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"
55 /* Number of bytes we write out */
56 #define OUTPUT_SEED_SIZE 48
58 /* Length of on-disk seedfiles */
59 #define SEED_FILE_SIZE 1024
61 /* Maximum number of command-line arguments to read from file */
64 /* Minimum number of usable commands to be considered sufficient */
65 #define MIN_ENTROPY_SOURCES 16
67 /* Path to on-disk seed file (relative to user's home directory */
68 #ifndef SSH_PRNG_SEED_FILE
69 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
72 /* Path to PRNG commands list */
73 #ifndef SSH_PRNG_COMMAND_FILE
74 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
77 extern char *__progname;
79 #define WHITESPACE " \t\n"
82 # define RUSAGE_SELF 0
84 #ifndef RUSAGE_CHILDREN
85 # define RUSAGE_CHILDREN 0
88 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
89 # define USE_SEED_FILES
93 /* Proportion of data that is entropy */
95 /* Counter goes positive if this command times out */
97 /* Increases by factor of two each timeout */
98 unsigned int sticky_badness;
99 /* Path to executable */
101 /* argv to pass to executable */
102 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
103 /* full command string (debug) */
107 /* slow command timeouts (all in milliseconds) */
108 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
109 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
111 /* this is initialised from a file, by prng_read_commands() */
112 static entropy_cmd_t *entropy_cmds = NULL;
115 double stir_from_system(void);
116 double stir_from_programs(void);
117 double stir_gettimeofday(double entropy_estimate);
118 double stir_clock(double entropy_estimate);
119 double stir_rusage(int who, double entropy_estimate);
120 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
121 int get_random_bytes_prngd(unsigned char *buf, int len,
122 unsigned short tcp_port, char *socket_path);
125 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
126 * listening either on 'tcp_port', or via Unix domain socket at *
128 * Either a non-zero tcp_port or a non-null socket_path must be
130 * Returns 0 on success, -1 on error
133 get_random_bytes_prngd(unsigned char *buf, int len,
134 unsigned short tcp_port, char *socket_path)
136 int fd, addr_len, rval, errors;
138 struct sockaddr_storage addr;
139 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
140 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
144 if (socket_path == NULL && tcp_port == 0)
145 fatal("You must specify a port or a socket");
146 if (socket_path != NULL &&
147 strlen(socket_path) >= sizeof(addr_un->sun_path))
148 fatal("Random pool path is too long");
149 if (len <= 0 || len > 255)
150 fatal("Too many bytes (%d) to read from PRNGD", len);
152 memset(&addr, '\0', sizeof(addr));
155 addr_in->sin_family = AF_INET;
156 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
157 addr_in->sin_port = htons(tcp_port);
158 addr_len = sizeof(*addr_in);
160 addr_un->sun_family = AF_UNIX;
161 strlcpy(addr_un->sun_path, socket_path,
162 sizeof(addr_un->sun_path));
163 addr_len = offsetof(struct sockaddr_un, sun_path) +
164 strlen(socket_path) + 1;
167 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
172 fd = socket(addr.ss_family, SOCK_STREAM, 0);
174 error("Couldn't create socket: %s", strerror(errno));
178 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
180 error("Couldn't connect to PRNGD port %d: %s",
181 tcp_port, strerror(errno));
183 error("Couldn't connect to PRNGD socket \"%s\": %s",
184 addr_un->sun_path, strerror(errno));
189 /* Send blocking read request to PRNGD */
193 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
194 if (errno == EPIPE && errors < 10) {
199 error("Couldn't write to PRNGD socket: %s",
204 if (atomicio(read, fd, buf, len) != (size_t)len) {
205 if (errno == EPIPE && errors < 10) {
210 error("Couldn't read from PRNGD socket: %s",
217 mysignal(SIGPIPE, old_sigpipe);
224 seed_from_prngd(unsigned char *buf, size_t bytes)
227 debug("trying egd/prngd port %d", PRNGD_PORT);
228 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
232 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
233 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
240 stir_gettimeofday(double entropy_estimate)
244 if (gettimeofday(&tv, NULL) == -1)
245 fatal("Couldn't gettimeofday: %s", strerror(errno));
247 RAND_add(&tv, sizeof(tv), entropy_estimate);
249 return entropy_estimate;
253 stir_clock(double entropy_estimate)
259 RAND_add(&c, sizeof(c), entropy_estimate);
261 return entropy_estimate;
262 #else /* _HAVE_CLOCK */
264 #endif /* _HAVE_CLOCK */
268 stir_rusage(int who, double entropy_estimate)
270 #ifdef HAVE_GETRUSAGE
273 if (getrusage(who, &ru) == -1)
276 RAND_add(&ru, sizeof(ru), entropy_estimate);
278 return entropy_estimate;
279 #else /* _HAVE_GETRUSAGE */
281 #endif /* _HAVE_GETRUSAGE */
285 timeval_diff(struct timeval *t1, struct timeval *t2)
287 int secdiff, usecdiff;
289 secdiff = t2->tv_sec - t1->tv_sec;
290 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
291 return (int)(usecdiff / 1000);
295 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
299 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
300 int status, total_bytes_read;
301 static int devnull = -1;
304 struct timeval tv_start, tv_current;
306 debug3("Reading output from \'%s\'", src->cmdstring);
309 devnull = open("/dev/null", O_RDWR);
311 fatal("Couldn't open /dev/null: %s",
316 fatal("Couldn't open pipe: %s", strerror(errno));
318 (void)gettimeofday(&tv_start, NULL); /* record start time */
320 switch (pid = fork()) {
324 fatal("Couldn't fork: %s", strerror(errno));
327 dup2(devnull, STDIN_FILENO);
328 dup2(p[1], STDOUT_FILENO);
329 dup2(p[1], STDERR_FILENO);
334 execv(src->path, (char**)(src->args));
336 debug("(child) Couldn't exec '%s': %s",
337 src->cmdstring, strerror(errno));
339 default: /* Parent */
343 RAND_add(&pid, sizeof(&pid), 0.0);
347 /* Hash output from child */
350 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
351 while (!error_abort && !cmd_eof) {
356 (void) gettimeofday(&tv_current, 0);
357 msec_elapsed = timeval_diff(&tv_start, &tv_current);
358 if (msec_elapsed >= entropy_timeout_current) {
362 msec_remaining = entropy_timeout_current - msec_elapsed;
365 FD_SET(p[0], &rdset);
366 tv.tv_sec = msec_remaining / 1000;
367 tv.tv_usec = (msec_remaining % 1000) * 1000;
369 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
371 RAND_add(&tv, sizeof(tv), 0.0);
382 bytes_read = read(p[0], buf, sizeof(buf));
383 } while (bytes_read == -1 && errno == EINTR);
384 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
385 if (bytes_read == -1) {
388 } else if (bytes_read) {
389 SHA1_Update(&sha, buf, bytes_read);
390 total_bytes_read += bytes_read;
398 debug("Command '%s': select() failed: %s",
399 src->cmdstring, strerror(errno));
405 SHA1_Final(hash, &sha);
409 debug3("Time elapsed: %d msec", msec_elapsed);
411 if (waitpid(pid, &status, 0) == -1) {
412 error("Couldn't wait for child '%s' completion: %s",
413 src->cmdstring, strerror(errno));
417 RAND_add(&status, sizeof(&status), 0.0);
421 * Closing p[0] on timeout causes the entropy command to
422 * SIGPIPE. Take whatever output we got, and mark this
425 debug2("Command '%s' timed out", src->cmdstring);
426 src->sticky_badness *= 2;
427 src->badness = src->sticky_badness;
428 return total_bytes_read;
431 if (WIFEXITED(status)) {
432 if (WEXITSTATUS(status) == 0) {
433 return total_bytes_read;
435 debug2("Command '%s' exit status was %d",
436 src->cmdstring, WEXITSTATUS(status));
437 src->badness = src->sticky_badness = 128;
440 } else if (WIFSIGNALED(status)) {
441 debug2("Command '%s' returned on uncaught signal %d !",
442 src->cmdstring, status);
443 src->badness = src->sticky_badness = 128;
450 stir_from_system(void)
452 double total_entropy_estimate;
455 total_entropy_estimate = 0;
458 RAND_add(&i, sizeof(i), 0.5);
459 total_entropy_estimate += 0.1;
462 RAND_add(&i, sizeof(i), 0.5);
463 total_entropy_estimate += 0.1;
466 RAND_add(&i, sizeof(i), 0.0);
468 RAND_add(&i, sizeof(i), 0.0);
470 total_entropy_estimate += stir_gettimeofday(1.0);
471 total_entropy_estimate += stir_clock(0.5);
472 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
474 return total_entropy_estimate;
478 stir_from_programs(void)
481 double entropy, total_entropy;
482 unsigned char hash[SHA_DIGEST_LENGTH];
485 for(c = 0; entropy_cmds[c].path != NULL; c++) {
486 if (!entropy_cmds[c].badness) {
487 /* Hash output from command */
488 entropy = hash_command_output(&entropy_cmds[c],
491 /* Scale back estimate by command's rate */
492 entropy *= entropy_cmds[c].rate;
494 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
495 if (entropy > SHA_DIGEST_LENGTH)
496 entropy = SHA_DIGEST_LENGTH;
499 RAND_add(hash, sizeof(hash), entropy);
501 debug3("Got %0.2f bytes of entropy from '%s'",
502 entropy, entropy_cmds[c].cmdstring);
504 total_entropy += entropy;
506 /* Execution time should be a bit unpredictable */
507 total_entropy += stir_gettimeofday(0.05);
508 total_entropy += stir_clock(0.05);
509 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
510 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
512 debug2("Command '%s' disabled (badness %d)",
513 entropy_cmds[c].cmdstring,
514 entropy_cmds[c].badness);
516 if (entropy_cmds[c].badness > 0)
517 entropy_cmds[c].badness--;
521 return total_entropy;
525 * prng seedfile functions
528 prng_check_seedfile(char *filename)
533 * XXX raceable: eg replace seed between this stat and subsequent
534 * open. Not such a problem because we don't really trust the
536 * XXX: use secure path checking as elsewhere in OpenSSH
538 if (lstat(filename, &st) == -1) {
539 /* Give up on hard errors */
541 debug("WARNING: Couldn't stat random seed file "
542 "\"%.100s\": %s", filename, strerror(errno));
547 if (!S_ISREG(st.st_mode))
548 fatal("PRNG seedfile %.100s is not a regular file",
551 /* mode 0600, owned by root or the current user? */
552 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
553 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
554 "owned by uid %li", filename, (long int)getuid());
562 prng_write_seedfile(void)
565 unsigned char seed[SEED_FILE_SIZE];
566 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
570 pw = getpwuid(getuid());
572 fatal("Couldn't get password entry for current user "
573 "(%li): %s", (long int)getuid(), strerror(errno));
575 /* Try to ensure that the parent directory is there */
576 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
578 mkdir(filename, 0700);
580 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
583 strlcpy(tmpseed, filename, sizeof(tmpseed));
584 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
586 fatal("PRNG seed filename too long");
588 if (RAND_bytes(seed, sizeof(seed)) <= 0)
589 fatal("PRNG seed extraction failed");
591 /* Don't care if the seed doesn't exist */
592 prng_check_seedfile(filename);
594 old_umask = umask(0177);
596 if ((fd = mkstemp(tmpseed)) == -1) {
597 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
598 "(%.100s)", tmpseed, strerror(errno));
600 debug("writing PRNG seed to file %.100s", tmpseed);
601 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
605 fatal("problem writing PRNG seedfile %.100s "
606 "(%.100s)", filename, strerror(save_errno));
609 debug("moving temporary PRNG seed to file %.100s", filename);
610 if (rename(tmpseed, filename) == -1) {
613 fatal("problem renaming PRNG seedfile from %.100s "
614 "to %.100s (%.100s)", tmpseed, filename,
615 strerror(save_errno));
622 prng_read_seedfile(void)
625 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
628 pw = getpwuid(getuid());
630 fatal("Couldn't get password entry for current user "
631 "(%li): %s", (long int)getuid(), strerror(errno));
633 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
636 debug("loading PRNG seed from file %.100s", filename);
638 if (!prng_check_seedfile(filename)) {
639 verbose("Random seed file not found or invalid, ignoring.");
643 /* open the file and read in the seed */
644 fd = open(filename, O_RDONLY);
646 fatal("could not open PRNG seedfile %.100s (%.100s)",
647 filename, strerror(errno));
649 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
650 verbose("invalid or short read from PRNG seedfile "
651 "%.100s - ignoring", filename);
652 memset(seed, '\0', sizeof(seed));
656 /* stir in the seed, with estimated entropy zero */
657 RAND_add(&seed, sizeof(seed), 0.0);
662 * entropy command initialisation functions
665 prng_read_commands(char *cmdfilename)
667 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
669 entropy_cmd_t *entcmd;
671 int cur_cmd, linenum, num_cmds, arg;
673 if ((f = fopen(cmdfilename, "r")) == NULL) {
674 fatal("couldn't read entropy commands file %.100s: %.100s",
675 cmdfilename, strerror(errno));
679 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
680 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
683 cur_cmd = linenum = 0;
684 while (fgets(line, sizeof(line), f)) {
687 /* Skip leading whitespace, blank lines and comments */
688 cp = line + strspn(line, WHITESPACE);
689 if ((*cp == 0) || (*cp == '#'))
690 continue; /* done with this line */
693 * The first non-whitespace char should be a double quote
694 * delimiting the commandline
697 error("bad entropy command, %.100s line %d",
698 cmdfilename, linenum);
703 * First token, command args (incl. argv[0]) in double
706 cp = strtok(cp, "\"");
708 error("missing or bad command string, %.100s "
709 "line %d -- ignored", cmdfilename, linenum);
712 strlcpy(cmd, cp, sizeof(cmd));
714 /* Second token, full command path */
715 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
716 error("missing command path, %.100s "
717 "line %d -- ignored", cmdfilename, linenum);
721 /* Did configure mark this as dead? */
722 if (strncmp("undef", cp, 5) == 0)
725 strlcpy(path, cp, sizeof(path));
727 /* Third token, entropy rate estimate for this command */
728 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
729 error("missing entropy estimate, %.100s "
730 "line %d -- ignored", cmdfilename, linenum);
733 est = strtod(cp, NULL);
736 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
737 error("garbage at end of line %d in %.100s "
738 "-- ignored", linenum, cmdfilename);
742 /* save the command for debug messages */
743 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
745 /* split the command args */
746 cp = strtok(cmd, WHITESPACE);
749 entcmd[cur_cmd].args[arg] = xstrdup(cp);
751 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
753 if (strtok(NULL, WHITESPACE))
754 error("ignored extra commands (max %d), %.100s "
755 "line %d", NUM_ARGS, cmdfilename, linenum);
757 /* Copy the command path and rate estimate */
758 entcmd[cur_cmd].path = xstrdup(path);
759 entcmd[cur_cmd].rate = est;
761 /* Initialise other values */
762 entcmd[cur_cmd].sticky_badness = 1;
767 * If we've filled the array, reallocate it twice the size
768 * Do this now because even if this we're on the last
769 * command we need another slot to mark the last entry
771 if (cur_cmd == num_cmds) {
773 entcmd = xrealloc(entcmd, num_cmds *
774 sizeof(entropy_cmd_t));
778 /* zero the last entry */
779 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
782 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
783 sizeof(entropy_cmd_t));
785 debug("Loaded %d entropy commands from %.100s", cur_cmd,
788 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
794 fprintf(stderr, "Usage: %s [options]\n", __progname);
795 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
796 fprintf(stderr, " Multiple -v increases verbosity.\n");
797 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
798 fprintf(stderr, " -X Force output in binary\n");
799 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
804 main(int argc, char **argv)
807 int ret, ch, debug_level, output_hex, bytes;
811 __progname = ssh_get_progname(argv[0]);
812 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
814 ll = SYSLOG_LEVEL_INFO;
815 debug_level = output_hex = 0;
816 bytes = OUTPUT_SEED_SIZE;
818 /* Don't write binary data to a tty, unless we are forced to */
819 if (isatty(STDOUT_FILENO))
822 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
826 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
835 if ((bytes = atoi(optarg)) <= 0)
836 fatal("Invalid number of output bytes");
842 error("Invalid commandline option");
847 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
849 #ifdef USE_SEED_FILES
850 prng_read_seedfile();
853 buf = xmalloc(bytes);
856 * Seed the RNG from wherever we can
859 /* Take whatever is on the stack, but don't credit it */
860 RAND_add(buf, bytes, 0);
862 debug("Seeded RNG with %i bytes from system calls",
863 (int)stir_from_system());
865 /* try prngd, fall back to commands if prngd fails or not configured */
866 if (seed_from_prngd(buf, bytes) == 0) {
867 RAND_add(buf, bytes, bytes);
869 /* Read in collection commands */
870 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
871 fatal("PRNG initialisation failed -- exiting.");
872 debug("Seeded RNG with %i bytes from programs",
873 (int)stir_from_programs());
876 #ifdef USE_SEED_FILES
877 prng_write_seedfile();
881 * Write the seed to stdout
885 fatal("Not enough entropy in RNG");
887 if (RAND_bytes(buf, bytes) <= 0)
888 fatal("Couldn't extract entropy from PRNG");
891 for(ret = 0; ret < bytes; ret++)
892 printf("%02x", (unsigned char)(buf[ret]));
895 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
897 memset(buf, '\0', bytes);
900 return ret == bytes ? 0 : 1;
904 * We may attempt to re-seed during mkstemp if we are using the one in the
905 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
906 * need our own seed_rng(). We must also check that we have enough entropy.
912 fatal("Not enough entropy in RNG");