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 */
62 #ifndef SSH_PRNG_COMMAND_FILE
63 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
66 extern char *__progname;
68 #define WHITESPACE " \t\n"
71 # define RUSAGE_SELF 0
73 #ifndef RUSAGE_CHILDREN
74 # define RUSAGE_CHILDREN 0
77 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
78 # define USE_SEED_FILES
82 /* Proportion of data that is entropy */
84 /* Counter goes positive if this command times out */
86 /* Increases by factor of two each timeout */
87 unsigned int sticky_badness;
88 /* Path to executable */
90 /* argv to pass to executable */
91 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
92 /* full command string (debug) */
96 /* slow command timeouts (all in milliseconds) */
97 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
98 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
100 /* this is initialised from a file, by prng_read_commands() */
101 static entropy_cmd_t *entropy_cmds = NULL;
104 double stir_from_system(void);
105 double stir_from_programs(void);
106 double stir_gettimeofday(double entropy_estimate);
107 double stir_clock(double entropy_estimate);
108 double stir_rusage(int who, double entropy_estimate);
109 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
110 int get_random_bytes_prngd(unsigned char *buf, int len,
111 unsigned short tcp_port, char *socket_path);
114 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
115 * listening either on 'tcp_port', or via Unix domain socket at *
117 * Either a non-zero tcp_port or a non-null socket_path must be
119 * Returns 0 on success, -1 on error
122 get_random_bytes_prngd(unsigned char *buf, int len,
123 unsigned short tcp_port, char *socket_path)
125 int fd, addr_len, rval, errors;
127 struct sockaddr_storage addr;
128 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
129 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
133 if (socket_path == NULL && tcp_port == 0)
134 fatal("You must specify a port or a socket");
135 if (socket_path != NULL &&
136 strlen(socket_path) >= sizeof(addr_un->sun_path))
137 fatal("Random pool path is too long");
139 fatal("Too many bytes to read from PRNGD");
141 memset(&addr, '\0', sizeof(addr));
144 addr_in->sin_family = AF_INET;
145 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
146 addr_in->sin_port = htons(tcp_port);
147 addr_len = sizeof(*addr_in);
149 addr_un->sun_family = AF_UNIX;
150 strlcpy(addr_un->sun_path, socket_path,
151 sizeof(addr_un->sun_path));
152 addr_len = offsetof(struct sockaddr_un, sun_path) +
153 strlen(socket_path) + 1;
156 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
161 fd = socket(addr.ss_family, SOCK_STREAM, 0);
163 error("Couldn't create socket: %s", strerror(errno));
167 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
169 error("Couldn't connect to PRNGD port %d: %s",
170 tcp_port, strerror(errno));
172 error("Couldn't connect to PRNGD socket \"%s\": %s",
173 addr_un->sun_path, strerror(errno));
178 /* Send blocking read request to PRNGD */
182 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
183 if (errno == EPIPE && errors < 10) {
188 error("Couldn't write to PRNGD socket: %s",
193 if (atomicio(read, fd, buf, len) != len) {
194 if (errno == EPIPE && errors < 10) {
199 error("Couldn't read from PRNGD socket: %s",
206 mysignal(SIGPIPE, old_sigpipe);
213 stir_gettimeofday(double entropy_estimate)
217 if (gettimeofday(&tv, NULL) == -1)
218 fatal("Couldn't gettimeofday: %s", strerror(errno));
220 RAND_add(&tv, sizeof(tv), entropy_estimate);
222 return entropy_estimate;
226 stir_clock(double entropy_estimate)
232 RAND_add(&c, sizeof(c), entropy_estimate);
234 return entropy_estimate;
235 #else /* _HAVE_CLOCK */
237 #endif /* _HAVE_CLOCK */
241 stir_rusage(int who, double entropy_estimate)
243 #ifdef HAVE_GETRUSAGE
246 if (getrusage(who, &ru) == -1)
249 RAND_add(&ru, sizeof(ru), entropy_estimate);
251 return entropy_estimate;
252 #else /* _HAVE_GETRUSAGE */
254 #endif /* _HAVE_GETRUSAGE */
258 timeval_diff(struct timeval *t1, struct timeval *t2)
260 int secdiff, usecdiff;
262 secdiff = t2->tv_sec - t1->tv_sec;
263 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
264 return (int)(usecdiff / 1000);
268 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
272 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
273 int status, total_bytes_read;
274 static int devnull = -1;
277 struct timeval tv_start, tv_current;
279 debug3("Reading output from \'%s\'", src->cmdstring);
282 devnull = open("/dev/null", O_RDWR);
284 fatal("Couldn't open /dev/null: %s",
289 fatal("Couldn't open pipe: %s", strerror(errno));
291 (void)gettimeofday(&tv_start, NULL); /* record start time */
293 switch (pid = fork()) {
297 fatal("Couldn't fork: %s", strerror(errno));
300 dup2(devnull, STDIN_FILENO);
301 dup2(p[1], STDOUT_FILENO);
302 dup2(p[1], STDERR_FILENO);
307 execv(src->path, (char**)(src->args));
309 debug("(child) Couldn't exec '%s': %s",
310 src->cmdstring, strerror(errno));
312 default: /* Parent */
316 RAND_add(&pid, sizeof(&pid), 0.0);
320 /* Hash output from child */
323 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
324 while (!error_abort && !cmd_eof) {
329 (void) gettimeofday(&tv_current, 0);
330 msec_elapsed = timeval_diff(&tv_start, &tv_current);
331 if (msec_elapsed >= entropy_timeout_current) {
335 msec_remaining = entropy_timeout_current - msec_elapsed;
338 FD_SET(p[0], &rdset);
339 tv.tv_sec = msec_remaining / 1000;
340 tv.tv_usec = (msec_remaining % 1000) * 1000;
342 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
344 RAND_add(&tv, sizeof(tv), 0.0);
355 bytes_read = read(p[0], buf, sizeof(buf));
356 } while (bytes_read == -1 && errno == EINTR);
357 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
358 if (bytes_read == -1) {
361 } else if (bytes_read) {
362 SHA1_Update(&sha, buf, bytes_read);
363 total_bytes_read += bytes_read;
371 debug("Command '%s': select() failed: %s",
372 src->cmdstring, strerror(errno));
378 SHA1_Final(hash, &sha);
382 debug3("Time elapsed: %d msec", msec_elapsed);
384 if (waitpid(pid, &status, 0) == -1) {
385 error("Couldn't wait for child '%s' completion: %s",
386 src->cmdstring, strerror(errno));
390 RAND_add(&status, sizeof(&status), 0.0);
394 * Closing p[0] on timeout causes the entropy command to
395 * SIGPIPE. Take whatever output we got, and mark this
398 debug2("Command '%s' timed out", src->cmdstring);
399 src->sticky_badness *= 2;
400 src->badness = src->sticky_badness;
401 return total_bytes_read;
404 if (WIFEXITED(status)) {
405 if (WEXITSTATUS(status) == 0) {
406 return total_bytes_read;
408 debug2("Command '%s' exit status was %d",
409 src->cmdstring, WEXITSTATUS(status));
410 src->badness = src->sticky_badness = 128;
413 } else if (WIFSIGNALED(status)) {
414 debug2("Command '%s' returned on uncaught signal %d !",
415 src->cmdstring, status);
416 src->badness = src->sticky_badness = 128;
423 stir_from_system(void)
425 double total_entropy_estimate;
428 total_entropy_estimate = 0;
431 RAND_add(&i, sizeof(i), 0.5);
432 total_entropy_estimate += 0.1;
435 RAND_add(&i, sizeof(i), 0.5);
436 total_entropy_estimate += 0.1;
439 RAND_add(&i, sizeof(i), 0.0);
441 RAND_add(&i, sizeof(i), 0.0);
443 total_entropy_estimate += stir_gettimeofday(1.0);
444 total_entropy_estimate += stir_clock(0.5);
445 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
447 return total_entropy_estimate;
451 stir_from_programs(void)
454 double entropy, total_entropy;
455 unsigned char hash[SHA_DIGEST_LENGTH];
458 for(c = 0; entropy_cmds[c].path != NULL; c++) {
459 if (!entropy_cmds[c].badness) {
460 /* Hash output from command */
461 entropy = hash_command_output(&entropy_cmds[c],
464 /* Scale back estimate by command's rate */
465 entropy *= entropy_cmds[c].rate;
467 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
468 if (entropy > SHA_DIGEST_LENGTH)
469 entropy = SHA_DIGEST_LENGTH;
472 RAND_add(hash, sizeof(hash), entropy);
474 debug3("Got %0.2f bytes of entropy from '%s'",
475 entropy, entropy_cmds[c].cmdstring);
477 total_entropy += entropy;
479 /* Execution time should be a bit unpredictable */
480 total_entropy += stir_gettimeofday(0.05);
481 total_entropy += stir_clock(0.05);
482 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
483 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
485 debug2("Command '%s' disabled (badness %d)",
486 entropy_cmds[c].cmdstring,
487 entropy_cmds[c].badness);
489 if (entropy_cmds[c].badness > 0)
490 entropy_cmds[c].badness--;
494 return total_entropy;
498 * prng seedfile functions
501 prng_check_seedfile(char *filename)
506 * XXX raceable: eg replace seed between this stat and subsequent
507 * open. Not such a problem because we don't really trust the
509 * XXX: use secure path checking as elsewhere in OpenSSH
511 if (lstat(filename, &st) == -1) {
512 /* Give up on hard errors */
514 debug("WARNING: Couldn't stat random seed file "
515 "\"%.100s\": %s", filename, strerror(errno));
520 if (!S_ISREG(st.st_mode))
521 fatal("PRNG seedfile %.100s is not a regular file",
524 /* mode 0600, owned by root or the current user? */
525 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
526 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
527 "owned by uid %li", filename, (long int)getuid());
535 prng_write_seedfile(void)
538 unsigned char seed[SEED_FILE_SIZE];
539 char filename[MAXPATHLEN];
542 pw = getpwuid(getuid());
544 fatal("Couldn't get password entry for current user "
545 "(%li): %s", (long int)getuid(), strerror(errno));
547 /* Try to ensure that the parent directory is there */
548 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
550 mkdir(filename, 0700);
552 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
555 debug("writing PRNG seed to file %.100s", filename);
557 if (RAND_bytes(seed, sizeof(seed)) <= 0)
558 fatal("PRNG seed extraction failed");
560 /* Don't care if the seed doesn't exist */
561 prng_check_seedfile(filename);
563 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
564 debug("WARNING: couldn't access PRNG seedfile %.100s "
565 "(%.100s)", filename, strerror(errno));
567 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed))
568 fatal("problem writing PRNG seedfile %.100s "
569 "(%.100s)", filename, strerror(errno));
575 prng_read_seedfile(void)
578 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
581 pw = getpwuid(getuid());
583 fatal("Couldn't get password entry for current user "
584 "(%li): %s", (long int)getuid(), strerror(errno));
586 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
589 debug("loading PRNG seed from file %.100s", filename);
591 if (!prng_check_seedfile(filename)) {
592 verbose("Random seed file not found or invalid, ignoring.");
596 /* open the file and read in the seed */
597 fd = open(filename, O_RDONLY);
599 fatal("could not open PRNG seedfile %.100s (%.100s)",
600 filename, strerror(errno));
602 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
603 verbose("invalid or short read from PRNG seedfile "
604 "%.100s - ignoring", filename);
605 memset(seed, '\0', sizeof(seed));
609 /* stir in the seed, with estimated entropy zero */
610 RAND_add(&seed, sizeof(seed), 0.0);
615 * entropy command initialisation functions
618 prng_read_commands(char *cmdfilename)
620 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
622 entropy_cmd_t *entcmd;
624 int cur_cmd, linenum, num_cmds, arg;
626 if ((f = fopen(cmdfilename, "r")) == NULL) {
627 fatal("couldn't read entropy commands file %.100s: %.100s",
628 cmdfilename, strerror(errno));
632 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
633 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
636 cur_cmd = linenum = 0;
637 while (fgets(line, sizeof(line), f)) {
640 /* Skip leading whitespace, blank lines and comments */
641 cp = line + strspn(line, WHITESPACE);
642 if ((*cp == 0) || (*cp == '#'))
643 continue; /* done with this line */
646 * The first non-whitespace char should be a double quote
647 * delimiting the commandline
650 error("bad entropy command, %.100s line %d",
651 cmdfilename, linenum);
656 * First token, command args (incl. argv[0]) in double
659 cp = strtok(cp, "\"");
661 error("missing or bad command string, %.100s "
662 "line %d -- ignored", cmdfilename, linenum);
665 strlcpy(cmd, cp, sizeof(cmd));
667 /* Second token, full command path */
668 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
669 error("missing command path, %.100s "
670 "line %d -- ignored", cmdfilename, linenum);
674 /* Did configure mark this as dead? */
675 if (strncmp("undef", cp, 5) == 0)
678 strlcpy(path, cp, sizeof(path));
680 /* Third token, entropy rate estimate for this command */
681 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
682 error("missing entropy estimate, %.100s "
683 "line %d -- ignored", cmdfilename, linenum);
686 est = strtod(cp, NULL);
689 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
690 error("garbage at end of line %d in %.100s "
691 "-- ignored", linenum, cmdfilename);
695 /* save the command for debug messages */
696 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
698 /* split the command args */
699 cp = strtok(cmd, WHITESPACE);
702 entcmd[cur_cmd].args[arg] = xstrdup(cp);
704 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
706 if (strtok(NULL, WHITESPACE))
707 error("ignored extra commands (max %d), %.100s "
708 "line %d", NUM_ARGS, cmdfilename, linenum);
710 /* Copy the command path and rate estimate */
711 entcmd[cur_cmd].path = xstrdup(path);
712 entcmd[cur_cmd].rate = est;
714 /* Initialise other values */
715 entcmd[cur_cmd].sticky_badness = 1;
720 * If we've filled the array, reallocate it twice the size
721 * Do this now because even if this we're on the last
722 * command we need another slot to mark the last entry
724 if (cur_cmd == num_cmds) {
726 entcmd = xrealloc(entcmd, num_cmds *
727 sizeof(entropy_cmd_t));
731 /* zero the last entry */
732 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
735 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
736 sizeof(entropy_cmd_t));
738 debug("Loaded %d entropy commands from %.100s", cur_cmd,
741 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
747 fprintf(stderr, "Usage: %s [options]\n", __progname);
748 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
749 fprintf(stderr, " Multiple -v increases verbosity.\n");
750 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
751 fprintf(stderr, " -X Force output in binary\n");
752 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
757 main(int argc, char **argv)
760 int ret, ch, debug_level, output_hex, bytes;
764 __progname = ssh_get_progname(argv[0]);
765 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
767 ll = SYSLOG_LEVEL_INFO;
768 debug_level = output_hex = 0;
769 bytes = OUTPUT_SEED_SIZE;
771 /* Don't write binary data to a tty, unless we are forced to */
772 if (isatty(STDOUT_FILENO))
775 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
779 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
788 if ((bytes = atoi(optarg)) <= 0)
789 fatal("Invalid number of output bytes");
795 error("Invalid commandline option");
800 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
802 #ifdef USE_SEED_FILES
803 prng_read_seedfile();
806 buf = xmalloc(bytes);
809 * Seed the RNG from wherever we can
812 /* Take whatever is on the stack, but don't credit it */
813 RAND_add(buf, bytes, 0);
815 debug("Seeded RNG with %i bytes from system calls",
816 (int)stir_from_system());
819 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == -1)
820 fatal("Entropy collection failed");
821 RAND_add(buf, bytes, bytes);
822 #elif defined(PRNGD_SOCKET)
823 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == -1)
824 fatal("Entropy collection failed");
825 RAND_add(buf, bytes, bytes);
827 /* Read in collection commands */
828 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
829 fatal("PRNG initialisation failed -- exiting.");
830 debug("Seeded RNG with %i bytes from programs",
831 (int)stir_from_programs());
834 #ifdef USE_SEED_FILES
835 prng_write_seedfile();
839 * Write the seed to stdout
843 fatal("Not enough entropy in RNG");
845 if (RAND_bytes(buf, bytes) <= 0)
846 fatal("Couldn't extract entropy from PRNG");
849 for(ret = 0; ret < bytes; ret++)
850 printf("%02x", (unsigned char)(buf[ret]));
853 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
855 memset(buf, '\0', bytes);
858 return ret == bytes ? 0 : 1;