1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2015 */
6 /* See the file NOTICE for conditions of use and distribution. */
9 #include "lf_functions.h"
13 /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
20 /* Many systems do not have T_SPF. */
25 /* New TLSA record for DANE */
30 /* Table of recognized DNS record types and their integer values. */
32 static const char *type_names[] = {
52 static int type_values[] = {
55 T_ADDRESSES, /* Private type for AAAA + A */
59 T_CSA, /* Private type for "Client SMTP Authorization". */
61 T_MXH, /* Private type for "MX hostnames" */
69 T_ZNS /* Private type for "zone nameservers" */
73 /*************************************************
75 *************************************************/
77 /* See local README for interface description. */
80 dnsdb_open(uschar *filename, uschar **errmsg)
82 filename = filename; /* Keep picky compilers happy */
83 errmsg = errmsg; /* Ditto */
84 return (void *)(-1); /* Any non-0 value */
89 /*************************************************
90 * Find entry point for dnsdb *
91 *************************************************/
93 /* See local README for interface description. The query in the "keystring" may
94 consist of a number of parts.
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
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.
107 (c) Options, all comma-terminated, in any order. Any unrecognised option
108 terminates option processing. Recognised options are:
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'.
115 - 'dnssec_FOO', with 'strict', 'lax' and 'never' (default). The meanings are
116 require, try and don't-try dnssec respectively.
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'.
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".
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
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. */
133 dnsdb_find(void *handle, uschar *filename, const uschar *keystring, int length,
134 uschar **result, uschar **errmsg, uint *do_cache)
140 int defer_mode = PASS;
141 int dnssec_mode = OK;
142 int save_retrans = dns_retrans;
143 int save_retry = dns_retry;
146 const uschar *outsep = CUS"\n";
147 const uschar *outsep2 = NULL;
148 uschar *equals, *domain, *found;
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 */
153 uschar *yield = store_get(size);
159 handle = handle; /* Keep picky compilers happy */
164 /* If the string starts with '>' we change the output separator.
165 If it's followed by ';' or ',' we set the TXT output separator. */
167 while (isspace(*keystring)) keystring++;
168 if (*keystring == '>')
170 outsep = keystring + 1;
172 if (*keystring == ',')
174 outsep2 = keystring + 1;
177 else if (*keystring == ';')
182 while (isspace(*keystring)) keystring++;
185 /* Check for a modifier keyword. */
189 if (strncmpic(keystring, US"defer_", 6) == 0)
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; }
200 *errmsg = US"unsupported dnsdb defer behaviour";
204 else if (strncmpic(keystring, US"dnssec_", 7) == 0)
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; }
215 *errmsg = US"unsupported dnsdb dnssec behaviour";
219 else if (strncmpic(keystring, US"retrans_", 8) == 0)
222 if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
224 *errmsg = US"unsupported dnsdb timeout value";
227 dns_retrans = timeout_sec;
228 while (*keystring != ',') keystring++;
230 else if (strncmpic(keystring, US"retry_", 6) == 0)
233 if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
235 *errmsg = US"unsupported dnsdb retry count";
243 while (isspace(*keystring)) keystring++;
244 if (*keystring++ != ',')
246 *errmsg = US"dnsdb modifier syntax error";
249 while (isspace(*keystring)) keystring++;
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. */
256 if ((equals = Ustrchr(keystring, '=')) != NULL)
259 uschar *tend = equals;
261 while (tend > keystring && isspace(tend[-1])) tend--;
262 len = tend - keystring;
264 for (i = 0; i < nelem(type_names); i++)
265 if (len == Ustrlen(type_names[i]) &&
266 strncmpic(keystring, US type_names[i], len) == 0)
268 type = type_values[i];
272 if (i >= nelem(type_names))
274 *errmsg = US"unsupported DNS record type";
278 keystring = equals + 1;
279 while (isspace(*keystring)) keystring++;
282 /* Initialize the resolver in case this is the first time it has been used. */
284 dns_init(FALSE, FALSE, dnssec_mode != OK);
286 /* The remainder of the string must be a list of domains. As long as the lookup
287 for at least one of them succeeds, we return success. Failure means that none
290 The original implementation did not support a list of domains. Adding the list
291 feature is compatible, except in one case: when PTR records are being looked up
292 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
293 here: If the type is PTR and no list separator is specified, and the entire
294 remaining string is valid as an IP address, set an impossible separator so that
295 it is treated as one item. */
297 if (type == T_PTR && keystring[0] != '<' &&
298 string_is_ip_address(keystring, NULL) != 0)
301 /* SPF strings should be concatenated without a separator, thus make
302 it the default if not defined (see RFC 4408 section 3.1.3).
303 Multiple SPF records are forbidden (section 3.1.2) but are currently
304 not handled specially, thus they are concatenated with \n by default.
305 MX priority and value are space-separated by default.
306 SRV and TLSA record parts are space-separated by default. */
308 if (!outsep2) switch(type)
310 case T_SPF: outsep2 = US""; break;
311 case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
314 /* Now scan the list and do a lookup for each item */
316 while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
319 int searchtype = (type == T_CSA)? T_SRV : /* record type we want */
320 (type == T_MXH)? T_MX :
321 (type == T_ZNS)? T_NS : type;
323 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
324 key if the original is an IP address (some experimental protocols are using
325 PTR records for different purposes where the key string is a host name, and
326 Exim's extended CSA can be keyed by domains or IP addresses). This code for
327 doing the reversal is now in a separate function. */
329 if ((type == T_PTR || type == T_CSA) &&
330 string_is_ip_address(domain, NULL) != 0)
332 dns_build_reverse(domain, rbuffer);
338 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
340 /* Do the lookup and sort out the result. There are four special types that
341 are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
342 The first two are handled in a special lookup function so that the facility
343 could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
344 over the types of A lookup. T_MXH affects only what happens later on in
345 this function, but for tidiness it is handled by the "special". If the
346 lookup fails, continue with the next domain. In the case of DEFER, adjust
347 the final "nothing found" result, but carry on to the next domain. */
351 if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
353 if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
354 else if (searchtype == T_AAAA) searchtype = T_A;
355 rc = dns_special_lookup(&dnsa, domain, searchtype, CUSS &found);
359 rc = dns_special_lookup(&dnsa, domain, type, CUSS &found);
361 lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
362 : dns_is_secure(&dnsa) ? US"yes" : US"no";
364 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
365 if ( rc != DNS_SUCCEED
366 || (dnssec_mode == DEFER && !dns_is_secure(&dnsa))
369 if (defer_mode == DEFER)
371 dns_retrans = save_retrans;
372 dns_retry = save_retry;
373 dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
374 return DEFER; /* always defer */
376 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
377 continue; /* treat defer as fail */
381 /* Search the returned records */
383 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
385 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
387 if (rr->type != searchtype) continue;
389 if (*do_cache > rr->ttl)
392 if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
395 for (da = dns_address_from_rr(&dnsa, rr); da; da = da->next)
397 if (ptr != 0) yield = string_catn(yield, &size, &ptr, outsep, 1);
398 yield = string_cat(yield, &size, &ptr, da->address);
403 /* Other kinds of record just have one piece of data each, but there may be
404 several of them, of course. */
406 if (ptr != 0) yield = string_catn(yield, &size, &ptr, outsep, 1);
408 if (type == T_TXT || type == T_SPF)
412 /* output only the first item of data */
413 yield = string_catn(yield, &size, &ptr, (uschar *)(rr->data+1),
418 /* output all items */
420 while (data_offset < rr->size)
422 uschar chunk_len = (rr->data)[data_offset++];
423 if (outsep2[0] != '\0' && data_offset != 1)
424 yield = string_catn(yield, &size, &ptr, outsep2, 1);
425 yield = string_catn(yield, &size, &ptr,
426 US ((rr->data)+data_offset), chunk_len);
427 data_offset += chunk_len;
431 else if (type == T_TLSA)
433 uint8_t usage, selector, matching_type;
434 uint16_t i, payload_length;
435 uschar s[MAX_TLSA_EXPANDED_SIZE];
437 uschar * p = US rr->data;
441 matching_type = *p++;
442 /* What's left after removing the first 3 bytes above */
443 payload_length = rr->size - 3;
444 sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
445 selector, *outsep2, matching_type, *outsep2);
446 /* Now append the cert/identifier, one hex char at a time */
448 i < payload_length && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4);
450 sp += sprintf(CS sp, "%02x", (unsigned char)p[i]);
452 yield = string_cat(yield, &size, &ptr, s);
454 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
456 int priority, weight, port;
458 uschar * p = US rr->data;
463 /* mxh ignores the priority number and includes only the hostnames */
464 GETSHORT(priority, p);
468 GETSHORT(priority, p);
469 sprintf(CS s, "%d%c", priority, *outsep2);
470 yield = string_cat(yield, &size, &ptr, s);
474 GETSHORT(priority, p);
477 sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
478 weight, *outsep2, port, *outsep2);
479 yield = string_cat(yield, &size, &ptr, s);
483 /* See acl_verify_csa() for more comments about CSA. */
484 GETSHORT(priority, p);
488 if (priority != 1) continue; /* CSA version must be 1 */
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. */
494 if (Ustrcmp(found, domain) != 0)
496 if (port & 1) *s = 'X'; /* explicit authorization required */
497 else *s = '?'; /* no subdomain assertions here */
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 */
508 yield = string_catn(yield, &size, &ptr, s, 2);
515 /* GETSHORT() has advanced the pointer to the target domain. */
517 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
518 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
520 /* If an overlong response was received, the data will have been
521 truncated and dn_expand may fail. */
525 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
526 "domain=%s", dns_text_type(type), domain);
529 else yield = string_cat(yield, &size, &ptr, s);
531 if (type == T_SOA && outsep2 != NULL)
533 unsigned long serial, refresh, retry, expire, minimum;
536 yield = string_catn(yield, &size, &ptr, outsep2, 1);
538 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
539 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
542 log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
543 "domain=%s", dns_text_type(type), domain);
546 else yield = string_cat(yield, &size, &ptr, s);
549 GETLONG(serial, p); GETLONG(refresh, p);
550 GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
551 sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
552 *outsep2, serial, *outsep2, refresh,
553 *outsep2, retry, *outsep2, expire, *outsep2, minimum);
554 yield = string_cat(yield, &size, &ptr, s);
557 } /* Loop for list of returned records */
559 /* Loop for set of A-lookup types */
560 } while (type == T_ADDRESSES && searchtype != T_A);
562 } /* Loop for list of domains */
564 /* Reclaim unused memory */
566 store_reset(yield + ptr + 1);
568 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
569 zero and return the result. */
571 dns_retrans = save_retrans;
572 dns_retry = save_retry;
573 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
575 if (ptr == 0) return failrc;
583 /*************************************************
584 * Version reporting entry point *
585 *************************************************/
587 /* See local README for interface description. */
589 #include "../version.h"
592 dnsdb_version_report(FILE *f)
595 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
600 static lookup_info _lookup_info = {
601 US"dnsdb", /* lookup name */
602 lookup_querystyle, /* query style */
603 dnsdb_open, /* open function */
604 NULL, /* check function */
605 dnsdb_find, /* find function */
606 NULL, /* no close function */
607 NULL, /* no tidy function */
608 NULL, /* no quoting function */
609 dnsdb_version_report /* version reporting */
613 #define dnsdb_lookup_module_info _lookup_module_info
616 static lookup_info *_lookup_list[] = { &_lookup_info };
617 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
621 /* End of lookups/dnsdb.c */