d03ab969 |
1 | /* -*-c-*- |
2 | * |
4e66da02 |
3 | * $Id: noise.c,v 1.7 2004/04/02 01:03:49 mdw Exp $ |
d03ab969 |
4 | * |
099355bc |
5 | * Acquisition of environmental noise (Unix-specific) |
d03ab969 |
6 | * |
7 | * (c) 1998 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: noise.c,v $ |
4e66da02 |
33 | * Revision 1.7 2004/04/02 01:03:49 mdw |
34 | * Miscellaneous constification. |
35 | * |
25f654a7 |
36 | * Revision 1.6 2000/06/17 12:57:47 mdw |
37 | * New free counter noise generator, for use if /dev/random is |
38 | * unavailable. |
39 | * |
099355bc |
40 | * Revision 1.5 1999/12/22 15:57:55 mdw |
41 | * Label system-specific parts more clearly. |
42 | * |
c141f4b6 |
43 | * Revision 1.4 1999/12/10 23:25:15 mdw |
44 | * Bug fix: remove old spurious fflush. |
45 | * |
028b34c6 |
46 | * Revision 1.3 1999/12/10 23:24:11 mdw |
47 | * Bug fix: flush buffers before forking. |
48 | * |
178220b3 |
49 | * Revision 1.2 1999/11/11 00:59:08 mdw |
50 | * A bit of reformatting. Initialize the uid and gid correctly. |
51 | * |
d03ab969 |
52 | * Revision 1.1 1999/09/03 08:41:12 mdw |
53 | * Initial import. |
54 | * |
55 | */ |
56 | |
57 | /*----- Header files ------------------------------------------------------*/ |
58 | |
178220b3 |
59 | #include "config.h" |
d03ab969 |
60 | |
25f654a7 |
61 | #include <setjmp.h> |
d03ab969 |
62 | #include <stdio.h> |
63 | #include <string.h> |
64 | #include <signal.h> |
65 | |
66 | #include <sys/types.h> |
67 | #include <sys/time.h> |
68 | #include <sys/wait.h> |
69 | |
70 | #include <fcntl.h> |
71 | #include <unistd.h> |
72 | |
73 | #ifdef HAVE_SETGROUPS |
74 | # include <grp.h> |
75 | #endif |
76 | |
77 | #include <mLib/bits.h> |
78 | #include <mLib/tv.h> |
79 | |
80 | #include "noise.h" |
81 | #include "paranoia.h" |
82 | #include "rand.h" |
83 | |
84 | /*----- Magical numbers ---------------------------------------------------*/ |
85 | |
86 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ |
87 | #define MILLION 1000000 /* One million */ |
88 | |
89 | /*----- Noise source definition -------------------------------------------*/ |
90 | |
4e66da02 |
91 | const rand_source noise_source = { noise_acquire, noise_timer }; |
d03ab969 |
92 | |
93 | /*----- Static variables --------------------------------------------------*/ |
94 | |
95 | /* --- Timer differences --- */ |
96 | |
97 | static unsigned long noise_last; /* Last time recorded */ |
98 | static unsigned long noise_diff; /* Last first order difference */ |
99 | |
100 | /* --- Setuid program handling --- */ |
101 | |
178220b3 |
102 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
103 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ |
d03ab969 |
104 | |
105 | /*----- Main code ---------------------------------------------------------*/ |
106 | |
107 | /* --- @bitcount@ --- * |
108 | * |
109 | * Arguments: @unsigned long x@ = a word containing bits |
110 | * |
111 | * Returns: The number of bits set in the word. |
112 | */ |
113 | |
114 | static int bitcount(unsigned long x) |
115 | { |
116 | char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, |
117 | 1, 2, 2, 3, 2, 3, 3, 4 }; |
118 | int count = 0; |
119 | while (x) { |
120 | count += ctab[x & 0xfu]; |
121 | x >>= 4; |
122 | } |
123 | return (count); |
124 | } |
125 | |
126 | /* --- @timer@ --- * |
127 | * |
128 | * Arguments: @rand_pool *r@ = pointer to randomness pool |
129 | * @struct timeval *tv@ = pointer to time block |
