1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* Copyright (c) The Exim Maintainers 2020 */
7 /* See the file NOTICE for conditions of use and distribution. */
10 #include "lf_functions.h"
14 /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
21 /* Many systems do not have T_SPF. */
26 /* New TLSA record for DANE */
31 /* Table of recognized DNS record types and their integer values. */
33 static const char *type_names[] = {
53 static int type_values[] = {
56 T_ADDRESSES, /* Private type for AAAA + A */
60 T_CSA, /* Private type for "Client SMTP Authorization". */
62 T_MXH, /* Private type for "MX hostnames" */
70 T_ZNS /* Private type for "zone nameservers" */
74 /*************************************************
76 *************************************************/
78 /* See local README for interface description. */
81 dnsdb_open(const uschar * filename, uschar **errmsg)
83 return (void *)(-1); /* Any non-0 value */
88 /*************************************************
89 * Find entry point for dnsdb *
90 *************************************************/
92 /* See local README for interface description. The query in the "keystring" may
93 consist of a number of parts.
95 (a) If the first significant character is '>' then the next character is the
96 separator character that is used when multiple records are found. The default
99 (b) If the next character is ',' then the next character is the separator
100 character used for multiple items of text in "TXT" records. Alternatively,
101 if the next character is ';' then these multiple items are concatenated with
102 no separator. With neither of these options specified, only the first item
103 is output. Similarly for "SPF" records, but the default for joining multiple
104 items in one SPF record is the empty string, for direct concatenation.
106 (c) Options, all comma-terminated, in any order. Any unrecognised option
107 terminates option processing. Recognised options are:
109 - 'defer_FOO': set the defer behaviour to FOO. The possible behaviours are:
110 'strict', where any defer causes the whole lookup to defer; 'lax', where a defer
111 causes the whole lookup to defer only if none of the DNS queries succeeds; and
112 'never', where all defers are as if the lookup failed. The default is 'lax'.
114 - 'dnssec_FOO', with 'strict', 'lax' (default), and 'never'. The meanings are
115 require, try and don't-try dnssec respectively.
117 - 'retrans_VAL', set the timeout value. VAL is an Exim time specification
118 (eg "5s"). The default is set by the main configuration option 'dns_retrans'.
120 - 'retry_VAL', set the retry count on timeouts. VAL is an integer. The
121 default is set by the main configuration option "dns_retry".
123 (d) If the next sequence of characters is a sequence of letters and digits
124 followed by '=', it is interpreted as the name of the DNS record type. The
127 (e) Then there follows list of domain names. This is a generalized Exim list,
128 which may start with '<' in order to set a specific separator. The default
129 separator, as always, is colon. */
132 dnsdb_find(void * handle, const uschar * filename, const uschar * keystring,
133 int length, uschar ** result, uschar ** errmsg, uint * do_cache,
138 int defer_mode = PASS;
139 int dnssec_mode = PASS;
140 int save_retrans = dns_retrans;
141 int save_retry = dns_retry;
144 const uschar *outsep = CUS"\n";
145 const uschar *outsep2 = NULL;
146 uschar *equals, *domain, *found;
148 dns_answer * dnsa = store_get_dns_answer();
151 /* Because we're working in the search pool, we try to reclaim as much
152 store as possible later, so we preallocate the result here */
154 gstring * yield = string_get(256);
156 /* If the string starts with '>' we change the output separator.
157 If it's followed by ';' or ',' we set the TXT output separator. */
159 while (isspace(*keystring)) keystring++;
160 if (*keystring == '>')
162 outsep = keystring + 1;
164 if (*keystring == ',')
166 outsep2 = keystring + 1;
169 else if (*keystring == ';')
174 while (isspace(*keystring)) keystring++;
177 /* Check for a modifier keyword. */
181 if (strncmpic(keystring, US"defer_", 6) == 0)
184 if (strncmpic(keystring, US"strict", 6) == 0)
185 { defer_mode = DEFER; keystring += 6; }
186 else if (strncmpic(keystring, US"lax", 3) == 0)
187 { defer_mode = PASS; keystring += 3; }
188 else if (strncmpic(keystring, US"never", 5) == 0)
189 { defer_mode = OK; keystring += 5; }
192 *errmsg = US"unsupported dnsdb defer behaviour";
196 else if (strncmpic(keystring, US"dnssec_", 7) == 0)
199 if (strncmpic(keystring, US"strict", 6) == 0)
200 { dnssec_mode = DEFER; keystring += 6; }
201 else if (strncmpic(keystring, US"lax", 3) == 0)
202 { dnssec_mode = PASS; keystring += 3; }
203 else if (strncmpic(keystring, US"never", 5) == 0)
204 { dnssec_mode = OK; keystring += 5; }
207 *errmsg = US"unsupported dnsdb dnssec behaviour";
211 else if (strncmpic(keystring, US"retrans_", 8) == 0)
214 if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
216 *errmsg = US"unsupported dnsdb timeout value";
219 dns_retrans = timeout_sec;
220 while (*keystring != ',') keystring++;
222 else if (strncmpic(keystring, US"retry_", 6) == 0)
225 if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
227 *errmsg = US"unsupported dnsdb retry count";
235 while (isspace(*keystring)) keystring++;
236 if (*keystring++ != ',')
238 *errmsg = US"dnsdb modifier syntax error";
241 while (isspace(*keystring)) keystring++;
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. */
248 if ((equals = Ustrchr(keystring, '=')) != NULL)
251 uschar *tend = equals;
253 while (tend > keystring && isspace(tend[-1])) tend--;
254 len = tend - keystring;
256 for (i = 0; i < nelem(type_names); i++)
257 if (len == Ustrlen(type_names[i]) &&
258 strncmpic(keystring, US type_names[i], len) == 0)
260 type = type_values[i];
264 if (i >= nelem(type_names))
266 *errmsg = US"unsupported DNS record type";
270 keystring = equals + 1;
271 while (isspace(*keystring)) keystring++;
274 /* Initialize the resolver in case this is the first time it has been used. */
276 dns_init(FALSE, FALSE, dnssec_mode != OK);
278 /* The remainder of the string must be a list of domains. As long as the lookup
279 for at least one of them succeeds, we return success. Failure means that none
282 The original implementation did not support a list of domains. Adding the list
283 feature is compatible, except in one case: when PTR records are being looked up
284 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
285 here: If the type is PTR and no list separator is specified, and the entire
286 remaining string is valid as an IP address, set an impossible separator so that
287 it is treated as one item. */
289 if (type == T_PTR && keystring[0] != '<' &&
290 string_is_ip_address(keystring, NULL) != 0)
293 /* SPF strings should be concatenated without a separator, thus make
294 it the default if not defined (see RFC 4408 section 3.1.3).
295 Multiple SPF records are forbidden (section 3.1.2) but are currently
296 not handled specially, thus they are concatenated with \n by default.
297 MX priority and value are space-separated by default.
298 SRV and TLSA record parts are space-separated by default. */
300 if (!outsep2) switch(type)
302 case T_SPF: outsep2 = US""; break;
303 case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
306 /* Now scan the list and do a lookup for each item */
308 while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
310 int searchtype = type == T_CSA ? T_SRV : /* record type we want */
311 type == T_MXH ? T_MX :
312 type == T_ZNS ? T_NS : type;
314 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
315 key if the original is an IP address (some experimental protocols are using
316 PTR records for different purposes where the key string is a host name, and
317 Exim's extended CSA can be keyed by domains or IP addresses). This code for
318 doing the reversal is now in a separate function. */
320 if ((type == T_PTR || type == T_CSA) &&
321 string_is_ip_address(domain, NULL) != 0)
322 domain = dns_build_reverse(domain);
326 DEBUG(D_lookup) debug_printf_indent("dnsdb key: %s\n", domain);
328 /* Do the lookup and sort out the result. There are four special types that
329 are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
330 The first two are handled in a special lookup function so that the facility
331 could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
332 over the types of A lookup. T_MXH affects only what happens later on in
333 this function, but for tidiness it is handled by the "special". If the
334 lookup fails, continue with the next domain. In the case of DEFER, adjust
335 the final "nothing found" result, but carry on to the next domain. */
339 if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
341 if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
342 else if (searchtype == T_AAAA) searchtype = T_A;
343 rc = dns_special_lookup(dnsa, domain, searchtype, CUSS &found);
347 rc = dns_special_lookup(dnsa, domain, type, CUSS &found);
349 lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
350 : dns_is_secure(dnsa) ? US"yes" : US"no";
352 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
353 if ( rc != DNS_SUCCEED
354 || (dnssec_mode == DEFER && !dns_is_secure(dnsa))
357 if (defer_mode == DEFER)
359 dns_retrans = save_retrans;
360 dns_retry = save_retry;
361 dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
362 return DEFER; /* always defer */
364 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
365 continue; /* treat defer as fail */
369 /* Search the returned records */
371 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
372 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == searchtype)
374 if (*do_cache > rr->ttl)
377 if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
379 for (dns_address * da = dns_address_from_rr(dnsa, rr); da; da = da->next)
381 if (yield->ptr) yield = string_catn(yield, outsep, 1);
382 yield = string_cat(yield, da->address);
387 /* Other kinds of record just have one piece of data each, but there may be
388 several of them, of course. */
390 if (yield->ptr) yield = string_catn(yield, outsep, 1);
392 if (type == T_TXT || type == T_SPF)
394 if (outsep2 == NULL) /* output only the first item of data */
395 yield = string_catn(yield, US (rr->data+1), (rr->data)[0]);
398 /* output all items */
400 while (data_offset < rr->size)
402 uschar chunk_len = (rr->data)[data_offset++];
403 if (outsep2[0] != '\0' && data_offset != 1)
404 yield = string_catn(yield, outsep2, 1);
405 yield = string_catn(yield, US ((rr->data)+data_offset), chunk_len);
406 data_offset += chunk_len;
410 else if (type == T_TLSA)
412 uint8_t usage, selector, matching_type;
413 uint16_t payload_length;
414 uschar s[MAX_TLSA_EXPANDED_SIZE];
416 uschar * p = US rr->data;
420 matching_type = *p++;
421 /* What's left after removing the first 3 bytes above */
422 payload_length = rr->size - 3;
423 sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
424 selector, *outsep2, matching_type, *outsep2);
425 /* Now append the cert/identifier, one hex char at a time */
426 while (payload_length-- > 0 && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4))
427 sp += sprintf(CS sp, "%02x", *p++);
429 yield = string_cat(yield, s);
431 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
433 int priority, weight, port;
435 uschar * p = US rr->data;
440 /* mxh ignores the priority number and includes only the hostnames */
441 GETSHORT(priority, p);
445 GETSHORT(priority, p);
446 sprintf(CS s, "%d%c", priority, *outsep2);
447 yield = string_cat(yield, s);
451 GETSHORT(priority, p);
454 sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
455 weight, *outsep2, port, *outsep2);
456 yield = string_cat(yield, s);
460 /* See acl_verify_csa() for more comments about CSA. */
461 GETSHORT(priority, p);
465 if (priority != 1) continue; /* CSA version must be 1 */
467 /* If the CSA record we found is not the one we asked for, analyse
468 the subdomain assertions in the port field, else analyse the direct
469 authorization status in the weight field. */
471 if (Ustrcmp(found, domain) != 0)
473 if (port & 1) *s = 'X'; /* explicit authorization required */
474 else *s = '?'; /* no subdomain assertions here */
478 if (weight < 2) *s = 'N'; /* not authorized */
479 else if (weight == 2) *s = 'Y'; /* authorized */
480 else if (weight == 3) *s = '?'; /* unauthorizable */
481 else continue; /* invalid */
485 yield = string_catn(yield, s, 2);
492 /* GETSHORT() has advanced the pointer to the target domain. */
494 rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
495 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
497 /* If an overlong response was received, the data will have been
498 truncated and dn_expand may fail. */
502 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
503 "domain=%s", dns_text_type(type), domain);
506 else yield = string_cat(yield, s);
508 if (type == T_SOA && outsep2 != NULL)
510 unsigned long serial, refresh, retry, expire, minimum;
513 yield = string_catn(yield, outsep2, 1);
515 rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
516 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
519 log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
520 "domain=%s", dns_text_type(type), domain);
523 else yield = string_cat(yield, s);
526 GETLONG(serial, p); GETLONG(refresh, p);
527 GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
528 sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
529 *outsep2, serial, *outsep2, refresh,
530 *outsep2, retry, *outsep2, expire, *outsep2, minimum);
531 yield = string_cat(yield, s);
534 } /* Loop for list of returned records */
536 /* Loop for set of A-lookup types */
537 } while (type == T_ADDRESSES && searchtype != T_A);
539 } /* Loop for list of domains */
541 /* Reclaim unused memory */
543 gstring_release_unused(yield);
545 /* If yield NULL we have not found anything. Otherwise, insert the terminating
546 zero and return the result. */
548 dns_retrans = save_retrans;
549 dns_retry = save_retry;
550 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
552 if (!yield || !yield->ptr) return failrc;
554 *result = string_from_gstring(yield);
560 /*************************************************
561 * Version reporting entry point *
562 *************************************************/
564 /* See local README for interface description. */
566 #include "../version.h"
569 dnsdb_version_report(FILE *f)
572 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
577 static lookup_info _lookup_info = {
578 .name = US"dnsdb", /* lookup name */
579 .type = lookup_querystyle, /* query style */
580 .open = dnsdb_open, /* open function */
581 .check = NULL, /* check function */
582 .find = dnsdb_find, /* find function */
583 .close = NULL, /* no close function */
584 .tidy = NULL, /* no tidy function */
585 .quote = NULL, /* no quoting function */
586 .version_report = dnsdb_version_report /* version reporting */
590 #define dnsdb_lookup_module_info _lookup_module_info
593 static lookup_info *_lookup_list[] = { &_lookup_info };
594 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
598 /* End of lookups/dnsdb.c */