1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
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 /* Table of recognized DNS record types and their integer values. */
27 static const char *type_names[] = {
47 static int type_values[] = {
56 T_CSA, /* Private type for "Client SMTP Authorization". */
58 T_MXH, /* Private type for "MX hostnames" */
64 T_ZNS /* Private type for "zone nameservers" */
68 /*************************************************
70 *************************************************/
72 /* See local README for interface description. */
75 dnsdb_open(uschar *filename, uschar **errmsg)
77 filename = filename; /* Keep picky compilers happy */
78 errmsg = errmsg; /* Ditto */
79 return (void *)(-1); /* Any non-0 value */
84 /*************************************************
85 * Find entry point for dnsdb *
86 *************************************************/
88 /* See local README for interface description. The query in the "keystring" may
89 consist of a number of parts.
91 (a) If the first significant character is '>' then the next character is the
92 separator character that is used when multiple records are found. The default
95 (b) If the next character is ',' then the next character is the separator
96 character used for multiple items of text in "TXT" records. Alternatively,
97 if the next character is ';' then these multiple items are concatenated with
98 no separator. With neither of these options specified, only the first item
99 is output. Similarly for "SPF" records, but the default for joining multiple
100 items in one SPF record is the empty string, for direct concatenation.
102 (c) If the next sequence of characters is 'defer_FOO' followed by a comma,
103 the defer behaviour is set to FOO. The possible behaviours are: 'strict', where
104 any defer causes the whole lookup to defer; 'lax', where a defer causes the
105 whole lookup to defer only if none of the DNS queries succeeds; and 'never',
106 where all defers are as if the lookup failed. The default is 'lax'.
108 (d) If the next sequence of characters is a sequence of letters and digits
109 followed by '=', it is interpreted as the name of the DNS record type. The
112 (e) Then there follows list of domain names. This is a generalized Exim list,
113 which may start with '<' in order to set a specific separator. The default
114 separator, as always, is colon. */
117 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
118 uschar **result, uschar **errmsg, BOOL *do_cache)
124 int defer_mode = PASS;
127 uschar *outsep = US"\n";
128 uschar *outsep2 = NULL;
129 uschar *equals, *domain, *found;
132 /* Because we're the working in the search pool, we try to reclaim as much
133 store as possible later, so we preallocate the result here */
135 uschar *yield = store_get(size);
141 handle = handle; /* Keep picky compilers happy */
146 /* If the string starts with '>' we change the output separator.
147 If it's followed by ';' or ',' we set the TXT output separator. */
149 while (isspace(*keystring)) keystring++;
150 if (*keystring == '>')
152 outsep = keystring + 1;
154 if (*keystring == ',')
156 outsep2 = keystring + 1;
159 else if (*keystring == ';')
164 while (isspace(*keystring)) keystring++;
167 /* SPF strings should be concatenated without a separator, thus make
168 it the default if not defined (see RFC 4408 section 3.1.3).
169 Multiple SPF records are forbidden (section 3.1.2) but are currently
170 not handled specially, thus they are concatenated with \n by default. */
172 if (type == T_SPF && outsep2 == NULL)
175 /* Check for a defer behaviour keyword. */
177 if (strncmpic(keystring, US"defer_", 6) == 0)
180 if (strncmpic(keystring, US"strict", 6) == 0)
185 else if (strncmpic(keystring, US"lax", 3) == 0)
190 else if (strncmpic(keystring, US"never", 5) == 0)
197 *errmsg = US"unsupported dnsdb defer behaviour";
200 while (isspace(*keystring)) keystring++;
201 if (*keystring++ != ',')
203 *errmsg = US"dnsdb defer behaviour syntax error";
206 while (isspace(*keystring)) keystring++;
209 /* If the keystring contains an = this must be preceded by a valid type name. */
211 if ((equals = Ustrchr(keystring, '=')) != NULL)
214 uschar *tend = equals;
216 while (tend > keystring && isspace(tend[-1])) tend--;
217 len = tend - keystring;
219 for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
221 if (len == Ustrlen(type_names[i]) &&
222 strncmpic(keystring, US type_names[i], len) == 0)
224 type = type_values[i];
229 if (i >= sizeof(type_names)/sizeof(uschar *))
231 *errmsg = US"unsupported DNS record type";
235 keystring = equals + 1;
236 while (isspace(*keystring)) keystring++;
239 /* Initialize the resolver in case this is the first time it has been used. */
241 dns_init(FALSE, FALSE);
243 /* The remainder of the string must be a list of domains. As long as the lookup
244 for at least one of them succeeds, we return success. Failure means that none
247 The original implementation did not support a list of domains. Adding the list
248 feature is compatible, except in one case: when PTR records are being looked up
249 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
250 here: If the type is PTR and no list separator is specified, and the entire
251 remaining string is valid as an IP address, set an impossible separator so that
252 it is treated as one item. */
254 if (type == T_PTR && keystring[0] != '<' &&
255 string_is_ip_address(keystring, NULL) != 0)
258 /* Now scan the list and do a lookup for each item */
260 while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer)))
264 int searchtype = (type == T_CSA)? T_SRV : /* record type we want */
265 (type == T_MXH)? T_MX :
266 (type == T_ZNS)? T_NS : type;
268 /* If the type is PTR or CSA, we have to construct the relevant magic lookup
269 key if the original is an IP address (some experimental protocols are using
270 PTR records for different purposes where the key string is a host name, and
271 Exim's extended CSA can be keyed by domains or IP addresses). This code for
272 doing the reversal is now in a separate function. */
274 if ((type == T_PTR || type == T_CSA) &&
275 string_is_ip_address(domain, NULL) != 0)
277 dns_build_reverse(domain, rbuffer);
281 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
283 /* Do the lookup and sort out the result. There are three special types that
284 are handled specially: T_CSA, T_ZNS and T_MXH. The former two are handled in
285 a special lookup function so that the facility could be used from other
286 parts of the Exim code. The latter affects only what happens later on in
287 this function, but for tidiness it is handled in a similar way. If the
288 lookup fails, continue with the next domain. In the case of DEFER, adjust
289 the final "nothing found" result, but carry on to the next domain. */
292 rc = dns_special_lookup(&dnsa, domain, type, &found);
294 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
295 if (rc != DNS_SUCCEED)
297 if (defer_mode == DEFER) return DEFER; /* always defer */
298 else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
299 continue; /* treat defer as fail */
302 /* Search the returned records */
304 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
306 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
308 if (rr->type != searchtype) continue;
310 /* There may be several addresses from an A6 record. Put the configured
311 separator between them, just as for between several records. However, A6
312 support is not normally configured these days. */
321 for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
323 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
324 yield = string_cat(yield, &size, &ptr, da->address,
325 Ustrlen(da->address));
330 /* Other kinds of record just have one piece of data each, but there may be
331 several of them, of course. */
333 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
335 if (type == T_TXT || type == T_SPF)
339 /* output only the first item of data */
340 yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
345 /* output all items */
347 while (data_offset < rr->size)
349 uschar chunk_len = (rr->data)[data_offset++];
350 if (outsep2[0] != '\0' && data_offset != 1)
351 yield = string_cat(yield, &size, &ptr, outsep2, 1);
352 yield = string_cat(yield, &size, &ptr,
353 (uschar *)((rr->data)+data_offset), chunk_len);
354 data_offset += chunk_len;
358 else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */
360 int priority, weight, port;
362 uschar *p = (uschar *)(rr->data);
366 /* mxh ignores the priority number and includes only the hostnames */
367 GETSHORT(priority, p);
369 else if (type == T_MX)
371 GETSHORT(priority, p);
372 sprintf(CS s, "%d ", priority);
373 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
375 else if (type == T_SRV)
377 GETSHORT(priority, p);
380 sprintf(CS s, "%d %d %d ", priority, weight, port);
381 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
383 else if (type == T_CSA)
385 /* See acl_verify_csa() for more comments about CSA. */
387 GETSHORT(priority, p);
391 if (priority != 1) continue; /* CSA version must be 1 */
393 /* If the CSA record we found is not the one we asked for, analyse
394 the subdomain assertions in the port field, else analyse the direct
395 authorization status in the weight field. */
399 if (port & 1) *s = 'X'; /* explicit authorization required */
400 else *s = '?'; /* no subdomain assertions here */
404 if (weight < 2) *s = 'N'; /* not authorized */
405 else if (weight == 2) *s = 'Y'; /* authorized */
406 else if (weight == 3) *s = '?'; /* unauthorizable */
407 else continue; /* invalid */
411 yield = string_cat(yield, &size, &ptr, s, 2);
414 /* GETSHORT() has advanced the pointer to the target domain. */
416 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
417 (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
419 /* If an overlong response was received, the data will have been
420 truncated and dn_expand may fail. */
424 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
425 "domain=%s", dns_text_type(type), domain);
428 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
430 } /* Loop for list of returned records */
431 } /* Loop for list of domains */
433 /* Reclaim unused memory */
435 store_reset(yield + ptr + 1);
437 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
438 zero and return the result. */
440 if (ptr == 0) return failrc;
448 /*************************************************
449 * Version reporting entry point *
450 *************************************************/
452 /* See local README for interface description. */
454 #include "../version.h"
457 dnsdb_version_report(FILE *f)
460 fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
465 static lookup_info _lookup_info = {
466 US"dnsdb", /* lookup name */
467 lookup_querystyle, /* query style */
468 dnsdb_open, /* open function */
469 NULL, /* check function */
470 dnsdb_find, /* find function */
471 NULL, /* no close function */
472 NULL, /* no tidy function */
473 NULL, /* no quoting function */
474 dnsdb_version_report /* version reporting */
478 #define dnsdb_lookup_module_info _lookup_module_info
481 static lookup_info *_lookup_list[] = { &_lookup_info };
482 lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
484 /* End of lookups/dnsdb.c */