2 * Copyright (c) 2000 Damien Miller. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 * must display the following acknowledgement:
14 * This product includes software developed by Markus Friedl.
15 * 4. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 #include <openssl/rand.h>
36 #include <openssl/sha.h>
38 /* SunOS 4.4.4 needs this */
39 #ifdef HAVE_FLOATINGPOINT_H
40 # include <floatingpoint.h>
41 #endif /* HAVE_FLOATINGPOINT_H */
46 # define offsetof(type, member) ((size_t) &((type *)0)->member)
49 /* Print lots of detail */
50 /* #define DEBUG_ENTROPY */
52 /* Number of times to pass through command list gathering entropy */
53 #define NUM_ENTROPY_RUNS 1
55 /* Scale entropy estimates back by this amount on subsequent runs */
56 #define SCALE_PER_RUN 10.0
58 /* Minimum number of commands to be considered valid */
59 #define MIN_ENTROPY_SOURCES 16
61 #define WHITESPACE " \t\n"
64 # define RUSAGE_SELF 0
66 #ifndef RUSAGE_CHILDREN
67 # define RUSAGE_CHILDREN 0
70 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
73 /* Collect entropy from EGD */
74 int get_random_bytes(unsigned char *buf, int len)
78 struct sockaddr_un addr;
82 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
83 fatal("Random pool path is too long");
85 fatal("Too many bytes to read from EGD");
87 memset(&addr, '\0', sizeof(addr));
88 addr.sun_family = AF_UNIX;
89 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
90 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
92 fd = socket(AF_UNIX, SOCK_STREAM, 0);
94 error("Couldn't create AF_UNIX socket: %s", strerror(errno));
98 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
99 error("Couldn't connect to EGD socket \"%s\": %s",
100 addr.sun_path, strerror(errno));
105 /* Send blocking read request to EGD */
109 if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
110 error("Couldn't write to EGD socket \"%s\": %s",
111 EGD_SOCKET, strerror(errno));
116 if (atomicio(read, fd, buf, len) != len) {
117 error("Couldn't read from EGD socket \"%s\": %s",
118 EGD_SOCKET, strerror(errno));
127 #else /* !EGD_SOCKET */
129 /* Collect entropy from /dev/urandom or pipe */
130 int get_random_bytes(unsigned char *buf, int len)
134 random_pool = open(RANDOM_POOL, O_RDONLY);
135 if (random_pool == -1) {
136 error("Couldn't open random pool \"%s\": %s",
137 RANDOM_POOL, strerror(errno));
141 if (atomicio(read, random_pool, buf, len) != len) {
142 error("Couldn't read from random pool \"%s\": %s",
143 RANDOM_POOL, strerror(errno));
152 #endif /* RANDOM_POOL */
153 #endif /* EGD_SOCKET */
156 * Seed OpenSSL's random number pool from Kernel random number generator
164 debug("Seeding random number generator");
166 if (!get_random_bytes(buf, sizeof(buf))) {
168 fatal("Entropy collection failed and entropy exhausted");
170 RAND_add(buf, sizeof(buf), sizeof(buf));
173 memset(buf, '\0', sizeof(buf));
177 void init_rng(void) {}
179 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
182 * FIXME: proper entropy estimations. All current values are guesses
183 * FIXME: (ATL) do estimates at compile time?
