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 8.15 (Berkeley) 02/25/94 (with name server)"; 14 #else 15 static char sccsid[] = "@(#)domain.c 8.15 (Berkeley) 02/25/94 (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 #ifndef HEADERSZ 47 # define HEADERSZ sizeof(HEADER) 48 #endif 49 50 /* don't use sizeof because sizeof(long) is different on 64-bit machines */ 51 #define SHORTSIZE 2 /* size of a short (really, must be 2) */ 52 #define LONGSIZE 4 /* size of a long (really, must be 4) */ 53 54 #define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */ 55 /* 56 ** GETMXRR -- get MX resource records for a domain 57 ** 58 ** Parameters: 59 ** host -- the name of the host to MX. 60 ** mxhosts -- a pointer to a return buffer of MX records. 61 ** droplocalhost -- If TRUE, all MX records less preferred 62 ** than the local host (as determined by $=w) will 63 ** be discarded. 64 ** rcode -- a pointer to an EX_ status code. 65 ** 66 ** Returns: 67 ** The number of MX records found. 68 ** -1 if there is an internal failure. 69 ** If no MX records are found, mxhosts[0] is set to host 70 ** and 1 is returned. 71 */ 72 73 getmxrr(host, mxhosts, droplocalhost, rcode) 74 char *host; 75 char **mxhosts; 76 bool droplocalhost; 77 int *rcode; 78 { 79 extern int h_errno; 80 register u_char *eom, *cp; 81 register int i, j, n; 82 int nmx = 0; 83 register char *bp; 84 HEADER *hp; 85 querybuf answer; 86 int ancount, qdcount, buflen; 87 bool seenlocal = FALSE; 88 u_short pref, localpref, type; 89 char *fallbackMX = FallBackMX; 90 static bool firsttime = TRUE; 91 STAB *st; 92 bool trycanon = FALSE; 93 u_short prefer[MAXMXHOSTS]; 94 int weight[MAXMXHOSTS]; 95 extern bool getcanonname(); 96 97 if (tTd(8, 2)) 98 printf("getmxrr(%s, droplocalhost=%d)\n", host, droplocalhost); 99 100 if (fallbackMX != NULL) 101 { 102 if (firsttime && res_query(FallBackMX, C_IN, T_A, 103 (char *) &answer, sizeof answer) < 0) 104 { 105 /* this entry is bogus */ 106 fallbackMX = FallBackMX = NULL; 107 } 108 else if (droplocalhost && 109 (st = stab(fallbackMX, ST_CLASS, ST_FIND)) != NULL && 110 bitnset('w', st->s_class)) 111 { 112 /* don't use fallback for this pass */ 113 fallbackMX = NULL; 114 } 115 firsttime = FALSE; 116 } 117 118 /* efficiency hack -- numeric or non-MX lookups */ 119 if (host[0] == '[') 120 goto punt; 121 122 errno = 0; 123 n = res_search(host, C_IN, T_MX, (char *)&answer, sizeof(answer)); 124 if (n < 0) 125 { 126 if (tTd(8, 1)) 127 printf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n", 128 (host == NULL) ? "<NULL>" : host, errno, h_errno); 129 switch (h_errno) 130 { 131 case NO_DATA: 132 trycanon = TRUE; 133 /* fall through */ 134 135 case NO_RECOVERY: 136 /* no MX data on this host */ 137 goto punt; 138 139 case HOST_NOT_FOUND: 140 /* the host just doesn't exist */ 141 *rcode = EX_NOHOST; 142 143 if (!UseNameServer) 144 { 145 /* might exist in /etc/hosts */ 146 goto punt; 147 } 148 break; 149 150 case TRY_AGAIN: 151 /* couldn't connect to the name server */ 152 if (!UseNameServer && errno == ECONNREFUSED) 153 goto punt; 154 155 /* it might come up later; better queue it up */ 156 *rcode = EX_TEMPFAIL; 157 break; 158 159 default: 160 syserr("getmxrr: res_search (%s) failed with impossible h_errno (%d)\n", 161 host, h_errno); 162 *rcode = EX_OSERR; 163 break; 164 } 165 166 /* irreconcilable differences */ 167 return (-1); 168 } 169 170 /* find first satisfactory answer */ 171 hp = (HEADER *)&answer; 172 cp = (u_char *)&answer + HEADERSZ; 173 eom = (u_char *)&answer + n; 174 for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ) 175 if ((n = dn_skipname(cp, eom)) < 0) 176 goto punt; 177 buflen = sizeof(MXHostBuf) - 1; 178 bp = MXHostBuf; 179 ancount = ntohs(hp->ancount); 180 while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1) 181 { 182 if ((n = dn_expand((u_char *)&answer, 183 eom, cp, (u_char *)bp, buflen)) < 0) 184 break; 185 cp += n; 186 GETSHORT(type, cp); 187 cp += SHORTSIZE + LONGSIZE; 188 GETSHORT(n, cp); 189 if (type != T_MX) 190 { 191 if (tTd(8, 8) || _res.options & RES_DEBUG) 192 printf("unexpected answer type %d, size %d\n", 193 type, n); 194 cp += n; 195 continue; 196 } 197 GETSHORT(pref, cp); 198 if ((n = dn_expand((u_char *)&answer, eom, cp, 199 (u_char *)bp, buflen)) < 0) 200 break; 201 cp += n; 202 if (droplocalhost && 203 (st = stab(bp, ST_CLASS, ST_FIND)) != NULL && 204 bitnset('w', st->s_class)) 205 { 206 if (tTd(8, 3)) 207 printf("found localhost (%s) in MX list, pref=%d\n", 208 bp, pref); 209 if (!seenlocal || pref < localpref) 210 localpref = pref; 211 seenlocal = TRUE; 212 continue; 213 } 214 weight[nmx] = mxrand(bp); 215 prefer[nmx] = pref; 216 mxhosts[nmx++] = bp; 217 n = strlen(bp); 218 bp += n; 219 if (bp[-1] != '.') 220 { 221 *bp++ = '.'; 222 n++; 223 } 224 *bp++ = '\0'; 225 buflen -= n + 1; 226 } 227 228 /* sort the records */ 229 for (i = 0; i < nmx; i++) 230 { 231 for (j = i + 1; j < nmx; j++) 232 { 233 if (prefer[i] > prefer[j] || 234 (prefer[i] == prefer[j] && weight[i] > weight[j])) 235 { 236 register int temp; 237 register char *temp1; 238 239 temp = prefer[i]; 240 prefer[i] = prefer[j]; 241 prefer[j] = temp; 242 temp1 = mxhosts[i]; 243 mxhosts[i] = mxhosts[j]; 244 mxhosts[j] = temp1; 245 temp = weight[i]; 246 weight[i] = weight[j]; 247 weight[j] = temp; 248 } 249 } 250 if (seenlocal && prefer[i] >= localpref) 251 { 252 /* truncate higher preference part of list */ 253 nmx = i; 254 } 255 } 256 257 if (nmx == 0) 258 { 259 punt: 260 if (seenlocal && 261 (!TryNullMXList || gethostbyname(host) == NULL)) 262 { 263 /* 264 ** If we have deleted all MX entries, this is 265 ** an error -- we should NEVER send to a host that 266 ** has an MX, and this should have been caught 267 ** earlier in the config file. 268 ** 269 ** Some sites prefer to go ahead and try the 270 ** A record anyway; that case is handled by 271 ** setting TryNullMXList. I believe this is a 272 ** bad idea, but it's up to you.... 273 */ 274 275 *rcode = EX_CONFIG; 276 return -1; 277 } 278 strcpy(MXHostBuf, host); 279 mxhosts[0] = MXHostBuf; 280 if (host[0] == '[') 281 { 282 register char *p; 283 284 /* this may be an MX suppression-style address */ 285 p = strchr(MXHostBuf, ']'); 286 if (p != NULL) 287 { 288 *p = '\0'; 289 if (inet_addr(&MXHostBuf[1]) != -1) 290 *p = ']'; 291 else 292 { 293 trycanon = TRUE; 294 mxhosts[0]++; 295 } 296 } 297 } 298 if (trycanon && 299 getcanonname(mxhosts[0], sizeof MXHostBuf - 2, FALSE)) 300 { 301 bp = &MXHostBuf[strlen(MXHostBuf)]; 302 if (bp[-1] != '.') 