ssh-rand-helper.c

   1 /*
   2  * Copyright (c) 2001-2002 Damien Miller.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26
  27 #include <sys/types.h>
  28 #include <sys/resource.h>
  29 #include <sys/stat.h>
  30 #include <sys/wait.h>
  31 #include <sys/socket.h>
  32
  33 #include <stdarg.h>
  34 #include <stddef.h>
  35 #include <string.h>
  36
  37 #include <netinet/in.h>
  38 #include <arpa/inet.h>
  39
  40 #ifdef HAVE_SYS_UN_H
  41 # include <sys/un.h>
  42 #endif
  43
  44 #include <errno.h>
  45 #include <fcntl.h>
  46 #include <pwd.h>
  47 #include <signal.h>
  48 #include <time.h>
  49 #include <unistd.h>
  50
  51 #include <openssl/rand.h>
  52 #include <openssl/sha.h>
  53 #include <openssl/crypto.h>
  54
  55 /* SunOS 4.4.4 needs this */
  56 #ifdef HAVE_FLOATINGPOINT_H
  57 # include <floatingpoint.h>
  58 #endif /* HAVE_FLOATINGPOINT_H */
  59
  60 #include "misc.h"
  61 #include "xmalloc.h"
  62 #include "atomicio.h"
  63 #include "pathnames.h"
  64 #include "log.h"
  65
  66 /* Number of bytes we write out */
  67 #define OUTPUT_SEED_SIZE        48
  68
  69 /* Length of on-disk seedfiles */
  70 #define SEED_FILE_SIZE          1024
  71
  72 /* Maximum number of command-line arguments to read from file */
  73 #define NUM_ARGS                10
  74
  75 /* Minimum number of usable commands to be considered sufficient */
  76 #define MIN_ENTROPY_SOURCES     16
  77
  78 /* Path to on-disk seed file (relative to user's home directory */
  79 #ifndef SSH_PRNG_SEED_FILE
  80 # define SSH_PRNG_SEED_FILE      _PATH_SSH_USER_DIR"/prng_seed"
  81 #endif
  82
  83 /* Path to PRNG commands list */
  84 #ifndef SSH_PRNG_COMMAND_FILE
  85 # define SSH_PRNG_COMMAND_FILE   SSHDIR "/ssh_prng_cmds"
  86 #endif
  87
  88 extern char *__progname;
  89
  90 #define WHITESPACE " \t\n"
  91
  92 #ifndef RUSAGE_SELF
  93 # define RUSAGE_SELF 0
  94 #endif
  95 #ifndef RUSAGE_CHILDREN
  96 # define RUSAGE_CHILDREN 0
  97 #endif
  98
  99 #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
 100 # define USE_SEED_FILES
 101 #endif
 102
 103 typedef struct {
 104         /* Proportion of data that is entropy */
 105         double rate;
 106         /* Counter goes positive if this command times out */
 107         unsigned int badness;
 108         /* Increases by factor of two each timeout */
 109         unsigned int sticky_badness;
 110         /* Path to executable */
 111         char *path;
 112         /* argv to pass to executable */
 113         char *args[NUM_ARGS]; /* XXX: arbitrary limit */
 114         /* full command string (debug) */
 115         char *cmdstring;
 116 } entropy_cmd_t;
 117
 118 /* slow command timeouts (all in milliseconds) */
 119 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
 120 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
 121
 122 /* this is initialised from a file, by prng_read_commands() */
 123 static entropy_cmd_t *entropy_cmds = NULL;
 124
 125 /* Prototypes */
 126 double stir_from_system(void);
 127 double stir_from_programs(void);
 128 double stir_gettimeofday(double entropy_estimate);
 129 double stir_clock(double entropy_estimate);
 130 double stir_rusage(int who, double entropy_estimate);
 131 double hash_command_output(entropy_cmd_t *src, unsigned char *hash);
 132 int get_random_bytes_prngd(unsigned char *buf, int len,
 133     unsigned short tcp_port, char *socket_path);
 134
 135 /*
 136  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
 137  * listening either on 'tcp_port', or via Unix domain socket at *
 138  * 'socket_path'.
