2471f2fb7884cce90b19df95d3902c1642115240
[exim.git] / src / src / routers / dnslookup.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 #include "../exim.h"
9 #include "rf_functions.h"
10 #include "dnslookup.h"
11
12
13
14 /* Options specific to the dnslookup router. */
15
16 optionlist dnslookup_router_options[] = {
17 { "check_secondary_mx", opt_bool,
18 (void *)(offsetof(dnslookup_router_options_block, check_secondary_mx)) },
19 { "check_srv", opt_stringptr,
20 (void *)(offsetof(dnslookup_router_options_block, check_srv)) },
21 { "fail_defer_domains", opt_stringptr,
22 (void *)(offsetof(dnslookup_router_options_block, fail_defer_domains)) },
23 { "ipv4_only", opt_stringptr,
24 (void *)(offsetof(dnslookup_router_options_block, ipv4_only)) },
25 { "ipv4_prefer", opt_stringptr,
26 (void *)(offsetof(dnslookup_router_options_block, ipv4_prefer)) },
27 { "mx_domains", opt_stringptr,
28 (void *)(offsetof(dnslookup_router_options_block, mx_domains)) },
29 { "mx_fail_domains", opt_stringptr,
30 (void *)(offsetof(dnslookup_router_options_block, mx_fail_domains)) },
31 { "qualify_single", opt_bool,
32 (void *)(offsetof(dnslookup_router_options_block, qualify_single)) },
33 { "rewrite_headers", opt_bool,
34 (void *)(offsetof(dnslookup_router_options_block, rewrite_headers)) },
35 { "same_domain_copy_routing", opt_bool|opt_public,
36 (void *)(offsetof(router_instance, same_domain_copy_routing)) },
37 { "search_parents", opt_bool,
38 (void *)(offsetof(dnslookup_router_options_block, search_parents)) },
39 { "srv_fail_domains", opt_stringptr,
40 (void *)(offsetof(dnslookup_router_options_block, srv_fail_domains)) },
41 { "widen_domains", opt_stringptr,
42 (void *)(offsetof(dnslookup_router_options_block, widen_domains)) }
43 };
44
45 /* Size of the options list. An extern variable has to be used so that its
46 address can appear in the tables drtables.c. */
47
48 int dnslookup_router_options_count =
49 sizeof(dnslookup_router_options)/sizeof(optionlist);
50
51
52 #ifdef MACRO_PREDEF
53
54 /* Dummy entries */
55 dnslookup_router_options_block dnslookup_router_option_defaults = {0};
56 void dnslookup_router_init(router_instance *rblock) {}
57 int dnslookup_router_entry(router_instance *rblock, address_item *addr,
58 struct passwd *pw, int verify, address_item **addr_local,
59 address_item **addr_remote, address_item **addr_new,
60 address_item **addr_succeed) {return 0;}
61
62 #else /*!MACRO_PREDEF*/
63
64
65
66
67 /* Default private options block for the dnslookup router. */
68
69 dnslookup_router_options_block dnslookup_router_option_defaults = {
70 .check_secondary_mx = FALSE,
71 .qualify_single = TRUE,
72 .search_parents = FALSE,
73 .rewrite_headers = TRUE,
74 .widen_domains = NULL,
75 .mx_domains = NULL,
76 .mx_fail_domains = NULL,
77 .srv_fail_domains = NULL,
78 .check_srv = NULL,
79 .fail_defer_domains = NULL,
80 .ipv4_only = NULL,
81 .ipv4_prefer = NULL,
82 };
83
84
85
86 /*************************************************
87 * Initialization entry point *
88 *************************************************/
89
90 /* Called for each instance, after its options have been read, to enable
91 consistency checks to be done, or anything else that needs to be set up. */
92
93 void
94 dnslookup_router_init(router_instance *rblock)
95 {
96 /*
97 dnslookup_router_options_block *ob =
98 (dnslookup_router_options_block *)(rblock->options_block);
99 */
100 rblock = rblock;
101 }
102
103
104
105 /*************************************************
106 * Main entry point *
107 *************************************************/
108
109 /* See local README for interface details. This router returns:
110
111 DECLINE
112 . the domain does not exist in the DNS
113 . MX records point to non-existent hosts (including RHS = IP address)
114 . a single SRV record has a host name of "." (=> no service)
115 . syntactically invalid mail domain
116 . check_secondary_mx set, and local host not in host list
117
118 DEFER
119 . lookup defer for mx_domains
120 . timeout etc on DNS lookup
121 . verifying the errors address caused a deferment or a big disaster such
122 as an expansion failure (rf_get_errors_address)
123 . expanding a headers_{add,remove} string caused a deferment or another
124 expansion error (rf_get_munge_headers)
125 . a problem in rf_get_transport: no transport when one is needed;
126 failed to expand dynamic transport; failed to find dynamic transport
127 . failure to expand or find a uid/gid (rf_get_ugid via rf_queue_add)
128 . self = "freeze", self = "defer"
129
130 PASS
131 . timeout etc on DNS lookup and pass_on_timeout set
132 . self = "pass"
133
134 REROUTED
135 . routed to local host, but name was expanded by DNS lookup, so a
136 re-routing should take place
137 . self = "reroute"
138
139 In both cases the new address will have been set up as a child
140
141 FAIL
142 . self = "fail"
143
144 OK
145 added address to addr_local or addr_remote, as appropriate for the
146 type of transport; this includes the self="send" case.
147 */
148
149 int
150 dnslookup_router_entry(
151 router_instance *rblock, /* data for this instantiation */
152 address_item *addr, /* address we are working on */
153 struct passwd *pw, /* passwd entry after check_local_user */
154 int verify, /* v_none/v_recipient/v_sender/v_expn */
155 address_item **addr_local, /* add it to this if it's local */
156 address_item **addr_remote, /* add it to this if it's remote */
157 address_item **addr_new, /* put new addresses on here */
158 address_item **addr_succeed) /* put old address here on success */
159 {
160 host_item h;
161 int rc;
162 int widen_sep = 0;
163 int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A | HOST_FIND_BY_AAAA;
164 dnslookup_router_options_block *ob =
165 (dnslookup_router_options_block *)(rblock->options_block);
166 uschar *srv_service = NULL;
167 uschar *widen = NULL;
168 const uschar *pre_widen = addr->domain;
169 const uschar *post_widen = NULL;
170 const uschar *fully_qualified_name;
171 const uschar *listptr;
172 uschar widen_buffer[256];
173
174 addr_new = addr_new; /* Keep picky compilers happy */
175 addr_succeed = addr_succeed;
176
177 DEBUG(D_route)
178 debug_printf("%s router called for %s\n domain = %s\n",
179 rblock->name, addr->address, addr->domain);
180
181 /* If an SRV check is required, expand the service name */
182
183 if (ob->check_srv)
184 {
185 if ( !(srv_service = expand_string(ob->check_srv))
186 && !f.expand_string_forcedfail)
187 {
188 addr->message = string_sprintf("%s router: failed to expand \"%s\": %s",
189 rblock->name, ob->check_srv, expand_string_message);
190 return DEFER;
191 }
192 else whichrrs |= HOST_FIND_BY_SRV;
193 }
194
195 /* Set up the first of any widening domains. The code further down copes with
196 either pre- or post-widening, but at present there is no way to turn on
197 pre-widening, as actually doing so seems like a rather bad idea, and nobody has
198 requested it. Pre-widening would cause local abbreviated names to take
199 precedence over global names. For example, if the domain is "xxx.ch" it might
200 be something in the "ch" toplevel domain, but it also might be xxx.ch.xyz.com.
201 The choice of pre- or post-widening affects which takes precedence. If ever
202 somebody comes up with some kind of requirement for pre-widening, presumably
203 with some conditions under which it is done, it can be selected here.