184 * FIXME: More entropy sources
187 /* slow command timeouts (all in milliseconds) */
188 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
189 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
191 static int prng_seed_saved = 0;
192 static int prng_initialised = 0;
197 /* Proportion of data that is entropy */
199 /* Counter goes positive if this command times out */
200 unsigned int badness;
201 /* Increases by factor of two each timeout */
202 unsigned int sticky_badness;
203 /* Path to executable */
205 /* argv to pass to executable */
207 /* full command string (debug) */
211 double stir_from_system(void);
212 double stir_from_programs(void);
213 double stir_gettimeofday(double entropy_estimate);
214 double stir_clock(double entropy_estimate);
215 double stir_rusage(int who, double entropy_estimate);
216 double hash_output_from_command(entropy_source_t *src, char *hash);
218 /* this is initialised from a file, by prng_read_commands() */
219 entropy_source_t *entropy_sources = NULL;
222 stir_from_system(void)
224 double total_entropy_estimate;
227 total_entropy_estimate = 0;
230 RAND_add(&i, sizeof(i), 0.5);
231 total_entropy_estimate += 0.1;
234 RAND_add(&i, sizeof(i), 0.5);
235 total_entropy_estimate += 0.1;
238 RAND_add(&i, sizeof(i), 0.0);
240 RAND_add(&i, sizeof(i), 0.0);
242 total_entropy_estimate += stir_gettimeofday(1.0);
243 total_entropy_estimate += stir_clock(0.5);
244 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
246 return(total_entropy_estimate);
250 stir_from_programs(void)
254 double entropy_estimate;
255 double total_entropy_estimate;
256 char hash[SHA_DIGEST_LENGTH];
258 total_entropy_estimate = 0;
259 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
261 while (entropy_sources[c].path != NULL) {
263 if (!entropy_sources[c].badness) {
264 /* Hash output from command */
265 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
267 /* Scale back entropy estimate according to command's rate */
268 entropy_estimate *= entropy_sources[c].rate;
270 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
271 if (entropy_estimate > SHA_DIGEST_LENGTH)
272 entropy_estimate = SHA_DIGEST_LENGTH;
274 /* Scale back estimates for subsequent passes through list */
275 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
278 RAND_add(hash, sizeof(hash), entropy_estimate);
281 debug("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
282 entropy_sources[c].cmdstring);
285 total_entropy_estimate += entropy_estimate;
287 /* Execution times should be a little unpredictable */
288 total_entropy_estimate += stir_gettimeofday(0.05);
289 total_entropy_estimate += stir_clock(0.05);
290 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
291 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
294 debug("Command '%s' disabled (badness %d)",
295 entropy_sources[c].cmdstring, entropy_sources[c].badness);
298 if (entropy_sources[c].badness > 0)
299 entropy_sources[c].badness--;
306 return(total_entropy_estimate);
310 stir_gettimeofday(double entropy_estimate)
314 if (gettimeofday(&tv, NULL) == -1)
315 fatal("Couldn't gettimeofday: %s", strerror(errno));
317 RAND_add(&tv, sizeof(tv), entropy_estimate);
319 return(entropy_estimate);
323 stir_clock(double entropy_estimate)
329 RAND_add(&c, sizeof(c), entropy_estimate);
331 return(entropy_estimate);
332 #else /* _HAVE_CLOCK */
334 #endif /* _HAVE_CLOCK */
338 stir_rusage(int who, double entropy_estimate)
340 #ifdef HAVE_GETRUSAGE
343 if (getrusage(who, &ru) == -1)
346 RAND_add(&ru, sizeof(ru), entropy_estimate);
348 return(entropy_estimate);
349 #else /* _HAVE_GETRUSAGE */
351 #endif /* _HAVE_GETRUSAGE */
357 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
358 int secdiff, usecdiff;
360 secdiff = t2->tv_sec - t1->tv_sec;
361 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
362 return (int)(usecdiff / 1000);
366 hash_output_from_command(entropy_source_t *src, char *hash)
368 static int devnull = -1;
371 int cmd_eof = 0, error_abort = 0;
372 struct timeval tv_start, tv_current;
373 int msec_elapsed = 0;
378 int total_bytes_read;
382 devnull = open("/dev/null", O_RDWR);
384 fatal("Couldn't open /dev/null: %s", strerror(errno));
388 fatal("Couldn't open pipe: %s", strerror(errno));
