Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
0a49a7a4 | 5 | /* Copyright (c) University of Cambridge 1995 - 2009 */ |
059ec3d9 PH |
6 | /* See the file NOTICE for conditions of use and distribution. */ |
7 | ||
8 | /* Functions for interfacing with the DNS. */ | |
9 | ||
10 | #include "exim.h" | |
11 | ||
12 | ||
13 | /* Function declaration needed for mutual recursion when A6 records | |
14 | are supported. */ | |
15 | ||
16 | #if HAVE_IPV6 | |
17 | #ifdef SUPPORT_A6 | |
18 | static void dns_complete_a6(dns_address ***, dns_answer *, dns_record *, | |
19 | int, uschar *); | |
20 | #endif | |
21 | #endif | |
22 | ||
23 | ||
bef5a11f PH |
24 | /************************************************* |
25 | * Fake DNS resolver * | |
26 | *************************************************/ | |
27 | ||
28 | /* This function is called instead of res_search() when Exim is running in its | |
29 | test harness. It recognizes some special domain names, and uses them to force | |
433a2980 PH |
30 | failure and retry responses (optionally with a delay). Otherwise, it calls an |
31 | external utility that mocks-up a nameserver, if it can find the utility. | |
32 | If not, it passes its arguments on to res_search(). The fake nameserver may | |
33 | also return a code specifying that the name should be passed on. | |
bef5a11f PH |
34 | |
35 | Background: the original test suite required a real nameserver to carry the | |
e7726cbf PH |
36 | test zones, whereas the new test suit has the fake server for portability. This |
37 | code supports both. | |
bef5a11f PH |
38 | |
39 | Arguments: | |
e7726cbf | 40 | domain the domain name |
bef5a11f PH |
41 | type the DNS record type |
42 | answerptr where to put the answer | |
43 | size size of the answer area | |
44 | ||
45 | Returns: length of returned data, or -1 on error (h_errno set) | |
46 | */ | |
47 | ||
48 | static int | |
e7726cbf | 49 | fakens_search(uschar *domain, int type, uschar *answerptr, int size) |
bef5a11f | 50 | { |
e7726cbf | 51 | int len = Ustrlen(domain); |
433a2980 | 52 | int asize = size; /* Locally modified */ |
e7726cbf PH |
53 | uschar *endname; |
54 | uschar name[256]; | |
433a2980 PH |
55 | uschar utilname[256]; |
56 | uschar *aptr = answerptr; /* Locally modified */ | |
57 | struct stat statbuf; | |
58 | ||
59 | /* Remove terminating dot. */ | |
e7726cbf PH |
60 | |
61 | if (domain[len - 1] == '.') len--; | |
62 | Ustrncpy(name, domain, len); | |
63 | name[len] = 0; | |
64 | endname = name + len; | |
bef5a11f | 65 | |
433a2980 PH |
66 | /* This code, for forcing TRY_AGAIN and NO_RECOVERY, is here so that it works |
67 | for the old test suite that uses a real nameserver. When the old test suite is | |
68 | eventually abandoned, this code could be moved into the fakens utility. */ | |
69 | ||
bef5a11f PH |
70 | if (len >= 14 && Ustrcmp(endname - 14, "test.again.dns") == 0) |
71 | { | |
72 | int delay = Uatoi(name); /* digits at the start of the name */ | |
73 | DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n", | |
74 | name, dns_text_type(type)); | |
75 | if (delay > 0) | |
76 | { | |
77 | DEBUG(D_dns) debug_printf("delaying %d seconds\n", delay); | |
78 | sleep(delay); | |
79 | } | |
80 | h_errno = TRY_AGAIN; | |
81 | return -1; | |
82 | } | |
83 | ||
84 | if (len >= 13 && Ustrcmp(endname - 13, "test.fail.dns") == 0) | |
85 | { | |
86 | DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n", | |
87 | name, dns_text_type(type)); | |
88 | h_errno = NO_RECOVERY; | |
89 | return -1; | |
90 | } | |
91 | ||
433a2980 PH |
92 | /* Look for the fakens utility, and if it exists, call it. */ |
93 | ||
94 | (void)string_format(utilname, sizeof(utilname), "%s/../bin/fakens", | |
95 | spool_directory); | |
96 | ||
97 | if (stat(CS utilname, &statbuf) >= 0) | |
bef5a11f | 98 | { |
433a2980 PH |
99 | pid_t pid; |
100 | int infd, outfd, rc; | |
101 | uschar *argv[5]; | |
102 | ||
103 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", | |
104 | name, dns_text_type(type)); | |
105 | ||
106 | argv[0] = utilname; | |
107 | argv[1] = spool_directory; | |
108 | argv[2] = name; | |
109 | argv[3] = dns_text_type(type); | |
110 | argv[4] = NULL; | |
111 | ||
112 | pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE); | |
113 | if (pid < 0) | |
114 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s", | |
115 | strerror(errno)); | |
116 | ||
117 | len = 0; | |
118 | rc = -1; | |
119 | while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0) | |
120 | { | |
121 | len += rc; | |
122 | aptr += rc; /* Don't modify the actual arguments, because they */ | |
123 | asize -= rc; /* may need to be passed on to res_search(). */ | |
124 | } | |
bef5a11f | 125 | |
433a2980 PH |
126 | if (rc < 0) |
127 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s", | |
128 | strerror(errno)); | |
bef5a11f | 129 | |
433a2980 | 130 | switch(child_close(pid, 0)) |
bef5a11f | 131 | { |
433a2980 PH |
132 | case 0: return len; |
133 | case 1: h_errno = HOST_NOT_FOUND; return -1; | |
134 | case 2: h_errno = TRY_AGAIN; return -1; | |
135 | default: | |
136 | case 3: h_errno = NO_RECOVERY; return -1; | |
137 | case 4: h_errno = NO_DATA; return -1; | |
138 | case 5: /* Pass on to res_search() */ | |
139 | DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n"); | |
bef5a11f PH |
140 | } |
141 | } | |
142 | ||
433a2980 | 143 | /* fakens utility not found, or it returned "pass on" */ |
bef5a11f | 144 | |
433a2980 | 145 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
146 | |
147 | return res_search(CS domain, C_IN, type, answerptr, size); | |
bef5a11f PH |
148 | } |
149 | ||
150 | ||
059ec3d9 PH |
151 | |
152 | /************************************************* | |
