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184e8823 | 1 | /* $Cambridge: exim/src/src/routers/dnslookup.c,v 1.11 2007/01/08 10:50:20 ph10 Exp $ */ |
0756eb3c PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
184e8823 | 7 | /* Copyright (c) University of Cambridge 1995 - 2007 */ |
0756eb3c PH |
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 */ | |
fd6de02e | 131 | int verify, /* v_none/v_recipient/v_sender/v_expn */ |
0756eb3c PH |
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 | |
fd6de02e PH |
180 | with some conditions under which it is done, it can be selected here. |
181 | ||
182 | The rewrite_headers option works only when routing an address at transport | |
183 | time, because the alterations to the headers are not persistent so must be | |
184 | worked out immediately before they are used. Sender addresses are routed for | |
185 | verification purposes, but never at transport time, so any header changes that | |
186 | you might expect as a result of sender domain widening do not occur. Therefore | |
187 | we do not perform widening when verifying sender addresses; however, widening | |
a5f65aa4 TF |
188 | sender addresses is OK if we do not have to rewrite the headers. A corollary |
189 | of this is that if the current address is not the original address, then it | |
190 | does not appear in the message header so it is also OK to widen. The | |
191 | suppression of widening for sender addresses is silent because it is the | |
192 | normal desirable behaviour. */ | |
193 | ||
194 | if (ob->widen_domains != NULL && | |
195 | (verify != v_sender || !ob->rewrite_headers || addr->parent != NULL)) | |
0756eb3c PH |
196 | { |
197 | listptr = ob->widen_domains; | |
198 | widen = string_nextinlist(&listptr, &widen_sep, widen_buffer, | |
199 | sizeof(widen_buffer)); | |
200 | ||
201 | /**** | |
202 | if (some condition requiring pre-widening) | |
203 | { | |
204 | post_widen = pre_widen; | |
205 | pre_widen = NULL; | |
206 | } | |
207 | ****/ | |
208 | } | |
209 | ||
210 | /* Loop to cope with explicit widening of domains as configured. This code | |
211 | copes with widening that may happen before or after the original name. The | |
212 | decision as to which is taken above. */ | |
213 | ||
214 | for (;;) | |
215 | { | |
216 | int flags = whichrrs; | |
217 | BOOL removed = FALSE; | |
218 | ||
219 | if (pre_widen != NULL) | |
220 | { | |
221 | h.name = pre_widen; | |
222 | pre_widen = NULL; | |
223 | } | |
224 | else if (widen != NULL) | |
225 | { | |
226 | h.name = string_sprintf("%s.%s", addr->domain, widen); | |
227 | widen = string_nextinlist(&listptr, &widen_sep, widen_buffer, | |
228 | sizeof(widen_buffer)); | |
229 | DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name, | |
230 | addr->domain, h.name); | |
231 | } | |
232 | else if (post_widen != NULL) | |
233 | { | |
234 | h.name = post_widen; | |
235 | post_widen = NULL; | |
236 | DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n", | |
237 | rblock->name, h.name); | |
238 | } | |
239 | else return DECLINE; | |
240 | ||
241 | /* Set up the rest of the initial host item. Others may get chained on if | |
242 | there is more than one IP address. We set it up here instead of outside the | |
243 | loop so as to re-initialize if a previous try succeeded but was rejected | |
244 | because of not having an MX record. */ | |
245 | ||
246 | h.next = NULL; | |
247 | h.address = NULL; | |
248 | h.port = PORT_NONE; | |
249 | h.mx = MX_NONE; | |
250 | h.status = hstatus_unknown; | |
251 | h.why = hwhy_unknown; | |
252 | h.last_try = 0; | |
253 | ||
254 | /* Unfortunately, we cannot set the mx_only option in advance, because the | |
255 | DNS lookup may extend an unqualified name. Therefore, we must do the test | |
a7fdad5b TF |
256 | subsequently. We use the same logic as that for widen_domains above to avoid |
257 | requesting a header rewrite that cannot work. */ | |
0756eb3c | 258 | |
a7fdad5b TF |
259 | if (verify != v_sender || !ob->rewrite_headers || addr->parent != NULL) |
260 | { | |
261 | if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE; | |
262 | if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS; | |
263 | } | |
0756eb3c PH |
264 | |
265 | rc = host_find_bydns(&h, rblock->ignore_target_hosts, flags, srv_service, | |
266 | ob->srv_fail_domains, ob->mx_fail_domains, &fully_qualified_name, &removed); | |
267 | if (removed) setflag(addr, af_local_host_removed); | |
268 | ||
269 | /* If host found with only address records, test for the domain's being in | |
270 | the mx_domains list. Note that this applies also to SRV records; the name of | |
271 | the option is historical. */ | |
272 | ||
273 | if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 && | |
274 | ob->mx_domains != NULL) | |
275 | { | |
276 | switch(match_isinlist(fully_qualified_name, &(ob->mx_domains), 0, | |
277 | &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL)) | |
278 | { | |
279 | case DEFER: | |
280 | addr->message = US"lookup defer for mx_domains"; | |
281 | return DEFER; | |
282 | ||
283 | case OK: | |
284 | DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n", | |
285 | rblock->name, fully_qualified_name); | |
286 | continue; | |
287 | } | |
288 | } | |
289 | ||
290 | /* Deferral returns forthwith, and anything other than failure breaks the | |
291 | loop. */ | |
292 | ||
293 | if (rc == HOST_FIND_AGAIN) | |
294 | { | |
295 | if (rblock->pass_on_timeout) | |
296 | { | |
297 | DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n", | |
298 | rblock->name); | |
299 | return PASS; | |
300 | } | |
301 | addr->message = US"host lookup did not complete"; | |
302 | return DEFER; | |
303 | } | |
304 | ||
305 | if (rc != HOST_FIND_FAILED) break; | |
306 | ||
66afa403 TF |
307 | /* Check to see if the failure is the result of MX records pointing to |
308 | non-existent domains, and if so, set an appropriate error message; the case | |
309 | of an MX or SRV record pointing to "." is another special case that we can | |
0756eb3c PH |
310 | detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in |
311 | this case don't do the widening. We need check only the first host to see if | |
312 | its MX has been filled in, but there is no address, because if there were any | |
313 | usable addresses returned, we would not have had HOST_FIND_FAILED. | |
314 | ||
315 | As a common cause of this problem is MX records with IP addresses on the | |
316 | RHS, give a special message in this case. */ | |
317 | ||
318 | if (h.mx >= 0 && h.address == NULL) | |
319 | { | |
ca02eafb | 320 | setflag(addr, af_pass_message); /* This is not a security risk */ |
0756eb3c | 321 | if (h.name[0] == 0) |
66afa403 | 322 | addr->message = US"an MX or SRV record indicated no SMTP service"; |
0756eb3c PH |
323 | else |
324 | { | |
325 | addr->message = US"all relevant MX records point to non-existent hosts"; | |
7e66e54d | 326 | if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0) |
0756eb3c PH |
327 | { |
328 | addr->user_message = | |
329 | string_sprintf("It appears that the DNS operator for %s\n" | |
330 | "has installed an invalid MX record with an IP address\n" | |
331 | "instead of a domain name on the right hand side.", addr->domain); | |
332 | addr->message = string_sprintf("%s or (invalidly) to IP addresses", | |
333 | addr->message); | |
334 | } | |
335 | } | |
336 | return DECLINE; | |
337 | } | |
338 | ||
339 | /* If there's a syntax error, do not continue with any widening, and note | |
340 | the error. */ | |
341 | ||
342 | if (host_find_failed_syntax) | |
343 | { | |
344 | addr->message = string_sprintf("mail domain \"%s\" is syntactically " | |
345 | "invalid", h.name); | |
346 | return DECLINE; | |
347 | } | |
348 | } | |
349 | ||
350 | /* If the original domain name has been changed as a result of the host lookup, | |
351 | set up a child address for rerouting and request header rewrites if so | |
352 | configured. Then yield REROUTED. However, if the only change is a change of | |
353 | case in the domain name, which some resolvers yield (others don't), just change | |
354 | the domain name in the original address so that the official version is used in | |
355 | RCPT commands. */ | |
356 | ||
357 | if (Ustrcmp(addr->domain, fully_qualified_name) != 0) | |
358 | { | |
359 | if (strcmpic(addr->domain, fully_qualified_name) == 0) | |
360 | { | |
361 | uschar *at = Ustrrchr(addr->address, '@'); | |
362 | memcpy(at+1, fully_qualified_name, Ustrlen(at+1)); | |
363 | } | |
364 | else | |
365 | { | |
366 | rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new); | |
367 | return REROUTED; | |
368 | } | |
369 | } | |
370 | ||
371 | /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX | |
372 | records with the lowest numbered one pointing to a host with an IP address that | |
373 | is set on one of the interfaces of this machine, or found A records or got | |
374 | addresses from gethostbyname() that contain one for this machine. This can | |
375 | happen quite legitimately if the original name was a shortened form of a | |
376 | domain, but we will have picked that up already via the name change test above. | |
377 | ||
378 | Otherwise, the action to be taken can be configured by the self option, the | |
379 | handling of which is in a separate function, as it is also required for other | |
380 | routers. */ | |
381 | ||
382 | if (rc == HOST_FOUND_LOCAL) | |
383 | { | |
384 | rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite, | |
385 | rblock->self, addr_new); | |
386 | if (rc != OK) return rc; | |
387 | } | |
388 | ||
389 | /* Otherwise, insist on being a secondary MX if so configured */ | |
390 | ||
391 | else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed)) | |
392 | { | |
393 | DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n"); | |
394 | return DECLINE; | |
395 | } | |
396 | ||
397 | /* Set up the errors address, if any. */ | |
398 | ||
399 | rc = rf_get_errors_address(addr, rblock, verify, &(addr->p.errors_address)); | |
400 | if (rc != OK) return rc; | |
401 | ||
402 | /* Set up the additional and removeable headers for this address. */ | |
403 | ||
404 | rc = rf_get_munge_headers(addr, rblock, &(addr->p.extra_headers), | |
405 | &(addr->p.remove_headers)); | |
406 | if (rc != OK) return rc; | |
407 | ||
408 | /* Get store in which to preserve the original host item, chained on | |
409 | to the address. */ | |
410 | ||
411 | addr->host_list = store_get(sizeof(host_item)); | |
412 | addr->host_list[0] = h; | |
413 | ||
414 | /* Fill in the transport and queue the address for delivery. */ | |
415 | ||
416 | if (!rf_get_transport(rblock->transport_name, &(rblock->transport), | |
417 | addr, rblock->name, NULL)) | |
418 | return DEFER; | |
419 | ||
420 | addr->transport = rblock->transport; | |
421 | ||
422 | return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)? | |
423 | OK : DEFER; | |
424 | } | |
425 | ||
426 | /* End of routers/dnslookup.c */ |