 139  * Either a non-zero tcp_port or a non-null socket_path must be
 140  * supplied.
 141  * Returns 0 on success, -1 on error
 142  */
 143 int
 144 get_random_bytes_prngd(unsigned char *buf, int len,
 145     unsigned short tcp_port, char *socket_path)
 146 {
 147         int fd, addr_len, rval, errors;
 148         u_char msg[2];
 149         struct sockaddr_storage addr;
 150         struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
 151         struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
 152         mysig_t old_sigpipe;
 153
 154         /* Sanity checks */
 155         if (socket_path == NULL && tcp_port == 0)
 156                 fatal("You must specify a port or a socket");
 157         if (socket_path != NULL &&
 158             strlen(socket_path) >= sizeof(addr_un->sun_path))
 159                 fatal("Random pool path is too long");
 160         if (len <= 0 || len > 255)
 161                 fatal("Too many bytes (%d) to read from PRNGD", len);
 162
 163         memset(&addr, '\0', sizeof(addr));
 164
 165         if (tcp_port != 0) {
 166                 addr_in->sin_family = AF_INET;
 167                 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 168                 addr_in->sin_port = htons(tcp_port);
 169                 addr_len = sizeof(*addr_in);
 170         } else {
 171                 addr_un->sun_family = AF_UNIX;
 172                 strlcpy(addr_un->sun_path, socket_path,
 173                     sizeof(addr_un->sun_path));
 174                 addr_len = offsetof(struct sockaddr_un, sun_path) +
 175                     strlen(socket_path) + 1;
 176         }
 177
 178         old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
 179
 180         errors = 0;
 181         rval = -1;
 182 reopen:
 183         fd = socket(addr.ss_family, SOCK_STREAM, 0);
 184         if (fd == -1) {
 185                 error("Couldn't create socket: %s", strerror(errno));
 186                 goto done;
 187         }
 188
 189         if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
 190                 if (tcp_port != 0) {
 191                         error("Couldn't connect to PRNGD port %d: %s",
 192                             tcp_port, strerror(errno));
 193                 } else {
 194                         error("Couldn't connect to PRNGD socket \"%s\": %s",
 195                             addr_un->sun_path, strerror(errno));
 196                 }
 197                 goto done;
 198         }
 199
 200         /* Send blocking read request to PRNGD */
 201         msg[0] = 0x02;
 202         msg[1] = len;
 203
 204         if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
 205                 if (errno == EPIPE && errors < 10) {
 206                         close(fd);
 207                         errors++;
 208                         goto reopen;
 209                 }
 210                 error("Couldn't write to PRNGD socket: %s",
 211                     strerror(errno));
 212                 goto done;
 213         }
 214
 215         if (atomicio(read, fd, buf, len) != (size_t)len) {
 216                 if (errno == EPIPE && errors < 10) {
 217                         close(fd);
 218                         errors++;
 219                         goto reopen;
 220                 }
 221                 error("Couldn't read from PRNGD socket: %s",
 222                     strerror(errno));
 223                 goto done;
 224         }
 225
 226         rval = 0;
 227 done:
 228         mysignal(SIGPIPE, old_sigpipe);
 229         if (fd != -1)
 230                 close(fd);
 231         return rval;
 232 }
 233
 234 static int
 235 seed_from_prngd(unsigned char *buf, size_t bytes)
 236 {
 237 #ifdef PRNGD_PORT
 238         debug("trying egd/prngd port %d", PRNGD_PORT);
 239         if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
 240                 return 0;
 241 #endif
 242 #ifdef PRNGD_SOCKET
 243         debug("trying egd/prngd socket %s", PRNGD_SOCKET);
 244         if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
 245                 return 0;
 246 #endif
 247         return -1;
 248 }
 249
 250 double
 251 stir_gettimeofday(double entropy_estimate)
 252 {
 253         struct timeval tv;
 254
