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.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 #include <openssl/rand.h>
28 #include <openssl/sha.h>
30 /* SunOS 4.4.4 needs this */
31 #ifdef HAVE_FLOATINGPOINT_H
32 # include <floatingpoint.h>
33 #endif /* HAVE_FLOATINGPOINT_H */
43 # define offsetof(type, member) ((size_t) &((type *)0)->member)
46 /* Number of times to pass through command list gathering entropy */
47 #define NUM_ENTROPY_RUNS 1
49 /* Scale entropy estimates back by this amount on subsequent runs */
50 #define SCALE_PER_RUN 10.0
52 /* Minimum number of commands to be considered valid */
53 #define MIN_ENTROPY_SOURCES 16
55 #define WHITESPACE " \t\n"
58 # define RUSAGE_SELF 0
60 #ifndef RUSAGE_CHILDREN
61 # define RUSAGE_CHILDREN 0
64 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
67 /* Collect entropy from EGD */
68 int get_random_bytes(unsigned char *buf, int len)
72 struct sockaddr_un addr;
76 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
77 fatal("Random pool path is too long");
79 fatal("Too many bytes to read from EGD");
81 memset(&addr, '\0', sizeof(addr));
82 addr.sun_family = AF_UNIX;
83 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
84 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
86 fd = socket(AF_UNIX, SOCK_STREAM, 0);
88 error("Couldn't create AF_UNIX socket: %s", strerror(errno));
92 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
93 error("Couldn't connect to EGD socket \"%s\": %s",
94 addr.sun_path, strerror(errno));
99 /* Send blocking read request to EGD */
103 if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
104 error("Couldn't write to EGD socket \"%s\": %s",
105 EGD_SOCKET, strerror(errno));
110 if (atomicio(read, fd, buf, len) != len) {
111 error("Couldn't read from EGD socket \"%s\": %s",
112 EGD_SOCKET, strerror(errno));
121 #else /* !EGD_SOCKET */
123 /* Collect entropy from /dev/urandom or pipe */
124 int get_random_bytes(unsigned char *buf, int len)
128 random_pool = open(RANDOM_POOL, O_RDONLY);
129 if (random_pool == -1) {
130 error("Couldn't open random pool \"%s\": %s",
131 RANDOM_POOL, strerror(errno));
135 if (atomicio(read, random_pool, buf, len) != len) {
136 error("Couldn't read from random pool \"%s\": %s",
137 RANDOM_POOL, strerror(errno));
146 #endif /* RANDOM_POOL */
147 #endif /* EGD_SOCKET */
150 * Seed OpenSSL's random number pool from Kernel random number generator
158 debug("Seeding random number generator");
160 if (!get_random_bytes(buf, sizeof(buf))) {
162 fatal("Entropy collection failed and entropy exhausted");
164 RAND_add(buf, sizeof(buf), sizeof(buf));
167 memset(buf, '\0', sizeof(buf));
171 void init_rng(void) {}
173 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
176 * FIXME: proper entropy estimations. All current values are guesses
177 * FIXME: (ATL) do estimates at compile time?
