2 * Copyright (c) 2001-2002 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 <sys/types.h>
28 #include <sys/resource.h>
38 #include <openssl/rand.h>
39 #include <openssl/sha.h>
40 #include <openssl/crypto.h>
42 /* SunOS 4.4.4 needs this */
43 #ifdef HAVE_FLOATINGPOINT_H
44 # include <floatingpoint.h>
45 #endif /* HAVE_FLOATINGPOINT_H */
50 #include "pathnames.h"
53 /* Number of bytes we write out */
54 #define OUTPUT_SEED_SIZE 48
56 /* Length of on-disk seedfiles */
57 #define SEED_FILE_SIZE 1024
59 /* Maximum number of command-line arguments to read from file */
62 /* Minimum number of usable commands to be considered sufficient */
63 #define MIN_ENTROPY_SOURCES 16
65 /* Path to on-disk seed file (relative to user's home directory */
66 #ifndef SSH_PRNG_SEED_FILE
67 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
70 /* Path to PRNG commands list */
71 #ifndef SSH_PRNG_COMMAND_FILE
72 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
75 extern char *__progname;
77 #define WHITESPACE " \t\n"
80 # define RUSAGE_SELF 0
82 #ifndef RUSAGE_CHILDREN
83 # define RUSAGE_CHILDREN 0
86 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
87 # define USE_SEED_FILES
91 /* Proportion of data that is entropy */
93 /* Counter goes positive if this command times out */
95 /* Increases by factor of two each timeout */
96 unsigned int sticky_badness;
97 /* Path to executable */
99 /* argv to pass to executable */
100 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
101 /* full command string (debug) */
105 /* slow command timeouts (all in milliseconds) */
106 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
107 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
109 /* this is initialised from a file, by prng_read_commands() */
110 static entropy_cmd_t *entropy_cmds = NULL;
113 double stir_from_system(void);
114 double stir_from_programs(void);
115 double stir_gettimeofday(double entropy_estimate);
116 double stir_clock(double entropy_estimate);
117 double stir_rusage(int who, double entropy_estimate);
118 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
119 int get_random_bytes_prngd(unsigned char *buf, int len,
120 unsigned short tcp_port, char *socket_path);
123 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
124 * listening either on 'tcp_port', or via Unix domain socket at *
126 * Either a non-zero tcp_port or a non-null socket_path must be
128 * Returns 0 on success, -1 on error
131 get_random_bytes_prngd(unsigned char *buf, int len,
132 unsigned short tcp_port, char *socket_path)
134 int fd, addr_len, rval, errors;
136 struct sockaddr_storage addr;
137 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
138 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
142 if (socket_path == NULL && tcp_port == 0)
143 fatal("You must specify a port or a socket");
144 if (socket_path != NULL &&
145 strlen(socket_path) >= sizeof(addr_un->sun_path))
146 fatal("Random pool path is too long");
147 if (len <= 0 || len > 255)
148 fatal("Too many bytes (%d) to read from PRNGD", len);
150 memset(&addr, '\0', sizeof(addr));
153 addr_in->sin_family = AF_INET;
154 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
155 addr_in->sin_port = htons(tcp_port);
156 addr_len = sizeof(*addr_in);
158 addr_un->sun_family = AF_UNIX;
159 strlcpy(addr_un->sun_path, socket_path,
160 sizeof(addr_un->sun_path));
161 addr_len = offsetof(struct sockaddr_un, sun_path) +
162 strlen(socket_path) + 1;
165 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
170 fd = socket(addr.ss_family, SOCK_STREAM, 0);
172 error("Couldn't create socket: %s", strerror(errno));
176 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
178 error("Couldn't connect to PRNGD port %d: %s",
179 tcp_port, strerror(errno));
181 error("Couldn't connect to PRNGD socket \"%s\": %s",
182 addr_un->sun_path, strerror(errno));
187 /* Send blocking read request to PRNGD */
191 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
192 if (errno == EPIPE && errors < 10) {
197 error("Couldn't write to PRNGD socket: %s",
202 if (atomicio(read, fd, buf, len) != (size_t)len) {
203 if (errno == EPIPE && errors < 10) {
208 error("Couldn't read from PRNGD socket: %s",
215 mysignal(SIGPIPE, old_sigpipe);
222 seed_from_prngd(unsigned char *buf, size_t bytes)
225 debug("trying egd/prngd port %d", PRNGD_PORT);
226 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
230 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
231 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
