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>
29 #include <openssl/crypto.h>
31 /* SunOS 4.4.4 needs this */
32 #ifdef HAVE_FLOATINGPOINT_H
33 # include <floatingpoint.h>
34 #endif /* HAVE_FLOATINGPOINT_H */
40 #include "pathnames.h"
46 # define offsetof(type, member) ((size_t) &((type *)0)->member)
49 /* Number of times to pass through command list gathering entropy */
50 #define NUM_ENTROPY_RUNS 1
52 /* Scale entropy estimates back by this amount on subsequent runs */
53 #define SCALE_PER_RUN 10.0
55 /* Minimum number of commands to be considered valid */
56 #define MIN_ENTROPY_SOURCES 16
58 #define WHITESPACE " \t\n"
61 # define RUSAGE_SELF 0
63 #ifndef RUSAGE_CHILDREN
64 # define RUSAGE_CHILDREN 0
67 #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
68 # define SAVED_IDS_WORK_WITH_SETEUID
71 void check_openssl_version(void)
73 if (SSLeay() != OPENSSL_VERSION_NUMBER)
74 fatal("OpenSSL version mismatch. Built against %x, you "
75 "have %x", OPENSSL_VERSION_NUMBER, SSLeay());
79 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
82 /* Collect entropy from EGD */
83 int get_random_bytes(unsigned char *buf, int len)
87 struct sockaddr_un addr;
88 int addr_len, rval, errors;
92 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
93 fatal("Random pool path is too long");
95 fatal("Too many bytes to read from EGD");
97 memset(&addr, '\0', sizeof(addr));
98 addr.sun_family = AF_UNIX;
99 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
100 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
102 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
106 fd = socket(AF_UNIX, SOCK_STREAM, 0);
108 error("Couldn't create AF_UNIX socket: %s", strerror(errno));
112 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
113 error("Couldn't connect to EGD socket \"%s\": %s",
114 addr.sun_path, strerror(errno));
118 /* Send blocking read request to EGD */
122 if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
123 if (errno == EPIPE && errors < 10) {
128 error("Couldn't write to EGD socket \"%s\": %s",
129 EGD_SOCKET, strerror(errno));
133 if (atomicio(read, fd, buf, len) != len) {
134 if (errno == EPIPE && errors < 10) {
139 error("Couldn't read from EGD socket \"%s\": %s",
140 EGD_SOCKET, strerror(errno));
146 mysignal(SIGPIPE, old_sigpipe);
151 #else /* !EGD_SOCKET */
153 /* Collect entropy from /dev/urandom or pipe */
154 int get_random_bytes(unsigned char *buf, int len)
158 random_pool = open(RANDOM_POOL, O_RDONLY);
159 if (random_pool == -1) {
160 error("Couldn't open random pool \"%s\": %s",
161 RANDOM_POOL, strerror(errno));
165 if (atomicio(read, random_pool, buf, len) != len) {
166 error("Couldn't read from random pool \"%s\": %s",
167 RANDOM_POOL, strerror(errno));
176 #endif /* RANDOM_POOL */
177 #endif /* EGD_SOCKET */
180 * Seed OpenSSL's random number pool from Kernel random number generator
188 debug("Seeding random number generator");
190 if (!get_random_bytes(buf, sizeof(buf))) {
192 fatal("Entropy collection failed and entropy exhausted");
194 RAND_add(buf, sizeof(buf), sizeof(buf));
197 memset(buf, '\0', sizeof(buf));
202 check_openssl_version();
205 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
208 * FIXME: proper entropy estimations. All current values are guesses
209 * FIXME: (ATL) do estimates at compile time?
210 * FIXME: More entropy sources
213 /* slow command timeouts (all in milliseconds) */
214 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
215 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
217 static int prng_seed_saved = 0;
218 static int prng_initialised = 0;
223 /* Proportion of data that is entropy */
225 /* Counter goes positive if this command times out */
226 unsigned int badness;
227 /* Increases by factor of two each timeout */
228 unsigned int sticky_badness;
229 /* Path to executable */
231 /* argv to pass to executable */
233 /* full command string (debug) */
237 double stir_from_system(void);
238 double stir_from_programs(void);
239 double stir_gettimeofday(double entropy_estimate);
240 double stir_clock(double entropy_estimate);
241 double stir_rusage(int who, double entropy_estimate);
242 double hash_output_from_command(entropy_source_t *src, char *hash);
244 /* this is initialised from a file, by prng_read_commands() */
245 entropy_source_t *entropy_sources = NULL;
248 stir_from_system(void)
250 double total_entropy_estimate;
253 total_entropy_estimate = 0;
256 RAND_add(&i, sizeof(i), 0.5);
257 total_entropy_estimate += 0.1;
260 RAND_add(&i, sizeof(i), 0.5);
261 total_entropy_estimate += 0.1;
264 RAND_add(&i, sizeof(i), 0.0);
266 RAND_add(&i, sizeof(i), 0.0);
268 total_entropy_estimate += stir_gettimeofday(1.0);
269 total_entropy_estimate += stir_clock(0.5);
270 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
272 return(total_entropy_estimate);
276 stir_from_programs(void)
280 double entropy_estimate;
281 double total_entropy_estimate;
282 char hash[SHA_DIGEST_LENGTH];
284 total_entropy_estimate = 0;
285 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
287 while (entropy_sources[c].path != NULL) {
289 if (!entropy_sources[c].badness) {
290 /* Hash output from command */
291 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
293 /* Scale back entropy estimate according to command's rate */
294 entropy_estimate *= entropy_sources[c].rate;
296 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
297 if (entropy_estimate > SHA_DIGEST_LENGTH)
298 entropy_estimate = SHA_DIGEST_LENGTH;
300 /* Scale back estimates for subsequent passes through list */
301 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
304 RAND_add(hash, sizeof(hash), entropy_estimate);
306 debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
307 entropy_sources[c].cmdstring);
309 total_entropy_estimate += entropy_estimate;
311 /* Execution times should be a little unpredictable */
312 total_entropy_estimate += stir_gettimeofday(0.05);
313 total_entropy_estimate += stir_clock(0.05);
314 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
315 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
317 debug2("Command '%s' disabled (badness %d)",
318 entropy_sources[c].cmdstring, entropy_sources[c].badness);
320 if (entropy_sources[c].badness > 0)
321 entropy_sources[c].badness--;
328 return(total_entropy_estimate);
332 stir_gettimeofday(double entropy_estimate)
336 if (gettimeofday(&tv, NULL) == -1)
337 fatal("Couldn't gettimeofday: %s", strerror(errno));
339 RAND_add(&tv, sizeof(tv), entropy_estimate);
341 return(entropy_estimate);
345 stir_clock(double entropy_estimate)
351 RAND_add(&c, sizeof(c), entropy_estimate);
353 return(entropy_estimate);
354 #else /* _HAVE_CLOCK */
356 #endif /* _HAVE_CLOCK */
360 stir_rusage(int who, double entropy_estimate)
362 #ifdef HAVE_GETRUSAGE
365 if (getrusage(who, &ru) == -1)
368 RAND_add(&ru, sizeof(ru), entropy_estimate);
370 return(entropy_estimate);
371 #else /* _HAVE_GETRUSAGE */
373 #endif /* _HAVE_GETRUSAGE */
379 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
380 int secdiff, usecdiff;
382 secdiff = t2->tv_sec - t1->tv_sec;
383 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
384 return (int)(usecdiff / 1000);
388 hash_output_from_command(entropy_source_t *src, char *hash)
390 static int devnull = -1;
393 int cmd_eof = 0, error_abort = 0;
394 struct timeval tv_start, tv_current;
395 int msec_elapsed = 0;
400 int total_bytes_read;
403 debug3("Reading output from \'%s\'", src->cmdstring);
406 devnull = open("/dev/null", O_RDWR);
408 fatal("Couldn't open /dev/null: %s", strerror(errno));
412 fatal("Couldn't open pipe: %s", strerror(errno));
414 (void)gettimeofday(&tv_start, NULL); /* record start time */
416 switch (pid = fork()) {
420 fatal("Couldn't fork: %s", strerror(errno));
423 dup2(devnull, STDIN_FILENO);
424 dup2(p[1], STDOUT_FILENO);
425 dup2(p[1], STDERR_FILENO);
430 setuid(original_uid);
431 execv(src->path, (char**)(src->args));
432 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
