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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 | |
25f654a7 | 32 | #include <setjmp.h> |
d03ab969 | 33 | #include <stdio.h> |
34 | #include <string.h> | |
35 | #include <signal.h> | |
36 | ||
37 | #include <sys/types.h> | |
38 | #include <sys/time.h> | |
39 | #include <sys/wait.h> | |
40 | ||
41 | #include <fcntl.h> | |
42 | #include <unistd.h> | |
43 | ||
44 | #ifdef HAVE_SETGROUPS | |
45 | # include <grp.h> | |
46 | #endif | |
47 | ||
48 | #include <mLib/bits.h> | |
49 | #include <mLib/tv.h> | |
50 | ||
51 | #include "noise.h" | |
52 | #include "paranoia.h" | |
53 | #include "rand.h" | |
54 | ||
55 | /*----- Magical numbers ---------------------------------------------------*/ | |
56 | ||
57 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ | |
58 | #define MILLION 1000000 /* One million */ | |
59 | ||
60 | /*----- Noise source definition -------------------------------------------*/ | |
61 | ||
4e66da02 | 62 | const rand_source noise_source = { noise_acquire, noise_timer }; |
d03ab969 | 63 | |
64 | /*----- Static variables --------------------------------------------------*/ | |
65 | ||
66 | /* --- Timer differences --- */ | |
67 | ||
68 | static unsigned long noise_last; /* Last time recorded */ | |
69 | static unsigned long noise_diff; /* Last first order difference */ | |
70 | ||
71 | /* --- Setuid program handling --- */ | |
72 | ||
178220b3 | 73 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
74 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ | |
d03ab969 | 75 | |
76 | /*----- Main code ---------------------------------------------------------*/ | |
77 | ||
78 | /* --- @bitcount@ --- * | |
79 | * | |
80 | * Arguments: @unsigned long x@ = a word containing bits | |
81 | * | |
82 | * Returns: The number of bits set in the word. | |
83 | */ | |
84 | ||
85 | static int bitcount(unsigned long x) | |
86 | { | |
87 | char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, | |
88 | 1, 2, 2, 3, 2, 3, 3, 4 }; | |
89 | int count = 0; | |
90 | while (x) { | |
91 | count += ctab[x & 0xfu]; | |
92 | x >>= 4; | |
93 | } | |
94 | return (count); | |
95 | } | |
96 | ||
97 | /* --- @timer@ --- * | |
98 | * | |
99 | * Arguments: @rand_pool *r@ = pointer to randomness pool | |
100 | * @struct timeval *tv@ = pointer to time block | |
101 | * | |
25f654a7 | 102 | * Returns: Nonzero if some randomness was contributed. |
d03ab969 | 103 | * |
104 | * Use: Low-level timer contributor. | |
105 | */ | |
106 | ||
107 | static int timer(rand_pool *r, struct timeval *tv) | |
108 | { | |
109 | unsigned long x, d, dd; | |
110 | int de, dde; | |
111 | int ret; | |
45c0fd36 | 112 | |
d03ab969 | 113 | x = tv->tv_usec + MILLION * tv->tv_sec; |
114 | d = x ^ noise_last; | |
115 | dd = d ^ noise_diff; | |
116 | noise_diff = d; | |
117 | de = bitcount(d); | |
118 | dde = bitcount(dd); | |
119 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); | |
120 | ret = (de || dde); | |
121 | BURN(tv); x = d = dd = de = dde = 0; | |
122 | return (ret); | |
123 | } | |
124 | ||
125 | /* --- @noise_timer@ --- * | |
126 | * | |
127 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
128 | * | |
129 | * Returns: Nonzero if some randomness was contributed. | |
130 | * | |
131 | * Use: Contributes the current time to the randomness pool. | |
