Commit | Line | Data |
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d03ab969 | 1 | /* -*-c-*- |
d03ab969 | 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> |
93f563bf | 33 | #include <signal.h> |
d03ab969 | 34 | #include <stdio.h> |
df40b082 | 35 | #include <stdlib.h> |
d03ab969 | 36 | #include <string.h> |
d03ab969 | 37 | |
38 | #include <sys/types.h> | |
39 | #include <sys/time.h> | |
40 | #include <sys/wait.h> | |
41 | ||
42 | #include <fcntl.h> | |
43 | #include <unistd.h> | |
44 | ||
45 | #ifdef HAVE_SETGROUPS | |
46 | # include <grp.h> | |
47 | #endif | |
48 | ||
49 | #include <mLib/bits.h> | |
cbc993ef | 50 | #include <mLib/mdup.h> |
6b837b22 | 51 | #include <mLib/sel.h> |
d03ab969 | 52 | #include <mLib/tv.h> |
53 | ||
54 | #include "noise.h" | |
55 | #include "paranoia.h" | |
56 | #include "rand.h" | |
57 | ||
58 | /*----- Magical numbers ---------------------------------------------------*/ | |
59 | ||
60 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ | |
61 | #define MILLION 1000000 /* One million */ | |
62 | ||
63 | /*----- Noise source definition -------------------------------------------*/ | |
64 | ||
4e66da02 | 65 | const rand_source noise_source = { noise_acquire, noise_timer }; |
d03ab969 | 66 | |
67 | /*----- Static variables --------------------------------------------------*/ | |
68 | ||
69 | /* --- Timer differences --- */ | |
70 | ||
71 | static unsigned long noise_last; /* Last time recorded */ | |
72 | static unsigned long noise_diff; /* Last first order difference */ | |
73 | ||
74 | /* --- Setuid program handling --- */ | |
75 | ||
178220b3 | 76 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
77 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ | |
d03ab969 | 78 | |
79 | /*----- Main code ---------------------------------------------------------*/ | |
80 | ||
81 | /* --- @bitcount@ --- * | |
82 | * | |
83 | * Arguments: @unsigned long x@ = a word containing bits | |
84 | * | |
85 | * Returns: The number of bits set in the word. | |
86 | */ | |
87 | ||
88 | static int bitcount(unsigned long x) | |
89 | { | |
90 | char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, | |
91 | 1, 2, 2, 3, 2, 3, 3, 4 }; | |
92 | int count = 0; | |
93 | while (x) { | |
94 | count += ctab[x & 0xfu]; | |
95 | x >>= 4; | |
96 | } | |
97 | return (count); | |
98 | } | |
99 | ||
100 | /* --- @timer@ --- * | |
101 | * | |
102 | * Arguments: @rand_pool *r@ = pointer to randomness pool | |
103 | * @struct timeval *tv@ = pointer to time block | |
104 | * | |
25f654a7 | 105 | * Returns: Nonzero if some randomness was contributed. |
d03ab969 | 106 | * |
107 | * Use: Low-level timer contributor. | |
108 | */ | |
109 | ||
110 | static int timer(rand_pool *r, struct timeval *tv) | |
111 | { | |
112 | unsigned long x, d, dd; | |
113 | int de, dde; | |
114 | int ret; | |
45c0fd36 | 115 | |
d03ab969 | 116 | x = tv->tv_usec + MILLION * tv->tv_sec; |
117 | d = x ^ noise_last; | |
118 | dd = d ^ noise_diff; | |
fc8f52d7 | 119 | noise_last = x; |
d03ab969 | 120 | noise_diff = d; |
121 | de = bitcount(d); | |
122 | dde = bitcount(dd); | |
123 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); | |
124 | ret = (de || dde); | |
125 | BURN(tv); x = d = dd = de = dde = 0; | |
126 | return (ret); | |
127 | } | |
128 | ||
129 | /* --- @noise_timer@ --- * | |
130 | * | |
131 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
132 | * | |
133 | * Returns: Nonzero if some randomness was contributed. | |
134 | * | |
135 | * Use: Contributes the current time to the randomness pool. | |