435 default: /* Parent */
439 RAND_add(&pid, sizeof(&pid), 0.0);
443 /* Hash output from child */
445 total_bytes_read = 0;
447 while (!error_abort && !cmd_eof) {
452 (void) gettimeofday(&tv_current, 0);
453 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
454 if (msec_elapsed >= entropy_timeout_current) {
458 msec_remaining = entropy_timeout_current - msec_elapsed;
461 FD_SET(p[0], &rdset);
462 tv.tv_sec = msec_remaining / 1000;
463 tv.tv_usec = (msec_remaining % 1000) * 1000;
465 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
467 RAND_add(&tv, sizeof(tv), 0.0);
476 bytes_read = read(p[0], buf, sizeof(buf));
477 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
478 if (bytes_read == -1) {
481 } else if (bytes_read) {
482 SHA1_Update(&sha, buf, bytes_read);
483 total_bytes_read += bytes_read;
491 debug("Command '%s': select() failed: %s", src->cmdstring,
498 SHA1_Final(hash, &sha);
502 debug3("Time elapsed: %d msec", msec_elapsed);
504 if (waitpid(pid, &status, 0) == -1) {
505 error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
510 RAND_add(&status, sizeof(&status), 0.0);
513 /* closing p[0] on timeout causes the entropy command to
514 * SIGPIPE. Take whatever output we got, and mark this command
516 debug2("Command '%s' timed out", src->cmdstring);
517 src->sticky_badness *= 2;
518 src->badness = src->sticky_badness;
519 return(total_bytes_read);
522 if (WIFEXITED(status)) {
523 if (WEXITSTATUS(status)==0) {
524 return(total_bytes_read);
526 debug2("Command '%s' exit status was %d", src->cmdstring,
527 WEXITSTATUS(status));
528 src->badness = src->sticky_badness = 128;
531 } else if (WIFSIGNALED(status)) {
532 debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring,
534 src->badness = src->sticky_badness = 128;
541 * prng seedfile functions
544 prng_check_seedfile(char *filename) {
548 /* FIXME raceable: eg replace seed between this stat and subsequent open */
549 /* Not such a problem because we don't trust the seed file anyway */
550 if (lstat(filename, &st) == -1) {
551 /* Give up on hard errors */
553 debug("WARNING: Couldn't stat random seed file \"%s\": %s",
554 filename, strerror(errno));
560 if (!S_ISREG(st.st_mode))
561 fatal("PRNG seedfile %.100s is not a regular file", filename);
563 /* mode 0600, owned by root or the current user? */
564 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid)) {
565 debug("WARNING: PRNG seedfile %.100s must be mode 0600, owned by uid %d",
574 prng_write_seedfile(void) {
580 /* Don't bother if we have already saved a seed */
584 setuid(original_uid);
588 pw = getpwuid(original_uid);
590 fatal("Couldn't get password entry for current user (%i): %s",
591 original_uid, strerror(errno));
593 /* Try to ensure that the parent directory is there */
594 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
596 mkdir(filename, 0700);
598 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
601 debug("writing PRNG seed to file %.100s", filename);
603 RAND_bytes(seed, sizeof(seed));
605 /* Don't care if the seed doesn't exist */
606 prng_check_seedfile(filename);
608 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
609 debug("WARNING: couldn't access PRNG seedfile %.100s (%.100s)",
610 filename, strerror(errno));
612 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
613 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
621 prng_read_seedfile(void) {
627 pw = getpwuid(original_uid);
629 fatal("Couldn't get password entry for current user (%i): %s",
630 original_uid, strerror(errno));
632 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
635 debug("loading PRNG seed from file %.100s", filename);
637 if (!prng_check_seedfile(filename)) {
638 verbose("Random seed file not found or not valid, ignoring.");
642 /* open the file and read in the seed */
643 fd = open(filename, O_RDONLY);
645 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
648 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
649 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
651 memset(seed, '\0', sizeof(seed));
655 /* stir in the seed, with estimated entropy zero */
656 RAND_add(&seed, sizeof(seed), 0.0);
661 * entropy command initialisation functions
664 prng_read_commands(char *cmdfilename)
675 entropy_source_t *entcmd;
677 f = fopen(cmdfilename, "r");
679 fatal("couldn't read entropy commands file %.100s: %.100s",
680 cmdfilename, strerror(errno));
683 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
684 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
688 while (fgets(line, sizeof(line), f)) {
694 /* skip leading whitespace, test for blank line or comment */
