aa5b924c78c558c6f8b40adc042c87220d289022
[exim.git] / src / src / routers / dnslookup.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2009 */
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 { "dnssec_request_domains", opt_stringptr,
22 (void *)(offsetof(dnslookup_router_options_block, dnssec_request_domains)) },
23 { "dnssec_require_domains", opt_stringptr,
24 (void *)(offsetof(dnslookup_router_options_block, dnssec_require_domains)) },
25 { "mx_domains", opt_stringptr,
26 (void *)(offsetof(dnslookup_router_options_block, mx_domains)) },
27 { "mx_fail_domains", opt_stringptr,
28 (void *)(offsetof(dnslookup_router_options_block, mx_fail_domains)) },
29 { "qualify_single", opt_bool,
30 (void *)(offsetof(dnslookup_router_options_block, qualify_single)) },
31 { "rewrite_headers", opt_bool,
32 (void *)(offsetof(dnslookup_router_options_block, rewrite_headers)) },
33 { "same_domain_copy_routing", opt_bool|opt_public,
34 (void *)(offsetof(router_instance, same_domain_copy_routing)) },
35 { "search_parents", opt_bool,
36 (void *)(offsetof(dnslookup_router_options_block, search_parents)) },
37 { "srv_fail_domains", opt_stringptr,
38 (void *)(offsetof(dnslookup_router_options_block, srv_fail_domains)) },
39 { "widen_domains", opt_stringptr,
40 (void *)(offsetof(dnslookup_router_options_block, widen_domains)) }
41 };
42
43 /* Size of the options list. An extern variable has to be used so that its
44 address can appear in the tables drtables.c. */
45
46 int dnslookup_router_options_count =
47 sizeof(dnslookup_router_options)/sizeof(optionlist);
48
49 /* Default private options block for the dnslookup router. */
50
51 dnslookup_router_options_block dnslookup_router_option_defaults = {
52 FALSE, /* check_secondary_mx */
53 TRUE, /* qualify_single */
54 FALSE, /* search_parents */
55 TRUE, /* rewrite_headers */
56 NULL, /* widen_domains */
57 NULL, /* mx_domains */
58 NULL, /* mx_fail_domains */
59 NULL, /* srv_fail_domains */
60 NULL, /* check_srv */
61 NULL, /* dnssec_request_domains */
62 NULL /* dnssec_require_domains */
63 };
64
65
66
67 /*************************************************
68 * Initialization entry point *
69 *************************************************/
70
71 /* Called for each instance, after its options have been read, to enable
72 consistency checks to be done, or anything else that needs to be set up. */
73
74 void
75 dnslookup_router_init(router_instance *rblock)
76 {
77 /*
78 dnslookup_router_options_block *ob =
79 (dnslookup_router_options_block *)(rblock->options_block);
80 */
81 rblock = rblock;
82 }
83
84
85
86 /*************************************************
87 * Main entry point *
88 *************************************************/
89
90 /* See local README for interface details. This router returns:
91
92 DECLINE
93 . the domain does not exist in the DNS
94 . MX records point to non-existent hosts (including RHS = IP address)
95 . a single SRV record has a host name of "." (=> no service)
96 . syntactically invalid mail domain
97 . check_secondary_mx set, and local host not in host list
98
99 DEFER
100 . lookup defer for mx_domains
101 . timeout etc on DNS lookup
102 . verifying the errors address caused a deferment or a big disaster such
103 as an expansion failure (rf_get_errors_address)
104 . expanding a headers_{add,remove} string caused a deferment or another
105 expansion error (rf_get_munge_headers)
106 . a problem in rf_get_transport: no transport when one is needed;
107 failed to expand dynamic transport; failed to find dynamic transport
108 . failure to expand or find a uid/gid (rf_get_ugid via rf_queue_add)
109 . self = "freeze", self = "defer"
110
111 PASS
112 . timeout etc on DNS lookup and pass_on_timeout set
113 . self = "pass"
114
115 REROUTED
116 . routed to local host, but name was expanded by DNS lookup, so a
117 re-routing should take place
118 . self = "reroute"
119
120 In both cases the new address will have been set up as a child
121
122 FAIL
123 . self = "fail"
124
125 OK
126 added address to addr_local or addr_remote, as appropriate for the
127 type of transport; this includes the self="send" case.
