src/src/routers/dnslookup.c

   1 /* $Cambridge: exim/src/src/routers/dnslookup.c,v 1.3 2005/01/11 15:51:03 ph10 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2005 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 #include "../exim.h"
  11 #include "rf_functions.h"
  12 #include "dnslookup.h"
  13
  14
  15
  16 /* Options specific to the dnslookup router. */
  17
  18 optionlist dnslookup_router_options[] = {
  19   { "check_secondary_mx", opt_bool,
  20       (void *)(offsetof(dnslookup_router_options_block, check_secondary_mx)) },
  21   { "check_srv",          opt_stringptr,
  22       (void *)(offsetof(dnslookup_router_options_block, check_srv)) },
  23   { "mx_domains",         opt_stringptr,
  24       (void *)(offsetof(dnslookup_router_options_block, mx_domains)) },
  25   { "mx_fail_domains",    opt_stringptr,
  26       (void *)(offsetof(dnslookup_router_options_block, mx_fail_domains)) },
  27   { "qualify_single",     opt_bool,
  28       (void *)(offsetof(dnslookup_router_options_block, qualify_single)) },
  29   { "rewrite_headers",    opt_bool,
  30       (void *)(offsetof(dnslookup_router_options_block, rewrite_headers)) },
  31   { "same_domain_copy_routing", opt_bool|opt_public,
  32       (void *)(offsetof(router_instance, same_domain_copy_routing)) },
  33   { "search_parents",     opt_bool,
  34       (void *)(offsetof(dnslookup_router_options_block, search_parents)) },
  35   { "srv_fail_domains",   opt_stringptr,
  36       (void *)(offsetof(dnslookup_router_options_block, srv_fail_domains)) },
  37   { "widen_domains",      opt_stringptr,
  38       (void *)(offsetof(dnslookup_router_options_block, widen_domains)) }
  39 };
  40
  41 /* Size of the options list. An extern variable has to be used so that its
  42 address can appear in the tables drtables.c. */
  43
  44 int dnslookup_router_options_count =
  45   sizeof(dnslookup_router_options)/sizeof(optionlist);
  46
  47 /* Default private options block for the dnslookup router. */
  48
  49 dnslookup_router_options_block dnslookup_router_option_defaults = {
  50   FALSE,           /* check_secondary_mx */
  51   TRUE,            /* qualify_single */
  52   FALSE,           /* search_parents */
  53   TRUE,            /* rewrite_headers */
  54   NULL,            /* widen_domains */
  55   NULL,            /* mx_domains */
  56   NULL,            /* mx_fail_domains */
  57   NULL,            /* srv_fail_domains */
  58   NULL             /* check_srv */
  59 };
  60
  61
  62
  63 /*************************************************
  64 *          Initialization entry point            *
  65 *************************************************/
  66
  67 /* Called for each instance, after its options have been read, to enable
  68 consistency checks to be done, or anything else that needs to be set up. */
  69
  70 void
  71 dnslookup_router_init(router_instance *rblock)
  72 {
  73 /*
  74 dnslookup_router_options_block *ob =
  75   (dnslookup_router_options_block *)(rblock->options_block);
  76 */
  77 rblock = rblock;
  78 }
  79
  80
  81
  82 /*************************************************
  83 *              Main entry point                  *
  84 *************************************************/
  85
  86 /* See local README for interface details. This router returns:
  87
  88 DECLINE
  89   . the domain does not exist in the DNS
  90   . MX records point to non-existent hosts (including RHS = IP address)
  91   . a single SRV record has a host name of "." (=> no service)
  92   . syntactically invalid mail domain
  93   . check_secondary_mx set, and local host not in host list
  94
  95 DEFER
  96   . lookup defer for mx_domains
  97   . timeout etc on DNS lookup
  98   . verifying the errors address caused a deferment or a big disaster such
  99       as an expansion failure (rf_get_errors_address)
 100   . expanding a headers_{add,remove} string caused a deferment or another
 101       expansion error (rf_get_munge_headers)
 102   . a problem in rf_get_transport: no transport when one is needed;
 103       failed to expand dynamic transport; failed to find dynamic transport
 104   . failure to expand or find a uid/gid (rf_get_ugid via rf_queue_add)
 105   . self = "freeze", self = "defer"
 106
 107 PASS
 108   . timeout etc on DNS lookup and pass_on_timeout set
 109   . self = "pass"
 110
 111 REROUTED
 112   . routed to local host, but name was expanded by DNS lookup, so a
 113       re-routing should take place
 114   . self = "reroute"
 115
 116   In both cases the new address will have been set up as a child
 117
 118 FAIL
 119   . self = "fail"
 120
 121 OK
 122   added address to addr_local or addr_remote, as appropriate for the
 123   type of transport; this includes the self="send" case.
 124 */
 125
 126 int
 127 dnslookup_router_entry(
 128   router_instance *rblock,        /* data for this instantiation */
 129   address_item *addr,             /* address we are working on */
 130   struct passwd *pw,              /* passwd entry after check_local_user */
 131   BOOL verify,                    /* TRUE when verifying */
 132   address_item **addr_local,      /* add it to this if it's local */
 133   address_item **addr_remote,     /* add it to this if it's remote */
 134   address_item **addr_new,        /* put new addresses on here */
 135   address_item **addr_succeed)    /* put old address here on success */
 136 {
 137 host_item h;
 138 int rc;
 139 int widen_sep = 0;
 140 int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A;
 141 dnslookup_router_options_block *ob =
 142   (dnslookup_router_options_block *)(rblock->options_block);
 143 uschar *srv_service = NULL;
 144 uschar *widen = NULL;
 145 uschar *pre_widen = addr->domain;
 146 uschar *post_widen = NULL;
 147 uschar *fully_qualified_name;
 148 uschar *listptr;
 149 uschar widen_buffer[256];
 150
 151 addr_new = addr_new;          /* Keep picky compilers happy */
 152 addr_succeed = addr_succeed;
 153
 154 DEBUG(D_route)
 155   debug_printf("%s router called for %s\n  domain = %s\n",
 156     rblock->name, addr->address, addr->domain);
 157
 158 /* If an SRV check is required, expand the service name */
 159
 160 if (ob->check_srv != NULL)
 161   {
 162   srv_service = expand_string(ob->check_srv);
 163   if (srv_service == NULL && !expand_string_forcedfail)
 164     {
 165     addr->message = string_sprintf("%s router: failed to expand \"%s\": %s",
 166       rblock->name, ob->check_srv, expand_string_message);
 167     return DEFER;
 168     }
 169   else whichrrs |= HOST_FIND_BY_SRV;
 170   }
 171
 172 /* Set up the first of any widening domains. The code further down copes with
 173 either pre- or post-widening, but at present there is no way to turn on
 174 pre-widening, as actually doing so seems like a rather bad idea, and nobody has
 175 requested it. Pre-widening would cause local abbreviated names to take
 176 precedence over global names. For example, if the domain is "xxx.ch" it might
 177 be something in the "ch" toplevel domain, but it also might be xxx.ch.xyz.com.
 178 The choice of pre- or post-widening affects which takes precedence. If ever
 179 somebody comes up with some kind of requirement for pre-widening, presumably
 180 with some conditions under which it is done, it can be selected here. */
 181
 182 if (ob->widen_domains != NULL)
 183   {
 184   listptr = ob->widen_domains;
 185   widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
 186     sizeof(widen_buffer));
 187
 188 /****
 189   if (some condition requiring pre-widening)
 190     {
 191     post_widen = pre_widen;
 192     pre_widen = NULL;
 193     }
 194 ****/
 195   }
 196
 197 /* Loop to cope with explicit widening of domains as configured. This code
 198 copes with widening that may happen before or after the original name. The
 199 decision as to which is taken above. */
 200
 201 for (;;)
 202   {
 203   int flags = whichrrs;
 204   BOOL removed = FALSE;
 205
 206   if (pre_widen != NULL)
 207     {
 208     h.name = pre_widen;
 209     pre_widen = NULL;
 210     }
 211   else if (widen != NULL)
 212     {
 213     h.name = string_sprintf("%s.%s", addr->domain, widen);
 214     widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
 215       sizeof(widen_buffer));
 216     DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name,
 217       addr->domain, h.name);
 218     }
 219   else if (post_widen != NULL)
 220     {
 221     h.name = post_widen;
 222     post_widen = NULL;
 223     DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n",
 224       rblock->name, h.name);
 225     }
 226   else return DECLINE;
 227
 228   /* Set up the rest of the initial host item. Others may get chained on if
 229   there is more than one IP address. We set it up here instead of outside the
 230   loop so as to re-initialize if a previous try succeeded but was rejected
 231   because of not having an MX record. */
 232
 233   h.next = NULL;
 234   h.address = NULL;
 235   h.port = PORT_NONE;
 236   h.mx = MX_NONE;
 237   h.status = hstatus_unknown;
 238   h.why = hwhy_unknown;
 239   h.last_try = 0;
 240
 241   /* Unfortunately, we cannot set the mx_only option in advance, because the
 242   DNS lookup may extend an unqualified name. Therefore, we must do the test
 243   subsequently. */
 244
 245   if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE;
 246   if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS;
 247
 248   rc = host_find_bydns(&h, rblock->ignore_target_hosts, flags, srv_service,
 249     ob->srv_fail_domains, ob->mx_fail_domains, &fully_qualified_name, &removed);
 250   if (removed) setflag(addr, af_local_host_removed);
 251
 252   /* If host found with only address records, test for the domain's being in
 253   the mx_domains list. Note that this applies also to SRV records; the name of
 254   the option is historical. */
 255
 256   if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 &&
 257        ob->mx_domains != NULL)
 258     {
 259     switch(match_isinlist(fully_qualified_name, &(ob->mx_domains), 0,
 260           &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
 261       {
 262       case DEFER:
 263       addr->message = US"lookup defer for mx_domains";
 264       return DEFER;
 265
 266       case OK:
 267       DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n",
 268         rblock->name, fully_qualified_name);
 269       continue;
 270       }
 271     }
 272
 273   /* Deferral returns forthwith, and anything other than failure breaks the
 274   loop. */
 275
 276   if (rc == HOST_FIND_AGAIN)
 277     {
 278     if (rblock->pass_on_timeout)
 279       {
 280       DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n",
 281         rblock->name);
 282       return PASS;
 283       }
 284     addr->message = US"host lookup did not complete";
 285     return DEFER;
 286     }
 287
 288   if (rc != HOST_FIND_FAILED) break;
 289
 290   /* Check to see if the failure is the result of MX records pointing
 291   to non-existent domains, and if so, set an appropriate error message; the
 292   case of an SRV record pointing to "." is another special case that we can
 293   detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in
 294   this case don't do the widening. We need check only the first host to see if
 295   its MX has been filled in, but there is no address, because if there were any
 296   usable addresses returned, we would not have had HOST_FIND_FAILED.
 297
 298   As a common cause of this problem is MX records with IP addresses on the
 299   RHS, give a special message in this case. */
 300
 301   if (h.mx >= 0 && h.address == NULL)
 302     {
 303     if (h.name[0] == 0)
 304       addr->message = US"an SRV record indicated no SMTP service";
 305     else
 306       {
 307       addr->message = US"all relevant MX records point to non-existent hosts";
 308       if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) > 0)
 309         {
 310         addr->user_message =
 311           string_sprintf("It appears that the DNS operator for %s\n"
 312             "has installed an invalid MX record with an IP address\n"
 313             "instead of a domain name on the right hand side.", addr->domain);
 314         addr->message = string_sprintf("%s or (invalidly) to IP addresses",
 315           addr->message);
 316         }
 317       }
 318     return DECLINE;
 319     }
 320
 321   /* If there's a syntax error, do not continue with any widening, and note
 322   the error. */
 323
 324   if (host_find_failed_syntax)
 325     {
 326     addr->message = string_sprintf("mail domain \"%s\" is syntactically "
 327       "invalid", h.name);
 328     return DECLINE;
 329     }
 330   }
 331
 332 /* If the original domain name has been changed as a result of the host lookup,
 333 set up a child address for rerouting and request header rewrites if so
 334 configured. Then yield REROUTED. However, if the only change is a change of
 335 case in the domain name, which some resolvers yield (others don't), just change
 336 the domain name in the original address so that the official version is used in
 337 RCPT commands. */
 338
 339 if (Ustrcmp(addr->domain, fully_qualified_name) != 0)
 340   {
 341   if (strcmpic(addr->domain, fully_qualified_name) == 0)
 342     {
 343     uschar *at = Ustrrchr(addr->address, '@');
 344     memcpy(at+1, fully_qualified_name, Ustrlen(at+1));
 345     }
 346   else
 347     {
 348     rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new);
 349     return REROUTED;
 350     }
 351   }
 352
 353 /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX
 354 records with the lowest numbered one pointing to a host with an IP address that
 355 is set on one of the interfaces of this machine, or found A records or got
 356 addresses from gethostbyname() that contain one for this machine. This can
 357 happen quite legitimately if the original name was a shortened form of a
 358 domain, but we will have picked that up already via the name change test above.
 359
 360 Otherwise, the action to be taken can be configured by the self option, the
 361 handling of which is in a separate function, as it is also required for other
 362 routers. */
 363
 364 if (rc == HOST_FOUND_LOCAL)
 365   {
 366   rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite,
 367     rblock->self, addr_new);
 368   if (rc != OK) return rc;
 369   }
 370
 371 /* Otherwise, insist on being a secondary MX if so configured */
 372
 373 else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed))
 374   {
 375   DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n");
 376   return DECLINE;
 377   }
 378
 379 /* Set up the errors address, if any. */
 380
 381 rc = rf_get_errors_address(addr, rblock, verify, &(addr->p.errors_address));
 382 if (rc != OK) return rc;
 383
 384 /* Set up the additional and removeable headers for this address. */
 385
 386 rc = rf_get_munge_headers(addr, rblock, &(addr->p.extra_headers),
 387   &(addr->p.remove_headers));
 388 if (rc != OK) return rc;
 389
 390 /* Get store in which to preserve the original host item, chained on
 391 to the address. */
 392
 393 addr->host_list = store_get(sizeof(host_item));
 394 addr->host_list[0] = h;
 395
 396 /* Fill in the transport and queue the address for delivery. */
 397
 398 if (!rf_get_transport(rblock->transport_name, &(rblock->transport),
 399       addr, rblock->name, NULL))
 400   return DEFER;
 401
 402 addr->transport = rblock->transport;
 403
 404 return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)?
 405   OK : DEFER;
 406 }
 407
 408 /* End of routers/dnslookup.c */