695 cp = line + strspn(line, WHITESPACE);
696 if ((*cp == 0) || (*cp == '#'))
697 continue; /* done with this line */
699 /* First non-whitespace char should be double quote delimiting */
702 error("bad entropy command, %.100s line %d", cmdfilename,
707 /* first token, command args (incl. argv[0]) in double quotes */
708 cp = strtok(cp, "\"");
710 error("missing or bad command string, %.100s line %d -- ignored",
711 cmdfilename, linenum);
714 strlcpy(cmd, cp, sizeof(cmd));
716 /* second token, full command path */
717 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
718 error("missing command path, %.100s line %d -- ignored",
719 cmdfilename, linenum);
723 /* did configure mark this as dead? */
724 if (strncmp("undef", cp, 5) == 0)
727 strlcpy(path, cp, sizeof(path));
729 /* third token, entropy rate estimate for this command */
730 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
731 error("missing entropy estimate, %.100s line %d -- ignored",
732 cmdfilename, linenum);
735 est = strtod(cp, &argv);
738 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
739 error("garbage at end of line %d in %.100s -- ignored", linenum,
744 /* save the command for debug messages */
745 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
747 /* split the command args */
748 cp = strtok(cmd, WHITESPACE);
752 char *s = (char*)xmalloc(strlen(cp) + 1);
753 strncpy(s, cp, strlen(cp) + 1);
754 entcmd[cur_cmd].args[arg] = s;
756 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
758 if (strtok(NULL, WHITESPACE))
759 error("ignored extra command elements (max 5), %.100s line %d",
760 cmdfilename, linenum);
762 /* Copy the command path and rate estimate */
763 entcmd[cur_cmd].path = xstrdup(path);
764 entcmd[cur_cmd].rate = est;
766 /* Initialise other values */
767 entcmd[cur_cmd].sticky_badness = 1;
771 /* If we've filled the array, reallocate it twice the size */
772 /* Do this now because even if this we're on the last command,
773 we need another slot to mark the last entry */
774 if (cur_cmd == num_cmds) {
776 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
780 /* zero the last entry */
781 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
784 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
786 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
788 return (cur_cmd >= MIN_ENTROPY_SOURCES);
792 * Write a keyfile at exit
795 prng_seed_cleanup(void *junk)
797 prng_write_seedfile();
801 * Conditionally Seed OpenSSL's random number pool from
802 * syscalls and program output
807 mysig_t old_sigchld_handler;
809 if (!prng_initialised)
810 fatal("RNG not initialised");
812 /* Make sure some other sigchld handler doesn't reap our entropy */
814 old_sigchld_handler = mysignal(SIGCHLD, SIG_DFL);
816 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
817 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
820 fatal("Not enough entropy in RNG");
822 mysignal(SIGCHLD, old_sigchld_handler);
825 fatal("Couldn't initialise builtin random number generator -- exiting.");
832 check_openssl_version();
834 original_uid = getuid();
835 original_euid = geteuid();
837 /* Read in collection commands */
838 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
839 fatal("PRNG initialisation failed -- exiting.");
841 /* Set ourselves up to save a seed upon exit */
844 /* Give up privs while reading seed file */
845 #ifdef SAVED_IDS_WORK_WITH_SETEUID
846 if ((original_uid != original_euid) && (seteuid(original_uid) == -1))
847 fatal("Couldn't give up privileges");
848 #else /* SAVED_IDS_WORK_WITH_SETEUID */
850 * Propagate the privileged uid to all of our uids.
851 * Set the effective uid to the given (unprivileged) uid.
853 if (original_uid != original_euid && setuid(original_euid) == -1 ||
854 seteuid(original_uid) == -1)
855 fatal("Couldn't give up privileges");
856 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
858 prng_read_seedfile();
860 #ifdef SAVED_IDS_WORK_WITH_SETEUID
861 if ((original_uid != original_euid) && (seteuid(original_euid) == -1))
862 fatal("Couldn't restore privileges");
863 #else /* SAVED_IDS_WORK_WITH_SETEUID */
865 * We are unable to restore the real uid to its unprivileged value.
866 * Propagate the real uid (usually more privileged) to effective uid
869 if (original_uid != original_euid && seteuid(original_euid) == -1 ||
870 setuid(original_uid) == -1)
871 fatal("Couldn't restore privileges");
872 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
874 fatal_add_cleanup(prng_seed_cleanup, NULL);
875 atexit(prng_write_seedfile);
877 prng_initialised = 1;
880 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */