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 */
38 #include "pathnames.h"
44 # define offsetof(type, member) ((size_t) &((type *)0)->member)
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);
275 debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
276 entropy_sources[c].cmdstring);
278 total_entropy_estimate += entropy_estimate;
280 /* Execution times should be a little unpredictable */
281 total_entropy_estimate += stir_gettimeofday(0.05);
282 total_entropy_estimate += stir_clock(0.05);
283 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
284 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
286 debug2("Command '%s' disabled (badness %d)",
287 entropy_sources[c].cmdstring, entropy_sources[c].badness);
289 if (entropy_sources[c].badness > 0)
290 entropy_sources[c].badness--;
297 return(total_entropy_estimate);
301 stir_gettimeofday(double entropy_estimate)
305 if (gettimeofday(&tv, NULL) == -1)
306 fatal("Couldn't gettimeofday: %s", strerror(errno));
308 RAND_add(&tv, sizeof(tv), entropy_estimate);
310 return(entropy_estimate);
314 stir_clock(double entropy_estimate)
320 RAND_add(&c, sizeof(c), entropy_estimate);
322 return(entropy_estimate);
323 #else /* _HAVE_CLOCK */
325 #endif /* _HAVE_CLOCK */
329 stir_rusage(int who, double entropy_estimate)
331 #ifdef HAVE_GETRUSAGE
334 if (getrusage(who, &ru) == -1)
337 RAND_add(&ru, sizeof(ru), entropy_estimate);
339 return(entropy_estimate);
340 #else /* _HAVE_GETRUSAGE */
342 #endif /* _HAVE_GETRUSAGE */
348 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
349 int secdiff, usecdiff;
351 secdiff = t2->tv_sec - t1->tv_sec;
352 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
353 return (int)(usecdiff / 1000);
357 hash_output_from_command(entropy_source_t *src, char *hash)
359 static int devnull = -1;
362 int cmd_eof = 0, error_abort = 0;
363 struct timeval tv_start, tv_current;
364 int msec_elapsed = 0;
369 int total_bytes_read;
372 debug3("Reading output from \'%s\'", src->cmdstring);
375 devnull = open("/dev/null", O_RDWR);
377 fatal("Couldn't open /dev/null: %s", strerror(errno));
381 fatal("Couldn't open pipe: %s", strerror(errno));
383 (void)gettimeofday(&tv_start, NULL); /* record start time */
385 switch (pid = fork()) {
389 fatal("Couldn't fork: %s", strerror(errno));
392 dup2(devnull, STDIN_FILENO);
393 dup2(p[1], STDOUT_FILENO);
394 dup2(p[1], STDERR_FILENO);
399 setuid(original_uid);
400 execv(src->path, (char**)(src->args));
401 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
404 default: /* Parent */
408 RAND_add(&pid, sizeof(&pid), 0.0);
412 /* Hash output from child */
414 total_bytes_read = 0;
416 while (!error_abort && !cmd_eof) {
421 (void) gettimeofday(&tv_current, 0);
422 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
423 if (msec_elapsed >= entropy_timeout_current) {
427 msec_remaining = entropy_timeout_current - msec_elapsed;
430 FD_SET(p[0], &rdset);
431 tv.tv_sec = msec_remaining / 1000;
432 tv.tv_usec = (msec_remaining % 1000) * 1000;
434 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
436 RAND_add(&tv, sizeof(tv), 0.0);
445 bytes_read = read(p[0], buf, sizeof(buf));
446 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
447 if (bytes_read == -1) {
450 } else if (bytes_read) {
451 SHA1_Update(&sha, buf, bytes_read);
452 total_bytes_read += bytes_read;
460 debug("Command '%s': select() failed: %s", src->cmdstring,
467 SHA1_Final(hash, &sha);
471 debug3("Time elapsed: %d msec", msec_elapsed);
473 if (waitpid(pid, &status, 0) == -1) {
474 error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
479 RAND_add(&status, sizeof(&status), 0.0);
482 /* closing p[0] on timeout causes the entropy command to
483 * SIGPIPE. Take whatever output we got, and mark this command
485 debug2("Command '%s' timed out", src->cmdstring);
486 src->sticky_badness *= 2;
487 src->badness = src->sticky_badness;
488 return(total_bytes_read);
491 if (WIFEXITED(status)) {
492 if (WEXITSTATUS(status)==0) {
493 return(total_bytes_read);
495 debug2("Command '%s' exit status was %d", src->cmdstring,
496 WEXITSTATUS(status));
497 src->badness = src->sticky_badness = 128;
500 } else if (WIFSIGNALED(status)) {
501 debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring,
503 src->badness = src->sticky_badness = 128;
510 * prng seedfile functions
513 prng_check_seedfile(char *filename) {
517 /* FIXME raceable: eg replace seed between this stat and subsequent open */
518 /* Not such a problem because we don't trust the seed file anyway */
519 if (lstat(filename, &st) == -1) {
520 /* Give up on hard errors */
522 debug("WARNING: Couldn't stat random seed file \"%s\": %s",
523 filename, strerror(errno));
529 if (!S_ISREG(st.st_mode))
530 fatal("PRNG seedfile %.100s is not a regular file", filename);
532 /* mode 0600, owned by root or the current user? */
533 if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid)) {
534 debug("WARNING: PRNG seedfile %.100s must be mode 0600, owned by uid %d",
543 prng_write_seedfile(void) {
549 /* Don't bother if we have already saved a seed */
553 setuid(original_uid);
557 pw = getpwuid(original_uid);
559 fatal("Couldn't get password entry for current user (%i): %s",
560 original_uid, strerror(errno));
562 /* Try to ensure that the parent directory is there */
563 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
565 mkdir(filename, 0700);
567 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
570 debug("writing PRNG seed to file %.100s", filename);