390 (void)gettimeofday(&tv_start, NULL); /* record start time */
392 switch (pid = fork()) {
396 fatal("Couldn't fork: %s", strerror(errno));
399 dup2(devnull, STDIN_FILENO);
400 dup2(p[1], STDOUT_FILENO);
401 dup2(p[1], STDERR_FILENO);
406 setuid(original_uid);
407 execv(src->path, (char**)(src->args));
408 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
411 default: /* Parent */
415 RAND_add(&pid, sizeof(&pid), 0.0);
419 /* Hash output from child */
421 total_bytes_read = 0;
423 while (!error_abort && !cmd_eof) {
428 (void) gettimeofday(&tv_current, 0);
429 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
430 if (msec_elapsed >= entropy_timeout_current) {
434 msec_remaining = entropy_timeout_current - msec_elapsed;
437 FD_SET(p[0], &rdset);
438 tv.tv_sec = msec_remaining / 1000;
439 tv.tv_usec = (msec_remaining % 1000) * 1000;
441 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
443 RAND_add(&tv, sizeof(tv), 0.0);
452 bytes_read = read(p[0], buf, sizeof(buf));
453 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
454 if (bytes_read == -1) {
457 } else if (bytes_read) {
458 SHA1_Update(&sha, buf, bytes_read);
459 total_bytes_read += bytes_read;
467 debug("Command '%s': select() failed: %s", src->cmdstring,
474 SHA1_Final(hash, &sha);
479 debug("Time elapsed: %d msec", msec_elapsed);
482 if (waitpid(pid, &status, 0) == -1) {
483 debug("Couldn't wait for child '%s' completion: %s", src->cmdstring,
488 RAND_add(&status, sizeof(&status), 0.0);
491 /* closing p[0] on timeout causes the entropy command to
492 * SIGPIPE. Take whatever output we got, and mark this command
494 debug("Command '%s' timed out", src->cmdstring);
495 src->sticky_badness *= 2;
496 src->badness = src->sticky_badness;
497 return(total_bytes_read);
500 if (WIFEXITED(status)) {
501 if (WEXITSTATUS(status)==0) {
502 return(total_bytes_read);
504 debug("Command '%s' exit status was %d", src->cmdstring,
505 WEXITSTATUS(status));
506 src->badness = src->sticky_badness = 128;
509 } else if (WIFSIGNALED(status)) {
510 debug("Command '%s' returned on uncaught signal %d !", src->cmdstring,
512 src->badness = src->sticky_badness = 128;
519 * prng seedfile functions
522 prng_check_seedfile(char *filename) {
526 /* FIXME raceable: eg replace seed between this stat and subsequent open */
527 /* Not such a problem because we don't trust the seed file anyway */
528 if (lstat(filename, &st) == -1) {
529 /* Fail on hard errors */
531 fatal("Couldn't stat random seed file \"%s\": %s", filename,
538 if (!S_ISREG(st.st_mode))
539 fatal("PRNG seedfile %.100s is not a regular file", filename);
541 /* mode 0600, owned by root or the current user? */
542 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid))
543 fatal("PRNG seedfile %.100s must be mode 0600, owned by uid %d",
550 prng_write_seedfile(void) {
556 /* Don't bother if we have already saved a seed */
560 setuid(original_uid);
564 pw = getpwuid(original_uid);
566 fatal("Couldn't get password entry for current user (%i): %s",
567 original_uid, strerror(errno));
569 /* Try to ensure that the parent directory is there */
570 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
572 mkdir(filename, 0700);
574 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
577 debug("writing PRNG seed to file %.100s", filename);
579 RAND_bytes(seed, sizeof(seed));
581 /* Don't care if the seed doesn't exist */
582 prng_check_seedfile(filename);
584 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1)
585 fatal("couldn't access PRNG seedfile %.100s (%.100s)", filename,
588 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
589 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
596 prng_read_seedfile(void) {
602 pw = getpwuid(original_uid);
604 fatal("Couldn't get password entry for current user (%i): %s",
605 original_uid, strerror(errno));
607 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
610 debug("loading PRNG seed from file %.100s", filename);
612 if (!prng_check_seedfile(filename)) {
613 verbose("Random seed file not found, creating new");
614 prng_write_seedfile();
616 /* Reseed immediatly */
617 (void)stir_from_system();
618 (void)stir_from_programs();
622 /* open the file and read in the seed */
623 fd = open(filename, O_RDONLY);