238 stir_gettimeofday(double entropy_estimate)
242 if (gettimeofday(&tv, NULL) == -1)
243 fatal("Couldn't gettimeofday: %s", strerror(errno));
245 RAND_add(&tv, sizeof(tv), entropy_estimate);
247 return entropy_estimate;
251 stir_clock(double entropy_estimate)
257 RAND_add(&c, sizeof(c), entropy_estimate);
259 return entropy_estimate;
260 #else /* _HAVE_CLOCK */
262 #endif /* _HAVE_CLOCK */
266 stir_rusage(int who, double entropy_estimate)
268 #ifdef HAVE_GETRUSAGE
271 if (getrusage(who, &ru) == -1)
274 RAND_add(&ru, sizeof(ru), entropy_estimate);
276 return entropy_estimate;
277 #else /* _HAVE_GETRUSAGE */
279 #endif /* _HAVE_GETRUSAGE */
283 timeval_diff(struct timeval *t1, struct timeval *t2)
285 int secdiff, usecdiff;
287 secdiff = t2->tv_sec - t1->tv_sec;
288 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
289 return (int)(usecdiff / 1000);
293 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
297 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
298 int status, total_bytes_read;
299 static int devnull = -1;
302 struct timeval tv_start, tv_current;
304 debug3("Reading output from \'%s\'", src->cmdstring);
307 devnull = open("/dev/null", O_RDWR);
309 fatal("Couldn't open /dev/null: %s",
314 fatal("Couldn't open pipe: %s", strerror(errno));
316 (void)gettimeofday(&tv_start, NULL); /* record start time */
318 switch (pid = fork()) {
322 fatal("Couldn't fork: %s", strerror(errno));
325 dup2(devnull, STDIN_FILENO);
326 dup2(p[1], STDOUT_FILENO);
327 dup2(p[1], STDERR_FILENO);
332 execv(src->path, (char**)(src->args));
334 debug("(child) Couldn't exec '%s': %s",
335 src->cmdstring, strerror(errno));
337 default: /* Parent */
341 RAND_add(&pid, sizeof(&pid), 0.0);
345 /* Hash output from child */
348 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
349 while (!error_abort && !cmd_eof) {
354 (void) gettimeofday(&tv_current, 0);
355 msec_elapsed = timeval_diff(&tv_start, &tv_current);
356 if (msec_elapsed >= entropy_timeout_current) {
360 msec_remaining = entropy_timeout_current - msec_elapsed;
363 FD_SET(p[0], &rdset);
364 tv.tv_sec = msec_remaining / 1000;
365 tv.tv_usec = (msec_remaining % 1000) * 1000;
367 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
369 RAND_add(&tv, sizeof(tv), 0.0);
380 bytes_read = read(p[0], buf, sizeof(buf));
381 } while (bytes_read == -1 && errno == EINTR);
382 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
383 if (bytes_read == -1) {
386 } else if (bytes_read) {
387 SHA1_Update(&sha, buf, bytes_read);
388 total_bytes_read += bytes_read;
396 debug("Command '%s': select() failed: %s",
397 src->cmdstring, strerror(errno));
403 SHA1_Final(hash, &sha);
407 debug3("Time elapsed: %d msec", msec_elapsed);
409 if (waitpid(pid, &status, 0) == -1) {
410 error("Couldn't wait for child '%s' completion: %s",
411 src->cmdstring, strerror(errno));
415 RAND_add(&status, sizeof(&status), 0.0);
419 * Closing p[0] on timeout causes the entropy command to
420 * SIGPIPE. Take whatever output we got, and mark this
423 debug2("Command '%s' timed out", src->cmdstring);
424 src->sticky_badness *= 2;
425 src->badness = src->sticky_badness;
426 return total_bytes_read;
429 if (WIFEXITED(status)) {
430 if (WEXITSTATUS(status) == 0) {
431 return total_bytes_read;
433 debug2("Command '%s' exit status was %d",
434 src->cmdstring, WEXITSTATUS(status));
435 src->badness = src->sticky_badness = 128;
438 } else if (WIFSIGNALED(status)) {
439 debug2("Command '%s' returned on uncaught signal %d !",
440 src->cmdstring, status);
441 src->badness = src->sticky_badness = 128;
448 stir_from_system(void)
450 double total_entropy_estimate;
453 total_entropy_estimate = 0;
456 RAND_add(&i, sizeof(i), 0.5);
457 total_entropy_estimate += 0.1;
460 RAND_add(&i, sizeof(i), 0.5);
461 total_entropy_estimate += 0.1;
464 RAND_add(&i, sizeof(i), 0.0);
466 RAND_add(&i, sizeof(i), 0.0);
468 total_entropy_estimate += stir_gettimeofday(1.0);
469 total_entropy_estimate += stir_clock(0.5);
470 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
472 return total_entropy_estimate;
476 stir_from_programs(void)
479 double entropy, total_entropy;
480 unsigned char hash[SHA_DIGEST_LENGTH];
483 for(c = 0; entropy_cmds[c].path != NULL; c++) {
484 if (!entropy_cmds[c].badness) {
485 /* Hash output from command */
486 entropy = hash_command_output(&entropy_cmds[c],
489 /* Scale back estimate by command's rate */
490 entropy *= entropy_cmds[c].rate;
492 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
493 if (entropy > SHA_DIGEST_LENGTH)
494 entropy = SHA_DIGEST_LENGTH;
