1 /* 2 * Copyright (c) 1986 Eric P. Allman 3 * Copyright (c) 1988, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * %sccs.include.redist.c% 7 */ 8 9 #include "sendmail.h" 10 11 #ifndef lint 12 #ifdef NAMED_BIND 13 static char sccsid[] = "@(#)domain.c 8.9 (Berkeley) 11/26/93 (with name server)"; 14 #else 15 static char sccsid[] = "@(#)domain.c 8.9 (Berkeley) 11/26/93 (without name server)"; 16 #endif 17 #endif /* not lint */ 18 19 #ifdef NAMED_BIND 20 21 #include <errno.h> 22 #include <arpa/nameser.h> 23 #include <resolv.h> 24 #include <netdb.h> 25 26 typedef union 27 { 28 HEADER qb1; 29 char qb2[PACKETSZ]; 30 } querybuf; 31 32 static char MXHostBuf[MAXMXHOSTS*PACKETSZ]; 33 34 #ifndef MAXDNSRCH 35 #define MAXDNSRCH 6 /* number of possible domains to search */ 36 #endif 37 38 #ifndef MAX 39 #define MAX(a, b) ((a) > (b) ? (a) : (b)) 40 #endif 41 42 #ifndef NO_DATA 43 # define NO_DATA NO_ADDRESS 44 #endif 45 46 /* don't use sizeof because sizeof(long) is different on 64-bit machines */ 47 #define SHORTSIZE 2 /* size of a short (really, must be 2) */ 48 #define LONGSIZE 4 /* size of a long (really, must be 4) */ 49 50 #define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */ 51 /* 52 ** GETMXRR -- get MX resource records for a domain 53 ** 54 ** Parameters: 55 ** host -- the name of the host to MX. 56 ** mxhosts -- a pointer to a return buffer of MX records. 57 ** droplocalhost -- If TRUE, all MX records less preferred 58 ** than the local host (as determined by $=w) will 59 ** be discarded. 60 ** rcode -- a pointer to an EX_ status code. 61 ** 62 ** Returns: 63 ** The number of MX records found. 64 ** -1 if there is an internal failure. 65 ** If no MX records are found, mxhosts[0] is set to host 66 ** and 1 is returned. 67 */ 68 69 getmxrr(host, mxhosts, droplocalhost, rcode) 70 char *host; 71 char **mxhosts; 72 bool droplocalhost; 73 int *rcode; 74 { 75 extern int h_errno; 76 register u_char *eom, *cp; 77 register int i, j, n; 78 int nmx = 0; 79 register char *bp; 80 HEADER *hp; 81 querybuf answer; 82 int ancount, qdcount, buflen; 83 bool seenlocal = FALSE; 84 u_short pref, localpref, type; 85 char *fallbackMX = FallBackMX; 86 static bool firsttime = TRUE; 87 STAB *st; 88 bool trycanon = FALSE; 89 u_short prefer[MAXMXHOSTS]; 90 int weight[MAXMXHOSTS]; 91 extern bool getcanonname(); 92 93 if (fallbackMX != NULL) 94 { 95 if (firsttime && res_query(FallBackMX, C_IN, T_A, 96 (char *) &answer, sizeof answer) < 0) 97 { 98 /* this entry is bogus */ 99 fallbackMX = FallBackMX = NULL; 100 } 101 else if (droplocalhost && 102 (st = stab(fallbackMX, ST_CLASS, ST_FIND)) != NULL && 103 bitnset('w', st->s_class)) 104 { 105 /* don't use fallback for this pass */ 106 fallbackMX = NULL; 107 } 108 firsttime = FALSE; 109 } 110 111 /* efficiency hack -- numeric or non-MX lookups */ 112 if (host[0] == '[') 113 goto punt; 114 115 errno = 0; 116 n = res_search(host, C_IN, T_MX, (char *)&answer, sizeof(answer)); 117 if (n < 0) 118 { 119 if (tTd(8, 1)) 120 