Merge remote-tracking branch 'github/pr/34'
[exim.git] / src / src / lookups / dnsdb.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2015 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 #include "../exim.h"
9 #include "lf_functions.h"
10
11
12
13 /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
14 header files. */
15
16 #ifndef T_TXT
17 #define T_TXT 16
18 #endif
19
20 /* Many systems do not have T_SPF. */
21 #ifndef T_SPF
22 #define T_SPF 99
23 #endif
24
25 /* New TLSA record for DANE */
26 #ifndef T_TLSA
27 #define T_TLSA 52
28 #endif
29
30 /* Table of recognized DNS record types and their integer values. */
31
32 static const char *type_names[] = {
33 "a",
34 #if HAVE_IPV6
35 "a+",
36 "aaaa",
37 #endif
38 "cname",
39 "csa",
40 "mx",
41 "mxh",
42 "ns",
43 "ptr",
44 "soa",
45 "spf",
46 "srv",
47 "tlsa",
48 "txt",
49 "zns"
50 };
51
52 static int type_values[] = {
53 T_A,
54 #if HAVE_IPV6
55 T_ADDRESSES, /* Private type for AAAA + A */
56 T_AAAA,
57 #endif
58 T_CNAME,
59 T_CSA, /* Private type for "Client SMTP Authorization". */
60 T_MX,
61 T_MXH, /* Private type for "MX hostnames" */
62 T_NS,
63 T_PTR,
64 T_SOA,
65 T_SPF,
66 T_SRV,
67 T_TLSA,
68 T_TXT,
69 T_ZNS /* Private type for "zone nameservers" */
70 };
71
72
73 /*************************************************
74 * Open entry point *
75 *************************************************/
76
77 /* See local README for interface description. */
78
79 static void *
80 dnsdb_open(uschar *filename, uschar **errmsg)
81 {
82 filename = filename; /* Keep picky compilers happy */
83 errmsg = errmsg; /* Ditto */
84 return (void *)(-1); /* Any non-0 value */
85 }
86
87
88
89 /*************************************************
90 * Find entry point for dnsdb *
91 *************************************************/
92
93 /* See local README for interface description. The query in the "keystring" may
94 consist of a number of parts.
95
96 (a) If the first significant character is '>' then the next character is the
97 separator character that is used when multiple records are found. The default
98 separator is newline.
99
100 (b) If the next character is ',' then the next character is the separator
101 character used for multiple items of text in "TXT" records. Alternatively,
102 if the next character is ';' then these multiple items are concatenated with
103 no separator. With neither of these options specified, only the first item
104 is output. Similarly for "SPF" records, but the default for joining multiple
105 items in one SPF record is the empty string, for direct concatenation.
106
107 (c) Options, all comma-terminated, in any order. Any unrecognised option
108 terminates option processing. Recognised options are:
109
110 - 'defer_FOO': set the defer behaviour to FOO. The possible behaviours are:
111 'strict', where any defer causes the whole lookup to defer; 'lax', where a defer
112 causes the whole lookup to defer only if none of the DNS queries succeeds; and
113 'never', where all defers are as if the lookup failed. The default is 'lax'.
114
115 - 'dnssec_FOO', with 'strict', 'lax' and 'never' (default). The meanings are
116 require, try and don't-try dnssec respectively.
117
118 - 'retrans_VAL', set the timeout value. VAL is an Exim time specification
119 (eg "5s"). The default is set by the main configuration option 'dns_retrans'.
120
121 - 'retry_VAL', set the retry count on timeouts. VAL is an integer. The
122 default is set by the main configuration option "dns_retry".
123
124 (d) If the next sequence of characters is a sequence of letters and digits
125 followed by '=', it is interpreted as the name of the DNS record type. The
126 default is "TXT".
127
128 (e) Then there follows list of domain names. This is a generalized Exim list,
129 which may start with '<' in order to set a specific separator. The default
130 separator, as always, is colon. */
131
132 static int
133 dnsdb_find(void *handle, uschar *filename, const uschar *keystring, int length,
134 uschar **result, uschar **errmsg, uint *do_cache)
135 {
136 int rc;
137 int size = 256;
138 int ptr = 0;
139 int sep = 0;
140 int defer_mode = PASS;
141 int dnssec_mode = OK;
142 int save_retrans = dns_retrans;
143 int save_retry = dns_retry;
144 int type;
145 int failrc = FAIL;
146 const uschar *outsep = CUS"\n";
147 const uschar *outsep2 = NULL;
148 uschar *equals, *domain, *found;
149
150 /* Because we're the working in the search pool, we try to reclaim as much
151 store as possible later, so we preallocate the result here */
152
153 uschar *yield = store_get(size);
154
155 dns_record *rr;
156 dns_answer dnsa;
157 dns_scan dnss;
158
159 handle = handle; /* Keep picky compilers happy */
160 filename = filename;
161 length = length;
162 do_cache = do_cache;
163
164 /* If the string starts with '>' we change the output separator.
165 If it's followed by ';' or ',' we set the TXT output separator. */
166
167 while (isspace(*keystring)) keystring++;
168 if (*keystring == '>')
169 {
170 outsep = keystring + 1;
171 keystring += 2;
172 if (*keystring == ',')
173 {
174 outsep2 = keystring + 1;
175 keystring += 2;
176 }
177 else if (*keystring == ';')
178 {
179 outsep2 = US"";
180 keystring++;
181 }
182 while (isspace(*keystring)) keystring++;
183 }
184
185 /* Check for a modifier keyword. */
186
187 for (;;)
188 {
189 if (strncmpic(keystring, US"defer_", 6) == 0)
190 {
191 keystring += 6;
192 if (strncmpic(keystring, US"strict", 6) == 0)
193 { defer_mode = DEFER; keystring += 6; }
194 else if (strncmpic(keystring, US"lax", 3) == 0)
195 { defer_mode = PASS; keystring += 3; }
196 else if (strncmpic(keystring, US"never", 5) == 0)
197 { defer_mode = OK; keystring += 5; }
198 else
199 {
200 *errmsg = US"unsupported dnsdb defer behaviour";
201 return DEFER;
202 }
203 }
204 else if (strncmpic(keystring, US"dnssec_", 7) == 0)
205 {
206 keystring += 7;
207 if (strncmpic(keystring, US"strict", 6) == 0)
208 { dnssec_mode = DEFER; keystring += 6; }
209 else if (strncmpic(keystring, US"lax", 3) == 0)
210 { dnssec_mode = PASS; keystring += 3; }
211 else if (strncmpic(keystring, US"never", 5) == 0)
212 { dnssec_mode = OK; keystring += 5; }
213 else
214 {
215 *errmsg = US"unsupported dnsdb dnssec behaviour";
216 return DEFER;
217 }
218 }
219 else if (strncmpic(keystring, US"retrans_", 8) == 0)
220 {
221 int timeout_sec;
222 if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
223 {
224 *errmsg = US"unsupported dnsdb timeout value";
225 return DEFER;
226 }
227 dns_retrans = timeout_sec;
228 while (*keystring != ',') keystring++;
229 }
230 else if (strncmpic(keystring, US"retry_", 6) == 0)
231 {
232 int retries;
233 if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
234 {
235 *errmsg = US"unsupported dnsdb retry count";
236 return DEFER;
237 }
238 dns_retry = retries;
239 }
240 else
241 break;
242
243 while (isspace(*keystring)) keystring++;
244 if (*keystring++ != ',')
245 {
246 *errmsg = US"dnsdb modifier syntax error";
247 return DEFER;
248 }
249 while (isspace(*keystring)) keystring++;
250 }
251
252 /* Figure out the "type" value if it is not T_TXT.
253 If the keystring contains an = this must be preceded by a valid type name. */
254
255 type = T_TXT;
256 if ((equals = Ustrchr(keystring, '=')) != NULL)
257 {
258 int i, len;
259 uschar *tend = equals;
260
261 while (tend > keystring && isspace(tend[-1])) tend--;
262 len = tend - keystring;
263
264 for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
265 {
266 if (len == Ustrlen(type_names[i]) &&
267 strncmpic(keystring, US type_names[i], len) == 0)
268 {
269 type = type_values[i];
270 break;
271 }
272 }
273
274 if (i >= sizeof(type_names)/sizeof(uschar *))
275 {
276 *errmsg = US"unsupported DNS record type";
277 return DEFER;
278 }
279
280 keystring = equals + 1;
281 while (isspace(*keystring)) keystring++;
282 }
283
284 /* Initialize the resolver in case this is the first time it has been used. */
285
286 dns_init(FALSE, FALSE, dnssec_mode != OK);
287
288 /* The remainder of the string must be a list of domains. As long as the lookup
289 for at least one of them succeeds, we return success. Failure means that none
290 of them were found.
291
292 The original implementation did not support a list of domains. Adding the list
293 feature is compatible, except in one case: when PTR records are being looked up
294 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
295 here: If the type is PTR and no list separator is specified, and the entire
296 remaining string is valid as an IP address, set an impossible separator so that
297 it is treated as one item. */
298
299 if (type == T_PTR && keystring[0] != '<' &&
300 string_is_ip_address(keystring, NULL) != 0)
301 sep = -1;
302
303 /* SPF strings should be concatenated without a separator, thus make
304 it the default if not defined (see RFC 4408 section 3.1.3).
305 Multiple SPF records are forbidden (section 3.1.2) but are currently
306 not handled specially, thus they are concatenated with \n by default.
307 MX priority and value are space-separated by default.
308 SRV and TLSA record parts are space-separated by default. */
309
310 if (!outsep2) switch(type)
311 {
312 case T_SPF: outsep2 = US""; break;
313 case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
314 }
315
316 /* Now scan the list and do a lookup for each item */
317
318 while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
319 {
320 uschar rbuffer[256];
321 int searchtype = (type == T_CSA)? T_SRV : /* record type we want */
322 (type == T_MXH)? T_MX :
323 (type == T_ZNS)? T_NS : type;
324
325 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
326 key if the original is an IP address (some experimental protocols are using
327 PTR records for different purposes where the key string is a host name, and
328 Exim's extended CSA can be keyed by domains or IP addresses). This code for
329 doing the reversal is now in a separate function. */
330
331 if ((type == T_PTR || type == T_CSA) &&
332 string_is_ip_address(domain, NULL) != 0)
333 {
334 dns_build_reverse(domain, rbuffer);
335 domain = rbuffer;
336 }
337
338 do
339 {
340 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
341
342 /* Do the lookup and sort out the result. There are four special types that
343 are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
344 The first two are handled in a special lookup function so that the facility
345 could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
346 over the types of A lookup. T_MXH affects only what happens later on in
347 this function, but for tidiness it is handled by the "special". If the
348 lookup fails, continue with the next domain. In the case of DEFER, adjust
349 the final "nothing found" result, but carry on to the next domain. */
350
351 found = domain;
352 #if HAVE_IPV6
353 if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
354 {
355 if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
356 else if (searchtype == T_AAAA) searchtype = T_A;
357 rc = dns_special_lookup(&dnsa, domain, searchtype, CUSS &found);
358 }
359 else
360 #endif
361 rc = dns_special_lookup(&dnsa, domain, type, CUSS &found);
362
363 lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
364 : dns_is_secure(&dnsa) ? US"yes" : US"no";
365
366 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
367 if ( rc != DNS_SUCCEED
368 || (dnssec_mode == DEFER && !dns_is_secure(&dnsa))
369 )
370 {
371 if (defer_mode == DEFER)
372 {
373 dns_retrans = save_retrans;
374 dns_retry = save_retry;
375 dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
376 return DEFER; /* always defer */
377 }
378 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
379 continue; /* treat defer as fail */
380 }
381
382
383 /* Search the returned records */
384
385 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
386 rr != NULL;
387 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
388 {
389 if (rr->type != searchtype) continue;
390
391 if (*do_cache > rr->ttl)
392 *do_cache = rr->ttl;
393
394 if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
395 {
396 dns_address *da;
397 for (da = dns_address_from_rr(&dnsa, rr); da; da = da->next)
398 {
399 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
400 yield = string_cat(yield, &size, &ptr, da->address,
401 Ustrlen(da->address));
402 }
403 continue;
404 }
405
406 /* Other kinds of record just have one piece of data each, but there may be
407 several of them, of course. */
408
409 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
410
411 if (type == T_TXT || type == T_SPF)
412 {
413 if (outsep2 == NULL)
414 {
415 /* output only the first item of data */
416 yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
417 (rr->data)[0]);
418 }
419 else
420 {
421 /* output all items */
422 int data_offset = 0;
423 while (data_offset < rr->size)
424 {
425 uschar chunk_len = (rr->data)[data_offset++];
426 if (outsep2[0] != '\0' && data_offset != 1)
427 yield = string_cat(yield, &size, &ptr, outsep2, 1);
428 yield = string_cat(yield, &size, &ptr,
429 (uschar *)((rr->data)+data_offset), chunk_len);
430 data_offset += chunk_len;
431 }
432 }
433 }
434 else if (type == T_TLSA)
435 {
436 uint8_t usage, selector, matching_type;
437 uint16_t i, payload_length;
438 uschar s[MAX_TLSA_EXPANDED_SIZE];
439 uschar * sp = s;
440 uschar * p = US rr->data;
441
442 usage = *p++;
443 selector = *p++;
444 matching_type = *p++;
445 /* What's left after removing the first 3 bytes above */
446 payload_length = rr->size - 3;
447 sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
448 selector, *outsep2, matching_type, *outsep2);
449 /* Now append the cert/identifier, one hex char at a time */
450 for (i=0;
451 i < payload_length && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4);
452 i++)
453 sp += sprintf(CS sp, "%02x", (unsigned char)p[i]);
454
455 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
456 }
457 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
458 {
459 int priority, weight, port;
460 uschar s[264];
461 uschar * p = US rr->data;
462
463 switch (type)
464 {
465 case T_MXH:
466 /* mxh ignores the priority number and includes only the hostnames */
467 GETSHORT(priority, p);
468 break;
469
470 case T_MX:
471 GETSHORT(priority, p);
472 sprintf(CS s, "%d%c", priority, *outsep2);
473 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
474 break;
475
476 case T_SRV:
477 GETSHORT(priority, p);
478 GETSHORT(weight, p);
479 GETSHORT(port, p);
480 sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
481 weight, *outsep2, port, *outsep2);
482 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
483 break;
484
485 case T_CSA:
486 /* See acl_verify_csa() for more comments about CSA. */
487 GETSHORT(priority, p);
488 GETSHORT(weight, p);
489 GETSHORT(port, p);
490
491 if (priority != 1) continue; /* CSA version must be 1 */
492
493 /* If the CSA record we found is not the one we asked for, analyse
494 the subdomain assertions in the port field, else analyse the direct
495 authorization status in the weight field. */
496
497 if (Ustrcmp(found, domain) != 0)
498 {
499 if (port & 1) *s = 'X'; /* explicit authorization required */
500 else *s = '?'; /* no subdomain assertions here */
501 }
502 else
503 {
504 if (weight < 2) *s = 'N'; /* not authorized */
505 else if (weight == 2) *s = 'Y'; /* authorized */
506 else if (weight == 3) *s = '?'; /* unauthorizable */
507 else continue; /* invalid */
508 }
509
510 s[1] = ' ';
511 yield = string_cat(yield, &size, &ptr, s, 2);
512 break;
513
514 default:
515 break;
516 }
517
518 /* GETSHORT() has advanced the pointer to the target domain. */
519
520 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
521 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
522
523 /* If an overlong response was received, the data will have been
524 truncated and dn_expand may fail. */
525
526 if (rc < 0)
527 {
528 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
529 "domain=%s", dns_text_type(type), domain);
530 break;
531 }
532 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
533
534 if (type == T_SOA && outsep2 != NULL)
535 {
536 unsigned long serial, refresh, retry, expire, minimum;
537
538 p += rc;
539 yield = string_cat(yield, &size, &ptr, outsep2, 1);
540
541 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
542 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
543 if (rc < 0)
544 {
545 log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
546 "domain=%s", dns_text_type(type), domain);
547 break;
548 }
549 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
550
551 p += rc;
552 GETLONG(serial, p); GETLONG(refresh, p);
553 GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
554 sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
555 *outsep2, serial, *outsep2, refresh,
556 *outsep2, retry, *outsep2, expire, *outsep2, minimum);
557 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
558 }
559 }
560 } /* Loop for list of returned records */
561
562 /* Loop for set of A-lookupu types */
563 } while (type == T_ADDRESSES && searchtype != T_A);
564
565 } /* Loop for list of domains */
566
567 /* Reclaim unused memory */
568
569 store_reset(yield + ptr + 1);
570
571 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
572 zero and return the result. */
573
574 dns_retrans = save_retrans;
575 dns_retry = save_retry;
576 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
577
578 if (ptr == 0) return failrc;
579 yield[ptr] = 0;
580 *result = yield;
581 return OK;
582 }
583
584
585
586 /*************************************************
587 * Version reporting entry point *
588 *************************************************/
589
590 /* See local README for interface description. */
591
592 #include "../version.h"
593
594 void
595 dnsdb_version_report(FILE *f)
596 {
597 #ifdef DYNLOOKUP
598 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
599 #endif
600 }
601
602
603 static lookup_info _lookup_info = {
604 US"dnsdb", /* lookup name */
605 lookup_querystyle, /* query style */
606 dnsdb_open, /* open function */
607 NULL, /* check function */
608 dnsdb_find, /* find function */
609 NULL, /* no close function */
610 NULL, /* no tidy function */
611 NULL, /* no quoting function */
612 dnsdb_version_report /* version reporting */
613 };
614
615 #ifdef DYNLOOKUP
616 #define dnsdb_lookup_module_info _lookup_module_info
617 #endif
618
619 static lookup_info *_lookup_list[] = { &_lookup_info };
620 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
621
622 /* vi: aw ai sw=2
623 */
624 /* End of lookups/dnsdb.c */