497 RAND_add(hash, sizeof(hash), entropy);
499 debug3("Got %0.2f bytes of entropy from '%s'",
500 entropy, entropy_cmds[c].cmdstring);
502 total_entropy += entropy;
504 /* Execution time should be a bit unpredictable */
505 total_entropy += stir_gettimeofday(0.05);
506 total_entropy += stir_clock(0.05);
507 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
508 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
510 debug2("Command '%s' disabled (badness %d)",
511 entropy_cmds[c].cmdstring,
512 entropy_cmds[c].badness);
514 if (entropy_cmds[c].badness > 0)
515 entropy_cmds[c].badness--;
519 return total_entropy;
523 * prng seedfile functions
526 prng_check_seedfile(char *filename)
531 * XXX raceable: eg replace seed between this stat and subsequent
532 * open. Not such a problem because we don't really trust the
534 * XXX: use secure path checking as elsewhere in OpenSSH
536 if (lstat(filename, &st) == -1) {
537 /* Give up on hard errors */
539 debug("WARNING: Couldn't stat random seed file "
540 "\"%.100s\": %s", filename, strerror(errno));
545 if (!S_ISREG(st.st_mode))
546 fatal("PRNG seedfile %.100s is not a regular file",
549 /* mode 0600, owned by root or the current user? */
550 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
551 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
552 "owned by uid %li", filename, (long int)getuid());
560 prng_write_seedfile(void)
563 unsigned char seed[SEED_FILE_SIZE];
564 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
568 pw = getpwuid(getuid());
570 fatal("Couldn't get password entry for current user "
571 "(%li): %s", (long int)getuid(), strerror(errno));
573 /* Try to ensure that the parent directory is there */
574 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
576 mkdir(filename, 0700);
578 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
581 strlcpy(tmpseed, filename, sizeof(tmpseed));
582 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
584 fatal("PRNG seed filename too long");
586 if (RAND_bytes(seed, sizeof(seed)) <= 0)
587 fatal("PRNG seed extraction failed");
589 /* Don't care if the seed doesn't exist */
590 prng_check_seedfile(filename);
592 old_umask = umask(0177);
594 if ((fd = mkstemp(tmpseed)) == -1) {
595 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
596 "(%.100s)", tmpseed, strerror(errno));
598 debug("writing PRNG seed to file %.100s", tmpseed);
599 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
603 fatal("problem writing PRNG seedfile %.100s "
604 "(%.100s)", filename, strerror(save_errno));
607 debug("moving temporary PRNG seed to file %.100s", filename);
608 if (rename(tmpseed, filename) == -1) {
611 fatal("problem renaming PRNG seedfile from %.100s "
612 "to %.100s (%.100s)", tmpseed, filename,
613 strerror(save_errno));
620 prng_read_seedfile(void)
623 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
626 pw = getpwuid(getuid());
628 fatal("Couldn't get password entry for current user "
629 "(%li): %s", (long int)getuid(), strerror(errno));
631 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
634 debug("loading PRNG seed from file %.100s", filename);
636 if (!prng_check_seedfile(filename)) {
637 verbose("Random seed file not found or invalid, ignoring.");
641 /* open the file and read in the seed */
642 fd = open(filename, O_RDONLY);
644 fatal("could not open PRNG seedfile %.100s (%.100s)",
645 filename, strerror(errno));
647 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
648 verbose("invalid or short read from PRNG seedfile "
649 "%.100s - ignoring", filename);
650 memset(seed, '\0', sizeof(seed));
654 /* stir in the seed, with estimated entropy zero */
655 RAND_add(&seed, sizeof(seed), 0.0);
660 * entropy command initialisation functions
663 prng_read_commands(char *cmdfilename)
665 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
667 entropy_cmd_t *entcmd;
669 int cur_cmd, linenum, num_cmds, arg;
671 if ((f = fopen(cmdfilename, "r")) == NULL) {
672 fatal("couldn't read entropy commands file %.100s: %.100s",
673 cmdfilename, strerror(errno));
677 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
678 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
681 cur_cmd = linenum = 0;
682 while (fgets(line, sizeof(line), f)) {
685 /* Skip leading whitespace, blank lines and comments */
686 cp = line + strspn(line, WHITESPACE);
687 if ((*cp == 0) || (*cp == '#'))
688 continue; /* done with this line */
691 * The first non-whitespace char should be a double quote
692 * delimiting the commandline
