| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: check.c,v 1.13 2004/04/08 01:36:20 mdw Exp $ |
| 4 | * |
| 5 | * Check validity of requests |
| 6 | * |
| 7 | * (c) 1998 EBI |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of `become' |
| 13 | * |
| 14 | * `Become' is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * `Become' is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with `become'; if not, write to the Free Software Foundation, |
| 26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | /*----- Header files ------------------------------------------------------*/ |
| 30 | |
| 31 | /* --- ANSI headers --- */ |
| 32 | |
| 33 | #include <ctype.h> |
| 34 | #include <errno.h> |
| 35 | #include <stdio.h> |
| 36 | #include <stdlib.h> |
| 37 | #include <string.h> |
| 38 | #include <time.h> |
| 39 | |
| 40 | /* --- Unix headers --- */ |
| 41 | |
| 42 | #include <sys/time.h> |
| 43 | #include <sys/types.h> |
| 44 | #include <sys/socket.h> |
| 45 | |
| 46 | #include <netinet/in.h> |
| 47 | |
| 48 | #include <arpa/inet.h> |
| 49 | |
| 50 | #include <fcntl.h> |
| 51 | #include <netdb.h> |
| 52 | #include <unistd.h> |
| 53 | |
| 54 | /* --- mLib headers --- */ |
| 55 | |
| 56 | #include <mLib/alloc.h> |
| 57 | #include <mLib/quis.h> |
| 58 | #include <mLib/report.h> |
| 59 | #include <mLib/sym.h> |
| 60 | #include <mLib/trace.h> |
| 61 | |
| 62 | /* --- Catacomb headers --- */ |
| 63 | |
| 64 | #include <catacomb/buf.h> |
| 65 | #include <catacomb/dsa.h> |
| 66 | #include <catacomb/key.h> |
| 67 | #include <catacomb/mp.h> |
| 68 | #include <catacomb/noise.h> |
| 69 | #include <catacomb/rand.h> |
| 70 | #include <catacomb/sha.h> |
| 71 | |
| 72 | /* --- Local headers --- */ |
| 73 | |
| 74 | #include "become.h" |
| 75 | #include "config.h" |
| 76 | #include "lexer.h" |
| 77 | #include "name.h" |
| 78 | #include "netg.h" |
| 79 | #include "rule.h" |
| 80 | #include "parse.h" |
| 81 | #include "userdb.h" |
| 82 | |
| 83 | /*----- Client-end network support ----------------------------------------*/ |
| 84 | |
| 85 | #ifndef NONETWORK |
| 86 | |
| 87 | /* --- @check__send@ --- * |
| 88 | * |
| 89 | * Arguments: @char *buf@ = pointer to encrypted request |
| 90 | * @size_t sz@ = size of request |
| 91 | * @int fd@ = socket to send from |
| 92 | * @struct sockaddr_in *serv@ = pointer to table of servers |
| 93 | * @size_t n_serv@ = number of servers |
| 94 | * |
| 95 | * Returns: --- |
| 96 | * |
| 97 | * Use: Sends the request packet to the list of servers. If the |
| 98 | * message couldn't be sent to any of them, an error is |
| 99 | * reported. |
| 100 | */ |
| 101 | |
| 102 | static void check__send(char *buf, size_t sz, int fd, |
| 103 | struct sockaddr_in *serv, size_t n_serv) |
| 104 | { |
| 105 | size_t i; |
| 106 | int ok = 0; |
| 107 | int err = 0; |
| 108 | |
| 109 | for (i = 0; i < n_serv; i++) { |
| 110 | if (sendto(fd, buf, sz, 0, |
