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0756eb3c PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
0a49a7a4 | 5 | /* Copyright (c) University of Cambridge 1995 - 2009 */ |
0756eb3c PH |
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)) }, | |
8c51eead JH |
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)) }, | |
0756eb3c PH |
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 */ | |
8c51eead JH |
60 | NULL, /* check_srv */ |
61 | NULL, /* dnssec_request_domains */ | |
62 | NULL /* dnssec_require_domains */ | |
0756eb3c PH |
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 */ | |
fd6de02e | 135 | int verify, /* v_none/v_recipient/v_sender/v_expn */ |
0756eb3c PH |
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; | |
55414b25 JH |
149 | const uschar *pre_widen = addr->domain; |
150 | const uschar *post_widen = NULL; | |
151 | const uschar *fully_qualified_name; | |
152 | const uschar *listptr; | |
0756eb3c PH |
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 | |
fd6de02e PH |
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 | |
a5f65aa4 TF |
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)) | |
0756eb3c PH |
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 | |
a7fdad5b TF |
260 | subsequently. We use the same logic as that for widen_domains above to avoid |
261 | requesting a header rewrite that cannot work. */ | |
0756eb3c | 262 | |
a7fdad5b TF |
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 | } | |
0756eb3c | 268 | |
55414b25 | 269 | rc = host_find_bydns(&h, CUS rblock->ignore_target_hosts, flags, srv_service, |
8c51eead JH |
270 | ob->srv_fail_domains, ob->mx_fail_domains, |
271 | ob->dnssec_request_domains, ob->dnssec_require_domains, | |
272 | &fully_qualified_name, &removed); | |
0756eb3c PH |
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 | { | |
55414b25 JH |
282 | switch(match_isinlist(fully_qualified_name, |
283 | (const uschar **)&(ob->mx_domains), 0, | |
0756eb3c PH |
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 | ||
66afa403 TF |
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 | |
0756eb3c PH |
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 | { | |
ca02eafb | 327 | setflag(addr, af_pass_message); /* This is not a security risk */ |
0756eb3c | 328 | if (h.name[0] == 0) |
66afa403 | 329 | addr->message = US"an MX or SRV record indicated no SMTP service"; |
0756eb3c PH |
330 | else |
331 | { | |
332 | addr->message = US"all relevant MX records point to non-existent hosts"; | |
7e66e54d | 333 | if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0) |
0756eb3c PH |
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 */ |