303 { 304 *bp++ = '.'; 305 *bp = '\0'; 306 } 307 } 308 nmx = 1; 309 } 310 311 /* if we have a default lowest preference, include that */ 312 if (fallbackMX != NULL && !seenlocal) 313 mxhosts[nmx++] = fallbackMX; 314 315 return (nmx); 316 } 317 /* 318 ** MXRAND -- create a randomizer for equal MX preferences 319 ** 320 ** If two MX hosts have equal preferences we want to randomize 321 ** the selection. But in order for signatures to be the same, 322 ** we need to randomize the same way each time. This function 323 ** computes a pseudo-random hash function from the host name. 324 ** 325 ** Parameters: 326 ** host -- the name of the host. 327 ** 328 ** Returns: 329 ** A random but repeatable value based on the host name. 330 ** 331 ** Side Effects: 332 ** none. 333 */ 334 335 mxrand(host) 336 register char *host; 337 { 338 int hfunc; 339 static unsigned int seed; 340 341 if (seed == 0) 342 { 343 seed = (int) curtime() & 0xffff; 344 if (seed == 0) 345 seed++; 346 } 347 348 if (tTd(17, 9)) 349 printf("mxrand(%s)", host); 350 351 hfunc = seed; 352 while (*host != '\0') 353 { 354 int c = *host++; 355 356 if (isascii(c) && isupper(c)) 357 c = tolower(c); 358 hfunc = ((hfunc << 1) ^ c) % 2003; 359 } 360 361 hfunc &= 0xff; 362 363 if (tTd(17, 9)) 364 printf(" = %d\n", hfunc); 365 return hfunc; 366 } 367 /* 368 ** GETCANONNAME -- get the canonical name for named host 369 ** 370 ** This algorithm tries to be smart about wildcard MX records. 371 ** This is hard to do because DNS doesn't tell is if we matched 372 ** against a wildcard or a specific MX. 373 ** 374 ** We always prefer A & CNAME records, since these are presumed 375 ** to be specific. 376 ** 377 ** If we match an MX in one pass and lose it in the next, we use 378 ** the old one. For example, consider an MX matching *.FOO.BAR.COM. 379 ** A hostname bletch.foo.bar.com will match against this MX, but 380 ** will stop matching when we try bletch.bar.com -- so we know 381 ** that bletch.foo.bar.com must have been right. This fails if 382 ** there was also an MX record matching *.BAR.COM, but there are 383 ** some things that just can't be fixed. 384 ** 385 ** Parameters: 386 ** host -- a buffer containing the name of the host. 387 ** This is a value-result parameter. 388 ** hbsize -- the size of the host buffer. 389 ** trymx -- if set, try MX records as well as A and CNAME. 390 ** 391 ** Returns: 392 ** TRUE -- if the host matched. 393 ** FALSE -- otherwise. 394 */ 395 396 bool 397 getcanonname(host, hbsize, trymx) 398 char *host; 399 int hbsize; 400 bool trymx; 401 { 402 extern int h_errno; 403 register u_char *eom, *ap; 404 register char *cp; 405 register int n; 406 HEADER *hp; 407 querybuf answer; 408 int ancount, qdcount; 409 int ret; 410 char **domain; 411 int type; 412 char **dp; 413 char *mxmatch; 414 bool amatch; 415 bool gotmx; 416 int qtype; 417 int loopcnt; 418 char *xp; 419 char nbuf[MAX(PACKETSZ, MAXDNAME*2+2)]; 420 char *searchlist[MAXDNSRCH+2]; 421 extern char *gethostalias(); 422 423 if (tTd(8, 2)) 424 printf("getcanonname(%s)\n", host); 425 426 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 427 return (FALSE); 428 429 /* 430 ** Initialize domain search list. If there is at least one 431 ** dot in the name, search the unmodified name first so we 432 ** find "vse.CS" in Czechoslovakia instead of in the local 433 ** domain (e.g., vse.CS.Berkeley.EDU). 434 ** 435 ** Older versions of the resolver could create this 436 ** list by tearing apart the host name. 437 */ 438 439 loopcnt = 0; 440 cnameloop: 441 for (cp = host, n = 0; *cp; cp++) 442 if (*cp == '.') 443 n++; 444 445 if (n == 0 && (xp = gethostalias(host)) != NULL) 446 { 447 if (loopcnt++ > MAXCNAMEDEPTH) 448 { 449 syserr("loop in ${HOSTALIASES} file"); 450 } 451 else 452 { 453 strncpy(host, xp, hbsize); 454 host[hbsize - 1] = '\0'; 455 goto cnameloop; 456 } 457 } 458 459 dp = searchlist; 460 if (n > 0) 461 *dp++ = ""; 462 if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options)) 463 { 464 for (domain = _res.dnsrch; *domain != NULL; ) 465 *dp++ = *domain++; 466 } 467 else if (n == 0 && bitset(RES_DEFNAMES, _res.options)) 468 { 469 *dp++ = _res.defdname; 470 } 471 else if (*cp == '.') 472 { 473 *cp = '\0'; 474 } 475 *dp = NULL; 476 477 /* 478 ** Now run through the search list for the name in question. 479 */ 480 481 mxmatch = NULL; 482 qtype = T_ANY; 483 484 for (dp = searchlist; *dp != NULL; ) 485 { 486 if (qtype == T_ANY) 487 gotmx = FALSE; 488 if (tTd(8, 5)) 489 printf("getcanonname: trying %s.%s (%s)\n", host, *dp, 490 qtype == T_ANY ? "ANY" : qtype == T_A ? "A" : 491 qtype == T_MX ? "MX" : "???"); 492 ret = res_querydomain(host, *dp, C_IN, qtype, 493 &answer, sizeof(answer)); 494 if (ret <= 0) 495 { 496 if (tTd(8, 7)) 497 printf("\tNO: errno=%d, h_errno=%d\n", 498 errno, h_errno); 499 500 if (errno == ECONNREFUSED || h_errno == TRY_AGAIN) 501 { 502 /* the name server seems to be down */ 503 h_errno = TRY_AGAIN; 504 return FALSE; 505 } 506 507 if (h_errno != HOST_NOT_FOUND) 508 { 509 /* might have another type of interest */ 510 if (qtype == T_ANY) 511 { 512 qtype = T_A; 513 continue; 514 } 515 else if (qtype == T_A && !gotmx && trymx) 516 { 517 qtype = T_MX; 518 continue; 519 } 520 } 521 522 if (mxmatch != NULL) 523 { 524 /* we matched before -- use that one */ 525 break; 526 } 527 528 /* otherwise, try the next name */ 529 dp++; 530 qtype = T_ANY; 531 continue; 532 } 533 else if (tTd(8, 7)) 534 printf("\tYES\n"); 535 536 /* 537 ** This might be a bogus match. Search for A or 538 ** CNAME records. If we don't have a matching 539 ** wild card MX record, we will accept MX as well. 540 */ 541 542 hp = (HEADER *) &answer; 543 ap = (u_char *) &answer + HEADERSZ; 544 eom = (u_char *) &answer + ret; 545 546 /* skip question part of response -- we know what we asked */ 547 for (qdcount = ntohs(hp->qdcount); qdcount--; ap += ret + QFIXEDSZ) 548 { 549 if ((ret = dn_skipname(ap, eom)) < 0) 550 { 551 if (tTd(8, 20)) 552 printf("qdcount failure (%d)\n", 553 ntohs(hp->qdcount)); 554 return FALSE; /* ???XXX??? */ 555 } 556 } 557 558 amatch = FALSE; 559 for (ancount = ntohs(hp->ancount); --ancount >= 0 && ap < eom; ap += n) 560 { 561 n = dn_expand((u_char *) &answer, eom, ap, 562 (u_char *) nbuf, sizeof nbuf); 563 if (n < 0) 564 break; 565 ap += n; 566 GETSHORT(type, ap); 