153 | * Initialize and configure resolver * | |
154 | *************************************************/ | |
155 | ||
156 | /* Initialize the resolver and the storage for holding DNS answers if this is | |
157 | the first time we have been here, and set the resolver options. | |
158 | ||
159 | Arguments: | |
160 | qualify_single TRUE to set the RES_DEFNAMES option | |
161 | search_parents TRUE to set the RES_DNSRCH option | |
162 | ||
163 | Returns: nothing | |
164 | */ | |
165 | ||
166 | void | |
167 | dns_init(BOOL qualify_single, BOOL search_parents) | |
168 | { | |
5bfb4cdf PP |
169 | res_state resp = os_get_dns_resolver_res(); |
170 | ||
171 | if ((resp->options & RES_INIT) == 0) | |
059ec3d9 | 172 | { |
5bfb4cdf PP |
173 | DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */ |
174 | os_put_dns_resolver_res(resp); | |
059ec3d9 | 175 | res_init(); |
5bfb4cdf PP |
176 | DEBUG(D_resolver) resp->options |= RES_DEBUG; |
177 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
178 | } |
179 | ||
5bfb4cdf PP |
180 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
181 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 182 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
183 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
184 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
185 | |
186 | #ifdef RES_USE_EDNS0 | |
187 | if (dns_use_edns0 >= 0) | |
188 | { | |
189 | if (dns_use_edns0) | |
5bfb4cdf | 190 | resp->options |= RES_USE_EDNS0; |
e97d1f08 | 191 | else |
5bfb4cdf | 192 | resp->options &= ~RES_USE_EDNS0; |
e97d1f08 PP |
193 | DEBUG(D_resolver) |
194 | debug_printf("Coerced resolver EDNS0 support %s.\n", | |
195 | dns_use_edns0 ? "on" : "off"); | |
196 | } | |
197 | #else | |
198 | if (dns_use_edns0 >= 0) | |
199 | DEBUG(D_resolver) | |
200 | debug_printf("Unable to %sset EDNS0 without resolver support.\n", | |
201 | dns_use_edns0 ? "" : "un"); | |
202 | #endif | |
5bfb4cdf PP |
203 | |
204 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
205 | } |
206 | ||
207 | ||
208 | ||
209 | /************************************************* | |
210 | * Build key name for PTR records * | |
211 | *************************************************/ | |
212 | ||
213 | /* This function inverts an IP address and adds the relevant domain, to produce | |
214 | a name that can be used to look up PTR records. | |
215 | ||
216 | Arguments: | |
217 | string the IP address as a string | |
218 | buffer a suitable buffer, long enough to hold the result | |
219 | ||
220 | Returns: nothing | |
221 | */ | |
222 | ||
223 | void | |
224 | dns_build_reverse(uschar *string, uschar *buffer) | |
225 | { | |
226 | uschar *p = string + Ustrlen(string); | |
227 | uschar *pp = buffer; | |
228 | ||
229 | /* Handle IPv4 address */ | |
230 | ||
231 | #if HAVE_IPV6 | |
232 | if (Ustrchr(string, ':') == NULL) | |
233 | #endif | |
234 | { | |
235 | int i; | |
236 | for (i = 0; i < 4; i++) | |
237 | { | |
238 | uschar *ppp = p; | |
239 | while (ppp > string && ppp[-1] != '.') ppp--; | |
240 | Ustrncpy(pp, ppp, p - ppp); | |
241 | pp += p - ppp; | |
242 | *pp++ = '.'; | |
243 | p = ppp - 1; | |
244 | } | |
245 | Ustrcpy(pp, "in-addr.arpa"); | |
246 | } | |
247 | ||
248 | /* Handle IPv6 address; convert to binary so as to fill out any | |
249 | abbreviation in the textual form. */ | |
250 | ||
251 | #if HAVE_IPV6 | |
252 | else | |
253 | { | |
254 | int i; | |
255 | int v6[4]; | |
256 | (void)host_aton(string, v6); | |
257 | ||
258 | /* The original specification for IPv6 reverse lookup was to invert each | |
259 | nibble, and look in the ip6.int domain. The domain was subsequently | |
260 | changed to ip6.arpa. */ | |
261 | ||
262 | for (i = 3; i >= 0; i--) | |
263 | { | |
264 | int j; | |
265 | for (j = 0; j < 32; j += 4) | |
266 | { | |
267 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
268 | pp += 2; | |
269 | } | |
270 | } | |
271 | Ustrcpy(pp, "ip6.arpa."); | |
272 | ||
273 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
274 | with A6 records. However, it fell out of favour when they did. The | |
275 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
276 | to make this code do that, but I could not make it work on Solaris 8. The | |
277 | resolver seems to lose the initial backslash somehow. However, now that | |
278 | this style of reverse lookup has been dropped, it doesn't matter. These | |
279 | lines are left here purely for historical interest. */ | |
280 | ||
281 | /************************************************** | |
282 | Ustrcpy(pp, "\\[x"); | |
283 | pp += 3; | |
284 | ||
285 | for (i = 0; i < 4; i++) | |
286 | { | |
287 | sprintf(pp, "%08X", v6[i]); | |
288 | pp += 8; | |
289 | } | |
290 | Ustrcpy(pp, "].ip6.arpa."); | |
291 | **************************************************/ | |
292 | ||
293 | } | |
294 | #endif | |
295 | } | |
296 | ||
297 | ||
298 | ||
299 | ||
300 | /************************************************* | |
301 | * Get next DNS record from answer block * | |
302 | *************************************************/ | |
303 | ||
304 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
305 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
306 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
307 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
308 | |
309 | Arguments: | |
310 | dnsa pointer to dns answer block | |
311 | dnss pointer to dns scan block | |
312 | reset option specifing what portion to scan, as described above | |
313 | ||
314 | Returns: next dns record, or NULL when no more | |
315 | */ | |
316 | ||
317 | dns_record * | |
318 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
319 | { | |
320 | HEADER *h = (HEADER *)dnsa->answer; | |
321 | int namelen; | |
322 | ||
323 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
324 | ||
325 | if (reset != RESET_NEXT) | |
326 | { | |
327 | dnss->rrcount = ntohs(h->qdcount); | |
328 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
329 | ||
330 | /* Skip over questions; failure to expand the name just gives up */ | |
331 | ||
332 | while (dnss->rrcount-- > 0) | |
333 | { | |
334 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
335 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
336 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
337 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
338 | } | |
339 | ||
340 | /* Get the number of answer records. */ | |
341 | ||
342 | dnss->rrcount = ntohs(h->ancount); | |
343 | ||
e5a9dba6 PH |
344 | /* Skip over answers if we want to look at the authority section. Also skip |
345 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
346 | records. */ |
347 | ||
e5a9dba6 PH |
348 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
349 | ||
350 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 351 | { |
059ec3d9 PH |
352 | while (dnss->rrcount-- > 0) |
353 | { | |
354 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
355 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
356 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
357 | dnss->aptr += namelen + 8; /* skip name, type, class & TTL */ | |
358 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
359 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
360 | } | |
e5a9dba6 PH |
361 | dnss->rrcount = (reset == RESET_AUTHORITY) |
362 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
363 | } |
364 | } | |
365 | ||
059ec3d9 PH |
366 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
367 | contains the number of RR records left. */ | |
368 | ||
369 | if (dnss->rrcount-- <= 0) return NULL; | |
370 | ||
371 | /* If expanding the RR domain name fails, behave as if no more records | |
372 | (something safe). */ | |
373 | ||
374 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
375 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
376 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
377 | ||
378 | /* Move the pointer past the name and fill in the rest of the data structure | |
379 | from the following bytes. */ | |
380 | ||
381 | dnss->aptr += namelen; | |
382 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
383 | dnss->aptr += 6; /* Don't want class or TTL */ | |
384 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
385 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
386 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
387 | ||
388 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
389 | for convenience so that the scans can use nice-looking for loops. */ | |
390 | ||
391 | return &(dnss->srr); | |
392 | } | |
393 | ||
394 | ||
395 | ||
396 | ||
397 | /************************************************* | |
398 | * Turn DNS type into text * | |
399 | *************************************************/ | |
400 | ||
885ccd3e PH |
401 | /* Turn the coded record type into a string for printing. All those that Exim |
402 | uses should be included here. | |
059ec3d9 PH |
403 | |
404 | Argument: record type | |
405 | Returns: pointer to string | |
406 | */ | |
407 | ||
408 | uschar * | |
409 | dns_text_type(int t) | |
410 | { | |
411 | switch(t) | |
412 | { | |
33397d19 PH |
413 | case T_A: return US"A"; |
414 | case T_MX: return US"MX"; | |
415 | case T_AAAA: return US"AAAA"; | |
416 | case T_A6: return US"A6"; | |
417 | case T_TXT: return US"TXT"; | |
418 | case T_PTR: return US"PTR"; | |
885ccd3e | 419 | case T_SOA: return US"SOA"; |
33397d19 PH |
420 | case T_SRV: return US"SRV"; |
421 | case T_NS: return US"NS"; | |
8e669ac1 | 422 | case T_CNAME: return US"CNAME"; |
33397d19 | 423 | default: return US"?"; |
059ec3d9 PH |
424 | } |
425 | } | |
426 | ||
427 | ||
428 | ||
429 | /************************************************* | |
430 | * Cache a failed DNS lookup result * | |
431 | *************************************************/ | |
432 | ||
433 | /* We cache failed lookup results so as not to experience timeouts many | |
434 | times for the same domain. We need to retain the resolver options because they | |
435 | may change. For successful lookups, we rely on resolver and/or name server | |
436 | caching. | |
437 | ||
438 | Arguments: | |
439 | name the domain name | |
440 | type the lookup type | |
441 | rc the return code | |
442 | ||
443 | Returns: the return code | |
444 | */ | |
445 | ||
446 | static int | |
447 | dns_return(uschar *name, int type, int rc) | |
448 | { | |
5bfb4cdf | 449 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
450 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); |
451 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 452 | resp->options); |
059ec3d9 PH |
453 | node->data.val = rc; |
454 | (void)tree_insertnode(&tree_dns_fails, node); | |
455 | return rc; | |
456 | } | |
457 | ||
458 | ||
459 | ||
460 | /************************************************* | |
461 | * Do basic DNS lookup * | |
462 | *************************************************/ | |
463 | ||
464 | /* Call the resolver to look up the given domain name, using the given type, | |
465 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
466 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
467 | up nameservers that produce this error continually, so there is the option of | |
468 | providing a list of domains for which this is treated as a non-existent | |
469 | host. | |
470 | ||
471 | Arguments: | |
472 | dnsa pointer to dns_answer structure | |
