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