178 * FIXME: More entropy sources
181 /* slow command timeouts (all in milliseconds) */
182 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
183 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
185 static int prng_seed_saved = 0;
186 static int prng_initialised = 0;
191 /* Proportion of data that is entropy */
193 /* Counter goes positive if this command times out */
194 unsigned int badness;
195 /* Increases by factor of two each timeout */
196 unsigned int sticky_badness;
197 /* Path to executable */
199 /* argv to pass to executable */
201 /* full command string (debug) */
205 double stir_from_system(void);
206 double stir_from_programs(void);
207 double stir_gettimeofday(double entropy_estimate);
208 double stir_clock(double entropy_estimate);
209 double stir_rusage(int who, double entropy_estimate);
210 double hash_output_from_command(entropy_source_t *src, char *hash);
212 /* this is initialised from a file, by prng_read_commands() */
213 entropy_source_t *entropy_sources = NULL;
216 stir_from_system(void)
218 double total_entropy_estimate;
221 total_entropy_estimate = 0;
224 RAND_add(&i, sizeof(i), 0.5);
225 total_entropy_estimate += 0.1;
228 RAND_add(&i, sizeof(i), 0.5);
229 total_entropy_estimate += 0.1;
232 RAND_add(&i, sizeof(i), 0.0);
234 RAND_add(&i, sizeof(i), 0.0);
236 total_entropy_estimate += stir_gettimeofday(1.0);
237 total_entropy_estimate += stir_clock(0.5);
238 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
240 return(total_entropy_estimate);
244 stir_from_programs(void)
248 double entropy_estimate;
249 double total_entropy_estimate;
250 char hash[SHA_DIGEST_LENGTH];
252 total_entropy_estimate = 0;
253 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
255 while (entropy_sources[c].path != NULL) {
257 if (!entropy_sources[c].badness) {
258 /* Hash output from command */
259 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
261 /* Scale back entropy estimate according to command's rate */
262 entropy_estimate *= entropy_sources[c].rate;
264 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
265 if (entropy_estimate > SHA_DIGEST_LENGTH)
266 entropy_estimate = SHA_DIGEST_LENGTH;
268 /* Scale back estimates for subsequent passes through list */
269 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
272 RAND_add(hash, sizeof(hash), entropy_estimate);
274 debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
275 entropy_sources[c].cmdstring);
277 total_entropy_estimate += entropy_estimate;
279 /* Execution times should be a little unpredictable */
280 total_entropy_estimate += stir_gettimeofday(0.05);
281 total_entropy_estimate += stir_clock(0.05);
282 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
283 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
285 debug2("Command '%s' disabled (badness %d)",
286 entropy_sources[c].cmdstring, entropy_sources[c].badness);
288 if (entropy_sources[c].badness > 0)
289 entropy_sources[c].badness--;
296 return(total_entropy_estimate);
300 stir_gettimeofday(double entropy_estimate)
304 if (gettimeofday(&tv, NULL) == -1)
305 fatal("Couldn't gettimeofday: %s", strerror(errno));
307 RAND_add(&tv, sizeof(tv), entropy_estimate);
309 return(entropy_estimate);
313 stir_clock(double entropy_estimate)
319 RAND_add(&c, sizeof(c), entropy_estimate);
321 return(entropy_estimate);
322 #else /* _HAVE_CLOCK */
324 #endif /* _HAVE_CLOCK */
328 stir_rusage(int who, double entropy_estimate)
330 #ifdef HAVE_GETRUSAGE
333 if (getrusage(who, &ru) == -1)
336 RAND_add(&ru, sizeof(ru), entropy_estimate);
338 return(entropy_estimate);
339 #else /* _HAVE_GETRUSAGE */
341 #endif /* _HAVE_GETRUSAGE */
347 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
348 int secdiff, usecdiff;
350 secdiff = t2->tv_sec - t1->tv_sec;
351 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
352 return (int)(usecdiff / 1000);
356 hash_output_from_command(entropy_source_t *src, char *hash)
358 static int devnull = -1;
361 int cmd_eof = 0, error_abort = 0;
362 struct timeval tv_start, tv_current;
363 int msec_elapsed = 0;
368 int total_bytes_read;
371 debug3("Reading output from \'%s\'", src->cmdstring);
374 devnull = open("/dev/null", O_RDWR);
376 fatal("Couldn't open /dev/null: %s", strerror(errno));
380 fatal("Couldn't open pipe: %s", strerror(errno));
382 (void)gettimeofday(&tv_start, NULL); /* record start time */
384 switch (pid = fork()) {
388 fatal("Couldn't fork: %s", strerror(errno));
391 dup2(devnull, STDIN_FILENO);
392 dup2(p[1], STDOUT_FILENO);
393 dup2(p[1], STDERR_FILENO);
398 setuid(original_uid);
399 execv(src->path, (char**)(src->args));
400 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
403 default: /* Parent */
407 RAND_add(&pid, sizeof(&pid), 0.0);
411 /* Hash output from child */
413 total_bytes_read = 0;
415 while (!error_abort && !cmd_eof) {
420 (void) gettimeofday(&tv_current, 0);
421 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
422 if (msec_elapsed >= entropy_timeout_current) {
426 msec_remaining = entropy_timeout_current - msec_elapsed;
429 FD_SET(p[0], &rdset);
430 tv.tv_sec = msec_remaining / 1000;
431 tv.tv_usec = (msec_remaining % 1000) * 1000;
433 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
435 RAND_add(&tv, sizeof(tv), 0.0);
444 bytes_read = read(p[0], buf, sizeof(buf));
445 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
446 if (bytes_read == -1) {
449 } else if (bytes_read) {
450 SHA1_Update(&sha, buf, bytes_read);
451 total_bytes_read += bytes_read;
459 debug("Command '%s': select() failed: %s", src->cmdstring,
466 SHA1_Final(hash, &sha);
470 debug3("Time elapsed: %d msec", msec_elapsed);
472 if (waitpid(pid, &status, 0) == -1) {
473 error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
478 RAND_add(&status, sizeof(&status), 0.0);
481 /* closing p[0] on timeout causes the entropy command to
482 * SIGPIPE. Take whatever output we got, and mark this command
484 debug2("Command '%s' timed out", src->cmdstring);
485 src->sticky_badness *= 2;
486 src->badness = src->sticky_badness;
487 return(total_bytes_read);
490 if (WIFEXITED(status)) {
491 if (WEXITSTATUS(status)==0) {
492 return(total_bytes_read);
494 debug2("Command '%s' exit status was %d", src->cmdstring,
495 WEXITSTATUS(status));
496 src->badness = src->sticky_badness = 128;
499 } else if (WIFSIGNALED(status)) {
500 debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring,
502 src->badness = src->sticky_badness = 128;
509 * prng seedfile functions
512 prng_check_seedfile(char *filename) {
516 /* FIXME raceable: eg replace seed between this stat and subsequent open */
517 /* Not such a problem because we don't trust the seed file anyway */
518 if (lstat(filename, &st) == -1) {
519 /* Give up on hard errors */
521 debug("WARNING: Couldn't stat random seed file \"%s\": %s",
522 filename, strerror(errno));
528 if (!S_ISREG(st.st_mode))
529 fatal("PRNG seedfile %.100s is not a regular file", filename);
531 /* mode 0600, owned by root or the current user? */
532 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid)) {
533 debug("WARNING: PRNG seedfile %.100s must be mode 0600, owned by uid %d",
542 prng_write_seedfile(void) {
548 /* Don't bother if we have already saved a seed */
552 setuid(original_uid);
556 pw = getpwuid(original_uid);
558 fatal("Couldn't get password entry for current user (%i): %s",
559 original_uid, strerror(errno));
561 /* Try to ensure that the parent directory is there */
562 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
564 mkdir(filename, 0700);
566 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
569 debug("writing PRNG seed to file %.100s", filename);
571 RAND_bytes(seed, sizeof(seed));
573 /* Don't care if the seed doesn't exist */
574 prng_check_seedfile(filename);
576 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
577 debug("WARNING: couldn't access PRNG seedfile %.100s (%.100s)",
578 filename, strerror(errno));
580 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
581 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
589 prng_read_seedfile(void) {
595 pw = getpwuid(original_uid);
597 fatal("Couldn't get password entry for current user (%i): %s",
598 original_uid, strerror(errno));
600 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
603 debug("loading PRNG seed from file %.100s", filename);
605 if (!prng_check_seedfile(filename)) {
606 verbose("Random seed file not found or not valid, ignoring.");
610 /* open the file and read in the seed */
611 fd = open(filename, O_RDONLY);
613 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
616 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