695 error("bad entropy command, %.100s line %d",
696 cmdfilename, linenum);
701 * First token, command args (incl. argv[0]) in double
704 cp = strtok(cp, "\"");
706 error("missing or bad command string, %.100s "
707 "line %d -- ignored", cmdfilename, linenum);
710 strlcpy(cmd, cp, sizeof(cmd));
712 /* Second token, full command path */
713 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
714 error("missing command path, %.100s "
715 "line %d -- ignored", cmdfilename, linenum);
719 /* Did configure mark this as dead? */
720 if (strncmp("undef", cp, 5) == 0)
723 strlcpy(path, cp, sizeof(path));
725 /* Third token, entropy rate estimate for this command */
726 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
727 error("missing entropy estimate, %.100s "
728 "line %d -- ignored", cmdfilename, linenum);
731 est = strtod(cp, NULL);
734 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
735 error("garbage at end of line %d in %.100s "
736 "-- ignored", linenum, cmdfilename);
740 /* save the command for debug messages */
741 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
743 /* split the command args */
744 cp = strtok(cmd, WHITESPACE);
747 entcmd[cur_cmd].args[arg] = xstrdup(cp);
749 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
751 if (strtok(NULL, WHITESPACE))
752 error("ignored extra commands (max %d), %.100s "
753 "line %d", NUM_ARGS, cmdfilename, linenum);
755 /* Copy the command path and rate estimate */
756 entcmd[cur_cmd].path = xstrdup(path);
757 entcmd[cur_cmd].rate = est;
759 /* Initialise other values */
760 entcmd[cur_cmd].sticky_badness = 1;
765 * If we've filled the array, reallocate it twice the size
766 * Do this now because even if this we're on the last
767 * command we need another slot to mark the last entry
769 if (cur_cmd == num_cmds) {
771 entcmd = xrealloc(entcmd, num_cmds *
772 sizeof(entropy_cmd_t));
776 /* zero the last entry */
777 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
780 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
781 sizeof(entropy_cmd_t));
783 debug("Loaded %d entropy commands from %.100s", cur_cmd,
786 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
792 fprintf(stderr, "Usage: %s [options]\n", __progname);
793 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
794 fprintf(stderr, " Multiple -v increases verbosity.\n");
795 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
796 fprintf(stderr, " -X Force output in binary\n");
797 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
802 main(int argc, char **argv)
805 int ret, ch, debug_level, output_hex, bytes;
809 __progname = ssh_get_progname(argv[0]);
810 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
812 ll = SYSLOG_LEVEL_INFO;
813 debug_level = output_hex = 0;
814 bytes = OUTPUT_SEED_SIZE;
816 /* Don't write binary data to a tty, unless we are forced to */
817 if (isatty(STDOUT_FILENO))
820 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
824 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
833 if ((bytes = atoi(optarg)) <= 0)
834 fatal("Invalid number of output bytes");
840 error("Invalid commandline option");
845 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
847 #ifdef USE_SEED_FILES
848 prng_read_seedfile();
851 buf = xmalloc(bytes);
854 * Seed the RNG from wherever we can
857 /* Take whatever is on the stack, but don't credit it */
858 RAND_add(buf, bytes, 0);
860 debug("Seeded RNG with %i bytes from system calls",
861 (int)stir_from_system());
863 /* try prngd, fall back to commands if prngd fails or not configured */
864 if (seed_from_prngd(buf, bytes) == 0) {
865 RAND_add(buf, bytes, bytes);
867 /* Read in collection commands */
868 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
869 fatal("PRNG initialisation failed -- exiting.");
870 debug("Seeded RNG with %i bytes from programs",
871 (int)stir_from_programs());
874 #ifdef USE_SEED_FILES
875 prng_write_seedfile();
879 * Write the seed to stdout
883 fatal("Not enough entropy in RNG");
885 if (RAND_bytes(buf, bytes) <= 0)
886 fatal("Couldn't extract entropy from PRNG");
889 for(ret = 0; ret < bytes; ret++)
890 printf("%02x", (unsigned char)(buf[ret]));
893 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
895 memset(buf, '\0', bytes);
898 return ret == bytes ? 0 : 1;
902 * We may attempt to re-seed during mkstemp if we are using the one in the
903 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
904 * need our own seed_rng(). We must also check that we have enough entropy.
910 fatal("Not enough entropy in RNG");