572 RAND_bytes(seed, sizeof(seed));
574 /* Don't care if the seed doesn't exist */
575 prng_check_seedfile(filename);
577 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
578 debug("WARNING: couldn't access PRNG seedfile %.100s (%.100s)",
579 filename, strerror(errno));
581 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
582 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
590 prng_read_seedfile(void) {
596 pw = getpwuid(original_uid);
598 fatal("Couldn't get password entry for current user (%i): %s",
599 original_uid, strerror(errno));
601 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
604 debug("loading PRNG seed from file %.100s", filename);
606 if (!prng_check_seedfile(filename)) {
607 verbose("Random seed file not found or not valid, ignoring.");
611 /* open the file and read in the seed */
612 fd = open(filename, O_RDONLY);
614 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
617 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
618 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
620 memset(seed, '\0', sizeof(seed));
624 /* stir in the seed, with estimated entropy zero */
625 RAND_add(&seed, sizeof(seed), 0.0);
630 * entropy command initialisation functions
633 prng_read_commands(char *cmdfilename)
644 entropy_source_t *entcmd;
646 f = fopen(cmdfilename, "r");
648 fatal("couldn't read entropy commands file %.100s: %.100s",
649 cmdfilename, strerror(errno));
652 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
653 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
657 while (fgets(line, sizeof(line), f)) {
663 /* skip leading whitespace, test for blank line or comment */
664 cp = line + strspn(line, WHITESPACE);
665 if ((*cp == 0) || (*cp == '#'))
666 continue; /* done with this line */
668 /* First non-whitespace char should be double quote delimiting */
671 error("bad entropy command, %.100s line %d", cmdfilename,
676 /* first token, command args (incl. argv[0]) in double quotes */
677 cp = strtok(cp, "\"");
679 error("missing or bad command string, %.100s line %d -- ignored",
680 cmdfilename, linenum);
683 strlcpy(cmd, cp, sizeof(cmd));
685 /* second token, full command path */
686 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
687 error("missing command path, %.100s line %d -- ignored",
688 cmdfilename, linenum);
692 /* did configure mark this as dead? */
693 if (strncmp("undef", cp, 5) == 0)
696 strlcpy(path, cp, sizeof(path));
698 /* third token, entropy rate estimate for this command */
699 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
700 error("missing entropy estimate, %.100s line %d -- ignored",
701 cmdfilename, linenum);
704 est = strtod(cp, &argv);
707 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
708 error("garbage at end of line %d in %.100s -- ignored", linenum,
713 /* save the command for debug messages */
714 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
716 /* split the command args */
717 cp = strtok(cmd, WHITESPACE);
721 char *s = (char*)xmalloc(strlen(cp) + 1);
722 strncpy(s, cp, strlen(cp) + 1);
723 entcmd[cur_cmd].args[arg] = s;
725 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
727 if (strtok(NULL, WHITESPACE))
728 error("ignored extra command elements (max 5), %.100s line %d",
729 cmdfilename, linenum);
731 /* Copy the command path and rate estimate */
732 entcmd[cur_cmd].path = xstrdup(path);
733 entcmd[cur_cmd].rate = est;
735 /* Initialise other values */
736 entcmd[cur_cmd].sticky_badness = 1;
740 /* If we've filled the array, reallocate it twice the size */
741 /* Do this now because even if this we're on the last command,
742 we need another slot to mark the last entry */
743 if (cur_cmd == num_cmds) {
745 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
749 /* zero the last entry */
750 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
753 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
755 debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
757 return (cur_cmd >= MIN_ENTROPY_SOURCES);
761 * Write a keyfile at exit
764 prng_seed_cleanup(void *junk)
766 prng_write_seedfile();
770 * Conditionally Seed OpenSSL's random number pool from
771 * syscalls and program output
776 void *old_sigchld_handler;
778 if (!prng_initialised)
779 fatal("RNG not initialised");
781 /* Make sure some other sigchld handler doesn't reap our entropy */
783 old_sigchld_handler = signal(SIGCHLD, SIG_DFL);
785 debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs());
786 debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system());
789 fatal("Not enough entropy in RNG");
791 signal(SIGCHLD, old_sigchld_handler);
794 fatal("Couldn't initialise builtin random number generator -- exiting.");
801 original_uid = getuid();
802 original_euid = geteuid();
804 /* Read in collection commands */
805 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
806 fatal("PRNG initialisation failed -- exiting.");
808 /* Set ourselves up to save a seed upon exit */
811 /* Give up privs while reading seed file */
812 if ((original_uid != original_euid) && (seteuid(original_uid) == -1))
813 fatal("Couldn't give up privileges");
815 prng_read_seedfile();
817 if ((original_uid != original_euid) && (seteuid(original_euid) == -1))
818 fatal("Couldn't restore privileges");
820 fatal_add_cleanup(prng_seed_cleanup, NULL);
821 atexit(prng_write_seedfile);
823 prng_initialised = 1;
826 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */