Commit | Line | Data |
---|---|---|
0756eb3c PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
66387a73 | 5 | /* Copyright (c) University of Cambridge 1995 - 2018 */ |
1e1ddfac | 6 | /* Copyright (c) The Exim Maintainers 2020 */ |
0756eb3c PH |
7 | /* See the file NOTICE for conditions of use and distribution. */ |
8 | ||
9 | #include "../exim.h" | |
10 | #include "rf_functions.h" | |
11 | #include "dnslookup.h" | |
12 | ||
13 | ||
14 | ||
15 | /* Options specific to the dnslookup router. */ | |
13a4b4c1 | 16 | #define LOFF(field) OPT_OFF(dnslookup_router_options_block, field) |
0756eb3c PH |
17 | |
18 | optionlist dnslookup_router_options[] = { | |
13a4b4c1 JH |
19 | { "check_secondary_mx", opt_bool, LOFF(check_secondary_mx) }, |
20 | { "check_srv", opt_stringptr, LOFF(check_srv) }, | |
21 | { "fail_defer_domains", opt_stringptr, LOFF(fail_defer_domains) }, | |
22 | { "ipv4_only", opt_stringptr, LOFF(ipv4_only) }, | |
23 | { "ipv4_prefer", opt_stringptr, LOFF(ipv4_prefer) }, | |
24 | { "mx_domains", opt_stringptr, LOFF(mx_domains) }, | |
25 | { "mx_fail_domains", opt_stringptr, LOFF(mx_fail_domains) }, | |
26 | { "qualify_single", opt_bool, LOFF(qualify_single) }, | |
27 | { "rewrite_headers", opt_bool, LOFF(rewrite_headers) }, | |
28 | { "same_domain_copy_routing", opt_bool|opt_public, OPT_OFF(router_instance, same_domain_copy_routing) }, | |
29 | { "search_parents", opt_bool, LOFF(search_parents) }, | |
30 | { "srv_fail_domains", opt_stringptr, LOFF(srv_fail_domains) }, | |
31 | { "widen_domains", opt_stringptr, LOFF(widen_domains) } | |
0756eb3c PH |
32 | }; |
33 | ||
34 | /* Size of the options list. An extern variable has to be used so that its | |
35 | address can appear in the tables drtables.c. */ | |
36 | ||
37 | int dnslookup_router_options_count = | |
38 | sizeof(dnslookup_router_options)/sizeof(optionlist); | |
39 | ||
d185889f JH |
40 | |
41 | #ifdef MACRO_PREDEF | |
42 | ||
43 | /* Dummy entries */ | |
44 | dnslookup_router_options_block dnslookup_router_option_defaults = {0}; | |
45 | void dnslookup_router_init(router_instance *rblock) {} | |
46 | int dnslookup_router_entry(router_instance *rblock, address_item *addr, | |
47 | struct passwd *pw, int verify, address_item **addr_local, | |
48 | address_item **addr_remote, address_item **addr_new, | |
cab0c277 | 49 | address_item **addr_succeed) {return 0;} |
d185889f JH |
50 | |
51 | #else /*!MACRO_PREDEF*/ | |
52 | ||
53 | ||
54 | ||
55 | ||
0756eb3c PH |
56 | /* Default private options block for the dnslookup router. */ |
57 | ||
58 | dnslookup_router_options_block dnslookup_router_option_defaults = { | |
66387a73 JH |
59 | .check_secondary_mx = FALSE, |
60 | .qualify_single = TRUE, | |
61 | .search_parents = FALSE, | |
62 | .rewrite_headers = TRUE, | |
63 | .widen_domains = NULL, | |
64 | .mx_domains = NULL, | |
65 | .mx_fail_domains = NULL, | |
66 | .srv_fail_domains = NULL, | |
67 | .check_srv = NULL, | |
68 | .fail_defer_domains = NULL, | |
69 | .ipv4_only = NULL, | |
70 | .ipv4_prefer = NULL, | |
0756eb3c PH |
71 | }; |
72 | ||
73 | ||
74 | ||
75 | /************************************************* | |
76 | * Initialization entry point * | |
77 | *************************************************/ | |
78 | ||
79 | /* Called for each instance, after its options have been read, to enable | |
80 | consistency checks to be done, or anything else that needs to be set up. */ | |
81 | ||
82 | void | |
83 | dnslookup_router_init(router_instance *rblock) | |
84 | { | |
85 | /* | |
86 | dnslookup_router_options_block *ob = | |
87 | (dnslookup_router_options_block *)(rblock->options_block); | |
88 | */ | |
89 | rblock = rblock; | |
90 | } | |
91 | ||
92 | ||
93 | ||
94 | /************************************************* | |
95 | * Main entry point * | |
96 | *************************************************/ | |
97 | ||
98 | /* See local README for interface details. This router returns: | |
99 | ||
100 | DECLINE | |
101 | . the domain does not exist in the DNS | |
102 | . MX records point to non-existent hosts (including RHS = IP address) | |
103 | . a single SRV record has a host name of "." (=> no service) | |
104 | . syntactically invalid mail domain | |
105 | . check_secondary_mx set, and local host not in host list | |
106 | ||
107 | DEFER | |
108 | . lookup defer for mx_domains | |
109 | . timeout etc on DNS lookup | |
110 | . verifying the errors address caused a deferment or a big disaster such | |
111 | as an expansion failure (rf_get_errors_address) | |
112 | . expanding a headers_{add,remove} string caused a deferment or another | |
113 | expansion error (rf_get_munge_headers) | |
114 | . a problem in rf_get_transport: no transport when one is needed; | |
115 | failed to expand dynamic transport; failed to find dynamic transport | |
116 | . failure to expand or find a uid/gid (rf_get_ugid via rf_queue_add) | |
117 | . self = "freeze", self = "defer" | |
118 | ||
119 | PASS | |
120 | . timeout etc on DNS lookup and pass_on_timeout set | |
121 | . self = "pass" | |
122 | ||
123 | REROUTED | |
124 | . routed to local host, but name was expanded by DNS lookup, so a | |
125 | re-routing should take place | |
126 | . self = "reroute" | |
127 | ||
128 | In both cases the new address will have been set up as a child | |
129 | ||
130 | FAIL | |
131 | . self = "fail" | |
132 | ||
133 | OK | |
134 | added address to addr_local or addr_remote, as appropriate for the | |
135 | type of transport; this includes the self="send" case. | |
136 | */ | |
137 | ||
138 | int | |
139 | dnslookup_router_entry( | |
140 | router_instance *rblock, /* data for this instantiation */ | |
141 | address_item *addr, /* address we are working on */ | |
142 | struct passwd *pw, /* passwd entry after check_local_user */ | |
fd6de02e | 143 | int verify, /* v_none/v_recipient/v_sender/v_expn */ |
0756eb3c PH |
144 | address_item **addr_local, /* add it to this if it's local */ |
145 | address_item **addr_remote, /* add it to this if it's remote */ | |
146 | address_item **addr_new, /* put new addresses on here */ | |
147 | address_item **addr_succeed) /* put old address here on success */ | |
148 | { | |
149 | host_item h; | |
150 | int rc; | |
151 | int widen_sep = 0; | |
66387a73 | 152 | int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A | HOST_FIND_BY_AAAA; |
0756eb3c PH |
153 | dnslookup_router_options_block *ob = |
154 | (dnslookup_router_options_block *)(rblock->options_block); | |
155 | uschar *srv_service = NULL; | |
156 | uschar *widen = NULL; | |
55414b25 JH |
157 | const uschar *pre_widen = addr->domain; |
158 | const uschar *post_widen = NULL; | |
159 | const uschar *fully_qualified_name; | |
160 | const uschar *listptr; | |
0756eb3c PH |
161 | uschar widen_buffer[256]; |
162 | ||
163 | addr_new = addr_new; /* Keep picky compilers happy */ | |
164 | addr_succeed = addr_succeed; | |
165 | ||
166 | DEBUG(D_route) | |
167 | debug_printf("%s router called for %s\n domain = %s\n", | |
168 | rblock->name, addr->address, addr->domain); | |
169 | ||
170 | /* If an SRV check is required, expand the service name */ | |
171 | ||
bd4ece7d | 172 | if (ob->check_srv) |
0756eb3c | 173 | { |
bd4ece7d | 174 | if ( !(srv_service = expand_string(ob->check_srv)) |
8768d548 | 175 | && !f.expand_string_forcedfail) |
0756eb3c PH |
176 | { |
177 | addr->message = string_sprintf("%s router: failed to expand \"%s\": %s", | |
178 | rblock->name, ob->check_srv, expand_string_message); | |
179 | return DEFER; | |
180 | } | |
181 | else whichrrs |= HOST_FIND_BY_SRV; | |
182 | } | |
183 | ||
184 | /* Set up the first of any widening domains. The code further down copes with | |
185 | either pre- or post-widening, but at present there is no way to turn on | |
186 | pre-widening, as actually doing so seems like a rather bad idea, and nobody has | |
187 | requested it. Pre-widening would cause local abbreviated names to take | |
188 | precedence over global names. For example, if the domain is "xxx.ch" it might | |
189 | be something in the "ch" toplevel domain, but it also might be xxx.ch.xyz.com. | |
190 | The choice of pre- or post-widening affects which takes precedence. If ever | |
191 | somebody comes up with some kind of requirement for pre-widening, presumably | |
fd6de02e PH |
192 | with some conditions under which it is done, it can be selected here. |
193 | ||
194 | The rewrite_headers option works only when routing an address at transport | |
195 | time, because the alterations to the headers are not persistent so must be | |
196 | worked out immediately before they are used. Sender addresses are routed for | |
197 | verification purposes, but never at transport time, so any header changes that | |
198 | you might expect as a result of sender domain widening do not occur. Therefore | |
199 | we do not perform widening when verifying sender addresses; however, widening | |
a5f65aa4 TF |
200 | sender addresses is OK if we do not have to rewrite the headers. A corollary |
201 | of this is that if the current address is not the original address, then it | |
202 | does not appear in the message header so it is also OK to widen. The | |
203 | suppression of widening for sender addresses is silent because it is the | |
204 | normal desirable behaviour. */ | |
205 | ||
bd4ece7d JH |
206 | if ( ob->widen_domains |
207 | && (verify != v_sender || !ob->rewrite_headers || addr->parent)) | |
0756eb3c PH |
208 | { |
209 | listptr = ob->widen_domains; | |
210 | widen = string_nextinlist(&listptr, &widen_sep, widen_buffer, | |
211 | sizeof(widen_buffer)); | |
212 | ||
213 | /**** | |
214 | if (some condition requiring pre-widening) | |
215 | { | |
216 | post_widen = pre_widen; | |
217 | pre_widen = NULL; | |
218 | } | |
219 | ****/ | |
220 | } | |
221 | ||
222 | /* Loop to cope with explicit widening of domains as configured. This code | |
223 | copes with widening that may happen before or after the original name. The | |
224 | decision as to which is taken above. */ | |
225 | ||
226 | for (;;) | |
227 | { | |
228 | int flags = whichrrs; | |
229 | BOOL removed = FALSE; | |
230 | ||
bd4ece7d | 231 | if (pre_widen) |
0756eb3c PH |
232 | { |
233 | h.name = pre_widen; | |
234 | pre_widen = NULL; | |
235 | } | |
bd4ece7d | 236 | else if (widen) |
0756eb3c PH |
237 | { |
238 | h.name = string_sprintf("%s.%s", addr->domain, widen); | |
239 | widen = string_nextinlist(&listptr, &widen_sep, widen_buffer, | |
240 | sizeof(widen_buffer)); | |
241 | DEBUG(D_route) debug_printf("%s router widened %s to %s\n", rblock->name, | |
242 | addr->domain, h.name); | |
243 | } | |
bd4ece7d | 244 | else if (post_widen) |
0756eb3c PH |
245 | { |
246 | h.name = post_widen; | |
247 | post_widen = NULL; | |
248 | DEBUG(D_route) debug_printf("%s router trying %s after widening failed\n", | |
249 | rblock->name, h.name); | |
250 | } | |
251 | else return DECLINE; | |
252 | ||
66387a73 JH |
253 | /* Check if we must request only. or prefer, ipv4 */ |
254 | ||
255 | if ( ob->ipv4_only | |
256 | && expand_check_condition(ob->ipv4_only, rblock->name, US"router")) | |
257 | flags = flags & ~HOST_FIND_BY_AAAA | HOST_FIND_IPV4_ONLY; | |
8768d548 | 258 | else if (f.search_find_defer) |
66387a73 JH |
259 | return DEFER; |
260 | if ( ob->ipv4_prefer | |
261 | && expand_check_condition(ob->ipv4_prefer, rblock->name, US"router")) | |
262 | flags |= HOST_FIND_IPV4_FIRST; | |
8768d548 | 263 | else if (f.search_find_defer) |
66387a73 JH |
264 | return DEFER; |
265 | ||
0756eb3c PH |
266 | /* Set up the rest of the initial host item. Others may get chained on if |
267 | there is more than one IP address. We set it up here instead of outside the | |
268 | loop so as to re-initialize if a previous try succeeded but was rejected | |
269 | because of not having an MX record. */ | |
270 | ||
271 | h.next = NULL; | |
272 | h.address = NULL; | |
273 | h.port = PORT_NONE; | |
274 | h.mx = MX_NONE; | |
275 | h.status = hstatus_unknown; | |
276 | h.why = hwhy_unknown; | |
277 | h.last_try = 0; | |
278 | ||
279 | /* Unfortunately, we cannot set the mx_only option in advance, because the | |
280 | DNS lookup may extend an unqualified name. Therefore, we must do the test | |
b09c1793 | 281 | subsequently. We use the same logic as that for widen_domains above to avoid |
a7fdad5b | 282 | requesting a header rewrite that cannot work. */ |
0756eb3c | 283 | |
bd4ece7d | 284 | if (verify != v_sender || !ob->rewrite_headers || addr->parent) |
a7fdad5b TF |
285 | { |
286 | if (ob->qualify_single) flags |= HOST_FIND_QUALIFY_SINGLE; | |
287 | if (ob->search_parents) flags |= HOST_FIND_SEARCH_PARENTS; | |
288 | } | |
0756eb3c | 289 | |
66387a73 JH |
290 | rc = host_find_bydns(&h, CUS rblock->ignore_target_hosts, flags, |
291 | srv_service, ob->srv_fail_domains, ob->mx_fail_domains, | |
8ac90765 JH |
292 | &rblock->dnssec, |
293 | &fully_qualified_name, &removed); | |
294 | ||
0756eb3c PH |
295 | if (removed) setflag(addr, af_local_host_removed); |
296 | ||
297 | /* If host found with only address records, test for the domain's being in | |
298 | the mx_domains list. Note that this applies also to SRV records; the name of | |
299 | the option is historical. */ | |
300 | ||
301 | if ((rc == HOST_FOUND || rc == HOST_FOUND_LOCAL) && h.mx < 0 && | |
bd4ece7d | 302 | ob->mx_domains) |
55414b25 | 303 | switch(match_isinlist(fully_qualified_name, |
bd4ece7d | 304 | CUSS &(ob->mx_domains), 0, |
0756eb3c PH |
305 | &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL)) |
306 | { | |
307 | case DEFER: | |
308 | addr->message = US"lookup defer for mx_domains"; | |
309 | return DEFER; | |
310 | ||
311 | case OK: | |
312 | DEBUG(D_route) debug_printf("%s router rejected %s: no MX record(s)\n", | |
313 | rblock->name, fully_qualified_name); | |
314 | continue; | |
315 | } | |
0756eb3c PH |
316 | |
317 | /* Deferral returns forthwith, and anything other than failure breaks the | |
318 | loop. */ | |
319 | ||
2546388c JH |
320 | if (rc == HOST_FIND_SECURITY) |
321 | { | |
322 | addr->message = US"host lookup done insecurely"; | |
323 | return DEFER; | |
324 | } | |
0756eb3c PH |
325 | if (rc == HOST_FIND_AGAIN) |
326 | { | |
327 | if (rblock->pass_on_timeout) | |
328 | { | |
329 | DEBUG(D_route) debug_printf("%s router timed out, and pass_on_timeout is set\n", | |
330 | rblock->name); | |
331 | return PASS; | |
332 | } | |
333 | addr->message = US"host lookup did not complete"; | |
334 | return DEFER; | |
335 | } | |
336 | ||
337 | if (rc != HOST_FIND_FAILED) break; | |
338 | ||
1435d4b2 JH |
339 | if (ob->fail_defer_domains) |
340 | switch(match_isinlist(fully_qualified_name, | |
341 | CUSS &ob->fail_defer_domains, 0, | |
342 | &domainlist_anchor, addr->domain_cache, MCL_DOMAIN, TRUE, NULL)) | |
343 | { | |
344 | case DEFER: | |
345 | addr->message = US"lookup defer for fail_defer_domains option"; | |
346 | return DEFER; | |
347 | ||
348 | case OK: | |
349 | DEBUG(D_route) debug_printf("%s router: matched fail_defer_domains\n", | |
350 | rblock->name); | |
351 | addr->message = US"missing MX, or all MXs point to missing A records," | |
352 | " and defer requested"; | |
353 | return DEFER; | |
354 | } | |
66afa403 TF |
355 | /* Check to see if the failure is the result of MX records pointing to |
356 | non-existent domains, and if so, set an appropriate error message; the case | |
357 | of an MX or SRV record pointing to "." is another special case that we can | |
0756eb3c PH |
358 | detect. Otherwise "unknown mail domain" is used, which is confusing. Also, in |
359 | this case don't do the widening. We need check only the first host to see if | |
360 | its MX has been filled in, but there is no address, because if there were any | |
361 | usable addresses returned, we would not have had HOST_FIND_FAILED. | |
362 | ||
363 | As a common cause of this problem is MX records with IP addresses on the | |
364 | RHS, give a special message in this case. */ | |
365 | ||
366 | if (h.mx >= 0 && h.address == NULL) | |
367 | { | |
ca02eafb | 368 | setflag(addr, af_pass_message); /* This is not a security risk */ |
0756eb3c | 369 | if (h.name[0] == 0) |
66afa403 | 370 | addr->message = US"an MX or SRV record indicated no SMTP service"; |
0756eb3c PH |
371 | else |
372 | { | |
bd4ece7d | 373 | addr->basic_errno = ERRNO_UNKNOWNHOST; |
0756eb3c | 374 | addr->message = US"all relevant MX records point to non-existent hosts"; |
7e66e54d | 375 | if (!allow_mx_to_ip && string_is_ip_address(h.name, NULL) != 0) |
0756eb3c PH |
376 | { |
377 | addr->user_message = | |
378 | string_sprintf("It appears that the DNS operator for %s\n" | |
379 | "has installed an invalid MX record with an IP address\n" | |
380 | "instead of a domain name on the right hand side.", addr->domain); | |
381 | addr->message = string_sprintf("%s or (invalidly) to IP addresses", | |
382 | addr->message); | |
383 | } | |
384 | } | |
385 | return DECLINE; | |
386 | } | |
387 | ||
388 | /* If there's a syntax error, do not continue with any widening, and note | |
389 | the error. */ | |
390 | ||
8768d548 | 391 | if (f.host_find_failed_syntax) |
0756eb3c PH |
392 | { |
393 | addr->message = string_sprintf("mail domain \"%s\" is syntactically " | |
394 | "invalid", h.name); | |
395 | return DECLINE; | |
396 | } | |
397 | } | |
398 | ||
399 | /* If the original domain name has been changed as a result of the host lookup, | |
400 | set up a child address for rerouting and request header rewrites if so | |
401 | configured. Then yield REROUTED. However, if the only change is a change of | |
402 | case in the domain name, which some resolvers yield (others don't), just change | |
403 | the domain name in the original address so that the official version is used in | |
404 | RCPT commands. */ | |
405 | ||
406 | if (Ustrcmp(addr->domain, fully_qualified_name) != 0) | |
407 | { | |
408 | if (strcmpic(addr->domain, fully_qualified_name) == 0) | |
409 | { | |
410 | uschar *at = Ustrrchr(addr->address, '@'); | |
411 | memcpy(at+1, fully_qualified_name, Ustrlen(at+1)); | |
412 | } | |
413 | else | |
414 | { | |
415 | rf_change_domain(addr, fully_qualified_name, ob->rewrite_headers, addr_new); | |
416 | return REROUTED; | |
417 | } | |
418 | } | |
419 | ||
420 | /* If the yield is HOST_FOUND_LOCAL, the remote domain name either found MX | |
421 | records with the lowest numbered one pointing to a host with an IP address that | |
422 | is set on one of the interfaces of this machine, or found A records or got | |
423 | addresses from gethostbyname() that contain one for this machine. This can | |
424 | happen quite legitimately if the original name was a shortened form of a | |
425 | domain, but we will have picked that up already via the name change test above. | |
426 | ||
427 | Otherwise, the action to be taken can be configured by the self option, the | |
428 | handling of which is in a separate function, as it is also required for other | |
429 | routers. */ | |
430 | ||
431 | if (rc == HOST_FOUND_LOCAL) | |
432 | { | |
433 | rc = rf_self_action(addr, &h, rblock->self_code, rblock->self_rewrite, | |
434 | rblock->self, addr_new); | |
435 | if (rc != OK) return rc; | |
436 | } | |
437 | ||
438 | /* Otherwise, insist on being a secondary MX if so configured */ | |
439 | ||
440 | else if (ob->check_secondary_mx && !testflag(addr, af_local_host_removed)) | |
441 | { | |
442 | DEBUG(D_route) debug_printf("check_secondary_mx set and local host not secondary\n"); | |
443 | return DECLINE; | |
444 | } | |
445 | ||
446 | /* Set up the errors address, if any. */ | |
447 | ||
d43cbe25 | 448 | rc = rf_get_errors_address(addr, rblock, verify, &addr->prop.errors_address); |
0756eb3c PH |
449 | if (rc != OK) return rc; |
450 | ||
aded2255 | 451 | /* Set up the additional and removable headers for this address. */ |
0756eb3c | 452 | |
d43cbe25 JH |
453 | rc = rf_get_munge_headers(addr, rblock, &addr->prop.extra_headers, |
454 | &addr->prop.remove_headers); | |
0756eb3c PH |
455 | if (rc != OK) return rc; |
456 | ||
457 | /* Get store in which to preserve the original host item, chained on | |
458 | to the address. */ | |
459 | ||
f3ebb786 | 460 | addr->host_list = store_get(sizeof(host_item), FALSE); |
0756eb3c PH |
461 | addr->host_list[0] = h; |
462 | ||
463 | /* Fill in the transport and queue the address for delivery. */ | |
464 | ||
465 | if (!rf_get_transport(rblock->transport_name, &(rblock->transport), | |
466 | addr, rblock->name, NULL)) | |
467 | return DEFER; | |
468 | ||
469 | addr->transport = rblock->transport; | |
470 | ||
471 | return rf_queue_add(addr, addr_local, addr_remote, rblock, pw)? | |
472 | OK : DEFER; | |
473 | } | |
474 | ||
d185889f | 475 | #endif /*!MACRO_PREDEF*/ |
0756eb3c | 476 | /* End of routers/dnslookup.c */ |
bd4ece7d JH |
477 | /* vi: aw ai sw=2 |
478 | */ |