printf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n", 121 (host == NULL) ? "<NULL>" : host, errno, h_errno); 122 switch (h_errno) 123 { 124 case NO_DATA: 125 trycanon = TRUE; 126 /* fall through */ 127 128 case NO_RECOVERY: 129 /* no MX data on this host */ 130 goto punt; 131 132 case HOST_NOT_FOUND: 133 /* the host just doesn't exist */ 134 *rcode = EX_NOHOST; 135 136 if (!UseNameServer) 137 { 138 /* might exist in /etc/hosts */ 139 goto punt; 140 } 141 break; 142 143 case TRY_AGAIN: 144 /* couldn't connect to the name server */ 145 if (!UseNameServer && errno == ECONNREFUSED) 146 goto punt; 147 148 /* it might come up later; better queue it up */ 149 *rcode = EX_TEMPFAIL; 150 break; 151 } 152 153 /* irreconcilable differences */ 154 return (-1); 155 } 156 157 /* find first satisfactory answer */ 158 hp = (HEADER *)&answer; 159 cp = (u_char *)&answer + sizeof(HEADER); 160 eom = (u_char *)&answer + n; 161 for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ) 162 if ((n = dn_skipname(cp, eom)) < 0) 163 goto punt; 164 buflen = sizeof(MXHostBuf) - 1; 165 bp = MXHostBuf; 166 ancount = ntohs(hp->ancount); 167 while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1) 168 { 169 if ((n = dn_expand((u_char *)&answer, 170 eom, cp, (u_char *)bp, buflen)) < 0) 171 break; 172 cp += n; 173 GETSHORT(type, cp); 174 cp += SHORTSIZE + LONGSIZE; 175 GETSHORT(n, cp); 176 if (type != T_MX) 177 { 178 if (tTd(8, 8) || _res.options & RES_DEBUG) 179 printf("unexpected answer type %d, size %d\n", 180 type, n); 181 cp += n; 182 continue; 183 } 184 GETSHORT(pref, cp); 185 if ((n = dn_expand((u_char *)&answer, eom, cp, 186 (u_char *)bp, buflen)) < 0) 187 break; 188 cp += n; 189 if (droplocalhost && 190 (st = stab(bp, ST_CLASS, ST_FIND)) != NULL && 191 bitnset('w', st->s_class)) 192 { 193 if (!seenlocal || pref < localpref) 194 localpref = pref; 195 seenlocal = TRUE; 196 continue; 197 } 198 weight[nmx] = mxrand(bp); 199 prefer[nmx] = pref; 200 mxhosts[nmx++] = bp; 201 n = strlen(bp); 202 bp += n; 203 if (bp[-1] != '.') 204 { 205 *bp++ = '.'; 206 n++; 207 } 208 *bp++ = '\0'; 209 buflen -= n + 1; 210 } 211 212 /* sort the records */ 213 for (i = 0; i < nmx; i++) 214 { 215 for (j = i + 1; j < nmx; j++) 216 { 217 if (prefer[i] > prefer[j] || 218 (prefer[i] == prefer[j] && weight[i] > weight[j])) 219 { 220 register int temp; 221 register char *temp1; 222 223 temp = prefer[i]; 224 prefer[i] = prefer[j]; 225 prefer[j] = temp; 226 temp1 = mxhosts[i]; 227 mxhosts[i] = mxhosts[j]; 228 mxhosts[j] = temp1; 229 temp = weight[i]; 230 weight[i] = weight[j]; 231 weight[j] = temp; 232 } 233 } 234 if (seenlocal && prefer[i] >= localpref) 235 { 236 /* truncate higher preference part of list */ 237 nmx = i; 238 } 239 } 240 241 if (nmx == 0) 242 { 243 punt: 244 if (seenlocal && 245 (!TryNullMXList || gethostbyname(host) == NULL)) 246 { 247 /* 248 ** If we have deleted all MX entries, this is 249 ** an error -- we should NEVER send to a host that 250 ** has an MX, and this should have been