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>
33 #include <netinet/in.h>
42 #include <openssl/rand.h>
43 #include <openssl/sha.h>
44 #include <openssl/crypto.h>
46 /* SunOS 4.4.4 needs this */
47 #ifdef HAVE_FLOATINGPOINT_H
48 # include <floatingpoint.h>
49 #endif /* HAVE_FLOATINGPOINT_H */
54 #include "pathnames.h"
57 /* Number of bytes we write out */
58 #define OUTPUT_SEED_SIZE 48
60 /* Length of on-disk seedfiles */
61 #define SEED_FILE_SIZE 1024
63 /* Maximum number of command-line arguments to read from file */
66 /* Minimum number of usable commands to be considered sufficient */
67 #define MIN_ENTROPY_SOURCES 16
69 /* Path to on-disk seed file (relative to user's home directory */
70 #ifndef SSH_PRNG_SEED_FILE
71 # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed"
74 /* Path to PRNG commands list */
75 #ifndef SSH_PRNG_COMMAND_FILE
76 # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds"
79 extern char *__progname;
81 #define WHITESPACE " \t\n"
84 # define RUSAGE_SELF 0
86 #ifndef RUSAGE_CHILDREN
87 # define RUSAGE_CHILDREN 0
90 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
91 # define USE_SEED_FILES
95 /* Proportion of data that is entropy */
97 /* Counter goes positive if this command times out */
99 /* Increases by factor of two each timeout */
100 unsigned int sticky_badness;
101 /* Path to executable */
103 /* argv to pass to executable */
104 char *args[NUM_ARGS]; /* XXX: arbitrary limit */
105 /* full command string (debug) */
109 /* slow command timeouts (all in milliseconds) */
110 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
111 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
113 /* this is initialised from a file, by prng_read_commands() */
114 static entropy_cmd_t *entropy_cmds = NULL;
117 double stir_from_system(void);
118 double stir_from_programs(void);
119 double stir_gettimeofday(double entropy_estimate);
120 double stir_clock(double entropy_estimate);
121 double stir_rusage(int who, double entropy_estimate);
122 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
123 int get_random_bytes_prngd(unsigned char *buf, int len,
124 unsigned short tcp_port, char *socket_path);
127 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
128 * listening either on 'tcp_port', or via Unix domain socket at *
130 * Either a non-zero tcp_port or a non-null socket_path must be
132 * Returns 0 on success, -1 on error
135 get_random_bytes_prngd(unsigned char *buf, int len,
136 unsigned short tcp_port, char *socket_path)
138 int fd, addr_len, rval, errors;
140 struct sockaddr_storage addr;
141 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
142 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
146 if (socket_path == NULL && tcp_port == 0)
147 fatal("You must specify a port or a socket");
148 if (socket_path != NULL &&
149 strlen(socket_path) >= sizeof(addr_un->sun_path))
150 fatal("Random pool path is too long");
151 if (len <= 0 || len > 255)
152 fatal("Too many bytes (%d) to read from PRNGD", len);
154 memset(&addr, '\0', sizeof(addr));
157 addr_in->sin_family = AF_INET;
158 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
159 addr_in->sin_port = htons(tcp_port);
160 addr_len = sizeof(*addr_in);
162 addr_un->sun_family = AF_UNIX;
163 strlcpy(addr_un->sun_path, socket_path,
164 sizeof(addr_un->sun_path));
165 addr_len = offsetof(struct sockaddr_un, sun_path) +
166 strlen(socket_path) + 1;
169 old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
174 fd = socket(addr.ss_family, SOCK_STREAM, 0);
176 error("Couldn't create socket: %s", strerror(errno));
180 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
182 error("Couldn't connect to PRNGD port %d: %s",
183 tcp_port, strerror(errno));
185 error("Couldn't connect to PRNGD socket \"%s\": %s",
186 addr_un->sun_path, strerror(errno));
191 /* Send blocking read request to PRNGD */
195 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
196 if (errno == EPIPE && errors < 10) {
201 error("Couldn't write to PRNGD socket: %s",
206 if (atomicio(read, fd, buf, len) != (size_t)len) {
207 if (errno == EPIPE && errors < 10) {
212 error("Couldn't read from PRNGD socket: %s",
219 mysignal(SIGPIPE, old_sigpipe);
226 seed_from_prngd(unsigned char *buf, size_t bytes)
229 debug("trying egd/prngd port %d", PRNGD_PORT);
230 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
234 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
235 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
242 stir_gettimeofday(double entropy_estimate)
246 if (gettimeofday(&tv, NULL) == -1)
247 fatal("Couldn't gettimeofday: %s", strerror(errno));
249 RAND_add(&tv, sizeof(tv), entropy_estimate);
251 return entropy_estimate;
255 stir_clock(double entropy_estimate)
261 RAND_add(&c, sizeof(c), entropy_estimate);
263 return entropy_estimate;
264 #else /* _HAVE_CLOCK */
266 #endif /* _HAVE_CLOCK */
270 stir_rusage(int who, double entropy_estimate)
272 #ifdef HAVE_GETRUSAGE
275 if (getrusage(who, &ru) == -1)
278 RAND_add(&ru, sizeof(ru), entropy_estimate);
280 return entropy_estimate;
281 #else /* _HAVE_GETRUSAGE */
283 #endif /* _HAVE_GETRUSAGE */
287 timeval_diff(struct timeval *t1, struct timeval *t2)
289 int secdiff, usecdiff;
291 secdiff = t2->tv_sec - t1->tv_sec;
292 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
293 return (int)(usecdiff / 1000);
297 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
301 int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
302 int status, total_bytes_read;
303 static int devnull = -1;
306 struct timeval tv_start, tv_current;
308 debug3("Reading output from \'%s\'", src->cmdstring);
311 devnull = open("/dev/null", O_RDWR);
313 fatal("Couldn't open /dev/null: %s",
318 fatal("Couldn't open pipe: %s", strerror(errno));
320 (void)gettimeofday(&tv_start, NULL); /* record start time */
322 switch (pid = fork()) {
326 fatal("Couldn't fork: %s", strerror(errno));
329 dup2(devnull, STDIN_FILENO);
330 dup2(p[1], STDOUT_FILENO);
331 dup2(p[1], STDERR_FILENO);
336 execv(src->path, (char**)(src->args));
338 debug("(child) Couldn't exec '%s': %s",
339 src->cmdstring, strerror(errno));
341 default: /* Parent */
345 RAND_add(&pid, sizeof(&pid), 0.0);
349 /* Hash output from child */
352 cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
353 while (!error_abort && !cmd_eof) {
358 (void) gettimeofday(&tv_current, 0);
359 msec_elapsed = timeval_diff(&tv_start, &tv_current);
360 if (msec_elapsed >= entropy_timeout_current) {
364 msec_remaining = entropy_timeout_current - msec_elapsed;
367 FD_SET(p[0], &rdset);
368 tv.tv_sec = msec_remaining / 1000;
369 tv.tv_usec = (msec_remaining % 1000) * 1000;
371 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
373 RAND_add(&tv, sizeof(tv), 0.0);
384 bytes_read = read(p[0], buf, sizeof(buf));
385 } while (bytes_read == -1 && errno == EINTR);
386 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
387 if (bytes_read == -1) {
390 } else if (bytes_read) {
391 SHA1_Update(&sha, buf, bytes_read);
392 total_bytes_read += bytes_read;
400 debug("Command '%s': select() failed: %s",
401 src->cmdstring, strerror(errno));
407 SHA1_Final(hash, &sha);
411 debug3("Time elapsed: %d msec", msec_elapsed);
413 if (waitpid(pid, &status, 0) == -1) {
414 error("Couldn't wait for child '%s' completion: %s",
415 src->cmdstring, strerror(errno));
419 RAND_add(&status, sizeof(&status), 0.0);
423 * Closing p[0] on timeout causes the entropy command to
424 * SIGPIPE. Take whatever output we got, and mark this
427 debug2("Command '%s' timed out", src->cmdstring);
428 src->sticky_badness *= 2;
429 src->badness = src->sticky_badness;
430 return total_bytes_read;
433 if (WIFEXITED(status)) {
434 if (WEXITSTATUS(status) == 0) {
435 return total_bytes_read;
437 debug2("Command '%s' exit status was %d",
438 src->cmdstring, WEXITSTATUS(status));
439 src->badness = src->sticky_badness = 128;
442 } else if (WIFSIGNALED(status)) {
443 debug2("Command '%s' returned on uncaught signal %d !",
444 src->cmdstring, status);
445 src->badness = src->sticky_badness = 128;
452 stir_from_system(void)
454 double total_entropy_estimate;
457 total_entropy_estimate = 0;
460 RAND_add(&i, sizeof(i), 0.5);
461 total_entropy_estimate += 0.1;
464 RAND_add(&i, sizeof(i), 0.5);
465 total_entropy_estimate += 0.1;
468 RAND_add(&i, sizeof(i), 0.0);
470 RAND_add(&i, sizeof(i), 0.0);
472 total_entropy_estimate += stir_gettimeofday(1.0);
473 total_entropy_estimate += stir_clock(0.5);
474 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
476 return total_entropy_estimate;
480 stir_from_programs(void)
483 double entropy, total_entropy;
484 unsigned char hash[SHA_DIGEST_LENGTH];
487 for(c = 0; entropy_cmds[c].path != NULL; c++) {
488 if (!entropy_cmds[c].badness) {
489 /* Hash output from command */
490 entropy = hash_command_output(&entropy_cmds[c],
493 /* Scale back estimate by command's rate */
494 entropy *= entropy_cmds[c].rate;
496 /* Upper bound of entropy is SHA_DIGEST_LENGTH */
497 if (entropy > SHA_DIGEST_LENGTH)
498 entropy = SHA_DIGEST_LENGTH;
501 RAND_add(hash, sizeof(hash), entropy);
503 debug3("Got %0.2f bytes of entropy from '%s'",
504 entropy, entropy_cmds[c].cmdstring);
506 total_entropy += entropy;
508 /* Execution time should be a bit unpredictable */
509 total_entropy += stir_gettimeofday(0.05);
510 total_entropy += stir_clock(0.05);
511 total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
512 total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
514 debug2("Command '%s' disabled (badness %d)",
515 entropy_cmds[c].cmdstring,
516 entropy_cmds[c].badness);
518 if (entropy_cmds[c].badness > 0)
519 entropy_cmds[c].badness--;
523 return total_entropy;
527 * prng seedfile functions
530 prng_check_seedfile(char *filename)
535 * XXX raceable: eg replace seed between this stat and subsequent
536 * open. Not such a problem because we don't really trust the
538 * XXX: use secure path checking as elsewhere in OpenSSH
540 if (lstat(filename, &st) == -1) {
541 /* Give up on hard errors */
543 debug("WARNING: Couldn't stat random seed file "
544 "\"%.100s\": %s", filename, strerror(errno));
549 if (!S_ISREG(st.st_mode))
550 fatal("PRNG seedfile %.100s is not a regular file",
553 /* mode 0600, owned by root or the current user? */
554 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
555 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
556 "owned by uid %li", filename, (long int)getuid());
564 prng_write_seedfile(void)
567 unsigned char seed[SEED_FILE_SIZE];
568 char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
572 pw = getpwuid(getuid());
574 fatal("Couldn't get password entry for current user "
575 "(%li): %s", (long int)getuid(), strerror(errno));
577 /* Try to ensure that the parent directory is there */
578 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
580 if (mkdir(filename, 0700) < 0 && errno != EEXIST)
581 fatal("mkdir %.200s: %s", filename, strerror(errno));
583 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
586 strlcpy(tmpseed, filename, sizeof(tmpseed));
587 if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
589 fatal("PRNG seed filename too long");
591 if (RAND_bytes(seed, sizeof(seed)) <= 0)
592 fatal("PRNG seed extraction failed");
594 /* Don't care if the seed doesn't exist */
595 prng_check_seedfile(filename);
597 old_umask = umask(0177);
599 if ((fd = mkstemp(tmpseed)) == -1) {
600 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
601 "(%.100s)", tmpseed, strerror(errno));
603 debug("writing PRNG seed to file %.100s", tmpseed);
604 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
608 fatal("problem writing PRNG seedfile %.100s "
609 "(%.100s)", filename, strerror(save_errno));
612 debug("moving temporary PRNG seed to file %.100s", filename);
613 if (rename(tmpseed, filename) == -1) {
616 fatal("problem renaming PRNG seedfile from %.100s "
617 "to %.100s (%.100s)", tmpseed, filename,
618 strerror(save_errno));
625 prng_read_seedfile(void)
628 char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
631 pw = getpwuid(getuid());
633 fatal("Couldn't get password entry for current user "
634 "(%li): %s", (long int)getuid(), strerror(errno));
636 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
639 debug("loading PRNG seed from file %.100s", filename);
641 if (!prng_check_seedfile(filename)) {
642 verbose("Random seed file not found or invalid, ignoring.");
646 /* open the file and read in the seed */
647 fd = open(filename, O_RDONLY);
649 fatal("could not open PRNG seedfile %.100s (%.100s)",
650 filename, strerror(errno));
652 if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
653 verbose("invalid or short read from PRNG seedfile "
654 "%.100s - ignoring", filename);
655 memset(seed, '\0', sizeof(seed));
659 /* stir in the seed, with estimated entropy zero */
660 RAND_add(&seed, sizeof(seed), 0.0);
665 * entropy command initialisation functions
668 prng_read_commands(char *cmdfilename)
670 char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
672 entropy_cmd_t *entcmd;
674 int cur_cmd, linenum, num_cmds, arg;
676 if ((f = fopen(cmdfilename, "r")) == NULL) {
677 fatal("couldn't read entropy commands file %.100s: %.100s",
678 cmdfilename, strerror(errno));
682 entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
685 cur_cmd = linenum = 0;
686 while (fgets(line, sizeof(line), f)) {
689 /* Skip leading whitespace, blank lines and comments */
690 cp = line + strspn(line, WHITESPACE);
691 if ((*cp == 0) || (*cp == '#'))
692 continue; /* done with this line */
695 * The first non-whitespace char should be a double quote
696 * delimiting the commandline
699 error("bad entropy command, %.100s line %d",
700 cmdfilename, linenum);
705 * First token, command args (incl. argv[0]) in double
708 cp = strtok(cp, "\"");
710 error("missing or bad command string, %.100s "
711 "line %d -- ignored", cmdfilename, linenum);
714 strlcpy(cmd, cp, sizeof(cmd));
716 /* Second token, full command path */
717 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
718 error("missing command path, %.100s "
719 "line %d -- ignored", cmdfilename, linenum);
723 /* Did configure mark this as dead? */
724 if (strncmp("undef", cp, 5) == 0)
727 strlcpy(path, cp, sizeof(path));
729 /* Third token, entropy rate estimate for this command */
730 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
731 error("missing entropy estimate, %.100s "
732 "line %d -- ignored", cmdfilename, linenum);
735 est = strtod(cp, NULL);
738 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
739 error("garbage at end of line %d in %.100s "
740 "-- ignored", linenum, cmdfilename);
744 /* save the command for debug messages */
745 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
747 /* split the command args */
748 cp = strtok(cmd, WHITESPACE);
751 entcmd[cur_cmd].args[arg] = xstrdup(cp);
753 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
755 if (strtok(NULL, WHITESPACE))
756 error("ignored extra commands (max %d), %.100s "
757 "line %d", NUM_ARGS, cmdfilename, linenum);
759 /* Copy the command path and rate estimate */
760 entcmd[cur_cmd].path = xstrdup(path);
761 entcmd[cur_cmd].rate = est;
763 /* Initialise other values */
764 entcmd[cur_cmd].sticky_badness = 1;
769 * If we've filled the array, reallocate it twice the size
770 * Do this now because even if this we're on the last
771 * command we need another slot to mark the last entry
773 if (cur_cmd == num_cmds) {
775 entcmd = xrealloc(entcmd, num_cmds,
776 sizeof(entropy_cmd_t));
780 /* zero the last entry */
781 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
784 entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
785 sizeof(entropy_cmd_t));
787 debug("Loaded %d entropy commands from %.100s", cur_cmd,
791 return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
797 fprintf(stderr, "Usage: %s [options]\n", __progname);
798 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
799 fprintf(stderr, " Multiple -v increases verbosity.\n");
800 fprintf(stderr, " -x Force output in hexadecimal (for debugging)\n");
801 fprintf(stderr, " -X Force output in binary\n");
802 fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n",
807 main(int argc, char **argv)
810 int ret, ch, debug_level, output_hex, bytes;
814 __progname = ssh_get_progname(argv[0]);
815 log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
817 ll = SYSLOG_LEVEL_INFO;
818 debug_level = output_hex = 0;
819 bytes = OUTPUT_SEED_SIZE;
821 /* Don't write binary data to a tty, unless we are forced to */
822 if (isatty(STDOUT_FILENO))
825 while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
829 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
838 if ((bytes = atoi(optarg)) <= 0)
839 fatal("Invalid number of output bytes");
845 error("Invalid commandline option");
850 log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
852 #ifdef USE_SEED_FILES
853 prng_read_seedfile();
856 buf = xmalloc(bytes);
859 * Seed the RNG from wherever we can
862 /* Take whatever is on the stack, but don't credit it */
863 RAND_add(buf, bytes, 0);
865 debug("Seeded RNG with %i bytes from system calls",
866 (int)stir_from_system());
868 /* try prngd, fall back to commands if prngd fails or not configured */
869 if (seed_from_prngd(buf, bytes) == 0) {
870 RAND_add(buf, bytes, bytes);
872 /* Read in collection commands */
873 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
874 fatal("PRNG initialisation failed -- exiting.");
875 debug("Seeded RNG with %i bytes from programs",
876 (int)stir_from_programs());
879 #ifdef USE_SEED_FILES
880 prng_write_seedfile();
884 * Write the seed to stdout
888 fatal("Not enough entropy in RNG");
890 if (RAND_bytes(buf, bytes) <= 0)
891 fatal("Couldn't extract entropy from PRNG");
894 for(ret = 0; ret < bytes; ret++)
895 printf("%02x", (unsigned char)(buf[ret]));
898 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
900 memset(buf, '\0', bytes);
903 return ret == bytes ? 0 : 1;
907 * We may attempt to re-seed during mkstemp if we are using the one in the
908 * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
909 * need our own seed_rng(). We must also check that we have enough entropy.
915 fatal("Not enough entropy in RNG");