136 | * A guess at the number of useful bits contributed is made, | |
137 | * based on first and second order bit differences. This isn't | |
138 | * ever-so reliable, but it's better than nothing. | |
139 | */ | |
140 | ||
141 | int noise_timer(rand_pool *r) | |
142 | { | |
143 | struct timeval tv; | |
144 | gettimeofday(&tv, 0); | |
145 | return (timer(r, &tv)); | |
146 | } | |
147 | ||
148 | /* --- @noise_devrandom@ --- * | |
149 | * | |
150 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
151 | * | |
152 | * Returns: Nonzero if some randomness was contributed. | |
153 | * | |
154 | * Use: Attempts to obtain some randomness from the system entropy | |
155 | * pool. All bits from the device are assumed to be good. | |
156 | */ | |
157 | ||
158 | int noise_devrandom(rand_pool *r) | |
159 | { | |
160 | int fd; | |
161 | octet buf[RAND_POOLSZ]; | |
162 | ssize_t len; | |
57354275 | 163 | size_t n = 0; |
d03ab969 | 164 | int ret = 0; |
165 | ||
166 | /* --- Be nice to other clients of the random device --- * | |
167 | * | |
168 | * Attempt to open the device nonblockingly. If that works, take up to | |
169 | * one bufferful and then close again. If there's no data to be read, | |
170 | * then that's tough and we go away again, on the grounds that the device | |
171 | * needs to get some more entropy from somewhere. | |
172 | */ | |
173 | ||
25f654a7 | 174 | if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
175 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || | |
176 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { | |
57354275 MW |
177 | while (n < sizeof(buf)) { |
178 | if ((len = read(fd, buf + n, sizeof(buf) - n)) <= 0) break; | |
179 | n += len; | |
d03ab969 | 180 | } |
57354275 MW |
181 | rand_add(r, buf, n, n * 8); |
182 | BURN(buf); | |
183 | if (n == sizeof(buf)) ret = 1; | |
d03ab969 | 184 | close(fd); |
185 | } | |
186 | noise_timer(r); | |
187 | return (ret); | |
188 | } | |
189 | ||
190 | /* --- @noise_setid@ --- * | |
191 | * | |
192 | * Arguments: @uid_t uid@ = uid to set | |
193 | * @gid_t gid@ = gid to set | |
194 | * | |
195 | * Returns: --- | |
196 | * | |
197 | * Use: Sets the user and group ids to be used by @noise_filter@ | |
198 | * when running child processes. This is useful to avoid | |
199 | * giving shell commands (even carefully written ones) undue | |
099355bc | 200 | * privileges. This interface is Unix-specific |
d03ab969 | 201 | */ |
202 | ||
203 | void noise_setid(uid_t uid, gid_t gid) | |
204 | { | |
205 | noise_uid = uid; | |
206 | noise_gid = gid; | |
207 | } | |
208 | ||
209 | /* --- @noise_filter@ --- * | |
210 | * | |
211 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
212 | * @int good@ = number of good bits per 1024 bits | |
213 | * @const char *c@ = shell command to run | |
214 | * | |
215 | * Returns: Nonzero if some randomness was contributed. | |
216 | * | |
217 | * Use: Attempts to execute a shell command, and dump it into the | |
218 | * randomness pool. A very rough estimate of the number of | |
219 | * good bits is made, based on the size of the command's output. | |
220 | * This function calls @waitpid@, so be careful. Before execing | |
221 | * the command, the process uid and gid are set to the values | |
222 | * given to @noise_setid@, and an attempt is made to reset the | |
223 | * list of supplementary groups. The environment passed to | |
224 | * the command has been severly lobotimized. If the command | |
225 | * fails to complete within a short time period, it is killed. | |
226 | * Paranoid use of close-on-exec flags for file descriptors is | |
227 | * recommended. | |