204
205 The rewrite_headers option works only when routing an address at transport
206 time, because the alterations to the headers are not persistent so must be
207 worked out immediately before they are used. Sender addresses are routed for
208 verification purposes, but never at transport time, so any header changes that
209 you might expect as a result of sender domain widening do not occur. Therefore
210 we do not perform widening when verifying sender addresses; however, widening
211 sender addresses is OK if we do not have to rewrite the headers. A corollary
212 of this is that if the current address is not the original address, then it
213 does not appear in the message header so it is also OK to widen. The
214 suppression of widening for sender addresses is silent because it is the
215 normal desirable behaviour. */
216
217 if ( ob->widen_domains
218 && (verify != v_sender || !ob->rewrite_headers || addr->parent))
219 {
220 listptr = ob->widen_domains;
221 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
222 sizeof(widen_buffer));
223
224 /****
225 if (some condition requiring pre-widening)
226 {
227 post_widen = pre_widen;
228 pre_widen = NULL;
229 }
230 ****/
231 }
232
233 /* Loop to cope with explicit widening of domains as configured. This code
234 copes with widening that may happen before or after the original name. The
235 decision as to which is taken above. */
236
237 for (;;)
238 {
239 int flags = whichrrs;
240 BOOL removed = FALSE;
241
242 if (pre_widen)
243 {
244 h.name = pre_widen;
245 pre_widen = NULL;
246 }
247 else if (widen)
248 {
249 h.name = string_sprintf("%s.%s", addr->domain, widen);
250 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
251 sizeof(widen_buffer));
252 DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name,
253 addr->domain, h.name);
254 }
255 else if (post_widen)
256 {
257 h.name = post_widen;
258 post_widen = NULL;
259 DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n",
260 rblock->name, h.name);
261 }
262 else return DECLINE;
263
264 /* Check if we must request only. or prefer, ipv4 */
265
266 if ( ob->ipv4_only
267 && expand_check_condition(ob->ipv4_only, rblock->name, US"router"))
268 flags = flags & ~HOST_FIND_BY_AAAA | HOST_FIND_IPV4_ONLY;
269 else if (f.search_find_defer)
270 return DEFER;
271 if ( ob->ipv4_prefer
272 && expand_check_condition(ob->ipv4_prefer, rblock->name, US"router"))
273 flags |= HOST_FIND_IPV4_FIRST;
274 else if (f.search_find_defer)
275 return DEFER;
276
277 /* Set up the rest of the initial host item. Others may get chained on if
278 there is more than one IP address. We set it up here instead of outside the
279 loop so as to re-initialize if a previous try succeeded but was rejected
280 because of not having an MX record. */
281
282 h.next = NULL;
283 h.address = NULL;
284 h.port = PORT_NONE;
285 h.mx = MX_NONE;
286 h.status = hstatus_unknown;
287 h.why = hwhy_unknown;
288 h.last_try = 0;
289
290 /* Unfortunately, we cannot set the mx_only option in advance, because the
291 DNS lookup may extend an unqualified name. Therefore, we must do the test
292 stoubsequently. We use the same logic as that for widen_domains above to avoid
293 requesting a header rewrite that cannot work. */
294
295 if (verify != v_sender || !ob->rewrite_headers || addr->parent)
296 {
297 if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE;
298 if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS;
299 }
300
301 rc = host_find_bydns(&h, CUS rblock->ignore_target_hosts, flags,
302 srv_service, ob->srv_fail_domains, ob->mx_fail_domains,
303 &rblock->dnssec,
304 &fully_qualified_name, &removed);
305
306 if (removed) setflag(addr, af_local_host_removed);
307
308 /* If host found with only address records, test for the domain's being in
309 the mx_domains list. Note that this applies also to SRV records; the name of
310 the option is historical. */
311
312 if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 &&
313 ob->mx_domains)
314 switch(match_isinlist(fully_qualified_name,
315 CUSS &(ob->mx_domains), 0,
316 &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
317 {
318 case DEFER:
319 addr->message = US"lookup defer for mx_domains";
320 return DEFER;
321
322 case OK:
323 DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n",
324 rblock->name, fully_qualified_name);
325 continue;
326 }
327
328 /* Deferral returns forthwith, and anything other than failure breaks the
329 loop. */
330
331 if (rc == HOST_FIND_SECURITY)
332 {
333 addr->message = US"host lookup done insecurely";
334 return DEFER;
335 }
336 if (rc == HOST_FIND_AGAIN)
337 {
338 if (rblock->pass_on_timeout)
339 {
340 DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n",
341 rblock->name);
342 return PASS;
343 }
344 addr->message = US"host lookup did not complete";
345 return DEFER;
346 }
347
348 if (rc != HOST_FIND_FAILED) break;
349
350 if (ob->fail_defer_domains)
351 switch(match_isinlist(fully_qualified_name,
352 CUSS &ob->fail_defer_domains, 0,
353 &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
354 {
355 case DEFER:
356 addr->message = US"lookup defer for fail_defer_domains option";
357 return DEFER;
358
359 case OK:
360 DEBUG(D_route) debug_printf("%s router: matched fail_defer_domains\n",
361 rblock->name);
362 addr->message = US"missing MX, or all MXs point to missing A records,"
363 " and defer requested";
364 return DEFER;
365 }
366 /* Check to see if the failure is the result of MX records pointing to
367 non-existent domains, and if so, set an appropriate error message; the case
368 of an MX or SRV record pointing to "." is another special case that we can
369 detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in
370 this case don't do the widening. We need check only the first host to see if
371 its MX has been filled in, but there is no address, because if there were any
372 usable addresses returned, we would not have had HOST_FIND_FAILED.
373
374 As a common cause of this problem is MX records with IP addresses on the
375 RHS, give a special message in this case. */
376
377 if (h.mx >= 0 && h.address == NULL)
378 {
379 setflag(addr, af_pass_message); /* This is not a security risk */
380 if (h.name[0] == 0)
381 addr->message = US"an MX or SRV record indicated no SMTP service";
382 else
383 {
384 addr->basic_errno = ERRNO_UNKNOWNHOST;
385 addr->message = US"all relevant MX records point to non-existent hosts";
386 if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0)
387 {
388 addr->user_message =
389 string_sprintf("It appears that the DNS operator for %s\n"
390 "has installed an invalid MX record with an IP address\n"
391 "instead of a domain name on the right hand side.", addr->domain);
392 addr->message = string_sprintf("%s or (invalidly) to IP addresses",
393 addr->message);
394 }
395 }
396 return DECLINE;
397 }
398
399 /* If there's a syntax error, do not continue with any widening, and note
400 the error. */
401
402 if (f.host_find_failed_syntax)
403 {
404 addr->message = string_sprintf("mail domain \"%s\" is syntactically "
405 "invalid", h.name);
406 return DECLINE;
407 }
408 }
409
410 /* If the original domain name has been changed as a result of the host lookup,
411 set up a child address for rerouting and request header rewrites if so
412 configured. Then yield REROUTED. However, if the only change is a change of
413 case in the domain name, which some resolvers yield (others don't), just change
414 the domain name in the original address so that the official version is used in
415 RCPT commands. */
416
417 if (Ustrcmp(addr->domain, fully_qualified_name) != 0)
418 {
419 if (strcmpic(addr->domain, fully_qualified_name) == 0)
420 {
421 uschar *at = Ustrrchr(addr->address, '@');
422 memcpy(at+1, fully_qualified_name, Ustrlen(at+1));
423 }
424 else
425 {
426 rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new);
427 return REROUTED;
428 }
429 }
430
431 /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX
432 records with the lowest numbered one pointing to a host with an IP address that
433 is set on one of the interfaces of this machine, or found A records or got
434 addresses from gethostbyname() that contain one for this machine. This can
435 happen quite legitimately if the original name was a shortened form of a
436 domain, but we will have picked that up already via the name change test above.
437
438 Otherwise, the action to be taken can be configured by the self option, the
439 handling of which is in a separate function, as it is also required for other
440 routers. */
441
442 if (rc == HOST_FOUND_LOCAL)
443 {
444 rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite,
445 rblock->self, addr_new);
446 if (rc != OK) return rc;
447 }
448
449 /* Otherwise, insist on being a secondary MX if so configured */
450
451 else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed))
452 {
453 DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n");
454 return DECLINE;
455 }
456
457 /* Set up the errors address, if any. */
458
459 rc = rf_get_errors_address(addr, rblock, verify, &addr->prop.errors_address);
460 if (rc != OK) return rc;
461
462 /* Set up the additional and removable headers for this address. */
463
464 rc = rf_get_munge_headers(addr, rblock, &addr->prop.extra_headers,
465 &addr->prop.remove_headers);
466 if (rc != OK) return rc;
467
468 /* Get store in which to preserve the original host item, chained on
469 to the address. */
470
471 addr->host_list = store_get(sizeof(host_item), FALSE);
472 addr->host_list[0] = h;
473
474 /* Fill in the transport and queue the address for delivery. */
475
476 if (!rf_get_transport(rblock->transport_name, &(rblock->transport),
477 addr, rblock->name, NULL))
478 return DEFER;
479
480 addr->transport = rblock->transport;
481
482 return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)?
483 OK : DEFER;
484 }
485
486 #endif /*!MACRO_PREDEF*/
487 /* End of routers/dnslookup.c */
488 /* vi: aw ai sw=2
489 */