625 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
628 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
629 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
631 memset(seed, '\0', sizeof(seed));
635 /* stir in the seed, with estimated entropy zero */
636 RAND_add(&seed, sizeof(seed), 0.0);
641 * entropy command initialisation functions
644 prng_read_commands(char *cmdfilename)
655 entropy_source_t *entcmd;
657 f = fopen(cmdfilename, "r");
659 fatal("couldn't read entropy commands file %.100s: %.100s",
660 cmdfilename, strerror(errno));
663 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
664 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
668 while (fgets(line, sizeof(line), f)) {
674 /* skip leading whitespace, test for blank line or comment */
675 cp = line + strspn(line, WHITESPACE);
676 if ((*cp == 0) || (*cp == '#'))
677 continue; /* done with this line */
679 /* First non-whitespace char should be double quote delimiting */
682 error("bad entropy command, %.100s line %d", cmdfilename,
687 /* first token, command args (incl. argv[0]) in double quotes */
688 cp = strtok(cp, "\"");
690 error("missing or bad command string, %.100s line %d -- ignored",
691 cmdfilename, linenum);
694 strlcpy(cmd, cp, sizeof(cmd));
696 /* second token, full command path */
697 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
698 error("missing command path, %.100s line %d -- ignored",
699 cmdfilename, linenum);
703 /* did configure mark this as dead? */
704 if (strncmp("undef", cp, 5) == 0)
707 strlcpy(path, cp, sizeof(path));
709 /* third token, entropy rate estimate for this command */
710 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
711 error("missing entropy estimate, %.100s line %d -- ignored",
712 cmdfilename, linenum);
715 est = strtod(cp, &argv);
718 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
719 error("garbage at end of line %d in %.100s -- ignored", linenum,
724 /* save the command for debug messages */
725 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
727 /* split the command args */
728 cp = strtok(cmd, WHITESPACE);
732 char *s = (char*)xmalloc(strlen(cp) + 1);
733 strncpy(s, cp, strlen(cp) + 1);
734 entcmd[cur_cmd].args[arg] = s;
736 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
738 if (strtok(NULL, WHITESPACE))
739 error("ignored extra command elements (max 5), %.100s line %d",
740 cmdfilename, linenum);
742 /* Copy the command path and rate estimate */
743 entcmd[cur_cmd].path = xstrdup(path);
744 entcmd[cur_cmd].rate = est;
746 /* Initialise other values */
747 entcmd[cur_cmd].sticky_badness = 1;
751 /* If we've filled the array, reallocate it twice the size */
752 /* Do this now because even if this we're on the last command,
753 we need another slot to mark the last entry */
754 if (cur_cmd == num_cmds) {
756 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
760 /* zero the last entry */
761 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
764 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
766 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
768 return (cur_cmd >= MIN_ENTROPY_SOURCES);
772 * Write a keyfile at exit
775 prng_seed_cleanup(void *junk)
777 prng_write_seedfile();
781 * Conditionally Seed OpenSSL's random number pool from
782 * syscalls and program output
787 void *old_sigchld_handler;
789 if (!prng_initialised)
790 fatal("RNG not initialised");
792 /* Make sure some other sigchld handler doesn't reap our entropy */
794 old_sigchld_handler = signal(SIGCHLD, SIG_DFL);
796 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
797 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
800 fatal("Not enough entropy in RNG");
802 signal(SIGCHLD, old_sigchld_handler);
805 fatal("Couldn't initialise builtin random number generator -- exiting.");
810 original_uid = getuid();
812 /* Read in collection commands */
813 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
814 fatal("PRNG initialisation failed -- exiting.");
816 /* Set ourselves up to save a seed upon exit */
818 prng_read_seedfile();
819 fatal_add_cleanup(prng_seed_cleanup, NULL);
820 atexit(prng_write_seedfile);
822 prng_initialised = 1;
825 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */