contrib/sendmail-8.14/sendmail/domain.c

   1 /*
   2  * Copyright (c) 1998-2004, 2006 Sendmail, Inc. and its suppliers.
   3  *      All rights reserved.
   4  * Copyright (c) 1986, 1995-1997 Eric P. Allman.  All rights reserved.
   5  * Copyright (c) 1988, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * By using this file, you agree to the terms and conditions set
   9  * forth in the LICENSE file which can be found at the top level of
  10  * the sendmail distribution.
  11  *
  12  */
  13
  14 #include <sendmail.h>
  15 #include "map.h"
  16
  17 #if NAMED_BIND
  18 SM_RCSID("@(#)$Id: domain.c,v 8.202 2006/12/19 01:15:07 ca Exp $ (with name server)")
  19 #else /* NAMED_BIND */
  20 SM_RCSID("@(#)$Id: domain.c,v 8.202 2006/12/19 01:15:07 ca Exp $ (without name server)")
  21 #endif /* NAMED_BIND */
  22
  23 #if NAMED_BIND
  24
  25 # include <arpa/inet.h>
  26
  27
  28 /*
  29 **  The standard udp packet size PACKETSZ (512) is not sufficient for some
  30 **  nameserver answers containing very many resource records. The resolver
  31 **  may switch to tcp and retry if it detects udp packet overflow.
  32 **  Also note that the resolver routines res_query and res_search return
  33 **  the size of the *un*truncated answer in case the supplied answer buffer
  34 **  it not big enough to accommodate the entire answer.
  35 */
  36
  37 # ifndef MAXPACKET
  38 #  define MAXPACKET 8192        /* max packet size used internally by BIND */
  39 # endif /* ! MAXPACKET */
  40
  41 typedef union
  42 {
  43         HEADER          qb1;
  44         unsigned char   qb2[MAXPACKET];
  45 } querybuf;
  46
  47 # ifndef MXHOSTBUFSIZE
  48 #  define MXHOSTBUFSIZE (128 * MAXMXHOSTS)
  49 # endif /* ! MXHOSTBUFSIZE */
  50
  51 static char     MXHostBuf[MXHOSTBUFSIZE];
  52 #if (MXHOSTBUFSIZE < 2) || (MXHOSTBUFSIZE >= INT_MAX/2)
  53         ERROR: _MXHOSTBUFSIZE is out of range
  54 #endif /* (MXHOSTBUFSIZE < 2) || (MXHOSTBUFSIZE >= INT_MAX/2) */
  55
  56 # ifndef MAXDNSRCH
  57 #  define MAXDNSRCH     6       /* number of possible domains to search */
  58 # endif /* ! MAXDNSRCH */
  59
  60 # ifndef RES_DNSRCH_VARIABLE
  61 #  define RES_DNSRCH_VARIABLE   _res.dnsrch
  62 # endif /* ! RES_DNSRCH_VARIABLE */
  63
  64 # ifndef NO_DATA
  65 #  define NO_DATA       NO_ADDRESS
  66 # endif /* ! NO_DATA */
  67
  68 # ifndef HFIXEDSZ
  69 #  define HFIXEDSZ      12      /* sizeof(HEADER) */
  70 # endif /* ! HFIXEDSZ */
  71
  72 # define MAXCNAMEDEPTH  10      /* maximum depth of CNAME recursion */
  73
  74 # if defined(__RES) && (__RES >= 19940415)
  75 #  define RES_UNC_T     char *
  76 # else /* defined(__RES) && (__RES >= 19940415) */
  77 #  define RES_UNC_T     unsigned char *
  78 # endif /* defined(__RES) && (__RES >= 19940415) */
  79
  80 static int      mxrand __P((char *));
  81 static int      fallbackmxrr __P((int, unsigned short *, char **));
  82
  83 /*
  84 **  GETFALLBACKMXRR -- get MX resource records for fallback MX host.
  85 **
  86 **      We have to initialize this once before doing anything else.
  87 **      Moreover, we have to repeat this from time to time to avoid
  88 **      stale data, e.g., in persistent queue runners.
  89 **      This should be done in a parent process so the child
  90 **      processes have the right data.
  91 **
  92 **      Parameters:
  93 **              host -- the name of the fallback MX host.
  94 **
  95 **      Returns:
  96 **              number of MX records.
  97 **
  98 **      Side Effects:
  99 **              Populates NumFallbackMXHosts and fbhosts.
 100 **              Sets renewal time (based on TTL).
 101 */
 102
 103 int NumFallbackMXHosts = 0;     /* Number of fallback MX hosts (after MX expansion) */
 104 static char *fbhosts[MAXMXHOSTS + 1];
 105
 106 int
 107 getfallbackmxrr(host)
 108         char *host;
 109 {
 110         int i, rcode;
 111         int ttl;
 112         static time_t renew = 0;
 113
 114 #if 0
 115         /* This is currently done before this function is called. */
 116         if (host == NULL || *host == '\0')
 117                 return 0;
 118 #endif /* 0 */
 119         if (NumFallbackMXHosts > 0 && renew > curtime())
 120                 return NumFallbackMXHosts;
 121         if (host[0] == '[')
 122         {
 123                 fbhosts[0] = host;
 124                 NumFallbackMXHosts = 1;
 125         }
 126         else
 127         {
 128                 /* free old data */
 129                 for (i = 0; i < NumFallbackMXHosts; i++)
 130                         sm_free(fbhosts[i]);
 131
 132                 /* get new data */
 133                 NumFallbackMXHosts = getmxrr(host, fbhosts, NULL, false,
 134                                              &rcode, false, &ttl);
 135                 renew = curtime() + ttl;
 136                 for (i = 0; i < NumFallbackMXHosts; i++)
 137                         fbhosts[i] = newstr(fbhosts[i]);
 138         }
 139         return NumFallbackMXHosts;
 140 }
 141
 142 /*
 143 **  FALLBACKMXRR -- add MX resource records for fallback MX host to list.
 144 **
 145 **      Parameters:
 146 **              nmx -- current number of MX records.
 147 **              prefs -- array of preferences.
 148 **              mxhosts -- array of MX hosts (maximum size: MAXMXHOSTS)
 149 **
 150 **      Returns:
 151 **              new number of MX records.
 152 **
 153 **      Side Effects:
 154 **              If FallbackMX was set, it appends the MX records for
 155 **              that host to mxhosts (and modifies prefs accordingly).
 156 */
 157
 158 static int
 159 fallbackmxrr(nmx, prefs, mxhosts)
 160         int nmx;
 161         unsigned short *prefs;
 162         char **mxhosts;
 163 {
 164         int i;
 165
 166         for (i = 0; i < NumFallbackMXHosts && nmx < MAXMXHOSTS; i++)
 167         {
 168                 if (nmx > 0)
 169                         prefs[nmx] = prefs[nmx - 1] + 1;
 170                 else
 171                         prefs[nmx] = 0;
 172                 mxhosts[nmx++] = fbhosts[i];
 173         }
 174         return nmx;
 175 }
 176
 177 /*
 178 **  GETMXRR -- get MX resource records for a domain
 179 **
 180 **      Parameters:
 181 **              host -- the name of the host to MX.
 182 **              mxhosts -- a pointer to a return buffer of MX records.
 183 **              mxprefs -- a pointer to a return buffer of MX preferences.
 184 **                      If NULL, don't try to populate.
 185 **              droplocalhost -- If true, all MX records less preferred
 186 **                      than the local host (as determined by $=w) will
 187 **                      be discarded.
 188 **              rcode -- a pointer to an EX_ status code.
 189 **              tryfallback -- add also fallback MX host?
 190 **              pttl -- pointer to return TTL (can be NULL).
 191 **
 192 **      Returns:
 193 **              The number of MX records found.
 194 **              -1 if there is an internal failure.
 195 **              If no MX records are found, mxhosts[0] is set to host
 196 **                      and 1 is returned.
 197 **
 198 **      Side Effects:
 199 **              The entries made for mxhosts point to a static array
 200 **              MXHostBuf[MXHOSTBUFSIZE], so the data needs to be copied,
 201 **              if it must be preserved across calls to this function.
 202 */
 203
 204 int
 205 getmxrr(host, mxhosts, mxprefs, droplocalhost, rcode, tryfallback, pttl)
 206         char *host;
 207         char **mxhosts;
 208         unsigned short *mxprefs;
 209         bool droplocalhost;
 210         int *rcode;
 211         bool tryfallback;
 212         int *pttl;
 213 {
 214         register unsigned char *eom, *cp;
 215         register int i, j, n;
 216         int nmx = 0;
 217         register char *bp;
 218         HEADER *hp;
 219         querybuf answer;
 220         int ancount, qdcount, buflen;
 221         bool seenlocal = false;
 222         unsigned short pref, type;
 223         unsigned short localpref = 256;
 224         char *fallbackMX = FallbackMX;
 225         bool trycanon = false;
 226         unsigned short *prefs;
 227         int (*resfunc) __P((const char *, int, int, u_char *, int));
 228         unsigned short prefer[MAXMXHOSTS];
 229         int weight[MAXMXHOSTS];
 230         int ttl = 0;
 231         extern int res_query(), res_search();
 232
 233         if (tTd(8, 2))
 234                 sm_dprintf("getmxrr(%s, droplocalhost=%d)\n",
 235                            host, droplocalhost);
 236         *rcode = EX_OK;
 237         if (pttl != NULL)
 238                 *pttl = SM_DEFAULT_TTL;
 239         if (*host == '\0')
 240                 return 0;
 241
 242         if ((fallbackMX != NULL && droplocalhost &&
 243              wordinclass(fallbackMX, 'w')) || !tryfallback)
 244         {
 245                 /* don't use fallback for this pass */
 246                 fallbackMX = NULL;
 247         }
 248
 249         if (mxprefs != NULL)
 250                 prefs = mxprefs;
 251         else
 252                 prefs = prefer;
 253
 254         /* efficiency hack -- numeric or non-MX lookups */
 255         if (host[0] == '[')
 256                 goto punt;
 257
 258         /*
 259         **  If we don't have MX records in our host switch, don't
 260         **  try for MX records.  Note that this really isn't "right",
 261         **  since we might be set up to try NIS first and then DNS;
 262         **  if the host is found in NIS we really shouldn't be doing
 263         **  MX lookups.  However, that should be a degenerate case.
 264         */
 265
 266         if (!UseNameServer)
 267                 goto punt;
 268         if (HasWildcardMX && ConfigLevel >= 6)
 269                 resfunc = res_query;
 270         else
 271                 resfunc = res_search;
 272
 273         errno = 0;
 274         n = (*resfunc)(host, C_IN, T_MX, (unsigned char *) &answer,
 275                        sizeof(answer));
 276         if (n < 0)
 277         {
 278                 if (tTd(8, 1))
 279                         sm_dprintf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n",
 280                                 host, errno, h_errno);
 281                 switch (h_errno)
 282                 {
 283                   case NO_DATA:
 284                         trycanon = true;
 285                         /* FALLTHROUGH */
 286
 287                   case NO_RECOVERY:
 288                         /* no MX data on this host */
 289                         goto punt;
 290
 291                   case HOST_NOT_FOUND:
 292 # if BROKEN_RES_SEARCH
 293                   case 0:       /* Ultrix resolver retns failure w/ h_errno=0 */
 294 # endif /* BROKEN_RES_SEARCH */
 295                         /* host doesn't exist in DNS; might be in /etc/hosts */
 296                         trycanon = true;
 297                         *rcode = EX_NOHOST;
 298                         goto punt;
 299
 300                   case TRY_AGAIN:
 301                   case -1:
 302                         /* couldn't connect to the name server */
 303                         if (fallbackMX != NULL)
 304                         {
 305                                 /* name server is hosed -- push to fallback */
 306                                 return fallbackmxrr(nmx, prefs, mxhosts);
 307                         }
 308                         /* it might come up later; better queue it up */
 309                         *rcode = EX_TEMPFAIL;
 310                         break;
 311
 312                   default:
 313                         syserr("getmxrr: res_search (%s) failed with impossible h_errno (%d)",
 314                                 host, h_errno);
 315                         *rcode = EX_OSERR;
 316                         break;
 317                 }
 318
 319                 /* irreconcilable differences */
 320                 return -1;
 321         }
 322
 323         /* avoid problems after truncation in tcp packets */
 324         if (n > sizeof(answer))
 325                 n = sizeof(answer);
 326
 327         /* find first satisfactory answer */
 328         hp = (HEADER *)&answer;
 329         cp = (unsigned char *)&answer + HFIXEDSZ;
 330         eom = (unsigned char *)&answer + n;
 331         for (qdcount = ntohs((unsigned short) hp->qdcount);
 332              qdcount--;
 333              cp += n + QFIXEDSZ)
 334         {
 335                 if ((n = dn_skipname(cp, eom)) < 0)
 336                         goto punt;
 337         }
 338
 339         /* NOTE: see definition of MXHostBuf! */
 340         buflen = sizeof(MXHostBuf) - 1;
 341         SM_ASSERT(buflen > 0);
 342         bp = MXHostBuf;
 343         ancount = ntohs((unsigned short) hp->ancount);
 344
 345         /* See RFC 1035 for layout of RRs. */
 346         /* XXX leave room for FallbackMX ? */
 347         while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1)
 348         {
 349                 if ((n = dn_expand((unsigned char *)&answer, eom, cp,
 350                                    (RES_UNC_T) bp, buflen)) < 0)
 351                         break;
 352                 cp += n;
 353                 GETSHORT(type, cp);
 354                 cp += INT16SZ;          /* skip over class */
 355                 GETLONG(ttl, cp);
 356                 GETSHORT(n, cp);        /* rdlength */
 357                 if (type != T_MX)
 358                 {
 359                         if (tTd(8, 8) || _res.options & RES_DEBUG)
 360                                 sm_dprintf("unexpected answer type %d, size %d\n",
 361                                         type, n);
 362                         cp += n;
 363                         continue;
 364                 }
 365                 GETSHORT(pref, cp);
 366                 if ((n = dn_expand((unsigned char *)&answer, eom, cp,
 367                                    (RES_UNC_T) bp, buflen)) < 0)
 368                         break;
 369                 cp += n;
 370                 n = strlen(bp);
 371 # if 0
 372                 /* Can this happen? */
 373                 if (n == 0)
 374                 {
 375                         if (LogLevel > 4)
 376                                 sm_syslog(LOG_ERR, NOQID,
 377                                           "MX records for %s contain empty string",
 378                                           host);
 379                         continue;
 380                 }
 381 # endif /* 0 */
 382                 if (wordinclass(bp, 'w'))
 383                 {
 384                         if (tTd(8, 3))
 385                                 sm_dprintf("found localhost (%s) in MX list, pref=%d\n",
 386                                         bp, pref);
 387                         if (droplocalhost)
 388                         {
 389                                 if (!seenlocal || pref < localpref)
 390                                         localpref = pref;
 391                                 seenlocal = true;
 392                                 continue;
 393                         }
 394                         weight[nmx] = 0;
 395                 }
 396                 else
 397                         weight[nmx] = mxrand(bp);
 398                 prefs[nmx] = pref;
 399                 mxhosts[nmx++] = bp;
 400                 bp += n;
 401                 if (bp[-1] != '.')
 402                 {
 403                         *bp++ = '.';
 404                         n++;
 405                 }
 406                 *bp++ = '\0';
 407                 if (buflen < n + 1)
 408                 {
 409                         /* don't want to wrap buflen */
 410                         break;
 411                 }
 412                 buflen -= n + 1;
 413         }
 414
 415         /* return only one TTL entry, that should be sufficient */
 416         if (ttl > 0 && pttl != NULL)
 417                 *pttl = ttl;
 418
 419         /* sort the records */
 420         for (i = 0; i < nmx; i++)
 421         {
 422                 for (j = i + 1; j < nmx; j++)
 423                 {
 424                         if (prefs[i] > prefs[j] ||
 425                             (prefs[i] == prefs[j] && weight[i] > weight[j]))
 426                         {
 427                                 register int temp;
 428                                 register char *temp1;
 429
 430                                 temp = prefs[i];
 431                                 prefs[i] = prefs[j];
 432                                 prefs[j] = temp;
 433                                 temp1 = mxhosts[i];
 434                                 mxhosts[i] = mxhosts[j];
 435                                 mxhosts[j] = temp1;
 436                                 temp = weight[i];
 437                                 weight[i] = weight[j];
 438                                 weight[j] = temp;
 439                         }
 440                 }
 441                 if (seenlocal && prefs[i] >= localpref)
 442                 {
 443                         /* truncate higher preference part of list */
 444                         nmx = i;
 445                 }
 446         }
 447
 448         /* delete duplicates from list (yes, some bozos have duplicates) */
 449         for (i = 0; i < nmx - 1; )
 450         {
 451                 if (sm_strcasecmp(mxhosts[i], mxhosts[i + 1]) != 0)
 452                         i++;
 453                 else
 454                 {
 455                         /* compress out duplicate */
 456                         for (j = i + 1; j < nmx; j++)
 457                         {
 458                                 mxhosts[j] = mxhosts[j + 1];
 459                                 prefs[j] = prefs[j + 1];
 460                         }
 461                         nmx--;
 462                 }
 463         }
 464
 465         if (nmx == 0)
 466         {
 467 punt:
 468                 if (seenlocal)
 469                 {
 470                         struct hostent *h = NULL;
 471
 472                         /*
 473                         **  If we have deleted all MX entries, this is
 474                         **  an error -- we should NEVER send to a host that
 475                         **  has an MX, and this should have been caught
 476                         **  earlier in the config file.
 477                         **
 478                         **  Some sites prefer to go ahead and try the
 479                         **  A record anyway; that case is handled by
 480                         **  setting TryNullMXList.  I believe this is a
 481                         **  bad idea, but it's up to you....
 482                         */
 483
 484                         if (TryNullMXList)
 485                         {
 486                                 SM_SET_H_ERRNO(0);
 487                                 errno = 0;
 488                                 h = sm_gethostbyname(host, AF_INET);
 489                                 if (h == NULL)
 490                                 {
 491                                         if (errno == ETIMEDOUT ||
 492                                             h_errno == TRY_AGAIN ||
 493                                             (errno == ECONNREFUSED &&
 494                                              UseNameServer))
 495                                         {
 496                                                 *rcode = EX_TEMPFAIL;
 497                                                 return -1;
 498                                         }
 499 # if NETINET6
 500                                         SM_SET_H_ERRNO(0);
 501                                         errno = 0;
 502                                         h = sm_gethostbyname(host, AF_INET6);
 503                                         if (h == NULL &&
 504                                             (errno == ETIMEDOUT ||
 505                                              h_errno == TRY_AGAIN ||
 506                                              (errno == ECONNREFUSED &&
 507                                               UseNameServer)))
 508                                         {
 509                                                 *rcode = EX_TEMPFAIL;
 510                                                 return -1;
 511                                         }
 512 # endif /* NETINET6 */
 513                                 }
 514                         }
 515
 516                         if (h == NULL)
 517                         {
 518                                 *rcode = EX_CONFIG;
 519                                 syserr("MX list for %s points back to %s",
 520                                        host, MyHostName);
 521                                 return -1;
 522                         }
 523 # if NETINET6
 524                         freehostent(h);
 525                         h = NULL;
 526 # endif /* NETINET6 */
 527                 }
 528                 if (strlen(host) >= sizeof(MXHostBuf))
 529                 {
 530                         *rcode = EX_CONFIG;
 531                         syserr("Host name %s too long",
 532                                shortenstring(host, MAXSHORTSTR));
 533                         return -1;
 534                 }
 535                 (void) sm_strlcpy(MXHostBuf, host, sizeof(MXHostBuf));
 536                 mxhosts[0] = MXHostBuf;
 537                 prefs[0] = 0;
 538                 if (host[0] == '[')
 539                 {
 540                         register char *p;
 541 # if NETINET6
 542                         struct sockaddr_in6 tmp6;
 543 # endif /* NETINET6 */
 544
 545                         /* this may be an MX suppression-style address */
 546                         p = strchr(MXHostBuf, ']');
 547                         if (p != NULL)
 548                         {
 549                                 *p = '\0';
 550
 551                                 if (inet_addr(&MXHostBuf[1]) != INADDR_NONE)
 552                                 {
 553                                         nmx++;
 554                                         *p = ']';
 555                                 }
 556 # if NETINET6
 557                                 else if (anynet_pton(AF_INET6, &MXHostBuf[1],
 558                                                      &tmp6.sin6_addr) == 1)
 559                                 {
 560                                         nmx++;
 561                                         *p = ']';
 562                                 }
 563 # endif /* NETINET6 */
 564                                 else
 565                                 {
 566                                         trycanon = true;
 567                                         mxhosts[0]++;
 568                                 }
 569                         }
 570                 }
 571                 if (trycanon &&
 572                     getcanonname(mxhosts[0], sizeof(MXHostBuf) - 2, false, pttl))
 573                 {
 574                         /* XXX MXHostBuf == "" ?  is that possible? */
 575                         bp = &MXHostBuf[strlen(MXHostBuf)];
 576                         if (bp[-1] != '.')
 577                         {
 578                                 *bp++ = '.';
 579                                 *bp = '\0';
 580                         }
 581                         nmx = 1;
 582                 }
 583         }
 584
 585         /* if we have a default lowest preference, include that */
 586         if (fallbackMX != NULL && !seenlocal)
 587         {
 588                 nmx = fallbackmxrr(nmx, prefs, mxhosts);
 589         }
 590         return nmx;
 591 }
 592 /*
 593 **  MXRAND -- create a randomizer for equal MX preferences
 594 **
 595 **      If two MX hosts have equal preferences we want to randomize
 596 **      the selection.  But in order for signatures to be the same,
 597 **      we need to randomize the same way each time.  This function
 598 **      computes a pseudo-random hash function from the host name.
 599 **
 600 **      Parameters:
 601 **              host -- the name of the host.
 602 **
 603 **      Returns:
 604 **              A random but repeatable value based on the host name.
 605 */
 606
 607 static int
 608 mxrand(host)
 609         register char *host;
 610 {
 611         int hfunc;
 612         static unsigned int seed;
 613
 614         if (seed == 0)
 615         {
 616                 seed = (int) curtime() & 0xffff;
 617                 if (seed == 0)
 618                         seed++;
 619         }
 620
 621         if (tTd(17, 9))
 622                 sm_dprintf("mxrand(%s)", host);
 623
 624         hfunc = seed;
 625         while (*host != '\0')
 626         {
 627                 int c = *host++;
 628
 629                 if (isascii(c) && isupper(c))
 630                         c = tolower(c);
 631                 hfunc = ((hfunc << 1) ^ c) % 2003;
 632         }
 633
 634         hfunc &= 0xff;
 635         hfunc++;
 636
 637         if (tTd(17, 9))
 638                 sm_dprintf(" = %d\n", hfunc);
 639         return hfunc;
 640 }
 641 /*
 642 **  BESTMX -- find the best MX for a name
 643 **
 644 **      This is really a hack, but I don't see any obvious way
 645 **      to generalize it at the moment.
 646 */
 647
 648 /* ARGSUSED3 */
 649 char *
 650 bestmx_map_lookup(map, name, av, statp)
 651         MAP *map;
 652         char *name;
 653         char **av;
 654         int *statp;
 655 {
 656         int nmx;
 657         int saveopts = _res.options;
 658         int i;
 659         ssize_t len = 0;
 660         char *result;
 661         char *mxhosts[MAXMXHOSTS + 1];
 662 #if _FFR_BESTMX_BETTER_TRUNCATION
 663         char *buf;
 664 #else /* _FFR_BESTMX_BETTER_TRUNCATION */
 665         char *p;
 666         char buf[PSBUFSIZE / 2];
 667 #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
 668
 669         _res.options &= ~(RES_DNSRCH|RES_DEFNAMES);
 670         nmx = getmxrr(name, mxhosts, NULL, false, statp, false, NULL);
 671         _res.options = saveopts;
 672         if (nmx <= 0)
 673                 return NULL;
 674         if (bitset(MF_MATCHONLY, map->map_mflags))
 675                 return map_rewrite(map, name, strlen(name), NULL);
 676         if ((map->map_coldelim == '\0') || (nmx == 1))
 677                 return map_rewrite(map, mxhosts[0], strlen(mxhosts[0]), av);
 678
 679         /*
 680         **  We were given a -z flag (return all MXs) and there are multiple
 681         **  ones.  We need to build them all into a list.
 682         */
 683
 684 #if _FFR_BESTMX_BETTER_TRUNCATION
 685         for (i = 0; i < nmx; i++)
 686         {
 687                 if (strchr(mxhosts[i], map->map_coldelim) != NULL)
 688                 {
 689                         syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
 690                                mxhosts[i], map->map_coldelim);
 691                         return NULL;
 692                 }
 693                 len += strlen(mxhosts[i]) + 1;
 694                 if (len < 0)
 695                 {
 696                         len -= strlen(mxhosts[i]) + 1;
 697                         break;
 698                 }
 699         }
 700         buf = (char *) sm_malloc(len);
 701         if (buf == NULL)
 702         {
 703                 *statp = EX_UNAVAILABLE;
 704                 return NULL;
 705         }
 706         *buf = '\0';
 707         for (i = 0; i < nmx; i++)
 708         {
 709                 int end;
 710
 711                 end = sm_strlcat(buf, mxhosts[i], len);
 712                 if (i != nmx && end + 1 < len)
 713                 {
 714                         buf[end] = map->map_coldelim;
 715                         buf[end + 1] = '\0';
 716                 }
 717         }
 718
 719         /* Cleanly truncate for rulesets */
 720         truncate_at_delim(buf, PSBUFSIZE / 2, map->map_coldelim);
 721 #else /* _FFR_BESTMX_BETTER_TRUNCATION */
 722         p = buf;
 723         for (i = 0; i < nmx; i++)
 724         {
 725                 size_t slen;
 726
 727                 if (strchr(mxhosts[i], map->map_coldelim) != NULL)
 728                 {
 729                         syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
 730                                mxhosts[i], map->map_coldelim);
 731                         return NULL;
 732                 }
 733                 slen = strlen(mxhosts[i]);
 734                 if (len + slen + 2 > sizeof(buf))
 735                         break;
 736                 if (i > 0)
 737                 {
 738                         *p++ = map->map_coldelim;
 739                         len++;
 740                 }
 741                 (void) sm_strlcpy(p, mxhosts[i], sizeof(buf) - len);
 742                 p += slen;
 743                 len += slen;
 744         }
 745 #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
 746
 747         result = map_rewrite(map, buf, len, av);
 748 #if _FFR_BESTMX_BETTER_TRUNCATION
 749         sm_free(buf);
 750 #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
 751         return result;
 752 }
 753 /*
 754 **  DNS_GETCANONNAME -- get the canonical name for named host using DNS
 755 **
 756 **      This algorithm tries to be smart about wildcard MX records.
 757 **      This is hard to do because DNS doesn't tell is if we matched
 758 **      against a wildcard or a specific MX.
 759 **
 760 **      We always prefer A & CNAME records, since these are presumed
 761 **      to be specific.
 762 **
 763 **      If we match an MX in one pass and lose it in the next, we use
 764 **      the old one.  For example, consider an MX matching *.FOO.BAR.COM.
 765 **      A hostname bletch.foo.bar.com will match against this MX, but
 766 **      will stop matching when we try bletch.bar.com -- so we know
 767 **      that bletch.foo.bar.com must have been right.  This fails if
 768 **      there was also an MX record matching *.BAR.COM, but there are
 769 **      some things that just can't be fixed.
 770 **
 771 **      Parameters:
 772 **              host -- a buffer containing the name of the host.
 773 **                      This is a value-result parameter.
 774 **              hbsize -- the size of the host buffer.
 775 **              trymx -- if set, try MX records as well as A and CNAME.
 776 **              statp -- pointer to place to store status.
 777 **              pttl -- pointer to return TTL (can be NULL).
 778 **
 779 **      Returns:
 780 **              true -- if the host matched.
 781 **              false -- otherwise.
 782 */
 783
 784 bool
 785 dns_getcanonname(host, hbsize, trymx, statp, pttl)
 786         char *host;
 787         int hbsize;
 788         bool trymx;
 789         int *statp;
 790         int *pttl;
 791 {
 792         register unsigned char *eom, *ap;
 793         register char *cp;
 794         register int n;
 795         HEADER *hp;
 796         querybuf answer;
 797         int ancount, qdcount;
 798         int ret;
 799         char **domain;
 800         int type;
 801         int ttl = 0;
 802         char **dp;
 803         char *mxmatch;
 804         bool amatch;
 805         bool gotmx = false;
 806         int qtype;
 807         int initial;
 808         int loopcnt;
 809         char nbuf[SM_MAX(MAXPACKET, MAXDNAME*2+2)];
 810         char *searchlist[MAXDNSRCH + 2];
 811
 812         if (tTd(8, 2))
 813                 sm_dprintf("dns_getcanonname(%s, trymx=%d)\n", host, trymx);
 814
 815         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
 816         {
 817                 *statp = EX_UNAVAILABLE;
 818                 return false;
 819         }
 820
 821         *statp = EX_OK;
 822
 823         /*
 824         **  Initialize domain search list.  If there is at least one
 825         **  dot in the name, search the unmodified name first so we
 826         **  find "vse.CS" in Czechoslovakia instead of in the local
 827         **  domain (e.g., vse.CS.Berkeley.EDU).  Note that there is no
 828         **  longer a country named Czechoslovakia but this type of problem
 829         **  is still present.
 830         **
 831         **  Older versions of the resolver could create this
 832         **  list by tearing apart the host name.
 833         */
 834
 835         loopcnt = 0;
 836 cnameloop:
 837         /* Check for dots in the name */
 838         for (cp = host, n = 0; *cp != '\0'; cp++)
 839                 if (*cp == '.')
 840                         n++;
 841
 842         /*
 843         **  Build the search list.
 844         **      If there is at least one dot in name, start with a null
 845         **      domain to search the unmodified name first.
 846         **      If name does not end with a dot and search up local domain
 847         **      tree desired, append each local domain component to the
 848         **      search list; if name contains no dots and default domain
 849         **      name is desired, append default domain name to search list;
 850         **      else if name ends in a dot, remove that dot.
 851         */
 852
 853         dp = searchlist;
 854         if (n > 0)
 855                 *dp++ = "";
 856         if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options))
 857         {
 858                 /* make sure there are less than MAXDNSRCH domains */
 859                 for (domain = RES_DNSRCH_VARIABLE, ret = 0;
 860                      *domain != NULL && ret < MAXDNSRCH;
 861                      ret++)
 862                         *dp++ = *domain++;
 863         }
 864         else if (n == 0 && bitset(RES_DEFNAMES, _res.options))
 865         {
 866                 *dp++ = _res.defdname;
 867         }
 868         else if (*cp == '.')
 869         {
 870                 *cp = '\0';
 871         }
 872         *dp = NULL;
 873
 874         /*
 875         **  Now loop through the search list, appending each domain in turn
 876         **  name and searching for a match.
 877         */
 878
 879         mxmatch = NULL;
 880         initial = T_A;
 881 # if NETINET6
 882         if (InetMode == AF_INET6)
 883                 initial = T_AAAA;
 884 # endif /* NETINET6 */
 885         qtype = initial;
 886
 887         for (dp = searchlist; *dp != NULL; )
 888         {
 889                 if (qtype == initial)
 890                         gotmx = false;
 891                 if (tTd(8, 5))
 892                         sm_dprintf("dns_getcanonname: trying %s.%s (%s)\n",
 893                                 host, *dp,
 894 # if NETINET6
 895                                 qtype == T_AAAA ? "AAAA" :
 896 # endif /* NETINET6 */
 897                                 qtype == T_A ? "A" :
 898                                 qtype == T_MX ? "MX" :
 899                                 "???");
 900                 errno = 0;
 901                 ret = res_querydomain(host, *dp, C_IN, qtype,
 902                                       answer.qb2, sizeof(answer.qb2));
 903                 if (ret <= 0)
 904                 {
 905                         int save_errno = errno;
 906
 907                         if (tTd(8, 7))
 908                                 sm_dprintf("\tNO: errno=%d, h_errno=%d\n",
 909                                            save_errno, h_errno);
 910
 911                         if (save_errno == ECONNREFUSED || h_errno == TRY_AGAIN)
 912                         {
 913                                 /*
 914                                 **  the name server seems to be down or broken.
 915                                 */
 916
 917                                 SM_SET_H_ERRNO(TRY_AGAIN);
 918                                 if (**dp == '\0')
 919                                 {
 920                                         if (*statp == EX_OK)
 921                                                 *statp = EX_TEMPFAIL;
 922                                         goto nexttype;
 923                                 }
 924                                 *statp = EX_TEMPFAIL;
 925
 926                                 if (WorkAroundBrokenAAAA)
 927                                 {
 928                                         /*
 929                                         **  Only return if not TRY_AGAIN as an
 930                                         **  attempt with a different qtype may
 931                                         **  succeed (res_querydomain() calls
 932                                         **  res_query() calls res_send() which
 933                                         **  sets errno to ETIMEDOUT if the
 934                                         **  nameservers could be contacted but
 935                                         **  didn't give an answer).
 936                                         */
 937
 938                                         if (save_errno != ETIMEDOUT)
 939                                                 return false;
 940                                 }
 941                                 else
 942                                         return false;
 943                         }
 944
 945 nexttype:
 946                         if (h_errno != HOST_NOT_FOUND)
 947                         {
 948                                 /* might have another type of interest */
 949 # if NETINET6
 950                                 if (qtype == T_AAAA)
 951                                 {
 952                                         qtype = T_A;
 953                                         continue;
 954                                 }
 955                                 else
 956 # endif /* NETINET6 */
 957                                 if (qtype == T_A && !gotmx &&
 958                                     (trymx || **dp == '\0'))
 959                                 {
 960                                         qtype = T_MX;
 961                                         continue;
 962                                 }
 963                         }
 964
 965                         /* definite no -- try the next domain */
 966                         dp++;
 967                         qtype = initial;
 968                         continue;
 969                 }
 970                 else if (tTd(8, 7))
 971                         sm_dprintf("\tYES\n");
 972
 973                 /* avoid problems after truncation in tcp packets */
 974                 if (ret > sizeof(answer))
 975                         ret = sizeof(answer);
 976                 SM_ASSERT(ret >= 0);
 977
 978                 /*
 979                 **  Appear to have a match.  Confirm it by searching for A or
 980                 **  CNAME records.  If we don't have a local domain
 981                 **  wild card MX record, we will accept MX as well.
 982                 */
 983
 984                 hp = (HEADER *) &answer;
 985                 ap = (unsigned char *) &answer + HFIXEDSZ;
 986                 eom = (unsigned char *) &answer + ret;
 987
 988                 /* skip question part of response -- we know what we asked */
 989                 for (qdcount = ntohs((unsigned short) hp->qdcount);
 990                      qdcount--;
 991                      ap += ret + QFIXEDSZ)
 992                 {
 993                         if ((ret = dn_skipname(ap, eom)) < 0)
 994                         {
 995                                 if (tTd(8, 20))
 996                                         sm_dprintf("qdcount failure (%d)\n",
 997                                                 ntohs((unsigned short) hp->qdcount));
 998                                 *statp = EX_SOFTWARE;
 999                                 return false;           /* ???XXX??? */
1000                         }
1001                 }
1002
1003                 amatch = false;
1004                 for (ancount = ntohs((unsigned short) hp->ancount);
1005                      --ancount >= 0 && ap < eom;
1006                      ap += n)
1007                 {
1008                         n = dn_expand((unsigned char *) &answer, eom, ap,
1009                                       (RES_UNC_T) nbuf, sizeof(nbuf));
1010                         if (n < 0)
1011                                 break;
1012                         ap += n;
1013                         GETSHORT(type, ap);
1014                         ap += INT16SZ;          /* skip over class */
1015                         GETLONG(ttl, ap);
1016                         GETSHORT(n, ap);        /* rdlength */
1017                         switch (type)
1018                         {
1019                           case T_MX:
1020                                 gotmx = true;
1021                                 if (**dp != '\0' && HasWildcardMX)
1022                                 {
1023                                         /*
1024                                         **  If we are using MX matches and have
1025                                         **  not yet gotten one, save this one
1026                                         **  but keep searching for an A or
1027                                         **  CNAME match.
1028                                         */
1029
1030                                         if (trymx && mxmatch == NULL)
1031                                                 mxmatch = *dp;
1032                                         continue;
1033                                 }
1034
1035                                 /*
1036                                 **  If we did not append a domain name, this
1037                                 **  must have been a canonical name to start
1038                                 **  with.  Even if we did append a domain name,
1039                                 **  in the absence of a wildcard MX this must
1040                                 **  still be a real MX match.
1041                                 **  Such MX matches are as good as an A match,
1042                                 **  fall through.
1043                                 */
1044                                 /* FALLTHROUGH */
1045
1046 # if NETINET6
1047                           case T_AAAA:
1048 # endif /* NETINET6 */
1049                           case T_A:
1050                                 /* Flag that a good match was found */
1051                                 amatch = true;
1052
1053                                 /* continue in case a CNAME also exists */
1054                                 continue;
1055
1056                           case T_CNAME:
1057                                 if (DontExpandCnames)
1058                                 {
1059                                         /* got CNAME -- guaranteed canonical */
1060                                         amatch = true;
1061                                         break;
1062                                 }
1063
1064                                 if (loopcnt++ > MAXCNAMEDEPTH)
1065                                 {
1066                                         /*XXX should notify postmaster XXX*/
1067                                         message("DNS failure: CNAME loop for %s",
1068                                                 host);
1069                                         if (CurEnv->e_message == NULL)
1070                                         {
1071                                                 char ebuf[MAXLINE];
1072
1073                                                 (void) sm_snprintf(ebuf,
1074                                                         sizeof(ebuf),
1075                                                         "Deferred: DNS failure: CNAME loop for %.100s",
1076                                                         host);
1077                                                 CurEnv->e_message =
1078                                                     sm_rpool_strdup_x(
1079                                                         CurEnv->e_rpool, ebuf);
1080                                         }
1081                                         SM_SET_H_ERRNO(NO_RECOVERY);
1082                                         *statp = EX_CONFIG;
1083                                         return false;
1084                                 }
1085
1086                                 /* value points at name */
1087                                 if ((ret = dn_expand((unsigned char *)&answer,
1088                                                      eom, ap, (RES_UNC_T) nbuf,
1089                                                      sizeof(nbuf))) < 0)
1090                                         break;
1091                                 (void) sm_strlcpy(host, nbuf, hbsize);
1092
1093                                 /*
1094                                 **  RFC 1034 section 3.6 specifies that CNAME
1095                                 **  should point at the canonical name -- but
1096                                 **  urges software to try again anyway.
1097                                 */
1098
1099                                 goto cnameloop;
1100
1101                           default:
1102                                 /* not a record of interest */
1103                                 continue;
1104                         }
1105                 }
1106
1107                 if (amatch)
1108                 {
1109                         /*
1110                         **  Got a good match -- either an A, CNAME, or an
1111                         **  exact MX record.  Save it and get out of here.
1112                         */
1113
1114                         mxmatch = *dp;
1115                         break;
1116                 }
1117
1118                 /*
1119                 **  Nothing definitive yet.
1120                 **      If this was a T_A query and we haven't yet found a MX
1121                 **              match, try T_MX if allowed to do so.
1122                 **      Otherwise, try the next domain.
1123                 */
1124
1125 # if NETINET6
1126                 if (qtype == T_AAAA)
1127                         qtype = T_A;
1128                 else
1129 # endif /* NETINET6 */
1130                 if (qtype == T_A && !gotmx && (trymx || **dp == '\0'))
1131                         qtype = T_MX;
1132                 else
1133                 {
1134                         qtype = initial;
1135                         dp++;
1136                 }
1137         }
1138
1139         /* if nothing was found, we are done */
1140         if (mxmatch == NULL)
1141         {
1142                 if (*statp == EX_OK)
1143                         *statp = EX_NOHOST;
1144                 return false;
1145         }
1146
1147         /*
1148         **  Create canonical name and return.
1149         **  If saved domain name is null, name was already canonical.
1150         **  Otherwise append the saved domain name.
1151         */
1152
1153         (void) sm_snprintf(nbuf, sizeof(nbuf), "%.*s%s%.*s", MAXDNAME, host,
1154                            *mxmatch == '\0' ? "" : ".",
1155                            MAXDNAME, mxmatch);
1156         (void) sm_strlcpy(host, nbuf, hbsize);
1157         if (tTd(8, 5))
1158                 sm_dprintf("dns_getcanonname: %s\n", host);
1159         *statp = EX_OK;
1160
1161         /* return only one TTL entry, that should be sufficient */
1162         if (ttl > 0 && pttl != NULL)
1163                 *pttl = ttl;
1164         return true;
1165 }
1166 #endif /* NAMED_BIND */