ssh-rand-helper.c

   1 /*
   2  * Copyright (c) 2001-2002 Damien Miller.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   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.
  12  *
  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.
  23  */
  24
  25 #include "includes.h"
  26
  27 #include <sys/types.h>
  28 #include <sys/resource.h>
  29 #include <sys/stat.h>
  30 #include <sys/wait.h>
  31 #include <sys/socket.h>
  32
  33 #include <stdarg.h>
  34 #include <stddef.h>
  35
  36 #include <netinet/in.h>
  37 #include <arpa/inet.h>
  38
  39 #ifdef HAVE_SYS_UN_H
  40 # include <sys/un.h>
  41 #endif
  42
  43 #include <errno.h>
  44 #include <fcntl.h>
  45 #include <pwd.h>
  46 #include <signal.h>
  47 #include <time.h>
  48 #include <unistd.h>
  49
  50 #include <openssl/rand.h>
  51 #include <openssl/sha.h>
  52 #include <openssl/crypto.h>
  53
  54 /* SunOS 4.4.4 needs this */
  55 #ifdef HAVE_FLOATINGPOINT_H
  56 # include <floatingpoint.h>
  57 #endif /* HAVE_FLOATINGPOINT_H */
  58
  59 #include "misc.h"
  60 #include "xmalloc.h"
  61 #include "atomicio.h"
  62 #include "pathnames.h"
  63 #include "log.h"
  64
  65 /* Number of bytes we write out */
  66 #define OUTPUT_SEED_SIZE        48
  67
  68 /* Length of on-disk seedfiles */
  69 #define SEED_FILE_SIZE          1024
  70
  71 /* Maximum number of command-line arguments to read from file */
  72 #define NUM_ARGS                10
  73
  74 /* Minimum number of usable commands to be considered sufficient */
  75 #define MIN_ENTROPY_SOURCES     16
  76
  77 /* Path to on-disk seed file (relative to user's home directory */
  78 #ifndef SSH_PRNG_SEED_FILE
  79 # define SSH_PRNG_SEED_FILE      _PATH_SSH_USER_DIR"/prng_seed"
  80 #endif
  81
  82 /* Path to PRNG commands list */
  83 #ifndef SSH_PRNG_COMMAND_FILE
  84 # define SSH_PRNG_COMMAND_FILE   SSHDIR "/ssh_prng_cmds"
  85 #endif
  86
  87 extern char *__progname;
  88
  89 #define WHITESPACE " \t\n"
  90
  91 #ifndef RUSAGE_SELF
  92 # define RUSAGE_SELF 0
  93 #endif
  94 #ifndef RUSAGE_CHILDREN
  95 # define RUSAGE_CHILDREN 0
  96 #endif
  97
  98 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
  99 # define USE_SEED_FILES
 100 #endif
 101
 102 typedef struct {
 103         /* Proportion of data that is entropy */
 104         double rate;
 105         /* Counter goes positive if this command times out */
 106         unsigned int badness;
 107         /* Increases by factor of two each timeout */
 108         unsigned int sticky_badness;
 109         /* Path to executable */
 110         char *path;
 111         /* argv to pass to executable */
 112         char *args[NUM_ARGS]; /* XXX: arbitrary limit */
 113         /* full command string (debug) */
 114         char *cmdstring;
 115 } entropy_cmd_t;
 116
 117 /* slow command timeouts (all in milliseconds) */
 118 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
 119 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
 120
 121 /* this is initialised from a file, by prng_read_commands() */
 122 static entropy_cmd_t *entropy_cmds = NULL;
 123
 124 /* Prototypes */
 125 double stir_from_system(void);
 126 double stir_from_programs(void);
 127 double stir_gettimeofday(double entropy_estimate);
 128 double stir_clock(double entropy_estimate);
 129 double stir_rusage(int who, double entropy_estimate);
 130 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
 131 int get_random_bytes_prngd(unsigned char *buf, int len,
 132     unsigned short tcp_port, char *socket_path);
 133
 134 /*
 135  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
 136  * listening either on 'tcp_port', or via Unix domain socket at *
 137  * 'socket_path'.
 138  * Either a non-zero tcp_port or a non-null socket_path must be
 139  * supplied.
 140  * Returns 0 on success, -1 on error
 141  */
 142 int
 143 get_random_bytes_prngd(unsigned char *buf, int len,
 144     unsigned short tcp_port, char *socket_path)
 145 {
 146         int fd, addr_len, rval, errors;
 147         u_char msg[2];
 148         struct sockaddr_storage addr;
 149         struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
 150         struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
 151         mysig_t old_sigpipe;
 152
 153         /* Sanity checks */
 154         if (socket_path == NULL && tcp_port == 0)
 155                 fatal("You must specify a port or a socket");
 156         if (socket_path != NULL &&
 157             strlen(socket_path) >= sizeof(addr_un->sun_path))
 158                 fatal("Random pool path is too long");
 159         if (len <= 0 || len > 255)
 160                 fatal("Too many bytes (%d) to read from PRNGD", len);
 161
 162         memset(&addr, '\0', sizeof(addr));
 163
 164         if (tcp_port != 0) {
 165                 addr_in->sin_family = AF_INET;
 166                 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 167                 addr_in->sin_port = htons(tcp_port);
 168                 addr_len = sizeof(*addr_in);
 169         } else {
 170                 addr_un->sun_family = AF_UNIX;
 171                 strlcpy(addr_un->sun_path, socket_path,
 172                     sizeof(addr_un->sun_path));
 173                 addr_len = offsetof(struct sockaddr_un, sun_path) +
 174                     strlen(socket_path) + 1;
 175         }
 176
 177         old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
 178
 179         errors = 0;
 180         rval = -1;
 181 reopen:
 182         fd = socket(addr.ss_family, SOCK_STREAM, 0);
 183         if (fd == -1) {
 184                 error("Couldn't create socket: %s", strerror(errno));
 185                 goto done;
 186         }
 187
 188         if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
 189                 if (tcp_port != 0) {
 190                         error("Couldn't connect to PRNGD port %d: %s",
 191                             tcp_port, strerror(errno));
 192                 } else {
 193                         error("Couldn't connect to PRNGD socket \"%s\": %s",
 194                             addr_un->sun_path, strerror(errno));
 195                 }
 196                 goto done;
 197         }
 198
 199         /* Send blocking read request to PRNGD */
 200         msg[0] = 0x02;
 201         msg[1] = len;
 202
 203         if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
 204                 if (errno == EPIPE && errors < 10) {
 205                         close(fd);
 206                         errors++;
 207                         goto reopen;
 208                 }
 209                 error("Couldn't write to PRNGD socket: %s",
 210                     strerror(errno));
 211                 goto done;
 212         }
 213
 214         if (atomicio(read, fd, buf, len) != (size_t)len) {
 215                 if (errno == EPIPE && errors < 10) {
 216                         close(fd);
 217                         errors++;
 218                         goto reopen;
 219                 }
 220                 error("Couldn't read from PRNGD socket: %s",
 221                     strerror(errno));
 222                 goto done;
 223         }
 224
 225         rval = 0;
 226 done:
 227         mysignal(SIGPIPE, old_sigpipe);
 228         if (fd != -1)
 229                 close(fd);
 230         return rval;
 231 }
 232
 233 static int
 234 seed_from_prngd(unsigned char *buf, size_t bytes)
 235 {
 236 #ifdef PRNGD_PORT
 237         debug("trying egd/prngd port %d", PRNGD_PORT);
 238         if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
 239                 return 0;
 240 #endif
 241 #ifdef PRNGD_SOCKET
 242         debug("trying egd/prngd socket %s", PRNGD_SOCKET);
 243         if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
 244                 return 0;
 245 #endif
 246         return -1;
 247 }
 248
 249 double
 250 stir_gettimeofday(double entropy_estimate)
 251 {
 252         struct timeval tv;
 253
 254         if (gettimeofday(&tv, NULL) == -1)
 255                 fatal("Couldn't gettimeofday: %s", strerror(errno));
 256
 257         RAND_add(&tv, sizeof(tv), entropy_estimate);
 258
 259         return entropy_estimate;
 260 }
 261
 262 double
 263 stir_clock(double entropy_estimate)
 264 {
 265 #ifdef HAVE_CLOCK
 266         clock_t c;
 267
 268         c = clock();
 269         RAND_add(&c, sizeof(c), entropy_estimate);
 270
 271         return entropy_estimate;
 272 #else /* _HAVE_CLOCK */
 273         return 0;
 274 #endif /* _HAVE_CLOCK */
 275 }
 276
 277 double
 278 stir_rusage(int who, double entropy_estimate)
 279 {
 280 #ifdef HAVE_GETRUSAGE
 281         struct rusage ru;
 282
 283         if (getrusage(who, &ru) == -1)
 284                 return 0;
 285
 286         RAND_add(&ru, sizeof(ru), entropy_estimate);
 287
 288         return entropy_estimate;
 289 #else /* _HAVE_GETRUSAGE */
 290         return 0;
 291 #endif /* _HAVE_GETRUSAGE */
 292 }
 293
 294 static int
 295 timeval_diff(struct timeval *t1, struct timeval *t2)
 296 {
 297         int secdiff, usecdiff;
 298
 299         secdiff = t2->tv_sec - t1->tv_sec;
 300         usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
 301         return (int)(usecdiff / 1000);
 302 }
 303
 304 double
 305 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
 306 {
 307         char buf[8192];
 308         fd_set rdset;
 309         int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
 310         int status, total_bytes_read;
 311         static int devnull = -1;
 312         pid_t pid;
 313         SHA_CTX sha;
 314         struct timeval tv_start, tv_current;
 315
 316         debug3("Reading output from \'%s\'", src->cmdstring);
 317
 318         if (devnull == -1) {
 319                 devnull = open("/dev/null", O_RDWR);
 320                 if (devnull == -1)
 321                         fatal("Couldn't open /dev/null: %s",
 322                             strerror(errno));
 323         }
 324
 325         if (pipe(p) == -1)
 326                 fatal("Couldn't open pipe: %s", strerror(errno));
 327
 328         (void)gettimeofday(&tv_start, NULL); /* record start time */
 329
 330         switch (pid = fork()) {
 331                 case -1: /* Error */
 332                         close(p[0]);
 333                         close(p[1]);
 334                         fatal("Couldn't fork: %s", strerror(errno));
 335                         /* NOTREACHED */
 336                 case 0: /* Child */
 337                         dup2(devnull, STDIN_FILENO);
 338                         dup2(p[1], STDOUT_FILENO);
 339                         dup2(p[1], STDERR_FILENO);
 340                         close(p[0]);
 341                         close(p[1]);
 342                         close(devnull);
 343
 344                         execv(src->path, (char**)(src->args));
 345
 346                         debug("(child) Couldn't exec '%s': %s",
 347                             src->cmdstring, strerror(errno));
 348                         _exit(-1);
 349                 default: /* Parent */
 350                         break;
 351         }
 352
 353         RAND_add(&pid, sizeof(&pid), 0.0);
 354
 355         close(p[1]);
 356
 357         /* Hash output from child */
 358         SHA1_Init(&sha);
 359
 360         cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
 361         while (!error_abort && !cmd_eof) {
 362                 int ret;
 363                 struct timeval tv;
 364                 int msec_remaining;
 365
 366                 (void) gettimeofday(&tv_current, 0);
 367                 msec_elapsed = timeval_diff(&tv_start, &tv_current);
 368                 if (msec_elapsed >= entropy_timeout_current) {
 369                         error_abort=1;
 370                         continue;
 371                 }
 372                 msec_remaining = entropy_timeout_current - msec_elapsed;
 373
 374                 FD_ZERO(&rdset);
 375                 FD_SET(p[0], &rdset);
 376                 tv.tv_sec = msec_remaining / 1000;
 377                 tv.tv_usec = (msec_remaining % 1000) * 1000;
 378
 379                 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
 380
 381                 RAND_add(&tv, sizeof(tv), 0.0);
 382
 383                 switch (ret) {
 384                 case 0:
 385                         /* timer expired */
 386                         error_abort = 1;
 387                         kill(pid, SIGINT);
 388                         break;
 389                 case 1:
 390                         /* command input */
 391                         do {
 392                                 bytes_read = read(p[0], buf, sizeof(buf));
 393                         } while (bytes_read == -1 && errno == EINTR);
 394                         RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
 395                         if (bytes_read == -1) {
 396                                 error_abort = 1;
 397                                 break;
 398                         } else if (bytes_read) {
 399                                 SHA1_Update(&sha, buf, bytes_read);
 400                                 total_bytes_read += bytes_read;
 401                         } else {
 402                                 cmd_eof = 1;
 403                         }
 404                         break;
 405                 case -1:
 406                 default:
 407                         /* error */
 408                         debug("Command '%s': select() failed: %s",
 409                             src->cmdstring, strerror(errno));
 410                         error_abort = 1;
 411                         break;
 412                 }
 413         }
 414
 415         SHA1_Final(hash, &sha);
 416
 417         close(p[0]);
 418
 419         debug3("Time elapsed: %d msec", msec_elapsed);
 420
 421         if (waitpid(pid, &status, 0) == -1) {
 422                 error("Couldn't wait for child '%s' completion: %s",
 423                     src->cmdstring, strerror(errno));
 424                 return 0.0;
 425         }
 426
 427         RAND_add(&status, sizeof(&status), 0.0);
 428
 429         if (error_abort) {
 430                 /*
 431                  * Closing p[0] on timeout causes the entropy command to
 432                  * SIGPIPE. Take whatever output we got, and mark this
 433                  * command as slow
 434                  */
 435                 debug2("Command '%s' timed out", src->cmdstring);
 436                 src->sticky_badness *= 2;
 437                 src->badness = src->sticky_badness;
 438                 return total_bytes_read;
 439         }
 440
 441         if (WIFEXITED(status)) {
 442                 if (WEXITSTATUS(status) == 0) {
 443                         return total_bytes_read;
 444                 } else {
 445                         debug2("Command '%s' exit status was %d",
 446                             src->cmdstring, WEXITSTATUS(status));
 447                         src->badness = src->sticky_badness = 128;
 448                         return 0.0;
 449                 }
 450         } else if (WIFSIGNALED(status)) {
 451                 debug2("Command '%s' returned on uncaught signal %d !",
 452                     src->cmdstring, status);
 453                 src->badness = src->sticky_badness = 128;
 454                 return 0.0;
 455         } else
 456                 return 0.0;
 457 }
 458
 459 double
 460 stir_from_system(void)
 461 {
 462         double total_entropy_estimate;
 463         long int i;
 464
 465         total_entropy_estimate = 0;
 466
 467         i = getpid();
 468         RAND_add(&i, sizeof(i), 0.5);
 469         total_entropy_estimate += 0.1;
 470
 471         i = getppid();
 472         RAND_add(&i, sizeof(i), 0.5);
 473         total_entropy_estimate += 0.1;
 474
 475         i = getuid();
 476         RAND_add(&i, sizeof(i), 0.0);
 477         i = getgid();
 478         RAND_add(&i, sizeof(i), 0.0);
 479
 480         total_entropy_estimate += stir_gettimeofday(1.0);
 481         total_entropy_estimate += stir_clock(0.5);
 482         total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
 483
 484         return total_entropy_estimate;
 485 }
 486
 487 double
 488 stir_from_programs(void)
 489 {
 490         int c;
 491         double entropy, total_entropy;
 492         unsigned char hash[SHA_DIGEST_LENGTH];
 493
 494         total_entropy = 0;
 495         for(c = 0; entropy_cmds[c].path != NULL; c++) {
 496                 if (!entropy_cmds[c].badness) {
 497                         /* Hash output from command */
 498                         entropy = hash_command_output(&entropy_cmds[c],
 499                             hash);
 500
 501                         /* Scale back estimate by command's rate */
 502                         entropy *= entropy_cmds[c].rate;
 503
 504                         /* Upper bound of entropy is SHA_DIGEST_LENGTH */
 505                         if (entropy > SHA_DIGEST_LENGTH)
 506                                 entropy = SHA_DIGEST_LENGTH;
 507
 508                         /* Stir it in */
 509                         RAND_add(hash, sizeof(hash), entropy);
 510
 511                         debug3("Got %0.2f bytes of entropy from '%s'",
 512                             entropy, entropy_cmds[c].cmdstring);
 513
 514                         total_entropy += entropy;
 515
 516                         /* Execution time should be a bit unpredictable */
 517                         total_entropy += stir_gettimeofday(0.05);
 518                         total_entropy += stir_clock(0.05);
 519                         total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
 520                         total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
 521                 } else {
 522                         debug2("Command '%s' disabled (badness %d)",
 523                             entropy_cmds[c].cmdstring,
 524                             entropy_cmds[c].badness);
 525
 526                         if (entropy_cmds[c].badness > 0)
 527                                 entropy_cmds[c].badness--;
 528                 }
 529         }
 530
 531         return total_entropy;
 532 }
 533
 534 /*
 535  * prng seedfile functions
 536  */
 537 int
 538 prng_check_seedfile(char *filename)
 539 {
 540         struct stat st;
 541
 542         /*
 543          * XXX raceable: eg replace seed between this stat and subsequent
 544          * open. Not such a problem because we don't really trust the
 545          * seed file anyway.
 546          * XXX: use secure path checking as elsewhere in OpenSSH
 547          */
 548         if (lstat(filename, &st) == -1) {
 549                 /* Give up on hard errors */
 550                 if (errno != ENOENT)
 551                         debug("WARNING: Couldn't stat random seed file "
 552                             "\"%.100s\": %s", filename, strerror(errno));
 553                 return 0;
 554         }
 555
 556         /* regular file? */
 557         if (!S_ISREG(st.st_mode))
 558                 fatal("PRNG seedfile %.100s is not a regular file",
 559                     filename);
 560
 561         /* mode 0600, owned by root or the current user? */
 562         if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
 563                 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
 564                     "owned by uid %li", filename, (long int)getuid());
 565                 return 0;
 566         }
 567
 568         return 1;
 569 }
 570
 571 void
 572 prng_write_seedfile(void)
 573 {
 574         int fd, save_errno;
 575         unsigned char seed[SEED_FILE_SIZE];
 576         char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
 577         struct passwd *pw;
 578         mode_t old_umask;
 579
 580         pw = getpwuid(getuid());
 581         if (pw == NULL)
 582                 fatal("Couldn't get password entry for current user "
 583                     "(%li): %s", (long int)getuid(), strerror(errno));
 584
 585         /* Try to ensure that the parent directory is there */
 586         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 587             _PATH_SSH_USER_DIR);
 588         if (mkdir(filename, 0700) < 0 && errno != EEXIST)
 589                 fatal("mkdir %.200s: %s", filename, strerror(errno));
 590
 591         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 592             SSH_PRNG_SEED_FILE);
 593
 594         strlcpy(tmpseed, filename, sizeof(tmpseed));
 595         if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
 596             sizeof(tmpseed))
 597                 fatal("PRNG seed filename too long");
 598
 599         if (RAND_bytes(seed, sizeof(seed)) <= 0)
 600                 fatal("PRNG seed extraction failed");
 601
 602         /* Don't care if the seed doesn't exist */
 603         prng_check_seedfile(filename);
 604
 605         old_umask = umask(0177);
 606
 607         if ((fd = mkstemp(tmpseed)) == -1) {
 608                 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
 609                     "(%.100s)", tmpseed, strerror(errno));
 610         } else {
 611                 debug("writing PRNG seed to file %.100s", tmpseed);
 612                 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 613                         save_errno = errno;
 614                         close(fd);
 615                         unlink(tmpseed);
 616                         fatal("problem writing PRNG seedfile %.100s "
 617                             "(%.100s)", filename, strerror(save_errno));
 618                 }
 619                 close(fd);
 620                 debug("moving temporary PRNG seed to file %.100s", filename);
 621                 if (rename(tmpseed, filename) == -1) {
 622                         save_errno = errno;
 623                         unlink(tmpseed);
 624                         fatal("problem renaming PRNG seedfile from %.100s "
 625                             "to %.100s (%.100s)", tmpseed, filename,
 626                             strerror(save_errno));
 627                 }
 628         }
 629         umask(old_umask);
 630 }
 631
 632 void
 633 prng_read_seedfile(void)
 634 {
 635         int fd;
 636         char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
 637         struct passwd *pw;
 638
 639         pw = getpwuid(getuid());
 640         if (pw == NULL)
 641                 fatal("Couldn't get password entry for current user "
 642                     "(%li): %s", (long int)getuid(), strerror(errno));
 643
 644         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 645                 SSH_PRNG_SEED_FILE);
 646
 647         debug("loading PRNG seed from file %.100s", filename);
 648
 649         if (!prng_check_seedfile(filename)) {
 650                 verbose("Random seed file not found or invalid, ignoring.");
 651                 return;
 652         }
 653
 654         /* open the file and read in the seed */
 655         fd = open(filename, O_RDONLY);
 656         if (fd == -1)
 657                 fatal("could not open PRNG seedfile %.100s (%.100s)",
 658                     filename, strerror(errno));
 659
 660         if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 661                 verbose("invalid or short read from PRNG seedfile "
 662                     "%.100s - ignoring", filename);
 663                 memset(seed, '\0', sizeof(seed));
 664         }
 665         close(fd);
 666
 667         /* stir in the seed, with estimated entropy zero */
 668         RAND_add(&seed, sizeof(seed), 0.0);
 669 }
 670
 671
 672 /*
 673  * entropy command initialisation functions
 674  */
 675 int
 676 prng_read_commands(char *cmdfilename)
 677 {
 678         char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
 679         double est;
 680         entropy_cmd_t *entcmd;
 681         FILE *f;
 682         int cur_cmd, linenum, num_cmds, arg;
 683
 684         if ((f = fopen(cmdfilename, "r")) == NULL) {
 685                 fatal("couldn't read entropy commands file %.100s: %.100s",
 686                     cmdfilename, strerror(errno));
 687         }
 688
 689         num_cmds = 64;
 690         entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
 691
 692         /* Read in file */
 693         cur_cmd = linenum = 0;
 694         while (fgets(line, sizeof(line), f)) {
 695                 linenum++;
 696
 697                 /* Skip leading whitespace, blank lines and comments */
 698                 cp = line + strspn(line, WHITESPACE);
 699                 if ((*cp == 0) || (*cp == '#'))
 700                         continue; /* done with this line */
 701
 702                 /*
 703                  * The first non-whitespace char should be a double quote
 704                  * delimiting the commandline
 705                  */
 706                 if (*cp != '"') {
 707                         error("bad entropy command, %.100s line %d",
 708                             cmdfilename, linenum);
 709                         continue;
 710                 }
 711
 712                 /*
 713                  * First token, command args (incl. argv[0]) in double
 714                  * quotes
 715                  */
 716                 cp = strtok(cp, "\"");
 717                 if (cp == NULL) {
 718                         error("missing or bad command string, %.100s "
 719                             "line %d -- ignored", cmdfilename, linenum);
 720                         continue;
 721                 }
 722                 strlcpy(cmd, cp, sizeof(cmd));
 723
 724                 /* Second token, full command path */
 725                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 726                         error("missing command path, %.100s "
 727                             "line %d -- ignored", cmdfilename, linenum);
 728                         continue;
 729                 }
 730
 731                 /* Did configure mark this as dead? */
 732                 if (strncmp("undef", cp, 5) == 0)
 733                         continue;
 734
 735                 strlcpy(path, cp, sizeof(path));
 736
 737                 /* Third token, entropy rate estimate for this command */
 738                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 739                         error("missing entropy estimate, %.100s "
 740                             "line %d -- ignored", cmdfilename, linenum);
 741                         continue;
 742                 }
 743                 est = strtod(cp, NULL);
 744
 745                 /* end of line */
 746                 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
 747                         error("garbage at end of line %d in %.100s "
 748                             "-- ignored", linenum, cmdfilename);
 749                         continue;
 750                 }
 751
 752                 /* save the command for debug messages */
 753                 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
 754
 755                 /* split the command args */
 756                 cp = strtok(cmd, WHITESPACE);
 757                 arg = 0;
 758                 do {
 759                         entcmd[cur_cmd].args[arg] = xstrdup(cp);
 760                         arg++;
 761                 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
 762
 763                 if (strtok(NULL, WHITESPACE))
 764                         error("ignored extra commands (max %d), %.100s "
 765                             "line %d", NUM_ARGS, cmdfilename, linenum);
 766
 767                 /* Copy the command path and rate estimate */
 768                 entcmd[cur_cmd].path = xstrdup(path);
 769                 entcmd[cur_cmd].rate = est;
 770
 771                 /* Initialise other values */
 772                 entcmd[cur_cmd].sticky_badness = 1;
 773
 774                 cur_cmd++;
 775
 776                 /*
 777                  * If we've filled the array, reallocate it twice the size
 778                  * Do this now because even if this we're on the last
 779                  * command we need another slot to mark the last entry
 780                  */
 781                 if (cur_cmd == num_cmds) {
 782                         num_cmds *= 2;
 783                         entcmd = xrealloc(entcmd, num_cmds,
 784                             sizeof(entropy_cmd_t));
 785                 }
 786         }
 787
 788         /* zero the last entry */
 789         memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
 790
 791         /* trim to size */
 792         entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
 793             sizeof(entropy_cmd_t));
 794
 795         debug("Loaded %d entropy commands from %.100s", cur_cmd,
 796             cmdfilename);
 797
 798         fclose(f);
 799         return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
 800 }
 801
 802 void
 803 usage(void)
 804 {
 805         fprintf(stderr, "Usage: %s [options]\n", __progname);
 806         fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
 807         fprintf(stderr, "              Multiple -v increases verbosity.\n");
 808         fprintf(stderr, "  -x          Force output in hexadecimal (for debugging)\n");
 809         fprintf(stderr, "  -X          Force output in binary\n");
 810         fprintf(stderr, "  -b bytes    Number of bytes to output (default %d)\n",
 811             OUTPUT_SEED_SIZE);
 812 }
 813
 814 int
 815 main(int argc, char **argv)
 816 {
 817         unsigned char *buf;
 818         int ret, ch, debug_level, output_hex, bytes;
 819         extern char *optarg;
 820         LogLevel ll;
 821
 822         __progname = ssh_get_progname(argv[0]);
 823         log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
 824
 825         ll = SYSLOG_LEVEL_INFO;
 826         debug_level = output_hex = 0;
 827         bytes = OUTPUT_SEED_SIZE;
 828
 829         /* Don't write binary data to a tty, unless we are forced to */
 830         if (isatty(STDOUT_FILENO))
 831                 output_hex = 1;
 832
 833         while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
 834                 switch (ch) {
 835                 case 'v':
 836                         if (debug_level < 3)
 837                                 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
 838                         break;
 839                 case 'x':
 840                         output_hex = 1;
 841                         break;
 842                 case 'X':
 843                         output_hex = 0;
 844                         break;
 845                 case 'b':
 846                         if ((bytes = atoi(optarg)) <= 0)
 847                                 fatal("Invalid number of output bytes");
 848                         break;
 849                 case 'h':
 850                         usage();
 851                         exit(0);
 852                 default:
 853                         error("Invalid commandline option");
 854                         usage();
 855                 }
 856         }
 857
 858         log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
 859
 860 #ifdef USE_SEED_FILES
 861         prng_read_seedfile();
 862 #endif
 863
 864         buf = xmalloc(bytes);
 865
 866         /*
 867          * Seed the RNG from wherever we can
 868          */
 869
 870         /* Take whatever is on the stack, but don't credit it */
 871         RAND_add(buf, bytes, 0);
 872
 873         debug("Seeded RNG with %i bytes from system calls",
 874             (int)stir_from_system());
 875
 876         /* try prngd, fall back to commands if prngd fails or not configured */
 877         if (seed_from_prngd(buf, bytes) == 0) {
 878                 RAND_add(buf, bytes, bytes);
 879         } else {
 880                 /* Read in collection commands */
 881                 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
 882                         fatal("PRNG initialisation failed -- exiting.");
 883                 debug("Seeded RNG with %i bytes from programs",
 884                     (int)stir_from_programs());
 885         }
 886
 887 #ifdef USE_SEED_FILES
 888         prng_write_seedfile();
 889 #endif
 890
 891         /*
 892          * Write the seed to stdout
 893          */
 894
 895         if (!RAND_status())
 896                 fatal("Not enough entropy in RNG");
 897
 898         if (RAND_bytes(buf, bytes) <= 0)
 899                 fatal("Couldn't extract entropy from PRNG");
 900
 901         if (output_hex) {
 902                 for(ret = 0; ret < bytes; ret++)
 903                         printf("%02x", (unsigned char)(buf[ret]));
 904                 printf("\n");
 905         } else
 906                 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
 907
 908         memset(buf, '\0', bytes);
 909         xfree(buf);
 910
 911         return ret == bytes ? 0 : 1;
 912 }
 913
 914 /*
 915  * We may attempt to re-seed during mkstemp if we are using the one in the
 916  * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
 917  * need our own seed_rng().  We must also check that we have enough entropy.
 918  */
 919 void
 920 seed_rng(void)
 921 {
 922         if (!RAND_status())
 923                 fatal("Not enough entropy in RNG");
 924 }