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 <openssl/rand.h>
  28 #include <openssl/sha.h>
  29 #include <openssl/crypto.h>
  30
  31 /* SunOS 4.4.4 needs this */
  32 #ifdef HAVE_FLOATINGPOINT_H
  33 # include <floatingpoint.h>
  34 #endif /* HAVE_FLOATINGPOINT_H */
  35
  36 #include "misc.h"
  37 #include "xmalloc.h"
  38 #include "atomicio.h"
  39 #include "pathnames.h"
  40 #include "log.h"
  41
  42 RCSID("$Id: ssh-rand-helper.c,v 1.23 2005/02/16 02:32:30 dtucker Exp $");
  43
  44 /* Number of bytes we write out */
  45 #define OUTPUT_SEED_SIZE        48
  46
  47 /* Length of on-disk seedfiles */
  48 #define SEED_FILE_SIZE          1024
  49
  50 /* Maximum number of command-line arguments to read from file */
  51 #define NUM_ARGS                10
  52
  53 /* Minimum number of usable commands to be considered sufficient */
  54 #define MIN_ENTROPY_SOURCES     16
  55
  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"
  59 #endif
  60
  61 /* Path to PRNG commands list */
  62 #ifndef SSH_PRNG_COMMAND_FILE
  63 # define SSH_PRNG_COMMAND_FILE   SSHDIR "/ssh_prng_cmds"
  64 #endif
  65
  66 extern char *__progname;
  67
  68 #define WHITESPACE " \t\n"
  69
  70 #ifndef RUSAGE_SELF
  71 # define RUSAGE_SELF 0
  72 #endif
  73 #ifndef RUSAGE_CHILDREN
  74 # define RUSAGE_CHILDREN 0
  75 #endif
  76
  77 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
  78 # define USE_SEED_FILES
  79 #endif
  80
  81 typedef struct {
  82         /* Proportion of data that is entropy */
  83         double rate;
  84         /* Counter goes positive if this command times out */
  85         unsigned int badness;
  86         /* Increases by factor of two each timeout */
  87         unsigned int sticky_badness;
  88         /* Path to executable */
  89         char *path;
  90         /* argv to pass to executable */
  91         char *args[NUM_ARGS]; /* XXX: arbitrary limit */
  92         /* full command string (debug) */
  93         char *cmdstring;
  94 } entropy_cmd_t;
  95
  96 /* slow command timeouts (all in milliseconds) */
  97 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
  98 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
  99
 100 /* this is initialised from a file, by prng_read_commands() */
 101 static entropy_cmd_t *entropy_cmds = NULL;
 102
 103 /* Prototypes */
 104 double stir_from_system(void);
 105 double stir_from_programs(void);
 106 double stir_gettimeofday(double entropy_estimate);
 107 double stir_clock(double entropy_estimate);
 108 double stir_rusage(int who, double entropy_estimate);
 109 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
 110 int get_random_bytes_prngd(unsigned char *buf, int len,
 111     unsigned short tcp_port, char *socket_path);
 112
 113 /*
 114  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
 115  * listening either on 'tcp_port', or via Unix domain socket at *
 116  * 'socket_path'.
 117  * Either a non-zero tcp_port or a non-null socket_path must be
 118  * supplied.
 119  * Returns 0 on success, -1 on error
 120  */
 121 int
 122 get_random_bytes_prngd(unsigned char *buf, int len,
 123     unsigned short tcp_port, char *socket_path)
 124 {
 125         int fd, addr_len, rval, errors;
 126         char msg[2];
 127         struct sockaddr_storage addr;
 128         struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
 129         struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
 130         mysig_t old_sigpipe;
 131
 132         /* Sanity checks */
 133         if (socket_path == NULL && tcp_port == 0)
 134                 fatal("You must specify a port or a socket");
 135         if (socket_path != NULL &&
 136             strlen(socket_path) >= sizeof(addr_un->sun_path))
 137                 fatal("Random pool path is too long");
 138         if (len > 255)
 139                 fatal("Too many bytes to read from PRNGD");
 140
 141         memset(&addr, '\0', sizeof(addr));
 142
 143         if (tcp_port != 0) {
 144                 addr_in->sin_family = AF_INET;
 145                 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 146                 addr_in->sin_port = htons(tcp_port);
 147                 addr_len = sizeof(*addr_in);
 148         } else {
 149                 addr_un->sun_family = AF_UNIX;
 150                 strlcpy(addr_un->sun_path, socket_path,
 151                     sizeof(addr_un->sun_path));
 152                 addr_len = offsetof(struct sockaddr_un, sun_path) +
 153                     strlen(socket_path) + 1;
 154         }
 155
 156         old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
 157
 158         errors = 0;
 159         rval = -1;
 160 reopen:
 161         fd = socket(addr.ss_family, SOCK_STREAM, 0);
 162         if (fd == -1) {
 163                 error("Couldn't create socket: %s", strerror(errno));
 164                 goto done;
 165         }
 166
 167         if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
 168                 if (tcp_port != 0) {
 169                         error("Couldn't connect to PRNGD port %d: %s",
 170                             tcp_port, strerror(errno));
 171                 } else {
 172                         error("Couldn't connect to PRNGD socket \"%s\": %s",
 173                             addr_un->sun_path, strerror(errno));
 174                 }
 175                 goto done;
 176         }
 177
 178         /* Send blocking read request to PRNGD */
 179         msg[0] = 0x02;
 180         msg[1] = len;
 181
 182         if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
 183                 if (errno == EPIPE && errors < 10) {
 184                         close(fd);
 185                         errors++;
 186                         goto reopen;
 187                 }
 188                 error("Couldn't write to PRNGD socket: %s",
 189                     strerror(errno));
 190                 goto done;
 191         }
 192
 193         if (atomicio(read, fd, buf, len) != len) {
 194                 if (errno == EPIPE && errors < 10) {
 195                         close(fd);
 196                         errors++;
 197                         goto reopen;
 198                 }
 199                 error("Couldn't read from PRNGD socket: %s",
 200                     strerror(errno));
 201                 goto done;
 202         }
 203
 204         rval = 0;
 205 done:
 206         mysignal(SIGPIPE, old_sigpipe);
 207         if (fd != -1)
 208                 close(fd);
 209         return rval;
 210 }
 211
 212 static int
 213 seed_from_prngd(unsigned char *buf, size_t bytes)
 214 {
 215 #ifdef PRNGD_PORT
 216         debug("trying egd/prngd port %d", PRNGD_PORT);
 217         if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
 218                 return 0;
 219 #endif
 220 #ifdef PRNGD_SOCKET
 221         debug("trying egd/prngd socket %s", PRNGD_SOCKET);
 222         if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
 223                 return 0;
 224 #endif
 225         return -1;
 226 }
 227
 228 double
 229 stir_gettimeofday(double entropy_estimate)
 230 {
 231         struct timeval tv;
 232
 233         if (gettimeofday(&tv, NULL) == -1)
 234                 fatal("Couldn't gettimeofday: %s", strerror(errno));
 235
 236         RAND_add(&tv, sizeof(tv), entropy_estimate);
 237
 238         return entropy_estimate;
 239 }
 240
 241 double
 242 stir_clock(double entropy_estimate)
 243 {
 244 #ifdef HAVE_CLOCK
 245         clock_t c;
 246
 247         c = clock();
 248         RAND_add(&c, sizeof(c), entropy_estimate);
 249
 250         return entropy_estimate;
 251 #else /* _HAVE_CLOCK */
 252         return 0;
 253 #endif /* _HAVE_CLOCK */
 254 }
 255
 256 double
 257 stir_rusage(int who, double entropy_estimate)
 258 {
 259 #ifdef HAVE_GETRUSAGE
 260         struct rusage ru;
 261
 262         if (getrusage(who, &ru) == -1)
 263                 return 0;
 264
 265         RAND_add(&ru, sizeof(ru), entropy_estimate);
 266
 267         return entropy_estimate;
 268 #else /* _HAVE_GETRUSAGE */
 269         return 0;
 270 #endif /* _HAVE_GETRUSAGE */
 271 }
 272
 273 static int
 274 timeval_diff(struct timeval *t1, struct timeval *t2)
 275 {
 276         int secdiff, usecdiff;
 277
 278         secdiff = t2->tv_sec - t1->tv_sec;
 279         usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
 280         return (int)(usecdiff / 1000);
 281 }
 282
 283 double
 284 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
 285 {
 286         char buf[8192];
 287         fd_set rdset;
 288         int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
 289         int status, total_bytes_read;
 290         static int devnull = -1;
 291         pid_t pid;
 292         SHA_CTX sha;
 293         struct timeval tv_start, tv_current;
 294
 295         debug3("Reading output from \'%s\'", src->cmdstring);
 296
 297         if (devnull == -1) {
 298                 devnull = open("/dev/null", O_RDWR);
 299                 if (devnull == -1)
 300                         fatal("Couldn't open /dev/null: %s",
 301                             strerror(errno));
 302         }
 303
 304         if (pipe(p) == -1)
 305                 fatal("Couldn't open pipe: %s", strerror(errno));
 306
 307         (void)gettimeofday(&tv_start, NULL); /* record start time */
 308
 309         switch (pid = fork()) {
 310                 case -1: /* Error */
 311                         close(p[0]);
 312                         close(p[1]);
 313                         fatal("Couldn't fork: %s", strerror(errno));
 314                         /* NOTREACHED */
 315                 case 0: /* Child */
 316                         dup2(devnull, STDIN_FILENO);
 317                         dup2(p[1], STDOUT_FILENO);
 318                         dup2(p[1], STDERR_FILENO);
 319                         close(p[0]);
 320                         close(p[1]);
 321                         close(devnull);
 322
 323                         execv(src->path, (char**)(src->args));
 324
 325                         debug("(child) Couldn't exec '%s': %s",
 326                             src->cmdstring, strerror(errno));
 327                         _exit(-1);
 328                 default: /* Parent */
 329                         break;
 330         }
 331
 332         RAND_add(&pid, sizeof(&pid), 0.0);
 333
 334         close(p[1]);
 335
 336         /* Hash output from child */
 337         SHA1_Init(&sha);
 338
 339         cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
 340         while (!error_abort && !cmd_eof) {
 341                 int ret;
 342                 struct timeval tv;
 343                 int msec_remaining;
 344
 345                 (void) gettimeofday(&tv_current, 0);
 346                 msec_elapsed = timeval_diff(&tv_start, &tv_current);
 347                 if (msec_elapsed >= entropy_timeout_current) {
 348                         error_abort=1;
 349                         continue;
 350                 }
 351                 msec_remaining = entropy_timeout_current - msec_elapsed;
 352
 353                 FD_ZERO(&rdset);
 354                 FD_SET(p[0], &rdset);
 355                 tv.tv_sec = msec_remaining / 1000;
 356                 tv.tv_usec = (msec_remaining % 1000) * 1000;
 357
 358                 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
 359
 360                 RAND_add(&tv, sizeof(tv), 0.0);
 361
 362                 switch (ret) {
 363                 case 0:
 364                         /* timer expired */
 365                         error_abort = 1;
 366                         kill(pid, SIGINT);
 367                         break;
 368                 case 1:
 369                         /* command input */
 370                         do {
 371                                 bytes_read = read(p[0], buf, sizeof(buf));
 372                         } while (bytes_read == -1 && errno == EINTR);
 373                         RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
 374                         if (bytes_read == -1) {
 375                                 error_abort = 1;
 376                                 break;
 377                         } else if (bytes_read) {
 378                                 SHA1_Update(&sha, buf, bytes_read);
 379                                 total_bytes_read += bytes_read;
 380                         } else {
 381                                 cmd_eof = 1;
 382                         }
 383                         break;
 384                 case -1:
 385                 default:
 386                         /* error */
 387                         debug("Command '%s': select() failed: %s",
 388                             src->cmdstring, strerror(errno));
 389                         error_abort = 1;
 390                         break;
 391                 }
 392         }
 393
 394         SHA1_Final(hash, &sha);
 395
 396         close(p[0]);
 397
 398         debug3("Time elapsed: %d msec", msec_elapsed);
 399
 400         if (waitpid(pid, &status, 0) == -1) {
 401                error("Couldn't wait for child '%s' completion: %s",
 402                    src->cmdstring, strerror(errno));
 403                 return 0.0;
 404         }
 405
 406         RAND_add(&status, sizeof(&status), 0.0);
 407
 408         if (error_abort) {
 409                 /*
 410                  * Closing p[0] on timeout causes the entropy command to
 411                  * SIGPIPE. Take whatever output we got, and mark this
 412                  * command as slow
 413                  */
 414                 debug2("Command '%s' timed out", src->cmdstring);
 415                 src->sticky_badness *= 2;
 416                 src->badness = src->sticky_badness;
 417                 return total_bytes_read;
 418         }
 419
 420         if (WIFEXITED(status)) {
 421                 if (WEXITSTATUS(status) == 0) {
 422                         return total_bytes_read;
 423                 } else {
 424                         debug2("Command '%s' exit status was %d",
 425                             src->cmdstring, WEXITSTATUS(status));
 426                         src->badness = src->sticky_badness = 128;
 427                         return 0.0;
 428                 }
 429         } else if (WIFSIGNALED(status)) {
 430                 debug2("Command '%s' returned on uncaught signal %d !",
 431                     src->cmdstring, status);
 432                 src->badness = src->sticky_badness = 128;
 433                 return 0.0;
 434         } else
 435                 return 0.0;
 436 }
 437
 438 double
 439 stir_from_system(void)
 440 {
 441         double total_entropy_estimate;
 442         long int i;
 443
 444         total_entropy_estimate = 0;
 445
 446         i = getpid();
 447         RAND_add(&i, sizeof(i), 0.5);
 448         total_entropy_estimate += 0.1;
 449
 450         i = getppid();
 451         RAND_add(&i, sizeof(i), 0.5);
 452         total_entropy_estimate += 0.1;
 453
 454         i = getuid();
 455         RAND_add(&i, sizeof(i), 0.0);
 456         i = getgid();
 457         RAND_add(&i, sizeof(i), 0.0);
 458
 459         total_entropy_estimate += stir_gettimeofday(1.0);
 460         total_entropy_estimate += stir_clock(0.5);
 461         total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
 462
 463         return total_entropy_estimate;
 464 }
 465
 466 double
 467 stir_from_programs(void)
 468 {
 469         int c;
 470         double entropy, total_entropy;
 471         unsigned char hash[SHA_DIGEST_LENGTH];
 472
 473         total_entropy = 0;
 474         for(c = 0; entropy_cmds[c].path != NULL; c++) {
 475                 if (!entropy_cmds[c].badness) {
 476                         /* Hash output from command */
 477                         entropy = hash_command_output(&entropy_cmds[c],
 478                             hash);
 479
 480                         /* Scale back estimate by command's rate */
 481                         entropy *= entropy_cmds[c].rate;
 482
 483                         /* Upper bound of entropy is SHA_DIGEST_LENGTH */
 484                         if (entropy > SHA_DIGEST_LENGTH)
 485                                 entropy = SHA_DIGEST_LENGTH;
 486
 487                         /* Stir it in */
 488                         RAND_add(hash, sizeof(hash), entropy);
 489
 490                         debug3("Got %0.2f bytes of entropy from '%s'",
 491                             entropy, entropy_cmds[c].cmdstring);
 492
 493                         total_entropy += entropy;
 494
 495                         /* Execution time should be a bit unpredictable */
 496                         total_entropy += stir_gettimeofday(0.05);
 497                         total_entropy += stir_clock(0.05);
 498                         total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
 499                         total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
 500                 } else {
 501                         debug2("Command '%s' disabled (badness %d)",
 502                             entropy_cmds[c].cmdstring,
 503                             entropy_cmds[c].badness);
 504
 505                         if (entropy_cmds[c].badness > 0)
 506                                 entropy_cmds[c].badness--;
 507                 }
 508         }
 509
 510         return total_entropy;
 511 }
 512
 513 /*
 514  * prng seedfile functions
 515  */
 516 int
 517 prng_check_seedfile(char *filename)
 518 {
 519         struct stat st;
 520
 521         /*
 522          * XXX raceable: eg replace seed between this stat and subsequent
 523          * open. Not such a problem because we don't really trust the
 524          * seed file anyway.
 525          * XXX: use secure path checking as elsewhere in OpenSSH
 526          */
 527         if (lstat(filename, &st) == -1) {
 528                 /* Give up on hard errors */
 529                 if (errno != ENOENT)
 530                         debug("WARNING: Couldn't stat random seed file "
 531                             "\"%.100s\": %s", filename, strerror(errno));
 532                 return 0;
 533         }
 534
 535         /* regular file? */
 536         if (!S_ISREG(st.st_mode))
 537                 fatal("PRNG seedfile %.100s is not a regular file",
 538                     filename);
 539
 540         /* mode 0600, owned by root or the current user? */
 541         if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
 542                 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
 543                     "owned by uid %li", filename, (long int)getuid());
 544                 return 0;
 545         }
 546
 547         return 1;
 548 }
 549
 550 void
 551 prng_write_seedfile(void)
 552 {
 553         int fd, save_errno;
 554         unsigned char seed[SEED_FILE_SIZE];
 555         char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
 556         struct passwd *pw;
 557         mode_t old_umask;
 558
 559         pw = getpwuid(getuid());
 560         if (pw == NULL)
 561                 fatal("Couldn't get password entry for current user "
 562                     "(%li): %s", (long int)getuid(), strerror(errno));
 563
 564         /* Try to ensure that the parent directory is there */
 565         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 566             _PATH_SSH_USER_DIR);
 567         mkdir(filename, 0700);
 568
 569         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 570             SSH_PRNG_SEED_FILE);
 571
 572         strlcpy(tmpseed, filename, sizeof(tmpseed));
 573         if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
 574             sizeof(tmpseed))
 575                 fatal("PRNG seed filename too long");
 576
 577         if (RAND_bytes(seed, sizeof(seed)) <= 0)
 578                 fatal("PRNG seed extraction failed");
 579
 580         /* Don't care if the seed doesn't exist */
 581         prng_check_seedfile(filename);
 582
 583         old_umask = umask(0177);
 584
 585         if ((fd = mkstemp(tmpseed)) == -1) {
 586                 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
 587                     "(%.100s)", tmpseed, strerror(errno));
 588         } else {
 589                 debug("writing PRNG seed to file %.100s", tmpseed);
 590                 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 591                         save_errno = errno;
 592                         close(fd);
 593                         unlink(tmpseed);
 594                         fatal("problem writing PRNG seedfile %.100s "
 595                             "(%.100s)", filename, strerror(save_errno));
 596                 }
 597                 close(fd);
 598                 debug("moving temporary PRNG seed to file %.100s", filename);
 599                 if (rename(tmpseed, filename) == -1) {
 600                         save_errno = errno;
 601                         unlink(tmpseed);
 602                         fatal("problem renaming PRNG seedfile from %.100s "
 603                             "to %.100s (%.100s)", tmpseed, filename,
 604                             strerror(save_errno));
 605                 }
 606         }
 607         umask(old_umask);
 608 }
 609
 610 void
 611 prng_read_seedfile(void)
 612 {
 613         int fd;
 614         char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
 615         struct passwd *pw;
 616
 617         pw = getpwuid(getuid());
 618         if (pw == NULL)
 619                 fatal("Couldn't get password entry for current user "
 620                     "(%li): %s", (long int)getuid(), strerror(errno));
 621
 622         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 623                 SSH_PRNG_SEED_FILE);
 624
 625         debug("loading PRNG seed from file %.100s", filename);
 626
 627         if (!prng_check_seedfile(filename)) {
 628                 verbose("Random seed file not found or invalid, ignoring.");
 629                 return;
 630         }
 631
 632         /* open the file and read in the seed */
 633         fd = open(filename, O_RDONLY);
 634         if (fd == -1)
 635                 fatal("could not open PRNG seedfile %.100s (%.100s)",
 636                     filename, strerror(errno));
 637
 638         if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 639                 verbose("invalid or short read from PRNG seedfile "
 640                     "%.100s - ignoring", filename);
 641                 memset(seed, '\0', sizeof(seed));
 642         }
 643         close(fd);
 644
 645         /* stir in the seed, with estimated entropy zero */
 646         RAND_add(&seed, sizeof(seed), 0.0);
 647 }
 648
 649
 650 /*
 651  * entropy command initialisation functions
 652  */
 653 int
 654 prng_read_commands(char *cmdfilename)
 655 {
 656         char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
 657         double est;
 658         entropy_cmd_t *entcmd;
 659         FILE *f;
 660         int cur_cmd, linenum, num_cmds, arg;
 661
 662         if ((f = fopen(cmdfilename, "r")) == NULL) {
 663                 fatal("couldn't read entropy commands file %.100s: %.100s",
 664                     cmdfilename, strerror(errno));
 665         }
 666
 667         num_cmds = 64;
 668         entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t));
 669         memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t));
 670
 671         /* Read in file */
 672         cur_cmd = linenum = 0;
 673         while (fgets(line, sizeof(line), f)) {
 674                 linenum++;
 675
 676                 /* Skip leading whitespace, blank lines and comments */
 677                 cp = line + strspn(line, WHITESPACE);
 678                 if ((*cp == 0) || (*cp == '#'))
 679                         continue; /* done with this line */
 680
 681                 /*
 682                  * The first non-whitespace char should be a double quote
 683                  * delimiting the commandline
 684                  */
 685                 if (*cp != '"') {
 686                         error("bad entropy command, %.100s line %d",
 687                             cmdfilename, linenum);
 688                         continue;
 689                 }
 690
 691                 /*
 692                  * First token, command args (incl. argv[0]) in double
 693                  * quotes
 694                  */
 695                 cp = strtok(cp, "\"");
 696                 if (cp == NULL) {
 697                         error("missing or bad command string, %.100s "
 698                             "line %d -- ignored", cmdfilename, linenum);
 699                         continue;
 700                 }
 701                 strlcpy(cmd, cp, sizeof(cmd));
 702
 703                 /* Second token, full command path */
 704                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 705                         error("missing command path, %.100s "
 706                             "line %d -- ignored", cmdfilename, linenum);
 707                         continue;
 708                 }
 709
 710                 /* Did configure mark this as dead? */
 711                 if (strncmp("undef", cp, 5) == 0)
 712                         continue;
 713
 714                 strlcpy(path, cp, sizeof(path));
 715
 716                 /* Third token, entropy rate estimate for this command */
 717                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 718                         error("missing entropy estimate, %.100s "
 719                             "line %d -- ignored", cmdfilename, linenum);
 720                         continue;
 721                 }
 722                 est = strtod(cp, NULL);
 723
 724                 /* end of line */
 725                 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
 726                         error("garbage at end of line %d in %.100s "
 727                             "-- ignored", linenum, cmdfilename);
 728                         continue;
 729                 }
 730
 731                 /* save the command for debug messages */
 732                 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
 733
 734                 /* split the command args */
 735                 cp = strtok(cmd, WHITESPACE);
 736                 arg = 0;
 737                 do {
 738                         entcmd[cur_cmd].args[arg] = xstrdup(cp);
 739                         arg++;
 740                 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
 741
 742                 if (strtok(NULL, WHITESPACE))
 743                         error("ignored extra commands (max %d), %.100s "
 744                             "line %d", NUM_ARGS, cmdfilename, linenum);
 745
 746                 /* Copy the command path and rate estimate */
 747                 entcmd[cur_cmd].path = xstrdup(path);
 748                 entcmd[cur_cmd].rate = est;
 749
 750                 /* Initialise other values */
 751                 entcmd[cur_cmd].sticky_badness = 1;
 752
 753                 cur_cmd++;
 754
 755                 /*
 756                  * If we've filled the array, reallocate it twice the size
 757                  * Do this now because even if this we're on the last
 758                  * command we need another slot to mark the last entry
 759                  */
 760                 if (cur_cmd == num_cmds) {
 761                         num_cmds *= 2;
 762                         entcmd = xrealloc(entcmd, num_cmds *
 763                             sizeof(entropy_cmd_t));
