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 <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 */
39 #include "pathnames.h"
44 /* Number of bytes we write out */
45 #define OUTPUT_SEED_SIZE 48
47 /* Length of on-disk seedfiles */
48 #define SEED_FILE_SIZE 1024
50 /* Maximum number of command-line arguments to read from file */
53 /* Minimum number of usable commands to be considered sufficient */
54 #define MIN_ENTROPY_SOURCES 16
56 /* Path to on-disk seed file (relative to user's home directory */
57 #ifndef SSH_PRNG_SEED_FILE
58 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
61 /* Path to PRNG commands list (from pathnames.c) */
62 extern char *SSH_PRNG_COMMAND_FILE;
64 #ifdef HAVE___PROGNAME
65 extern char *__progname;
71 # define offsetof(type, member) ((size_t) &((type *)0)->member)
74 #define WHITESPACE " \t\n"
77 # define RUSAGE_SELF 0
79 #ifndef RUSAGE_CHILDREN
80 # define RUSAGE_CHILDREN 0
83 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
84 # define USE_SEED_FILES
88 /* Proportion of data that is entropy */
90 /* Counter goes positive if this command times out */
92 /* Increases by factor of two each timeout */
93 unsigned int sticky_badness;
94 /* Path to executable */
96 /* argv to pass to executable */
97 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
98 /* full command string (debug) */
102 /* slow command timeouts (all in milliseconds) */
103 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
104 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
106 /* this is initialised from a file, by prng_read_commands() */
107 static entropy_cmd_t *entropy_cmds = NULL;
110 double stir_from_system(void);
111 double stir_from_programs(void);
112 double stir_gettimeofday(double entropy_estimate);
113 double stir_clock(double entropy_estimate);
114 double stir_rusage(int who, double entropy_estimate);
115 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
116 int get_random_bytes_prngd(unsigned char *buf, int len,
117 unsigned short tcp_port, char *socket_path);
120 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
121 * listening either on 'tcp_port', or via Unix domain socket at *
123 * Either a non-zero tcp_port or a non-null socket_path must be
125 * Returns 0 on success, -1 on error
128 get_random_bytes_prngd(unsigned char *buf, int len,
129 unsigned short tcp_port, char *socket_path)
131 int fd, addr_len, rval, errors;
133 struct sockaddr_storage addr;
134 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
135 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
139 if (socket_path == NULL && tcp_port == 0)
140 fatal("You must specify a port or a socket");
141 if (socket_path != NULL &&
142 strlen(socket_path) >= sizeof(addr_un->sun_path))
143 fatal("Random pool path is too long");
145 fatal("Too many bytes to read from PRNGD");
147 memset(&addr, '\0', sizeof(addr));
150 addr_in->sin_family = AF_INET;
151 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
152 addr_in->sin_port = htons(tcp_port);
153 addr_len = sizeof(*addr_in);
155 addr_un->sun_family = AF_UNIX;
156 strlcpy(addr_un->sun_path, socket_path,
157 sizeof(addr_un->sun_path));
158 addr_len = offsetof(struct sockaddr_un, sun_path) +
159 strlen(socket_path) + 1;
162 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
167 fd = socket(addr.ss_family, SOCK_STREAM, 0);
169 error("Couldn't create socket: %s", strerror(errno));
173 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
175 error("Couldn't connect to PRNGD port %d: %s",
176 tcp_port, strerror(errno));
178 error("Couldn't connect to PRNGD socket \"%s\": %s",
179 addr_un->sun_path, strerror(errno));
184 /* Send blocking read request to PRNGD */
188 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
189 if (errno == EPIPE && errors < 10) {
194 error("Couldn't write to PRNGD socket: %s",
199 if (atomicio(read, fd, buf, len) != len) {
200 if (errno == EPIPE && errors < 10) {
205 error("Couldn't read from PRNGD socket: %s",
212 mysignal(SIGPIPE, old_sigpipe);
219 stir_gettimeofday(double entropy_estimate)
223 if (gettimeofday(&tv, NULL) == -1)
224 fatal("Couldn't gettimeofday: %s", strerror(errno));
226 RAND_add(&tv, sizeof(tv), entropy_estimate);
228 return entropy_estimate;
232 stir_clock(double entropy_estimate)
238 RAND_add(&c, sizeof(c), entropy_estimate);
240 return entropy_estimate;
241 #else /* _HAVE_CLOCK */
243 #endif /* _HAVE_CLOCK */
247 stir_rusage(int who, double entropy_estimate)
249 #ifdef HAVE_GETRUSAGE
252 if (getrusage(who, &ru) == -1)
255 RAND_add(&ru, sizeof(ru), entropy_estimate);
257 return entropy_estimate;
258 #else /* _HAVE_GETRUSAGE */
260 #endif /* _HAVE_GETRUSAGE */
264 timeval_diff(struct timeval *t1, struct timeval *t2)
266 int secdiff, usecdiff;
268 secdiff = t2->tv_sec - t1->tv_sec;
269 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
270 return (int)(usecdiff / 1000);
274 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
278 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
279 int status, total_bytes_read;
280 static int devnull = -1;
283 struct timeval tv_start, tv_current;
285 debug3("Reading output from \'%s\'", src->cmdstring);
288 devnull = open("/dev/null", O_RDWR);
290 fatal("Couldn't open /dev/null: %s",
295 fatal("Couldn't open pipe: %s", strerror(errno));
297 (void)gettimeofday(&tv_start, NULL); /* record start time */
299 switch (pid = fork()) {
303 fatal("Couldn't fork: %s", strerror(errno));
306 dup2(devnull, STDIN_FILENO);
307 dup2(p[1], STDOUT_FILENO);
308 dup2(p[1], STDERR_FILENO);
313 execv(src->path, (char**)(src->args));
315 debug("(child) Couldn't exec '%s': %s",
316 src->cmdstring, strerror(errno));
318 default: /* Parent */
322 RAND_add(&pid, sizeof(&pid), 0.0);
326 /* Hash output from child */
329 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
330 while (!error_abort && !cmd_eof) {
335 (void) gettimeofday(&tv_current, 0);
336 msec_elapsed = timeval_diff(&tv_start, &tv_current);
337 if (msec_elapsed >= entropy_timeout_current) {
341 msec_remaining = entropy_timeout_current - msec_elapsed;
344 FD_SET(p[0], &rdset);
345 tv.tv_sec = msec_remaining / 1000;
346 tv.tv_usec = (msec_remaining % 1000) * 1000;
348 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
350 RAND_add(&tv, sizeof(tv), 0.0);
361 bytes_read = read(p[0], buf, sizeof(buf));
362 } while (bytes_read == -1 && errno == EINTR);
363 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
364 if (bytes_read == -1) {
367 } else if (bytes_read) {
368 SHA1_Update(&sha, buf, bytes_read);
369 total_bytes_read += bytes_read;
377 debug("Command '%s': select() failed: %s",
378 src->cmdstring, strerror(errno));
384 SHA1_Final(hash, &sha);
388 debug3("Time elapsed: %d msec", msec_elapsed);
390 if (waitpid(pid, &status, 0) == -1) {
391 error("Couldn't wait for child '%s' completion: %s",
392 src->cmdstring, strerror(errno));
396 RAND_add(&status, sizeof(&status), 0.0);
400 * Closing p[0] on timeout causes the entropy command to
401 * SIGPIPE. Take whatever output we got, and mark this
404 debug2("Command '%s' timed out", src->cmdstring);
405 src->sticky_badness *= 2;
406 src->badness = src->sticky_badness;
407 return total_bytes_read;
410 if (WIFEXITED(status)) {
411 if (WEXITSTATUS(status) == 0) {
412 return total_bytes_read;
414 debug2("Command '%s' exit status was %d",
415 src->cmdstring, WEXITSTATUS(status));
416 src->badness = src->sticky_badness = 128;
419 } else if (WIFSIGNALED(status)) {
420 debug2("Command '%s' returned on uncaught signal %d !",
421 src->cmdstring, status);
422 src->badness = src->sticky_badness = 128;
429 stir_from_system(void)
431 double total_entropy_estimate;
434 total_entropy_estimate = 0;
437 RAND_add(&i, sizeof(i), 0.5);
438 total_entropy_estimate += 0.1;
441 RAND_add(&i, sizeof(i), 0.5);
442 total_entropy_estimate += 0.1;
445 RAND_add(&i, sizeof(i), 0.0);
447 RAND_add(&i, sizeof(i), 0.0);
449 total_entropy_estimate += stir_gettimeofday(1.0);
450 total_entropy_estimate += stir_clock(0.5);
451 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
453 return total_entropy_estimate;
457 stir_from_programs(void)
460 double entropy, total_entropy;
461 unsigned char hash[SHA_DIGEST_LENGTH];
464 for(c = 0; entropy_cmds[c].path != NULL; c++) {
465 if (!entropy_cmds[c].badness) {
466 /* Hash output from command */
467 entropy = hash_command_output(&entropy_cmds[c],
470 /* Scale back estimate by command's rate */
471 entropy *= entropy_cmds[c].rate;
473 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
474 if (entropy > SHA_DIGEST_LENGTH)
475 entropy = SHA_DIGEST_LENGTH;
478 RAND_add(hash, sizeof(hash), entropy);
480 debug3("Got %0.2f bytes of entropy from '%s'",
481 entropy, entropy_cmds[c].cmdstring);
483 total_entropy += entropy;
485 /* Execution time should be a bit unpredictable */
486 total_entropy += stir_gettimeofday(0.05);
487 total_entropy += stir_clock(0.05);
488 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
489 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
491 debug2("Command '%s' disabled (badness %d)",
492 entropy_cmds[c].cmdstring,
493 entropy_cmds[c].badness);
495 if (entropy_cmds[c].badness > 0)
496 entropy_cmds[c].badness--;
500 return total_entropy;
504 * prng seedfile functions
507 prng_check_seedfile(char *filename)
512 * XXX raceable: eg replace seed between this stat and subsequent
513 * open. Not such a problem because we don't really trust the
515 * XXX: use secure path checking as elsewhere in OpenSSH
517 if (lstat(filename, &st) == -1) {
518 /* Give up on hard errors */
520 debug("WARNING: Couldn't stat random seed file "
521 "\"%.100s\": %s", filename, strerror(errno));
526 if (!S_ISREG(st.st_mode))
527 fatal("PRNG seedfile %.100s is not a regular file",
530 /* mode 0600, owned by root or the current user? */
531 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
532 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
533 "owned by uid %li", filename, (long int)getuid());
541 prng_write_seedfile(void)
544 unsigned char seed[SEED_FILE_SIZE];
545 char filename[MAXPATHLEN];
548 pw = getpwuid(getuid());
550 fatal("Couldn't get password entry for current user "
551 "(%li): %s", (long int)getuid(), strerror(errno));
553 /* Try to ensure that the parent directory is there */
554 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
556 mkdir(filename, 0700);
558 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
561 debug("writing PRNG seed to file %.100s", filename);
563 if (RAND_bytes(seed, sizeof(seed)) <= 0)
564 fatal("PRNG seed extraction failed");
566 /* Don't care if the seed doesn't exist */
567 prng_check_seedfile(filename);
569 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
570 debug("WARNING: couldn't access PRNG seedfile %.100s "
571 "(%.100s)", filename, strerror(errno));
573 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed))
574 fatal("problem writing PRNG seedfile %.100s "
575 "(%.100s)", filename, strerror(errno));
581 prng_read_seedfile(void)
584 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
587 pw = getpwuid(getuid());
589 fatal("Couldn't get password entry for current user "
590 "(%li): %s", (long int)getuid(), strerror(errno));
592 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
595 debug("loading PRNG seed from file %.100s", filename);
597 if (!prng_check_seedfile(filename)) {
598 verbose("Random seed file not found or invalid, ignoring.");
602 /* open the file and read in the seed */
603 fd = open(filename, O_RDONLY);
605 fatal("could not open PRNG seedfile %.100s (%.100s)",
606 filename, strerror(errno));
608 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
609 verbose("invalid or short read from PRNG seedfile "
610 "%.100s - ignoring", filename);
611 memset(seed, '\0', sizeof(seed));
615 /* stir in the seed, with estimated entropy zero */
616 RAND_add(&seed, sizeof(seed), 0.0);
621 * entropy command initialisation functions
624 prng_read_commands(char *cmdfilename)
626 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
628 entropy_cmd_t *entcmd;
630 int cur_cmd, linenum, num_cmds, arg;
632 if ((f = fopen(cmdfilename, "r")) == NULL) {
633 fatal("couldn't read entropy commands file %.100s: %.100s",
634 cmdfilename, strerror(errno));
638 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
639 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
642 cur_cmd = linenum = 0;
643 while (fgets(line, sizeof(line), f)) {
646 /* Skip leading whitespace, blank lines and comments */
647 cp = line + strspn(line, WHITESPACE);
648 if ((*cp == 0) || (*cp == '#'))
649 continue; /* done with this line */
652 * The first non-whitespace char should be a double quote
653 * delimiting the commandline
656 error("bad entropy command, %.100s line %d",
657 cmdfilename, linenum);
662 * First token, command args (incl. argv[0]) in double
665 cp = strtok(cp, "\"");
667 error("missing or bad command string, %.100s "
668 "line %d -- ignored", cmdfilename, linenum);
671 strlcpy(cmd, cp, sizeof(cmd));
673 /* Second token, full command path */
674 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
675 error("missing command path, %.100s "
676 "line %d -- ignored", cmdfilename, linenum);
680 /* Did configure mark this as dead? */
681 if (strncmp("undef", cp, 5) == 0)
684 strlcpy(path, cp, sizeof(path));
686 /* Third token, entropy rate estimate for this command */
687 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
688 error("missing entropy estimate, %.100s "
689 "line %d -- ignored", cmdfilename, linenum);
692 est = strtod(cp, NULL);
695 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
696 error("garbage at end of line %d in %.100s "
697 "-- ignored", linenum, cmdfilename);
701 /* save the command for debug messages */
702 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
704 /* split the command args */
705 cp = strtok(cmd, WHITESPACE);
708 entcmd[cur_cmd].args[arg] = xstrdup(cp);
710 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
712 if (strtok(NULL, WHITESPACE))
713 error("ignored extra commands (max %d), %.100s "
714 "line %d", NUM_ARGS, cmdfilename, linenum);
716 /* Copy the command path and rate estimate */
717 entcmd[cur_cmd].path = xstrdup(path);
718 entcmd[cur_cmd].rate = est;
720 /* Initialise other values */
721 entcmd[cur_cmd].sticky_badness = 1;
726 * If we've filled the array, reallocate it twice the size
727 * Do this now because even if this we're on the last
728 * command we need another slot to mark the last entry
730 if (cur_cmd == num_cmds) {
732 entcmd = xrealloc(entcmd, num_cmds *
733 sizeof(entropy_cmd_t));
737 /* zero the last entry */
738 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
741 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
742 sizeof(entropy_cmd_t));
744 debug("Loaded %d entropy commands from %.100s", cur_cmd,
747 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
753 fprintf(stderr, "Usage: %s [options]\n", __progname);
754 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
755 fprintf(stderr, " Multiple -v increases verbosity.\n");
756 fprintf(stderr, " -x Force output in hexidecimal (for debugging)\n");
757 fprintf(stderr, " -X Force output in binary\n");
758 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
763 main(int argc, char **argv)
766 int ret, ch, debug_level, output_hex, bytes;
770 __progname = ssh_get_progname(argv[0]);
772 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
774 ll = SYSLOG_LEVEL_INFO;
775 debug_level = output_hex = 0;
776 bytes = OUTPUT_SEED_SIZE;
778 /* Don't write binary data to a tty, unless we are forced to */
779 if (isatty(STDOUT_FILENO))
782 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
786 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
795 if ((bytes = atoi(optarg)) <= 0)
796 fatal("Invalid number of output bytes");
802 error("Invalid commandline option");
807 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
809 #ifdef USE_SEED_FILES
810 prng_read_seedfile();
813 buf = xmalloc(bytes);
816 * Seed the RNG from wherever we can
819 /* Take whatever is on the stack, but don't credit it */
820 RAND_add(buf, bytes, 0);
822 debug("Seeded RNG with %i bytes from system calls",
823 (int)stir_from_system());
826 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == -1)
827 fatal("Entropy collection failed");
828 RAND_add(buf, bytes, bytes);
829 #elif defined(PRNGD_SOCKET)
830 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == -1)
831 fatal("Entropy collection failed");
832 RAND_add(buf, bytes, bytes);
834 /* Read in collection commands */
835 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
836 fatal("PRNG initialisation failed -- exiting.");
837 debug("Seeded RNG with %i bytes from programs",
838 (int)stir_from_programs());
841 #ifdef USE_SEED_FILES
842 prng_write_seedfile();
846 * Write the seed to stdout
850 fatal("Not enough entropy in RNG");
852 if (RAND_bytes(buf, bytes) <= 0)
853 fatal("Couldn't extract entropy from PRNG");
856 for(ret = 0; ret < bytes; ret++)
857 printf("%02x", (unsigned char)(buf[ret]));
860 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
862 memset(buf, '\0', bytes);
865 return ret == bytes ? 0 : 1;