130 | * |
25f654a7 |
131 | * Returns: Nonzero if some randomness was contributed. |
d03ab969 |
132 | * |
133 | * Use: Low-level timer contributor. |
134 | */ |
135 | |
136 | static int timer(rand_pool *r, struct timeval *tv) |
137 | { |
138 | unsigned long x, d, dd; |
139 | int de, dde; |
140 | int ret; |
141 | |
142 | x = tv->tv_usec + MILLION * tv->tv_sec; |
143 | d = x ^ noise_last; |
144 | dd = d ^ noise_diff; |
145 | noise_diff = d; |
146 | de = bitcount(d); |
147 | dde = bitcount(dd); |
148 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); |
149 | ret = (de || dde); |
150 | BURN(tv); x = d = dd = de = dde = 0; |
151 | return (ret); |
152 | } |
153 | |
154 | /* --- @noise_timer@ --- * |
155 | * |
156 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
157 | * |
158 | * Returns: Nonzero if some randomness was contributed. |
159 | * |
160 | * Use: Contributes the current time to the randomness pool. |
161 | * A guess at the number of useful bits contributed is made, |
162 | * based on first and second order bit differences. This isn't |
163 | * ever-so reliable, but it's better than nothing. |
164 | */ |
165 | |
166 | int noise_timer(rand_pool *r) |
167 | { |
168 | struct timeval tv; |
169 | gettimeofday(&tv, 0); |
170 | return (timer(r, &tv)); |
171 | } |
172 | |
173 | /* --- @noise_devrandom@ --- * |
174 | * |
175 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
176 | * |
177 | * Returns: Nonzero if some randomness was contributed. |
178 | * |
179 | * Use: Attempts to obtain some randomness from the system entropy |
180 | * pool. All bits from the device are assumed to be good. |
181 | */ |
182 | |
183 | int noise_devrandom(rand_pool *r) |
184 | { |
185 | int fd; |
186 | octet buf[RAND_POOLSZ]; |
187 | ssize_t len; |
188 | int ret = 0; |
189 | |
190 | /* --- Be nice to other clients of the random device --- * |
191 | * |
192 | * Attempt to open the device nonblockingly. If that works, take up to |
193 | * one bufferful and then close again. If there's no data to be read, |
194 | * then that's tough and we go away again, on the grounds that the device |
195 | * needs to get some more entropy from somewhere. |
196 | */ |
197 | |
25f654a7 |
198 | if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
199 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
200 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { |
d03ab969 |
201 | if ((len = read(fd, buf, sizeof(buf))) > 0) { |
202 | rand_add(r, buf, len, len * 8); |
203 | BURN(buf); |
204 | ret = 1; |
205 | } |
206 | close(fd); |
207 | } |
208 | noise_timer(r); |
209 | return (ret); |
210 | } |
211 | |
212 | /* --- @noise_setid@ --- * |
213 | * |
214 | * Arguments: @uid_t uid@ = uid to set |
215 | * @gid_t gid@ = gid to set |
216 | * |
217 | * Returns: --- |
218 | * |
219 | * Use: Sets the user and group ids to be used by @noise_filter@ |
220 | * when running child processes. This is useful to avoid |
221 | * giving shell commands (even carefully written ones) undue |
099355bc |
222 | * privileges. This interface is Unix-specific |
d03ab969 |
223 | */ |
224 | |
225 | void noise_setid(uid_t uid, gid_t gid) |
226 | { |
227 | noise_uid = uid; |
228 | noise_gid = gid; |
229 | } |
230 | |
231 | /* --- @noise_filter@ --- * |
232 | * |
233 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
234 | * @int good@ = number of good bits per 1024 bits |
235 | * @const char *c@ = shell command to run |
236 | * |
