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