 255         if (gettimeofday(&tv, NULL) == -1)
 256                 fatal("Couldn't gettimeofday: %s", strerror(errno));
 257
 258         RAND_add(&tv, sizeof(tv), entropy_estimate);
 259
 260         return entropy_estimate;
 261 }
 262
 263 double
 264 stir_clock(double entropy_estimate)
 265 {
 266 #ifdef HAVE_CLOCK
 267         clock_t c;
 268
 269         c = clock();
 270         RAND_add(&c, sizeof(c), entropy_estimate);
 271
 272         return entropy_estimate;
 273 #else /* _HAVE_CLOCK */
 274         return 0;
 275 #endif /* _HAVE_CLOCK */
 276 }
 277
 278 double
 279 stir_rusage(int who, double entropy_estimate)
 280 {
 281 #ifdef HAVE_GETRUSAGE
 282         struct rusage ru;
 283
 284         if (getrusage(who, &ru) == -1)
 285                 return 0;
 286
 287         RAND_add(&ru, sizeof(ru), entropy_estimate);
 288
 289         return entropy_estimate;
 290 #else /* _HAVE_GETRUSAGE */
 291         return 0;
 292 #endif /* _HAVE_GETRUSAGE */
 293 }
 294
 295 static int
 296 timeval_diff(struct timeval *t1, struct timeval *t2)
 297 {
 298         int secdiff, usecdiff;
 299
 300         secdiff = t2->tv_sec - t1->tv_sec;
 301         usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
 302         return (int)(usecdiff / 1000);
 303 }
 304
 305 double
 306 hash_command_output(entropy_cmd_t *src, unsigned char *hash)
 307 {
 308         char buf[8192];
 309         fd_set rdset;
 310         int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
 311         int status, total_bytes_read;
 312         static int devnull = -1;
 313         pid_t pid;
 314         SHA_CTX sha;
 315         struct timeval tv_start, tv_current;
 316
 317         debug3("Reading output from \'%s\'", src->cmdstring);
 318
 319         if (devnull == -1) {
 320                 devnull = open("/dev/null", O_RDWR);
 321                 if (devnull == -1)
 322                         fatal("Couldn't open /dev/null: %s",
 323                             strerror(errno));
 324         }
 325
 326         if (pipe(p) == -1)
 327                 fatal("Couldn't open pipe: %s", strerror(errno));
 328
 329         (void)gettimeofday(&tv_start, NULL); /* record start time */
 330
 331         switch (pid = fork()) {
 332                 case -1: /* Error */
 333                         close(p[0]);
 334                         close(p[1]);
 335                         fatal("Couldn't fork: %s", strerror(errno));
 336                         /* NOTREACHED */
 337                 case 0: /* Child */
 338                         dup2(devnull, STDIN_FILENO);
 339                         dup2(p[1], STDOUT_FILENO);
 340                         dup2(p[1], STDERR_FILENO);
 341                         close(p[0]);
 342                         close(p[1]);
 343                         close(devnull);
 344
 345                         execv(src->path, (char**)(src->args));
 346
 347                         debug("(child) Couldn't exec '%s': %s",
 348                             src->cmdstring, strerror(errno));
 349                         _exit(-1);
 350                 default: /* Parent */
 351                         break;
 352         }
 353
 354         RAND_add(&pid, sizeof(&pid), 0.0);
 355
 356         close(p[1]);
 357
 358         /* Hash output from child */
 359         SHA1_Init(&sha);
 360
 361         cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
 362         while (!error_abort && !cmd_eof) {
 363                 int ret;
 364                 struct timeval tv;
 365                 int msec_remaining;
 366
 367                 (void) gettimeofday(&tv_current, 0);
 368                 msec_elapsed = timeval_diff(&tv_start, &tv_current);
 369                 if (msec_elapsed >= entropy_timeout_current) {
 370                         error_abort=1;
 371                         continue;
 372                 }
 373                 msec_remaining = entropy_timeout_current - msec_elapsed;
 374
 375                 FD_ZERO(&rdset);
 376                 FD_SET(p[0], &rdset);
 377                 tv.tv_sec = msec_remaining / 1000;
 378                 tv.tv_usec = (msec_remaining % 1000) * 1000;
 379
 380                 ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);
 381
 382                 RAND_add(&tv, sizeof(tv), 0.0);