caught 251 ** earlier in the config file. 252 ** 253 ** Some sites prefer to go ahead and try the 254 ** A record anyway; that case is handled by 255 ** setting TryNullMXList. I believe this is a 256 ** bad idea, but it's up to you.... 257 */ 258 259 *rcode = EX_CONFIG; 260 return -1; 261 } 262 strcpy(MXHostBuf, host); 263 mxhosts[0] = MXHostBuf; 264 if (host[0] == '[') 265 { 266 register char *p; 267 268 /* this may be an MX suppression-style address */ 269 p = strchr(MXHostBuf, ']'); 270 if (p != NULL) 271 { 272 *p = '\0'; 273 if (inet_addr(&MXHostBuf[1]) != -1) 274 *p = ']'; 275 else 276 { 277 trycanon = TRUE; 278 mxhosts[0]++; 279 } 280 } 281 } 282 if (trycanon && 283 getcanonname(mxhosts[0], sizeof MXHostBuf - 2, FALSE)) 284 { 285 bp = &MXHostBuf[strlen(MXHostBuf)]; 286 if (bp[-1] != '.') 287 { 288 *bp++ = '.'; 289 *bp = '\0'; 290 } 291 } 292 nmx = 1; 293 } 294 295 /* if we have a default lowest preference, include that */ 296 if (fallbackMX != NULL && !seenlocal) 297 mxhosts[nmx++] = fallbackMX; 298 299 return (nmx); 300 } 301 /* 302 ** MXRAND -- create a randomizer for equal MX preferences 303 ** 304 ** If two MX hosts have equal preferences we want to randomize 305 ** the selection. But in order for signatures to be the same, 306 ** we need to randomize the same way each time. This function 307 ** computes a pseudo-random hash function from the host name. 308 ** 309 ** Parameters: 310 ** host -- the name of the host. 311 ** 312 ** Returns: 313 ** A random but repeatable value based on the host name. 314 ** 315 ** Side Effects: 316 ** none. 317 */ 318 319 mxrand(host) 320 register char *host; 321 { 322 int hfunc; 323 static unsigned int seed; 324 325 if (seed == 0) 326 { 327 seed = (int) curtime() & 0xffff; 328 if (seed == 0) 329 seed++; 330 } 331 332 if (tTd(17, 9)) 333 printf("mxrand(%s)", host); 334 335 hfunc = seed; 336 while (*host != '\0') 337 { 338 int c = *host++; 339 340 if (isascii(c) && isupper(c)) 341 c = tolower(c); 342 hfunc = ((hfunc << 1) + c) % 2003; 343 } 344 345 hfunc &= 0xff; 346 347 if (tTd(17, 9)) 348 printf(" = %d\n", hfunc); 349 return hfunc; 350 } 351 /* 352 ** GETCANONNAME -- get the canonical name for named host 353 ** 354 ** This algorithm tries to be smart about wildcard MX records. 355 ** This is hard to do because DNS doesn't tell is if we matched 356 ** against a wildcard or a specific MX. 357 ** 358 ** We always prefer A & CNAME records, since these are presumed 359 ** to be specific. 360 ** 361 ** If we match an MX in one pass and lose it in the next, we use 362 ** the old one. For example, consider an MX matching *.FOO.BAR.COM. 363 ** A hostname bletch.foo.bar.com will match against this MX, but 364 ** will stop matching when we try bletch.bar.com -- so we know 365 ** that bletch.foo.bar.com must have been right. This fails if 366 ** there was also an MX record matching *.BAR.COM, but there are 367 ** some things that just can't be fixed. 368 ** 369 ** Parameters: 370 ** host -- a buffer containing the name of the host. 371 ** This is a value-result parameter. 