 764                 }
 765         }
 766
 767         /* zero the last entry */
 768         memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
 769
 770         /* trim to size */
 771         entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) *
 772             sizeof(entropy_cmd_t));
 773
 774         debug("Loaded %d entropy commands from %.100s", cur_cmd,
 775             cmdfilename);
 776
 777         return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
 778 }
 779
 780 void
 781 usage(void)
 782 {
 783         fprintf(stderr, "Usage: %s [options]\n", __progname);
 784         fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
 785         fprintf(stderr, "              Multiple -v increases verbosity.\n");
 786         fprintf(stderr, "  -x          Force output in hexadecimal (for debugging)\n");
 787         fprintf(stderr, "  -X          Force output in binary\n");
 788         fprintf(stderr, "  -b bytes    Number of bytes to output (default %d)\n",
 789             OUTPUT_SEED_SIZE);
 790 }
 791
 792 int
 793 main(int argc, char **argv)
 794 {
 795         unsigned char *buf;
 796         int ret, ch, debug_level, output_hex, bytes;
 797         extern char *optarg;
 798         LogLevel ll;
 799
 800         __progname = ssh_get_progname(argv[0]);
 801         log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
 802
 803         ll = SYSLOG_LEVEL_INFO;
 804         debug_level = output_hex = 0;
 805         bytes = OUTPUT_SEED_SIZE;
 806
 807         /* Don't write binary data to a tty, unless we are forced to */
 808         if (isatty(STDOUT_FILENO))
 809                 output_hex = 1;
 810
 811         while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
 812                 switch (ch) {
 813                 case 'v':
 814                         if (debug_level < 3)
 815                                 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
 816                         break;
 817                 case 'x':
 818                         output_hex = 1;
 819                         break;
 820                 case 'X':
 821                         output_hex = 0;
 822                         break;
 823                 case 'b':
 824                         if ((bytes = atoi(optarg)) <= 0)
 825                                 fatal("Invalid number of output bytes");
 826                         break;
 827                 case 'h':
 828                         usage();
 829                         exit(0);
 830                 default:
 831                         error("Invalid commandline option");
 832                         usage();
 833                 }
 834         }
 835
 836         log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
 837
 838 #ifdef USE_SEED_FILES
 839         prng_read_seedfile();
 840 #endif
 841
 842         buf = xmalloc(bytes);
 843
 844         /*
 845          * Seed the RNG from wherever we can
 846          */
 847
 848         /* Take whatever is on the stack, but don't credit it */
 849         RAND_add(buf, bytes, 0);
 850
 851         debug("Seeded RNG with %i bytes from system calls",
 852             (int)stir_from_system());
 853
 854         /* try prngd, fall back to commands if prngd fails or not configured */
 855         if (seed_from_prngd(buf, bytes) == 0) {
 856                 RAND_add(buf, bytes, bytes);
 857         } else {
 858                 /* Read in collection commands */
 859                 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
 860                         fatal("PRNG initialisation failed -- exiting.");
 861                 debug("Seeded RNG with %i bytes from programs",
 862                     (int)stir_from_programs());
 863         }
 864
 865 #ifdef USE_SEED_FILES
 866         prng_write_seedfile();
 867 #endif
 868
 869         /*
 870          * Write the seed to stdout
 871          */
 872
 873         if (!RAND_status())
 874                 fatal("Not enough entropy in RNG");
 875
 876         if (RAND_bytes(buf, bytes) <= 0)
 877                 fatal("Couldn't extract entropy from PRNG");
 878
 879         if (output_hex) {
 880                 for(ret = 0; ret < bytes; ret++)
 881                         printf("%02x", (unsigned char)(buf[ret]));
 882                 printf("\n");
 883         } else
 884                 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
 885
 886         memset(buf, '\0', bytes);
 887         xfree(buf);
 888
 889         return ret == bytes ? 0 : 1;
 890 }
 891
 892 /*
 893  * We may attempt to re-seed during mkstemp if we are using the one in the
 894  * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
 895  * need our own seed_rng().  We must also check that we have enough entropy.
 896  */
 897 void
 898 seed_rng(void)
 899 {
 900         if (!RAND_status())
 901                 fatal("Not enough entropy in RNG");
 902 }