132 | * A guess at the number of useful bits contributed is made, | |
133 | * based on first and second order bit differences. This isn't | |
134 | * ever-so reliable, but it's better than nothing. | |
135 | */ | |
136 | ||
137 | int noise_timer(rand_pool *r) | |
138 | { | |
139 | struct timeval tv; | |
140 | gettimeofday(&tv, 0); | |
141 | return (timer(r, &tv)); | |
142 | } | |
143 | ||
144 | /* --- @noise_devrandom@ --- * | |
145 | * | |
146 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
147 | * | |
148 | * Returns: Nonzero if some randomness was contributed. | |
149 | * | |
150 | * Use: Attempts to obtain some randomness from the system entropy | |
151 | * pool. All bits from the device are assumed to be good. | |
152 | */ | |
153 | ||
154 | int noise_devrandom(rand_pool *r) | |
155 | { | |
156 | int fd; | |
157 | octet buf[RAND_POOLSZ]; | |
158 | ssize_t len; | |
159 | int ret = 0; | |
160 | ||
161 | /* --- Be nice to other clients of the random device --- * | |
162 | * | |
163 | * Attempt to open the device nonblockingly. If that works, take up to | |
164 | * one bufferful and then close again. If there's no data to be read, | |
165 | * then that's tough and we go away again, on the grounds that the device | |
166 | * needs to get some more entropy from somewhere. | |
167 | */ | |
168 | ||
25f654a7 | 169 | if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
170 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || | |
171 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { | |
d03ab969 | 172 | if ((len = read(fd, buf, sizeof(buf))) > 0) { |
173 | rand_add(r, buf, len, len * 8); | |
174 | BURN(buf); | |
175 | ret = 1; | |
176 | } | |
177 | close(fd); | |
178 | } | |
179 | noise_timer(r); | |
180 | return (ret); | |
181 | } | |
182 | ||
183 | /* --- @noise_setid@ --- * | |
184 | * | |
185 | * Arguments: @uid_t uid@ = uid to set | |
186 | * @gid_t gid@ = gid to set | |
187 | * | |
188 | * Returns: --- | |
189 | * | |
190 | * Use: Sets the user and group ids to be used by @noise_filter@ | |
191 | * when running child processes. This is useful to avoid | |
192 | * giving shell commands (even carefully written ones) undue | |
099355bc | 193 | * privileges. This interface is Unix-specific |
d03ab969 | 194 | */ |
195 | ||
196 | void noise_setid(uid_t uid, gid_t gid) | |
197 | { | |
198 | noise_uid = uid; | |
199 | noise_gid = gid; | |
200 | } | |
201 | ||
202 | /* --- @noise_filter@ --- * | |
203 | * | |
204 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
205 | * @int good@ = number of good bits per 1024 bits | |
206 | * @const char *c@ = shell command to run | |
207 | * | |
208 | * Returns: Nonzero if some randomness was contributed. | |
209 | * | |
210 | * Use: Attempts to execute a shell command, and dump it into the | |
211 | * randomness pool. A very rough estimate of the number of | |
212 | * good bits is made, based on the size of the command's output. | |
213 | * This function calls @waitpid@, so be careful. Before execing | |
214 | * the command, the process uid and gid are set to the values | |
215 | * given to @noise_setid@, and an attempt is made to reset the | |
216 | * list of supplementary groups. The environment passed to | |
217 | * the command has been severly lobotimized. If the command | |
218 | * fails to complete within a short time period, it is killed. | |
219 | * Paranoid use of close-on-exec flags for file descriptors is | |
220 | * recommended. | |
099355bc | 221 | * |
222 | * This interface is Unix-specific. | |
d03ab969 | 223 | */ |
224 | ||
225 | int noise_filter(rand_pool *r, int good, const char *c) | |
226 | { | |
227 | char buf[4096]; | |
228 | pid_t kid; | |
229 | int fd[2]; | |
230 | struct timeval dead; | |
231 | int ret = 0; | |
232 | const char *env[] = { | |
233 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", | |
234 | 0 | |
235 | }; | |
236 | ||
237 | /* --- Remember when this business started --- */ | |
238 | ||
239 | gettimeofday(&dead, 0); | |
240 | timer(r, &dead); | |
241 | ||
242 | /* --- Create a pipe --- */ | |
243 | ||
244 | if (pipe(fd)) | |
245 | return (ret); | |
246 | ||
247 | /* --- Fork a child off --- */ | |
248 | ||
028b34c6 | 249 | fflush(0); |
d03ab969 | 250 | kid = fork(); |
251 | if (kid < 0) { | |
252 | close(fd[0]); | |
253 | close(fd[1]); | |
254 | return (ret); | |
255 | } | |
256 | ||
257 | /* --- Handle the child end of the deal --- */ | |
258 | ||
d03ab969 | 259 | if (kid == 0) { |
260 | int f; | |
261 | ||
262 | /* --- Set the pipe as standard output, close standard input --- */ | |
263 | ||
264 | close(0); close(1); close(2); | |
265 | ||
266 | if (fd[1] != 1) { | |
267 | if (dup2(fd[1], 1) < 0) _exit(127); | |
268 | close(fd[1]); | |
269 | } | |
270 | ||
271 | if ((f = open("/dev/null", O_RDONLY)) != 0 || | |
272 | (f = open("/dev/null", O_WRONLY)) != 2) | |
273 | _exit(127); | |
274 | ||
275 | /* --- Play games with uids --- */ | |
276 | ||
277 | if (noise_gid != NOISE_NOSETGID) { | |
278 | setgid(noise_gid); | |
279 | setegid(noise_gid); | |
280 | #ifdef HAVE_SETGROUPS | |
281 | setgroups(1, &noise_gid); | |
282 | #endif | |
283 | } | |
284 | ||
285 | if (noise_uid != NOISE_NOSETUID) { | |
286 | setuid(noise_uid); | |
287 | seteuid(noise_uid); | |
288 | } | |
289 | ||
290 | /* --- Start the process up --- */ | |
291 | ||
292 | execle("/bin/sh", "-c", c, (char *)0, env); | |
293 | _exit(127); | |
294 | } | |
295 | ||
296 | /* --- Sort out my end of the deal --- */ | |
297 | ||
298 | close(fd[1]); | |
299 | ||
300 | /* --- Decide on the deadline --- */ | |
301 | ||
302 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); | |
303 | ||
304 | /* --- Now read, and think --- */ | |
305 | ||
306 | for (;;) { | |
307 | struct timeval now, diff; | |
308 | fd_set rd; | |
309 | ||
310 | gettimeofday(&now, 0); | |
311 | timer(r, &now); | |
312 | if (TV_CMP(&now, >, &dead)) | |
313 | break; | |
314 | TV_SUB(&diff, &dead, &now); | |
315 | ||
316 | FD_ZERO(&rd); | |
317 | FD_SET(fd[0], &rd); | |
318 | ||
319 | if (select(fd[0] + 1, &rd, 0, 0, &diff) < 0) | |
320 | break; | |
321 | if (FD_ISSET(fd[0], &rd)) { | |
322 | ssize_t sz; | |
323 | int goodbits; | |
324 | ||
325 | if ((sz = read(fd[0], buf, sizeof(buf))) <= 0) | |
326 | break; | |
327 | goodbits = (sz * good) / 128; | |
328 | rand_add(r, buf, sz, goodbits); | |
329 | ret = 1; | |
330 | } | |
331 | } | |
332 | ||
333 | /* --- We've finished with it: kill the child process --- * | |
334 | * | |
335 | * This is morally questionable. On the other hand, I don't want to be | |
336 | * held up in the @waitpid@ call if I can possibly help it. Maybe a | |
337 | * double-fork is worth doing here. | |
338 | */ | |
339 | ||
340 | close(fd[0]); | |
341 | BURN(buf); | |
