7e074c23ed02bf90bf6740c1fbac4f2e751a35cf
[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 #define LOFF(field) OPT_OFF(dnslookup_router_options_block, field)
16
17 optionlist dnslookup_router_options[] = {
18 { "check_secondary_mx", opt_bool, LOFF(check_secondary_mx) },
19 { "check_srv", opt_stringptr, LOFF(check_srv) },
20 { "fail_defer_domains", opt_stringptr, LOFF(fail_defer_domains) },
21 { "ipv4_only", opt_stringptr, LOFF(ipv4_only) },
22 { "ipv4_prefer", opt_stringptr, LOFF(ipv4_prefer) },
23 { "mx_domains", opt_stringptr, LOFF(mx_domains) },
24 { "mx_fail_domains", opt_stringptr, LOFF(mx_fail_domains) },
25 { "qualify_single", opt_bool, LOFF(qualify_single) },
26 { "rewrite_headers", opt_bool, LOFF(rewrite_headers) },
27 { "same_domain_copy_routing", opt_bool|opt_public, OPT_OFF(router_instance, same_domain_copy_routing) },
28 { "search_parents", opt_bool, LOFF(search_parents) },
29 { "srv_fail_domains", opt_stringptr, LOFF(srv_fail_domains) },
30 { "widen_domains", opt_stringptr, LOFF(widen_domains) }
31 };
32
33 /* Size of the options list. An extern variable has to be used so that its
34 address can appear in the tables drtables.c. */
35
36 int dnslookup_router_options_count =
37 sizeof(dnslookup_router_options)/sizeof(optionlist);
38
39
40 #ifdef MACRO_PREDEF
41
42 /* Dummy entries */
43 dnslookup_router_options_block dnslookup_router_option_defaults = {0};
44 void dnslookup_router_init(router_instance *rblock) {}
45 int dnslookup_router_entry(router_instance *rblock, address_item *addr,
46 struct passwd *pw, int verify, address_item **addr_local,
47 address_item **addr_remote, address_item **addr_new,
48 address_item **addr_succeed) {return 0;}
49
50 #else /*!MACRO_PREDEF*/
51
52
53
54
55 /* Default private options block for the dnslookup router. */
56
57 dnslookup_router_options_block dnslookup_router_option_defaults = {
58 .check_secondary_mx = FALSE,
59 .qualify_single = TRUE,
60 .search_parents = FALSE,
61 .rewrite_headers = TRUE,
62 .widen_domains = NULL,
63 .mx_domains = NULL,
64 .mx_fail_domains = NULL,
65 .srv_fail_domains = NULL,
66 .check_srv = NULL,
67 .fail_defer_domains = NULL,
68 .ipv4_only = NULL,
69 .ipv4_prefer = NULL,
70 };
71
72
73
74 /*************************************************
75 * Initialization entry point *
76 *************************************************/
77
78 /* Called for each instance, after its options have been read, to enable
79 consistency checks to be done, or anything else that needs to be set up. */
80
81 void
82 dnslookup_router_init(router_instance *rblock)
83 {
84 /*
85 dnslookup_router_options_block *ob =
86 (dnslookup_router_options_block *)(rblock->options_block);
87 */
88 rblock = rblock;
89 }
90
91
92
93 /*************************************************
94 * Main entry point *
95 *************************************************/
96
97 /* See local README for interface details. This router returns:
98
99 DECLINE
100 . the domain does not exist in the DNS
101 . MX records point to non-existent hosts (including RHS = IP address)
102 . a single SRV record has a host name of "." (=> no service)
103 . syntactically invalid mail domain
104 . check_secondary_mx set, and local host not in host list
105
106 DEFER
107 . lookup defer for mx_domains
108 . timeout etc on DNS lookup
109 . verifying the errors address caused a deferment or a big disaster such
110 as an expansion failure (rf_get_errors_address)
111 . expanding a headers_{add,remove} string caused a deferment or another
112 expansion error (rf_get_munge_headers)
113 . a problem in rf_get_transport: no transport when one is needed;
114 failed to expand dynamic transport; failed to find dynamic transport
115 . failure to expand or find a uid/gid (rf_get_ugid via rf_queue_add)
116 . self = "freeze", self = "defer"
117
118 PASS
119 . timeout etc on DNS lookup and pass_on_timeout set
120 . self = "pass"
121
122 REROUTED
123 . routed to local host, but name was expanded by DNS lookup, so a
124 re-routing should take place
125 . self = "reroute"
126
127 In both cases the new address will have been set up as a child
128
129 FAIL
130 . self = "fail"
131
132 OK
133 added address to addr_local or addr_remote, as appropriate for the
134 type of transport; this includes the self="send" case.
135 */
136
137 int
138 dnslookup_router_entry(
139 router_instance *rblock, /* data for this instantiation */
140 address_item *addr, /* address we are working on */
141 struct passwd *pw, /* passwd entry after check_local_user */
142 int verify, /* v_none/v_recipient/v_sender/v_expn */
143 address_item **addr_local, /* add it to this if it's local */
144 address_item **addr_remote, /* add it to this if it's remote */
145 address_item **addr_new, /* put new addresses on here */
146 address_item **addr_succeed) /* put old address here on success */
147 {
148 host_item h;
149 int rc;
150 int widen_sep = 0;
151 int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A | HOST_FIND_BY_AAAA;
152 dnslookup_router_options_block *ob =
153 (dnslookup_router_options_block *)(rblock->options_block);
154 uschar *srv_service = NULL;
155 uschar *widen = NULL;
156 const uschar *pre_widen = addr->domain;
157 const uschar *post_widen = NULL;
158 const uschar *fully_qualified_name;
159 const uschar *listptr;
160 uschar widen_buffer[256];
161
162 addr_new = addr_new; /* Keep picky compilers happy */
163 addr_succeed = addr_succeed;
164
165 DEBUG(D_route)
166 debug_printf("%s router called for %s\n domain = %s\n",
167 rblock->name, addr->address, addr->domain);
168
169 /* If an SRV check is required, expand the service name */
170
171 if (ob->check_srv)
172 {
173 if ( !(srv_service = expand_string(ob->check_srv))
174 && !f.expand_string_forcedfail)
175 {
176 addr->message = string_sprintf("%s router: failed to expand \"%s\": %s",
177 rblock->name, ob->check_srv, expand_string_message);
178 return DEFER;
179 }
180 else whichrrs |= HOST_FIND_BY_SRV;
181 }
182
183 /* Set up the first of any widening domains. The code further down copes with
184 either pre- or post-widening, but at present there is no way to turn on
185 pre-widening, as actually doing so seems like a rather bad idea, and nobody has
186 requested it. Pre-widening would cause local abbreviated names to take
187 precedence over global names. For example, if the domain is "xxx.ch" it might
188 be something in the "ch" toplevel domain, but it also might be xxx.ch.xyz.com.
189 The choice of pre- or post-widening affects which takes precedence. If ever
190 somebody comes up with some kind of requirement for pre-widening, presumably
191 with some conditions under which it is done, it can be selected here.
