errno == ENOSYS) break; | |
209 | else goto done; | |
210 | } | |
211 | n += len; | |
212 | } | |
213 | if (n == sizeof(buf)) goto win; | |
214 | #endif | |
215 | ||
6d4416cc MW |
216 | #ifdef HAVE_GETENTROPY |
217 | /* --- OpenBSD-flavoured shinies --- */ | |
218 | ||
219 | while (n < sizeof(buf)) { | |
220 | nn = sizeof(buf) - nn; | |
221 | if (nn > 256) nn = 256; | |
222 | if (getentropy(buf + n, nn)) break; | |
223 | n += nn; | |
224 | } | |
225 | if (n == sizeof(buf)) goto win; | |
226 | #endif | |
227 | ||
ecc296eb MW |
228 | #ifdef __linux__ |
229 | /* --- Don't take from `/dev/urandom' if `/dev/random' would block --- */ | |
230 | ||
231 | if ((fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) < 0) goto done; | |
232 | FD_ZERO(&infd); | |
233 | FD_SET(fd, &infd); | |
234 | if (select(fd + 1, &infd, 0, 0, &tv) < 0 || !FD_ISSET(fd, &infd)) | |
235 | goto done; | |
236 | close(fd); fd = -1; | |
237 | #endif | |
d03ab969 | 238 | |
239 | /* --- Be nice to other clients of the random device --- * | |
240 | * | |
241 | * Attempt to open the device nonblockingly. If that works, take up to | |
242 | * one bufferful and then close again. If there's no data to be read, | |
243 | * then that's tough and we go away again, on the grounds that the device | |
244 | * needs to get some more entropy from somewhere. | |
245 | */ | |
246 | ||
c22fa0c9 MW |
247 | if (fd >= 0 || |
248 | (fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || | |
25f654a7 | 249 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
250 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { | |
57354275 MW |
251 | while (n < sizeof(buf)) { |
252 | if ((len = read(fd, buf + n, sizeof(buf) - n)) <= 0) break; | |
253 | n += len; | |
d03ab969 | 254 | } |
c22fa0c9 | 255 | if (n == sizeof(buf)) goto win; |
d03ab969 | 256 | } |
c22fa0c9 MW |
257 | goto done; |
258 | ||
259 | win: | |
260 | ret = 1; | |
261 | done: | |
262 | if (fd >= 0) close(fd); | |
263 | rand_add(r, buf, n, 8*n); | |
264 | BURN(buf); | |
d03ab969 | 265 | noise_timer(r); |
266 | return (ret); | |
267 | } | |
268 | ||
269 | /* --- @noise_setid@ --- * | |
270 | * | |
271 | * Arguments: @uid_t uid@ = uid to set | |
272 | * @gid_t gid@ = gid to set | |
273 | * | |
274 | * Returns: --- | |
275 | * | |
276 | * Use: Sets the user and group ids to be used by @noise_filter@ | |
277 | * when running child processes. This is useful to avoid | |
278 | * giving shell commands (even carefully written ones) undue | |
099355bc | 279 | * privileges. This interface is Unix-specific |
d03ab969 | 280 | */ |
281 | ||
282 | void noise_setid(uid_t uid, gid_t gid) | |
283 | { | |
284 | noise_uid = uid; | |
285 | noise_gid = gid; | |
286 | } | |
287 | ||
288 | /* --- @noise_filter@ --- * | |
289 | * | |
290 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
291 | * @int good@ = number of good bits per 1024 bits | |
292 | * @const char *c@ = shell command to run | |
293 | * | |
294 | * Returns: Nonzero if some randomness was contributed. | |
295 | * | |
296 | * Use: Attempts to execute a shell command, and dump it into the | |
297 | * randomness pool. A very rough estimate of the number of | |
298 | * good bits is made, based on the size of the command's output. | |
299 | * This function calls @waitpid@, so be careful. Before execing | |
300 | * the command, the process uid and gid are set to the values | |
301 | * given to @noise_setid@, and an attempt is made to reset the | |
302 | * list of supplementary groups. The environment passed to | |
303 | * the command has been severly lobotimized. If the command | |
304 | * fails to complete within a short time period, it is killed. | |
305 | * Paranoid use of close-on-exec flags for file descriptors is | |
306 | * recommended. | |
099355bc | 307 | * |
308 | * This interface is Unix-specific. | |
d03ab969 | 309 | */ |
310 | ||
6b837b22 MW |
311 | struct noisekid { |
312 | rand_pool *r; | |
313 | int good; | |
314 | char buf[4096]; | |
315 | int donep; | |
316 | int ret; | |
317 | }; | |
318 | ||
319 | static void kid_read(int fd, unsigned mode, void *p) | |
320 | { | |
321 | struct noisekid *nk = p; | |
322 | ssize_t sz; | |
323 | int goodbits; | |
324 | ||
325 | noise_timer(nk->r); | |
326 | if ((sz = read(fd, nk->buf, sizeof(nk->buf))) <= 0) | |
327 | nk->donep = 1; | |
328 | else { | |
329 | goodbits = (sz * nk->good) / 128; | |
330 | rand_add(nk->r, nk->buf, sz, goodbits); | |
331 | nk->ret = 1; | |
332 | } | |
333 | } | |
334 | ||
335 | static void kid_dead(struct timeval *tv, void *p) | |
336 | { struct noisekid *nk = p; nk->donep = 1; } | |
337 | ||
d03ab969 | 338 | int noise_filter(rand_pool *r, int good, const char *c) |
339 | { | |
d03ab969 | 340 | pid_t kid; |
341 | int fd[2]; | |
342 | struct timeval dead; | |
70221324 | 343 | struct TIMESTRUCT now; |
d03ab969 | 344 | int ret = 0; |
6b837b22 MW |
345 | struct noisekid nk = { 0 }; |
346 | sel_state sel; | |
347 | sel_file sf; | |
348 | sel_timer st; | |
d03ab969 | 349 | const char *env[] = { |
350 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", | |
351 | 0 | |
352 | }; | |
353 | ||
354 | /* --- Remember when this business started --- */ | |
355 | ||
70221324 MW |
356 | GETTIME(&now); timer(r, &now); |
357 | TOTIMEVAL(&dead, &now); | |
d03ab969 | 358 | |
359 | /* --- Create a pipe --- */ | |
360 | ||
361 | if (pipe(fd)) | |
362 | return (ret); | |
363 | ||
364 | /* --- Fork a child off --- */ | |
365 | ||
028b34c6 | 366 | fflush(0); |
d03ab969 | 367 | kid = fork(); |
368 | if (kid < 0) { | |
369 | close(fd[0]); | |
370 | close(fd[1]); | |
371 | return (ret); | |
372 | } | |
373 | ||
374 | /* --- Handle the child end of the deal --- */ | |
375 | ||
d03ab969 | 376 | if (kid == 0) { |
cbc993ef MW |
377 | mdup_fd mfd[3]; |
378 | int f, i = 0; | |
d03ab969 | 379 | |
380 | /* --- Set the pipe as standard output, close standard input --- */ | |
381 | ||
cbc993ef MW |
382 | if ((f = open("/dev/null", O_RDONLY)) < 0) _exit(127); |
383 | mfd[i].cur = f; mfd[i].want = 0; i++; | |
384 | mfd[i].cur = fd[1]; mfd[i].want = 1; i++; | |
385 | mfd[i].cur = f; mfd[i].want = 2; i++; | |
386 | if (mdup(mfd, i)) _exit(127); | |
d03ab969 | 387 | |
388 | /* --- Play games with uids --- */ | |
389 | ||
390 | if (noise_gid != NOISE_NOSETGID) { | |
391 | setgid(noise_gid); | |
392 | setegid(noise_gid); | |
393 | #ifdef HAVE_SETGROUPS | |
394 | setgroups(1, &noise_gid); | |
395 | #endif | |
396 | } | |
397 | ||
398 | if (noise_uid != NOISE_NOSETUID) { | |
399 | setuid(noise_uid); | |
400 | seteuid(noise_uid); | |
401 | } | |
402 | ||
403 | /* --- Start the process up --- */ | |
404 | ||
65e14862 | 405 | execle("/bin/sh", "sh", "-c", c, (char *)0, env); |
d03ab969 | 406 | _exit(127); |
407 | } | |
408 | ||
409 | /* --- Sort out my end of the deal --- */ | |
410 | ||
411 | close(fd[1]); | |
6b837b22 MW |
412 | sel_init(&sel); |
413 | nk.r = r; nk.good = good; | |
d03ab969 | 414 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); |
6b837b22 MW |
415 | sel_initfile(&sel, &sf, fd[0], SEL_READ, kid_read, &nk); |
416 | sel_addfile(&sf); | |
417 | sel_addtimer(&sel, &st, &dead, kid_dead, &nk); | |
418 | while (!nk.donep && !sel_select(&sel)); | |
d03ab969 | 419 | |
420 | /* --- We've finished with it: kill the child process --- * | |
421 | * | |
422 | * This is morally questionable. On the other hand, I don't want to be | |
