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 */
39 #include "pathnames.h"
45 # define offsetof(type, member) ((size_t) &((type *)0)->member)
48 /* Number of times to pass through command list gathering entropy */
49 #define NUM_ENTROPY_RUNS 1
51 /* Scale entropy estimates back by this amount on subsequent runs */
52 #define SCALE_PER_RUN 10.0
54 /* Minimum number of commands to be considered valid */
55 #define MIN_ENTROPY_SOURCES 16
57 #define WHITESPACE " \t\n"
60 # define RUSAGE_SELF 0
62 #ifndef RUSAGE_CHILDREN
63 # define RUSAGE_CHILDREN 0
66 #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
67 # define SAVED_IDS_WORK_WITH_SETEUID
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;
79 int addr_len, rval, errors;
83 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
84 fatal("Random pool path is too long");
86 fatal("Too many bytes to read from EGD");
88 memset(&addr, '\0', sizeof(addr));
89 addr.sun_family = AF_UNIX;
90 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
91 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
93 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
97 fd = socket(AF_UNIX, SOCK_STREAM, 0);
99 error("Couldn't create AF_UNIX socket: %s", strerror(errno));
103 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
104 error("Couldn't connect to EGD socket \"%s\": %s",
105 addr.sun_path, strerror(errno));
109 /* Send blocking read request to EGD */
113 if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
114 if (errno == EPIPE && errors < 10) {
119 error("Couldn't write to EGD socket \"%s\": %s",
120 EGD_SOCKET, strerror(errno));
124 if (atomicio(read, fd, buf, len) != len) {
125 if (errno == EPIPE && errors < 10) {
130 error("Couldn't read from EGD socket \"%s\": %s",
131 EGD_SOCKET, strerror(errno));
137 mysignal(SIGPIPE, old_sigpipe);
142 #else /* !EGD_SOCKET */
144 /* Collect entropy from /dev/urandom or pipe */
145 int get_random_bytes(unsigned char *buf, int len)
149 random_pool = open(RANDOM_POOL, O_RDONLY);
150 if (random_pool == -1) {
151 error("Couldn't open random pool \"%s\": %s",
152 RANDOM_POOL, strerror(errno));
156 if (atomicio(read, random_pool, buf, len) != len) {
157 error("Couldn't read from random pool \"%s\": %s",
158 RANDOM_POOL, strerror(errno));
167 #endif /* RANDOM_POOL */
168 #endif /* EGD_SOCKET */
171 * Seed OpenSSL's random number pool from Kernel random number generator
179 debug("Seeding random number generator");
181 if (!get_random_bytes(buf, sizeof(buf))) {
183 fatal("Entropy collection failed and entropy exhausted");
185 RAND_add(buf, sizeof(buf), sizeof(buf));
188 memset(buf, '\0', sizeof(buf));
192 void init_rng(void) {}
194 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
197 * FIXME: proper entropy estimations. All current values are guesses
198 * FIXME: (ATL) do estimates at compile time?