| 111 | (struct sockaddr *)(serv + i), sizeof(serv[i])) < 0) { |
| 112 | T( trace(TRACE_CLIENT, "client: send to %s failed: %s", |
| 113 | inet_ntoa(serv[i].sin_addr), strerror(errno)); ) |
| 114 | err = errno; |
| 115 | } else |
| 116 | ok = 1; |
| 117 | } |
| 118 | |
| 119 | if (!ok) |
| 120 | die(1, "couldn't send request to server: %s", strerror(err)); |
| 121 | } |
| 122 | |
| 123 | /* --- @check__ask@ --- * |
| 124 | * |
| 125 | * Arguments: @request *rq@ = pointer to request buffer |
| 126 | * @struct sockaddr_in *serv@ = pointer to table of servers |
| 127 | * @size_t n_serv@ = number of servers |
| 128 | * |
| 129 | * Returns: Nonzero if OK, zero if forbidden |
| 130 | * |
| 131 | * Use: Contacts a number of servers to decide whether the request |
| 132 | * is OK. |
| 133 | */ |
| 134 | |
| 135 | static int check__ask(request *rq, struct sockaddr_in *serv, size_t n_serv) |
| 136 | { |
| 137 | static int tbl[] = { 0, 5, 10, 20, -1 }; |
| 138 | |
| 139 | char buff[2048], rbuff[2048]; |
| 140 | size_t rqlen; |
| 141 | octet hmsg[SHA_HASHSZ]; |
| 142 | octet h[SHA_HASHSZ]; |
| 143 | key_packstruct kps[DSA_PUBFETCHSZ]; |
| 144 | key_packdef *kp; |
| 145 | dsa_pub kpub; |
| 146 | buf b; |
| 147 | sha_ctx hc; |
| 148 | int fd; |
| 149 | struct sockaddr_in sin; |
| 150 | socklen_t slen; |
| 151 | ssize_t sz; |
| 152 | int ans; |
| 153 | fd_set fds; |
| 154 | struct timeval start, now, tv; |
| 155 | mp *m, *r, *s; |
| 156 | key_file f; |
| 157 | key *k; |
| 158 | key_iter ki; |
| 159 | int ind; |
| 160 | size_t i; |
| 161 | |
| 162 | /* --- Open the public keyring --- */ |
| 163 | |
| 164 | if ((key_open(&f, file_PUBKEY, KOPEN_READ, key_moan, 0)) != 0) |
| 165 | die(1, "couldn't open public keyring"); |
| 166 | kp = key_fetchinit(dsa_pubfetch, kps, &kpub); |
| 167 | |
| 168 | /* --- Build the request packet --- */ |
| 169 | |
| 170 | rand_noisesrc(RAND_GLOBAL, &noise_source); |
| 171 | rand_seed(RAND_GLOBAL, 160); |
| 172 | buf_init(&b, buff, sizeof(buff)); |
| 173 | rand_get(RAND_GLOBAL, buf_get(&b, SHA_HASHSZ), SHA_HASHSZ); |
| 174 | buf_putu32(&b, rq->from); |
| 175 | buf_putu32(&b, rq->to); |
| 176 | buf_putu16(&b, strlen(rq->cmd)); |
| 177 | buf_put(&b, rq->cmd, strlen(rq->cmd)); |
| 178 | rqlen = BLEN(&b); |
| 179 | sha_init(&hc); |
| 180 | sha_hash(&hc, buff, rqlen); |
| 181 | sha_done(&hc, hmsg); |
| 182 | |
| 183 | /* --- Create my socket --- */ |
| 184 | |
| 185 | if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0) |
| 186 | die(1, "couldn't create socket: %s", strerror(errno)); |
| 187 | if (fcntl(fd, F_SETFD, 1) < 0) |
| 188 | die(1, "couldn't set close-on-exec flag for socket: %s", strerror(errno)); |
| 189 | |
| 190 | /* --- Bind myself to some address --- */ |
| 191 | |
| 192 | sin.sin_family = AF_INET; |
| 193 | sin.sin_port = 0; |
| 194 | sin.sin_addr.s_addr = htonl(INADDR_ANY); |
| 195 | |
| 196 | if (bind(fd, (struct sockaddr *)&sin, sizeof(sin)) < 0) |
| 197 | die(1, "couldn't bind socket to address: %s", strerror(errno)); |
| 198 | |
| 199 | /* --- Find out when we are --- */ |
| 200 | |
| 201 | gettimeofday(&start, 0); |
| 202 | ind = 0; |
| 203 | |
| 204 | /* --- Now loop until everything's done --- */ |
| 205 | |
| 206 | for (;;) { |
| 207 | gettimeofday(&now, 0); |
| 208 | |
| 209 | /* --- If the current timer has expired, find one that hasn't --- * |
| 210 | * |
| 211 | * Also resend the request after I've found a timer which is still |
| 212 | * extant. If there aren't any, report an error. |
| 213 | */ |
| 214 | |
| 215 | if (now.tv_sec >= start.tv_sec + tbl[ind] && |
| 216 | now.tv_usec >= start.tv_usec) { |
| 217 | do { |
| 218 | ind++; |
| 219 | if (tbl[ind] < 0) |
| 220 | die(1, "no reply from servers"); |
| 221 | } while (now.tv_sec >= start.tv_sec + tbl[ind] && |
| 222 | now.tv_usec >= start.tv_usec); |
| 223 | check__send(buff, rqlen, fd, serv, n_serv); |
| 224 | T( trace(TRACE_CLIENT, "client: send request to servers"); ) |
| 225 | } |
| 226 | |
| 227 | /* --- Now wait for a packet to arrive --- */ |
| 228 | |
| 229 | if (now.tv_usec > start.tv_usec) { |
| 230 | now.tv_usec -= 1000000; |
| 231 | now.tv_sec += 1; |
| 232 | } |
| 233 | tv.tv_sec = start.tv_sec + tbl[ind] - now.tv_sec; |
| 234 | tv.tv_usec = start.tv_usec - now.tv_usec; |
| 235 | |
| 236 | /* --- Sort out file descriptors to watch --- */ |
| 237 | |
| 238 | FD_ZERO(&fds); |
| 239 | FD_SET(fd, &fds); |
| 240 | |
| 241 | /* --- Wait for them --- */ |
| 242 | |
| 243 | i = select(FD_SETSIZE, &fds, 0, 0, &tv); |
| 244 | if (i == 0 || (i < 0 && errno == EINTR)) |
| 245 | continue; |
| 246 | if (i < 0) |
| 247 | die(1, "error waiting for reply: %s", strerror(errno)); |
| 248 | |
| 249 | /* --- Read the reply data --- */ |
| 250 | |
| 251 | slen = sizeof(sin); |
| 252 | if ((sz = recvfrom(fd, (char *)rbuff, sizeof(rbuff), 0, |
| 253 | (struct sockaddr *)&sin, &slen)) < 0) |
| 254 | die(1, "error reading server's reply: %s", strerror(errno)); |
| 255 | |
| 256 | IF_TRACING(TRACE_CLIENT, { |
| 257 | struct hostent *h = gethostbyaddr((char *)&sin.sin_addr, |
| 258 | sizeof(sin.sin_addr), AF_INET); |
| 259 | trace(TRACE_CLIENT, "client: reply received from %s port %i", |
| 260 | h ? h->h_name : inet_ntoa(sin.sin_addr), |
| 261 | ntohs(sin.sin_port)); |
| 262 | }) |
| 263 | |
| 264 | /* --- Verify the sender --- * |
| 265 | * |
| 266 | * This is more to avoid confusion than for security: an active |
| 267 | * attacker is quite capable of forging the source address. We rely |
| 268 | * on the signature in the reply packet for authentication. |
| 269 | */ |
| 270 | |
| 271 | for (i = 0; i < n_serv; i++) { |
| 272 | if (sin.sin_addr.s_addr == serv[i].sin_addr.s_addr && |
| 273 | sin.sin_port == serv[i].sin_port) |
| 274 | break; |
| 275 | } |
| 276 | if (i >= n_serv) { |
| 277 | T( trace(TRACE_CLIENT, "client: reply from unknown host"); ) |
| 278 | continue; |
| 279 | } |
| 280 | |
| 281 | /* --- Unpack and verify the response --- */ |
| 282 | |
| 283 | buf_init(&b, rbuff, sz); |
| 284 | if (buf_ensure(&b, sizeof(hmsg))) goto bad; |
| 285 | if (memcmp(BCUR(&b), hmsg, sizeof(hmsg)) != 0) goto bad; |
| 286 | BSTEP(&b, sizeof(hmsg)); |
| 287 | if ((ans = buf_getbyte(&b)) < 0) goto bad; |
| 288 | |
| 289 | sha_init(&hc); |
| 290 | sha_hash(&hc, BBASE(&b), BLEN(&b)); |
| 291 | sha_done(&hc, h); |
| 292 | if ((r = buf_getmp(&b)) == 0 || (s = buf_getmp(&b)) == 0) goto bad; |
| 293 | m = mp_loadb(MP_NEW, h, sizeof(h)); |
| 294 | |
| 295 | key_mkiter(&ki, &f); |
| 296 | while ((k = key_next(&ki)) != 0) { |
| 297 | if (key_expired(k)) continue; |
| 298 | if (strcmp(k->type, "become-dsa") != 0) continue; |
| 299 | if (key_fetch(kp, k)) continue; |
| 300 | i = dsa_vrfy(&kpub.dp, kpub.y, m, r, s); |
| 301 | dsa_pubfree(&kpub); |
| 302 | if (i) { |
| 303 | key_fetchdone(kp); |
| 304 | key_close(&f); |
| 305 | close(fd); |
| 306 | mp_drop(m); |
| 307 | mp_drop(r); |
| 308 | mp_drop(s); |
| 309 | return (ans); |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | bad: |
| 314 | T( trace(TRACE_CLIENT, |
| 315 | "client: invalid or corrupt reply packet"); ) |
| 316 | } |
| 317 | |
| 318 | die(1, "internal error: can't get here in check__ask"); |
| 319 | return (0); |
| 320 | } |
| 321 | |
| 322 | /* --- @check__client@ --- * |
| 323 | * |
| 324 | * Arguments: @request *rq@ = pointer to a request block |
| 325 | * @FILE *fp@ = file containing server configuration |
| 326 | * |
| 327 | * Returns: Nonzero if OK, zero if forbidden |
| 328 | * |
| 329 | * Use: Asks one or several servers whether a request is acceptable. |
| 330 | */ |
| 331 | |
| 332 | int check__client(request *rq, FILE *fp) |
| 333 | { |
| 334 | /* --- Format of the file --- * |
| 335 | * |
| 336 | * The `servers' file contains entries of the form |
| 337 | * |
| 338 | * %%\syntax{<host> [`:' <port>]}%% |
| 339 | * |
| 340 | * separates by whitespace. I build them all into an array of socket |
| 341 | * addresses and pass the whole lot to another function. |
| 342 | */ |
| 343 | |
| 344 | struct sockaddr_in *serv; /* Array of servers */ |
| 345 | size_t n_serv, max_serv; /* Number and maximum number */ |
| 346 | |
| 347 | /* --- Initialise the server array --- */ |
| 348 | |
| 349 | T( trace(TRACE_CLIENT, "client: reading server definitions"); ) |
| 350 | n_serv = 0; max_serv = 4; /* Four seems reasonable */ |
| 351 | serv = xmalloc(sizeof(*serv) * max_serv); |
| 352 | |
| 353 | /* --- Start reading the file --- */ |
| 354 | |
| 355 | { |
| 356 | char buff[256], *p, *l; /* A buffer and pointers for it */ |
| 357 | int port; /* Default port for servers */ |
| 358 | int state; /* Current parser state */ |
| 359 | struct in_addr t_host; /* Temp place for an address*/ |
| 360 | int t_port; /* Temp place for a port */ |
| 361 | int ch; /* The current character */ |
| 362 | |
| 363 | /* --- Parser states --- */ |
| 364 | |
| 365 | enum { |
| 366 | st_start, /* Waiting to begin */ |
| 367 | st_host, /* Reading a new hostname */ |
| 368 | st_colon, /* Expecting a colon, maybe */ |
| 369 | st_preport, /* Waiting before reading port */ |
| 370 | st_port, /* Reading a port number */ |
| 371 | st_commit, /* Commit a newly read server */ |
| 372 | st_done /* Finished reading the file */ |
| 373 | }; |
| 374 | |
| 375 | /* --- Find a default port --- */ |
| 376 | |
| 377 | { |
| 378 | struct servent *s = getservbyname(quis(), "udp"); |
| 379 | port = (s ? s->s_port : htons(SERVER_PORT)); |
| 380 | } |
| 381 | |
| 382 | /* --- Initialise for scanning the file --- */ |
| 383 | |
| 384 | state = st_host; |
| 385 | p = buff; |
| 386 | l = buff + sizeof(buff); |
| 387 | t_port = port; |
| 388 | ch = getc(fp); |
| 389 | |
| 390 | /* --- Go for it --- */ |
| 391 | |
| 392 | while (state != st_done) { |
| 393 | switch (state) { |
| 394 | |
| 395 | /* --- Initial whitespace before hostname --- */ |
| 396 | |
| 397 | case st_start: |
| 398 | if (ch == EOF) |
| 399 | state = st_done; |
| 400 | else if (isspace((unsigned char)ch)) |
| 401 | ch = getc(fp); |
| 402 | else |
| 403 | state = st_host; |
| 404 | break; |
| 405 | |
| 406 | /* --- Read a host name --- */ |
| 407 | |
| 408 | case st_host: |
| 409 | if (p == l) |
| 410 | die(1, "string too long in `" file_SERVER "'"); |
| 411 | if (ch != EOF && !isspace((unsigned char)ch) && ch != ':') { |
| 412 | *p++ = ch; |
| 413 | ch = getc(fp); |
| 414 | } else { |
| 415 | struct hostent *h; |
| 416 | |
| 417 | *p++ = 0; |
| 418 | if ((h = gethostbyname(buff)) == 0) |
| 419 | die(1, "unknown host `%s' in `" file_SERVER "'", buff); |
| 420 | memcpy(&t_host, h->h_addr, sizeof(t_host)); |
| 421 | state = st_colon; |
| 422 | } |
| 423 | break; |
| 424 | |
| 425 | /* --- Waiting for a colon coming up --- */ |
| 426 | |
| 427 | case st_colon: |
| 428 | if (ch == EOF) |
| 429 | state = st_commit; |
| 430 | else if (isspace((unsigned char)ch)) |
| 431 | ch = getc(fp); |
| 432 | else if (ch == ':') { |
| 433 | state = st_preport; |
| 434 | ch = getc(fp); |
| 435 | } |
| 436 | else |
| 437 | state = st_commit; |
| 438 | break; |
| 439 | |
| 440 | /* --- Clearing whitespace before a port number --- */ |
| 441 | |
| 442 | case st_preport: |
| 443 | if (ch == EOF) |
| 444 | state = st_commit; |
| 445 | else if (isspace((unsigned char)ch)) |
| 446 | ch = getc(fp); |
| 447 | else { |
| 448 | state = st_port; |
| 449 | p = buff; |
| 450 | } |
| 451 | break; |
| 452 | |
| 453 | /* --- Read a port number --- */ |
| 454 | |
| 455 | case st_port: |
| 456 | if (p == l) |
| 457 | die(1, "string too long in `" file_SERVER "'"); |
| 458 | if (ch != EOF && !isspace((unsigned char)ch) && ch != ':') { |
| 459 | *p++ = ch; |
| 460 | ch = getc(fp); |
| 461 | } else { |
| 462 | struct servent *s; |
| 463 | |