192
193 The rewrite_headers option works only when routing an address at transport
194 time, because the alterations to the headers are not persistent so must be
195 worked out immediately before they are used. Sender addresses are routed for
196 verification purposes, but never at transport time, so any header changes that
197 you might expect as a result of sender domain widening do not occur. Therefore
198 we do not perform widening when verifying sender addresses; however, widening
199 sender addresses is OK if we do not have to rewrite the headers. A corollary
200 of this is that if the current address is not the original address, then it
201 does not appear in the message header so it is also OK to widen. The
202 suppression of widening for sender addresses is silent because it is the
203 normal desirable behaviour. */
204
205 if ( ob->widen_domains
206 && (verify != v_sender || !ob->rewrite_headers || addr->parent))
207 {
208 listptr = ob->widen_domains;
209 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
210 sizeof(widen_buffer));
211
212 /****
213 if (some condition requiring pre-widening)
214 {
215 post_widen = pre_widen;
216 pre_widen = NULL;
217 }
218 ****/
219 }
220
221 /* Loop to cope with explicit widening of domains as configured. This code
222 copes with widening that may happen before or after the original name. The
223 decision as to which is taken above. */
224
225 for (;;)
226 {
227 int flags = whichrrs;
228 BOOL removed = FALSE;
229
230 if (pre_widen)
231 {
232 h.name = pre_widen;
233 pre_widen = NULL;
234 }
235 else if (widen)
236 {
237 h.name = string_sprintf("%s.%s", addr->domain, widen);
238 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
239 sizeof(widen_buffer));
240 DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name,
241 addr->domain, h.name);
242 }
243 else if (post_widen)
244 {
245 h.name = post_widen;
246 post_widen = NULL;
247 DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n",
248 rblock->name, h.name);
249 }
250 else return DECLINE;
251
252 /* Check if we must request only. or prefer, ipv4 */
253
254 if ( ob->ipv4_only
255 && expand_check_condition(ob->ipv4_only, rblock->name, US"router"))
256 flags = flags & ~HOST_FIND_BY_AAAA | HOST_FIND_IPV4_ONLY;
257 else if (f.search_find_defer)
258 return DEFER;
259 if ( ob->ipv4_prefer
260 && expand_check_condition(ob->ipv4_prefer, rblock->name, US"router"))
261 flags |= HOST_FIND_IPV4_FIRST;
262 else if (f.search_find_defer)
263 return DEFER;
264
265 /* Set up the rest of the initial host item. Others may get chained on if
266 there is more than one IP address. We set it up here instead of outside the
267 loop so as to re-initialize if a previous try succeeded but was rejected
268 because of not having an MX record. */
269
270 h.next = NULL;
271 h.address = NULL;
272 h.port = PORT_NONE;
273 h.mx = MX_NONE;
274 h.status = hstatus_unknown;
275 h.why = hwhy_unknown;
276 h.last_try = 0;
277
278 /* Unfortunately, we cannot set the mx_only option in advance, because the
279 DNS lookup may extend an unqualified name. Therefore, we must do the test
280 subsequently. We use the same logic as that for widen_domains above to avoid
281 requesting a header rewrite that cannot work. */
282
283 if (verify != v_sender || !ob->rewrite_headers || addr->parent)
284 {
285 if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE;
286 if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS;
287 }
288
289 rc = host_find_bydns(&h, CUS rblock->ignore_target_hosts, flags,
290 srv_service, ob->srv_fail_domains, ob->mx_fail_domains,
291 &rblock->dnssec,
292 &fully_qualified_name, &removed);
293
294 if (removed) setflag(addr, af_local_host_removed);
295
296 /* If host found with only address records, test for the domain's being in
297 the mx_domains list. Note that this applies also to SRV records; the name of
298 the option is historical. */
299
300 if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 &&
301 ob->mx_domains)
302 switch(match_isinlist(fully_qualified_name,
303 CUSS &(ob->mx_domains), 0,
304 &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
305 {
306 case DEFER:
307 addr->message = US"lookup defer for mx_domains";
308 return DEFER;
309
310 case OK:
311 DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n",
312 rblock->name, fully_qualified_name);
313 continue;
314 }
315
316 /* Deferral returns forthwith, and anything other than failure breaks the
317 loop. */
318
319 if (rc == HOST_FIND_SECURITY)
320 {
321 addr->message = US"host lookup done insecurely";
322 return DEFER;
323 }
324 if (rc == HOST_FIND_AGAIN)
325 {
326 if (rblock->pass_on_timeout)
327 {
328 DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n",
329 rblock->name);
330 return PASS;
331 }
332 addr->message = US"host lookup did not complete";
333 return DEFER;
334 }
335
336 if (rc != HOST_FIND_FAILED) break;
337
338 if (ob->fail_defer_domains)
339 switch(match_isinlist(fully_qualified_name,
340 CUSS &ob->fail_defer_domains, 0,
341 &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
342 {
343 case DEFER:
344 addr->message = US"lookup defer for fail_defer_domains option";
345 return DEFER;
346
347 case OK:
348 DEBUG(D_route) debug_printf("%s router: matched fail_defer_domains\n",
349 rblock->name);
350 addr->message = US"missing MX, or all MXs point to missing A records,"
351 " and defer requested";
352 return DEFER;
353 }
354 /* Check to see if the failure is the result of MX records pointing to
355 non-existent domains, and if so, set an appropriate error message; the case
356 of an MX or SRV record pointing to "." is another special case that we can
357 detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in
358 this case don't do the widening. We need check only the first host to see if
359 its MX has been filled in, but there is no address, because if there were any
360 usable addresses returned, we would not have had HOST_FIND_FAILED.
361
362 As a common cause of this problem is MX records with IP addresses on the
363 RHS, give a special message in this case. */
364
365 if (h.mx >= 0 && h.address == NULL)
366 {
367 setflag(addr, af_pass_message); /* This is not a security risk */
368 if (h.name[0] == 0)
369 addr->message = US"an MX or SRV record indicated no SMTP service";
370 else
371 {
372 addr->basic_errno = ERRNO_UNKNOWNHOST;
373 addr->message = US"all relevant MX records point to non-existent hosts";
374 if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0)
375 {
376 addr->user_message =
377 string_sprintf("It appears that the DNS operator for %s\n"
378 "has installed an invalid MX record with an IP address\n"
379 "instead of a domain name on the right hand side.", addr->domain);
380 addr->message = string_sprintf("%s or (invalidly) to IP addresses",
381 addr->message);
382 }
383 }
384 return DECLINE;
385 }
386
387 /* If there's a syntax error, do not continue with any widening, and note
388 the error. */
389
390 if (f.host_find_failed_syntax)
391 {
392 addr->message = string_sprintf("mail domain \"%s\" is syntactically "
393 "invalid", h.name);
394 return DECLINE;
395 }
396 }
397
398 /* If the original domain name has been changed as a result of the host lookup,
399 set up a child address for rerouting and request header rewrites if so
400 configured. Then yield REROUTED. However, if the only change is a change of
401 case in the domain name, which some resolvers yield (others don't), just change
402 the domain name in the original address so that the official version is used in
403 RCPT commands. */
404
405 if (Ustrcmp(addr->domain, fully_qualified_name) != 0)
406 {
407 if (strcmpic(addr->domain, fully_qualified_name) == 0)
408 {
409 uschar *at = Ustrrchr(addr->address, '@');
410 memcpy(at+1, fully_qualified_name, Ustrlen(at+1));
411 }
412 else
413 {
414 rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new);
415 return REROUTED;
416 }
417 }
418
419 /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX
420 records with the lowest numbered one pointing to a host with an IP address that
421 is set on one of the interfaces of this machine, or found A records or got
422 addresses from gethostbyname() that contain one for this machine. This can
423 happen quite legitimately if the original name was a shortened form of a
424 domain, but we will have picked that up already via the name change test above.
425
426 Otherwise, the action to be taken can be configured by the self option, the
427 handling of which is in a separate function, as it is also required for other
428 routers. */
429
430 if (rc == HOST_FOUND_LOCAL)
431 {
432 rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite,
433 rblock->self, addr_new);
434 if (rc != OK) return rc;
435 }
436
437 /* Otherwise, insist on being a secondary MX if so configured */
438
439 else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed))
440 {
441 DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n");
442 return DECLINE;
443 }
444
445 /* Set up the errors address, if any. */
446
447 rc = rf_get_errors_address(addr, rblock, verify, &addr->prop.errors_address);
448 if (rc != OK) return rc;
449
450 /* Set up the additional and removable headers for this address. */
451
452 rc = rf_get_munge_headers(addr, rblock, &addr->prop.extra_headers,
453 &addr->prop.remove_headers);
454 if (rc != OK) return rc;
455
456 /* Get store in which to preserve the original host item, chained on
457 to the address. */
458
459 addr->host_list = store_get(sizeof(host_item), FALSE);
460 addr->host_list[0] = h;
461
462 /* Fill in the transport and queue the address for delivery. */
463
464 if (!rf_get_transport(rblock->transport_name, &(rblock->transport),
465 addr, rblock->name, NULL))
466 return DEFER;
467
468 addr->transport = rblock->transport;
469
470 return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)?
471 OK : DEFER;
472 }
473
474 #endif /*!MACRO_PREDEF*/
475 /* End of routers/dnslookup.c */
476 /* vi: aw ai sw=2
477 */