MacOS: fix clang redef warning
[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_ADDRESSES, /* 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_ADDRESSES 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_ADDRESSES 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_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
342 {
343 if (searchtype == T_ADDRESSES)
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 || dnssec_mode == DEFER && !dns_is_secure(&dnsa)
363 )
364 {
365 if (defer_mode == DEFER)
366 {
367 dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
368 return DEFER; /* always defer */
369 }
370 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
371 continue; /* treat defer as fail */
372 }
373
374
375 /* Search the returned records */
376
377 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
378 rr != NULL;
379 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
380 {
381 if (rr->type != searchtype) continue;
382
383 /* There may be several addresses from an A6 record. Put the configured
384 separator between them, just as for between several records. However, A6
385 support is not normally configured these days. */
386
387 if (type == T_A ||
388 #ifdef SUPPORT_A6
389 type == T_A6 ||
390 #endif
391 type == T_AAAA ||
392 type == T_ADDRESSES)
393 {
394 dns_address *da;
395 for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
396 {
397 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
398 yield = string_cat(yield, &size, &ptr, da->address,
399 Ustrlen(da->address));
400 }
401 continue;
402 }
403
404 /* Other kinds of record just have one piece of data each, but there may be
405 several of them, of course. */
406
407 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
408
409 if (type == T_TXT || type == T_SPF)
410 {
411 if (outsep2 == NULL)
412 {
413 /* output only the first item of data */
414 yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
415 (rr->data)[0]);
416 }
417 else
418 {
419 /* output all items */
420 int data_offset = 0;
421 while (data_offset < rr->size)
422 {
423 uschar chunk_len = (rr->data)[data_offset++];
424 if (outsep2[0] != '\0' && data_offset != 1)
425 yield = string_cat(yield, &size, &ptr, outsep2, 1);
426 yield = string_cat(yield, &size, &ptr,
427 (uschar *)((rr->data)+data_offset), chunk_len);
428 data_offset += chunk_len;
429 }
430 }
431 }
432 else if (type == T_TLSA)
433 {
434 uint8_t usage, selector, matching_type;
435 uint16_t i, payload_length;
436 uschar s[MAX_TLSA_EXPANDED_SIZE];
437 uschar * sp = s;
438 uschar *p = (uschar *)(rr->data);
439
440 usage = *p++;
441 selector = *p++;
442 matching_type = *p++;
443 /* What's left after removing the first 3 bytes above */
444 payload_length = rr->size - 3;
445 sp += sprintf(CS s, "%d %d %d ", usage, selector, matching_type);
446 /* Now append the cert/identifier, one hex char at a time */
447 for (i=0;
448 i < payload_length && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4);
449 i++)
450 {
451 sp += sprintf(CS sp, "%02x", (unsigned char)p[i]);
452 }
453 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
454 }
455 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */
456 {
457 int priority, weight, port;
458 uschar s[264];
459 uschar *p = (uschar *)(rr->data);
460
461 if (type == T_MXH)
462 {
463 /* mxh ignores the priority number and includes only the hostnames */
464 GETSHORT(priority, p);
465 }
466 else if (type == T_MX)
467 {
468 GETSHORT(priority, p);
469 sprintf(CS s, "%d ", priority);
470 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
471 }
472 else if (type == T_SRV)
473 {
474 GETSHORT(priority, p);
475 GETSHORT(weight, p);
476 GETSHORT(port, p);
477 sprintf(CS s, "%d %d %d ", priority, weight, port);
478 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
479 }
480 else if (type == T_CSA)
481 {
482 /* See acl_verify_csa() for more comments about CSA. */
483
484 GETSHORT(priority, p);
485 GETSHORT(weight, p);
486 GETSHORT(port, p);
487
488 if (priority != 1) continue; /* CSA version must be 1 */
489
490 /* If the CSA record we found is not the one we asked for, analyse
491 the subdomain assertions in the port field, else analyse the direct
492 authorization status in the weight field. */
493
494 if (found != domain)
495 {
496 if (port & 1) *s = 'X'; /* explicit authorization required */
497 else *s = '?'; /* no subdomain assertions here */
498 }
499 else
500 {
501 if (weight < 2) *s = 'N'; /* not authorized */
502 else if (weight == 2) *s = 'Y'; /* authorized */
503 else if (weight == 3) *s = '?'; /* unauthorizable */
504 else continue; /* invalid */
505 }
506
507 s[1] = ' ';
508 yield = string_cat(yield, &size, &ptr, s, 2);
509 }
510
511 /* GETSHORT() has advanced the pointer to the target domain. */
512
513 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
514 (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
515
516 /* If an overlong response was received, the data will have been
517 truncated and dn_expand may fail. */
518
519 if (rc < 0)
520 {
521 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
522 "domain=%s", dns_text_type(type), domain);
523 break;
524 }
525 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
526 }
527 } /* Loop for list of returned records */
528
529 /* Loop for set of A-lookupu types */
530 } while (type == T_ADDRESSES && searchtype != T_A);
531
532 } /* Loop for list of domains */
533
534 /* Reclaim unused memory */
535
536 store_reset(yield + ptr + 1);
537
538 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
539 zero and return the result. */
540
541 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
542
543 if (ptr == 0) return failrc;
544 yield[ptr] = 0;
545 *result = yield;
546 return OK;
547 }
548
549
550
551 /*************************************************
552 * Version reporting entry point *
553 *************************************************/
554
555 /* See local README for interface description. */
556
557 #include "../version.h"
558
559 void
560 dnsdb_version_report(FILE *f)
561 {
562 #ifdef DYNLOOKUP
563 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
564 #endif
565 }
566
567
568 static lookup_info _lookup_info = {
569 US"dnsdb", /* lookup name */
570 lookup_querystyle, /* query style */
571 dnsdb_open, /* open function */
572 NULL, /* check function */
573 dnsdb_find, /* find function */
574 NULL, /* no close function */
575 NULL, /* no tidy function */
576 NULL, /* no quoting function */
577 dnsdb_version_report /* version reporting */
578 };
579
580 #ifdef DYNLOOKUP
581 #define dnsdb_lookup_module_info _lookup_module_info
582 #endif
583
584 static lookup_info *_lookup_list[] = { &_lookup_info };
585 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
586
587 /* vi: aw ai sw=2
588 */
589 /* End of lookups/dnsdb.c */