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d03ab969 | 1 | /* -*-c-*- |
2 | * | |
4108c8d2 | 3 | * $Id$ |
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 | ||
d03ab969 | 30 | /*----- Header files ------------------------------------------------------*/ |
31 | ||
178220b3 | 32 | #include "config.h" |
d03ab969 | 33 | |
25f654a7 | 34 | #include <setjmp.h> |
d03ab969 | 35 | #include <stdio.h> |
36 | #include <string.h> | |
37 | #include <signal.h> | |
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 | ||
50 | #include <mLib/bits.h> | |
51 | #include <mLib/tv.h> | |
52 | ||
53 | #include "noise.h" | |
54 | #include "paranoia.h" | |
55 | #include "rand.h" | |
56 | ||
57 | /*----- Magical numbers ---------------------------------------------------*/ | |
58 | ||
59 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ | |
60 | #define MILLION 1000000 /* One million */ | |
61 | ||
62 | /*----- Noise source definition -------------------------------------------*/ | |
63 | ||
4e66da02 | 64 | const rand_source noise_source = { noise_acquire, noise_timer }; |
d03ab969 | 65 | |
66 | /*----- Static variables --------------------------------------------------*/ | |
67 | ||
68 | /* --- Timer differences --- */ | |
69 | ||
70 | static unsigned long noise_last; /* Last time recorded */ | |
71 | static unsigned long noise_diff; /* Last first order difference */ | |
72 | ||
73 | /* --- Setuid program handling --- */ | |
74 | ||
178220b3 | 75 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
76 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ | |
d03ab969 | 77 | |
78 | /*----- Main code ---------------------------------------------------------*/ | |
79 | ||
80 | /* --- @bitcount@ --- * | |
81 | * | |
82 | * Arguments: @unsigned long x@ = a word containing bits | |
83 | * | |
84 | * Returns: The number of bits set in the word. | |
85 | */ | |
86 | ||
87 | static int bitcount(unsigned long x) | |
88 | { | |
89 | char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, | |
90 | 1, 2, 2, 3, 2, 3, 3, 4 }; | |
91 | int count = 0; | |
92 | while (x) { | |
93 | count += ctab[x & 0xfu]; | |
94 | x >>= 4; | |
95 | } | |
96 | return (count); | |
97 | } | |
98 | ||
99 | /* --- @timer@ --- * | |
100 | * | |
101 | * Arguments: @rand_pool *r@ = pointer to randomness pool | |
102 | * @struct timeval *tv@ = pointer to time block | |
103 | * | |
25f654a7 | 104 | * Returns: Nonzero if some randomness was contributed. |
d03ab969 | 105 | * |
106 | * Use: Low-level timer contributor. | |
107 | */ | |
108 | ||
109 | static int timer(rand_pool *r, struct timeval *tv) | |
110 | { | |
111 | unsigned long x, d, dd; | |
112 | int de, dde; | |
113 | int ret; | |
114 | ||
115 | x = tv->tv_usec + MILLION * tv->tv_sec; | |
116 | d = x ^ noise_last; | |
117 | dd = d ^ noise_diff; | |
118 | noise_diff = d; | |
119 | de = bitcount(d); | |
120 | dde = bitcount(dd); | |
121 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); | |
122 | ret = (de || dde); | |
123 | BURN(tv); x = d = dd = de = dde = 0; | |
124 | return (ret); | |
125 | } | |
126 | ||
127 | /* --- @noise_timer@ --- * | |
128 | * | |
129 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
130 | * | |
131 | * Returns: Nonzero if some randomness was contributed. | |
132 | * | |
133 | * Use: Contributes the current time to the randomness pool. | |