237 | * Returns: Nonzero if some randomness was contributed. |
238 | * |
239 | * Use: Attempts to execute a shell command, and dump it into the |
240 | * randomness pool. A very rough estimate of the number of |
241 | * good bits is made, based on the size of the command's output. |
242 | * This function calls @waitpid@, so be careful. Before execing |
243 | * the command, the process uid and gid are set to the values |
244 | * given to @noise_setid@, and an attempt is made to reset the |
245 | * list of supplementary groups. The environment passed to |
246 | * the command has been severly lobotimized. If the command |
247 | * fails to complete within a short time period, it is killed. |
248 | * Paranoid use of close-on-exec flags for file descriptors is |
249 | * recommended. |
099355bc |
250 | * |
251 | * This interface is Unix-specific. |
d03ab969 |
252 | */ |
253 | |
254 | int noise_filter(rand_pool *r, int good, const char *c) |
255 | { |
256 | char buf[4096]; |
257 | pid_t kid; |
258 | int fd[2]; |
259 | struct timeval dead; |
260 | int ret = 0; |
261 | const char *env[] = { |
262 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", |
263 | 0 |
264 | }; |
265 | |
266 | /* --- Remember when this business started --- */ |
267 | |
268 | gettimeofday(&dead, 0); |
269 | timer(r, &dead); |
270 | |
271 | /* --- Create a pipe --- */ |
272 | |
273 | if (pipe(fd)) |
274 | return (ret); |
275 | |
276 | /* --- Fork a child off --- */ |
277 | |
028b34c6 |
278 | fflush(0); |
d03ab969 |
279 | kid = fork(); |
280 | if (kid < 0) { |
281 | close(fd[0]); |
282 | close(fd[1]); |
283 | return (ret); |
284 | } |
285 | |
286 | /* --- Handle the child end of the deal --- */ |
287 | |
d03ab969 |
288 | if (kid == 0) { |
289 | int f; |
290 | |
291 | /* --- Set the pipe as standard output, close standard input --- */ |
292 | |
293 | close(0); close(1); close(2); |
294 | |
295 | if (fd[1] != 1) { |
296 | if (dup2(fd[1], 1) < 0) _exit(127); |
297 | close(fd[1]); |
298 | } |
299 | |
300 | if ((f = open("/dev/null", O_RDONLY)) != 0 || |
301 | (f = open("/dev/null", O_WRONLY)) != 2) |
302 | _exit(127); |
303 | |
304 | /* --- Play games with uids --- */ |
305 | |
306 | if (noise_gid != NOISE_NOSETGID) { |
307 | setgid(noise_gid); |
308 | setegid(noise_gid); |
309 | #ifdef HAVE_SETGROUPS |
310 | setgroups(1, &noise_gid); |
311 | #endif |
312 | } |
313 | |
314 | if (noise_uid != NOISE_NOSETUID) { |
315 | setuid(noise_uid); |
316 | seteuid(noise_uid); |
317 | } |
318 | |
319 | /* --- Start the process up --- */ |
320 | |
321 | execle("/bin/sh", "-c", c, (char *)0, env); |
322 | _exit(127); |
323 | } |
324 | |
325 | /* --- Sort out my end of the deal --- */ |
326 | |
327 | close(fd[1]); |
328 | |
329 | /* --- Decide on the deadline --- */ |
330 | |
331 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); |
332 | |
333 | /* --- Now read, and think --- */ |
334 | |
335 | for (;;) { |
336 | struct timeval now, diff; |
337 | fd_set rd; |
338 | |
339 | gettimeofday(&now, 0); |
340 | timer(r, &now); |
341 | if (TV_CMP(&now, >, &dead)) |
342 | break; |
343 | TV_SUB(&diff, &dead, &now); |
344 | |
345 | FD_ZERO(&rd); |
346 | FD_SET(fd[0], &rd); |
347 | |
348 | if (select(fd[0] + 1, &rd, 0, 0, &diff) < 0) |
349 | break; |
350 | if (FD_ISSET(fd[0], &rd)) { |
351 | ssize_t sz; |
352 | int goodbits; |
353 | |
354 | if ((sz = read(fd[0], buf, sizeof(buf))) <= 0) |
355 | break; |
356 | goodbits = (sz * good) / 128; |