| 464 | *p++ = 0; |
| 465 | s = getservbyname(buff, "udp"); |
| 466 | if (!s && isdigit((unsigned char)buff[0])) |
| 467 | t_port = htons(atoi(buff)); |
| 468 | else if (!s) |
| 469 | die(1, "unknown service `%s' in `" file_SERVER "'", buff); |
| 470 | else |
| 471 | t_port = s->s_port; |
| 472 | state = st_commit; |
| 473 | } |
| 474 | break; |
| 475 | |
| 476 | /* --- A server has been read successfully --- */ |
| 477 | |
| 478 | case st_commit: |
| 479 | if (n_serv == max_serv) { |
| 480 | max_serv *= 2; |
| 481 | serv = xrealloc(serv, n_serv * sizeof(*serv), |
| 482 | max_serv * sizeof(*serv)); |
| 483 | } |
| 484 | serv[n_serv].sin_family = AF_INET; |
| 485 | serv[n_serv].sin_addr = t_host; |
| 486 | serv[n_serv].sin_port = t_port; |
| 487 | n_serv++; |
| 488 | state = st_start; |
| 489 | p = buff; |
| 490 | t_port = port; |
| 491 | break; |
| 492 | |
| 493 | /* --- A safety net for a broken parser --- */ |
| 494 | |
| 495 | default: |
| 496 | die(1, "internal error: can't get here in check__client"); |
| 497 | break; |
| 498 | } |
| 499 | } |
| 500 | } |
| 501 | |
| 502 | fclose(fp); |
| 503 | |
| 504 | /* --- Now start sending requests --- */ |
| 505 | |
| 506 | if (!n_serv) |
| 507 | die(1, "no servers specified in `" file_SERVER "'"); |
| 508 | |
| 509 | IF_TRACING(TRACE_CLIENT, { |
| 510 | size_t i; |
| 511 | |
| 512 | for (i = 0; i < n_serv; i++) { |
| 513 | trace(TRACE_CLIENT, "client: server %s port %i", |
| 514 | inet_ntoa(serv[i].sin_addr), ntohs(serv[i].sin_port)); |
| 515 | } |
| 516 | }) |
| 517 | return (check__ask(rq, serv, n_serv)); |
| 518 | } |
| 519 | |
| 520 | #endif |
| 521 | |
| 522 | /*----- Main checking function --------------------------------------------*/ |
| 523 | |
| 524 | /* --- @check@ --- * |
| 525 | * |
| 526 | * Arguments: @request *rq@ = pointer to request buffer |
| 527 | * |
| 528 | * Returns: Nonzero if OK, zero if forbidden |
| 529 | * |
| 530 | * Use: Checks to see if the request is acceptable. |
| 531 | */ |
| 532 | |
| 533 | int check(request *rq) |
| 534 | { |
| 535 | FILE *fp; |
| 536 | |
| 537 | /* --- Check if we need to talk to a server --- */ |
| 538 | |
| 539 | #ifndef NONETWORK |
| 540 | if ((fp = fopen(file_SERVER, "r")) != 0) |
| 541 | return (check__client(rq, fp)); |
| 542 | #endif |
| 543 | |
| 544 | /* --- Otherwise do this all the old-fashioned way --- */ |
| 545 | |
| 546 | if ((fp = fopen(file_RULES, "r")) == 0) { |
| 547 | die(1, "couldn't read configuration file `%s': %s", |
| 548 | file_RULES, strerror(errno)); |
| 549 | } |
| 550 | |
| 551 | userdb_init(); |
| 552 | userdb_local(); |
| 553 | userdb_yp(); |
| 554 | netg_init(); |
| 555 | name_init(); |
| 556 | rule_init(); |
| 557 | lexer_scan(fp); |
| 558 | parse(); |
| 559 | fclose(fp); |
| 560 | |
| 561 | return (rule_check(rq)); |
| 562 | } |
| 563 | |
| 564 | /*----- That's all, folks -------------------------------------------------*/ |