| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Acquisition of environmental noise (Unix-specific) |
| 4 | * |
| 5 | * (c) 1998 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include "config.h" |
| 31 | |
| 32 | #include <errno.h> |
| 33 | #include <setjmp.h> |
| 34 | #include <signal.h> |
| 35 | #include <stdio.h> |
| 36 | #include <stdlib.h> |
| 37 | #include <string.h> |
| 38 | |
| 39 | #include <sys/types.h> |
| 40 | #include <sys/time.h> |
| 41 | #include <sys/wait.h> |
| 42 | |
| 43 | #include <fcntl.h> |
| 44 | #include <unistd.h> |
| 45 | |
| 46 | #ifdef HAVE_SETGROUPS |
| 47 | # include <grp.h> |
| 48 | #endif |
| 49 | |
| 50 | #if defined(HAVE_LINUX_RANDOM_H) |
| 51 | # include <linux/random.h> |
| 52 | # include <sys/syscall.h> |
| 53 | #endif |
| 54 | |
| 55 | #include <mLib/bits.h> |
| 56 | #include <mLib/mdup.h> |
| 57 | #include <mLib/sel.h> |
| 58 | #include <mLib/tv.h> |
| 59 | |
| 60 | #include "noise.h" |
| 61 | #include "paranoia.h" |
| 62 | #include "rand.h" |
| 63 | |
| 64 | /*----- Magical numbers ---------------------------------------------------*/ |
| 65 | |
| 66 | #define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */ |
| 67 | |
| 68 | # define TIMESTRUCT timeval |
| 69 | # define tv_SEC tv_sec |
| 70 | # define tv_FRAC tv_usec |
| 71 | # define TIMERES 1000000 |
| 72 | # define GETTIME(tv) (gettimeofday((tv), 0)) |
| 73 | # define TOTIMEVAL(tv, xx) (*(tv) = *(xx)) |
| 74 | |
| 75 | /*----- Noise source definition -------------------------------------------*/ |
| 76 | |
| 77 | const rand_source noise_source = { noise_acquire, noise_timer }; |
| 78 | |
| 79 | /*----- Static variables --------------------------------------------------*/ |
| 80 | |
| 81 | /* --- Timer differences --- */ |
| 82 | |
| 83 | static unsigned long noise_last; /* Last time recorded */ |
| 84 | static unsigned long noise_diff; /* Last first order difference */ |
| 85 | |
| 86 | /* --- Setuid program handling --- */ |
| 87 | |
| 88 | static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */ |
| 89 | static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */ |
| 90 | |
| 91 | /*----- Main code ---------------------------------------------------------*/ |
| 92 | |
| 93 | /* --- @bitcount@ --- * |
| 94 | * |
| 95 | * Arguments: @unsigned long x@ = a word containing bits |
| 96 | * |
| 97 | * Returns: The number of bits set in the word. |
| 98 | */ |
| 99 | |
| 100 | static int bitcount(unsigned long x) |
| 101 | { |
| 102 | static const char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3, |
| 103 | 1, 2, 2, 3, 2, 3, 3, 4 }; |
| 104 | int count = 0; |
| 105 | while (x) { |
| 106 | count += ctab[x & 0xfu]; |
| 107 | x >>= 4; |
| 108 | } |
| 109 | return (count); |
| 110 | } |
| 111 | |
| 112 | /* --- @timer@ --- * |
| 113 | * |
| 114 | * Arguments: @rand_pool *r@ = pointer to randomness pool |
| 115 | * @const struct TIMESTRUCT *tv@ = pointer to time block |
| 116 | * |
| 117 | * Returns: Nonzero if some randomness was contributed. |
| 118 | * |
| 119 | * Use: Low-level timer contributor. |
| 120 | */ |
| 121 | |
| 122 | static int timer(rand_pool *r, const struct TIMESTRUCT *tv) |
| 123 | { |
| 124 | unsigned long x, d, dd; |
| 125 | int de, dde; |
| 126 | int ret; |
| 127 | |
| 128 | x = tv->tv_FRAC + TIMERES*tv->tv_SEC; |
| 129 | d = x ^ noise_last; |
| 130 | dd = d ^ noise_diff; |
| 131 | noise_last = x; |
| 132 | noise_diff = d; |
| 133 | de = bitcount(d); |
| 134 | dde = bitcount(dd); |
| 135 | rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde); |
| 136 | ret = (de || dde); |
| 137 | BURN(tv); x = d = dd = de = dde = 0; |
| 138 | return (ret); |
| 139 | } |
| 140 | |
| 141 | /* --- @noise_timer@ --- * |
| 142 | * |
| 143 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 144 | * |
| 145 | * Returns: Nonzero if some randomness was contributed. |
| 146 | * |
| 147 | * Use: Contributes the current time to the randomness pool. |
| 148 | * A guess at the number of useful bits contributed is made, |
| 149 | * based on first and second order bit differences. This isn't |
| 150 | * ever-so reliable, but it's better than nothing. |
| 151 | */ |
| 152 | |
| 153 | int noise_timer(rand_pool *r) |
| 154 | { |
| 155 | struct TIMESTRUCT tv; |
| 156 | GETTIME(&tv); return (timer(r, &tv)); |
| 157 | } |
| 158 | |
| 159 | /* --- @noise_devrandom@ --- * |
| 160 | * |
| 161 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 162 | * |
| 163 | * Returns: Nonzero if some randomness was contributed. |
| 164 | * |
| 165 | * Use: Attempts to obtain some randomness from the system entropy |
| 166 | * pool. All bits from the device are assumed to be good. |
| 167 | */ |
| 168 | |
| 169 | int noise_devrandom(rand_pool *r) |
| 170 | { |
| 171 | int fd = -1; |
| 172 | octet buf[RAND_POOLSZ]; |
| 173 | ssize_t len; |
| 174 | size_t n = 0; |
| 175 | int ret = 0; |
| 176 | #ifdef __linux__ |
| 177 | fd_set infd; |
| 178 | struct timeval tv = { 0, 0 }; |
| 179 | #endif |
| 180 | #ifdef HAVE_GETENTROPY |
| 181 | size_t nn; |
| 182 | #endif |
| 183 | |
| 184 | #if defined(HAVE_LINUX_RANDOM_H) && \ |
| 185 | defined(GRND_NONBLOCK) && \ |
| 186 | defined(SYS_getrandom) |
| 187 | /* --- Use the new shinies if available --- */ |
| 188 | |
| 189 | while (n < sizeof(buf)) { |
| 190 | if ((len = syscall(SYS_getrandom, buf + n, sizeof(buf) - n, |
| 191 | GRND_NONBLOCK)) <= 0) { |
| 192 | if (errno == ENOSYS) break; |
| 193 | else goto done; |
| 194 | } |
| 195 | n += len; |
| 196 | } |
| 197 | if (n == sizeof(buf)) goto win; |
| 198 | #endif |
| 199 | |
| 200 | #ifdef HAVE_GETENTROPY |
| 201 | /* --- OpenBSD-flavoured shinies --- */ |
| 202 | |
| 203 | while (n < sizeof(buf)) { |
| 204 | nn = sizeof(buf) - nn; |
| 205 | if (nn > 256) nn = 256; |
| 206 | if (getentropy(buf + n, nn)) break; |
| 207 | n += nn; |
| 208 | } |
| 209 | if (n == sizeof(buf)) goto win; |
| 210 | #endif |
| 211 | |
| 212 | #ifdef __linux__ |
| 213 | /* --- Don't take from `/dev/urandom' if `/dev/random' would block --- */ |
| 214 | |
| 215 | if ((fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) < 0) goto done; |
| 216 | FD_ZERO(&infd); |
| 217 | FD_SET(fd, &infd); |
| 218 | if (select(fd + 1, &infd, 0, 0, &tv) < 0 || !FD_ISSET(fd, &infd)) |
| 219 | goto done; |
| 220 | close(fd); fd = -1; |
| 221 | #endif |
| 222 | |
| 223 | /* --- Be nice to other clients of the random device --- * |
| 224 | * |
| 225 | * Attempt to open the device nonblockingly. If that works, take up to |
| 226 | * one bufferful and then close again. If there's no data to be read, |
| 227 | * then that's tough and we go away again, on the grounds that the device |
| 228 | * needs to get some more entropy from somewhere. |
| 229 | */ |
| 230 | |
| 231 | if (fd >= 0 || |
| 232 | (fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
| 233 | (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 || |
| 234 | (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) { |
| 235 | while (n < sizeof(buf)) { |
| 236 | if ((len = read(fd, buf + n, sizeof(buf) - n)) <= 0) break; |
| 237 | n += len; |
| 238 | } |
| 239 | if (n == sizeof(buf)) goto win; |
| 240 | } |
| 241 | goto done; |
| 242 | |
| 243 | win: |
| 244 | ret = 1; |
| 245 | done: |
| 246 | if (fd >= 0) close(fd); |
| 247 | rand_add(r, buf, n, 8*n); |
| 248 | BURN(buf); |
| 249 | noise_timer(r); |
| 250 | return (ret); |
| 251 | } |
| 252 | |
| 253 | /* --- @noise_setid@ --- * |
| 254 | * |
| 255 | * Arguments: @uid_t uid@ = uid to set |
| 256 | * @gid_t gid@ = gid to set |
| 257 | * |
| 258 | * Returns: --- |
| 259 | * |
| 260 | * Use: Sets the user and group ids to be used by @noise_filter@ |
| 261 | * when running child processes. This is useful to avoid |
| 262 | * giving shell commands (even carefully written ones) undue |
| 263 | * privileges. This interface is Unix-specific |
| 264 | */ |
| 265 | |
| 266 | void noise_setid(uid_t uid, gid_t gid) |
| 267 | { |
| 268 | noise_uid = uid; |
| 269 | noise_gid = gid; |
| 270 | } |
| 271 | |
| 272 | /* --- @noise_filter@ --- * |
| 273 | * |
| 274 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 275 | * @int good@ = number of good bits per 1024 bits |
| 276 | * @const char *c@ = shell command to run |
| 277 | * |
| 278 | * Returns: Nonzero if some randomness was contributed. |
| 279 | * |
| 280 | * Use: Attempts to execute a shell command, and dump it into the |
| 281 | * randomness pool. A very rough estimate of the number of |
| 282 | * good bits is made, based on the size of the command's output. |
| 283 | * This function calls @waitpid@, so be careful. Before execing |
| 284 | * the command, the process uid and gid are set to the values |
| 285 | * given to @noise_setid@, and an attempt is made to reset the |
| 286 | * list of supplementary groups. The environment passed to |
| 287 | * the command has been severly lobotimized. If the command |
| 288 | * fails to complete within a short time period, it is killed. |
| 289 | * Paranoid use of close-on-exec flags for file descriptors is |
| 290 | * recommended. |
| 291 | * |
| 292 | * This interface is Unix-specific. |
| 293 | */ |
| 294 | |
| 295 | struct noisekid { |
| 296 | rand_pool *r; |
| 297 | int good; |
| 298 | char buf[4096]; |
| 299 | int donep; |
| 300 | int ret; |
| 301 | }; |
| 302 | |
| 303 | static void kid_read(int fd, unsigned mode, void *p) |
| 304 | { |
| 305 | struct noisekid *nk = p; |
| 306 | ssize_t sz; |
| 307 | int goodbits; |
| 308 | |
| 309 | noise_timer(nk->r); |
| 310 | if ((sz = read(fd, nk->buf, sizeof(nk->buf))) <= 0) |
| 311 | nk->donep = 1; |
| 312 | else { |
| 313 | goodbits = (sz * nk->good) / 128; |
| 314 | rand_add(nk->r, nk->buf, sz, goodbits); |
| 315 | nk->ret = 1; |
| 316 | } |
| 317 | } |
| 318 | |
| 319 | static void kid_dead(struct timeval *tv, void *p) |
| 320 | { struct noisekid *nk = p; nk->donep = 1; } |
| 321 | |
| 322 | int noise_filter(rand_pool *r, int good, const char *c) |
| 323 | { |
| 324 | pid_t kid; |
| 325 | int fd[2]; |
| 326 | struct timeval dead; |
| 327 | struct TIMESTRUCT now; |
| 328 | int ret = 0; |
| 329 | struct noisekid nk = { 0 }; |
| 330 | sel_state sel; |
| 331 | sel_file sf; |
| 332 | sel_timer st; |
| 333 | const char *env[] = { |
| 334 | "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc", |
| 335 | 0 |
| 336 | }; |
| 337 | |
| 338 | /* --- Remember when this business started --- */ |
| 339 | |
| 340 | GETTIME(&now); timer(r, &now); |
| 341 | TOTIMEVAL(&dead, &now); |
| 342 | |
| 343 | /* --- Create a pipe --- */ |
| 344 | |
| 345 | if (pipe(fd)) |
| 346 | return (ret); |
| 347 | |
| 348 | /* --- Fork a child off --- */ |
| 349 | |
| 350 | fflush(0); |
| 351 | kid = fork(); |
| 352 | if (kid < 0) { |
| 353 | close(fd[0]); |
| 354 | close(fd[1]); |
| 355 | return (ret); |
| 356 | } |
| 357 | |
| 358 | /* --- Handle the child end of the deal --- */ |
| 359 | |
| 360 | if (kid == 0) { |
| 361 | mdup_fd mfd[3]; |
| 362 | int f, i = 0; |
| 363 | |
| 364 | /* --- Set the pipe as standard output, close standard input --- */ |
| 365 | |
| 366 | if ((f = open("/dev/null", O_RDONLY)) < 0) _exit(127); |
| 367 | mfd[i].cur = f; mfd[i].want = 0; i++; |
| 368 | mfd[i].cur = fd[1]; mfd[i].want = 1; i++; |
| 369 | mfd[i].cur = f; mfd[i].want = 2; i++; |
| 370 | if (mdup(mfd, i)) _exit(127); |
| 371 | |
| 372 | /* --- Play games with uids --- */ |
| 373 | |
| 374 | if (noise_gid != NOISE_NOSETGID) { |
| 375 | setgid(noise_gid); |
| 376 | setegid(noise_gid); |
| 377 | #ifdef HAVE_SETGROUPS |
| 378 | setgroups(1, &noise_gid); |
| 379 | #endif |
| 380 | } |
| 381 | |
| 382 | if (noise_uid != NOISE_NOSETUID) { |
| 383 | setuid(noise_uid); |
| 384 | seteuid(noise_uid); |
| 385 | } |
| 386 | |
| 387 | /* --- Start the process up --- */ |
| 388 | |
| 389 | execle("/bin/sh", "sh", "-c", c, (char *)0, env); |
| 390 | _exit(127); |
| 391 | } |
| 392 | |
| 393 | /* --- Sort out my end of the deal --- */ |
| 394 | |
| 395 | close(fd[1]); |
| 396 | sel_init(&sel); |
| 397 | nk.r = r; nk.good = good; |
| 398 | TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE); |
| 399 | sel_initfile(&sel, &sf, fd[0], SEL_READ, kid_read, &nk); |
| 400 | sel_addfile(&sf); |
| 401 | sel_addtimer(&sel, &st, &dead, kid_dead, &nk); |
| 402 | while (!nk.donep && !sel_select(&sel)); |
| 403 | |
| 404 | /* --- We've finished with it: kill the child process --- * |
| 405 | * |
| 406 | * This is morally questionable. On the other hand, I don't want to be |
| 407 | * held up in the @waitpid@ call if I can possibly help it. Maybe a |
| 408 | * double-fork is worth doing here. |
| 409 | */ |
| 410 | |
| 411 | close(fd[0]); |
| 412 | BURN(nk.buf); |
| 413 | noise_timer(r); |
| 414 | kill(kid, SIGKILL); |
| 415 | waitpid(kid, 0, 0); |
| 416 | return (nk.ret); |
| 417 | } |
| 418 | |
| 419 | /* --- @noise_freewheel@ --- * |
| 420 | * |
| 421 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 422 | * |
| 423 | * Returns: Nonzero if some randomness was contributed. |
| 424 | * |
| 425 | * Use: Runs a free counter for a short while as a desparate attempt |
| 426 | * to get randomness from somewhere. This is actually quite |
| 427 | * effective. |
| 428 | */ |
| 429 | |
| 430 | #ifdef USE_FREEWHEEL |
| 431 | |
| 432 | static sigjmp_buf fwjmp; |
| 433 | |
| 434 | static void fwalarm(int sig) |
| 435 | { |
| 436 | siglongjmp(fwjmp, 1); |
| 437 | } |
| 438 | |
| 439 | int noise_freewheel(rand_pool *r) |
| 440 | { |
| 441 | void (*sigal)(int) = 0; |
| 442 | struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } }; |
| 443 | int rc = 0; |
| 444 | volatile uint32 fwcount = 0; |
| 445 | |
| 446 | if (!sigsetjmp(fwjmp, 1)) { |
| 447 | if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR) |
| 448 | return (0); |
| 449 | if (setitimer(ITIMER_REAL, &itv, &oitv)) |
| 450 | goto done; |
| 451 | for (;;) |
| 452 | fwcount++; |
| 453 | } else { |
| 454 | octet buf[4]; |
| 455 | STORE32(buf, fwcount); |
| 456 | rand_add(r, buf, sizeof(buf), 16); |
| 457 | rc = 1; |
| 458 | } |
| 459 | |
| 460 | done: |
| 461 | signal(SIGALRM, sigal); |
| 462 | if (oitv.it_value.tv_sec || oitv.it_value.tv_usec) |
| 463 | TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value); |
| 464 | setitimer(ITIMER_REAL, &oitv, 0); |
| 465 | return (rc); |
| 466 | } |
| 467 | |
| 468 | #else |
| 469 | |
| 470 | int noise_freewheel(rand_pool *r) |
| 471 | { |
| 472 | return (0); |
| 473 | } |
| 474 | |
| 475 | #endif |
| 476 | |
| 477 | /* --- @noise_enquire@ --- * |
| 478 | * |
| 479 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 480 | * |
| 481 | * Returns: Nonzero if some randomness was contributed. |
| 482 | * |
| 483 | * Use: Runs some shell commands to enquire about the prevailing |
| 484 | * environment. This can gather quite a lot of low-quality |
| 485 | * entropy. |
| 486 | */ |
| 487 | |
| 488 | int noise_enquire(rand_pool *r) |
| 489 | { |
| 490 | struct tab { |
| 491 | const char *cmd; |
| 492 | unsigned rate; |
| 493 | } tab[] = { |
| 494 | { "ps alxww || ps -elf", 16 }, |
| 495 | { "netstat -n", 6 }, |
| 496 | { "ifconfig -a", 8 }, |
| 497 | { "df", 20 }, |
| 498 | { "w", 6 }, |
| 499 | { "ls -align /tmp/.", 10 }, |
| 500 | { 0, 0 } |
| 501 | }; |
| 502 | int i; |
| 503 | |
| 504 | for (i = 0; tab[i].cmd; i++) |
| 505 | noise_filter(r, tab[i].rate, tab[i].cmd); |
| 506 | return (1); |
| 507 | } |
| 508 | |
| 509 | /* --- @noise_acquire@ --- * |
| 510 | * |
| 511 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 512 | * |
| 513 | * Returns: --- |
| 514 | * |
| 515 | * Use: Acquires some randomness from somewhere. |
| 516 | */ |
| 517 | |
| 518 | void noise_acquire(rand_pool *r) |
| 519 | { |
| 520 | unsigned i; |
| 521 | for (i = 0; i < 8; i++) |
| 522 | noise_freewheel(r); |
| 523 | if (!noise_devrandom(r) || getenv("CATACOMB_FORCE_ESOTERIC_SOURCES")) { |
| 524 | noise_enquire(r); |
| 525 | for (i = 0; i < 8; i++) |
| 526 | noise_freewheel(r); |
| 527 | } |
| 528 | } |
| 529 | |
| 530 | /*----- That's all, folks -------------------------------------------------*/ |