199 * FIXME: More entropy sources
202 /* slow command timeouts (all in milliseconds) */
203 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
204 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
206 static int prng_seed_saved = 0;
207 static int prng_initialised = 0;
212 /* Proportion of data that is entropy */
214 /* Counter goes positive if this command times out */
215 unsigned int badness;
216 /* Increases by factor of two each timeout */
217 unsigned int sticky_badness;
218 /* Path to executable */
220 /* argv to pass to executable */
222 /* full command string (debug) */
226 double stir_from_system(void);
227 double stir_from_programs(void);
228 double stir_gettimeofday(double entropy_estimate);
229 double stir_clock(double entropy_estimate);
230 double stir_rusage(int who, double entropy_estimate);
231 double hash_output_from_command(entropy_source_t *src, char *hash);
233 /* this is initialised from a file, by prng_read_commands() */
234 entropy_source_t *entropy_sources = NULL;
237 stir_from_system(void)
239 double total_entropy_estimate;
242 total_entropy_estimate = 0;
245 RAND_add(&i, sizeof(i), 0.5);
246 total_entropy_estimate += 0.1;
249 RAND_add(&i, sizeof(i), 0.5);
250 total_entropy_estimate += 0.1;
253 RAND_add(&i, sizeof(i), 0.0);
255 RAND_add(&i, sizeof(i), 0.0);
257 total_entropy_estimate += stir_gettimeofday(1.0);
258 total_entropy_estimate += stir_clock(0.5);
259 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
261 return(total_entropy_estimate);
265 stir_from_programs(void)
269 double entropy_estimate;
270 double total_entropy_estimate;
271 char hash[SHA_DIGEST_LENGTH];
273 total_entropy_estimate = 0;
274 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
276 while (entropy_sources[c].path != NULL) {
278 if (!entropy_sources[c].badness) {
279 /* Hash output from command */
280 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
282 /* Scale back entropy estimate according to command's rate */
283 entropy_estimate *= entropy_sources[c].rate;
285 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
286 if (entropy_estimate > SHA_DIGEST_LENGTH)
287 entropy_estimate = SHA_DIGEST_LENGTH;
289 /* Scale back estimates for subsequent passes through list */
290 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
293 RAND_add(hash, sizeof(hash), entropy_estimate);
295 debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
296 entropy_sources[c].cmdstring);
298 total_entropy_estimate += entropy_estimate;
300 /* Execution times should be a little unpredictable */
301 total_entropy_estimate += stir_gettimeofday(0.05);
302 total_entropy_estimate += stir_clock(0.05);
303 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
304 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
306 debug2("Command '%s' disabled (badness %d)",
307 entropy_sources[c].cmdstring, entropy_sources[c].badness);
309 if (entropy_sources[c].badness > 0)
310 entropy_sources[c].badness--;
317 return(total_entropy_estimate);
321 stir_gettimeofday(double entropy_estimate)
325 if (gettimeofday(&tv, NULL) == -1)
326 fatal("Couldn't gettimeofday: %s", strerror(errno));
328 RAND_add(&tv, sizeof(tv), entropy_estimate);
330 return(entropy_estimate);
334 stir_clock(double entropy_estimate)
340 RAND_add(&c, sizeof(c), entropy_estimate);
342 return(entropy_estimate);
343 #else /* _HAVE_CLOCK */
345 #endif /* _HAVE_CLOCK */
349 stir_rusage(int who, double entropy_estimate)
351 #ifdef HAVE_GETRUSAGE
354 if (getrusage(who, &ru) == -1)
357 RAND_add(&ru, sizeof(ru), entropy_estimate);
359 return(entropy_estimate);
360 #else /* _HAVE_GETRUSAGE */
362 #endif /* _HAVE_GETRUSAGE */
368 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
369 int secdiff, usecdiff;
371 secdiff = t2->tv_sec - t1->tv_sec;
372 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
373 return (int)(usecdiff / 1000);
377 hash_output_from_command(entropy_source_t *src, char *hash)
379 static int devnull = -1;
382 int cmd_eof = 0, error_abort = 0;
383 struct timeval tv_start, tv_current;
384 int msec_elapsed = 0;
389 int total_bytes_read;
392 debug3("Reading output from \'%s\'", src->cmdstring);
395 devnull = open("/dev/null", O_RDWR);
397 fatal("Couldn't open /dev/null: %s", strerror(errno));
401 fatal("Couldn't open pipe: %s", strerror(errno));
403 (void)gettimeofday(&tv_start, NULL); /* record start time */
405 switch (pid = fork()) {
409 fatal("Couldn't fork: %s", strerror(errno));
412 dup2(devnull, STDIN_FILENO);
413 dup2(p[1], STDOUT_FILENO);
414 dup2(p[1], STDERR_FILENO);
419 setuid(original_uid);
420 execv(src->path, (char**)(src->args));
