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>
58 /*----- Magical numbers ---------------------------------------------------*/
60 #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */
61 #define MILLION 1000000 /* One million */
63 /*----- Noise source definition -------------------------------------------*/
65 const rand_source noise_source = { noise_acquire, noise_timer };
67 /*----- Static variables --------------------------------------------------*/
69 /* --- Timer differences --- */
71 static unsigned long noise_last; /* Last time recorded */
72 static unsigned long noise_diff; /* Last first order difference */
74 /* --- Setuid program handling --- */
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 */
79 /*----- Main code ---------------------------------------------------------*/
81 /* --- @bitcount@ --- *
83 * Arguments: @unsigned long x@ = a word containing bits
85 * Returns: The number of bits set in the word.
88 static int bitcount(unsigned long x)
90 static const char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3,
91 1, 2, 2, 3, 2, 3, 3, 4 };
94 count += ctab[x & 0xfu];
102 * Arguments: @rand_pool *r@ = pointer to randomness pool
103 * @struct timeval *tv@ = pointer to time block
105 * Returns: Nonzero if some randomness was contributed.
107 * Use: Low-level timer contributor.
110 static int timer(rand_pool *r, struct timeval *tv)
112 unsigned long x, d, dd;
116 x = tv->tv_usec + MILLION * tv->tv_sec;
123 rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde);
125 BURN(tv); x = d = dd = de = dde = 0;
129 /* --- @noise_timer@ --- *
131 * Arguments: @rand_pool *r@ = pointer to a randomness pool
133 * Returns: Nonzero if some randomness was contributed.
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.
141 int noise_timer(rand_pool *r)
144 gettimeofday(&tv, 0);
145 return (timer(r, &tv));
148 /* --- @noise_devrandom@ --- *
150 * Arguments: @rand_pool *r@ = pointer to a randomness pool
152 * Returns: Nonzero if some randomness was contributed.
154 * Use: Attempts to obtain some randomness from the system entropy
155 * pool. All bits from the device are assumed to be good.
158 int noise_devrandom(rand_pool *r)
161 octet buf[RAND_POOLSZ];
166 /* --- Be nice to other clients of the random device --- *
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.
175 (fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
176 (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
177 (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) {
178 while (n < sizeof(buf)) {
179 if ((len = read(fd, buf + n, sizeof(buf) - n)) <= 0) break;
182 if (n == sizeof(buf)) goto win;
189 if (fd >= 0) close(fd);
190 rand_add(r, buf, n, 8*n);
196 /* --- @noise_setid@ --- *
198 * Arguments: @uid_t uid@ = uid to set
199 * @gid_t gid@ = gid to set
203 * Use: Sets the user and group ids to be used by @noise_filter@
204 * when running child processes. This is useful to avoid
205 * giving shell commands (even carefully written ones) undue
206 * privileges. This interface is Unix-specific
209 void noise_setid(uid_t uid, gid_t gid)
215 /* --- @noise_filter@ --- *
217 * Arguments: @rand_pool *r@ = pointer to a randomness pool
218 * @int good@ = number of good bits per 1024 bits
219 * @const char *c@ = shell command to run
221 * Returns: Nonzero if some randomness was contributed.
223 * Use: Attempts to execute a shell command, and dump it into the
224 * randomness pool. A very rough estimate of the number of
225 * good bits is made, based on the size of the command's output.
226 * This function calls @waitpid@, so be careful. Before execing
227 * the command, the process uid and gid are set to the values
228 * given to @noise_setid@, and an attempt is made to reset the
229 * list of supplementary groups. The environment passed to
230 * the command has been severly lobotimized. If the command
231 * fails to complete within a short time period, it is killed.
232 * Paranoid use of close-on-exec flags for file descriptors is
235 * This interface is Unix-specific.
246 static void kid_read(int fd, unsigned mode, void *p)
248 struct noisekid *nk = p;
253 if ((sz = read(fd, nk->buf, sizeof(nk->buf))) <= 0)
256 goodbits = (sz * nk->good) / 128;
257 rand_add(nk->r, nk->buf, sz, goodbits);
262 static void kid_dead(struct timeval *tv, void *p)
263 { struct noisekid *nk = p; nk->donep = 1; }
265 int noise_filter(rand_pool *r, int good, const char *c)
271 struct noisekid nk = { 0 };
275 const char *env[] = {
276 "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc",
280 /* --- Remember when this business started --- */
282 gettimeofday(&dead, 0);
285 /* --- Create a pipe --- */
290 /* --- Fork a child off --- */
300 /* --- Handle the child end of the deal --- */
306 /* --- Set the pipe as standard output, close standard input --- */
308 if ((f = open("/dev/null", O_RDONLY)) < 0) _exit(127);
309 mfd[i].cur = f; mfd[i].want = 0; i++;
310 mfd[i].cur = fd[1]; mfd[i].want = 1; i++;
311 mfd[i].cur = f; mfd[i].want = 2; i++;
312 if (mdup(mfd, i)) _exit(127);
314 /* --- Play games with uids --- */
316 if (noise_gid != NOISE_NOSETGID) {
319 #ifdef HAVE_SETGROUPS
320 setgroups(1, &noise_gid);
324 if (noise_uid != NOISE_NOSETUID) {
329 /* --- Start the process up --- */
331 execle("/bin/sh", "sh", "-c", c, (char *)0, env);
335 /* --- Sort out my end of the deal --- */
339 nk.r = r; nk.good = good;
340 TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE);
341 sel_initfile(&sel, &sf, fd[0], SEL_READ, kid_read, &nk);
343 sel_addtimer(&sel, &st, &dead, kid_dead, &nk);
344 while (!nk.donep && !sel_select(&sel));
346 /* --- We've finished with it: kill the child process --- *
348 * This is morally questionable. On the other hand, I don't want to be
349 * held up in the @waitpid@ call if I can possibly help it. Maybe a
350 * double-fork is worth doing here.
361 /* --- @noise_freewheel@ --- *
363 * Arguments: @rand_pool *r@ = pointer to a randomness pool
365 * Returns: Nonzero if some randomness was contributed.
367 * Use: Runs a free counter for a short while as a desparate attempt
368 * to get randomness from somewhere. This is actually quite
374 static sigjmp_buf fwjmp;
376 static void fwalarm(int sig)
378 siglongjmp(fwjmp, 1);
381 int noise_freewheel(rand_pool *r)
383 void (*sigal)(int) = 0;
384 struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } };
386 volatile uint32 fwcount = 0;
388 if (!sigsetjmp(fwjmp, 1)) {
389 if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR)
391 if (setitimer(ITIMER_REAL, &itv, &oitv))
397 STORE32(buf, fwcount);
398 rand_add(r, buf, sizeof(buf), 16);
403 signal(SIGALRM, sigal);
404 if (oitv.it_value.tv_sec || oitv.it_value.tv_usec)
405 TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value);
406 setitimer(ITIMER_REAL, &oitv, 0);
412 int noise_freewheel(rand_pool *r)
419 /* --- @noise_enquire@ --- *
421 * Arguments: @rand_pool *r@ = pointer to a randomness pool
423 * Returns: Nonzero if some randomness was contributed.
425 * Use: Runs some shell commands to enquire about the prevailing
426 * environment. This can gather quite a lot of low-quality
430 int noise_enquire(rand_pool *r)
436 { "ps alxww || ps -elf", 16 },
438 { "ifconfig -a", 8 },
441 { "ls -align /tmp/.", 10 },
446 for (i = 0; tab[i].cmd; i++)
447 noise_filter(r, tab[i].rate, tab[i].cmd);
451 /* --- @noise_acquire@ --- *
453 * Arguments: @rand_pool *r@ = pointer to a randomness pool
457 * Use: Acquires some randomness from somewhere.
460 void noise_acquire(rand_pool *r)
463 for (i = 0; i < 8; i++)
465 if (!noise_devrandom(r) || getenv("CATACOMB_FORCE_ESOTERIC_SOURCES")) {
467 for (i = 0; i < 8; i++)
472 /*----- That's all, folks -------------------------------------------------*/