423 | * held up in the @waitpid@ call if I can possibly help it. Maybe a | |
424 | * double-fork is worth doing here. | |
425 | */ | |
426 | ||
427 | close(fd[0]); | |
6b837b22 | 428 | BURN(nk.buf); |
d03ab969 | 429 | noise_timer(r); |
430 | kill(kid, SIGKILL); | |
431 | waitpid(kid, 0, 0); | |
6b837b22 | 432 | return (nk.ret); |
d03ab969 | 433 | } |
434 | ||
25f654a7 | 435 | /* --- @noise_freewheel@ --- * |
436 | * | |
437 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
438 | * | |
439 | * Returns: Nonzero if some randomness was contributed. | |
440 | * | |
441 | * Use: Runs a free counter for a short while as a desparate attempt | |
442 | * to get randomness from somewhere. This is actually quite | |
443 | * effective. | |
444 | */ | |
445 | ||
446 | #ifdef USE_FREEWHEEL | |
447 | ||
3a5a9d7d | 448 | static sigjmp_buf fwjmp; |
25f654a7 | 449 | |
450 | static void fwalarm(int sig) | |
451 | { | |
452 | siglongjmp(fwjmp, 1); | |
453 | } | |
454 | ||
455 | int noise_freewheel(rand_pool *r) | |
456 | { | |
457 | void (*sigal)(int) = 0; | |
458 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; | |
459 | int rc = 0; | |
460 | volatile uint32 fwcount = 0; | |
461 | ||
462 | if (!sigsetjmp(fwjmp, 1)) { | |
463 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) | |
464 | return (0); | |
465 | if (setitimer(ITIMER_REAL, &itv, &oitv)) | |
466 | goto done; | |
467 | for (;;) | |
468 | fwcount++; | |
469 | } else { | |
470 | octet buf[4]; | |
471 | STORE32(buf, fwcount); | |
472 | rand_add(r, buf, sizeof(buf), 16); | |
473 | rc = 1; | |
474 | } | |
475 | ||
476 | done: | |
477 | signal(SIGALRM, sigal); | |
ff98dc94 MW |
478 | if (oitv.it_value.tv_sec || oitv.it_value.tv_usec) |
479 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); | |
25f654a7 | 480 | setitimer(ITIMER_REAL, &oitv, 0); |
481 | return (rc); | |
482 | } | |
483 | ||
484 | #else | |
485 | ||
486 | int noise_freewheel(rand_pool *r) | |
487 | { | |
488 | return (0); | |
489 | } | |
490 | ||
491 | #endif | |
492 | ||
493 | /* --- @noise_enquire@ --- * | |
494 | * | |
495 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
496 | * | |
497 | * Returns: Nonzero if some randomness was contributed. | |
498 | * | |
499 | * Use: Runs some shell commands to enquire about the prevailing | |
500 | * environment. This can gather quite a lot of low-quality | |
501 | * entropy. | |
502 | */ | |
503 | ||
504 | int noise_enquire(rand_pool *r) | |
505 | { | |
506 | struct tab { | |
507 | const char *cmd; | |
508 | unsigned rate; | |
509 | } tab[] = { | |
510 | { "ps alxww || ps -elf", 16 }, | |
511 | { "netstat -n", 6 }, | |
4108c8d2 | 512 | { "ifconfig -a", 8 }, |
25f654a7 | 513 | { "df", 20 }, |
514 | { "w", 6 }, | |
515 | { "ls -align /tmp/.", 10 }, | |
516 | { 0, 0 } | |
517 | }; | |
518 | int i; | |
519 | ||
520 | for (i = 0; tab[i].cmd; i++) | |
521 | noise_filter(r, tab[i].rate, tab[i].cmd); | |
522 | return (1); | |
523 | } | |
524 | ||
d03ab969 | 525 | /* --- @noise_acquire@ --- * |
526 | * | |
527 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
528 | * | |
529 | * Returns: --- | |
530 | * | |
531 | * Use: Acquires some randomness from somewhere. | |
532 | */ | |
533 | ||
534 | void noise_acquire(rand_pool *r) | |
535 | { | |
25f654a7 | 536 | unsigned i; |
537 | for (i = 0; i < 8; i++) | |
538 | noise_freewheel(r); | |
df40b082 | 539 | if (!noise_devrandom(r) || getenv("CATACOMB_FORCE_ESOTERIC_SOURCES")) { |
25f654a7 | 540 | noise_enquire(r); |
541 | for (i = 0; i < 8; i++) | |
542 | noise_freewheel(r); | |
d03ab969 | 543 | } |
544 | } | |
545 | ||
546 | /*----- That's all, folks -------------------------------------------------*/ |