421 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
424 default: /* Parent */
428 RAND_add(&pid, sizeof(&pid), 0.0);
432 /* Hash output from child */
434 total_bytes_read = 0;
436 while (!error_abort && !cmd_eof) {
441 (void) gettimeofday(&tv_current, 0);
442 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
443 if (msec_elapsed >= entropy_timeout_current) {
447 msec_remaining = entropy_timeout_current - msec_elapsed;
450 FD_SET(p[0], &rdset);
451 tv.tv_sec = msec_remaining / 1000;
452 tv.tv_usec = (msec_remaining % 1000) * 1000;
454 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
456 RAND_add(&tv, sizeof(tv), 0.0);
465 bytes_read = read(p[0], buf, sizeof(buf));
466 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
467 if (bytes_read == -1) {
470 } else if (bytes_read) {
471 SHA1_Update(&sha, buf, bytes_read);
472 total_bytes_read += bytes_read;
480 debug("Command '%s': select() failed: %s", src->cmdstring,
487 SHA1_Final(hash, &sha);
491 debug3("Time elapsed: %d msec", msec_elapsed);
493 if (waitpid(pid, &status, 0) == -1) {
494 error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
499 RAND_add(&status, sizeof(&status), 0.0);
502 /* closing p[0] on timeout causes the entropy command to
503 * SIGPIPE. Take whatever output we got, and mark this command
505 debug2("Command '%s' timed out", src->cmdstring);
506 src->sticky_badness *= 2;
507 src->badness = src->sticky_badness;
508 return(total_bytes_read);
511 if (WIFEXITED(status)) {
512 if (WEXITSTATUS(status)==0) {
513 return(total_bytes_read);
515 debug2("Command '%s' exit status was %d", src->cmdstring,
516 WEXITSTATUS(status));
517 src->badness = src->sticky_badness = 128;
520 } else if (WIFSIGNALED(status)) {
521 debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring,
523 src->badness = src->sticky_badness = 128;
530 * prng seedfile functions
533 prng_check_seedfile(char *filename) {
537 /* FIXME raceable: eg replace seed between this stat and subsequent open */
538 /* Not such a problem because we don't trust the seed file anyway */
539 if (lstat(filename, &st) == -1) {
540 /* Give up on hard errors */
542 debug("WARNING: Couldn't stat random seed file \"%s\": %s",
543 filename, strerror(errno));
549 if (!S_ISREG(st.st_mode))
550 fatal("PRNG seedfile %.100s is not a regular file", filename);
552 /* mode 0600, owned by root or the current user? */
553 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid)) {
554 debug("WARNING: PRNG seedfile %.100s must be mode 0600, owned by uid %d",
563 prng_write_seedfile(void) {
569 /* Don't bother if we have already saved a seed */
573 setuid(original_uid);
577 pw = getpwuid(original_uid);
579 fatal("Couldn't get password entry for current user (%i): %s",
580 original_uid, strerror(errno));
582 /* Try to ensure that the parent directory is there */
583 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
585 mkdir(filename, 0700);
587 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
590 debug("writing PRNG seed to file %.100s", filename);
592 RAND_bytes(seed, sizeof(seed));
594 /* Don't care if the seed doesn't exist */
595 prng_check_seedfile(filename);
597 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
598 debug("WARNING: couldn't access PRNG seedfile %.100s (%.100s)",
599 filename, strerror(errno));
601 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
602 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
610 prng_read_seedfile(void) {
616 pw = getpwuid(original_uid);
618 fatal("Couldn't get password entry for current user (%i): %s",
619 original_uid, strerror(errno));
621 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
624 debug("loading PRNG seed from file %.100s", filename);
626 if (!prng_check_seedfile(filename)) {
627 verbose("Random seed file not found or not valid, ignoring.");
631 /* open the file and read in the seed */
632 fd = open(filename, O_RDONLY);
634 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
637 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
638 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
640 memset(seed, '\0', sizeof(seed));
644 /* stir in the seed, with estimated entropy zero */
645 RAND_add(&seed, sizeof(seed), 0.0);
650 * entropy command initialisation functions
653 prng_read_commands(char *cmdfilename)
664 entropy_source_t *entcmd;
666 f = fopen(cmdfilename, "r");
668 fatal("couldn't read entropy commands file %.100s: %.100s",
669 cmdfilename, strerror(errno));
672 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
673 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
677 while (fgets(line, sizeof(line), f)) {
683 /* skip leading whitespace, test for blank line or comment */
