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>
41 # define offsetof(type, member) ((size_t) &((type *)0)->member)
44 /* Print lots of detail */
45 /* #define DEBUG_ENTROPY */
47 /* Number of times to pass through command list gathering entropy */
48 #define NUM_ENTROPY_RUNS 1
50 /* Scale entropy estimates back by this amount on subsequent runs */
51 #define SCALE_PER_RUN 10.0
53 /* Minimum number of commands to be considered valid */
54 #define MIN_ENTROPY_SOURCES 16
56 #define WHITESPACE " \t\n"
59 # define RUSAGE_SELF 0
61 #ifndef RUSAGE_CHILDREN
62 # define RUSAGE_CHILDREN 0
65 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
68 /* Collect entropy from EGD */
69 int get_random_bytes(unsigned char *buf, int len)
73 struct sockaddr_un addr;
77 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
78 fatal("Random pool path is too long");
80 fatal("Too many bytes to read from EGD");
82 memset(&addr, '\0', sizeof(addr));
83 addr.sun_family = AF_UNIX;
84 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
85 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
87 fd = socket(AF_UNIX, SOCK_STREAM, 0);
89 error("Couldn't create AF_UNIX socket: %s", strerror(errno));
93 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
94 error("Couldn't connect to EGD socket \"%s\": %s",
95 addr.sun_path, strerror(errno));
100 /* Send blocking read request to EGD */
104 if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
105 error("Couldn't write to EGD socket \"%s\": %s",
106 EGD_SOCKET, strerror(errno));
111 if (atomicio(read, fd, buf, len) != len) {
112 error("Couldn't read from EGD socket \"%s\": %s",
113 EGD_SOCKET, strerror(errno));
122 #else /* !EGD_SOCKET */
124 /* Collect entropy from /dev/urandom or pipe */
125 int get_random_bytes(unsigned char *buf, int len)
129 random_pool = open(RANDOM_POOL, O_RDONLY);
130 if (random_pool == -1) {
131 error("Couldn't open random pool \"%s\": %s",
132 RANDOM_POOL, strerror(errno));
136 if (atomicio(read, random_pool, buf, len) != len) {
137 error("Couldn't read from random pool \"%s\": %s",
138 RANDOM_POOL, strerror(errno));
147 #endif /* RANDOM_POOL */
148 #endif /* EGD_SOCKET */
151 * Seed OpenSSL's random number pool from Kernel random number generator
159 debug("Seeding random number generator");
161 if (!get_random_bytes(buf, sizeof(buf))) {
163 fatal("Entropy collection failed and entropy exhausted");
165 RAND_add(buf, sizeof(buf), sizeof(buf));
168 memset(buf, '\0', sizeof(buf));
172 void init_rng(void) {}
174 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
177 * FIXME: proper entropy estimations. All current values are guesses
178 * FIXME: (ATL) do estimates at compile time?