 383
 384                 switch (ret) {
 385                 case 0:
 386                         /* timer expired */
 387                         error_abort = 1;
 388                         kill(pid, SIGINT);
 389                         break;
 390                 case 1:
 391                         /* command input */
 392                         do {
 393                                 bytes_read = read(p[0], buf, sizeof(buf));
 394                         } while (bytes_read == -1 && errno == EINTR);
 395                         RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
 396                         if (bytes_read == -1) {
 397                                 error_abort = 1;
 398                                 break;
 399                         } else if (bytes_read) {
 400                                 SHA1_Update(&sha, buf, bytes_read);
 401                                 total_bytes_read += bytes_read;
 402                         } else {
 403                                 cmd_eof = 1;
 404                         }
 405                         break;
 406                 case -1:
 407                 default:
 408                         /* error */
 409                         debug("Command '%s': select() failed: %s",
 410                             src->cmdstring, strerror(errno));
 411                         error_abort = 1;
 412                         break;
 413                 }
 414         }
 415
 416         SHA1_Final(hash, &sha);
 417
 418         close(p[0]);
 419
 420         debug3("Time elapsed: %d msec", msec_elapsed);
 421
 422         if (waitpid(pid, &status, 0) == -1) {
 423                 error("Couldn't wait for child '%s' completion: %s",
 424                     src->cmdstring, strerror(errno));
 425                 return 0.0;
 426         }
 427
 428         RAND_add(&status, sizeof(&status), 0.0);
 429
 430         if (error_abort) {
 431                 /*
 432                  * Closing p[0] on timeout causes the entropy command to
 433                  * SIGPIPE. Take whatever output we got, and mark this
 434                  * command as slow
 435                  */
 436                 debug2("Command '%s' timed out", src->cmdstring);
 437                 src->sticky_badness *= 2;
 438                 src->badness = src->sticky_badness;
 439                 return total_bytes_read;
 440         }
 441
 442         if (WIFEXITED(status)) {
 443                 if (WEXITSTATUS(status) == 0) {
 444                         return total_bytes_read;
 445                 } else {
 446                         debug2("Command '%s' exit status was %d",
 447                             src->cmdstring, WEXITSTATUS(status));
 448                         src->badness = src->sticky_badness = 128;
 449                         return 0.0;
 450                 }
 451         } else if (WIFSIGNALED(status)) {
 452                 debug2("Command '%s' returned on uncaught signal %d !",
 453                     src->cmdstring, status);
 454                 src->badness = src->sticky_badness = 128;
 455                 return 0.0;
 456         } else
 457                 return 0.0;
 458 }
 459
 460 double
 461 stir_from_system(void)
 462 {
 463         double total_entropy_estimate;
 464         long int i;
 465
 466         total_entropy_estimate = 0;
 467
 468         i = getpid();
 469         RAND_add(&i, sizeof(i), 0.5);
 470         total_entropy_estimate += 0.1;
 471
 472         i = getppid();
 473         RAND_add(&i, sizeof(i), 0.5);
 474         total_entropy_estimate += 0.1;
 475
 476         i = getuid();
 477         RAND_add(&i, sizeof(i), 0.0);
 478         i = getgid();
 479         RAND_add(&i, sizeof(i), 0.0);
 480
 481         total_entropy_estimate += stir_gettimeofday(1.0);
 482         total_entropy_estimate += stir_clock(0.5);
 483         total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
 484
 485         return total_entropy_estimate;
 486 }
 487
 488 double
 489 stir_from_programs(void)
 490 {
 491         int c;
 492         double entropy, total_entropy;
 493         unsigned char hash[SHA_DIGEST_LENGTH];
 494
 495         total_entropy = 0;
 496         for(c = 0; entropy_cmds[c].path != NULL; c++) {