342 | noise_timer(r); | |
343 | kill(kid, SIGKILL); | |
344 | waitpid(kid, 0, 0); | |
345 | return (ret); | |
346 | } | |
347 | ||
25f654a7 | 348 | /* --- @noise_freewheel@ --- * |
349 | * | |
350 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
351 | * | |
352 | * Returns: Nonzero if some randomness was contributed. | |
353 | * | |
354 | * Use: Runs a free counter for a short while as a desparate attempt | |
355 | * to get randomness from somewhere. This is actually quite | |
356 | * effective. | |
357 | */ | |
358 | ||
359 | #ifdef USE_FREEWHEEL | |
360 | ||
361 | static jmp_buf fwjmp; | |
362 | ||
363 | static void fwalarm(int sig) | |
364 | { | |
365 | siglongjmp(fwjmp, 1); | |
366 | } | |
367 | ||
368 | int noise_freewheel(rand_pool *r) | |
369 | { | |
370 | void (*sigal)(int) = 0; | |
371 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; | |
372 | int rc = 0; | |
373 | volatile uint32 fwcount = 0; | |
374 | ||
375 | if (!sigsetjmp(fwjmp, 1)) { | |
376 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) | |
377 | return (0); | |
378 | if (setitimer(ITIMER_REAL, &itv, &oitv)) | |
379 | goto done; | |
380 | for (;;) | |
381 | fwcount++; | |
382 | } else { | |
383 | octet buf[4]; | |
384 | STORE32(buf, fwcount); | |
385 | rand_add(r, buf, sizeof(buf), 16); | |
386 | rc = 1; | |
387 | } | |
388 | ||
389 | done: | |
390 | signal(SIGALRM, sigal); | |
ff98dc94 MW |
391 | if (oitv.it_value.tv_sec || oitv.it_value.tv_usec) |
392 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); | |
25f654a7 | 393 | setitimer(ITIMER_REAL, &oitv, 0); |
394 | return (rc); | |
395 | } | |
396 | ||
397 | #else | |
398 | ||
399 | int noise_freewheel(rand_pool *r) | |
400 | { | |
401 | return (0); | |
402 | } | |
403 | ||
404 | #endif | |
405 | ||
406 | /* --- @noise_enquire@ --- * | |
407 | * | |
408 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
409 | * | |
410 | * Returns: Nonzero if some randomness was contributed. | |
411 | * | |
412 | * Use: Runs some shell commands to enquire about the prevailing | |
413 | * environment. This can gather quite a lot of low-quality | |
414 | * entropy. | |
415 | */ | |
416 | ||
417 | int noise_enquire(rand_pool *r) | |
418 | { | |
419 | struct tab { | |
420 | const char *cmd; | |
421 | unsigned rate; | |
422 | } tab[] = { | |
423 | { "ps alxww || ps -elf", 16 }, | |
424 | { "netstat -n", 6 }, | |
4108c8d2 | 425 | { "ifconfig -a", 8 }, |
25f654a7 | 426 | { "df", 20 }, |
427 | { "w", 6 }, | |
428 | { "ls -align /tmp/.", 10 }, | |
429 | { 0, 0 } | |
430 | }; | |
431 | int i; | |
432 | ||
433 | for (i = 0; tab[i].cmd; i++) | |
434 | noise_filter(r, tab[i].rate, tab[i].cmd); | |
435 | return (1); | |
436 | } | |
437 | ||
d03ab969 | 438 | /* --- @noise_acquire@ --- * |
439 | * | |
440 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
441 | * | |
442 | * Returns: --- | |
443 | * | |
444 | * Use: Acquires some randomness from somewhere. | |
445 | */ | |
446 | ||
447 | void noise_acquire(rand_pool *r) | |
448 | { | |
25f654a7 | 449 | unsigned i; |
450 | for (i = 0; i < 8; i++) | |
451 | noise_freewheel(r); | |
d03ab969 | 452 | if (!noise_devrandom(r)) { |
25f654a7 | 453 | noise_enquire(r); |
454 | for (i = 0; i < 8; i++) | |
455 | noise_freewheel(r); | |
d03ab969 | 456 | } |
457 | } | |
458 | ||
459 | /*----- That's all, folks -------------------------------------------------*/ |