128 */
129
130 int
131 dnslookup_router_entry(
132 router_instance *rblock, /* data for this instantiation */
133 address_item *addr, /* address we are working on */
134 struct passwd *pw, /* passwd entry after check_local_user */
135 int verify, /* v_none/v_recipient/v_sender/v_expn */
136 address_item **addr_local, /* add it to this if it's local */
137 address_item **addr_remote, /* add it to this if it's remote */
138 address_item **addr_new, /* put new addresses on here */
139 address_item **addr_succeed) /* put old address here on success */
140 {
141 host_item h;
142 int rc;
143 int widen_sep = 0;
144 int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A;
145 dnslookup_router_options_block *ob =
146 (dnslookup_router_options_block *)(rblock->options_block);
147 uschar *srv_service = NULL;
148 uschar *widen = NULL;
149 const uschar *pre_widen = addr->domain;
150 const uschar *post_widen = NULL;
151 const uschar *fully_qualified_name;
152 const uschar *listptr;
153 uschar widen_buffer[256];
154
155 addr_new = addr_new; /* Keep picky compilers happy */
156 addr_succeed = addr_succeed;
157
158 DEBUG(D_route)
159 debug_printf("%s router called for %s\n domain = %s\n",
160 rblock->name, addr->address, addr->domain);
161
162 /* If an SRV check is required, expand the service name */
163
164 if (ob->check_srv != NULL)
165 {
166 srv_service = expand_string(ob->check_srv);
167 if (srv_service == NULL && !expand_string_forcedfail)
168 {
169 addr->message = string_sprintf("%s router: failed to expand \"%s\": %s",
170 rblock->name, ob->check_srv, expand_string_message);
171 return DEFER;
172 }
173 else whichrrs |= HOST_FIND_BY_SRV;
174 }
175
176 /* Set up the first of any widening domains. The code further down copes with
177 either pre- or post-widening, but at present there is no way to turn on
178 pre-widening, as actually doing so seems like a rather bad idea, and nobody has
179 requested it. Pre-widening would cause local abbreviated names to take
180 precedence over global names. For example, if the domain is "xxx.ch" it might
181 be something in the "ch" toplevel domain, but it also might be xxx.ch.xyz.com.
182 The choice of pre- or post-widening affects which takes precedence. If ever
183 somebody comes up with some kind of requirement for pre-widening, presumably
184 with some conditions under which it is done, it can be selected here.
185
186 The rewrite_headers option works only when routing an address at transport
187 time, because the alterations to the headers are not persistent so must be
188 worked out immediately before they are used. Sender addresses are routed for
189 verification purposes, but never at transport time, so any header changes that
190 you might expect as a result of sender domain widening do not occur. Therefore
191 we do not perform widening when verifying sender addresses; however, widening
192 sender addresses is OK if we do not have to rewrite the headers. A corollary
193 of this is that if the current address is not the original address, then it
194 does not appear in the message header so it is also OK to widen. The
195 suppression of widening for sender addresses is silent because it is the
196 normal desirable behaviour. */
197
198 if (ob->widen_domains != NULL &&
199 (verify != v_sender || !ob->rewrite_headers || addr->parent != NULL))
200 {
201 listptr = ob->widen_domains;
202 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
203 sizeof(widen_buffer));
204
205 /****
206 if (some condition requiring pre-widening)
207 {
208 post_widen = pre_widen;
209 pre_widen = NULL;
210 }
211 ****/
212 }
213
214 /* Loop to cope with explicit widening of domains as configured. This code
215 copes with widening that may happen before or after the original name. The
216 decision as to which is taken above. */
217
218 for (;;)
219 {
220 int flags = whichrrs;
221 BOOL removed = FALSE;
222
223 if (pre_widen != NULL)
224 {
225 h.name = pre_widen;
226 pre_widen = NULL;
227 }
228 else if (widen != NULL)
229 {
230 h.name = string_sprintf("%s.%s", addr->domain, widen);
231 widen = string_nextinlist(&listptr, &widen_sep, widen_buffer,
232 sizeof(widen_buffer));
233 DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name,
234 addr->domain, h.name);
235 }
236 else if (post_widen != NULL)
237 {
238 h.name = post_widen;
239 post_widen = NULL;
240 DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n",
241 rblock->name, h.name);
242 }
243 else return DECLINE;
244
245 /* Set up the rest of the initial host item. Others may get chained on if
246 there is more than one IP address. We set it up here instead of outside the
247 loop so as to re-initialize if a previous try succeeded but was rejected
248 because of not having an MX record. */
249
250 h.next = NULL;
251 h.address = NULL;
252 h.port = PORT_NONE;
253 h.mx = MX_NONE;
254 h.status = hstatus_unknown;
255 h.why = hwhy_unknown;
256 h.last_try = 0;
257
258 /* Unfortunately, we cannot set the mx_only option in advance, because the
259 DNS lookup may extend an unqualified name. Therefore, we must do the test
260 subsequently. We use the same logic as that for widen_domains above to avoid
261 requesting a header rewrite that cannot work. */
262
263 if (verify != v_sender || !ob->rewrite_headers || addr->parent != NULL)
264 {
265 if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE;
266 if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS;
267 }
268
269 rc = host_find_bydns(&h, CUS rblock->ignore_target_hosts, flags, srv_service,
270 ob->srv_fail_domains, ob->mx_fail_domains,
271 ob->dnssec_request_domains, ob->dnssec_require_domains,
272 &fully_qualified_name, &removed);
273 if (removed) setflag(addr, af_local_host_removed);
274
275 /* If host found with only address records, test for the domain's being in
276 the mx_domains list. Note that this applies also to SRV records; the name of
277 the option is historical. */
278
279 if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 &&
280 ob->mx_domains != NULL)
281 {
282 switch(match_isinlist(fully_qualified_name,
283 (const uschar **)&(ob->mx_domains), 0,
284 &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL))
285 {
286 case DEFER:
287 addr->message = US"lookup defer for mx_domains";
288 return DEFER;
289
290 case OK:
291 DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n",
292 rblock->name, fully_qualified_name);
293 continue;
294 }
295 }
296
297 /* Deferral returns forthwith, and anything other than failure breaks the
298 loop. */
299
300 if (rc == HOST_FIND_AGAIN)
301 {
302 if (rblock->pass_on_timeout)
303 {
304 DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n",
305 rblock->name);
306 return PASS;
307 }
308 addr->message = US"host lookup did not complete";
309 return DEFER;
310 }
311
312 if (rc != HOST_FIND_FAILED) break;
313
314 /* Check to see if the failure is the result of MX records pointing to
315 non-existent domains, and if so, set an appropriate error message; the case
316 of an MX or SRV record pointing to "." is another special case that we can
317 detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in
318 this case don't do the widening. We need check only the first host to see if
319 its MX has been filled in, but there is no address, because if there were any
320 usable addresses returned, we would not have had HOST_FIND_FAILED.
321
322 As a common cause of this problem is MX records with IP addresses on the
323 RHS, give a special message in this case. */
324
325 if (h.mx >= 0 && h.address == NULL)
326 {
327 setflag(addr, af_pass_message); /* This is not a security risk */
328 if (h.name[0] == 0)
329 addr->message = US"an MX or SRV record indicated no SMTP service";
330 else
331 {
332 addr->message = US"all relevant MX records point to non-existent hosts";
333 if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0)
334 {
335 addr->user_message =
336 string_sprintf("It appears that the DNS operator for %s\n"
337 "has installed an invalid MX record with an IP address\n"
338 "instead of a domain name on the right hand side.", addr->domain);
339 addr->message = string_sprintf("%s or (invalidly) to IP addresses",
340 addr->message);
341 }
342 }
343 return DECLINE;
344 }
345
346 /* If there's a syntax error, do not continue with any widening, and note
347 the error. */
348
349 if (host_find_failed_syntax)
350 {
351 addr->message = string_sprintf("mail domain \"%s\" is syntactically "
352 "invalid", h.name);
353 return DECLINE;
354 }
355 }
356
357 /* If the original domain name has been changed as a result of the host lookup,
358 set up a child address for rerouting and request header rewrites if so
359 configured. Then yield REROUTED. However, if the only change is a change of
360 case in the domain name, which some resolvers yield (others don't), just change
361 the domain name in the original address so that the official version is used in
362 RCPT commands. */
363
364 if (Ustrcmp(addr->domain, fully_qualified_name) != 0)
365 {
366 if (strcmpic(addr->domain, fully_qualified_name) == 0)
367 {
368 uschar *at = Ustrrchr(addr->address, '@');
369 memcpy(at+1, fully_qualified_name, Ustrlen(at+1));
370 }
371 else
372 {
373 rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new);
374 return REROUTED;
375 }
376 }
377
378 /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX
379 records with the lowest numbered one pointing to a host with an IP address that
380 is set on one of the interfaces of this machine, or found A records or got
381 addresses from gethostbyname() that contain one for this machine. This can
382 happen quite legitimately if the original name was a shortened form of a
383 domain, but we will have picked that up already via the name change test above.
384
385 Otherwise, the action to be taken can be configured by the self option, the
386 handling of which is in a separate function, as it is also required for other
387 routers. */
388
389 if (rc == HOST_FOUND_LOCAL)
390 {
391 rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite,
392 rblock->self, addr_new);
393 if (rc != OK) return rc;
394 }
395
396 /* Otherwise, insist on being a secondary MX if so configured */
397
398 else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed))
399 {
400 DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n");
401 return DECLINE;
402 }
403
404 /* Set up the errors address, if any. */
405
406 rc = rf_get_errors_address(addr, rblock, verify, &(addr->p.errors_address));
407 if (rc != OK) return rc;
408
409 /* Set up the additional and removeable headers for this address. */
410
411 rc = rf_get_munge_headers(addr, rblock, &(addr->p.extra_headers),
412 &(addr->p.remove_headers));
413 if (rc != OK) return rc;
414
415 /* Get store in which to preserve the original host item, chained on
416 to the address. */
417
418 addr->host_list = store_get(sizeof(host_item));
419 addr->host_list[0] = h;
420
421 /* Fill in the transport and queue the address for delivery. */
422
423 if (!rf_get_transport(rblock->transport_name, &(rblock->transport),
424 addr, rblock->name, NULL))
425 return DEFER;
426
427 addr->transport = rblock->transport;
428
429 return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)?
430 OK : DEFER;
431 }
432
433 /* End of routers/dnslookup.c */