 497                 if (!entropy_cmds[c].badness) {
 498                         /* Hash output from command */
 499                         entropy = hash_command_output(&entropy_cmds[c],
 500                             hash);
 501
 502                         /* Scale back estimate by command's rate */
 503                         entropy *= entropy_cmds[c].rate;
 504
 505                         /* Upper bound of entropy is SHA_DIGEST_LENGTH */
 506                         if (entropy > SHA_DIGEST_LENGTH)
 507                                 entropy = SHA_DIGEST_LENGTH;
 508
 509                         /* Stir it in */
 510                         RAND_add(hash, sizeof(hash), entropy);
 511
 512                         debug3("Got %0.2f bytes of entropy from '%s'",
 513                             entropy, entropy_cmds[c].cmdstring);
 514
 515                         total_entropy += entropy;
 516
 517                         /* Execution time should be a bit unpredictable */
 518                         total_entropy += stir_gettimeofday(0.05);
 519                         total_entropy += stir_clock(0.05);
 520                         total_entropy += stir_rusage(RUSAGE_SELF, 0.1);
 521                         total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1);
 522                 } else {
 523                         debug2("Command '%s' disabled (badness %d)",
 524                             entropy_cmds[c].cmdstring,
 525                             entropy_cmds[c].badness);
 526
 527                         if (entropy_cmds[c].badness > 0)
 528                                 entropy_cmds[c].badness--;
 529                 }
 530         }
 531
 532         return total_entropy;
 533 }
 534
 535 /*
 536  * prng seedfile functions
 537  */
 538 int
 539 prng_check_seedfile(char *filename)
 540 {
 541         struct stat st;
 542
 543         /*
 544          * XXX raceable: eg replace seed between this stat and subsequent
 545          * open. Not such a problem because we don't really trust the
 546          * seed file anyway.
 547          * XXX: use secure path checking as elsewhere in OpenSSH
 548          */
 549         if (lstat(filename, &st) == -1) {
 550                 /* Give up on hard errors */
 551                 if (errno != ENOENT)
 552                         debug("WARNING: Couldn't stat random seed file "
 553                             "\"%.100s\": %s", filename, strerror(errno));
 554                 return 0;
 555         }
 556
 557         /* regular file? */
 558         if (!S_ISREG(st.st_mode))
 559                 fatal("PRNG seedfile %.100s is not a regular file",
 560                     filename);
 561
 562         /* mode 0600, owned by root or the current user? */
 563         if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) {
 564                 debug("WARNING: PRNG seedfile %.100s must be mode 0600, "
 565                     "owned by uid %li", filename, (long int)getuid());
 566                 return 0;
 567         }
 568
 569         return 1;
 570 }
 571
 572 void
 573 prng_write_seedfile(void)
 574 {
 575         int fd, save_errno;
 576         unsigned char seed[SEED_FILE_SIZE];
 577         char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
 578         struct passwd *pw;
 579         mode_t old_umask;
 580
 581         pw = getpwuid(getuid());
 582         if (pw == NULL)
 583                 fatal("Couldn't get password entry for current user "
 584                     "(%li): %s", (long int)getuid(), strerror(errno));
 585
 586         /* Try to ensure that the parent directory is there */
 587         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 588             _PATH_SSH_USER_DIR);
 589         if (mkdir(filename, 0700) < 0 && errno != EEXIST)
 590                 fatal("mkdir %.200s: %s", filename, strerror(errno));
 591
 592         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 593             SSH_PRNG_SEED_FILE);
 594
 595         strlcpy(tmpseed, filename, sizeof(tmpseed));
 596         if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
 597             sizeof(tmpseed))
 598                 fatal("PRNG seed filename too long");
 599
 600         if (RAND_bytes(seed, sizeof(seed)) <= 0)