134 | * A guess at the number of useful bits contributed is made, | |
135 | * based on first and second order bit differences. This isn't | |
136 | * ever-so reliable, but it's better than nothing. | |
137 | */ | |
138 | ||
139 | int noise_timer(rand_pool *r) | |
140 | { | |
141 | struct timeval tv; | |
142 | gettimeofday(&tv, 0); | |
143 | return (timer(r, &tv)); | |
144 | } | |
145 | ||
146 | /* --- @noise_devrandom@ --- * | |
147 | * | |
148 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
149 | * | |
150 | * Returns: Nonzero if some randomness was contributed. | |
151 | * | |
152 | * Use: Attempts to obtain some randomness from the system entropy | |
153 | * pool. All bits from the device are assumed to be good. | |
154 | */ | |
155 | ||
156 | int noise_devrandom(rand_pool *r) | |
157 | { | |
158 | int fd; | |
159 | octet buf[RAND_POOLSZ]; | |
160 | ssize_t len; | |
161 | int ret = 0; | |
162 | ||
163 | /* --- Be nice to other clients of the random device --- * | |
164 | * | |
165 | * Attempt to open the device nonblockingly. If that works, take up to | |
166 | * one bufferful and then close again. If there's no data to be read, | |
167 | * then that's tough and we go away again, on the grounds that the device | |
168 | * needs to get some more entropy from somewhere. | |
169 | */ | |
170 | ||
25f654a7 | 171 | if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
172 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || | |
173 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { | |
d03ab969 | 174 | if ((len = read(fd, buf, sizeof(buf))) > 0) { |
175 | rand_add(r, buf, len, len * 8); | |
176 | BURN(buf); | |
177 | ret = 1; | |
178 | } | |
179 | close(fd); | |
180 | } | |
181 | noise_timer(r); | |
182 | return (ret); | |
183 | } | |
184 | ||
185 | /* --- @noise_setid@ --- * | |
186 | * | |
187 | * Arguments: @uid_t uid@ = uid to set | |
188 | * @gid_t gid@ = gid to set | |
189 | * | |
190 | * Returns: --- | |
191 | * | |
192 | * Use: Sets the user and group ids to be used by @noise_filter@ | |
193 | * when running child processes. This is useful to avoid | |
194 | * giving shell commands (even carefully written ones) undue | |
099355bc | 195 | * privileges. This interface is Unix-specific |
d03ab969 | 196 | */ |
197 | ||
198 | void noise_setid(uid_t uid, gid_t gid) | |
199 | { | |
200 | noise_uid = uid; | |
201 | noise_gid = gid; | |
202 | } | |
203 | ||
204 | /* --- @noise_filter@ --- * | |
205 | * | |
206 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
207 | * @int good@ = number of good bits per 1024 bits | |
208 | * @const char *c@ = shell command to run | |
209 | * | |
210 | * Returns: Nonzero if some randomness was contributed. | |
211 | * | |
212 | * Use: Attempts to execute a shell command, and dump it into the | |
213 | * randomness pool. A very rough estimate of the number of | |
214 | * good bits is made, based on the size of the command's output. | |
215 | * This function calls @waitpid@, so be careful. Before execing | |
216 | * the command, the process uid and gid are set to the values | |
217 | * given to @noise_setid@, and an attempt is made to reset the | |
218 | * list of supplementary groups. The environment passed to | |
219 | * the command has been severly lobotimized. If the command | |
220 | * fails to complete within a short time period, it is killed. | |
