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