473 | name name to look up | |
474 | type type of DNS record required (T_A, T_MX, etc) | |
475 | ||
476 | Returns: DNS_SUCCEED successful lookup | |
477 | DNS_NOMATCH name not found (NXDOMAIN) | |
478 | or name contains illegal characters (if checking) | |
30e18802 | 479 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
480 | DNS_NODATA domain exists, but no data for this type (NODATA) |
481 | DNS_AGAIN soft failure, try again later | |
482 | DNS_FAIL DNS failure | |
483 | */ | |
484 | ||
485 | int | |
486 | dns_basic_lookup(dns_answer *dnsa, uschar *name, int type) | |
487 | { | |
488 | #ifndef STAND_ALONE | |
7156b1ef | 489 | int rc = -1; |
059ec3d9 PH |
490 | uschar *save; |
491 | #endif | |
5bfb4cdf | 492 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
493 | |
494 | tree_node *previous; | |
495 | uschar node_name[290]; | |
496 | ||
497 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
498 | a timeout on one domain doesn't happen time and time again for messages that | |
499 | have many addresses in the same domain. We rely on the resolver and name server | |
500 | caching for successful lookups. */ | |
501 | ||
502 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 503 | resp->options); |
059ec3d9 PH |
504 | previous = tree_search(tree_dns_fails, node_name); |
505 | if (previous != NULL) | |
506 | { | |
507 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
508 | name, dns_text_type(type), | |
509 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
510 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
511 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
512 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
513 | return previous->data.val; | |
514 | } | |
515 | ||
059ec3d9 PH |
516 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
517 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
518 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
519 | domains cannot be in the DNS. The check is now done by a regular expression; | |
520 | give it space for substring storage to save it having to get its own if the | |
521 | regex has substrings that are used - the default uses a conditional. | |
522 | ||
523 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
524 | lookup, which constructs the names itself, so they should be OK. Besides, | |
525 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
526 | more.) | |
527 | ||
528 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
529 | ||
530 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
531 | ||
482d1455 | 532 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 PH |
533 | { |
534 | uschar *checkname = name; | |
535 | int ovector[3*(EXPAND_MAXN+1)]; | |
536 | ||
537 | if (regex_check_dns_names == NULL) | |
538 | regex_check_dns_names = | |
539 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
540 | ||
541 | /* For an SRV lookup, skip over the first two components (the service and | |
542 | protocol names, which both start with an underscore). */ | |
543 | ||
544 | if (type == T_SRV) | |
545 | { | |
546 | while (*checkname++ != '.'); | |
547 | while (*checkname++ != '.'); | |
548 | } | |
549 | ||
550 | if (pcre_exec(regex_check_dns_names, NULL, CS checkname, Ustrlen(checkname), | |
551 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) | |
552 | { | |
553 | DEBUG(D_dns) | |
554 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
555 | dns_text_type(type)); | |
556 | host_find_failed_syntax = TRUE; | |
557 | return DNS_NOMATCH; | |
558 | } | |
559 | } | |
560 | ||
561 | #endif /* STAND_ALONE */ | |
562 | ||
563 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
564 | number of bytes the message would need, so we need to check for this case. The |
565 | effect is to truncate overlong data. | |
566 | ||
30e18802 PH |
567 | On some systems, res_search() will recognize "A-for-A" queries and return |
568 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
569 | nameservers are also believed to do this. It is, of course, contrary to the | |
570 | specification of the DNS, so we lock it out. */ | |
571 | ||
572 | if (( | |
573 | #ifdef SUPPORT_A6 | |
574 | type == T_A6 || | |
575 | #endif | |
576 | type == T_A || type == T_AAAA) && | |
577 | string_is_ip_address(name, NULL) != 0) | |
578 | return DNS_NOMATCH; | |
579 | ||
580 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
581 | (res_search), we call fakens_search(), which recognizes certain special |
582 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
583 | ||
584 | if (running_in_test_harness) | |
585 | dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET); | |
586 | else | |
587 | dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET); | |
059ec3d9 | 588 | |
80a47a2c TK |
589 | if (dnsa->answerlen > MAXPACKET) |
590 | { | |
591 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n", | |
592 | name, dns_text_type(type), dnsa->answerlen, MAXPACKET); | |
593 | dnsa->answerlen = MAXPACKET; | |
594 | } | |
059ec3d9 PH |
595 | |
596 | if (dnsa->answerlen < 0) switch (h_errno) | |
597 | { | |
598 | case HOST_NOT_FOUND: | |
599 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
600 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
601 | return dns_return(name, type, DNS_NOMATCH); | |
602 | ||
603 | case TRY_AGAIN: | |
604 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
605 | name, dns_text_type(type)); | |
606 | ||
607 | /* Cut this out for various test programs */ | |
608 | #ifndef STAND_ALONE | |
609 | save = deliver_domain; | |
610 | deliver_domain = name; /* set $domain */ | |
611 | rc = match_isinlist(name, &dns_again_means_nonexist, 0, NULL, NULL, | |
