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>
31 #include <sys/socket.h>
34 #include <netinet/in.h>
45 #include <openssl/rand.h>
46 #include <openssl/sha.h>
47 #include <openssl/crypto.h>
49 /* SunOS 4.4.4 needs this */
50 #ifdef HAVE_FLOATINGPOINT_H
51 # include <floatingpoint.h>
52 #endif /* HAVE_FLOATINGPOINT_H */
57 #include "pathnames.h"
60 /* Number of bytes we write out */
61 #define OUTPUT_SEED_SIZE 48
63 /* Length of on-disk seedfiles */
64 #define SEED_FILE_SIZE 1024
66 /* Maximum number of command-line arguments to read from file */
69 /* Minimum number of usable commands to be considered sufficient */
70 #define MIN_ENTROPY_SOURCES 16
72 /* Path to on-disk seed file (relative to user's home directory */
73 #ifndef SSH_PRNG_SEED_FILE
74 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
77 /* Path to PRNG commands list */
78 #ifndef SSH_PRNG_COMMAND_FILE
79 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
82 extern char *__progname;
84 #define WHITESPACE " \t\n"
87 # define RUSAGE_SELF 0
89 #ifndef RUSAGE_CHILDREN
90 # define RUSAGE_CHILDREN 0
93 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
94 # define USE_SEED_FILES
98 /* Proportion of data that is entropy */
100 /* Counter goes positive if this command times out */
101 unsigned int badness;
102 /* Increases by factor of two each timeout */
103 unsigned int sticky_badness;
104 /* Path to executable */
106 /* argv to pass to executable */
107 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
108 /* full command string (debug) */
112 /* slow command timeouts (all in milliseconds) */
113 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
114 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
116 /* this is initialised from a file, by prng_read_commands() */
117 static entropy_cmd_t *entropy_cmds = NULL;
120 double stir_from_system(void);
121 double stir_from_programs(void);
122 double stir_gettimeofday(double entropy_estimate);
123 double stir_clock(double entropy_estimate);
124 double stir_rusage(int who, double entropy_estimate);
125 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
126 int get_random_bytes_prngd(unsigned char *buf, int len,
127 unsigned short tcp_port, char *socket_path);
130 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
131 * listening either on 'tcp_port', or via Unix domain socket at *
133 * Either a non-zero tcp_port or a non-null socket_path must be
135 * Returns 0 on success, -1 on error
138 get_random_bytes_prngd(unsigned char *buf, int len,
139 unsigned short tcp_port, char *socket_path)
141 int fd, addr_len, rval, errors;
143 struct sockaddr_storage addr;
144 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
145 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
149 if (socket_path == NULL && tcp_port == 0)
150 fatal("You must specify a port or a socket");
151 if (socket_path != NULL &&
152 strlen(socket_path) >= sizeof(addr_un->sun_path))
153 fatal("Random pool path is too long");
154 if (len <= 0 || len > 255)
155 fatal("Too many bytes (%d) to read from PRNGD", len);
157 memset(&addr, '\0', sizeof(addr));
160 addr_in->sin_family = AF_INET;
161 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
162 addr_in->sin_port = htons(tcp_port);
163 addr_len = sizeof(*addr_in);
165 addr_un->sun_family = AF_UNIX;
166 strlcpy(addr_un->sun_path, socket_path,
167 sizeof(addr_un->sun_path));
168 addr_len = offsetof(struct sockaddr_un, sun_path) +
169 strlen(socket_path) + 1;
172 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
177 fd = socket(addr.ss_family, SOCK_STREAM, 0);
179 error("Couldn't create socket: %s", strerror(errno));
183 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
185 error("Couldn't connect to PRNGD port %d: %s",
186 tcp_port, strerror(errno));
188 error("Couldn't connect to PRNGD socket \"%s\": %s",
189 addr_un->sun_path, strerror(errno));
194 /* Send blocking read request to PRNGD */
198 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
199 if (errno == EPIPE && errors < 10) {
204 error("Couldn't write to PRNGD socket: %s",
209 if (atomicio(read, fd, buf, len) != (size_t)len) {
210 if (errno == EPIPE && errors < 10) {
215 error("Couldn't read from PRNGD socket: %s",
222 mysignal(SIGPIPE, old_sigpipe);
229 seed_from_prngd(unsigned char *buf, size_t bytes)
232 debug("trying egd/prngd port %d", PRNGD_PORT);
233 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
237 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
238 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
245 stir_gettimeofday(double entropy_estimate)
249 if (gettimeofday(&tv, NULL) == -1)
250 fatal("Couldn't gettimeofday: %s", strerror(errno));
252 RAND_add(&tv, sizeof(tv), entropy_estimate);
254 return entropy_estimate;
258 stir_clock(double entropy_estimate)
264 RAND_add(&c, sizeof(c), entropy_estimate);
266 return entropy_estimate;
267 #else /* _HAVE_CLOCK */
269 #endif /* _HAVE_CLOCK */
273 stir_rusage(int who, double entropy_estimate)
275 #ifdef HAVE_GETRUSAGE
278 if (getrusage(who, &ru) == -1)
281 RAND_add(&ru, sizeof(ru), entropy_estimate);
283 return entropy_estimate;
284 #else /* _HAVE_GETRUSAGE */
286 #endif /* _HAVE_GETRUSAGE */
290 timeval_diff(struct timeval *t1, struct timeval *t2)
292 int secdiff, usecdiff;
294 secdiff = t2->tv_sec - t1->tv_sec;
295 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
296 return (int)(usecdiff / 1000);
300 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
304 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
305 int status, total_bytes_read;
306 static int devnull = -1;
309 struct timeval tv_start, tv_current;
311 debug3("Reading output from \'%s\'", src->cmdstring);
314 devnull = open("/dev/null", O_RDWR);
316 fatal("Couldn't open /dev/null: %s",
321 fatal("Couldn't open pipe: %s", strerror(errno));
323 (void)gettimeofday(&tv_start, NULL); /* record start time */
325 switch (pid = fork()) {
329 fatal("Couldn't fork: %s", strerror(errno));
332 dup2(devnull, STDIN_FILENO);
333 dup2(p[1], STDOUT_FILENO);
334 dup2(p[1], STDERR_FILENO);
339 execv(src->path, (char**)(src->args));
341 debug("(child) Couldn't exec '%s': %s",
342 src->cmdstring, strerror(errno));
344 default: /* Parent */
348 RAND_add(&pid, sizeof(&pid), 0.0);
352 /* Hash output from child */
355 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
356 while (!error_abort && !cmd_eof) {
361 (void) gettimeofday(&tv_current, 0);
362 msec_elapsed = timeval_diff(&tv_start, &tv_current);
363 if (msec_elapsed >= entropy_timeout_current) {
367 msec_remaining = entropy_timeout_current - msec_elapsed;
370 FD_SET(p[0], &rdset);
371 tv.tv_sec = msec_remaining / 1000;
372 tv.tv_usec = (msec_remaining % 1000) * 1000;
374 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
376 RAND_add(&tv, sizeof(tv), 0.0);
387 bytes_read = read(p[0], buf, sizeof(buf));
388 } while (bytes_read == -1 && errno == EINTR);
389 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
390 if (bytes_read == -1) {
393 } else if (bytes_read) {
394 SHA1_Update(&sha, buf, bytes_read);
395 total_bytes_read += bytes_read;
403 debug("Command '%s': select() failed: %s",
404 src->cmdstring, strerror(errno));
410 SHA1_Final(hash, &sha);
414 debug3("Time elapsed: %d msec", msec_elapsed);
416 if (waitpid(pid, &status, 0) == -1) {
417 error("Couldn't wait for child '%s' completion: %s",
418 src->cmdstring, strerror(errno));
422 RAND_add(&status, sizeof(&status), 0.0);
426 * Closing p[0] on timeout causes the entropy command to
427 * SIGPIPE. Take whatever output we got, and mark this
430 debug2("Command '%s' timed out", src->cmdstring);
431 src->sticky_badness *= 2;
432 src->badness = src->sticky_badness;
433 return total_bytes_read;
436 if (WIFEXITED(status)) {
437 if (WEXITSTATUS(status) == 0) {
438 return total_bytes_read;
440 debug2("Command '%s' exit status was %d",
441 src->cmdstring, WEXITSTATUS(status));
442 src->badness = src->sticky_badness = 128;
445 } else if (WIFSIGNALED(status)) {
446 debug2("Command '%s' returned on uncaught signal %d !",
447 src->cmdstring, status);
448 src->badness = src->sticky_badness = 128;
455 stir_from_system(void)
457 double total_entropy_estimate;
460 total_entropy_estimate = 0;
463 RAND_add(&i, sizeof(i), 0.5);
464 total_entropy_estimate += 0.1;
467 RAND_add(&i, sizeof(i), 0.5);
468 total_entropy_estimate += 0.1;
471 RAND_add(&i, sizeof(i), 0.0);
473 RAND_add(&i, sizeof(i), 0.0);
475 total_entropy_estimate += stir_gettimeofday(1.0);
476 total_entropy_estimate += stir_clock(0.5);
477 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
479 return total_entropy_estimate;
483 stir_from_programs(void)
486 double entropy, total_entropy;
487 unsigned char hash[SHA_DIGEST_LENGTH];
490 for(c = 0; entropy_cmds[c].path != NULL; c++) {
491 if (!entropy_cmds[c].badness) {
492 /* Hash output from command */
493 entropy = hash_command_output(&entropy_cmds[c],
496 /* Scale back estimate by command's rate */
497 entropy *= entropy_cmds[c].rate;
499 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
500 if (entropy > SHA_DIGEST_LENGTH)
501 entropy = SHA_DIGEST_LENGTH;
504 RAND_add(hash, sizeof(hash), entropy);
506 debug3("Got %0.2f bytes of entropy from '%s'",
507 entropy, entropy_cmds[c].cmdstring);
509 total_entropy += entropy;
511 /* Execution time should be a bit unpredictable */
512 total_entropy += stir_gettimeofday(0.05);
513 total_entropy += stir_clock(0.05);
514 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
515 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
517 debug2("Command '%s' disabled (badness %d)",
518 entropy_cmds[c].cmdstring,
519 entropy_cmds[c].badness);
521 if (entropy_cmds[c].badness > 0)
522 entropy_cmds[c].badness--;
526 return total_entropy;
530 * prng seedfile functions
533 prng_check_seedfile(char *filename)
538 * XXX raceable: eg replace seed between this stat and subsequent
539 * open. Not such a problem because we don't really trust the
541 * XXX: use secure path checking as elsewhere in OpenSSH
543 if (lstat(filename, &st) == -1) {
544 /* Give up on hard errors */
546 debug("WARNING: Couldn't stat random seed file "
547 "\"%.100s\": %s", filename, strerror(errno));
552 if (!S_ISREG(st.st_mode))
553 fatal("PRNG seedfile %.100s is not a regular file",
556 /* mode 0600, owned by root or the current user? */
557 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
558 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
559 "owned by uid %li", filename, (long int)getuid());
567 prng_write_seedfile(void)
570 unsigned char seed[SEED_FILE_SIZE];
571 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
575 pw = getpwuid(getuid());
577 fatal("Couldn't get password entry for current user "
578 "(%li): %s", (long int)getuid(), strerror(errno));
580 /* Try to ensure that the parent directory is there */
581 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
583 if (mkdir(filename, 0700) < 0 && errno != EEXIST)
584 fatal("mkdir %.200s: %s", filename, strerror(errno));
586 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
589 strlcpy(tmpseed, filename, sizeof(tmpseed));
590 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
592 fatal("PRNG seed filename too long");
594 if (RAND_bytes(seed, sizeof(seed)) <= 0)
595 fatal("PRNG seed extraction failed");
597 /* Don't care if the seed doesn't exist */
598 prng_check_seedfile(filename);
600 old_umask = umask(0177);
602 if ((fd = mkstemp(tmpseed)) == -1) {
603 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
604 "(%.100s)", tmpseed, strerror(errno));
606 debug("writing PRNG seed to file %.100s", tmpseed);
607 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
611 fatal("problem writing PRNG seedfile %.100s "
612 "(%.100s)", filename, strerror(save_errno));
615 debug("moving temporary PRNG seed to file %.100s", filename);
616 if (rename(tmpseed, filename) == -1) {
619 fatal("problem renaming PRNG seedfile from %.100s "
620 "to %.100s (%.100s)", tmpseed, filename,
621 strerror(save_errno));
628 prng_read_seedfile(void)
631 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
634 pw = getpwuid(getuid());
636 fatal("Couldn't get password entry for current user "
637 "(%li): %s", (long int)getuid(), strerror(errno));
639 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
642 debug("loading PRNG seed from file %.100s", filename);
644 if (!prng_check_seedfile(filename)) {
645 verbose("Random seed file not found or invalid, ignoring.");
649 /* open the file and read in the seed */
650 fd = open(filename, O_RDONLY);
652 fatal("could not open PRNG seedfile %.100s (%.100s)",
653 filename, strerror(errno));
655 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
656 verbose("invalid or short read from PRNG seedfile "
657 "%.100s - ignoring", filename);
658 memset(seed, '\0', sizeof(seed));
662 /* stir in the seed, with estimated entropy zero */
663 RAND_add(&seed, sizeof(seed), 0.0);
668 * entropy command initialisation functions
671 prng_read_commands(char *cmdfilename)
673 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
675 entropy_cmd_t *entcmd;
677 int cur_cmd, linenum, num_cmds, arg;
679 if ((f = fopen(cmdfilename, "r")) == NULL) {
680 fatal("couldn't read entropy commands file %.100s: %.100s",
681 cmdfilename, strerror(errno));
685 entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
688 cur_cmd = linenum = 0;
689 while (fgets(line, sizeof(line), f)) {
692 /* Skip leading whitespace, blank lines and comments */
693 cp = line + strspn(line, WHITESPACE);
694 if ((*cp == 0) || (*cp == '#'))
695 continue; /* done with this line */
698 * The first non-whitespace char should be a double quote
699 * delimiting the commandline
702 error("bad entropy command, %.100s line %d",
703 cmdfilename, linenum);
708 * First token, command args (incl. argv[0]) in double
711 cp = strtok(cp, "\"");
713 error("missing or bad command string, %.100s "
714 "line %d -- ignored", cmdfilename, linenum);
717 strlcpy(cmd, cp, sizeof(cmd));
719 /* Second token, full command path */
720 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
721 error("missing command path, %.100s "
722 "line %d -- ignored", cmdfilename, linenum);
726 /* Did configure mark this as dead? */
727 if (strncmp("undef", cp, 5) == 0)
730 strlcpy(path, cp, sizeof(path));
732 /* Third token, entropy rate estimate for this command */
733 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
734 error("missing entropy estimate, %.100s "
735 "line %d -- ignored", cmdfilename, linenum);
738 est = strtod(cp, NULL);
741 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
742 error("garbage at end of line %d in %.100s "
743 "-- ignored", linenum, cmdfilename);
747 /* save the command for debug messages */
748 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
750 /* split the command args */
751 cp = strtok(cmd, WHITESPACE);
754 entcmd[cur_cmd].args[arg] = xstrdup(cp);
756 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
758 if (strtok(NULL, WHITESPACE))
759 error("ignored extra commands (max %d), %.100s "
760 "line %d", NUM_ARGS, 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;
772 * If we've filled the array, reallocate it twice the size
773 * Do this now because even if this we're on the last
774 * command we need another slot to mark the last entry
776 if (cur_cmd == num_cmds) {
778 entcmd = xrealloc(entcmd, num_cmds,
779 sizeof(entropy_cmd_t));
783 /* zero the last entry */
784 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
787 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
788 sizeof(entropy_cmd_t));
790 debug("Loaded %d entropy commands from %.100s", cur_cmd,
794 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
800 fprintf(stderr, "Usage: %s [options]\n", __progname);
801 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
802 fprintf(stderr, " Multiple -v increases verbosity.\n");
803 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
804 fprintf(stderr, " -X Force output in binary\n");
805 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
810 main(int argc, char **argv)
813 int ret, ch, debug_level, output_hex, bytes;
817 __progname = ssh_get_progname(argv[0]);
818 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
820 ll = SYSLOG_LEVEL_INFO;
821 debug_level = output_hex = 0;
822 bytes = OUTPUT_SEED_SIZE;
824 /* Don't write binary data to a tty, unless we are forced to */
825 if (isatty(STDOUT_FILENO))
828 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
832 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
841 if ((bytes = atoi(optarg)) <= 0)
842 fatal("Invalid number of output bytes");
848 error("Invalid commandline option");
853 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
855 #ifdef USE_SEED_FILES
856 prng_read_seedfile();
859 buf = xmalloc(bytes);
862 * Seed the RNG from wherever we can
865 /* Take whatever is on the stack, but don't credit it */
866 RAND_add(buf, bytes, 0);
868 debug("Seeded RNG with %i bytes from system calls",
869 (int)stir_from_system());
871 /* try prngd, fall back to commands if prngd fails or not configured */
872 if (seed_from_prngd(buf, bytes) == 0) {
873 RAND_add(buf, bytes, bytes);
875 /* Read in collection commands */
876 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
877 fatal("PRNG initialisation failed -- exiting.");
878 debug("Seeded RNG with %i bytes from programs",
879 (int)stir_from_programs());
882 #ifdef USE_SEED_FILES
883 prng_write_seedfile();
887 * Write the seed to stdout
891 fatal("Not enough entropy in RNG");
893 if (RAND_bytes(buf, bytes) <= 0)
894 fatal("Couldn't extract entropy from PRNG");
897 for(ret = 0; ret < bytes; ret++)
898 printf("%02x", (unsigned char)(buf[ret]));
901 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
903 memset(buf, '\0', bytes);
906 return ret == bytes ? 0 : 1;
910 * We may attempt to re-seed during mkstemp if we are using the one in the
911 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
912 * need our own seed_rng(). We must also check that we have enough entropy.
918 fatal("Not enough entropy in RNG");