ef3376505c504793295cbe366acdc3ed82fd38a7
[exim.git] / src / src / lookups / dnsdb.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2014 */
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 #ifdef SUPPORT_A6
38 "a6",
39 #endif
40 #endif
41 "cname",
42 "csa",
43 "mx",
44 "mxh",
45 "ns",
46 "ptr",
47 "spf",
48 "srv",
49 "tlsa",
50 "txt",
51 "zns"
52 };
53
54 static int type_values[] = {
55 T_A,
56 #if HAVE_IPV6
57 T_APL, /* Private type for AAAA + A */
58 T_AAAA,
59 #ifdef SUPPORT_A6
60 T_A6,
61 #endif
62 #endif
63 T_CNAME,
64 T_CSA, /* Private type for "Client SMTP Authorization". */
65 T_MX,
66 T_MXH, /* Private type for "MX hostnames" */
67 T_NS,
68 T_PTR,
69 T_SPF,
70 T_SRV,
71 T_TLSA,
72 T_TXT,
73 T_ZNS /* Private type for "zone nameservers" */
74 };
75
76
77 /*************************************************
78 * Open entry point *
79 *************************************************/
80
81 /* See local README for interface description. */
82
83 static void *
84 dnsdb_open(uschar *filename, uschar **errmsg)
85 {
86 filename = filename; /* Keep picky compilers happy */
87 errmsg = errmsg; /* Ditto */
88 return (void *)(-1); /* Any non-0 value */
89 }
90
91
92
93 /*************************************************
94 * Find entry point for dnsdb *
95 *************************************************/
96
97 /* See local README for interface description. The query in the "keystring" may
98 consist of a number of parts.
99
100 (a) If the first significant character is '>' then the next character is the
101 separator character that is used when multiple records are found. The default
102 separator is newline.
103
104 (b) If the next character is ',' then the next character is the separator
105 character used for multiple items of text in "TXT" records. Alternatively,
106 if the next character is ';' then these multiple items are concatenated with
107 no separator. With neither of these options specified, only the first item
108 is output. Similarly for "SPF" records, but the default for joining multiple
109 items in one SPF record is the empty string, for direct concatenation.
110
111 (c) If the next sequence of characters is 'defer_FOO' followed by a comma,
112 the defer behaviour is set to FOO. The possible behaviours are: 'strict', where
113 any defer causes the whole lookup to defer; 'lax', where a defer causes the
114 whole lookup to defer only if none of the DNS queries succeeds; and 'never',
115 where all defers are as if the lookup failed. The default is 'lax'.
116
117 (d) Another optional comma-sep field: 'dnssec_FOO', with 'strict', 'lax'
118 and 'never' (default); can appear before or after (c). The meanings are
119 require, try and don't-try dnssec respectively.
120
121 (e) If the next sequence of characters is a sequence of letters and digits
122 followed by '=', it is interpreted as the name of the DNS record type. The
123 default is "TXT".
124
125 (f) Then there follows list of domain names. This is a generalized Exim list,
126 which may start with '<' in order to set a specific separator. The default
127 separator, as always, is colon. */
128
129 static int
130 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
131 uschar **result, uschar **errmsg, BOOL *do_cache)
132 {
133 int rc;
134 int size = 256;
135 int ptr = 0;
136 int sep = 0;
137 int defer_mode = PASS;
138 int dnssec_mode = OK;
139 int type;
140 int failrc = FAIL;
141 uschar *outsep = US"\n";
142 uschar *outsep2 = NULL;
143 uschar *equals, *domain, *found;
144 uschar buffer[256];
145
146 /* Because we're the working in the search pool, we try to reclaim as much
147 store as possible later, so we preallocate the result here */
148
149 uschar *yield = store_get(size);
150
151 dns_record *rr;
152 dns_answer dnsa;
153 dns_scan dnss;
154
155 handle = handle; /* Keep picky compilers happy */
156 filename = filename;
157 length = length;
158 do_cache = do_cache;
159
160 /* If the string starts with '>' we change the output separator.
161 If it's followed by ';' or ',' we set the TXT output separator. */
162
163 while (isspace(*keystring)) keystring++;
164 if (*keystring == '>')
165 {
166 outsep = keystring + 1;
167 keystring += 2;
168 if (*keystring == ',')
169 {
170 outsep2 = keystring + 1;
171 keystring += 2;
172 }
173 else if (*keystring == ';')
174 {
175 outsep2 = US"";
176 keystring++;
177 }
178 while (isspace(*keystring)) keystring++;
179 }
180
181 /* Check for a modifier keyword. */
182
183 while ( strncmpic(keystring, US"defer_", 6) == 0
184 || strncmpic(keystring, US"dnssec_", 7) == 0
185 )
186 {
187 if (strncmpic(keystring, US"defer_", 6) == 0)
188 {
189 keystring += 6;
190 if (strncmpic(keystring, US"strict", 6) == 0)
191 {
192 defer_mode = DEFER;
193 keystring += 6;
194 }
195 else if (strncmpic(keystring, US"lax", 3) == 0)
196 {
197 defer_mode = PASS;
198 keystring += 3;
199 }
200 else if (strncmpic(keystring, US"never", 5) == 0)
201 {
202 defer_mode = OK;
203 keystring += 5;
204 }
205 else
206 {
207 *errmsg = US"unsupported dnsdb defer behaviour";
208 return DEFER;
209 }
210 }
211 else
212 {
213 keystring += 7;
214 if (strncmpic(keystring, US"strict", 6) == 0)
215 {
216 dnssec_mode = DEFER;
217 keystring += 6;
218 }
219 else if (strncmpic(keystring, US"lax", 3) == 0)
220 {
221 dnssec_mode = PASS;
222 keystring += 3;
223 }
224 else if (strncmpic(keystring, US"never", 5) == 0)
225 {
226 dnssec_mode = OK;
227 keystring += 5;
228 }
229 else
230 {
231 *errmsg = US"unsupported dnsdb dnssec behaviour";
232 return DEFER;
233 }
234 }
235 while (isspace(*keystring)) keystring++;
236 if (*keystring++ != ',')
237 {
238 *errmsg = US"dnsdb modifier syntax error";
239 return DEFER;
240 }
241 while (isspace(*keystring)) keystring++;
242 }
243
244 /* Figure out the "type" value if it is not T_TXT.
245 If the keystring contains an = this must be preceded by a valid type name. */
246
247 type = T_TXT;
248 if ((equals = Ustrchr(keystring, '=')) != NULL)
249 {
250 int i, len;
251 uschar *tend = equals;
252
253 while (tend > keystring && isspace(tend[-1])) tend--;
254 len = tend - keystring;
255
256 for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
257 {
258 if (len == Ustrlen(type_names[i]) &&
259 strncmpic(keystring, US type_names[i], len) == 0)
260 {
261 type = type_values[i];
262 break;
263 }
264 }
265
266 if (i >= sizeof(type_names)/sizeof(uschar *))
267 {
268 *errmsg = US"unsupported DNS record type";
269 return DEFER;
270 }
271
272 keystring = equals + 1;
273 while (isspace(*keystring)) keystring++;
274 }
275
276 /* Initialize the resolver in case this is the first time it has been used. */
277
278 dns_init(FALSE, FALSE, dnssec_mode != OK);
279
280 /* The remainder of the string must be a list of domains. As long as the lookup
281 for at least one of them succeeds, we return success. Failure means that none
282 of them were found.
283
284 The original implementation did not support a list of domains. Adding the list
285 feature is compatible, except in one case: when PTR records are being looked up
286 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
287 here: If the type is PTR and no list separator is specified, and the entire
288 remaining string is valid as an IP address, set an impossible separator so that
289 it is treated as one item. */
290
291 if (type == T_PTR && keystring[0] != '<' &&
292 string_is_ip_address(keystring, NULL) != 0)
293 sep = -1;
294
295 /* SPF strings should be concatenated without a separator, thus make
296 it the default if not defined (see RFC 4408 section 3.1.3).
297 Multiple SPF records are forbidden (section 3.1.2) but are currently
298 not handled specially, thus they are concatenated with \n by default. */
299
300 if (type == T_SPF && outsep2 == NULL)
301 outsep2 = US"";
302
303 /* Now scan the list and do a lookup for each item */
304
305 while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer)))
306 != NULL)
307 {
308 uschar rbuffer[256];
309 int searchtype = (type == T_CSA)? T_SRV : /* record type we want */
310 (type == T_MXH)? T_MX :
311 (type == T_ZNS)? T_NS : type;
312
313 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
314 key if the original is an IP address (some experimental protocols are using
315 PTR records for different purposes where the key string is a host name, and
316 Exim's extended CSA can be keyed by domains or IP addresses). This code for
317 doing the reversal is now in a separate function. */
318
319 if ((type == T_PTR || type == T_CSA) &&
320 string_is_ip_address(domain, NULL) != 0)
321 {
322 dns_build_reverse(domain, rbuffer);
323 domain = rbuffer;
324 }
325
326 do
327 {
328 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
329
330 /* Do the lookup and sort out the result. There are four special types that
331 are handled specially: T_CSA, T_ZNS, T_APL and T_MXH.
332 The first two are handled in a special lookup function so that the facility
333 could be used from other parts of the Exim code. T_APL is handled by looping
334 over the types of A lookup. T_MXH affects only what happens later on in
335 this function, but for tidiness it is handled by the "special". If the
336 lookup fails, continue with the next domain. In the case of DEFER, adjust
337 the final "nothing found" result, but carry on to the next domain. */
338
339 found = domain;
340 #if HAVE_IPV6
341 if (type == T_APL) /* NB cannot happen unless HAVE_IPV6 */
342 {
343 if (searchtype == T_APL)
344 # if defined(SUPPORT_A6)
345 searchtype = T_A6;
346 # else
347 searchtype = T_AAAA;
348 # endif
349 else if (searchtype == T_A6) searchtype = T_AAAA;
350 else if (searchtype == T_AAAA) searchtype = T_A;
351 rc = dns_special_lookup(&dnsa, domain, searchtype, &found);
352 }
353 else
354 #endif
355 rc = dns_special_lookup(&dnsa, domain, type, &found);
356
357 lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
358 : dns_is_secure(&dnsa) ? US"yes" : US"no";
359
360 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
361 if (rc != DNS_SUCCEED)
362 {
363 if (defer_mode == DEFER)
364 {
365 dns_init(FALSE, FALSE, FALSE);
366 return DEFER; /* always defer */
367 }
368 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
369 continue; /* treat defer as fail */
370 }
371 if (dnssec_mode == DEFER && !dns_is_secure(&dnsa))
372 {
373 failrc = DEFER;
374 continue;
375 }
376
377
378 /* Search the returned records */
379
380 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
381 rr != NULL;
382 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
383 {
384 if (rr->type != searchtype) continue;
385
386 /* There may be several addresses from an A6 record. Put the configured
387 separator between them, just as for between several records. However, A6
388 support is not normally configured these days. */
389
390 if (type == T_A ||
391 #ifdef SUPPORT_A6
392 type == T_A6 ||
393 #endif
394 type == T_AAAA ||
395 type == T_APL)
396 {
397 dns_address *da;
398 for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
399 {
400 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
401 yield = string_cat(yield, &size, &ptr, da->address,
402 Ustrlen(da->address));
403 }
404 continue;
405 }
406
407 /* Other kinds of record just have one piece of data each, but there may be
408 several of them, of course. */
409
410 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
411
412 if (type == T_TXT || type == T_SPF)
413 {
414 if (outsep2 == NULL)
415 {
416 /* output only the first item of data */
417 yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
418 (rr->data)[0]);
419 }
420 else
421 {
422 /* output all items */
423 int data_offset = 0;
424 while (data_offset < rr->size)
425 {
426 uschar chunk_len = (rr->data)[data_offset++];
427 if (outsep2[0] != '\0' && data_offset != 1)
428 yield = string_cat(yield, &size, &ptr, outsep2, 1);
429 yield = string_cat(yield, &size, &ptr,
430 (uschar *)((rr->data)+data_offset), chunk_len);
431 data_offset += chunk_len;
432 }
433 }
434 }
435 else if (type == T_TLSA)
436 {
437 uint8_t usage, selector, matching_type;
438 uint16_t i, payload_length;
439 uschar s[MAX_TLSA_EXPANDED_SIZE];
440 uschar * sp = s;
441 uschar *p = (uschar *)(rr->data);
442
443 usage = *p++;
444 selector = *p++;
445 matching_type = *p++;
446 /* What's left after removing the first 3 bytes above */
447 payload_length = rr->size - 3;
448 sp += sprintf(CS s, "%d %d %d ", usage, selector, matching_type);
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 {
454 sp += sprintf(CS sp, "%02x", (unsigned char)p[i]);
455 }
456 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
457 }
458 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */
459 {
460 int priority, weight, port;
461 uschar s[264];
462 uschar *p = (uschar *)(rr->data);
463
464 if (type == T_MXH)
465 {
466 /* mxh ignores the priority number and includes only the hostnames */
467 GETSHORT(priority, p);
468 }
469 else if (type == T_MX)
470 {
471 GETSHORT(priority, p);
472 sprintf(CS s, "%d ", priority);
473 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
474 }
475 else if (type == T_SRV)
476 {
477 GETSHORT(priority, p);
478 GETSHORT(weight, p);
479 GETSHORT(port, p);
480 sprintf(CS s, "%d %d %d ", priority, weight, port);
481 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
482 }
483 else if (type == T_CSA)
484 {
485 /* See acl_verify_csa() for more comments about CSA. */
486
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 (found != domain)
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 }
513
514 /* GETSHORT() has advanced the pointer to the target domain. */
515
516 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
517 (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
518
519 /* If an overlong response was received, the data will have been
520 truncated and dn_expand may fail. */
521
522 if (rc < 0)
523 {
524 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
525 "domain=%s", dns_text_type(type), domain);
526 break;
527 }
528 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
529 }
530 } /* Loop for list of returned records */
531
532 /* Loop for set of A-lookupu types */
533 } while (type == T_APL && searchtype != T_A);
534
535 } /* Loop for list of domains */
536
537 /* Reclaim unused memory */
538
539 store_reset(yield + ptr + 1);
540
541 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
542 zero and return the result. */
543
544 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
545
546 if (ptr == 0) return failrc;
547 yield[ptr] = 0;
548 *result = yield;
549 return OK;
550 }
551
552
553
554 /*************************************************
555 * Version reporting entry point *
556 *************************************************/
557
558 /* See local README for interface description. */
559
560 #include "../version.h"
561
562 void
563 dnsdb_version_report(FILE *f)
564 {
565 #ifdef DYNLOOKUP
566 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
567 #endif
568 }
569
570
571 static lookup_info _lookup_info = {
572 US"dnsdb", /* lookup name */
573 lookup_querystyle, /* query style */
574 dnsdb_open, /* open function */
575 NULL, /* check function */
576 dnsdb_find, /* find function */
577 NULL, /* no close function */
578 NULL, /* no tidy function */
579 NULL, /* no quoting function */
580 dnsdb_version_report /* version reporting */
581 };
582
583 #ifdef DYNLOOKUP
584 #define dnsdb_lookup_module_info _lookup_module_info
585 #endif
586
587 static lookup_info *_lookup_list[] = { &_lookup_info };
588 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
589
590 /* vi: aw ai sw=2
591 */
592 /* End of lookups/dnsdb.c */