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>
49 #include <openssl/rand.h>
50 #include <openssl/sha.h>
51 #include <openssl/crypto.h>
53 /* SunOS 4.4.4 needs this */
54 #ifdef HAVE_FLOATINGPOINT_H
55 # include <floatingpoint.h>
56 #endif /* HAVE_FLOATINGPOINT_H */
61 #include "pathnames.h"
64 /* Number of bytes we write out */
65 #define OUTPUT_SEED_SIZE 48
67 /* Length of on-disk seedfiles */
68 #define SEED_FILE_SIZE 1024
70 /* Maximum number of command-line arguments to read from file */
73 /* Minimum number of usable commands to be considered sufficient */
74 #define MIN_ENTROPY_SOURCES 16
76 /* Path to on-disk seed file (relative to user's home directory */
77 #ifndef SSH_PRNG_SEED_FILE
78 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
81 /* Path to PRNG commands list */
82 #ifndef SSH_PRNG_COMMAND_FILE
83 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
86 extern char *__progname;
88 #define WHITESPACE " \t\n"
91 # define RUSAGE_SELF 0
93 #ifndef RUSAGE_CHILDREN
94 # define RUSAGE_CHILDREN 0
97 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
98 # define USE_SEED_FILES
102 /* Proportion of data that is entropy */
104 /* Counter goes positive if this command times out */
105 unsigned int badness;
106 /* Increases by factor of two each timeout */
107 unsigned int sticky_badness;
108 /* Path to executable */
110 /* argv to pass to executable */
111 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
112 /* full command string (debug) */
116 /* slow command timeouts (all in milliseconds) */
117 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
118 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
120 /* this is initialised from a file, by prng_read_commands() */
121 static entropy_cmd_t *entropy_cmds = NULL;
124 double stir_from_system(void);
125 double stir_from_programs(void);
126 double stir_gettimeofday(double entropy_estimate);
127 double stir_clock(double entropy_estimate);
128 double stir_rusage(int who, double entropy_estimate);
129 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
130 int get_random_bytes_prngd(unsigned char *buf, int len,
131 unsigned short tcp_port, char *socket_path);
134 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
135 * listening either on 'tcp_port', or via Unix domain socket at *
137 * Either a non-zero tcp_port or a non-null socket_path must be
139 * Returns 0 on success, -1 on error
142 get_random_bytes_prngd(unsigned char *buf, int len,
143 unsigned short tcp_port, char *socket_path)
145 int fd, addr_len, rval, errors;
147 struct sockaddr_storage addr;
148 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
149 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
153 if (socket_path == NULL && tcp_port == 0)
154 fatal("You must specify a port or a socket");
155 if (socket_path != NULL &&
156 strlen(socket_path) >= sizeof(addr_un->sun_path))
157 fatal("Random pool path is too long");
158 if (len <= 0 || len > 255)
159 fatal("Too many bytes (%d) to read from PRNGD", len);
161 memset(&addr, '\0', sizeof(addr));
164 addr_in->sin_family = AF_INET;
165 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
166 addr_in->sin_port = htons(tcp_port);
167 addr_len = sizeof(*addr_in);
169 addr_un->sun_family = AF_UNIX;
170 strlcpy(addr_un->sun_path, socket_path,
171 sizeof(addr_un->sun_path));
172 addr_len = offsetof(struct sockaddr_un, sun_path) +
173 strlen(socket_path) + 1;
176 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
181 fd = socket(addr.ss_family, SOCK_STREAM, 0);
183 error("Couldn't create socket: %s", strerror(errno));
187 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
189 error("Couldn't connect to PRNGD port %d: %s",
190 tcp_port, strerror(errno));
192 error("Couldn't connect to PRNGD socket \"%s\": %s",
193 addr_un->sun_path, strerror(errno));
198 /* Send blocking read request to PRNGD */
202 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
203 if (errno == EPIPE && errors < 10) {
208 error("Couldn't write to PRNGD socket: %s",
213 if (atomicio(read, fd, buf, len) != (size_t)len) {
214 if (errno == EPIPE && errors < 10) {
219 error("Couldn't read from PRNGD socket: %s",
226 mysignal(SIGPIPE, old_sigpipe);
233 seed_from_prngd(unsigned char *buf, size_t bytes)
236 debug("trying egd/prngd port %d", PRNGD_PORT);
237 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
241 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
242 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
249 stir_gettimeofday(double entropy_estimate)
253 if (gettimeofday(&tv, NULL) == -1)
254 fatal("Couldn't gettimeofday: %s", strerror(errno));
256 RAND_add(&tv, sizeof(tv), entropy_estimate);
258 return entropy_estimate;
262 stir_clock(double entropy_estimate)
268 RAND_add(&c, sizeof(c), entropy_estimate);
270 return entropy_estimate;
271 #else /* _HAVE_CLOCK */
273 #endif /* _HAVE_CLOCK */
277 stir_rusage(int who, double entropy_estimate)
279 #ifdef HAVE_GETRUSAGE
282 if (getrusage(who, &ru) == -1)
285 RAND_add(&ru, sizeof(ru), entropy_estimate);
287 return entropy_estimate;
288 #else /* _HAVE_GETRUSAGE */
290 #endif /* _HAVE_GETRUSAGE */
294 timeval_diff(struct timeval *t1, struct timeval *t2)
296 int secdiff, usecdiff;
298 secdiff = t2->tv_sec - t1->tv_sec;
299 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
300 return (int)(usecdiff / 1000);
304 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
308 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
309 int status, total_bytes_read;
310 static int devnull = -1;
313 struct timeval tv_start, tv_current;
315 debug3("Reading output from \'%s\'", src->cmdstring);
318 devnull = open("/dev/null", O_RDWR);
320 fatal("Couldn't open /dev/null: %s",
325 fatal("Couldn't open pipe: %s", strerror(errno));
327 (void)gettimeofday(&tv_start, NULL); /* record start time */
329 switch (pid = fork()) {
333 fatal("Couldn't fork: %s", strerror(errno));
336 dup2(devnull, STDIN_FILENO);
337 dup2(p[1], STDOUT_FILENO);
338 dup2(p[1], STDERR_FILENO);
343 execv(src->path, (char**)(src->args));
345 debug("(child) Couldn't exec '%s': %s",
346 src->cmdstring, strerror(errno));
348 default: /* Parent */
352 RAND_add(&pid, sizeof(&pid), 0.0);
356 /* Hash output from child */
359 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
360 while (!error_abort && !cmd_eof) {
365 (void) gettimeofday(&tv_current, 0);
366 msec_elapsed = timeval_diff(&tv_start, &tv_current);
367 if (msec_elapsed >= entropy_timeout_current) {
371 msec_remaining = entropy_timeout_current - msec_elapsed;
374 FD_SET(p[0], &rdset);
375 tv.tv_sec = msec_remaining / 1000;
376 tv.tv_usec = (msec_remaining % 1000) * 1000;
378 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
380 RAND_add(&tv, sizeof(tv), 0.0);
391 bytes_read = read(p[0], buf, sizeof(buf));
392 } while (bytes_read == -1 && errno == EINTR);
393 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
394 if (bytes_read == -1) {
397 } else if (bytes_read) {
398 SHA1_Update(&sha, buf, bytes_read);
399 total_bytes_read += bytes_read;
407 debug("Command '%s': select() failed: %s",
408 src->cmdstring, strerror(errno));
414 SHA1_Final(hash, &sha);
418 debug3("Time elapsed: %d msec", msec_elapsed);
420 if (waitpid(pid, &status, 0) == -1) {
421 error("Couldn't wait for child '%s' completion: %s",
422 src->cmdstring, strerror(errno));
426 RAND_add(&status, sizeof(&status), 0.0);
430 * Closing p[0] on timeout causes the entropy command to
431 * SIGPIPE. Take whatever output we got, and mark this
434 debug2("Command '%s' timed out", src->cmdstring);
435 src->sticky_badness *= 2;
436 src->badness = src->sticky_badness;
437 return total_bytes_read;
440 if (WIFEXITED(status)) {
441 if (WEXITSTATUS(status) == 0) {
442 return total_bytes_read;
444 debug2("Command '%s' exit status was %d",
445 src->cmdstring, WEXITSTATUS(status));
446 src->badness = src->sticky_badness = 128;
449 } else if (WIFSIGNALED(status)) {
450 debug2("Command '%s' returned on uncaught signal %d !",
451 src->cmdstring, status);
452 src->badness = src->sticky_badness = 128;
459 stir_from_system(void)
461 double total_entropy_estimate;
464 total_entropy_estimate = 0;
467 RAND_add(&i, sizeof(i), 0.5);
468 total_entropy_estimate += 0.1;
471 RAND_add(&i, sizeof(i), 0.5);
472 total_entropy_estimate += 0.1;
475 RAND_add(&i, sizeof(i), 0.0);
477 RAND_add(&i, sizeof(i), 0.0);
479 total_entropy_estimate += stir_gettimeofday(1.0);
480 total_entropy_estimate += stir_clock(0.5);
481 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
483 return total_entropy_estimate;
487 stir_from_programs(void)
490 double entropy, total_entropy;
491 unsigned char hash[SHA_DIGEST_LENGTH];
494 for(c = 0; entropy_cmds[c].path != NULL; c++) {
495 if (!entropy_cmds[c].badness) {
496 /* Hash output from command */
497 entropy = hash_command_output(&entropy_cmds[c],
500 /* Scale back estimate by command's rate */
501 entropy *= entropy_cmds[c].rate;
503 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
504 if (entropy > SHA_DIGEST_LENGTH)
505 entropy = SHA_DIGEST_LENGTH;
508 RAND_add(hash, sizeof(hash), entropy);
510 debug3("Got %0.2f bytes of entropy from '%s'",
511 entropy, entropy_cmds[c].cmdstring);
513 total_entropy += entropy;
515 /* Execution time should be a bit unpredictable */
516 total_entropy += stir_gettimeofday(0.05);
517 total_entropy += stir_clock(0.05);
518 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
519 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
521 debug2("Command '%s' disabled (badness %d)",
522 entropy_cmds[c].cmdstring,
523 entropy_cmds[c].badness);
525 if (entropy_cmds[c].badness > 0)
526 entropy_cmds[c].badness--;
530 return total_entropy;
534 * prng seedfile functions
537 prng_check_seedfile(char *filename)
542 * XXX raceable: eg replace seed between this stat and subsequent
543 * open. Not such a problem because we don't really trust the
545 * XXX: use secure path checking as elsewhere in OpenSSH
547 if (lstat(filename, &st) == -1) {
548 /* Give up on hard errors */
550 debug("WARNING: Couldn't stat random seed file "
551 "\"%.100s\": %s", filename, strerror(errno));
556 if (!S_ISREG(st.st_mode))
557 fatal("PRNG seedfile %.100s is not a regular file",
560 /* mode 0600, owned by root or the current user? */
561 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
562 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
563 "owned by uid %li", filename, (long int)getuid());
571 prng_write_seedfile(void)
574 unsigned char seed[SEED_FILE_SIZE];
575 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
579 pw = getpwuid(getuid());
581 fatal("Couldn't get password entry for current user "
582 "(%li): %s", (long int)getuid(), strerror(errno));
584 /* Try to ensure that the parent directory is there */
585 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
587 if (mkdir(filename, 0700) < 0 && errno != EEXIST)
588 fatal("mkdir %.200s: %s", filename, strerror(errno));
590 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
593 strlcpy(tmpseed, filename, sizeof(tmpseed));
594 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
596 fatal("PRNG seed filename too long");
598 if (RAND_bytes(seed, sizeof(seed)) <= 0)
599 fatal("PRNG seed extraction failed");
601 /* Don't care if the seed doesn't exist */
602 prng_check_seedfile(filename);
604 old_umask = umask(0177);
606 if ((fd = mkstemp(tmpseed)) == -1) {
607 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
608 "(%.100s)", tmpseed, strerror(errno));
610 debug("writing PRNG seed to file %.100s", tmpseed);
611 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
615 fatal("problem writing PRNG seedfile %.100s "
616 "(%.100s)", filename, strerror(save_errno));
619 debug("moving temporary PRNG seed to file %.100s", filename);
620 if (rename(tmpseed, filename) == -1) {
623 fatal("problem renaming PRNG seedfile from %.100s "
624 "to %.100s (%.100s)", tmpseed, filename,
625 strerror(save_errno));
632 prng_read_seedfile(void)
635 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
638 pw = getpwuid(getuid());
640 fatal("Couldn't get password entry for current user "
641 "(%li): %s", (long int)getuid(), strerror(errno));
643 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
646 debug("loading PRNG seed from file %.100s", filename);
648 if (!prng_check_seedfile(filename)) {
649 verbose("Random seed file not found or invalid, ignoring.");
653 /* open the file and read in the seed */
654 fd = open(filename, O_RDONLY);
656 fatal("could not open PRNG seedfile %.100s (%.100s)",
657 filename, strerror(errno));
659 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
660 verbose("invalid or short read from PRNG seedfile "
661 "%.100s - ignoring", filename);
662 memset(seed, '\0', sizeof(seed));
666 /* stir in the seed, with estimated entropy zero */
667 RAND_add(&seed, sizeof(seed), 0.0);
672 * entropy command initialisation functions
675 prng_read_commands(char *cmdfilename)
677 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
679 entropy_cmd_t *entcmd;
681 int cur_cmd, linenum, num_cmds, arg;
683 if ((f = fopen(cmdfilename, "r")) == NULL) {
684 fatal("couldn't read entropy commands file %.100s: %.100s",
685 cmdfilename, strerror(errno));
689 entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
692 cur_cmd = linenum = 0;
693 while (fgets(line, sizeof(line), f)) {
696 /* Skip leading whitespace, blank lines and comments */
697 cp = line + strspn(line, WHITESPACE);
698 if ((*cp == 0) || (*cp == '#'))
699 continue; /* done with this line */
702 * The first non-whitespace char should be a double quote
703 * delimiting the commandline
706 error("bad entropy command, %.100s line %d",
707 cmdfilename, linenum);
712 * First token, command args (incl. argv[0]) in double
715 cp = strtok(cp, "\"");
717 error("missing or bad command string, %.100s "
718 "line %d -- ignored", cmdfilename, linenum);
721 strlcpy(cmd, cp, sizeof(cmd));
723 /* Second token, full command path */
724 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
725 error("missing command path, %.100s "
726 "line %d -- ignored", cmdfilename, linenum);
730 /* Did configure mark this as dead? */
731 if (strncmp("undef", cp, 5) == 0)
734 strlcpy(path, cp, sizeof(path));
736 /* Third token, entropy rate estimate for this command */
737 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
738 error("missing entropy estimate, %.100s "
739 "line %d -- ignored", cmdfilename, linenum);
742 est = strtod(cp, NULL);
745 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
746 error("garbage at end of line %d in %.100s "
747 "-- ignored", linenum, cmdfilename);
751 /* save the command for debug messages */
752 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
754 /* split the command args */
755 cp = strtok(cmd, WHITESPACE);
758 entcmd[cur_cmd].args[arg] = xstrdup(cp);
760 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
762 if (strtok(NULL, WHITESPACE))
763 error("ignored extra commands (max %d), %.100s "
764 "line %d", NUM_ARGS, cmdfilename, linenum);
766 /* Copy the command path and rate estimate */
767 entcmd[cur_cmd].path = xstrdup(path);
768 entcmd[cur_cmd].rate = est;
770 /* Initialise other values */
771 entcmd[cur_cmd].sticky_badness = 1;
776 * If we've filled the array, reallocate it twice the size
777 * Do this now because even if this we're on the last
778 * command we need another slot to mark the last entry
780 if (cur_cmd == num_cmds) {
782 entcmd = xrealloc(entcmd, num_cmds,
783 sizeof(entropy_cmd_t));
787 /* zero the last entry */
788 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
791 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
792 sizeof(entropy_cmd_t));
794 debug("Loaded %d entropy commands from %.100s", cur_cmd,
798 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
804 fprintf(stderr, "Usage: %s [options]\n", __progname);
805 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
806 fprintf(stderr, " Multiple -v increases verbosity.\n");
807 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
808 fprintf(stderr, " -X Force output in binary\n");
809 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
814 main(int argc, char **argv)
817 int ret, ch, debug_level, output_hex, bytes;
821 __progname = ssh_get_progname(argv[0]);
822 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
824 ll = SYSLOG_LEVEL_INFO;
825 debug_level = output_hex = 0;
826 bytes = OUTPUT_SEED_SIZE;
828 /* Don't write binary data to a tty, unless we are forced to */
829 if (isatty(STDOUT_FILENO))
832 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
836 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
845 if ((bytes = atoi(optarg)) <= 0)
846 fatal("Invalid number of output bytes");
852 error("Invalid commandline option");
857 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
859 #ifdef USE_SEED_FILES
860 prng_read_seedfile();
863 buf = xmalloc(bytes);
866 * Seed the RNG from wherever we can
869 /* Take whatever is on the stack, but don't credit it */
870 RAND_add(buf, bytes, 0);
872 debug("Seeded RNG with %i bytes from system calls",
873 (int)stir_from_system());
875 /* try prngd, fall back to commands if prngd fails or not configured */
876 if (seed_from_prngd(buf, bytes) == 0) {
877 RAND_add(buf, bytes, bytes);
879 /* Read in collection commands */
880 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
881 fatal("PRNG initialisation failed -- exiting.");
882 debug("Seeded RNG with %i bytes from programs",
883 (int)stir_from_programs());
886 #ifdef USE_SEED_FILES
887 prng_write_seedfile();
891 * Write the seed to stdout
895 fatal("Not enough entropy in RNG");
897 if (RAND_bytes(buf, bytes) <= 0)
898 fatal("Couldn't extract entropy from PRNG");
901 for(ret = 0; ret < bytes; ret++)
902 printf("%02x", (unsigned char)(buf[ret]));
905 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
907 memset(buf, '\0', bytes);
910 return ret == bytes ? 0 : 1;
914 * We may attempt to re-seed during mkstemp if we are using the one in the
915 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
916 * need our own seed_rng(). We must also check that we have enough entropy.
922 fatal("Not enough entropy in RNG");