3 * Acquisition of environmental noise (Unix-specific)
5 * (c) 1998 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
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.
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.
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,
28 /*----- Header files ------------------------------------------------------*/
38 #include <sys/types.h>
49 #include <mLib/bits.h>
50 #include <mLib/mdup.h>
57 /*----- Magical numbers ---------------------------------------------------*/
59 #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */
60 #define MILLION 1000000 /* One million */
62 /*----- Noise source definition -------------------------------------------*/
64 const rand_source noise_source = { noise_acquire, noise_timer };
66 /*----- Static variables --------------------------------------------------*/
68 /* --- Timer differences --- */
70 static unsigned long noise_last; /* Last time recorded */
71 static unsigned long noise_diff; /* Last first order difference */
73 /* --- Setuid program handling --- */
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 */
78 /*----- Main code ---------------------------------------------------------*/
80 /* --- @bitcount@ --- *
82 * Arguments: @unsigned long x@ = a word containing bits
84 * Returns: The number of bits set in the word.
87 static int bitcount(unsigned long x)
89 char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3,
90 1, 2, 2, 3, 2, 3, 3, 4 };
93 count += ctab[x & 0xfu];
101 * Arguments: @rand_pool *r@ = pointer to randomness pool
102 * @struct timeval *tv@ = pointer to time block
104 * Returns: Nonzero if some randomness was contributed.
106 * Use: Low-level timer contributor.
109 static int timer(rand_pool *r, struct timeval *tv)
111 unsigned long x, d, dd;
115 x = tv->tv_usec + MILLION * tv->tv_sec;
122 rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde);
124 BURN(tv); x = d = dd = de = dde = 0;
128 /* --- @noise_timer@ --- *
130 * Arguments: @rand_pool *r@ = pointer to a randomness pool
132 * Returns: Nonzero if some randomness was contributed.
134 * Use: Contributes the current time to the randomness pool.
135 * A guess at the number of useful bits contributed is made,
136 * based on first and second order bit differences. This isn't
137 * ever-so reliable, but it's better than nothing.
140 int noise_timer(rand_pool *r)
143 gettimeofday(&tv, 0);
144 return (timer(r, &tv));
147 /* --- @noise_devrandom@ --- *
149 * Arguments: @rand_pool *r@ = pointer to a randomness pool
151 * Returns: Nonzero if some randomness was contributed.
153 * Use: Attempts to obtain some randomness from the system entropy
154 * pool. All bits from the device are assumed to be good.
157 int noise_devrandom(rand_pool *r)
160 octet buf[RAND_POOLSZ];
165 /* --- Be nice to other clients of the random device --- *
167 * Attempt to open the device nonblockingly. If that works, take up to
168 * one bufferful and then close again. If there's no data to be read,
169 * then that's tough and we go away again, on the grounds that the device
170 * needs to get some more entropy from somewhere.
173 if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
174 (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
175 (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) {
176 while (n < sizeof(buf)) {
177 if ((len = read(fd, buf + n, sizeof(buf) - n)) <= 0) break;
180 rand_add(r, buf, n, n * 8);
182 if (n == sizeof(buf)) ret = 1;
189 /* --- @noise_setid@ --- *
191 * Arguments: @uid_t uid@ = uid to set
192 * @gid_t gid@ = gid to set
196 * Use: Sets the user and group ids to be used by @noise_filter@
197 * when running child processes. This is useful to avoid
198 * giving shell commands (even carefully written ones) undue
199 * privileges. This interface is Unix-specific
202 void noise_setid(uid_t uid, gid_t gid)
208 /* --- @noise_filter@ --- *
210 * Arguments: @rand_pool *r@ = pointer to a randomness pool
211 * @int good@ = number of good bits per 1024 bits
212 * @const char *c@ = shell command to run
214 * Returns: Nonzero if some randomness was contributed.
216 * Use: Attempts to execute a shell command, and dump it into the
217 * randomness pool. A very rough estimate of the number of
218 * good bits is made, based on the size of the command's output.
219 * This function calls @waitpid@, so be careful. Before execing
220 * the command, the process uid and gid are set to the values
221 * given to @noise_setid@, and an attempt is made to reset the
222 * list of supplementary groups. The environment passed to
223 * the command has been severly lobotimized. If the command
224 * fails to complete within a short time period, it is killed.
225 * Paranoid use of close-on-exec flags for file descriptors is
228 * This interface is Unix-specific.
231 int noise_filter(rand_pool *r, int good, const char *c)
238 const char *env[] = {
239 "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc",
243 /* --- Remember when this business started --- */
245 gettimeofday(&dead, 0);
248 /* --- Create a pipe --- */
253 /* --- Fork a child off --- */
263 /* --- Handle the child end of the deal --- */
269 /* --- Set the pipe as standard output, close standard input --- */
271 if ((f = open("/dev/null", O_RDONLY)) < 0) _exit(127);
272 mfd[i].cur = f; mfd[i].want = 0; i++;
273 mfd[i].cur = fd[1]; mfd[i].want = 1; i++;
274 mfd[i].cur = f; mfd[i].want = 2; i++;
275 if (mdup(mfd, i)) _exit(127);
277 /* --- Play games with uids --- */
279 if (noise_gid != NOISE_NOSETGID) {
282 #ifdef HAVE_SETGROUPS
283 setgroups(1, &noise_gid);
287 if (noise_uid != NOISE_NOSETUID) {
292 /* --- Start the process up --- */
294 execle("/bin/sh", "sh", "-c", c, (char *)0, env);
298 /* --- Sort out my end of the deal --- */
302 /* --- Decide on the deadline --- */
304 TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE);
306 /* --- Now read, and think --- */
309 struct timeval now, diff;
312 gettimeofday(&now, 0);
314 if (TV_CMP(&now, >, &dead))
316 TV_SUB(&diff, &dead, &now);
321 if (select(fd[0] + 1, &rd, 0, 0, &diff) < 0)
323 if (FD_ISSET(fd[0], &rd)) {
327 if ((sz = read(fd[0], buf, sizeof(buf))) <= 0)
329 goodbits = (sz * good) / 128;
330 rand_add(r, buf, sz, goodbits);
335 /* --- We've finished with it: kill the child process --- *
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.
350 /* --- @noise_freewheel@ --- *
352 * Arguments: @rand_pool *r@ = pointer to a randomness pool
354 * Returns: Nonzero if some randomness was contributed.
356 * Use: Runs a free counter for a short while as a desparate attempt
357 * to get randomness from somewhere. This is actually quite
363 static jmp_buf fwjmp;
365 static void fwalarm(int sig)
367 siglongjmp(fwjmp, 1);
370 int noise_freewheel(rand_pool *r)
372 void (*sigal)(int) = 0;
373 struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } };
375 volatile uint32 fwcount = 0;
377 if (!sigsetjmp(fwjmp, 1)) {
378 if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR)
380 if (setitimer(ITIMER_REAL, &itv, &oitv))
386 STORE32(buf, fwcount);
387 rand_add(r, buf, sizeof(buf), 16);
392 signal(SIGALRM, sigal);
393 if (oitv.it_value.tv_sec || oitv.it_value.tv_usec)
394 TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value);
395 setitimer(ITIMER_REAL, &oitv, 0);
401 int noise_freewheel(rand_pool *r)
408 /* --- @noise_enquire@ --- *
410 * Arguments: @rand_pool *r@ = pointer to a randomness pool
412 * Returns: Nonzero if some randomness was contributed.
414 * Use: Runs some shell commands to enquire about the prevailing
415 * environment. This can gather quite a lot of low-quality
419 int noise_enquire(rand_pool *r)
425 { "ps alxww || ps -elf", 16 },
427 { "ifconfig -a", 8 },
430 { "ls -align /tmp/.", 10 },
435 for (i = 0; tab[i].cmd; i++)
436 noise_filter(r, tab[i].rate, tab[i].cmd);
440 /* --- @noise_acquire@ --- *
442 * Arguments: @rand_pool *r@ = pointer to a randomness pool
446 * Use: Acquires some randomness from somewhere.
449 void noise_acquire(rand_pool *r)
452 for (i = 0; i < 8; i++)
454 if (!noise_devrandom(r) || getenv("CATACOMB_FORCE_ESOTERIC_SOURCES")) {
456 for (i = 0; i < 8; i++)
461 /*----- That's all, folks -------------------------------------------------*/