221 | * Paranoid use of close-on-exec flags for file descriptors is | |
222 | * recommended. | |
099355bc | 223 | * |
224 | * This interface is Unix-specific. | |
d03ab969 | 225 | */ |
226 | ||
227 | int noise_filter(rand_pool *r, int good, const char *c) | |
228 | { | |
229 | char buf[4096]; | |
230 | pid_t kid; | |
231 | int fd[2]; | |
232 | struct timeval dead; | |
233 | int ret = 0; | |
234 | const char *env[] = { | |
235 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", | |
236 | 0 | |
237 | }; | |
238 | ||
239 | /* --- Remember when this business started --- */ | |
240 | ||
241 | gettimeofday(&dead, 0); | |
242 | timer(r, &dead); | |
243 | ||
244 | /* --- Create a pipe --- */ | |
245 | ||
246 | if (pipe(fd)) | |
247 | return (ret); | |
248 | ||
249 | /* --- Fork a child off --- */ | |
250 | ||
028b34c6 | 251 | fflush(0); |
d03ab969 | 252 | kid = fork(); |
253 | if (kid < 0) { | |
254 | close(fd[0]); | |
255 | close(fd[1]); | |
256 | return (ret); | |
257 | } | |
258 | ||
259 | /* --- Handle the child end of the deal --- */ | |
260 | ||
d03ab969 | 261 | if (kid == 0) { |
262 | int f; | |
263 | ||
264 | /* --- Set the pipe as standard output, close standard input --- */ | |
265 | ||
266 | close(0); close(1); close(2); | |
267 | ||
268 | if (fd[1] != 1) { | |
269 | if (dup2(fd[1], 1) < 0) _exit(127); | |
270 | close(fd[1]); | |
271 | } | |
272 | ||
273 | if ((f = open("/dev/null", O_RDONLY)) != 0 || | |
274 | (f = open("/dev/null", O_WRONLY)) != 2) | |
275 | _exit(127); | |
276 | ||
277 | /* --- Play games with uids --- */ | |
278 | ||
279 | if (noise_gid != NOISE_NOSETGID) { | |
280 | setgid(noise_gid); | |
281 | setegid(noise_gid); | |
282 | #ifdef HAVE_SETGROUPS | |
283 | setgroups(1, &noise_gid); | |
284 | #endif | |
285 | } | |
286 | ||
287 | if (noise_uid != NOISE_NOSETUID) { | |
288 | setuid(noise_uid); | |
289 | seteuid(noise_uid); | |
290 | } | |
291 | ||
292 | /* --- Start the process up --- */ | |
293 | ||
294 | execle("/bin/sh", "-c", c, (char *)0, env); | |
295 | _exit(127); | |
296 | } | |
297 | ||
298 | /* --- Sort out my end of the deal --- */ | |
299 | ||
300 | close(fd[1]); | |
301 | ||
302 | /* --- Decide on the deadline --- */ | |
303 | ||
304 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); | |
305 | ||
306 | /* --- Now read, and think --- */ | |
307 | ||
308 | for (;;) { | |
309 | struct timeval now, diff; | |
310 | fd_set rd; | |
311 | ||
312 | gettimeofday(&now, 0); | |
313 | timer(r, &now); | |
314 | if (TV_CMP(&now, >, &dead)) | |
315 | break; | |
316 | TV_SUB(&diff, &dead, &now); | |
317 | ||
318 | FD_ZERO(&rd); | |
319 | FD_SET(fd[0], &rd); | |
320 | ||
321 | if (select(fd[0] + 1, &rd, 0, 0, &diff) < 0) | |
322 | break; | |
323 | if (FD_ISSET(fd[0], &rd)) { | |
324 | ssize_t sz; | |
325 | int goodbits; | |
326 | ||
327 | if ((sz = read(fd[0], buf, sizeof(buf))) <= 0) | |
328 | break; | |
329 | goodbits = (sz * good) / 128; | |
330 | rand_add(r, buf, sz, goodbits); | |
331 | ret = 1; | |
332 | } | |
333 | } | |
334 | ||
335 | /* --- We've finished with it: kill the child process --- * | |
336 | * | |
337 | * This is morally questionable. On the other hand, I don't want to be | |
338 | * held up in the @waitpid@ call if I can possibly help it. Maybe a | |
339 | * double-fork is worth doing here. | |
340 | */ | |
341 | ||
342 | close(fd[0]); | |
343 | BURN(buf); | |