099355bc | 228 | * |
229 | * This interface is Unix-specific. | |
d03ab969 | 230 | */ |
231 | ||
6b837b22 MW |
232 | struct noisekid { |
233 | rand_pool *r; | |
234 | int good; | |
235 | char buf[4096]; | |
236 | int donep; | |
237 | int ret; | |
238 | }; | |
239 | ||
240 | static void kid_read(int fd, unsigned mode, void *p) | |
241 | { | |
242 | struct noisekid *nk = p; | |
243 | ssize_t sz; | |
244 | int goodbits; | |
245 | ||
246 | noise_timer(nk->r); | |
247 | if ((sz = read(fd, nk->buf, sizeof(nk->buf))) <= 0) | |
248 | nk->donep = 1; | |
249 | else { | |
250 | goodbits = (sz * nk->good) / 128; | |
251 | rand_add(nk->r, nk->buf, sz, goodbits); | |
252 | nk->ret = 1; | |
253 | } | |
254 | } | |
255 | ||
256 | static void kid_dead(struct timeval *tv, void *p) | |
257 | { struct noisekid *nk = p; nk->donep = 1; } | |
258 | ||
d03ab969 | 259 | int noise_filter(rand_pool *r, int good, const char *c) |
260 | { | |
d03ab969 | 261 | pid_t kid; |
262 | int fd[2]; | |
263 | struct timeval dead; | |
264 | int ret = 0; | |
6b837b22 MW |
265 | struct noisekid nk = { 0 }; |
266 | sel_state sel; | |
267 | sel_file sf; | |
268 | sel_timer st; | |
d03ab969 | 269 | const char *env[] = { |
270 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", | |
271 | 0 | |
272 | }; | |
273 | ||
274 | /* --- Remember when this business started --- */ | |
275 | ||
276 | gettimeofday(&dead, 0); | |
277 | timer(r, &dead); | |
278 | ||
279 | /* --- Create a pipe --- */ | |
280 | ||
281 | if (pipe(fd)) | |
282 | return (ret); | |
283 | ||
284 | /* --- Fork a child off --- */ | |
285 | ||
028b34c6 | 286 | fflush(0); |
d03ab969 | 287 | kid = fork(); |
288 | if (kid < 0) { | |
289 | close(fd[0]); | |
290 | close(fd[1]); | |
291 | return (ret); | |
292 | } | |
293 | ||
294 | /* --- Handle the child end of the deal --- */ | |
295 | ||
d03ab969 | 296 | if (kid == 0) { |
cbc993ef MW |
297 | mdup_fd mfd[3]; |
298 | int f, i = 0; | |
d03ab969 | 299 | |
300 | /* --- Set the pipe as standard output, close standard input --- */ | |
301 | ||
cbc993ef MW |
302 | if ((f = open("/dev/null", O_RDONLY)) < 0) _exit(127); |
303 | mfd[i].cur = f; mfd[i].want = 0; i++; | |
304 | mfd[i].cur = fd[1]; mfd[i].want = 1; i++; | |
305 | mfd[i].cur = f; mfd[i].want = 2; i++; | |
306 | if (mdup(mfd, i)) _exit(127); | |
d03ab969 | 307 | |
308 | /* --- Play games with uids --- */ | |
309 | ||
310 | if (noise_gid != NOISE_NOSETGID) { | |
311 | setgid(noise_gid); | |
312 | setegid(noise_gid); | |
313 | #ifdef HAVE_SETGROUPS | |
314 | setgroups(1, &noise_gid); | |
315 | #endif | |
316 | } | |
317 | ||
318 | if (noise_uid != NOISE_NOSETUID) { | |
319 | setuid(noise_uid); | |
320 | seteuid(noise_uid); | |
321 | } | |
322 | ||
323 | /* --- Start the process up --- */ | |
324 | ||
65e14862 | 325 | execle("/bin/sh", "sh", "-c", c, (char *)0, env); |
d03ab969 | 326 | _exit(127); |
327 | } | |
328 | ||
329 | /* --- Sort out my end of the deal --- */ | |
330 | ||
331 | close(fd[1]); | |
6b837b22 MW |
332 | sel_init(&sel); |
333 | nk.r = r; nk.good = good; | |
d03ab969 | 334 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); |
6b837b22 MW |
335 | sel_initfile(&sel, &sf, fd[0], SEL_READ, kid_read, &nk); |
336 | sel_addfile(&sf); | |
337 | sel_addtimer(&sel, &st, &dead, kid_dead, &nk); | |
338 | while (!nk.donep && !sel_select(&sel)); | |
d03ab969 | 339 | |
340 | /* --- We've finished with it: kill the child process --- * | |
341 | * | |
342 | * This is morally questionable. On the other hand, I don't want to be | |
343 | * held up in the @waitpid@ call if I can possibly help it. Maybe a | |