357 | rand_add(r, buf, sz, goodbits); |
358 | ret = 1; |
359 | } |
360 | } |
361 | |
362 | /* --- We've finished with it: kill the child process --- * |
363 | * |
364 | * This is morally questionable. On the other hand, I don't want to be |
365 | * held up in the @waitpid@ call if I can possibly help it. Maybe a |
366 | * double-fork is worth doing here. |
367 | */ |
368 | |
369 | close(fd[0]); |
370 | BURN(buf); |
371 | noise_timer(r); |
372 | kill(kid, SIGKILL); |
373 | waitpid(kid, 0, 0); |
374 | return (ret); |
375 | } |
376 | |
25f654a7 |
377 | /* --- @noise_freewheel@ --- * |
378 | * |
379 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
380 | * |
381 | * Returns: Nonzero if some randomness was contributed. |
382 | * |
383 | * Use: Runs a free counter for a short while as a desparate attempt |
384 | * to get randomness from somewhere. This is actually quite |
385 | * effective. |
386 | */ |
387 | |
388 | #ifdef USE_FREEWHEEL |
389 | |
390 | static jmp_buf fwjmp; |
391 | |
392 | static void fwalarm(int sig) |
393 | { |
394 | siglongjmp(fwjmp, 1); |
395 | } |
396 | |
397 | int noise_freewheel(rand_pool *r) |
398 | { |
399 | void (*sigal)(int) = 0; |
400 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; |
401 | int rc = 0; |
402 | volatile uint32 fwcount = 0; |
403 | |
404 | if (!sigsetjmp(fwjmp, 1)) { |
405 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) |
406 | return (0); |
407 | if (setitimer(ITIMER_REAL, &itv, &oitv)) |
408 | goto done; |
409 | for (;;) |
410 | fwcount++; |
411 | } else { |
412 | octet buf[4]; |
413 | STORE32(buf, fwcount); |
414 | rand_add(r, buf, sizeof(buf), 16); |
415 | rc = 1; |
416 | } |
417 | |
418 | done: |
419 | signal(SIGALRM, sigal); |
420 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); |
421 | setitimer(ITIMER_REAL, &oitv, 0); |
422 | return (rc); |
423 | } |
424 | |
425 | #else |
426 | |
427 | int noise_freewheel(rand_pool *r) |
428 | { |
429 | return (0); |
430 | } |
431 | |
432 | #endif |
433 | |
434 | /* --- @noise_enquire@ --- * |
435 | * |
436 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
437 | * |
438 | * Returns: Nonzero if some randomness was contributed. |
439 | * |
440 | * Use: Runs some shell commands to enquire about the prevailing |
441 | * environment. This can gather quite a lot of low-quality |
442 | * entropy. |
443 | */ |
444 | |
445 | int noise_enquire(rand_pool *r) |
446 | { |
447 | struct tab { |
448 | const char *cmd; |
449 | unsigned rate; |
450 | } tab[] = { |
451 | { "ps alxww || ps -elf", 16 }, |
452 | { "netstat -n", 6 }, |
453 | { "df", 20 }, |
454 | { "w", 6 }, |
455 | { "ls -align /tmp/.", 10 }, |
456 | { 0, 0 } |
457 | }; |
458 | int i; |
459 | |
460 | for (i = 0; tab[i].cmd; i++) |
461 | noise_filter(r, tab[i].rate, tab[i].cmd); |
462 | return (1); |
463 | } |
464 | |
d03ab969 |
465 | /* --- @noise_acquire@ --- * |
466 | * |
467 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
468 | * |
469 | * Returns: --- |
470 | * |
471 | * Use: Acquires some randomness from somewhere. |
472 | */ |
473 | |
474 | void noise_acquire(rand_pool *r) |
475 | { |
25f654a7 |
476 | unsigned i; |
477 | for (i = 0; i < 8; i++) |
478 | noise_freewheel(r); |
d03ab969 |
479 | if (!noise_devrandom(r)) { |
25f654a7 |
480 | noise_enquire(r); |
481 | for (i = 0; i < 8; i++) |
482 | noise_freewheel(r); |
d03ab969 |
483 | } |
484 | } |
485 | |
486 | /*----- That's all, folks -------------------------------------------------*/ |