684 cp = line + strspn(line, WHITESPACE);
685 if ((*cp == 0) || (*cp == '#'))
686 continue; /* done with this line */
688 /* First non-whitespace char should be double quote delimiting */
691 error("bad entropy command, %.100s line %d", cmdfilename,
696 /* first token, command args (incl. argv[0]) in double quotes */
697 cp = strtok(cp, "\"");
699 error("missing or bad command string, %.100s line %d -- ignored",
700 cmdfilename, linenum);
703 strlcpy(cmd, cp, sizeof(cmd));
705 /* second token, full command path */
706 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
707 error("missing command path, %.100s line %d -- ignored",
708 cmdfilename, linenum);
712 /* did configure mark this as dead? */
713 if (strncmp("undef", cp, 5) == 0)
716 strlcpy(path, cp, sizeof(path));
718 /* third token, entropy rate estimate for this command */
719 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
720 error("missing entropy estimate, %.100s line %d -- ignored",
721 cmdfilename, linenum);
724 est = strtod(cp, &argv);
727 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
728 error("garbage at end of line %d in %.100s -- ignored", linenum,
733 /* save the command for debug messages */
734 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
736 /* split the command args */
737 cp = strtok(cmd, WHITESPACE);
741 char *s = (char*)xmalloc(strlen(cp) + 1);
742 strncpy(s, cp, strlen(cp) + 1);
743 entcmd[cur_cmd].args[arg] = s;
745 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
747 if (strtok(NULL, WHITESPACE))
748 error("ignored extra command elements (max 5), %.100s line %d",
749 cmdfilename, linenum);
751 /* Copy the command path and rate estimate */
752 entcmd[cur_cmd].path = xstrdup(path);
753 entcmd[cur_cmd].rate = est;
755 /* Initialise other values */
756 entcmd[cur_cmd].sticky_badness = 1;
760 /* If we've filled the array, reallocate it twice the size */
761 /* Do this now because even if this we're on the last command,
762 we need another slot to mark the last entry */
763 if (cur_cmd == num_cmds) {
765 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
769 /* zero the last entry */
770 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
773 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
775 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
777 return (cur_cmd >= MIN_ENTROPY_SOURCES);
781 * Write a keyfile at exit
784 prng_seed_cleanup(void *junk)
786 prng_write_seedfile();
790 * Conditionally Seed OpenSSL's random number pool from
791 * syscalls and program output
796 mysig_t old_sigchld_handler;
798 if (!prng_initialised)
799 fatal("RNG not initialised");
801 /* Make sure some other sigchld handler doesn't reap our entropy */
803 old_sigchld_handler = mysignal(SIGCHLD, SIG_DFL);
805 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
806 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
809 fatal("Not enough entropy in RNG");
811 mysignal(SIGCHLD, old_sigchld_handler);
814 fatal("Couldn't initialise builtin random number generator -- exiting.");
821 original_uid = getuid();
822 original_euid = geteuid();
824 /* Read in collection commands */
825 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
826 fatal("PRNG initialisation failed -- exiting.");
828 /* Set ourselves up to save a seed upon exit */
831 /* Give up privs while reading seed file */
832 #ifdef SAVED_IDS_WORK_WITH_SETEUID
833 if ((original_uid != original_euid) && (seteuid(original_uid) == -1))
834 fatal("Couldn't give up privileges");
835 #else /* SAVED_IDS_WORK_WITH_SETEUID */
837 * Propagate the privileged uid to all of our uids.
838 * Set the effective uid to the given (unprivileged) uid.
840 if (original_uid != original_euid && setuid(original_euid) == -1 ||
841 seteuid(original_uid) == -1)
842 fatal("Couldn't give up privileges");
843 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
845 prng_read_seedfile();
847 #ifdef SAVED_IDS_WORK_WITH_SETEUID
848 if ((original_uid != original_euid) && (seteuid(original_euid) == -1))
849 fatal("Couldn't restore privileges");
850 #else /* SAVED_IDS_WORK_WITH_SETEUID */
852 * We are unable to restore the real uid to its unprivileged value.
853 * Propagate the real uid (usually more privileged) to effective uid
856 if (original_uid != original_euid && seteuid(original_euid) == -1 ||
857 setuid(original_uid) == -1)
858 fatal("Couldn't restore privileges");
859 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
861 fatal_add_cleanup(prng_seed_cleanup, NULL);
862 atexit(prng_write_seedfile);
864 prng_initialised = 1;
867 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */