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>
36 #include <netinet/in.h>
37 #include <arpa/inet.h>
50 #include <openssl/rand.h>
51 #include <openssl/sha.h>
52 #include <openssl/crypto.h>
54 /* SunOS 4.4.4 needs this */
55 #ifdef HAVE_FLOATINGPOINT_H
56 # include <floatingpoint.h>
57 #endif /* HAVE_FLOATINGPOINT_H */
62 #include "pathnames.h"
65 /* Number of bytes we write out */
66 #define OUTPUT_SEED_SIZE 48
68 /* Length of on-disk seedfiles */
69 #define SEED_FILE_SIZE 1024
71 /* Maximum number of command-line arguments to read from file */
74 /* Minimum number of usable commands to be considered sufficient */
75 #define MIN_ENTROPY_SOURCES 16
77 /* Path to on-disk seed file (relative to user's home directory */
78 #ifndef SSH_PRNG_SEED_FILE
79 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
82 /* Path to PRNG commands list */
83 #ifndef SSH_PRNG_COMMAND_FILE
84 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
87 extern char *__progname;
89 #define WHITESPACE " \t\n"
92 # define RUSAGE_SELF 0
94 #ifndef RUSAGE_CHILDREN
95 # define RUSAGE_CHILDREN 0
98 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
99 # define USE_SEED_FILES
103 /* Proportion of data that is entropy */
105 /* Counter goes positive if this command times out */
106 unsigned int badness;
107 /* Increases by factor of two each timeout */
108 unsigned int sticky_badness;
109 /* Path to executable */
111 /* argv to pass to executable */
112 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
113 /* full command string (debug) */
117 /* slow command timeouts (all in milliseconds) */
118 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
119 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
121 /* this is initialised from a file, by prng_read_commands() */
122 static entropy_cmd_t *entropy_cmds = NULL;
125 double stir_from_system(void);
126 double stir_from_programs(void);
127 double stir_gettimeofday(double entropy_estimate);
128 double stir_clock(double entropy_estimate);
129 double stir_rusage(int who, double entropy_estimate);
130 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
131 int get_random_bytes_prngd(unsigned char *buf, int len,
132 unsigned short tcp_port, char *socket_path);
135 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
136 * listening either on 'tcp_port', or via Unix domain socket at *
138 * Either a non-zero tcp_port or a non-null socket_path must be
140 * Returns 0 on success, -1 on error
143 get_random_bytes_prngd(unsigned char *buf, int len,
144 unsigned short tcp_port, char *socket_path)
146 int fd, addr_len, rval, errors;
148 struct sockaddr_storage addr;
149 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
150 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
154 if (socket_path == NULL && tcp_port == 0)
155 fatal("You must specify a port or a socket");
156 if (socket_path != NULL &&
157 strlen(socket_path) >= sizeof(addr_un->sun_path))
158 fatal("Random pool path is too long");
159 if (len <= 0 || len > 255)
160 fatal("Too many bytes (%d) to read from PRNGD", len);
162 memset(&addr, '\0', sizeof(addr));
165 addr_in->sin_family = AF_INET;
166 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
167 addr_in->sin_port = htons(tcp_port);
168 addr_len = sizeof(*addr_in);
170 addr_un->sun_family = AF_UNIX;
171 strlcpy(addr_un->sun_path, socket_path,
172 sizeof(addr_un->sun_path));
173 addr_len = offsetof(struct sockaddr_un, sun_path) +
174 strlen(socket_path) + 1;
177 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
182 fd = socket(addr.ss_family, SOCK_STREAM, 0);
184 error("Couldn't create socket: %s", strerror(errno));
188 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
190 error("Couldn't connect to PRNGD port %d: %s",
191 tcp_port, strerror(errno));
193 error("Couldn't connect to PRNGD socket \"%s\": %s",
194 addr_un->sun_path, strerror(errno));
199 /* Send blocking read request to PRNGD */
203 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
204 if (errno == EPIPE && errors < 10) {
209 error("Couldn't write to PRNGD socket: %s",
214 if (atomicio(read, fd, buf, len) != (size_t)len) {
215 if (errno == EPIPE && errors < 10) {
220 error("Couldn't read from PRNGD socket: %s",
227 mysignal(SIGPIPE, old_sigpipe);
234 seed_from_prngd(unsigned char *buf, size_t bytes)
237 debug("trying egd/prngd port %d", PRNGD_PORT);
238 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
242 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
243 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
250 stir_gettimeofday(double entropy_estimate)
254 if (gettimeofday(&tv, NULL) == -1)
255 fatal("Couldn't gettimeofday: %s", strerror(errno));
257 RAND_add(&tv, sizeof(tv), entropy_estimate);
259 return entropy_estimate;
263 stir_clock(double entropy_estimate)
269 RAND_add(&c, sizeof(c), entropy_estimate);
271 return entropy_estimate;
272 #else /* _HAVE_CLOCK */
274 #endif /* _HAVE_CLOCK */
278 stir_rusage(int who, double entropy_estimate)
280 #ifdef HAVE_GETRUSAGE
283 if (getrusage(who, &ru) == -1)
286 RAND_add(&ru, sizeof(ru), entropy_estimate);
288 return entropy_estimate;
289 #else /* _HAVE_GETRUSAGE */
291 #endif /* _HAVE_GETRUSAGE */
295 timeval_diff(struct timeval *t1, struct timeval *t2)
297 int secdiff, usecdiff;
299 secdiff = t2->tv_sec - t1->tv_sec;
300 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
301 return (int)(usecdiff / 1000);
305 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
309 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
310 int status, total_bytes_read;
311 static int devnull = -1;
314 struct timeval tv_start, tv_current;
316 debug3("Reading output from \'%s\'", src->cmdstring);
319 devnull = open("/dev/null", O_RDWR);
321 fatal("Couldn't open /dev/null: %s",
326 fatal("Couldn't open pipe: %s", strerror(errno));
328 (void)gettimeofday(&tv_start, NULL); /* record start time */
330 switch (pid = fork()) {
334 fatal("Couldn't fork: %s", strerror(errno));
337 dup2(devnull, STDIN_FILENO);
338 dup2(p[1], STDOUT_FILENO);
339 dup2(p[1], STDERR_FILENO);
344 execv(src->path, (char**)(src->args));
346 debug("(child) Couldn't exec '%s': %s",
347 src->cmdstring, strerror(errno));
349 default: /* Parent */
353 RAND_add(&pid, sizeof(&pid), 0.0);
357 /* Hash output from child */
360 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
361 while (!error_abort && !cmd_eof) {
366 (void) gettimeofday(&tv_current, 0);
367 msec_elapsed = timeval_diff(&tv_start, &tv_current);
368 if (msec_elapsed >= entropy_timeout_current) {
372 msec_remaining = entropy_timeout_current - msec_elapsed;
375 FD_SET(p[0], &rdset);
376 tv.tv_sec = msec_remaining / 1000;
377 tv.tv_usec = (msec_remaining % 1000) * 1000;
379 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
381 RAND_add(&tv, sizeof(tv), 0.0);
392 bytes_read = read(p[0], buf, sizeof(buf));
393 } while (bytes_read == -1 && errno == EINTR);
394 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
395 if (bytes_read == -1) {
398 } else if (bytes_read) {
399 SHA1_Update(&sha, buf, bytes_read);
400 total_bytes_read += bytes_read;
408 debug("Command '%s': select() failed: %s",
409 src->cmdstring, strerror(errno));
415 SHA1_Final(hash, &sha);
419 debug3("Time elapsed: %d msec", msec_elapsed);
421 if (waitpid(pid, &status, 0) == -1) {
422 error("Couldn't wait for child '%s' completion: %s",
423 src->cmdstring, strerror(errno));
427 RAND_add(&status, sizeof(&status), 0.0);
431 * Closing p[0] on timeout causes the entropy command to
432 * SIGPIPE. Take whatever output we got, and mark this
435 debug2("Command '%s' timed out", src->cmdstring);
436 src->sticky_badness *= 2;
437 src->badness = src->sticky_badness;
438 return total_bytes_read;
441 if (WIFEXITED(status)) {
442 if (WEXITSTATUS(status) == 0) {
443 return total_bytes_read;
445 debug2("Command '%s' exit status was %d",
446 src->cmdstring, WEXITSTATUS(status));
447 src->badness = src->sticky_badness = 128;
450 } else if (WIFSIGNALED(status)) {
451 debug2("Command '%s' returned on uncaught signal %d !",
452 src->cmdstring, status);
453 src->badness = src->sticky_badness = 128;
460 stir_from_system(void)
462 double total_entropy_estimate;
465 total_entropy_estimate = 0;
468 RAND_add(&i, sizeof(i), 0.5);
469 total_entropy_estimate += 0.1;
472 RAND_add(&i, sizeof(i), 0.5);
473 total_entropy_estimate += 0.1;
476 RAND_add(&i, sizeof(i), 0.0);
478 RAND_add(&i, sizeof(i), 0.0);
480 total_entropy_estimate += stir_gettimeofday(1.0);
481 total_entropy_estimate += stir_clock(0.5);
482 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
484 return total_entropy_estimate;
488 stir_from_programs(void)
491 double entropy, total_entropy;
492 unsigned char hash[SHA_DIGEST_LENGTH];
495 for(c = 0; entropy_cmds[c].path != NULL; c++) {
496 if (!entropy_cmds[c].badness) {
497 /* Hash output from command */
498 entropy = hash_command_output(&entropy_cmds[c],
501 /* Scale back estimate by command's rate */
502 entropy *= entropy_cmds[c].rate;
504 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
505 if (entropy > SHA_DIGEST_LENGTH)
506 entropy = SHA_DIGEST_LENGTH;
509 RAND_add(hash, sizeof(hash), entropy);
511 debug3("Got %0.2f bytes of entropy from '%s'",
512 entropy, entropy_cmds[c].cmdstring);
514 total_entropy += entropy;
516 /* Execution time should be a bit unpredictable */
517 total_entropy += stir_gettimeofday(0.05);
518 total_entropy += stir_clock(0.05);
519 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
520 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
522 debug2("Command '%s' disabled (badness %d)",
523 entropy_cmds[c].cmdstring,
524 entropy_cmds[c].badness);
526 if (entropy_cmds[c].badness > 0)
527 entropy_cmds[c].badness--;
531 return total_entropy;
535 * prng seedfile functions
538 prng_check_seedfile(char *filename)
543 * XXX raceable: eg replace seed between this stat and subsequent
544 * open. Not such a problem because we don't really trust the
546 * XXX: use secure path checking as elsewhere in OpenSSH
548 if (lstat(filename, &st) == -1) {
549 /* Give up on hard errors */
551 debug("WARNING: Couldn't stat random seed file "
552 "\"%.100s\": %s", filename, strerror(errno));
557 if (!S_ISREG(st.st_mode))
558 fatal("PRNG seedfile %.100s is not a regular file",
561 /* mode 0600, owned by root or the current user? */
562 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
563 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
564 "owned by uid %li", filename, (long int)getuid());
572 prng_write_seedfile(void)
575 unsigned char seed[SEED_FILE_SIZE];
576 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
580 pw = getpwuid(getuid());
582 fatal("Couldn't get password entry for current user "
583 "(%li): %s", (long int)getuid(), strerror(errno));
585 /* Try to ensure that the parent directory is there */
586 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
588 if (mkdir(filename, 0700) < 0 && errno != EEXIST)
589 fatal("mkdir %.200s: %s", filename, strerror(errno));
591 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
594 strlcpy(tmpseed, filename, sizeof(tmpseed));
595 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
597 fatal("PRNG seed filename too long");
599 if (RAND_bytes(seed, sizeof(seed)) <= 0)
600 fatal("PRNG seed extraction failed");
602 /* Don't care if the seed doesn't exist */
603 prng_check_seedfile(filename);
605 old_umask = umask(0177);
607 if ((fd = mkstemp(tmpseed)) == -1) {
608 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
609 "(%.100s)", tmpseed, strerror(errno));
611 debug("writing PRNG seed to file %.100s", tmpseed);
612 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
616 fatal("problem writing PRNG seedfile %.100s "
617 "(%.100s)", filename, strerror(save_errno));
620 debug("moving temporary PRNG seed to file %.100s", filename);
621 if (rename(tmpseed, filename) == -1) {
624 fatal("problem renaming PRNG seedfile from %.100s "
625 "to %.100s (%.100s)", tmpseed, filename,
626 strerror(save_errno));
633 prng_read_seedfile(void)
636 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
639 pw = getpwuid(getuid());
641 fatal("Couldn't get password entry for current user "
642 "(%li): %s", (long int)getuid(), strerror(errno));
644 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
647 debug("loading PRNG seed from file %.100s", filename);
649 if (!prng_check_seedfile(filename)) {
650 verbose("Random seed file not found or invalid, ignoring.");
654 /* open the file and read in the seed */
655 fd = open(filename, O_RDONLY);
657 fatal("could not open PRNG seedfile %.100s (%.100s)",
658 filename, strerror(errno));
660 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
661 verbose("invalid or short read from PRNG seedfile "
662 "%.100s - ignoring", filename);
663 memset(seed, '\0', sizeof(seed));
667 /* stir in the seed, with estimated entropy zero */
668 RAND_add(&seed, sizeof(seed), 0.0);
673 * entropy command initialisation functions
676 prng_read_commands(char *cmdfilename)
678 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
680 entropy_cmd_t *entcmd;
682 int cur_cmd, linenum, num_cmds, arg;
684 if ((f = fopen(cmdfilename, "r")) == NULL) {
685 fatal("couldn't read entropy commands file %.100s: %.100s",
686 cmdfilename, strerror(errno));
690 entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
693 cur_cmd = linenum = 0;
694 while (fgets(line, sizeof(line), f)) {
697 /* Skip leading whitespace, blank lines and comments */
698 cp = line + strspn(line, WHITESPACE);
699 if ((*cp == 0) || (*cp == '#'))
700 continue; /* done with this line */
703 * The first non-whitespace char should be a double quote
704 * delimiting the commandline
707 error("bad entropy command, %.100s line %d",
708 cmdfilename, linenum);
713 * First token, command args (incl. argv[0]) in double
716 cp = strtok(cp, "\"");
718 error("missing or bad command string, %.100s "
719 "line %d -- ignored", cmdfilename, linenum);
722 strlcpy(cmd, cp, sizeof(cmd));
724 /* Second token, full command path */
725 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
726 error("missing command path, %.100s "
727 "line %d -- ignored", cmdfilename, linenum);
731 /* Did configure mark this as dead? */
732 if (strncmp("undef", cp, 5) == 0)
735 strlcpy(path, cp, sizeof(path));
737 /* Third token, entropy rate estimate for this command */
738 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
739 error("missing entropy estimate, %.100s "
740 "line %d -- ignored", cmdfilename, linenum);
743 est = strtod(cp, NULL);
746 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
747 error("garbage at end of line %d in %.100s "
748 "-- ignored", linenum, cmdfilename);
752 /* save the command for debug messages */
753 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
755 /* split the command args */
756 cp = strtok(cmd, WHITESPACE);
759 entcmd[cur_cmd].args[arg] = xstrdup(cp);
761 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
763 if (strtok(NULL, WHITESPACE))
764 error("ignored extra commands (max %d), %.100s "
765 "line %d", NUM_ARGS, cmdfilename, linenum);
767 /* Copy the command path and rate estimate */
768 entcmd[cur_cmd].path = xstrdup(path);
769 entcmd[cur_cmd].rate = est;
771 /* Initialise other values */
772 entcmd[cur_cmd].sticky_badness = 1;
777 * If we've filled the array, reallocate it twice the size
778 * Do this now because even if this we're on the last
779 * command we need another slot to mark the last entry
781 if (cur_cmd == num_cmds) {
783 entcmd = xrealloc(entcmd, num_cmds,
784 sizeof(entropy_cmd_t));
788 /* zero the last entry */
789 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
792 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
793 sizeof(entropy_cmd_t));
795 debug("Loaded %d entropy commands from %.100s", cur_cmd,
799 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
805 fprintf(stderr, "Usage: %s [options]\n", __progname);
806 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
807 fprintf(stderr, " Multiple -v increases verbosity.\n");
808 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
809 fprintf(stderr, " -X Force output in binary\n");
810 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
815 main(int argc, char **argv)
818 int ret, ch, debug_level, output_hex, bytes;
822 __progname = ssh_get_progname(argv[0]);
823 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
825 ll = SYSLOG_LEVEL_INFO;
826 debug_level = output_hex = 0;
827 bytes = OUTPUT_SEED_SIZE;
829 /* Don't write binary data to a tty, unless we are forced to */
830 if (isatty(STDOUT_FILENO))
833 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
837 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
846 if ((bytes = atoi(optarg)) <= 0)
847 fatal("Invalid number of output bytes");
853 error("Invalid commandline option");
858 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
860 #ifdef USE_SEED_FILES
861 prng_read_seedfile();
864 buf = xmalloc(bytes);
867 * Seed the RNG from wherever we can
870 /* Take whatever is on the stack, but don't credit it */
871 RAND_add(buf, bytes, 0);
873 debug("Seeded RNG with %i bytes from system calls",
874 (int)stir_from_system());
876 /* try prngd, fall back to commands if prngd fails or not configured */
877 if (seed_from_prngd(buf, bytes) == 0) {
878 RAND_add(buf, bytes, bytes);
880 /* Read in collection commands */
881 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
882 fatal("PRNG initialisation failed -- exiting.");
883 debug("Seeded RNG with %i bytes from programs",
884 (int)stir_from_programs());
887 #ifdef USE_SEED_FILES
888 prng_write_seedfile();
892 * Write the seed to stdout
896 fatal("Not enough entropy in RNG");
898 if (RAND_bytes(buf, bytes) <= 0)
899 fatal("Couldn't extract entropy from PRNG");
902 for(ret = 0; ret < bytes; ret++)
903 printf("%02x", (unsigned char)(buf[ret]));
906 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
908 memset(buf, '\0', bytes);
911 return ret == bytes ? 0 : 1;
915 * We may attempt to re-seed during mkstemp if we are using the one in the
916 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
917 * need our own seed_rng(). We must also check that we have enough entropy.
923 fatal("Not enough entropy in RNG");