372 ** hbsize -- the size of the host buffer. 373 ** trymx -- if set, try MX records as well as A and CNAME. 374 ** 375 ** Returns: 376 ** TRUE -- if the host matched. 377 ** FALSE -- otherwise. 378 */ 379 380 bool 381 getcanonname(host, hbsize, trymx) 382 char *host; 383 int hbsize; 384 bool trymx; 385 { 386 extern int h_errno; 387 register u_char *eom, *ap; 388 register char *cp; 389 register int n; 390 HEADER *hp; 391 querybuf answer; 392 int ancount, qdcount; 393 int ret; 394 char **domain; 395 int type; 396 char **dp; 397 char *mxmatch; 398 bool amatch; 399 bool gotmx; 400 int qtype; 401 int loopcnt; 402 char nbuf[MAX(PACKETSZ, MAXDNAME*2+2)]; 403 char *searchlist[MAXDNSRCH+2]; 404 405 if (tTd(8, 2)) 406 printf("getcanonname(%s)\n", host); 407 408 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 409 return (FALSE); 410 411 /* 412 ** Initialize domain search list. If there is at least one 413 ** dot in the name, search the unmodified name first so we 414 ** find "vse.CS" in Czechoslovakia instead of in the local 415 ** domain (e.g., vse.CS.Berkeley.EDU). 416 ** 417 ** Older versions of the resolver could create this 418 ** list by tearing apart the host name. 419 */ 420 421 loopcnt = 0; 422 cnameloop: 423 for (cp = host, n = 0; *cp; cp++) 424 if (*cp == '.') 425 n++; 426 427 dp = searchlist; 428 if (n > 0) 429 *dp++ = ""; 430 if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options)) 431 { 432 for (domain = _res.dnsrch; *domain != NULL; ) 433 *dp++ = *domain++; 434 } 435 else if (n == 0 && bitset(RES_DEFNAMES, _res.options)) 436 { 437 *dp++ = _res.defdname; 438 } 439 *dp = NULL; 440 441 /* 442 ** Now run through the search list for the name in question. 443 */ 444 445 mxmatch = NULL; 446 qtype = T_ANY; 447 448 for (dp = searchlist; *dp != NULL; ) 449 { 450 if (qtype == T_ANY) 451 gotmx = FALSE; 452 if (tTd(8, 5)) 453 printf("getcanonname: trying %s.%s (%s)\n", host, *dp, 454 qtype == T_ANY ? "ANY" : qtype == T_A ? "A" : 455 qtype == T_MX ? "MX" : "???"); 456 ret = res_querydomain(host, *dp, C_IN, qtype, 457 &answer, sizeof(answer)); 458 if (ret <= 0) 459 { 460 if (tTd(8, 7)) 461 printf("\tNO: errno=%d, h_errno=%d\n", 462 errno, h_errno); 463 464 if (errno == ECONNREFUSED || h_errno == TRY_AGAIN) 465 { 466 /* the name server seems to be down */ 467 h_errno = TRY_AGAIN; 468 return FALSE; 469 } 470 471 if (h_errno != HOST_NOT_FOUND) 472 { 473 /* might have another type of interest */ 474 if (qtype == T_ANY) 475 { 476 qtype = T_A; 477 continue; 478 } 479 else if (qtype == T_A && !gotmx && trymx) 480 { 481 qtype = T_MX; 482 continue; 483 } 484 } 485 486 if (mxmatch != NULL) 487 { 488 /* we matched before -- use that one */ 489 break; 490 } 491 492 /* otherwise, try the next name */ 493 dp++; 494 qtype = T_ANY; 495 continue; 496 } 497 else if (tTd(8, 7)) 498 printf("\tYES\n"); 499 500 /* 501 ** This might be a bogus match. Search for A or 502 ** CNAME records. If we don't have a matching 503 ** wild card MX record, we will accept MX as well. 504 */ 505 506 hp = (HEADER *) &answer; 507 ap = (u_char *) &answer + sizeof(HEADER); 508 eom = (u_char *) &answer + ret; 509 510 /* skip question part of response -- we know what we asked */ 511 for (qdcount = ntohs(hp->qdcount); qdcount--; ap += ret + QFIXEDSZ) 512 { 513 if ((ret = dn_skipname(ap, eom)) < 0) 514 { 515 if (tTd(8, 20)) 516 printf("qdcount failure (%d)\n", 517 ntohs(hp->qdcount)); 518 return FALSE; /* ???XXX??? */ 519 } 520 } 521 522 amatch = FALSE; 523 for (ancount = ntohs(hp->ancount); --ancount >= 0 && ap < eom; ap += n) 524 { 525 n = dn_expand((u_char *) &answer, eom, ap, 526 (u_char *) nbuf, sizeof nbuf); 527 if (n < 0) 528 break; 529 ap += n; 530 GETSHORT(type, ap); 531 ap += SHORTSIZE + LONGSIZE; 532 GETSHORT(n, ap); 533 switch (type) 534 { 535 case T_MX: 536 gotmx = TRUE; 537 if (**dp != '\0') 538 { 539 /* got a match -- save that info */ 540 if (trymx && mxmatch == NULL) 541 mxmatch = *dp; 542 continue; 543 } 544 545 /* exact MX matches are as good as an A match */ 546 /* fall through */ 547 548 case T_A: 549 /* good show */ 550 amatch = TRUE; 551 552 /* continue in case a CNAME also exists */ 553 continue; 554 555 case T_CNAME: 556 if (loopcnt++ > MAXCNAMEDEPTH) 557 { 558 syserr("DNS failure: CNAME loop for %s", 559 host); 560 continue; 561 } 562 563 /* value points at name */ 564 if ((ret = dn_expand((u_char *)&answer, 565 eom, ap, (u_char *)nbuf, sizeof(nbuf))) < 0) 566 break; 567 (void)strncpy(host, nbuf, hbsize); /* XXX */ 568 host[hbsize - 1] = '\0'; 569 570 /* 571 ** RFC 1034 section 3.6 specifies that CNAME 572 ** should point at the canonical name -- but 573 ** urges software to try again anyway. 574 */ 575 576 goto cnameloop; 577 578 default: 579 /* not a record of interest */ 580 continue; 581 } 582 } 583 584 if (amatch) 585 { 586 /* got an A record and no CNAME */ 587 mxmatch = *dp; 588 break; 589 } 590 591 /* 592 ** If this was a T_ANY query, we may have the info but 593 ** need an explicit query. Try T_A, then T_MX. 594 */ 595 596 if (qtype == T_ANY) 597 qtype = T_A; 598 else if (qtype == T_A && !gotmx && trymx) 599 qtype = T_MX; 600 else 601 { 602 /* really nothing in this domain; try the next */ 603 qtype = T_ANY; 604 dp++; 605 } 606 } 607 608 if (mxmatch == NULL) 609 return FALSE; 610 611 /* create matching name and return */ 612 (void) sprintf(nbuf, "%.*s%s%.*s", MAXDNAME, host, 613 *mxmatch == '\0' ? "" : ".", 614 MAXDNAME, mxmatch); 615 strncpy(host, nbuf, hbsize); 616 host[hbsize - 1] = '\0'; 617 return TRUE; 618 } 619 620 #else /* not NAMED_BIND */ 621 622 #include <netdb.h> 623 624 bool 625 getcanonname(host, hbsize, trymx) 626 char *host; 627 int hbsize; 628 bool trymx; 629 { 630 struct hostent *hp; 631 632 hp = gethostbyname(host); 633 if (hp == NULL) 634 return (FALSE); 635 636 if (strlen(hp->h_name) >= hbsize) 637 return (FALSE); 638 639 (void) strcpy(host, hp->h_name); 640 return (TRUE); 641 } 642 643 #endif /* not NAMED_BIND */ 644