1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
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' (default), and 'never'. 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)
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 handle = handle; /* Keep picky compilers happy */
161 /* If the string starts with '>' we change the output separator.
162 If it's followed by ';' or ',' we set the TXT output separator. */
164 while (isspace(*keystring)) keystring++;
165 if (*keystring == '>')
167 outsep = keystring + 1;
169 if (*keystring == ',')
171 outsep2 = keystring + 1;
174 else if (*keystring == ';')
179 while (isspace(*keystring)) keystring++;
182 /* Check for a modifier keyword. */
186 if (strncmpic(keystring, US"defer_", 6) == 0)
189 if (strncmpic(keystring, US"strict", 6) == 0)
190 { defer_mode = DEFER; keystring += 6; }
191 else if (strncmpic(keystring, US"lax", 3) == 0)
192 { defer_mode = PASS; keystring += 3; }
193 else if (strncmpic(keystring, US"never", 5) == 0)
194 { defer_mode = OK; keystring += 5; }
197 *errmsg = US"unsupported dnsdb defer behaviour";
201 else if (strncmpic(keystring, US"dnssec_", 7) == 0)
204 if (strncmpic(keystring, US"strict", 6) == 0)
205 { dnssec_mode = DEFER; keystring += 6; }
206 else if (strncmpic(keystring, US"lax", 3) == 0)
207 { dnssec_mode = PASS; keystring += 3; }
208 else if (strncmpic(keystring, US"never", 5) == 0)
209 { dnssec_mode = OK; keystring += 5; }
212 *errmsg = US"unsupported dnsdb dnssec behaviour";
216 else if (strncmpic(keystring, US"retrans_", 8) == 0)
219 if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
221 *errmsg = US"unsupported dnsdb timeout value";
224 dns_retrans = timeout_sec;
225 while (*keystring != ',') keystring++;
227 else if (strncmpic(keystring, US"retry_", 6) == 0)
230 if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
232 *errmsg = US"unsupported dnsdb retry count";
240 while (isspace(*keystring)) keystring++;
241 if (*keystring++ != ',')
243 *errmsg = US"dnsdb modifier syntax error";
246 while (isspace(*keystring)) keystring++;
249 /* Figure out the "type" value if it is not T_TXT.
250 If the keystring contains an = this must be preceded by a valid type name. */
253 if ((equals = Ustrchr(keystring, '=')) != NULL)
256 uschar *tend = equals;
258 while (tend > keystring && isspace(tend[-1])) tend--;
259 len = tend - keystring;
261 for (i = 0; i < nelem(type_names); i++)
262 if (len == Ustrlen(type_names[i]) &&
263 strncmpic(keystring, US type_names[i], len) == 0)
265 type = type_values[i];
269 if (i >= nelem(type_names))
271 *errmsg = US"unsupported DNS record type";
275 keystring = equals + 1;
276 while (isspace(*keystring)) keystring++;
279 /* Initialize the resolver in case this is the first time it has been used. */
281 dns_init(FALSE, FALSE, dnssec_mode != OK);
283 /* The remainder of the string must be a list of domains. As long as the lookup
284 for at least one of them succeeds, we return success. Failure means that none
287 The original implementation did not support a list of domains. Adding the list
288 feature is compatible, except in one case: when PTR records are being looked up
289 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
290 here: If the type is PTR and no list separator is specified, and the entire
291 remaining string is valid as an IP address, set an impossible separator so that
292 it is treated as one item. */
294 if (type == T_PTR && keystring[0] != '<' &&
295 string_is_ip_address(keystring, NULL) != 0)
298 /* SPF strings should be concatenated without a separator, thus make
299 it the default if not defined (see RFC 4408 section 3.1.3).
300 Multiple SPF records are forbidden (section 3.1.2) but are currently
301 not handled specially, thus they are concatenated with \n by default.
302 MX priority and value are space-separated by default.
303 SRV and TLSA record parts are space-separated by default. */
305 if (!outsep2) switch(type)
307 case T_SPF: outsep2 = US""; break;
308 case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
311 /* Now scan the list and do a lookup for each item */
313 while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
315 int searchtype = type == T_CSA ? T_SRV : /* record type we want */
316 type == T_MXH ? T_MX :
317 type == T_ZNS ? T_NS : type;
319 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
320 key if the original is an IP address (some experimental protocols are using
321 PTR records for different purposes where the key string is a host name, and
322 Exim's extended CSA can be keyed by domains or IP addresses). This code for
323 doing the reversal is now in a separate function. */
325 if ((type == T_PTR || type == T_CSA) &&
326 string_is_ip_address(domain, NULL) != 0)
327 domain = dns_build_reverse(domain);
331 DEBUG(D_lookup) debug_printf_indent("dnsdb key: %s\n", domain);
333 /* Do the lookup and sort out the result. There are four special types that
334 are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
335 The first two are handled in a special lookup function so that the facility
336 could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
337 over the types of A lookup. T_MXH affects only what happens later on in
338 this function, but for tidiness it is handled by the "special". If the
339 lookup fails, continue with the next domain. In the case of DEFER, adjust
340 the final "nothing found" result, but carry on to the next domain. */
344 if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
346 if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
347 else if (searchtype == T_AAAA) searchtype = T_A;
348 rc = dns_special_lookup(dnsa, domain, searchtype, CUSS &found);
352 rc = dns_special_lookup(dnsa, domain, type, CUSS &found);
354 lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
355 : dns_is_secure(dnsa) ? US"yes" : US"no";
357 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
358 if ( rc != DNS_SUCCEED
359 || (dnssec_mode == DEFER && !dns_is_secure(dnsa))
362 if (defer_mode == DEFER)
364 dns_retrans = save_retrans;
365 dns_retry = save_retry;
366 dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
367 return DEFER; /* always defer */
369 if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
370 continue; /* treat defer as fail */
374 /* Search the returned records */
376 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
377 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == searchtype)
379 if (*do_cache > rr->ttl)
382 if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
384 for (dns_address * da = dns_address_from_rr(dnsa, rr); da; da = da->next)
386 if (yield->ptr) yield = string_catn(yield, outsep, 1);
387 yield = string_cat(yield, da->address);
392 /* Other kinds of record just have one piece of data each, but there may be
393 several of them, of course. */
395 if (yield->ptr) yield = string_catn(yield, outsep, 1);
397 if (type == T_TXT || type == T_SPF)
399 if (outsep2 == NULL) /* output only the first item of data */
400 yield = string_catn(yield, US (rr->data+1), (rr->data)[0]);
403 /* output all items */
405 while (data_offset < rr->size)
407 uschar chunk_len = (rr->data)[data_offset++];
408 if (outsep2[0] != '\0' && data_offset != 1)
409 yield = string_catn(yield, outsep2, 1);
410 yield = string_catn(yield, US ((rr->data)+data_offset), chunk_len);
411 data_offset += chunk_len;
415 else if (type == T_TLSA)
417 uint8_t usage, selector, matching_type;
418 uint16_t payload_length;
419 uschar s[MAX_TLSA_EXPANDED_SIZE];
421 uschar * p = US rr->data;
425 matching_type = *p++;
426 /* What's left after removing the first 3 bytes above */
427 payload_length = rr->size - 3;
428 sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
429 selector, *outsep2, matching_type, *outsep2);
430 /* Now append the cert/identifier, one hex char at a time */
431 while (payload_length-- > 0 && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4))
432 sp += sprintf(CS sp, "%02x", *p++);
434 yield = string_cat(yield, s);
436 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
438 int priority, weight, port;
440 uschar * p = US rr->data;
445 /* mxh ignores the priority number and includes only the hostnames */
446 GETSHORT(priority, p);
450 GETSHORT(priority, p);
451 sprintf(CS s, "%d%c", priority, *outsep2);
452 yield = string_cat(yield, s);
456 GETSHORT(priority, p);
459 sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
460 weight, *outsep2, port, *outsep2);
461 yield = string_cat(yield, s);
465 /* See acl_verify_csa() for more comments about CSA. */
466 GETSHORT(priority, p);
470 if (priority != 1) continue; /* CSA version must be 1 */
472 /* If the CSA record we found is not the one we asked for, analyse
473 the subdomain assertions in the port field, else analyse the direct
474 authorization status in the weight field. */
476 if (Ustrcmp(found, domain) != 0)
478 if (port & 1) *s = 'X'; /* explicit authorization required */
479 else *s = '?'; /* no subdomain assertions here */
483 if (weight < 2) *s = 'N'; /* not authorized */
484 else if (weight == 2) *s = 'Y'; /* authorized */
485 else if (weight == 3) *s = '?'; /* unauthorizable */
486 else continue; /* invalid */
490 yield = string_catn(yield, s, 2);
497 /* GETSHORT() has advanced the pointer to the target domain. */
499 rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
500 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
502 /* If an overlong response was received, the data will have been
503 truncated and dn_expand may fail. */
507 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
508 "domain=%s", dns_text_type(type), domain);
511 else yield = string_cat(yield, s);
513 if (type == T_SOA && outsep2 != NULL)
515 unsigned long serial, refresh, retry, expire, minimum;
518 yield = string_catn(yield, outsep2, 1);
520 rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
521 (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
524 log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
525 "domain=%s", dns_text_type(type), domain);
528 else yield = string_cat(yield, s);
531 GETLONG(serial, p); GETLONG(refresh, p);
532 GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
533 sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
534 *outsep2, serial, *outsep2, refresh,
535 *outsep2, retry, *outsep2, expire, *outsep2, minimum);
536 yield = string_cat(yield, s);
539 } /* Loop for list of returned records */
541 /* Loop for set of A-lookup types */
542 } while (type == T_ADDRESSES && searchtype != T_A);
544 } /* Loop for list of domains */
546 /* Reclaim unused memory */
548 gstring_release_unused(yield);
550 /* If yield NULL we have not found anything. Otherwise, insert the terminating
551 zero and return the result. */
553 dns_retrans = save_retrans;
554 dns_retry = save_retry;
555 dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
557 if (!yield || !yield->ptr) return failrc;
559 *result = string_from_gstring(yield);
565 /*************************************************
566 * Version reporting entry point *
567 *************************************************/
569 /* See local README for interface description. */
571 #include "../version.h"
574 dnsdb_version_report(FILE *f)
577 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
582 static lookup_info _lookup_info = {
583 US"dnsdb", /* lookup name */
584 lookup_querystyle, /* query style */
585 dnsdb_open, /* open function */
586 NULL, /* check function */
587 dnsdb_find, /* find function */
588 NULL, /* no close function */
589 NULL, /* no tidy function */
590 NULL, /* no quoting function */
591 dnsdb_version_report /* version reporting */
595 #define dnsdb_lookup_module_info _lookup_module_info
598 static lookup_info *_lookup_list[] = { &_lookup_info };
599 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
603 /* End of lookups/dnsdb.c */