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 8.11 (Berkeley) 01/15/94 (with name server)"; 14 #else 15 static char sccsid[] = "@(#)domain.c 8.11 (Berkeley) 01/15/94 (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 (fallbackMX != NULL) 98 { 99 if (firsttime && res_query(FallBackMX, C_IN, T_A, 100 (char *) &answer, sizeof answer) < 0) 101 { 102 /* this entry is bogus */ 103 fallbackMX = FallBackMX = NULL; 104 } 105 else if (droplocalhost && 106 (st = stab(fallbackMX, ST_CLASS, ST_FIND)) != NULL && 107 bitnset('w', st->s_class)) 108 { 109 /* don't use fallback for this pass */ 110 fallbackMX = NULL; 111 } 112 firsttime = FALSE; 113 } 114 115 /* efficiency hack -- numeric or non-MX lookups */ 116 if (host[0] == '[') 117 goto punt; 118 119 errno = 0; 120 n = res_search(host, C_IN, T_MX, (char *)&answer, sizeof(answer)); 121 if (n < 0) 122 { 123 if (tTd(8, 1)) 124 printf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n", 125 (host == NULL) ? "<NULL>" : host, errno, h_errno); 126 switch (h_errno) 127 { 128 case NO_DATA: 129 trycanon = TRUE; 130 /* fall through */ 131 132 case NO_RECOVERY: 133 /* no MX data on this host */ 134 goto punt; 135 136 case HOST_NOT_FOUND: 137 /* the host just doesn't exist */ 138 *rcode = EX_NOHOST; 139 140 if (!UseNameServer) 141 { 142 /* might exist in /etc/hosts */ 143 goto punt; 144 } 145 break; 146 147 case TRY_AGAIN: 148 /* couldn't connect to the name server */ 149 if (!UseNameServer && errno == ECONNREFUSED) 150 goto punt; 151 152 /* it might come up later; better queue it up */ 153 *rcode = EX_TEMPFAIL; 154 break; 155 } 156 157 /* irreconcilable differences */ 158 return (-1); 159 } 160 161 /* find first satisfactory answer */ 162 hp = (HEADER *)&answer; 163 cp = (u_char *)&answer + HEADERSZ; 164 eom = (u_char *)&answer + n; 165 for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ) 166 if ((n = dn_skipname(cp, eom)) < 0) 167 goto punt; 168 buflen = sizeof(MXHostBuf) - 1; 169 bp = MXHostBuf; 170 ancount = ntohs(hp->ancount); 171 while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1) 172 { 173 if ((n = dn_expand((u_char *)&answer, 174 eom, cp, (u_char *)bp, buflen)) < 0) 175 break; 176 cp += n; 177 GETSHORT(type, cp); 178 cp += SHORTSIZE + LONGSIZE; 179 GETSHORT(n, cp); 180 if (type != T_MX) 181 { 182 if (tTd(8, 8) || _res.options & RES_DEBUG) 183 printf("unexpected answer type %d, size %d\n", 184 type, n); 185 cp += n; 186 continue; 187 } 188 GETSHORT(pref, cp); 189 if ((n = dn_expand((u_char *)&answer, eom, cp, 190 (u_char *)bp, buflen)) < 0) 191 break; 192 cp += n; 193 if (droplocalhost && 194 (st = stab(bp, ST_CLASS, ST_FIND)) != NULL && 195 bitnset('w', st->s_class)) 196 { 197 if (!seenlocal || pref < localpref) 198 localpref = pref; 199 seenlocal = TRUE; 200 continue; 201 } 202 weight[nmx] = mxrand(bp); 203 prefer[nmx] = pref; 204 mxhosts[nmx++] = bp; 205 n = strlen(bp); 206 bp += n; 207 if (bp[-1] != '.') 208 { 209 *bp++ = '.'; 210 n++; 211 } 212 *bp++ = '\0'; 213 buflen -= n + 1; 214 } 215 216 /* sort the records */ 217 for (i = 0; i < nmx; i++) 218 { 219 for (j = i + 1; j < nmx; j++) 220 { 221 if (prefer[i] > prefer[j] || 222 (prefer[i] == prefer[j] && weight[i] > weight[j])) 223 { 224 register int temp; 225 register char *temp1; 226 227 temp = prefer[i]; 228 prefer[i] = prefer[j]; 229 prefer[j] = temp; 230 temp1 = mxhosts[i]; 231 mxhosts[i] = mxhosts[j]; 232 mxhosts[j] = temp1; 233 temp = weight[i]; 234 weight[i] = weight[j]; 235 weight[j] = temp; 236 } 237 } 238 if (seenlocal && prefer[i] >= localpref) 239 { 240 /* truncate higher preference part of list */ 241 nmx = i; 242 } 243 } 244 245 if (nmx == 0) 246 { 247 punt: 248 if (seenlocal && 249 (!TryNullMXList || gethostbyname(host) == NULL)) 250 { 251 /* 252 ** If we have deleted all MX entries, this is 253 ** an error -- we should NEVER send to a host that 254 ** has an MX, and this should have been caught 255 ** earlier in the config file. 256 ** 257 ** Some sites prefer to go ahead and try the 258 ** A record anyway; that case is handled by 259 ** setting TryNullMXList. I believe this is a 260 ** bad idea, but it's up to you.... 261 */ 262 263 *rcode = EX_CONFIG; 264 return -1; 265 } 266 strcpy(MXHostBuf, host); 267 mxhosts[0] = MXHostBuf; 268 if (host[0] == '[') 269 { 270 register char *p; 271 272 /* this may be an MX suppression-style address */ 273 p = strchr(MXHostBuf, ']'); 274 if (p != NULL) 275 { 276 *p = '\0'; 277 if (inet_addr(&MXHostBuf[1]) != -1) 278 *p = ']'; 279 else 280 { 281 trycanon = TRUE; 282 mxhosts[0]++; 283 } 284 } 285 } 286 if (trycanon && 287 getcanonname(mxhosts[0], sizeof MXHostBuf - 2, FALSE)) 288 { 289 bp = &MXHostBuf[strlen(MXHostBuf)]; 290 if (bp[-1] != '.') 291 { 292 *bp++ = '.'; 293 *bp = '\0'; 294 } 295 } 296 nmx = 1; 297 } 298 299 /* if we have a default lowest preference, include that */ 300 if (fallbackMX != NULL && !seenlocal) 301 mxhosts[nmx++] = fallbackMX; 302 303 return (nmx); 304 } 305 /* 306 ** MXRAND -- create a randomizer for equal MX preferences 307 ** 308 ** If two MX hosts have equal preferences we want to randomize 309 ** the selection. But in order for signatures to be the same, 310 ** we need to randomize the same way each time. This function 311 ** computes a pseudo-random hash function from the host name. 312 ** 313 ** Parameters: 314 ** host -- the name of the host. 315 ** 316 ** Returns: 317 ** A random but repeatable value based on the host name. 318 ** 319 ** Side Effects: 320 ** none. 321 */ 322 323 mxrand(host) 324 register char *host; 325 { 326 int hfunc; 327 static unsigned int seed; 328 329 if (seed == 0) 330 { 331 seed = (int) curtime() & 0xffff; 332 if (seed == 0) 333 seed++; 334 } 335 336 if (tTd(17, 9)) 337 printf("mxrand(%s)", host); 338 339 hfunc = seed; 340 while (*host != '\0') 341 { 342 int c = *host++; 343 344 if (isascii(c) && isupper(c)) 345 c = tolower(c); 346 hfunc = ((hfunc << 1) + c) % 2003; 347 } 348 349 hfunc &= 0xff; 350 351 if (tTd(17, 9)) 352 printf(" = %d\n", hfunc); 353 return hfunc; 354 } 355 /* 356 ** GETCANONNAME -- get the canonical name for named host 357 ** 358 ** This algorithm tries to be smart about wildcard MX records. 359 ** This is hard to do because DNS doesn't tell is if we matched 360 ** against a wildcard or a specific MX. 361 ** 362 ** We always prefer A & CNAME records, since these are presumed 363 ** to be specific. 364 ** 365 ** If we match an MX in one pass and lose it in the next, we use 366 ** the old one. For example, consider an MX matching *.FOO.BAR.COM. 367 ** A hostname bletch.foo.bar.com will match against this MX, but 368 ** will stop matching when we try bletch.bar.com -- so we know 369 ** that bletch.foo.bar.com must have been right. This fails if 370 ** there was also an MX record matching *.BAR.COM, but there are 371 ** some things that just can't be fixed. 372 ** 373 ** Parameters: 374 ** host -- a buffer containing the name of the host. 375 ** This is a value-result parameter. 376 ** hbsize -- the size of the host buffer. 377 ** trymx -- if set, try MX records as well as A and CNAME. 378 ** 379 ** Returns: 380 ** TRUE -- if the host matched. 381 ** FALSE -- otherwise. 382 */ 383 384 bool 385 getcanonname(host, hbsize, trymx) 386 char *host; 387 int hbsize; 388 bool trymx; 389 { 390 extern int h_errno; 391 register u_char *eom, *ap; 392 register char *cp; 393 register int n; 394 HEADER *hp; 395 querybuf answer; 396 int ancount, qdcount; 397 int ret; 398 char **domain; 399 int type; 400 char **dp; 401 char *mxmatch; 402 bool amatch; 403 bool gotmx; 404 int qtype; 405 int loopcnt; 406 char *xp; 407 char nbuf[MAX(PACKETSZ, MAXDNAME*2+2)]; 408 char *searchlist[MAXDNSRCH+2]; 409 extern char *gethostalias(); 410 411 if (tTd(8, 2)) 412 printf("getcanonname(%s)\n", host); 413 414 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 415 return (FALSE); 416 417 /* 418 ** Initialize domain search list. If there is at least one 419 ** dot in the name, search the unmodified name first so we 420 ** find "vse.CS" in Czechoslovakia instead of in the local 421 ** domain (e.g., vse.CS.Berkeley.EDU). 422 ** 423 ** Older versions of the resolver could create this 424 ** list by tearing apart the host name. 425 */ 426 427 loopcnt = 0; 428 cnameloop: 429 for (cp = host, n = 0; *cp; cp++) 430 if (*cp == '.') 431 n++; 432 433 if (n == 0 && (xp = gethostalias(host)) != NULL) 434 { 435 if (loopcnt++ > MAXCNAMEDEPTH) 436 { 437 syserr("loop in ${HOSTALIASES} file"); 438 } 439 else 440 { 441 strncpy(host, xp, hbsize); 442 host[hbsize - 1] = '\0'; 443 goto cnameloop; 444 } 445 } 446 447 dp = searchlist; 448 if (n > 0) 449 *dp++ = ""; 450 if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options)) 451 { 452 for (domain = _res.dnsrch; *domain != NULL; ) 453 *dp++ = *domain++; 454 } 455 else if (n == 0 && bitset(RES_DEFNAMES, _res.options)) 456 { 457 *dp++ = _res.defdname; 458 } 459 *dp = NULL; 460 461 /* 462 ** Now run through the search list for the name in question. 463 */ 464 465 mxmatch = NULL; 466 qtype = T_ANY; 467 468 for (dp = searchlist; *dp != NULL; ) 469 { 470 if (qtype == T_ANY) 471 gotmx = FALSE; 472 if (tTd(8, 5)) 473 printf("getcanonname: trying %s.%s (%s)\n", host, *dp, 474 qtype == T_ANY ? "ANY" : qtype == T_A ? "A" : 475 qtype == T_MX ? "MX" : "???"); 476 ret = res_querydomain(host, *dp, C_IN, qtype, 477 &answer, sizeof(answer)); 478 if (ret <= 0) 479 { 480 if (tTd(8, 7)) 481 printf("\tNO: errno=%d, h_errno=%d\n", 482 errno, h_errno); 483 484 if (errno == ECONNREFUSED || h_errno == TRY_AGAIN) 485 { 486 /* the name server seems to be down */ 487 h_errno = TRY_AGAIN; 488 return FALSE; 489 } 490 491 if (h_errno != HOST_NOT_FOUND) 492 { 493 /* might have another type of interest */ 494 if (qtype == T_ANY) 495 { 496 qtype = T_A; 497 continue; 498 } 499 else if (qtype == T_A && !gotmx && trymx) 500 { 501 qtype = T_MX; 502 continue; 503 } 504 } 505 506 if (mxmatch != NULL) 507 { 508 /* we matched before -- use that one */ 509 break; 510 } 511 512 /* otherwise, try the next name */ 513 dp++; 514 qtype = T_ANY; 515 continue; 516 } 517 else if (tTd(8, 7)) 518 printf("\tYES\n"); 519 520 /* 521 ** This might be a bogus match. Search for A or 522 ** CNAME records. If we don't have a matching 523 ** wild card MX record, we will accept MX as well. 524 */ 525 526 hp = (HEADER *) &answer; 527 ap = (u_char *) &answer + HEADERSZ; 528 eom = (u_char *) &answer + ret; 529 530 /* skip question part of response -- we know what we asked */ 531 for (qdcount = ntohs(hp->qdcount); qdcount--; ap += ret + QFIXEDSZ) 532 { 533 if ((ret = dn_skipname(ap, eom)) < 0) 534 { 535 if (tTd(8, 20)) 536 printf("qdcount failure (%d)\n", 537 ntohs(hp->qdcount)); 538 return FALSE; /* ???XXX??? */ 539 } 540 } 541 542 amatch = FALSE; 543 for (ancount = ntohs(hp->ancount); --ancount >= 0 && ap < eom; ap += n) 544 { 545 n = dn_expand((u_char *) &answer, eom, ap, 546 (u_char *) nbuf, sizeof nbuf); 547 if (n < 0) 548 break; 549 ap += n; 550 GETSHORT(type, ap); 551 ap += SHORTSIZE + LONGSIZE; 552 GETSHORT(n, ap); 553 switch (type) 554 { 555 case T_MX: 556 gotmx = TRUE; 557 if (**dp != '\0') 558 { 559 /* got a match -- save that info */ 560 if (trymx && mxmatch == NULL) 561 mxmatch = *dp; 562 continue; 563 } 564 565 /* exact MX matches are as good as an A match */ 566 /* fall through */ 567 568 case T_A: 569 /* good show */ 570 amatch = TRUE; 571 572 /* continue in case a CNAME also exists */ 573 continue; 574 575 case T_CNAME: 576 if (loopcnt++ > MAXCNAMEDEPTH) 577 { 578 syserr("DNS failure: CNAME loop for %s", 579 host); 580 continue; 581 } 582 583 /* value points at name */ 584 if ((ret = dn_expand((u_char *)&answer, 585 eom, ap, (u_char *)nbuf, sizeof(nbuf))) < 0) 586 break; 587 (void)strncpy(host, nbuf, hbsize); /* XXX */ 588 host[hbsize - 1] = '\0'; 589 590 /* 591 ** RFC 1034 section 3.6 specifies that CNAME 592 ** should point at the canonical name -- but 593 ** urges software to try again anyway. 594 */ 595 596 goto cnameloop; 597 598 default: 599 /* not a record of interest */ 600 continue; 601 } 602 } 603 604 if (amatch) 605 { 606 /* got an A record and no CNAME */ 607 mxmatch = *dp; 608 break; 609 } 610 611 /* 612 ** If this was a T_ANY query, we may have the info but 613 ** need an explicit query. Try T_A, then T_MX. 614 */ 615 616 if (qtype == T_ANY) 617 qtype = T_A; 618 else if (qtype == T_A && !gotmx && trymx) 619 qtype = T_MX; 620 else 621 { 622 /* really nothing in this domain; try the next */ 623 qtype = T_ANY; 624 dp++; 625 } 626 } 627 628 if (mxmatch == NULL) 629 return FALSE; 630 631 /* create matching name and return */ 632 (void) sprintf(nbuf, "%.*s%s%.*s", MAXDNAME, host, 633 *mxmatch == '\0' ? "" : ".", 634 MAXDNAME, mxmatch); 635 strncpy(host, nbuf, hbsize); 636 host[hbsize - 1] = '\0'; 637 return TRUE; 638 } 639 640 641 char * 642 gethostalias(host) 643 char *host; 644 { 645 char *fname; 646 FILE *fp; 647 register char *p; 648 char buf[MAXLINE]; 649 static char hbuf[MAXDNAME]; 650 651 fname = getenv("HOSTALIASES"); 652 if (fname == NULL || (fp = fopen(fname, "r")) == NULL) 653 return NULL; 654 while (fgets(buf, sizeof buf, fp) != NULL) 655 { 656 for (p = buf; p != '\0' && !(isascii(*p) && isspace(*p)); p++) 657 continue; 658 if (*p == 0) 659 { 660 /* syntax error */ 661 continue; 662 } 663 *p++ = '\0'; 664 if (strcasecmp(buf, host) == 0) 665 break; 666 } 667 668 if (feof(fp)) 669 { 670 /* no match */ 671 fclose(fp); 672 return NULL; 673 } 674 675 /* got a match; extract the equivalent name */ 676 while (*p != '\0' && isascii(*p) && isspace(*p)) 677 p++; 678 host = p; 679 while (*p != '\0' && !(isascii(*p) && isspace(*p))) 680 p++; 681 *p = '\0'; 682 strncpy(hbuf, host, sizeof hbuf - 1); 683 hbuf[sizeof hbuf - 1] = '\0'; 684 return hbuf; 685 } 686 687 688 #else /* not NAMED_BIND */ 689 690 #include <netdb.h> 691 692 bool 693 getcanonname(host, hbsize, trymx) 694 char *host; 695 int hbsize; 696 bool trymx; 697 { 698 struct hostent *hp; 699 700 hp = gethostbyname(host); 701 if (hp == NULL) 702 return (FALSE); 703 704 if (strlen(hp->h_name) >= hbsize) 705 return (FALSE); 706 707 (void) strcpy(host, hp->h_name); 708 return (TRUE); 709 } 710 711 #endif /* not NAMED_BIND */ 712