 601                 fatal("PRNG seed extraction failed");
 602
 603         /* Don't care if the seed doesn't exist */
 604         prng_check_seedfile(filename);
 605
 606         old_umask = umask(0177);
 607
 608         if ((fd = mkstemp(tmpseed)) == -1) {
 609                 debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
 610                     "(%.100s)", tmpseed, strerror(errno));
 611         } else {
 612                 debug("writing PRNG seed to file %.100s", tmpseed);
 613                 if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 614                         save_errno = errno;
 615                         close(fd);
 616                         unlink(tmpseed);
 617                         fatal("problem writing PRNG seedfile %.100s "
 618                             "(%.100s)", filename, strerror(save_errno));
 619                 }
 620                 close(fd);
 621                 debug("moving temporary PRNG seed to file %.100s", filename);
 622                 if (rename(tmpseed, filename) == -1) {
 623                         save_errno = errno;
 624                         unlink(tmpseed);
 625                         fatal("problem renaming PRNG seedfile from %.100s "
 626                             "to %.100s (%.100s)", tmpseed, filename,
 627                             strerror(save_errno));
 628                 }
 629         }
 630         umask(old_umask);
 631 }
 632
 633 void
 634 prng_read_seedfile(void)
 635 {
 636         int fd;
 637         char seed[SEED_FILE_SIZE], filename[MAXPATHLEN];
 638         struct passwd *pw;
 639
 640         pw = getpwuid(getuid());
 641         if (pw == NULL)
 642                 fatal("Couldn't get password entry for current user "
 643                     "(%li): %s", (long int)getuid(), strerror(errno));
 644
 645         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 646                 SSH_PRNG_SEED_FILE);
 647
 648         debug("loading PRNG seed from file %.100s", filename);
 649
 650         if (!prng_check_seedfile(filename)) {
 651                 verbose("Random seed file not found or invalid, ignoring.");
 652                 return;
 653         }
 654
 655         /* open the file and read in the seed */
 656         fd = open(filename, O_RDONLY);
 657         if (fd == -1)
 658                 fatal("could not open PRNG seedfile %.100s (%.100s)",
 659                     filename, strerror(errno));
 660
 661         if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) {
 662                 verbose("invalid or short read from PRNG seedfile "
 663                     "%.100s - ignoring", filename);
 664                 memset(seed, '\0', sizeof(seed));
 665         }
 666         close(fd);
 667
 668         /* stir in the seed, with estimated entropy zero */
 669         RAND_add(&seed, sizeof(seed), 0.0);
 670 }
 671
 672
 673 /*
 674  * entropy command initialisation functions
 675  */
 676 int
 677 prng_read_commands(char *cmdfilename)
 678 {
 679         char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE];
 680         double est;
 681         entropy_cmd_t *entcmd;
 682         FILE *f;
 683         int cur_cmd, linenum, num_cmds, arg;
 684
 685         if ((f = fopen(cmdfilename, "r")) == NULL) {
 686                 fatal("couldn't read entropy commands file %.100s: %.100s",
 687                     cmdfilename, strerror(errno));
 688         }
 689
 690         num_cmds = 64;
 691         entcmd = xcalloc(num_cmds, sizeof(entropy_cmd_t));
 692
 693         /* Read in file */
 694         cur_cmd = linenum = 0;
 695         while (fgets(line, sizeof(line), f)) {
 696                 linenum++;
 697
 698                 /* Skip leading whitespace, blank lines and comments */
 699                 cp = line + strspn(line, WHITESPACE);
 700                 if ((*cp == 0) || (*cp == '#'))
 701                         continue; /* done with this line */
 702
 703                 /*
 704                  * The first non-whitespace char should be a double quote
 705                  * delimiting the commandline
 706                  */
 707                 if (*cp != '"') {
 708                         error("bad entropy command, %.100s line %d",
 709                             cmdfilename, linenum);