179 * FIXME: More entropy sources
182 /* slow command timeouts (all in milliseconds) */
183 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
184 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
186 static int prng_seed_saved = 0;
187 static int prng_initialised = 0;
192 /* Proportion of data that is entropy */
194 /* Counter goes positive if this command times out */
195 unsigned int badness;
196 /* Increases by factor of two each timeout */
197 unsigned int sticky_badness;
198 /* Path to executable */
200 /* argv to pass to executable */
202 /* full command string (debug) */
206 double stir_from_system(void);
207 double stir_from_programs(void);
208 double stir_gettimeofday(double entropy_estimate);
209 double stir_clock(double entropy_estimate);
210 double stir_rusage(int who, double entropy_estimate);
211 double hash_output_from_command(entropy_source_t *src, char *hash);
213 /* this is initialised from a file, by prng_read_commands() */
214 entropy_source_t *entropy_sources = NULL;
217 stir_from_system(void)
219 double total_entropy_estimate;
222 total_entropy_estimate = 0;
225 RAND_add(&i, sizeof(i), 0.5);
226 total_entropy_estimate += 0.1;
229 RAND_add(&i, sizeof(i), 0.5);
230 total_entropy_estimate += 0.1;
233 RAND_add(&i, sizeof(i), 0.0);
235 RAND_add(&i, sizeof(i), 0.0);
237 total_entropy_estimate += stir_gettimeofday(1.0);
238 total_entropy_estimate += stir_clock(0.5);
239 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
241 return(total_entropy_estimate);
245 stir_from_programs(void)
249 double entropy_estimate;
250 double total_entropy_estimate;
251 char hash[SHA_DIGEST_LENGTH];
253 total_entropy_estimate = 0;
254 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
256 while (entropy_sources[c].path != NULL) {
258 if (!entropy_sources[c].badness) {
259 /* Hash output from command */
260 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
262 /* Scale back entropy estimate according to command's rate */
263 entropy_estimate *= entropy_sources[c].rate;
265 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
266 if (entropy_estimate > SHA_DIGEST_LENGTH)
267 entropy_estimate = SHA_DIGEST_LENGTH;
269 /* Scale back estimates for subsequent passes through list */
270 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
273 RAND_add(hash, sizeof(hash), entropy_estimate);
276 debug("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
277 entropy_sources[c].cmdstring);
280 total_entropy_estimate += entropy_estimate;
282 /* Execution times should be a little unpredictable */
283 total_entropy_estimate += stir_gettimeofday(0.05);
284 total_entropy_estimate += stir_clock(0.05);
285 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
286 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
289 debug("Command '%s' disabled (badness %d)",
290 entropy_sources[c].cmdstring, entropy_sources[c].badness);
293 if (entropy_sources[c].badness > 0)
294 entropy_sources[c].badness--;
301 return(total_entropy_estimate);
305 stir_gettimeofday(double entropy_estimate)
309 if (gettimeofday(&tv, NULL) == -1)
310 fatal("Couldn't gettimeofday: %s", strerror(errno));
312 RAND_add(&tv, sizeof(tv), entropy_estimate);
314 return(entropy_estimate);
318 stir_clock(double entropy_estimate)
324 RAND_add(&c, sizeof(c), entropy_estimate);
326 return(entropy_estimate);
327 #else /* _HAVE_CLOCK */
329 #endif /* _HAVE_CLOCK */
333 stir_rusage(int who, double entropy_estimate)
335 #ifdef HAVE_GETRUSAGE
338 if (getrusage(who, &ru) == -1)
341 RAND_add(&ru, sizeof(ru), entropy_estimate);
343 return(entropy_estimate);
344 #else /* _HAVE_GETRUSAGE */
346 #endif /* _HAVE_GETRUSAGE */
352 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
353 int secdiff, usecdiff;
355 secdiff = t2->tv_sec - t1->tv_sec;
356 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
357 return (int)(usecdiff / 1000);
361 hash_output_from_command(entropy_source_t *src, char *hash)
363 static int devnull = -1;
366 int cmd_eof = 0, error_abort = 0;
367 struct timeval tv_start, tv_current;
368 int msec_elapsed = 0;
373 int total_bytes_read;
377 devnull = open("/dev/null", O_RDWR);
379 fatal("Couldn't open /dev/null: %s", strerror(errno));
383 fatal("Couldn't open pipe: %s", strerror(errno));
