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 8.8 (Berkeley) 09/29/93 (with name server)"; 14 #else 15 static char sccsid[] = "@(#)domain.c 8.8 (Berkeley) 09/29/93 (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 break; 136 137 case TRY_AGAIN: 138 /* couldn't connect to the name server */ 139 if (!UseNameServer && errno == ECONNREFUSED) 140 goto punt; 141 142 /* it might come up later; better queue it up */ 143 *rcode = EX_TEMPFAIL; 144 break; 145 } 146 147 /* irreconcilable differences */ 148 return (-1); 149 } 150 151 /* find first satisfactory answer */ 152 hp = (HEADER *)&answer; 153 cp = (u_char *)&answer + sizeof(HEADER); 154 eom = (u_char *)&answer + n; 155 for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ) 156 if ((n = dn_skipname(cp, eom)) < 0) 157 goto punt; 158 buflen = sizeof(MXHostBuf) - 1; 159 bp = MXHostBuf; 160 ancount = ntohs(hp->ancount); 161 while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1) 162 { 163 if ((n = dn_expand((u_char *)&answer, 164 eom, cp, (u_char *)bp, buflen)) < 0) 165 break; 166 cp += n; 167 GETSHORT(type, cp); 168 cp += SHORTSIZE + LONGSIZE; 169 GETSHORT(n, cp); 170 if (type != T_MX) 171 { 172 if (tTd(8, 8) || _res.options & RES_DEBUG) 173 printf("unexpected answer type %d, size %d\n", 174 type, n); 175 cp += n; 176 continue; 177 } 178 GETSHORT(pref, cp); 179 if ((n = dn_expand((u_char *)&answer, eom, cp, 180 (u_char *)bp, buflen)) < 0) 181 break; 182 cp += n; 183 if (droplocalhost && 184 (st = stab(bp, ST_CLASS, ST_FIND)) != NULL && 185 bitnset('w', st->s_class)) 186 { 187 if (!seenlocal || pref < localpref) 188 localpref = pref; 189 seenlocal = TRUE; 190 continue; 191 } 192 weight[nmx] = mxrand(bp); 193 prefer[nmx] = pref; 194 mxhosts[nmx++] = bp; 195 n = strlen(bp); 196 bp += n; 197 if (bp[-1] != '.') 198 { 199 *bp++ = '.'; 200 n++; 201 } 202 *bp++ = '\0'; 203 buflen -= n + 1; 204 } 205 206 /* sort the records */ 207 for (i = 0; i < nmx; i++) 208 { 209 for (j = i + 1; j < nmx; j++) 210 { 211 if (prefer[i] > prefer[j] || 212 (prefer[i] == prefer[j] && weight[i] > weight[j])) 213 { 214 register int temp; 215 register char *temp1; 216 217 temp = prefer[i]; 218 prefer[i] = prefer[j]; 219 prefer[j] = temp; 220 temp1 = mxhosts[i]; 221 mxhosts[i] = mxhosts[j]; 222 mxhosts[j] = temp1; 223 temp = weight[i]; 224 weight[i] = weight[j]; 225 weight[j] = temp; 226 } 227 } 228 if (seenlocal && prefer[i] >= localpref) 229 { 230 /* truncate higher preference part of list */ 231 nmx = i; 232 } 233 } 234 235 if (nmx == 0) 236 { 237 punt: 238 if (seenlocal && 239 (!TryNullMXList || gethostbyname(host) == NULL)) 240 { 241 /* 242 ** If we have deleted all MX entries, this is 243 ** an error -- we should NEVER send to a host that 244 ** has an MX, and this should have been caught 245 ** earlier in the config file. 246 ** 247 ** Some sites prefer to go ahead and try the 248 ** A record anyway; that case is handled by 249 ** setting TryNullMXList. I believe this is a 250 ** bad idea, but it's up to you.... 251 */ 252 253 *rcode = EX_CONFIG; 254 return -1; 255 } 256 strcpy(MXHostBuf, host); 257 mxhosts[0] = MXHostBuf; 258 if (host[0] == '[') 259 { 260 register char *p; 261 262 /* this may be an MX suppression-style address */ 263 p = strchr(MXHostBuf, ']'); 264 if (p != NULL) 265 { 266 *p = '\0'; 267 if (inet_addr(&MXHostBuf[1]) != -1) 268 *p = ']'; 269 else 270 { 271 trycanon = TRUE; 272 mxhosts[0]++; 273 } 274 } 275 } 276 if (trycanon && 277 getcanonname(mxhosts[0], sizeof MXHostBuf - 2, FALSE)) 278 { 279 bp = &MXHostBuf[strlen(MXHostBuf)]; 280 if (bp[-1] != '.') 281 { 282 *bp++ = '.'; 283 *bp = '\0'; 284 } 285 } 286 nmx = 1; 287 } 288 289 /* if we have a default lowest preference, include that */ 290 if (fallbackMX != NULL && !seenlocal) 291 mxhosts[nmx++] = fallbackMX; 292 293 return (nmx); 294 } 295 /* 296 ** MXRAND -- create a randomizer for equal MX preferences 297 ** 298 ** If two MX hosts have equal preferences we want to randomize 299 ** the selection. But in order for signatures to be the same, 300 ** we need to randomize the same way each time. This function 301 ** computes a pseudo-random hash function from the host name. 302 ** 303 ** Parameters: 304 ** host -- the name of the host. 305 ** 306 ** Returns: 307 ** A random but repeatable value based on the host name. 308 ** 309 ** Side Effects: 310 ** none. 311 */ 312 313 mxrand(host) 314 register char *host; 315 { 316 int hfunc; 317 static unsigned int seed; 318 319 if (seed == 0) 320 { 321 seed = (int) curtime() & 0xffff; 322 if (seed == 0) 323 seed++; 324 } 325 326 if (tTd(17, 9)) 327 printf("mxrand(%s)", host); 328 329 hfunc = seed; 330 while (*host != '\0') 331 { 332 int c = *host++; 333 334 if (isascii(c) && isupper(c)) 335 c = tolower(c); 336 hfunc = ((hfunc << 1) + c) % 2003; 337 } 338 339 hfunc &= 0xff; 340 341 if (tTd(17, 9)) 342 printf(" = %d\n", hfunc); 343 return hfunc; 344 } 345 /* 346 ** GETCANONNAME -- get the canonical name for named host 347 ** 348 ** This algorithm tries to be smart about wildcard MX records. 349 ** This is hard to do because DNS doesn't tell is if we matched 350 ** against a wildcard or a specific MX. 351 ** 352 ** We always prefer A & CNAME records, since these are presumed 353 ** to be specific. 354 ** 355 ** If we match an MX in one pass and lose it in the next, we use 356 ** the old one. For example, consider an MX matching *.FOO.BAR.COM. 357 ** A hostname bletch.foo.bar.com will match against this MX, but 358 ** will stop matching when we try bletch.bar.com -- so we know 359 ** that bletch.foo.bar.com must have been right. This fails if 360 ** there was also an MX record matching *.BAR.COM, but there are 361 ** some things that just can't be fixed. 362 ** 363 ** Parameters: 364 ** host -- a buffer containing the name of the host. 365 ** This is a value-result parameter. 366 ** hbsize -- the size of the host buffer. 367 ** trymx -- if set, try MX records as well as A and CNAME. 368 ** 369 ** Returns: 370 ** TRUE -- if the host matched. 371 ** FALSE -- otherwise. 372 */ 373 374 bool 375 getcanonname(host, hbsize, trymx) 376 char *host; 377 int hbsize; 378 bool trymx; 379 { 380 extern int h_errno; 381 register u_char *eom, *ap; 382 register char *cp; 383 register int n; 384 HEADER *hp; 385 querybuf answer; 386 int ancount, qdcount; 387 int ret; 388 char **domain; 389 int type; 390 char **dp; 391 char *mxmatch; 392 bool amatch; 393 bool gotmx; 394 int qtype; 395 int loopcnt; 396 char nbuf[MAX(PACKETSZ, MAXDNAME*2+2)]; 397 char *searchlist[MAXDNSRCH+2]; 398 399 if (tTd(8, 2)) 400 printf("getcanonname(%s)\n", host); 401 402 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 403 return (FALSE); 404 405 /* 406 ** Initialize domain search list. If there is at least one 407 ** dot in the name, search the unmodified name first so we 408 ** find "vse.CS" in Czechoslovakia instead of in the local 409 ** domain (e.g., vse.CS.Berkeley.EDU). 410 ** 411 ** Older versions of the resolver could create this 412 ** list by tearing apart the host name. 413 */ 414 415 loopcnt = 0; 416 cnameloop: 417 for (cp = host, n = 0; *cp; cp++) 418 if (*cp == '.') 419 n++; 420 421 dp = searchlist; 422 if (n > 0) 423 *dp++ = ""; 424 if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options)) 425 { 426 for (domain = _res.dnsrch; *domain != NULL; ) 427 *dp++ = *domain++; 428 } 429 else if (n == 0 && bitset(RES_DEFNAMES, _res.options)) 430 { 431 *dp++ = _res.defdname; 432 } 433 *dp = NULL; 434 435 /* 436 ** Now run through the search list for the name in question. 437 */ 438 439 mxmatch = NULL; 440 qtype = T_ANY; 441 442 for (dp = searchlist; *dp != NULL; ) 443 { 444 if (qtype == T_ANY) 445 gotmx = FALSE; 446 if (tTd(8, 5)) 447 printf("getcanonname: trying %s.%s (%s)\n", host, *dp, 448 qtype == T_ANY ? "ANY" : qtype == T_A ? "A" : 449 qtype == T_MX ? "MX" : "???"); 450 ret = res_querydomain(host, *dp, C_IN, qtype, 451 &answer, sizeof(answer)); 452 if (ret <= 0) 453 { 454 if (tTd(8, 7)) 455 printf("\tNO: errno=%d, h_errno=%d\n", 456 errno, h_errno); 457 458 if (errno == ECONNREFUSED || h_errno == TRY_AGAIN) 459 { 460 /* the name server seems to be down */ 461 h_errno = TRY_AGAIN; 462 return FALSE; 463 } 464 465 if (h_errno != HOST_NOT_FOUND) 466 { 467 /* might have another type of interest */ 468 if (qtype == T_ANY) 469 { 470 qtype = T_A; 471 continue; 472 } 473 else if (qtype == T_A && !gotmx && trymx) 474 { 475 qtype = T_MX; 476 continue; 477 } 478 } 479 480 if (mxmatch != NULL) 481 { 482 /* we matched before -- use that one */ 483 break; 484 } 485 486 /* otherwise, try the next name */ 487 dp++; 488 qtype = T_ANY; 489 continue; 490 } 491 else if (tTd(8, 7)) 492 printf("\tYES\n"); 493 494 /* 495 ** This might be a bogus match. Search for A or 496 ** CNAME records. If we don't have a matching 497 ** wild card MX record, we will accept MX as well. 498 */ 499 500 hp = (HEADER *) &answer; 501 ap = (u_char *) &answer + sizeof(HEADER); 502 eom = (u_char *) &answer + ret; 503 504 /* skip question part of response -- we know what we asked */ 505 for (qdcount = ntohs(hp->qdcount); qdcount--; ap += ret + QFIXEDSZ) 506 { 507 if ((ret = dn_skipname(ap, eom)) < 0) 508 { 509 if (tTd(8, 20)) 510 printf("qdcount failure (%d)\n", 511 ntohs(hp->qdcount)); 512 return FALSE; /* ???XXX??? */ 513 } 514 } 515 516 amatch = FALSE; 517 for (ancount = ntohs(hp->ancount); --ancount >= 0 && ap < eom; ap += n) 518 { 519 n = dn_expand((u_char *) &answer, eom, ap, 520 (u_char *) nbuf, sizeof nbuf); 521 if (n < 0) 522 break; 523 ap += n; 524 GETSHORT(type, ap); 525 ap += SHORTSIZE + LONGSIZE; 526 GETSHORT(n, ap); 527 switch (type) 528 { 529 case T_MX: 530 gotmx = TRUE; 531 if (**dp != '\0') 532 { 533 /* got a match -- save that info */ 534 if (trymx && mxmatch == NULL) 535 mxmatch = *dp; 536 continue; 537 } 538 539 /* exact MX matches are as good as an A match */ 540 /* fall through */ 541 542 case T_A: 543 /* good show */ 544 amatch = TRUE; 545 546 /* continue in case a CNAME also exists */ 547 continue; 548 549 case T_CNAME: 550 if (loopcnt++ > MAXCNAMEDEPTH) 551 { 552 syserr("DNS failure: CNAME loop for %s", 553 host); 554 continue; 555 } 556 557 /* value points at name */ 558 if ((ret = dn_expand((u_char *)&answer, 559 eom, ap, (u_char *)nbuf, sizeof(nbuf))) < 0) 560 break; 561 (void)strncpy(host, nbuf, hbsize); /* XXX */ 562 host[hbsize - 1] = '\0'; 563 564 /* 565 ** RFC 1034 section 3.6 specifies that CNAME 566 ** should point at the canonical name -- but 567 ** urges software to try again anyway. 568 */ 569 570 goto cnameloop; 571 572 default: 573 /* not a record of interest */ 574 continue; 575 } 576 } 577 578 if (amatch) 579 { 580 /* got an A record and no CNAME */ 581 mxmatch = *dp; 582 break; 583 } 584 585 /* 586 ** If this was a T_ANY query, we may have the info but 587 ** need an explicit query. Try T_A, then T_MX. 588 */ 589 590 if (qtype == T_ANY) 591 qtype = T_A; 592 else if (qtype == T_A && !gotmx && trymx) 593 qtype = T_MX; 594 else 595 { 596 /* really nothing in this domain; try the next */ 597 qtype = T_ANY; 598 dp++; 599 } 600 } 601 602 if (mxmatch == NULL) 603 return FALSE; 604 605 /* create matching name and return */ 606 (void) sprintf(nbuf, "%.*s%s%.*s", MAXDNAME, host, 607 *mxmatch == '\0' ? "" : ".", 608 MAXDNAME, mxmatch); 609 strncpy(host, nbuf, hbsize); 610 host[hbsize - 1] = '\0'; 611 return TRUE; 612 } 613 614 #else /* not NAMED_BIND */ 615 616 #include <netdb.h> 617 618 bool 619 getcanonname(host, hbsize, trymx) 620 char *host; 621 int hbsize; 622 bool trymx; 623 { 624 struct hostent *hp; 625 626 hp = gethostbyname(host); 627 if (hp == NULL) 628 return (FALSE); 629 630 if (strlen(hp->h_name) >= hbsize) 631 return (FALSE); 632 633 (void) strcpy(host, hp->h_name); 634 return (TRUE); 635 } 636 637 #endif /* not NAMED_BIND */ 638