 710                         continue;
 711                 }
 712
 713                 /*
 714                  * First token, command args (incl. argv[0]) in double
 715                  * quotes
 716                  */
 717                 cp = strtok(cp, "\"");
 718                 if (cp == NULL) {
 719                         error("missing or bad command string, %.100s "
 720                             "line %d -- ignored", cmdfilename, linenum);
 721                         continue;
 722                 }
 723                 strlcpy(cmd, cp, sizeof(cmd));
 724
 725                 /* Second token, full command path */
 726                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 727                         error("missing command path, %.100s "
 728                             "line %d -- ignored", cmdfilename, linenum);
 729                         continue;
 730                 }
 731
 732                 /* Did configure mark this as dead? */
 733                 if (strncmp("undef", cp, 5) == 0)
 734                         continue;
 735
 736                 strlcpy(path, cp, sizeof(path));
 737
 738                 /* Third token, entropy rate estimate for this command */
 739                 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
 740                         error("missing entropy estimate, %.100s "
 741                             "line %d -- ignored", cmdfilename, linenum);
 742                         continue;
 743                 }
 744                 est = strtod(cp, NULL);
 745
 746                 /* end of line */
 747                 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
 748                         error("garbage at end of line %d in %.100s "
 749                             "-- ignored", linenum, cmdfilename);
 750                         continue;
 751                 }
 752
 753                 /* save the command for debug messages */
 754                 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
 755
 756                 /* split the command args */
 757                 cp = strtok(cmd, WHITESPACE);
 758                 arg = 0;
 759                 do {
 760                         entcmd[cur_cmd].args[arg] = xstrdup(cp);
 761                         arg++;
 762                 } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE)));
 763
 764                 if (strtok(NULL, WHITESPACE))
 765                         error("ignored extra commands (max %d), %.100s "
 766                             "line %d", NUM_ARGS, cmdfilename, linenum);
 767
 768                 /* Copy the command path and rate estimate */
 769                 entcmd[cur_cmd].path = xstrdup(path);
 770                 entcmd[cur_cmd].rate = est;
 771
 772                 /* Initialise other values */
 773                 entcmd[cur_cmd].sticky_badness = 1;
 774
 775                 cur_cmd++;
 776
 777                 /*
 778                  * If we've filled the array, reallocate it twice the size
 779                  * Do this now because even if this we're on the last
 780                  * command we need another slot to mark the last entry
 781                  */
 782                 if (cur_cmd == num_cmds) {
 783                         num_cmds *= 2;
 784                         entcmd = xrealloc(entcmd, num_cmds,
 785                             sizeof(entropy_cmd_t));
 786                 }
 787         }
 788
 789         /* zero the last entry */
 790         memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t));
 791
 792         /* trim to size */
 793         entropy_cmds = xrealloc(entcmd, (cur_cmd + 1),
 794             sizeof(entropy_cmd_t));
 795
 796         debug("Loaded %d entropy commands from %.100s", cur_cmd,
 797             cmdfilename);
 798
 799         fclose(f);
 800         return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0;
 801 }
 802
 803 void
 804 usage(void)
 805 {
 806         fprintf(stderr, "Usage: %s [options]\n", __progname);
 807         fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
 808         fprintf(stderr, "              Multiple -v increases verbosity.\n");
 809         fprintf(stderr, "  -x          Force output in hexadecimal (for debugging)\n");
 810         fprintf(stderr, "  -X          Force output in binary\n");
 811         fprintf(stderr, "  -b bytes    Number of bytes to output (default %d)\n",
 812             OUTPUT_SEED_SIZE);
 813 }
 814
 815 int
 816 main(int argc, char **argv)
 817 {
 818         unsigned char *buf;
 819         int ret, ch, debug_level, output_hex, bytes;
 820         extern char *optarg;
 821         extern int optind;
 822         LogLevel ll;
 823
 824         __progname = ssh_get_progname(argv[0]);
 825         log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
 826
 827         ll = SYSLOG_LEVEL_INFO;
 828         debug_level = output_hex = 0;
 829         bytes = OUTPUT_SEED_SIZE;
 830
 831         /* Don't write binary data to a tty, unless we are forced to */
 832         if (isatty(STDOUT_FILENO))
 833                 output_hex = 1;
 834
 835         while ((ch = getopt(argc, argv, "vxXhb:")) != -1) {
 836                 switch (ch) {
 837                 case 'v':
 838                         if (debug_level < 3)
 839                                 ll = SYSLOG_LEVEL_DEBUG1 + debug_level++;
 840                         break;
 841                 case 'x':
 842                         output_hex = 1;
 843                         break;
 844                 case 'X':
 845                         output_hex = 0;
 846                         break;
 847                 case 'b':
 848                         if ((bytes = atoi(optarg)) <= 0)
 849                                 fatal("Invalid number of output bytes");
 850                         break;
 851                 case 'h':
 852                         usage();
 853                         exit(0);
 854                 default:
 855                         error("Invalid commandline option");
 856                         usage();
 857                         exit(1);
 858                 }
 859         }
 860         log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1);
 861
 862         if (argc != optind) {
 863                 error("Unexpected commandline arguments.");
 864                 usage();
 865                 exit(1);
 866         }
 867
 868 #ifdef USE_SEED_FILES
 869         prng_read_seedfile();
 870 #endif
 871
 872         buf = xmalloc(bytes);
 873
 874         /*
 875          * Seed the RNG from wherever we can
 876          */
 877
 878         /* Take whatever is on the stack, but don't credit it */
 879         RAND_add(buf, bytes, 0);
 880
 881         debug("Seeded RNG with %i bytes from system calls",
 882             (int)stir_from_system());
 883
 884         /* try prngd, fall back to commands if prngd fails or not configured */
 885         if (seed_from_prngd(buf, bytes) == 0) {
 886                 RAND_add(buf, bytes, bytes);
 887         } else {
 888                 /* Read in collection commands */
 889                 if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
 890                         fatal("PRNG initialisation failed -- exiting.");
 891                 debug("Seeded RNG with %i bytes from programs",
 892                     (int)stir_from_programs());
 893         }
 894
 895 #ifdef USE_SEED_FILES
 896         prng_write_seedfile();
 897 #endif
 898
 899         /*
 900          * Write the seed to stdout
 901          */
 902
 903         if (!RAND_status())
 904                 fatal("Not enough entropy in RNG");
 905
 906         if (RAND_bytes(buf, bytes) <= 0)
 907                 fatal("Couldn't extract entropy from PRNG");
 908
 909         if (output_hex) {
 910                 for(ret = 0; ret < bytes; ret++)
 911                         printf("%02x", (unsigned char)(buf[ret]));
 912                 printf("\n");
 913         } else
 914                 ret = atomicio(vwrite, STDOUT_FILENO, buf, bytes);
 915
 916         memset(buf, '\0', bytes);
 917         xfree(buf);
 918
 919         return ret == bytes ? 0 : 1;
 920 }
 921
 922 /*
 923  * We may attempt to re-seed during mkstemp if we are using the one in the
 924  * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
 925  * need our own seed_rng().  We must also check that we have enough entropy.
 926  */
 927 void
 928 seed_rng(void)
 929 {
 930         if (!RAND_status())
 931                 fatal("Not enough entropy in RNG");
 932 }