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