344 | noise_timer(r); | |
345 | kill(kid, SIGKILL); | |
346 | waitpid(kid, 0, 0); | |
347 | return (ret); | |
348 | } | |
349 | ||
25f654a7 | 350 | /* --- @noise_freewheel@ --- * |
351 | * | |
352 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
353 | * | |
354 | * Returns: Nonzero if some randomness was contributed. | |
355 | * | |
356 | * Use: Runs a free counter for a short while as a desparate attempt | |
357 | * to get randomness from somewhere. This is actually quite | |
358 | * effective. | |
359 | */ | |
360 | ||
361 | #ifdef USE_FREEWHEEL | |
362 | ||
363 | static jmp_buf fwjmp; | |
364 | ||
365 | static void fwalarm(int sig) | |
366 | { | |
367 | siglongjmp(fwjmp, 1); | |
368 | } | |
369 | ||
370 | int noise_freewheel(rand_pool *r) | |
371 | { | |
372 | void (*sigal)(int) = 0; | |
373 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; | |
374 | int rc = 0; | |
375 | volatile uint32 fwcount = 0; | |
376 | ||
377 | if (!sigsetjmp(fwjmp, 1)) { | |
378 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) | |
379 | return (0); | |
380 | if (setitimer(ITIMER_REAL, &itv, &oitv)) | |
381 | goto done; | |
382 | for (;;) | |
383 | fwcount++; | |
384 | } else { | |
385 | octet buf[4]; | |
386 | STORE32(buf, fwcount); | |
387 | rand_add(r, buf, sizeof(buf), 16); | |
388 | rc = 1; | |
389 | } | |
390 | ||
391 | done: | |
392 | signal(SIGALRM, sigal); | |
ff98dc94 MW |
393 | if (oitv.it_value.tv_sec || oitv.it_value.tv_usec) |
394 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); | |
25f654a7 | 395 | setitimer(ITIMER_REAL, &oitv, 0); |
396 | return (rc); | |
397 | } | |
398 | ||
399 | #else | |
400 | ||
401 | int noise_freewheel(rand_pool *r) | |
402 | { | |
403 | return (0); | |
404 | } | |
405 | ||
406 | #endif | |
407 | ||
408 | /* --- @noise_enquire@ --- * | |
409 | * | |
410 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
411 | * | |
412 | * Returns: Nonzero if some randomness was contributed. | |
413 | * | |
414 | * Use: Runs some shell commands to enquire about the prevailing | |
415 | * environment. This can gather quite a lot of low-quality | |
416 | * entropy. | |
417 | */ | |
418 | ||
419 | int noise_enquire(rand_pool *r) | |
420 | { | |
421 | struct tab { | |
422 | const char *cmd; | |
423 | unsigned rate; | |
424 | } tab[] = { | |
425 | { "ps alxww || ps -elf", 16 }, | |
426 | { "netstat -n", 6 }, | |
4108c8d2 | 427 | { "ifconfig -a", 8 }, |
25f654a7 | 428 | { "df", 20 }, |
429 | { "w", 6 }, | |
430 | { "ls -align /tmp/.", 10 }, | |
431 | { 0, 0 } | |
432 | }; | |
433 | int i; | |
434 | ||
435 | for (i = 0; tab[i].cmd; i++) | |
436 | noise_filter(r, tab[i].rate, tab[i].cmd); | |
437 | return (1); | |
438 | } | |
439 | ||
d03ab969 | 440 | /* --- @noise_acquire@ --- * |
441 | * | |
442 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
443 | * | |
444 | * Returns: --- | |
445 | * | |
446 | * Use: Acquires some randomness from somewhere. | |
447 | */ | |
448 | ||
449 | void noise_acquire(rand_pool *r) | |
450 | { | |
25f654a7 | 451 | unsigned i; |
452 | for (i = 0; i < 8; i++) | |
453 | noise_freewheel(r); | |
d03ab969 | 454 | if (!noise_devrandom(r)) { |
25f654a7 | 455 | noise_enquire(r); |
456 | for (i = 0; i < 8; i++) | |
457 | noise_freewheel(r); | |
d03ab969 | 458 | } |
459 | } | |
460 | ||
461 | /*----- That's all, folks -------------------------------------------------*/ |