612 | MCL_DOMAIN, TRUE, NULL); | |
613 | deliver_domain = save; | |
614 | if (rc != OK) | |
615 | { | |
616 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
617 | return dns_return(name, type, DNS_AGAIN); | |
618 | } | |
619 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
620 | "DNS_NOMATCH\n", name); | |
621 | return dns_return(name, type, DNS_NOMATCH); | |
622 | ||
623 | #else /* For stand-alone tests */ | |
624 | return dns_return(name, type, DNS_AGAIN); | |
625 | #endif | |
626 | ||
627 | case NO_RECOVERY: | |
628 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
629 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
630 | return dns_return(name, type, DNS_FAIL); | |
631 | ||
632 | case NO_DATA: | |
633 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
634 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
635 | return dns_return(name, type, DNS_NODATA); | |
636 | ||
637 | default: | |
638 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
639 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
640 | return dns_return(name, type, DNS_FAIL); | |
641 | } | |
642 | ||
643 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
644 | name, dns_text_type(type)); | |
645 | ||
646 | return DNS_SUCCEED; | |
647 | } | |
648 | ||
649 | ||
650 | ||
651 | ||
652 | /************************************************ | |
653 | * Do a DNS lookup and handle CNAMES * | |
654 | ************************************************/ | |
655 | ||
656 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
657 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
658 | the DNS, but you are supposed to cope with them if you find them. | |
659 | ||
660 | The assumption is made that if the resolver gives back records of the | |
661 | requested type *and* a CNAME, we don't need to make another call to look up | |
662 | the CNAME. I can't see how it could return only some of the right records. If | |
663 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
664 | won't return any. | |
665 | ||
666 | If fully_qualified_name is not NULL, set it to point to the full name | |
667 | returned by the resolver, if this is different to what it is given, unless | |
668 | the returned name starts with "*" as some nameservers seem to be returning | |
669 | wildcards in this form. | |
670 | ||
671 | Arguments: | |
672 | dnsa pointer to dns_answer structure | |
673 | name domain name to look up | |
674 | type DNS record type (T_A, T_MX, etc) | |
675 | fully_qualified_name if not NULL, return the returned name here if its | |
676 | contents are different (i.e. it must be preset) | |
677 | ||
678 | Returns: DNS_SUCCEED successful lookup | |
679 | DNS_NOMATCH name not found | |
680 | DNS_NODATA no data found | |
681 | DNS_AGAIN soft failure, try again later | |
682 | DNS_FAIL DNS failure | |
683 | */ | |
684 | ||
685 | int | |
686 | dns_lookup(dns_answer *dnsa, uschar *name, int type, uschar **fully_qualified_name) | |
687 | { | |
688 | int i; | |
689 | uschar *orig_name = name; | |
690 | ||
691 | /* Loop to follow CNAME chains so far, but no further... */ | |
692 | ||
693 | for (i = 0; i < 10; i++) | |
694 | { | |
695 | uschar data[256]; | |
696 | dns_record *rr, cname_rr, type_rr; | |
697 | dns_scan dnss; | |
698 | int datalen, rc; | |
699 | ||
700 | /* DNS lookup failures get passed straight back. */ | |
701 | ||
702 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
703 | ||
704 | /* We should have either records of the required type, or a CNAME record, | |
705 | or both. We need to know whether both exist for getting the fully qualified | |
706 | name, but avoid scanning more than necessary. Note that we must copy the | |
707 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
708 | area in the dnsa block. */ | |
709 | ||
710 | cname_rr.data = type_rr.data = NULL; | |
711 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
712 | rr != NULL; | |
713 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
714 | { | |
715 | if (rr->type == type) | |
716 | { | |
717 | if (type_rr.data == NULL) type_rr = *rr; | |
718 | if (cname_rr.data != NULL) break; | |
719 | } | |
720 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
721 | } | |
722 | ||
a2042e78 PH |
723 | /* For the first time round this loop, if a CNAME was found, take the fully |
724 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 725 | |
a2042e78 | 726 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 PH |
727 | { |
728 | if (cname_rr.data != NULL) | |
729 | { | |
730 | if (Ustrcmp(cname_rr.name, *fully_qualified_name) != 0 && | |
731 | cname_rr.name[0] != '*') | |
732 | *fully_qualified_name = string_copy_dnsdomain(cname_rr.name); | |
733 | } | |
734 | else if (type_rr.data != NULL) | |
735 | { | |
75e0e026 PH |
736 | if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 && |
737 | type_rr.name[0] != '*') | |
738 | *fully_qualified_name = string_copy_dnsdomain(type_rr.name); | |
059ec3d9 PH |
739 | } |
740 | } | |
741 | ||
742 | /* If any data records of the correct type were found, we are done. */ | |
743 | ||
744 | if (type_rr.data != NULL) return DNS_SUCCEED; | |
745 | ||
746 | /* If there are no data records, we need to re-scan the DNS using the | |
747 | domain given in the CNAME record, which should exist (otherwise we should | |
748 | have had a failure from dns_lookup). However code against the possibility of | |
749 | its not existing. */ | |
750 | ||
751 | if (cname_rr.data == NULL) return DNS_FAIL; | |
752 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
753 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256); | |
754 | if (datalen < 0) return DNS_FAIL; | |
755 | name = data; | |
a2042e78 PH |
756 | |
757 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); | |
059ec3d9 PH |
758 | } /* Loop back to do another lookup */ |
759 | ||
760 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
761 | right... */ | |
762 | ||
763 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
764 | return DNS_FAIL; | |
765 | } | |
766 | ||
767 | ||
768 | ||
33397d19 PH |
769 | |
770 | ||
771 | ||
772 | /************************************************ | |
773 | * Do a DNS lookup and handle virtual types * | |
774 | ************************************************/ | |
775 | ||
8e669ac1 PH |
776 | /* This function handles some invented "lookup types" that synthesize feature |
777 | not available in the basic types. The special types all have negative values. | |
33397d19 PH |
778 | Positive type values are passed straight on to dns_lookup(). |
779 | ||
780 | Arguments: | |
781 | dnsa pointer to dns_answer structure | |
782 | name domain name to look up | |
783 | type DNS record type (T_A, T_MX, etc or a "special") | |
784 | fully_qualified_name if not NULL, return the returned name here if its | |
785 | contents are different (i.e. it must be preset) | |
786 | ||
787 | Returns: DNS_SUCCEED successful lookup | |
788 | DNS_NOMATCH name not found | |
789 | DNS_NODATA no data found | |
790 | DNS_AGAIN soft failure, try again later | |
791 | DNS_FAIL DNS failure | |
792 | */ | |
793 | ||
794 | int | |
8e669ac1 | 795 | dns_special_lookup(dns_answer *dnsa, uschar *name, int type, |
33397d19 PH |
796 | uschar **fully_qualified_name) |
797 | { | |
798 | if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name); | |
799 | ||
ea3bc19b PH |
800 | /* The "mx hosts only" type doesn't require any special action here */ |
801 | ||
802 | if (type == T_MXH) return dns_lookup(dnsa, name, T_MX, fully_qualified_name); | |
803 | ||
8e669ac1 | 804 | /* Find nameservers for the domain or the nearest enclosing zone, excluding the |
33397d19 PH |
805 | root servers. */ |
806 | ||
807 | if (type == T_ZNS) | |
808 | { | |
809 | uschar *d = name; | |
810 | while (d != 0) | |
811 | { | |
812 | int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name); | |
813 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
814 | while (*d != 0 && *d != '.') d++; | |
8e669ac1 | 815 | if (*d++ == 0) break; |
33397d19 | 816 | } |
8e669ac1 PH |
817 | return DNS_NOMATCH; |
818 | } | |
33397d19 | 819 | |
e5a9dba6 PH |
820 | /* Try to look up the Client SMTP Authorization SRV record for the name. If |
821 | there isn't one, search from the top downwards for a CSA record in a parent | |
822 | domain, which might be making assertions about subdomains. If we find a record | |
823 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
824 | can tell whether to look at the explicit authorization field or the subdomain | |
825 | assertion field. */ | |
826 | ||
827 | if (type == T_CSA) | |
828 | { | |
829 | uschar *srvname, *namesuff, *tld, *p; | |
830 | int priority, weight, port; | |
831 | int limit, rc, i; | |
832 | BOOL ipv6; | |
833 | dns_record *rr; | |
834 | dns_scan dnss; | |
835 | ||
836 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
837 | ||
838 | srvname = string_sprintf("_client._smtp.%s", name); | |
839 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
840 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
841 | { | |
842 | if (rc == DNS_SUCCEED) *fully_qualified_name = name; | |
843 | return rc; | |
844 | } | |
845 | ||
846 | /* Search for CSA subdomain assertion SRV records from the top downwards, | |
847 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
848 | We skip the top level domains to avoid loading their nameservers and because | |
849 | we know they'll never have CSA SRV records. */ | |
850 | ||
851 | namesuff = Ustrrchr(name, '.'); | |
852 | if (namesuff == NULL) return DNS_NOMATCH; | |
853 | tld = namesuff + 1; | |
854 | ipv6 = FALSE; | |
855 | limit = dns_csa_search_limit; | |
856 | ||
857 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
858 | ||
859 | if (strcmpic(namesuff, US".arpa") == 0) | |
860 | { | |
861 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
862 | { | |
863 | namesuff -= 8; | |
864 | tld = namesuff + 1; | |
865 | limit = 3; | |
866 | } | |
867 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
868 | { | |
869 | namesuff -= 4; | |
870 | tld = namesuff + 1; | |
871 | ipv6 = TRUE; | |
872 | limit = 3; | |
873 | } | |
874 | } | |
875 | ||
876 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); | |
877 | ||
878 | /* Do not perform the search if the top level or 2nd level domains do not | |
879 | exist. This is quite common, and when it occurs all the search queries would | |
880 | go to the root or TLD name servers, which is not friendly. So we check the | |
881 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
882 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
883 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
884 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
885 | ||
886 | if (rc == DNS_NOMATCH) | |
887 | { | |
888 | /* This is really gross. The successful return value from res_search() is | |
889 | the packet length, which is stored in dnsa->answerlen. If we get a | |
890 | negative DNS reply then res_search() returns -1, which causes the bounds | |
891 | checks for name decompression to fail when it is treated as a packet | |
892 | length, which in turn causes the authority search to fail. The correct | |
893 | packet length has been lost inside libresolv, so we have to guess a | |
894 | replacement value. (The only way to fix this properly would be to | |
895 | re-implement res_search() and res_query() so that they don't muddle their | |
896 | success and packet length return values.) For added safety we only reset | |
897 | the packet length if the packet header looks plausible. */ | |
898 | ||
899 | HEADER *h = (HEADER *)dnsa->answer; | |
900 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
901 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
902 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
903 | && ntohs(h->nscount) >= 1) | |
904 | dnsa->answerlen = MAXPACKET; | |
905 | ||
906 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
907 | rr != NULL; | |
908 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
909 | if (rr->type != T_SOA) continue; | |
910 | else if (strcmpic(rr->name, US"") == 0 || | |
911 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
912 | else break; | |
913 | } | |
914 | ||
915 | for (i = 0; i < limit; i++) | |
916 | { | |
917 | if (ipv6) | |
918 | { | |
919 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
920 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
921 | namesuff -= 8; | |
922 | if (namesuff <= name) return DNS_NOMATCH; | |
923 | } | |
924 | else | |
925 | /* Find the start of the preceding domain name label. */ | |
926 | do | |
927 | if (--namesuff <= name) return DNS_NOMATCH; | |
928 | while (*namesuff != '.'); | |
929 | ||
930 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
931 | ||
932 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
933 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
934 | if (rc == DNS_AGAIN) return rc; | |
935 | if (rc != DNS_SUCCEED) continue; | |
936 | ||
937 | /* Check that the SRV record we have found is worth returning. We don't | |
938 | just return the first one we find, because some lower level SRV record | |
939 | might make stricter assertions than its parent domain. */ | |
940 | ||
941 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
942 | rr != NULL; | |
943 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
944 | { | |
945 | if (rr->type != T_SRV) continue; | |
946 | ||
947 | /* Extract the numerical SRV fields (p is incremented) */ | |
948 | p = rr->data; | |
949 | GETSHORT(priority, p); | |
950 | GETSHORT(weight, p); | |
951 | GETSHORT(port, p); | |
952 | ||
953 | /* Check the CSA version number */ | |
954 | if (priority != 1) continue; | |
955 | ||
956 | /* If it's making an interesting assertion, return this response. */ | |
957 | if (port & 1) | |
958 | { | |
959 | *fully_qualified_name = namesuff + 1; | |
960 | return DNS_SUCCEED; | |
961 | } | |
962 | } | |
963 | } | |
964 | return DNS_NOMATCH; | |
965 | } | |
966 | ||
33397d19 PH |
967 | /* Control should never reach here */ |
968 | ||
969 | return DNS_FAIL; | |
970 | } | |
971 | ||
972 | ||
973 | ||
059ec3d9 PH |
974 | /* Support for A6 records has been commented out since they were demoted to |
975 | experimental status at IETF 51. */ | |
976 | ||
977 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
978 | ||
979 | /************************************************* | |
980 | * Search DNS block for prefix RRs * | |
981 | *************************************************/ | |
982 | ||
983 | /* Called from dns_complete_a6() to search an additional section or a main | |
984 | answer section for required prefix records to complete an IPv6 address obtained | |
985 | from an A6 record. For each prefix record, a recursive call to dns_complete_a6 | |
986 | is made, with a new copy of the address so far. | |
987 | ||
988 | Arguments: | |
989 | dnsa the DNS answer block | |
990 | which RESET_ADDITIONAL or RESET_ANSWERS | |
991 | name name of prefix record | |
992 | yptrptr pointer to the pointer that points to where to hang the next | |
993 | dns_address structure | |
994 | bits number of bits we have already got | |
995 | bitvec the bits we have already got | |
996 | ||
997 | Returns: TRUE if any records were found | |
998 | */ | |
999 | ||
1000 | static BOOL | |
1001 | dns_find_prefix(dns_answer *dnsa, int which, uschar *name, dns_address | |
1002 | ***yptrptr, int bits, uschar *bitvec) | |
1003 | { | |
1004 | BOOL yield = FALSE; | |
1005 | dns_record *rr; | |
1006 | dns_scan dnss; | |
1007 | ||
1008 | for (rr = dns_next_rr(dnsa, &dnss, which); | |
1009 | rr != NULL; | |
1010 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1011 | { | |
1012 | uschar cbitvec[16]; | |
1013 | if (rr->type != T_A6 || strcmpic(rr->name, name) != 0) continue; | |
1014 | yield = TRUE; | |
1015 | memcpy(cbitvec, bitvec, sizeof(cbitvec)); | |
1016 | dns_complete_a6(yptrptr, dnsa, rr, bits, cbitvec); | |
1017 | } | |
1018 | ||
1019 | return yield; | |
1020 | } | |
1021 | ||
1022 | ||
1023 | ||
1024 | /************************************************* | |
1025 | * Follow chains of A6 records * | |
1026 | *************************************************/ | |
1027 | ||
1028 | /* A6 records may be incomplete, with pointers to other records containing more | |
1029 | bits of the address. There can be a tree structure, leading to a number of | |
1030 | addresses originating from a single initial A6 record. | |
1031 | ||
1032 | Arguments: | |
1033 | yptrptr pointer to the pointer that points to where to hang the next | |
1034 | dns_address structure | |
1035 | dnsa the current DNS answer block | |
1036 | rr the RR we have at present | |
1037 | bits number of bits we have already got | |
1038 | bitvec the bits we have already got | |
1039 | ||
1040 | Returns: nothing | |
1041 | */ | |
1042 | ||
1043 | static void | |
1044 | dns_complete_a6(dns_address ***yptrptr, dns_answer *dnsa, dns_record *rr, | |
1045 | int bits, uschar *bitvec) | |
1046 | { | |
1047 | static uschar bitmask[] = { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 }; | |
1048 | uschar *p = (uschar *)(rr->data); | |
1049 | int prefix_len, suffix_len; | |
1050 | int i, j, k; | |
1051 | uschar *chainptr; | |
1052 | uschar chain[264]; | |
1053 | dns_answer cdnsa; | |
1054 | ||
1055 | /* The prefix length is the first byte. It defines the prefix which is missing | |
1056 | from the data in this record as a number of bits. Zero means this is the end of | |
1057 | a chain. The suffix is the data in this record; only sufficient bytes to hold | |
1058 | it are supplied. There may be zero bytes. We have to ignore trailing bits that | |
1059 | we have already obtained from earlier RRs in the chain. */ | |
1060 | ||
1061 | prefix_len = *p++; /* bits */ | |
1062 | suffix_len = (128 - prefix_len + 7)/8; /* bytes */ | |
1063 | ||
1064 | /* If the prefix in this record is greater than the prefix in the previous | |
1065 | record in the chain, we have to ignore the record (RFC 2874). */ | |
1066 | ||
1067 | if (prefix_len > 128 - bits) return; | |
1068 | ||
1069 | /* In this little loop, the number of bits up to and including the current byte | |
1070 | is held in k. If we have none of the bits in this byte, we can just or it into | |
1071 | the current data. If we have all of the bits in this byte, we skip it. | |
1072 | Otherwise, some masking has to be done. */ | |
1073 | ||
1074 | for (i = suffix_len - 1, j = 15, k = 8; i >= 0; i--) | |
1075 | { | |
1076 | int required = k - bits; | |
1077 | if (required >= 8) bitvec[j] |= p[i]; | |
1078 | else if (required > 0) bitvec[j] |= p[i] & bitmask[required]; | |
1079 | j--; /* I tried putting these in the "for" statement, but gcc muttered */ | |
1080 | k += 8; /* about computed values not being used. */ | |
1081 | } | |
1082 | ||
1083 | /* If the prefix_length is zero, we are at the end of a chain. Build a | |
1084 | dns_address item with the current data, hang it onto the end of the chain, | |
1085 | adjust the hanging pointer, and we are done. */ | |
1086 | ||
1087 | if (prefix_len == 0) | |
1088 | { | |
1089 | dns_address *new = store_get(sizeof(dns_address) + 50); | |
1090 | inet_ntop(AF_INET6, bitvec, CS new->address, 50); | |
1091 | new->next = NULL; | |
1092 | **yptrptr = new; | |
1093 | *yptrptr = &(new->next); | |
1094 | return; | |
1095 | } | |
1096 | ||
1097 | /* Prefix length is not zero. Reset the number of bits that we have collected | |
1098 | so far, and extract the chain name. */ | |
1099 | ||
1100 | bits = 128 - prefix_len; | |
1101 | p += suffix_len; | |
1102 | ||
1103 | chainptr = chain; | |
1104 | while ((i = *p++) != 0) | |
1105 | { | |
1106 | if (chainptr != chain) *chainptr++ = '.'; | |
1107 | memcpy(chainptr, p, i); | |
1108 | chainptr += i; | |
1109 | p += i; | |
1110 | } | |
1111 | *chainptr = 0; | |
1112 | chainptr = chain; | |
1113 | ||
1114 | /* Now scan the current DNS response record to see if the additional section | |
1115 | contains the records we want. This processing can be cut out for testing | |
1116 | purposes. */ | |
1117 | ||
1118 | if (dns_find_prefix(dnsa, RESET_ADDITIONAL, chainptr, yptrptr, bits, bitvec)) | |
1119 | return; | |
1120 | ||
1121 | /* No chain records were found in the current DNS response block. Do a new DNS | |
1122 | lookup to try to find these records. This opens up the possibility of DNS | |
1123 | failures. We ignore them at this point; if all branches of the tree fail, there | |
1124 | will be no addresses at the end. */ | |
1125 | ||
1126 | if (dns_lookup(&cdnsa, chainptr, T_A6, NULL) == DNS_SUCCEED) | |
1127 | (void)dns_find_prefix(&cdnsa, RESET_ANSWERS, chainptr, yptrptr, bits, bitvec); | |
1128 | } | |
1129 | #endif /* HAVE_IPV6 && defined(SUPPORT_A6) */ | |
1130 | ||
1131 | ||
1132 | ||
1133 | ||
1134 | /************************************************* | |
1135 | * Get address(es) from DNS record * | |
1136 | *************************************************/ | |
1137 | ||
1138 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
1139 | supported) for an IPv6 address. In the A6 case, there may be several addresses, | |
1140 | generated by following chains. A recursive function does all the hard work. A6 | |
1141 | records now look like passing into history, so the code is only included when | |
1142 | explicitly asked for. | |
1143 | ||
1144 | Argument: | |
1145 | dnsa the DNS answer block | |
1146 | rr the RR | |
1147 | ||
1148 | Returns: pointer a chain of dns_address items | |
1149 | */ | |
1150 | ||
1151 | dns_address * | |
1152 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1153 | { | |
1154 | dns_address *yield = NULL; | |
1155 | ||
1156 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1157 | dns_address **yieldptr = &yield; | |
1158 | uschar bitvec[16]; | |
1159 | #else | |
1160 | dnsa = dnsa; /* Stop picky compilers warning */ | |
1161 | #endif | |
1162 | ||
1163 | if (rr->type == T_A) | |
1164 | { | |
1165 | uschar *p = (uschar *)(rr->data); | |
1166 | yield = store_get(sizeof(dns_address) + 20); | |
1167 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1168 | yield->next = NULL; | |
1169 | } | |
1170 | ||
1171 | #if HAVE_IPV6 | |
1172 | ||
1173 | #ifdef SUPPORT_A6 | |
1174 | else if (rr->type == T_A6) | |
1175 | { | |
1176 | memset(bitvec, 0, sizeof(bitvec)); | |
1177 | dns_complete_a6(&yieldptr, dnsa, rr, 0, bitvec); | |
1178 | } | |
1179 | #endif /* SUPPORT_A6 */ | |
1180 | ||
1181 | else | |
1182 | { | |
1183 | yield = store_get(sizeof(dns_address) + 50); | |
1184 | inet_ntop(AF_INET6, (uschar *)(rr->data), CS yield->address, 50); | |
1185 | yield->next = NULL; | |
1186 | } | |
1187 | #endif /* HAVE_IPV6 */ | |
1188 | ||
1189 | return yield; | |
1190 | } | |
1191 | ||
1192 | /* End of dns.c */ |