344 | * double-fork is worth doing here. | |
345 | */ | |
346 | ||
347 | close(fd[0]); | |
6b837b22 | 348 | BURN(nk.buf); |
d03ab969 | 349 | noise_timer(r); |
350 | kill(kid, SIGKILL); | |
351 | waitpid(kid, 0, 0); | |
6b837b22 | 352 | return (nk.ret); |
d03ab969 | 353 | } |
354 | ||
25f654a7 | 355 | /* --- @noise_freewheel@ --- * |
356 | * | |
357 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
358 | * | |
359 | * Returns: Nonzero if some randomness was contributed. | |
360 | * | |
361 | * Use: Runs a free counter for a short while as a desparate attempt | |
362 | * to get randomness from somewhere. This is actually quite | |
363 | * effective. | |
364 | */ | |
365 | ||
366 | #ifdef USE_FREEWHEEL | |
367 | ||
3a5a9d7d | 368 | static sigjmp_buf fwjmp; |
25f654a7 | 369 | |
370 | static void fwalarm(int sig) | |
371 | { | |
372 | siglongjmp(fwjmp, 1); | |
373 | } | |
374 | ||
375 | int noise_freewheel(rand_pool *r) | |
376 | { | |
377 | void (*sigal)(int) = 0; | |
378 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; | |
379 | int rc = 0; | |
380 | volatile uint32 fwcount = 0; | |
381 | ||
382 | if (!sigsetjmp(fwjmp, 1)) { | |
383 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) | |
384 | return (0); | |
385 | if (setitimer(ITIMER_REAL, &itv, &oitv)) | |
386 | goto done; | |
387 | for (;;) | |
388 | fwcount++; | |
389 | } else { | |
390 | octet buf[4]; | |
391 | STORE32(buf, fwcount); | |
392 | rand_add(r, buf, sizeof(buf), 16); | |
393 | rc = 1; | |
394 | } | |
395 | ||
396 | done: | |
397 | signal(SIGALRM, sigal); | |
ff98dc94 MW |
398 | if (oitv.it_value.tv_sec || oitv.it_value.tv_usec) |
399 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); | |
25f654a7 | 400 | setitimer(ITIMER_REAL, &oitv, 0); |
401 | return (rc); | |
402 | } | |
403 | ||
404 | #else | |
405 | ||
406 | int noise_freewheel(rand_pool *r) | |
407 | { | |
408 | return (0); | |
409 | } | |
410 | ||
411 | #endif | |
412 | ||
413 | /* --- @noise_enquire@ --- * | |
414 | * | |
415 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
416 | * | |
417 | * Returns: Nonzero if some randomness was contributed. | |
418 | * | |
419 | * Use: Runs some shell commands to enquire about the prevailing | |
420 | * environment. This can gather quite a lot of low-quality | |
421 | * entropy. | |
422 | */ | |
423 | ||
424 | int noise_enquire(rand_pool *r) | |
425 | { | |
426 | struct tab { | |
427 | const char *cmd; | |
428 | unsigned rate; | |
429 | } tab[] = { | |
430 | { "ps alxww || ps -elf", 16 }, | |
431 | { "netstat -n", 6 }, | |
4108c8d2 | 432 | { "ifconfig -a", 8 }, |
25f654a7 | 433 | { "df", 20 }, |
434 | { "w", 6 }, | |
435 | { "ls -align /tmp/.", 10 }, | |
436 | { 0, 0 } | |
437 | }; | |
438 | int i; | |
439 | ||
440 | for (i = 0; tab[i].cmd; i++) | |
441 | noise_filter(r, tab[i].rate, tab[i].cmd); | |
442 | return (1); | |
443 | } | |
444 | ||
d03ab969 | 445 | /* --- @noise_acquire@ --- * |
446 | * | |
447 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
448 | * | |
449 | * Returns: --- | |
450 | * | |
451 | * Use: Acquires some randomness from somewhere. | |
452 | */ | |
453 | ||
454 | void noise_acquire(rand_pool *r) | |
455 | { | |
25f654a7 | 456 | unsigned i; |
457 | for (i = 0; i < 8; i++) | |
458 | noise_freewheel(r); | |
df40b082 | 459 | if (!noise_devrandom(r) || getenv("CATACOMB_FORCE_ESOTERIC_SOURCES")) { |
25f654a7 | 460 | noise_enquire(r); |
461 | for (i = 0; i < 8; i++) | |
462 | noise_freewheel(r); | |
d03ab969 | 463 | } |
464 | } | |
465 | ||
466 | /*----- That's all, folks -------------------------------------------------*/ |