567 ap += SHORTSIZE + LONGSIZE; 568 GETSHORT(n, ap); 569 switch (type) 570 { 571 case T_MX: 572 gotmx = TRUE; 573 if (**dp != '\0') 574 { 575 /* got a match -- save that info */ 576 if (trymx && mxmatch == NULL) 577 mxmatch = *dp; 578 continue; 579 } 580 581 /* exact MX matches are as good as an A match */ 582 /* fall through */ 583 584 case T_A: 585 /* good show */ 586 amatch = TRUE; 587 588 /* continue in case a CNAME also exists */ 589 continue; 590 591 case T_CNAME: 592 if (loopcnt++ > MAXCNAMEDEPTH) 593 { 594 syserr("DNS failure: CNAME loop for %s", 595 host); 596 continue; 597 } 598 599 /* value points at name */ 600 if ((ret = dn_expand((u_char *)&answer, 601 eom, ap, (u_char *)nbuf, sizeof(nbuf))) < 0) 602 break; 603 (void)strncpy(host, nbuf, hbsize); /* XXX */ 604 host[hbsize - 1] = '\0'; 605 606 /* 607 ** RFC 1034 section 3.6 specifies that CNAME 608 ** should point at the canonical name -- but 609 ** urges software to try again anyway. 610 */ 611 612 goto cnameloop; 613 614 default: 615 /* not a record of interest */ 616 continue; 617 } 618 } 619 620 if (amatch) 621 { 622 /* got an A record and no CNAME */ 623 mxmatch = *dp; 624 break; 625 } 626 627 /* 628 ** If this was a T_ANY query, we may have the info but 629 ** need an explicit query. Try T_A, then T_MX. 630 */ 631 632 if (qtype == T_ANY) 633 qtype = T_A; 634 else if (qtype == T_A && !gotmx && trymx) 635 qtype = T_MX; 636 else 637 { 638 /* really nothing in this domain; try the next */ 639 qtype = T_ANY; 640 dp++; 641 } 642 } 643 644 if (mxmatch == NULL) 645 return FALSE; 646 647 /* create matching name and return */ 648 (void) sprintf(nbuf, "%.*s%s%.*s", MAXDNAME, host, 649 *mxmatch == '\0' ? "" : ".", 650 MAXDNAME, mxmatch); 651 strncpy(host, nbuf, hbsize); 652 host[hbsize - 1] = '\0'; 653 return TRUE; 654 } 655 656 657 char * 658 gethostalias(host) 659 char *host; 660 { 661 char *fname; 662 FILE *fp; 663 register char *p; 664 char buf[MAXLINE]; 665 static char hbuf[MAXDNAME]; 666 667 fname = getenv("HOSTALIASES"); 668 if (fname == NULL || (fp = fopen(fname, "r")) == NULL) 669 return NULL; 670 while (fgets(buf, sizeof buf, fp) != NULL) 671 { 672 for (p = buf; p != '\0' && !(isascii(*p) && isspace(*p)); p++) 673 continue; 674 if (*p == 0) 675 { 676 /* syntax error */ 677 continue; 678 } 679 *p++ = '\0'; 680 if (strcasecmp(buf, host) == 0) 681 break; 682 } 683 684 if (feof(fp)) 685 { 686 /* no match */ 687 fclose(fp); 688 return NULL; 689 } 690 691 /* got a match; extract the equivalent name */ 692 while (*p != '\0' && isascii(*p) && isspace(*p)) 693 p++; 694 host = p; 695 while (*p != '\0' && !(isascii(*p) && isspace(*p))) 696 p++; 697 *p = '\0'; 698 strncpy(hbuf, host, sizeof hbuf - 1); 699 hbuf[sizeof hbuf - 1] = '\0'; 700 return hbuf; 701 } 702 703 704 #else /* not NAMED_BIND */ 705 706 #include <netdb.h> 707 708 bool 709 getcanonname(host, hbsize, trymx) 710 char *host; 711 int hbsize; 712 bool trymx; 713 { 714 struct hostent *hp; 715 716 hp = gethostbyname(host); 717 if (hp == NULL) 718 return (FALSE); 719 720 if (strlen(hp->h_name) >= hbsize) 721 return (FALSE); 722 723 (void) strcpy(host, hp->h_name); 724 return (TRUE); 725 } 726 727 #endif /* not NAMED_BIND */ 728