385 (void)gettimeofday(&tv_start, NULL); /* record start time */
387 switch (pid = fork()) {
391 fatal("Couldn't fork: %s", strerror(errno));
394 dup2(devnull, STDIN_FILENO);
395 dup2(p[1], STDOUT_FILENO);
396 dup2(p[1], STDERR_FILENO);
401 setuid(original_uid);
402 execv(src->path, (char**)(src->args));
403 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
406 default: /* Parent */
410 RAND_add(&pid, sizeof(&pid), 0.0);
414 /* Hash output from child */
416 total_bytes_read = 0;
418 while (!error_abort && !cmd_eof) {
423 (void) gettimeofday(&tv_current, 0);
424 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
425 if (msec_elapsed >= entropy_timeout_current) {
429 msec_remaining = entropy_timeout_current - msec_elapsed;
432 FD_SET(p[0], &rdset);
433 tv.tv_sec = msec_remaining / 1000;
434 tv.tv_usec = (msec_remaining % 1000) * 1000;
436 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
438 RAND_add(&tv, sizeof(tv), 0.0);
447 bytes_read = read(p[0], buf, sizeof(buf));
448 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
449 if (bytes_read == -1) {
452 } else if (bytes_read) {
453 SHA1_Update(&sha, buf, bytes_read);
454 total_bytes_read += bytes_read;
462 debug("Command '%s': select() failed: %s", src->cmdstring,
469 SHA1_Final(hash, &sha);
474 debug("Time elapsed: %d msec", msec_elapsed);
477 if (waitpid(pid, &status, 0) == -1) {
478 debug("Couldn't wait for child '%s' completion: %s", src->cmdstring,
483 RAND_add(&status, sizeof(&status), 0.0);
486 /* closing p[0] on timeout causes the entropy command to
487 * SIGPIPE. Take whatever output we got, and mark this command
489 debug("Command '%s' timed out", src->cmdstring);
490 src->sticky_badness *= 2;
491 src->badness = src->sticky_badness;
492 return(total_bytes_read);
495 if (WIFEXITED(status)) {
496 if (WEXITSTATUS(status)==0) {
497 return(total_bytes_read);
499 debug("Command '%s' exit status was %d", src->cmdstring,
500 WEXITSTATUS(status));
501 src->badness = src->sticky_badness = 128;
504 } else if (WIFSIGNALED(status)) {
505 debug("Command '%s' returned on uncaught signal %d !", src->cmdstring,
507 src->badness = src->sticky_badness = 128;
514 * prng seedfile functions
517 prng_check_seedfile(char *filename) {
521 /* FIXME raceable: eg replace seed between this stat and subsequent open */
522 /* Not such a problem because we don't trust the seed file anyway */
523 if (lstat(filename, &st) == -1) {
524 /* Fail on hard errors */
526 fatal("Couldn't stat random seed file \"%s\": %s", filename,
533 if (!S_ISREG(st.st_mode))
534 fatal("PRNG seedfile %.100s is not a regular file", filename);
536 /* mode 0600, owned by root or the current user? */
537 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid))
538 fatal("PRNG seedfile %.100s must be mode 0600, owned by uid %d",
545 prng_write_seedfile(void) {
551 /* Don't bother if we have already saved a seed */
555 setuid(original_uid);
559 pw = getpwuid(original_uid);
561 fatal("Couldn't get password entry for current user (%i): %s",
562 original_uid, strerror(errno));
564 /* Try to ensure that the parent directory is there */
565 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
567 mkdir(filename, 0700);
569 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
572 debug("writing PRNG seed to file %.100s", filename);
574 RAND_bytes(seed, sizeof(seed));
576 /* Don't care if the seed doesn't exist */
577 prng_check_seedfile(filename);
579 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1)
580 fatal("couldn't access PRNG seedfile %.100s (%.100s)", filename,
583 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
584 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
591 prng_read_seedfile(void) {
597 pw = getpwuid(original_uid);
599 fatal("Couldn't get password entry for current user (%i): %s",
600 original_uid, strerror(errno));
602 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
605 debug("loading PRNG seed from file %.100s", filename);
607 if (!prng_check_seedfile(filename)) {
608 verbose("Random seed file not found, creating new");
609 prng_write_seedfile();
611 /* Reseed immediatly */
612 (void)stir_from_system();
613 (void)stir_from_programs();
617 /* open the file and read in the seed */
618 fd = open(filename, O_RDONLY);
