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 #ifdef HAVE___PROGNAME
67 extern char *__progname;
73 # define offsetof(type, member) ((size_t) &((type *)0)->member)
76 #define WHITESPACE " \t\n"
79 # define RUSAGE_SELF 0
81 #ifndef RUSAGE_CHILDREN
82 # define RUSAGE_CHILDREN 0
85 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
86 # define USE_SEED_FILES
90 /* Proportion of data that is entropy */
92 /* Counter goes positive if this command times out */
94 /* Increases by factor of two each timeout */
95 unsigned int sticky_badness;
96 /* Path to executable */
98 /* argv to pass to executable */
99 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
100 /* full command string (debug) */
104 /* slow command timeouts (all in milliseconds) */
105 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
106 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
108 /* this is initialised from a file, by prng_read_commands() */
109 static entropy_cmd_t *entropy_cmds = NULL;
112 double stir_from_system(void);
113 double stir_from_programs(void);
114 double stir_gettimeofday(double entropy_estimate);
115 double stir_clock(double entropy_estimate);
116 double stir_rusage(int who, double entropy_estimate);
117 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
118 int get_random_bytes_prngd(unsigned char *buf, int len,
119 unsigned short tcp_port, char *socket_path);
122 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
123 * listening either on 'tcp_port', or via Unix domain socket at *
125 * Either a non-zero tcp_port or a non-null socket_path must be
127 * Returns 0 on success, -1 on error
130 get_random_bytes_prngd(unsigned char *buf, int len,
131 unsigned short tcp_port, char *socket_path)
133 int fd, addr_len, rval, errors;
135 struct sockaddr_storage addr;
136 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
137 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
141 if (socket_path == NULL && tcp_port == 0)
142 fatal("You must specify a port or a socket");
143 if (socket_path != NULL &&
144 strlen(socket_path) >= sizeof(addr_un->sun_path))
145 fatal("Random pool path is too long");
147 fatal("Too many bytes to read from PRNGD");
149 memset(&addr, '\0', sizeof(addr));
152 addr_in->sin_family = AF_INET;
153 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
154 addr_in->sin_port = htons(tcp_port);
155 addr_len = sizeof(*addr_in);
157 addr_un->sun_family = AF_UNIX;
158 strlcpy(addr_un->sun_path, socket_path,
159 sizeof(addr_un->sun_path));
160 addr_len = offsetof(struct sockaddr_un, sun_path) +
161 strlen(socket_path) + 1;
164 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
169 fd = socket(addr.ss_family, SOCK_STREAM, 0);
171 error("Couldn't create socket: %s", strerror(errno));
175 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
177 error("Couldn't connect to PRNGD port %d: %s",
178 tcp_port, strerror(errno));
180 error("Couldn't connect to PRNGD socket \"%s\": %s",
181 addr_un->sun_path, strerror(errno));
186 /* Send blocking read request to PRNGD */
190 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
191 if (errno == EPIPE && errors < 10) {
196 error("Couldn't write to PRNGD socket: %s",
201 if (atomicio(read, fd, buf, len) != len) {
202 if (errno == EPIPE && errors < 10) {
207 error("Couldn't read from PRNGD socket: %s",
214 mysignal(SIGPIPE, old_sigpipe);
221 stir_gettimeofday(double entropy_estimate)
225 if (gettimeofday(&tv, NULL) == -1)
226 fatal("Couldn't gettimeofday: %s", strerror(errno));
228 RAND_add(&tv, sizeof(tv), entropy_estimate);
230 return entropy_estimate;
234 stir_clock(double entropy_estimate)
240 RAND_add(&c, sizeof(c), entropy_estimate);
242 return entropy_estimate;
243 #else /* _HAVE_CLOCK */
245 #endif /* _HAVE_CLOCK */
249 stir_rusage(int who, double entropy_estimate)
251 #ifdef HAVE_GETRUSAGE
254 if (getrusage(who, &ru) == -1)
257 RAND_add(&ru, sizeof(ru), entropy_estimate);
259 return entropy_estimate;
260 #else /* _HAVE_GETRUSAGE */
262 #endif /* _HAVE_GETRUSAGE */
266 timeval_diff(struct timeval *t1, struct timeval *t2)
268 int secdiff, usecdiff;
270 secdiff = t2->tv_sec - t1->tv_sec;
271 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
272 return (int)(usecdiff / 1000);
276 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
280 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
281 int status, total_bytes_read;
282 static int devnull = -1;
285 struct timeval tv_start, tv_current;
287 debug3("Reading output from \'%s\'", src->cmdstring);
290 devnull = open("/dev/null", O_RDWR);
292 fatal("Couldn't open /dev/null: %s",
297 fatal("Couldn't open pipe: %s", strerror(errno));
299 (void)gettimeofday(&tv_start, NULL); /* record start time */
301 switch (pid = fork()) {
305 fatal("Couldn't fork: %s", strerror(errno));
308 dup2(devnull, STDIN_FILENO);
309 dup2(p[1], STDOUT_FILENO);
310 dup2(p[1], STDERR_FILENO);
315 execv(src->path, (char**)(src->args));
317 debug("(child) Couldn't exec '%s': %s",
318 src->cmdstring, strerror(errno));
320 default: /* Parent */
324 RAND_add(&pid, sizeof(&pid), 0.0);
328 /* Hash output from child */
331 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
332 while (!error_abort && !cmd_eof) {
337 (void) gettimeofday(&tv_current, 0);
338 msec_elapsed = timeval_diff(&tv_start, &tv_current);
339 if (msec_elapsed >= entropy_timeout_current) {
343 msec_remaining = entropy_timeout_current - msec_elapsed;
346 FD_SET(p[0], &rdset);
347 tv.tv_sec = msec_remaining / 1000;
348 tv.tv_usec = (msec_remaining % 1000) * 1000;
350 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
352 RAND_add(&tv, sizeof(tv), 0.0);
363 bytes_read = read(p[0], buf, sizeof(buf));
364 } while (bytes_read == -1 && errno == EINTR);
365 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
366 if (bytes_read == -1) {
369 } else if (bytes_read) {
370 SHA1_Update(&sha, buf, bytes_read);
371 total_bytes_read += bytes_read;
379 debug("Command '%s': select() failed: %s",
380 src->cmdstring, strerror(errno));
386 SHA1_Final(hash, &sha);
390 debug3("Time elapsed: %d msec", msec_elapsed);
392 if (waitpid(pid, &status, 0) == -1) {
393 error("Couldn't wait for child '%s' completion: %s",
394 src->cmdstring, strerror(errno));
398 RAND_add(&status, sizeof(&status), 0.0);
402 * Closing p[0] on timeout causes the entropy command to
403 * SIGPIPE. Take whatever output we got, and mark this
406 debug2("Command '%s' timed out", src->cmdstring);
407 src->sticky_badness *= 2;
408 src->badness = src->sticky_badness;
409 return total_bytes_read;
412 if (WIFEXITED(status)) {
413 if (WEXITSTATUS(status) == 0) {
414 return total_bytes_read;
416 debug2("Command '%s' exit status was %d",
417 src->cmdstring, WEXITSTATUS(status));
418 src->badness = src->sticky_badness = 128;
421 } else if (WIFSIGNALED(status)) {
422 debug2("Command '%s' returned on uncaught signal %d !",
423 src->cmdstring, status);
424 src->badness = src->sticky_badness = 128;
431 stir_from_system(void)
433 double total_entropy_estimate;
436 total_entropy_estimate = 0;
439 RAND_add(&i, sizeof(i), 0.5);
440 total_entropy_estimate += 0.1;
443 RAND_add(&i, sizeof(i), 0.5);
444 total_entropy_estimate += 0.1;
447 RAND_add(&i, sizeof(i), 0.0);
449 RAND_add(&i, sizeof(i), 0.0);
451 total_entropy_estimate += stir_gettimeofday(1.0);
452 total_entropy_estimate += stir_clock(0.5);
453 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
455 return total_entropy_estimate;
459 stir_from_programs(void)
462 double entropy, total_entropy;
463 unsigned char hash[SHA_DIGEST_LENGTH];
466 for(c = 0; entropy_cmds[c].path != NULL; c++) {
467 if (!entropy_cmds[c].badness) {
468 /* Hash output from command */
469 entropy = hash_command_output(&entropy_cmds[c],
472 /* Scale back estimate by command's rate */
473 entropy *= entropy_cmds[c].rate;
475 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
476 if (entropy > SHA_DIGEST_LENGTH)
477 entropy = SHA_DIGEST_LENGTH;
480 RAND_add(hash, sizeof(hash), entropy);
482 debug3("Got %0.2f bytes of entropy from '%s'",
483 entropy, entropy_cmds[c].cmdstring);
485 total_entropy += entropy;
487 /* Execution time should be a bit unpredictable */
488 total_entropy += stir_gettimeofday(0.05);
489 total_entropy += stir_clock(0.05);
490 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
491 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
493 debug2("Command '%s' disabled (badness %d)",
494 entropy_cmds[c].cmdstring,
495 entropy_cmds[c].badness);
497 if (entropy_cmds[c].badness > 0)
498 entropy_cmds[c].badness--;
502 return total_entropy;
506 * prng seedfile functions
509 prng_check_seedfile(char *filename)
514 * XXX raceable: eg replace seed between this stat and subsequent
515 * open. Not such a problem because we don't really trust the
517 * XXX: use secure path checking as elsewhere in OpenSSH
519 if (lstat(filename, &st) == -1) {
520 /* Give up on hard errors */
522 debug("WARNING: Couldn't stat random seed file "
523 "\"%.100s\": %s", filename, strerror(errno));
528 if (!S_ISREG(st.st_mode))
529 fatal("PRNG seedfile %.100s is not a regular file",
532 /* mode 0600, owned by root or the current user? */
533 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
534 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
535 "owned by uid %li", filename, (long int)getuid());
543 prng_write_seedfile(void)
546 unsigned char seed[SEED_FILE_SIZE];
547 char filename[MAXPATHLEN];
550 pw = getpwuid(getuid());
552 fatal("Couldn't get password entry for current user "
553 "(%li): %s", (long int)getuid(), strerror(errno));
555 /* Try to ensure that the parent directory is there */
556 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
558 mkdir(filename, 0700);
560 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
563 debug("writing PRNG seed to file %.100s", filename);
565 if (RAND_bytes(seed, sizeof(seed)) <= 0)
566 fatal("PRNG seed extraction failed");
568 /* Don't care if the seed doesn't exist */
569 prng_check_seedfile(filename);
571 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
572 debug("WARNING: couldn't access PRNG seedfile %.100s "
573 "(%.100s)", filename, strerror(errno));
575 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed))
576 fatal("problem writing PRNG seedfile %.100s "
577 "(%.100s)", filename, strerror(errno));
583 prng_read_seedfile(void)
586 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
589 pw = getpwuid(getuid());
591 fatal("Couldn't get password entry for current user "
592 "(%li): %s", (long int)getuid(), strerror(errno));
594 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
597 debug("loading PRNG seed from file %.100s", filename);
599 if (!prng_check_seedfile(filename)) {
600 verbose("Random seed file not found or invalid, ignoring.");
604 /* open the file and read in the seed */
605 fd = open(filename, O_RDONLY);
607 fatal("could not open PRNG seedfile %.100s (%.100s)",
608 filename, strerror(errno));
610 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
611 verbose("invalid or short read from PRNG seedfile "
612 "%.100s - ignoring", filename);
613 memset(seed, '\0', sizeof(seed));
617 /* stir in the seed, with estimated entropy zero */
618 RAND_add(&seed, sizeof(seed), 0.0);
623 * entropy command initialisation functions
626 prng_read_commands(char *cmdfilename)
628 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
630 entropy_cmd_t *entcmd;
632 int cur_cmd, linenum, num_cmds, arg;
634 if ((f = fopen(cmdfilename, "r")) == NULL) {
635 fatal("couldn't read entropy commands file %.100s: %.100s",
636 cmdfilename, strerror(errno));
640 entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
641 memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
644 cur_cmd = linenum = 0;
645 while (fgets(line, sizeof(line), f)) {
648 /* Skip leading whitespace, blank lines and comments */
649 cp = line + strspn(line, WHITESPACE);
650 if ((*cp == 0) || (*cp == '#'))
651 continue; /* done with this line */
654 * The first non-whitespace char should be a double quote
655 * delimiting the commandline
658 error("bad entropy command, %.100s line %d",
659 cmdfilename, linenum);
664 * First token, command args (incl. argv[0]) in double
667 cp = strtok(cp, "\"");
669 error("missing or bad command string, %.100s "
670 "line %d -- ignored", cmdfilename, linenum);
673 strlcpy(cmd, cp, sizeof(cmd));
675 /* Second token, full command path */
676 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
677 error("missing command path, %.100s "
678 "line %d -- ignored", cmdfilename, linenum);
682 /* Did configure mark this as dead? */
683 if (strncmp("undef", cp, 5) == 0)
686 strlcpy(path, cp, sizeof(path));
688 /* Third token, entropy rate estimate for this command */
689 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
690 error("missing entropy estimate, %.100s "
691 "line %d -- ignored", cmdfilename, linenum);
694 est = strtod(cp, NULL);
697 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
698 error("garbage at end of line %d in %.100s "
699 "-- ignored", linenum, cmdfilename);
703 /* save the command for debug messages */
704 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
706 /* split the command args */
707 cp = strtok(cmd, WHITESPACE);
710 entcmd[cur_cmd].args[arg] = xstrdup(cp);
712 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
714 if (strtok(NULL, WHITESPACE))
715 error("ignored extra commands (max %d), %.100s "
716 "line %d", NUM_ARGS, cmdfilename, linenum);
718 /* Copy the command path and rate estimate */
719 entcmd[cur_cmd].path = xstrdup(path);
720 entcmd[cur_cmd].rate = est;
722 /* Initialise other values */
723 entcmd[cur_cmd].sticky_badness = 1;
728 * If we've filled the array, reallocate it twice the size
729 * Do this now because even if this we're on the last
730 * command we need another slot to mark the last entry
732 if (cur_cmd == num_cmds) {
734 entcmd = xrealloc(entcmd, num_cmds *
735 sizeof(entropy_cmd_t));
739 /* zero the last entry */
740 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
743 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
744 sizeof(entropy_cmd_t));
746 debug("Loaded %d entropy commands from %.100s", cur_cmd,
749 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
755 fprintf(stderr, "Usage: %s [options]\n", __progname);
756 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
757 fprintf(stderr, " Multiple -v increases verbosity.\n");
758 fprintf(stderr, " -x Force output in hexidecimal (for debugging)\n");
759 fprintf(stderr, " -X Force output in binary\n");
760 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
765 main(int argc, char **argv)
768 int ret, ch, debug_level, output_hex, bytes;
772 __progname = ssh_get_progname(argv[0]);
773 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
775 ll = SYSLOG_LEVEL_INFO;
776 debug_level = output_hex = 0;
777 bytes = OUTPUT_SEED_SIZE;
779 /* Don't write binary data to a tty, unless we are forced to */
780 if (isatty(STDOUT_FILENO))
783 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
787 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
796 if ((bytes = atoi(optarg)) <= 0)
797 fatal("Invalid number of output bytes");
803 error("Invalid commandline option");
808 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
810 #ifdef USE_SEED_FILES
811 prng_read_seedfile();
814 buf = xmalloc(bytes);
817 * Seed the RNG from wherever we can
820 /* Take whatever is on the stack, but don't credit it */
821 RAND_add(buf, bytes, 0);
823 debug("Seeded RNG with %i bytes from system calls",
824 (int)stir_from_system());
827 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == -1)
828 fatal("Entropy collection failed");
829 RAND_add(buf, bytes, bytes);
830 #elif defined(PRNGD_SOCKET)
831 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == -1)
832 fatal("Entropy collection failed");
833 RAND_add(buf, bytes, bytes);
835 /* Read in collection commands */
836 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
837 fatal("PRNG initialisation failed -- exiting.");
838 debug("Seeded RNG with %i bytes from programs",
839 (int)stir_from_programs());
842 #ifdef USE_SEED_FILES
843 prng_write_seedfile();
847 * Write the seed to stdout
851 fatal("Not enough entropy in RNG");
853 if (RAND_bytes(buf, bytes) <= 0)
854 fatal("Couldn't extract entropy from PRNG");
857 for(ret = 0; ret < bytes; ret++)
858 printf("%02x", (unsigned char)(buf[ret]));
861 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
863 memset(buf, '\0', bytes);
866 return ret == bytes ? 0 : 1;