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