620 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
623 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
624 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
626 memset(seed, '\0', sizeof(seed));
630 /* stir in the seed, with estimated entropy zero */
631 RAND_add(&seed, sizeof(seed), 0.0);
636 * entropy command initialisation functions
639 prng_read_commands(char *cmdfilename)
650 entropy_source_t *entcmd;
652 f = fopen(cmdfilename, "r");
654 fatal("couldn't read entropy commands file %.100s: %.100s",
655 cmdfilename, strerror(errno));
658 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
659 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
663 while (fgets(line, sizeof(line), f)) {
669 /* skip leading whitespace, test for blank line or comment */
670 cp = line + strspn(line, WHITESPACE);
671 if ((*cp == 0) || (*cp == '#'))
672 continue; /* done with this line */
674 /* First non-whitespace char should be double quote delimiting */
677 error("bad entropy command, %.100s line %d", cmdfilename,
682 /* first token, command args (incl. argv[0]) in double quotes */
683 cp = strtok(cp, "\"");
685 error("missing or bad command string, %.100s line %d -- ignored",
686 cmdfilename, linenum);
689 strlcpy(cmd, cp, sizeof(cmd));
691 /* second token, full command path */
692 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
693 error("missing command path, %.100s line %d -- ignored",
694 cmdfilename, linenum);
698 /* did configure mark this as dead? */
699 if (strncmp("undef", cp, 5) == 0)
702 strlcpy(path, cp, sizeof(path));
704 /* third token, entropy rate estimate for this command */
705 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
706 error("missing entropy estimate, %.100s line %d -- ignored",
707 cmdfilename, linenum);
710 est = strtod(cp, &argv);
713 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
714 error("garbage at end of line %d in %.100s -- ignored", linenum,
719 /* save the command for debug messages */
720 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
722 /* split the command args */
723 cp = strtok(cmd, WHITESPACE);
727 char *s = (char*)xmalloc(strlen(cp) + 1);
728 strncpy(s, cp, strlen(cp) + 1);
729 entcmd[cur_cmd].args[arg] = s;
731 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
733 if (strtok(NULL, WHITESPACE))
734 error("ignored extra command elements (max 5), %.100s line %d",
735 cmdfilename, linenum);
737 /* Copy the command path and rate estimate */
738 entcmd[cur_cmd].path = xstrdup(path);
739 entcmd[cur_cmd].rate = est;
741 /* Initialise other values */
742 entcmd[cur_cmd].sticky_badness = 1;
746 /* If we've filled the array, reallocate it twice the size */
747 /* Do this now because even if this we're on the last command,
748 we need another slot to mark the last entry */
749 if (cur_cmd == num_cmds) {
751 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
755 /* zero the last entry */
756 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
759 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
761 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
763 return (cur_cmd >= MIN_ENTROPY_SOURCES);
767 * Write a keyfile at exit
770 prng_seed_cleanup(void *junk)
772 prng_write_seedfile();
776 * Conditionally Seed OpenSSL's random number pool from
777 * syscalls and program output
782 void *old_sigchld_handler;
784 if (!prng_initialised)
785 fatal("RNG not initialised");
787 /* Make sure some other sigchld handler doesn't reap our entropy */
789 old_sigchld_handler = signal(SIGCHLD, SIG_DFL);
791 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
792 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
795 fatal("Not enough entropy in RNG");
797 signal(SIGCHLD, old_sigchld_handler);
800 fatal("Couldn't initialise builtin random number generator -- exiting.");
805 original_uid = getuid();
807 /* Read in collection commands */
808 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
809 fatal("PRNG initialisation failed -- exiting.");
811 /* Set ourselves up to save a seed upon exit */
813 prng_read_seedfile();
814 fatal_add_cleanup(prng_seed_cleanup, NULL);
815 atexit(prng_write_seedfile);
817 prng_initialised = 1;
820 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */