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 seed_from_prngd(unsigned char *buf, size_t bytes)
216 debug("trying egd/prngd port %d", PRNGD_PORT);
217 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
221 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
222 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
229 stir_gettimeofday(double entropy_estimate)
233 if (gettimeofday(&tv, NULL) == -1)
234 fatal("Couldn't gettimeofday: %s", strerror(errno));
236 RAND_add(&tv, sizeof(tv), entropy_estimate);
238 return entropy_estimate;
242 stir_clock(double entropy_estimate)
248 RAND_add(&c, sizeof(c), entropy_estimate);
250 return entropy_estimate;
251 #else /* _HAVE_CLOCK */
253 #endif /* _HAVE_CLOCK */
257 stir_rusage(int who, double entropy_estimate)
259 #ifdef HAVE_GETRUSAGE
262 if (getrusage(who, &ru) == -1)
265 RAND_add(&ru, sizeof(ru), entropy_estimate);
267 return entropy_estimate;
268 #else /* _HAVE_GETRUSAGE */
270 #endif /* _HAVE_GETRUSAGE */
274 timeval_diff(struct timeval *t1, struct timeval *t2)
276 int secdiff, usecdiff;
278 secdiff = t2->tv_sec - t1->tv_sec;
279 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
280 return (int)(usecdiff / 1000);
284 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
288 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
289 int status, total_bytes_read;
290 static int devnull = -1;
293 struct timeval tv_start, tv_current;
295 debug3("Reading output from \'%s\'", src->cmdstring);
298 devnull = open("/dev/null", O_RDWR);
300 fatal("Couldn't open /dev/null: %s",
305 fatal("Couldn't open pipe: %s", strerror(errno));
307 (void)gettimeofday(&tv_start, NULL); /* record start time */
309 switch (pid = fork()) {
313 fatal("Couldn't fork: %s", strerror(errno));
316 dup2(devnull, STDIN_FILENO);
317 dup2(p[1], STDOUT_FILENO);
318 dup2(p[1], STDERR_FILENO);
323 execv(src->path, (char**)(src->args));
325 debug("(child) Couldn't exec '%s': %s",
326 src->cmdstring, strerror(errno));
328 default: /* Parent */
332 RAND_add(&pid, sizeof(&pid), 0.0);
336 /* Hash output from child */
339 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
340 while (!error_abort && !cmd_eof) {
345 (void) gettimeofday(&tv_current, 0);
346 msec_elapsed = timeval_diff(&tv_start, &tv_current);
347 if (msec_elapsed >= entropy_timeout_current) {
351 msec_remaining = entropy_timeout_current - msec_elapsed;
354 FD_SET(p[0], &rdset);
355 tv.tv_sec = msec_remaining / 1000;
356 tv.tv_usec = (msec_remaining % 1000) * 1000;
358 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
360 RAND_add(&tv, sizeof(tv), 0.0);
371 bytes_read = read(p[0], buf, sizeof(buf));
372 } while (bytes_read == -1 && errno == EINTR);
373 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
374 if (bytes_read == -1) {
377 } else if (bytes_read) {
378 SHA1_Update(&sha, buf, bytes_read);
379 total_bytes_read += bytes_read;
387 debug("Command '%s': select() failed: %s",
388 src->cmdstring, strerror(errno));
394 SHA1_Final(hash, &sha);
398 debug3("Time elapsed: %d msec", msec_elapsed);
400 if (waitpid(pid, &status, 0) == -1) {
401 error("Couldn't wait for child '%s' completion: %s",
402 src->cmdstring, strerror(errno));
406 RAND_add(&status, sizeof(&status), 0.0);
410 * Closing p[0] on timeout causes the entropy command to
411 * SIGPIPE. Take whatever output we got, and mark this
414 debug2("Command '%s' timed out", src->cmdstring);
415 src->sticky_badness *= 2;
416 src->badness = src->sticky_badness;
417 return total_bytes_read;
420 if (WIFEXITED(status)) {
421 if (WEXITSTATUS(status) == 0) {
422 return total_bytes_read;
424 debug2("Command '%s' exit status was %d",
425 src->cmdstring, WEXITSTATUS(status));
426 src->badness = src->sticky_badness = 128;
429 } else if (WIFSIGNALED(status)) {
430 debug2("Command '%s' returned on uncaught signal %d !",
431 src->cmdstring, status);
432 src->badness = src->sticky_badness = 128;
439 stir_from_system(void)
441 double total_entropy_estimate;
444 total_entropy_estimate = 0;
447 RAND_add(&i, sizeof(i), 0.5);
448 total_entropy_estimate += 0.1;
451 RAND_add(&i, sizeof(i), 0.5);
452 total_entropy_estimate += 0.1;
455 RAND_add(&i, sizeof(i), 0.0);
457 RAND_add(&i, sizeof(i), 0.0);
459 total_entropy_estimate += stir_gettimeofday(1.0);
460 total_entropy_estimate += stir_clock(0.5);
461 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
463 return total_entropy_estimate;
467 stir_from_programs(void)
470 double entropy, total_entropy;
471 unsigned char hash[SHA_DIGEST_LENGTH];
474 for(c = 0; entropy_cmds[c].path != NULL; c++) {
475 if (!entropy_cmds[c].badness) {
476 /* Hash output from command */
477 entropy = hash_command_output(&entropy_cmds[c],
480 /* Scale back estimate by command's rate */
481 entropy *= entropy_cmds[c].rate;
483 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
484 if (entropy > SHA_DIGEST_LENGTH)
485 entropy = SHA_DIGEST_LENGTH;
488 RAND_add(hash, sizeof(hash), entropy);
490 debug3("Got %0.2f bytes of entropy from '%s'",
491 entropy, entropy_cmds[c].cmdstring);
493 total_entropy += entropy;
495 /* Execution time should be a bit unpredictable */
496 total_entropy += stir_gettimeofday(0.05);
497 total_entropy += stir_clock(0.05);
498 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
499 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
501 debug2("Command '%s' disabled (badness %d)",
502 entropy_cmds[c].cmdstring,
503 entropy_cmds[c].badness);
505 if (entropy_cmds[c].badness > 0)
506 entropy_cmds[c].badness--;
510 return total_entropy;
514 * prng seedfile functions
517 prng_check_seedfile(char *filename)
522 * XXX raceable: eg replace seed between this stat and subsequent
523 * open. Not such a problem because we don't really trust the
525 * XXX: use secure path checking as elsewhere in OpenSSH
527 if (lstat(filename, &st) == -1) {
528 /* Give up on hard errors */
530 debug("WARNING: Couldn't stat random seed file "
531 "\"%.100s\": %s", filename, strerror(errno));
536 if (!S_ISREG(st.st_mode))
537 fatal("PRNG seedfile %.100s is not a regular file",
540 /* mode 0600, owned by root or the current user? */
541 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
542 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
543 "owned by uid %li", filename, (long int)getuid());
551 prng_write_seedfile(void)
554 unsigned char seed[SEED_FILE_SIZE];
555 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
559 pw = getpwuid(getuid());
561 fatal("Couldn't get password entry for current user "
562 "(%li): %s", (long int)getuid(), strerror(errno));
564 /* Try to ensure that the parent directory is there */
565 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
567 mkdir(filename, 0700);
569 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
572 strlcpy(tmpseed, filename, sizeof(tmpseed));
573 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
575 fatal("PRNG seed filename too long");
577 if (RAND_bytes(seed, sizeof(seed)) <= 0)
578 fatal("PRNG seed extraction failed");
580 /* Don't care if the seed doesn't exist */
581 prng_check_seedfile(filename);
583 old_umask = umask(0177);
585 if ((fd = mkstemp(tmpseed)) == -1) {
586 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
587 "(%.100s)", tmpseed, strerror(errno));
589 debug("writing PRNG seed to file %.100s", tmpseed);
590 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
594 fatal("problem writing PRNG seedfile %.100s "
595 "(%.100s)", filename, strerror(save_errno));
598 debug("moving temporary PRNG seed to file %.100s", filename);
599 if (rename(tmpseed, filename) == -1) {
602 fatal("problem renaming PRNG seedfile from %.100s "
603 "to %.100s (%.100s)", tmpseed, filename,
604 strerror(save_errno));
611 prng_read_seedfile(void)
614 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
617 pw = getpwuid(getuid());
619 fatal("Couldn't get password entry for current user "
620 "(%li): %s", (long int)getuid(), strerror(errno));
622 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
625 debug("loading PRNG seed from file %.100s", filename);
627 if (!prng_check_seedfile(filename)) {
628 verbose("Random seed file not found or invalid, ignoring.");
632 /* open the file and read in the seed */
633 fd = open(filename, O_RDONLY);
635 fatal("could not open PRNG seedfile %.100s (%.100s)",
636 filename, strerror(errno));
638 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
639 verbose("invalid or short read from PRNG seedfile "
640 "%.100s - ignoring", filename);
641 memset(seed, '\0', sizeof(seed));
645 /* stir in the seed, with estimated entropy zero */
646 RAND_add(&seed, sizeof(seed), 0.0);
651 * entropy command initialisation functions
654 prng_read_commands(char *cmdfilename)
656 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
658 entropy_cmd_t *entcmd;
660 int cur_cmd, linenum, num_cmds, arg;
662 if ((f = fopen(cmdfilename, "r")) == NULL) {
663 fatal("couldn't read entropy commands file %.100s: %.100s",
664 cmdfilename, strerror(errno));
668 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
669 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
672 cur_cmd = linenum = 0;
673 while (fgets(line, sizeof(line), f)) {
676 /* Skip leading whitespace, blank lines and comments */
677 cp = line + strspn(line, WHITESPACE);
678 if ((*cp == 0) || (*cp == '#'))
679 continue; /* done with this line */
682 * The first non-whitespace char should be a double quote
683 * delimiting the commandline
686 error("bad entropy command, %.100s line %d",
687 cmdfilename, linenum);
692 * First token, command args (incl. argv[0]) in double
695 cp = strtok(cp, "\"");
697 error("missing or bad command string, %.100s "
698 "line %d -- ignored", cmdfilename, linenum);
701 strlcpy(cmd, cp, sizeof(cmd));
703 /* Second token, full command path */
704 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
705 error("missing command path, %.100s "
706 "line %d -- ignored", cmdfilename, linenum);
710 /* Did configure mark this as dead? */
711 if (strncmp("undef", cp, 5) == 0)
714 strlcpy(path, cp, sizeof(path));
716 /* Third token, entropy rate estimate for this command */
717 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
718 error("missing entropy estimate, %.100s "
719 "line %d -- ignored", cmdfilename, linenum);
722 est = strtod(cp, NULL);
725 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
726 error("garbage at end of line %d in %.100s "
727 "-- ignored", linenum, cmdfilename);
731 /* save the command for debug messages */
732 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
734 /* split the command args */
735 cp = strtok(cmd, WHITESPACE);
738 entcmd[cur_cmd].args[arg] = xstrdup(cp);
740 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
742 if (strtok(NULL, WHITESPACE))
743 error("ignored extra commands (max %d), %.100s "
744 "line %d", NUM_ARGS, cmdfilename, linenum);
746 /* Copy the command path and rate estimate */
747 entcmd[cur_cmd].path = xstrdup(path);
748 entcmd[cur_cmd].rate = est;
750 /* Initialise other values */
751 entcmd[cur_cmd].sticky_badness = 1;
756 * If we've filled the array, reallocate it twice the size
757 * Do this now because even if this we're on the last
758 * command we need another slot to mark the last entry
760 if (cur_cmd == num_cmds) {
762 entcmd = xrealloc(entcmd, num_cmds *
763 sizeof(entropy_cmd_t));
767 /* zero the last entry */
768 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
771 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
772 sizeof(entropy_cmd_t));
774 debug("Loaded %d entropy commands from %.100s", cur_cmd,
777 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
783 fprintf(stderr, "Usage: %s [options]\n", __progname);
784 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
785 fprintf(stderr, " Multiple -v increases verbosity.\n");
786 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
787 fprintf(stderr, " -X Force output in binary\n");
788 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
793 main(int argc, char **argv)
796 int ret, ch, debug_level, output_hex, bytes;
800 __progname = ssh_get_progname(argv[0]);
801 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
803 ll = SYSLOG_LEVEL_INFO;
804 debug_level = output_hex = 0;
805 bytes = OUTPUT_SEED_SIZE;
807 /* Don't write binary data to a tty, unless we are forced to */
808 if (isatty(STDOUT_FILENO))
811 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
815 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
824 if ((bytes = atoi(optarg)) <= 0)
825 fatal("Invalid number of output bytes");
831 error("Invalid commandline option");
836 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
838 #ifdef USE_SEED_FILES
839 prng_read_seedfile();
842 buf = xmalloc(bytes);
845 * Seed the RNG from wherever we can
848 /* Take whatever is on the stack, but don't credit it */
849 RAND_add(buf, bytes, 0);
851 debug("Seeded RNG with %i bytes from system calls",
852 (int)stir_from_system());
854 /* try prngd, fall back to commands if prngd fails or not configured */
855 if (seed_from_prngd(buf, bytes) == 0) {
856 RAND_add(buf, bytes, bytes);
858 /* Read in collection commands */
859 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
860 fatal("PRNG initialisation failed -- exiting.");
861 debug("Seeded RNG with %i bytes from programs",
862 (int)stir_from_programs());
865 #ifdef USE_SEED_FILES
866 prng_write_seedfile();
870 * Write the seed to stdout
874 fatal("Not enough entropy in RNG");
876 if (RAND_bytes(buf, bytes) <= 0)
877 fatal("Couldn't extract entropy from PRNG");
880 for(ret = 0; ret < bytes; ret++)
881 printf("%02x", (unsigned char)(buf[ret]));
884 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
886 memset(buf, '\0', bytes);
889 return ret == bytes ? 0 : 1;
893 * We may attempt to re-seed during mkstemp if we are using the one in the
894 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
895 * need our own seed_rng(). We must also check that we have enough entropy.
901 fatal("Not enough entropy in RNG");