617 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
619 memset(seed, '\0', sizeof(seed));
623 /* stir in the seed, with estimated entropy zero */
624 RAND_add(&seed, sizeof(seed), 0.0);
629 * entropy command initialisation functions
632 prng_read_commands(char *cmdfilename)
643 entropy_source_t *entcmd;
645 f = fopen(cmdfilename, "r");
647 fatal("couldn't read entropy commands file %.100s: %.100s",
648 cmdfilename, strerror(errno));
651 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
652 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
656 while (fgets(line, sizeof(line), f)) {
662 /* skip leading whitespace, test for blank line or comment */
663 cp = line + strspn(line, WHITESPACE);
664 if ((*cp == 0) || (*cp == '#'))
665 continue; /* done with this line */
667 /* First non-whitespace char should be double quote delimiting */
670 error("bad entropy command, %.100s line %d", cmdfilename,
675 /* first token, command args (incl. argv[0]) in double quotes */
676 cp = strtok(cp, "\"");
678 error("missing or bad command string, %.100s line %d -- ignored",
679 cmdfilename, linenum);
682 strlcpy(cmd, cp, sizeof(cmd));
684 /* second token, full command path */
685 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
686 error("missing command path, %.100s line %d -- ignored",
687 cmdfilename, linenum);
691 /* did configure mark this as dead? */
692 if (strncmp("undef", cp, 5) == 0)
695 strlcpy(path, cp, sizeof(path));
697 /* third token, entropy rate estimate for this command */
698 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
699 error("missing entropy estimate, %.100s line %d -- ignored",
700 cmdfilename, linenum);
703 est = strtod(cp, &argv);
706 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
707 error("garbage at end of line %d in %.100s -- ignored", linenum,
712 /* save the command for debug messages */
713 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
715 /* split the command args */
716 cp = strtok(cmd, WHITESPACE);
720 char *s = (char*)xmalloc(strlen(cp) + 1);
721 strncpy(s, cp, strlen(cp) + 1);
722 entcmd[cur_cmd].args[arg] = s;
724 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
726 if (strtok(NULL, WHITESPACE))
727 error("ignored extra command elements (max 5), %.100s line %d",
728 cmdfilename, linenum);
730 /* Copy the command path and rate estimate */
731 entcmd[cur_cmd].path = xstrdup(path);
732 entcmd[cur_cmd].rate = est;
734 /* Initialise other values */
735 entcmd[cur_cmd].sticky_badness = 1;
739 /* If we've filled the array, reallocate it twice the size */
740 /* Do this now because even if this we're on the last command,
741 we need another slot to mark the last entry */
742 if (cur_cmd == num_cmds) {
744 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
748 /* zero the last entry */
749 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
752 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
754 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
756 return (cur_cmd >= MIN_ENTROPY_SOURCES);
760 * Write a keyfile at exit
763 prng_seed_cleanup(void *junk)
765 prng_write_seedfile();
769 * Conditionally Seed OpenSSL's random number pool from
770 * syscalls and program output
775 void *old_sigchld_handler;
777 if (!prng_initialised)
778 fatal("RNG not initialised");
780 /* Make sure some other sigchld handler doesn't reap our entropy */
782 old_sigchld_handler = signal(SIGCHLD, SIG_DFL);
784 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
785 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
788 fatal("Not enough entropy in RNG");
790 signal(SIGCHLD, old_sigchld_handler);
793 fatal("Couldn't initialise builtin random number generator -- exiting.");
800 original_uid = getuid();
801 original_euid = geteuid();
803 /* Read in collection commands */
804 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
805 fatal("PRNG initialisation failed -- exiting.");
807 /* Set ourselves up to save a seed upon exit */
810 /* Give up privs while reading seed file */
811 if ((original_uid != original_euid) && (seteuid(original_uid) == -1))
812 fatal("Couldn't give up privileges");
814 prng_read_seedfile();
816 if ((original_uid != original_euid) && (seteuid(original_euid) == -1))
817 fatal("Couldn't restore privileges");
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) */