Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
5a66c31b | 5 | /* Copyright (c) University of Cambridge 1995 - 2014 */ |
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 | |
1dc92d5a | 49 | fakens_search(const 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 | |
8c51eead | 162 | use_dnssec TRUE to set the RES_USE_DNSSEC option |
059ec3d9 PH |
163 | |
164 | Returns: nothing | |
165 | */ | |
166 | ||
167 | void | |
8c51eead | 168 | dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec) |
059ec3d9 | 169 | { |
5bfb4cdf PP |
170 | res_state resp = os_get_dns_resolver_res(); |
171 | ||
172 | if ((resp->options & RES_INIT) == 0) | |
059ec3d9 | 173 | { |
5bfb4cdf PP |
174 | DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */ |
175 | os_put_dns_resolver_res(resp); | |
059ec3d9 | 176 | res_init(); |
5bfb4cdf PP |
177 | DEBUG(D_resolver) resp->options |= RES_DEBUG; |
178 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
179 | } |
180 | ||
5bfb4cdf PP |
181 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
182 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 183 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
184 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
185 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
186 | |
187 | #ifdef RES_USE_EDNS0 | |
188 | if (dns_use_edns0 >= 0) | |
189 | { | |
190 | if (dns_use_edns0) | |
5bfb4cdf | 191 | resp->options |= RES_USE_EDNS0; |
e97d1f08 | 192 | else |
5bfb4cdf | 193 | resp->options &= ~RES_USE_EDNS0; |
e97d1f08 PP |
194 | DEBUG(D_resolver) |
195 | debug_printf("Coerced resolver EDNS0 support %s.\n", | |
196 | dns_use_edns0 ? "on" : "off"); | |
197 | } | |
198 | #else | |
199 | if (dns_use_edns0 >= 0) | |
200 | DEBUG(D_resolver) | |
201 | debug_printf("Unable to %sset EDNS0 without resolver support.\n", | |
202 | dns_use_edns0 ? "" : "un"); | |
203 | #endif | |
5bfb4cdf | 204 | |
1f4a55da PP |
205 | #ifndef DISABLE_DNSSEC |
206 | # ifdef RES_USE_DNSSEC | |
207 | # ifndef RES_USE_EDNS0 | |
208 | # error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ... | |
209 | # endif | |
8c51eead JH |
210 | if (use_dnssec) |
211 | resp->options |= RES_USE_DNSSEC; | |
0fbd9bff | 212 | if (dns_dnssec_ok >= 0) |
1f4a55da | 213 | { |
0fbd9bff | 214 | if (dns_use_edns0 == 0 && dns_dnssec_ok != 0) |
1f4a55da PP |
215 | { |
216 | DEBUG(D_resolver) | |
0fbd9bff | 217 | debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n"); |
1f4a55da PP |
218 | } |
219 | else | |
220 | { | |
0fbd9bff | 221 | if (dns_dnssec_ok) |
1f4a55da PP |
222 | resp->options |= RES_USE_DNSSEC; |
223 | else | |
224 | resp->options &= ~RES_USE_DNSSEC; | |
225 | DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n", | |
0fbd9bff | 226 | dns_dnssec_ok ? "on" : "off"); |
1f4a55da PP |
227 | } |
228 | } | |
229 | # else | |
0fbd9bff | 230 | if (dns_dnssec_ok >= 0) |
1f4a55da PP |
231 | DEBUG(D_resolver) |
232 | debug_printf("Unable to %sset DNSSEC without resolver support.\n", | |
0fbd9bff | 233 | dns_dnssec_ok ? "" : "un"); |
8c51eead JH |
234 | if (use_dnssec) |
235 | DEBUG(D_resolver) | |
93d4b03a | 236 | debug_printf("Unable to set DNSSEC without resolver support.\n"); |
1f4a55da PP |
237 | # endif |
238 | #endif /* DISABLE_DNSSEC */ | |
239 | ||
5bfb4cdf | 240 | os_put_dns_resolver_res(resp); |
059ec3d9 PH |
241 | } |
242 | ||
243 | ||
244 | ||
245 | /************************************************* | |
246 | * Build key name for PTR records * | |
247 | *************************************************/ | |
248 | ||
249 | /* This function inverts an IP address and adds the relevant domain, to produce | |
250 | a name that can be used to look up PTR records. | |
251 | ||
252 | Arguments: | |
253 | string the IP address as a string | |
254 | buffer a suitable buffer, long enough to hold the result | |
255 | ||
256 | Returns: nothing | |
257 | */ | |
258 | ||
259 | void | |
260 | dns_build_reverse(uschar *string, uschar *buffer) | |
261 | { | |
262 | uschar *p = string + Ustrlen(string); | |
263 | uschar *pp = buffer; | |
264 | ||
265 | /* Handle IPv4 address */ | |
266 | ||
267 | #if HAVE_IPV6 | |
268 | if (Ustrchr(string, ':') == NULL) | |
269 | #endif | |
270 | { | |
271 | int i; | |
272 | for (i = 0; i < 4; i++) | |
273 | { | |
274 | uschar *ppp = p; | |
275 | while (ppp > string && ppp[-1] != '.') ppp--; | |
276 | Ustrncpy(pp, ppp, p - ppp); | |
277 | pp += p - ppp; | |
278 | *pp++ = '.'; | |
279 | p = ppp - 1; | |
280 | } | |
281 | Ustrcpy(pp, "in-addr.arpa"); | |
282 | } | |
283 | ||
284 | /* Handle IPv6 address; convert to binary so as to fill out any | |
285 | abbreviation in the textual form. */ | |
286 | ||
287 | #if HAVE_IPV6 | |
288 | else | |
289 | { | |
290 | int i; | |
291 | int v6[4]; | |
292 | (void)host_aton(string, v6); | |
293 | ||
294 | /* The original specification for IPv6 reverse lookup was to invert each | |
295 | nibble, and look in the ip6.int domain. The domain was subsequently | |
296 | changed to ip6.arpa. */ | |
297 | ||
298 | for (i = 3; i >= 0; i--) | |
299 | { | |
300 | int j; | |
301 | for (j = 0; j < 32; j += 4) | |
302 | { | |
303 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
304 | pp += 2; | |
305 | } | |
306 | } | |
307 | Ustrcpy(pp, "ip6.arpa."); | |
308 | ||
309 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
310 | with A6 records. However, it fell out of favour when they did. The | |
311 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
312 | to make this code do that, but I could not make it work on Solaris 8. The | |
313 | resolver seems to lose the initial backslash somehow. However, now that | |
314 | this style of reverse lookup has been dropped, it doesn't matter. These | |
315 | lines are left here purely for historical interest. */ | |
316 | ||
317 | /************************************************** | |
318 | Ustrcpy(pp, "\\[x"); | |
319 | pp += 3; | |
320 | ||
321 | for (i = 0; i < 4; i++) | |
322 | { | |
323 | sprintf(pp, "%08X", v6[i]); | |
324 | pp += 8; | |
325 | } | |
326 | Ustrcpy(pp, "].ip6.arpa."); | |
327 | **************************************************/ | |
328 | ||
329 | } | |
330 | #endif | |
331 | } | |
332 | ||
333 | ||
334 | ||
335 | ||
336 | /************************************************* | |
337 | * Get next DNS record from answer block * | |
338 | *************************************************/ | |
339 | ||
340 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
341 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
342 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
343 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
344 | |
345 | Arguments: | |
346 | dnsa pointer to dns answer block | |
347 | dnss pointer to dns scan block | |
348 | reset option specifing what portion to scan, as described above | |
349 | ||
350 | Returns: next dns record, or NULL when no more | |
351 | */ | |
352 | ||
353 | dns_record * | |
354 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
355 | { | |
356 | HEADER *h = (HEADER *)dnsa->answer; | |
357 | int namelen; | |
358 | ||
359 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
360 | ||
361 | if (reset != RESET_NEXT) | |
362 | { | |
363 | dnss->rrcount = ntohs(h->qdcount); | |
364 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
365 | ||
366 | /* Skip over questions; failure to expand the name just gives up */ | |
367 | ||
368 | while (dnss->rrcount-- > 0) | |
369 | { | |
370 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
371 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
372 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
373 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
374 | } | |
375 | ||
376 | /* Get the number of answer records. */ | |
377 | ||
378 | dnss->rrcount = ntohs(h->ancount); | |
379 | ||
e5a9dba6 PH |
380 | /* Skip over answers if we want to look at the authority section. Also skip |
381 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
382 | records. */ |
383 | ||
e5a9dba6 PH |
384 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
385 | ||
386 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 387 | { |
059ec3d9 PH |
388 | while (dnss->rrcount-- > 0) |
389 | { | |
390 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
391 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
392 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
393 | dnss->aptr += namelen + 8; /* skip name, type, class & TTL */ | |
394 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
395 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
396 | } | |
e5a9dba6 PH |
397 | dnss->rrcount = (reset == RESET_AUTHORITY) |
398 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
399 | } |
400 | } | |
401 | ||
059ec3d9 PH |
402 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
403 | contains the number of RR records left. */ | |
404 | ||
405 | if (dnss->rrcount-- <= 0) return NULL; | |
406 | ||
407 | /* If expanding the RR domain name fails, behave as if no more records | |
408 | (something safe). */ | |
409 | ||
410 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
411 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
412 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
413 | ||
414 | /* Move the pointer past the name and fill in the rest of the data structure | |
415 | from the following bytes. */ | |
416 | ||
417 | dnss->aptr += namelen; | |
418 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
419 | dnss->aptr += 6; /* Don't want class or TTL */ | |
420 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
421 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
422 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
423 | ||
424 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
425 | for convenience so that the scans can use nice-looking for loops. */ | |
426 | ||
427 | return &(dnss->srr); | |
428 | } | |
429 | ||
430 | ||
431 | ||
432 | ||
1f4a55da PP |
433 | /************************************************* |
434 | * Return whether AD bit set in DNS result * | |
435 | *************************************************/ | |
436 | ||
437 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
438 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
439 | (AD = Authentic Data) | |
440 | ||
441 | Argument: pointer to dns answer block | |
442 | Returns: bool indicating presence of AD bit | |
443 | */ | |
444 | ||
445 | BOOL | |
4a142059 | 446 | dns_is_secure(const dns_answer * dnsa) |
1f4a55da PP |
447 | { |
448 | #ifdef DISABLE_DNSSEC | |
449 | DEBUG(D_dns) | |
450 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
451 | return FALSE; | |
452 | #else | |
453 | HEADER *h = (HEADER *)dnsa->answer; | |
454 | return h->ad ? TRUE : FALSE; | |
455 | #endif | |
456 | } | |
457 | ||
4a142059 JH |
458 | static void |
459 | dns_set_insecure(dns_answer * dnsa) | |
460 | { | |
461 | HEADER * h = (HEADER *)dnsa->answer; | |
462 | h->ad = 0; | |
463 | } | |
464 | ||
1f4a55da PP |
465 | |
466 | ||
467 | ||
059ec3d9 PH |
468 | /************************************************* |
469 | * Turn DNS type into text * | |
470 | *************************************************/ | |
471 | ||
885ccd3e PH |
472 | /* Turn the coded record type into a string for printing. All those that Exim |
473 | uses should be included here. | |
059ec3d9 PH |
474 | |
475 | Argument: record type | |
476 | Returns: pointer to string | |
477 | */ | |
478 | ||
479 | uschar * | |
480 | dns_text_type(int t) | |
481 | { | |
482 | switch(t) | |
483 | { | |
33397d19 PH |
484 | case T_A: return US"A"; |
485 | case T_MX: return US"MX"; | |
486 | case T_AAAA: return US"AAAA"; | |
487 | case T_A6: return US"A6"; | |
488 | case T_TXT: return US"TXT"; | |
eae0036b | 489 | case T_SPF: return US"SPF"; |
33397d19 | 490 | case T_PTR: return US"PTR"; |
885ccd3e | 491 | case T_SOA: return US"SOA"; |
33397d19 PH |
492 | case T_SRV: return US"SRV"; |
493 | case T_NS: return US"NS"; | |
8e669ac1 | 494 | case T_CNAME: return US"CNAME"; |
1e06383a | 495 | case T_TLSA: return US"TLSA"; |
33397d19 | 496 | default: return US"?"; |
059ec3d9 PH |
497 | } |
498 | } | |
499 | ||
500 | ||
501 | ||
502 | /************************************************* | |
503 | * Cache a failed DNS lookup result * | |
504 | *************************************************/ | |
505 | ||
506 | /* We cache failed lookup results so as not to experience timeouts many | |
507 | times for the same domain. We need to retain the resolver options because they | |
508 | may change. For successful lookups, we rely on resolver and/or name server | |
509 | caching. | |
510 | ||
511 | Arguments: | |
512 | name the domain name | |
513 | type the lookup type | |
514 | rc the return code | |
515 | ||
516 | Returns: the return code | |
517 | */ | |
518 | ||
519 | static int | |
1dc92d5a | 520 | dns_return(const uschar * name, int type, int rc) |
059ec3d9 | 521 | { |
5bfb4cdf | 522 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
523 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); |
524 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 525 | resp->options); |
059ec3d9 PH |
526 | node->data.val = rc; |
527 | (void)tree_insertnode(&tree_dns_fails, node); | |
528 | return rc; | |
529 | } | |
530 | ||
531 | ||
532 | ||
533 | /************************************************* | |
534 | * Do basic DNS lookup * | |
535 | *************************************************/ | |
536 | ||
537 | /* Call the resolver to look up the given domain name, using the given type, | |
538 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
539 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
540 | up nameservers that produce this error continually, so there is the option of | |
541 | providing a list of domains for which this is treated as a non-existent | |
542 | host. | |
543 | ||
544 | Arguments: | |
545 | dnsa pointer to dns_answer structure | |
546 | name name to look up | |
547 | type type of DNS record required (T_A, T_MX, etc) | |
548 | ||
549 | Returns: DNS_SUCCEED successful lookup | |
550 | DNS_NOMATCH name not found (NXDOMAIN) | |
551 | or name contains illegal characters (if checking) | |
30e18802 | 552 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
553 | DNS_NODATA domain exists, but no data for this type (NODATA) |
554 | DNS_AGAIN soft failure, try again later | |
555 | DNS_FAIL DNS failure | |
556 | */ | |
557 | ||
558 | int | |
1dc92d5a | 559 | dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type) |
059ec3d9 PH |
560 | { |
561 | #ifndef STAND_ALONE | |
7156b1ef | 562 | int rc = -1; |
059ec3d9 PH |
563 | uschar *save; |
564 | #endif | |
5bfb4cdf | 565 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
566 | |
567 | tree_node *previous; | |
568 | uschar node_name[290]; | |
569 | ||
570 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
571 | a timeout on one domain doesn't happen time and time again for messages that | |
572 | have many addresses in the same domain. We rely on the resolver and name server | |
573 | caching for successful lookups. */ | |
574 | ||
575 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 576 | resp->options); |
059ec3d9 PH |
577 | previous = tree_search(tree_dns_fails, node_name); |
578 | if (previous != NULL) | |
579 | { | |
580 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
581 | name, dns_text_type(type), | |
582 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
583 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
584 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
585 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
586 | return previous->data.val; | |
587 | } | |
588 | ||
059ec3d9 PH |
589 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
590 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
591 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
592 | domains cannot be in the DNS. The check is now done by a regular expression; | |
593 | give it space for substring storage to save it having to get its own if the | |
594 | regex has substrings that are used - the default uses a conditional. | |
595 | ||
596 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
597 | lookup, which constructs the names itself, so they should be OK. Besides, | |
598 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
599 | more.) | |
600 | ||
601 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
602 | ||
603 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
604 | ||
482d1455 | 605 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 | 606 | { |
1dc92d5a | 607 | const uschar *checkname = name; |
059ec3d9 PH |
608 | int ovector[3*(EXPAND_MAXN+1)]; |
609 | ||
610 | if (regex_check_dns_names == NULL) | |
611 | regex_check_dns_names = | |
612 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
613 | ||
614 | /* For an SRV lookup, skip over the first two components (the service and | |
615 | protocol names, which both start with an underscore). */ | |
616 | ||
b4161d10 | 617 | if (type == T_SRV || type == T_TLSA) |
059ec3d9 PH |
618 | { |
619 | while (*checkname++ != '.'); | |
620 | while (*checkname++ != '.'); | |
621 | } | |
622 | ||
1dc92d5a | 623 | if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname), |
059ec3d9 PH |
624 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) |
625 | { | |
626 | DEBUG(D_dns) | |
627 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
628 | dns_text_type(type)); | |
629 | host_find_failed_syntax = TRUE; | |
630 | return DNS_NOMATCH; | |
631 | } | |
632 | } | |
633 | ||
634 | #endif /* STAND_ALONE */ | |
635 | ||
636 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
637 | number of bytes the message would need, so we need to check for this case. The |
638 | effect is to truncate overlong data. | |
639 | ||
30e18802 PH |
640 | On some systems, res_search() will recognize "A-for-A" queries and return |
641 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
642 | nameservers are also believed to do this. It is, of course, contrary to the | |
643 | specification of the DNS, so we lock it out. */ | |
644 | ||
645 | if (( | |
646 | #ifdef SUPPORT_A6 | |
647 | type == T_A6 || | |
648 | #endif | |
649 | type == T_A || type == T_AAAA) && | |
650 | string_is_ip_address(name, NULL) != 0) | |
651 | return DNS_NOMATCH; | |
652 | ||
653 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
654 | (res_search), we call fakens_search(), which recognizes certain special |
655 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
656 | ||
657 | if (running_in_test_harness) | |
658 | dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET); | |
659 | else | |
1dc92d5a | 660 | dnsa->answerlen = res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET); |
059ec3d9 | 661 | |
80a47a2c TK |
662 | if (dnsa->answerlen > MAXPACKET) |
663 | { | |
664 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n", | |
665 | name, dns_text_type(type), dnsa->answerlen, MAXPACKET); | |
666 | dnsa->answerlen = MAXPACKET; | |
667 | } | |
059ec3d9 PH |
668 | |
669 | if (dnsa->answerlen < 0) switch (h_errno) | |
670 | { | |
671 | case HOST_NOT_FOUND: | |
672 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
673 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
674 | return dns_return(name, type, DNS_NOMATCH); | |
675 | ||
676 | case TRY_AGAIN: | |
677 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
678 | name, dns_text_type(type)); | |
679 | ||
680 | /* Cut this out for various test programs */ | |
1dc92d5a | 681 | #ifndef STAND_ALONE |
059ec3d9 | 682 | save = deliver_domain; |
1dc92d5a | 683 | deliver_domain = string_copy(name); /* set $domain */ |
059ec3d9 PH |
684 | rc = match_isinlist(name, &dns_again_means_nonexist, 0, NULL, NULL, |
685 | MCL_DOMAIN, TRUE, NULL); | |
686 | deliver_domain = save; | |
687 | if (rc != OK) | |
688 | { | |
689 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
690 | return dns_return(name, type, DNS_AGAIN); | |
691 | } | |
692 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
693 | "DNS_NOMATCH\n", name); | |
694 | return dns_return(name, type, DNS_NOMATCH); | |
695 | ||
1dc92d5a | 696 | #else /* For stand-alone tests */ |
059ec3d9 | 697 | return dns_return(name, type, DNS_AGAIN); |
1dc92d5a | 698 | #endif |
059ec3d9 PH |
699 | |
700 | case NO_RECOVERY: | |
701 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
702 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
703 | return dns_return(name, type, DNS_FAIL); | |
704 | ||
705 | case NO_DATA: | |
706 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
707 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
708 | return dns_return(name, type, DNS_NODATA); | |
709 | ||
710 | default: | |
711 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
712 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
713 | return dns_return(name, type, DNS_FAIL); | |
714 | } | |
715 | ||
716 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
717 | name, dns_text_type(type)); | |
718 | ||
719 | return DNS_SUCCEED; | |
720 | } | |
721 | ||
722 | ||
723 | ||
724 | ||
725 | /************************************************ | |
726 | * Do a DNS lookup and handle CNAMES * | |
727 | ************************************************/ | |
728 | ||
729 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
730 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
731 | the DNS, but you are supposed to cope with them if you find them. | |
732 | ||
733 | The assumption is made that if the resolver gives back records of the | |
734 | requested type *and* a CNAME, we don't need to make another call to look up | |
735 | the CNAME. I can't see how it could return only some of the right records. If | |
736 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
737 | won't return any. | |
738 | ||
739 | If fully_qualified_name is not NULL, set it to point to the full name | |
740 | returned by the resolver, if this is different to what it is given, unless | |
741 | the returned name starts with "*" as some nameservers seem to be returning | |
742 | wildcards in this form. | |
743 | ||
744 | Arguments: | |
745 | dnsa pointer to dns_answer structure | |
746 | name domain name to look up | |
747 | type DNS record type (T_A, T_MX, etc) | |
748 | fully_qualified_name if not NULL, return the returned name here if its | |
749 | contents are different (i.e. it must be preset) | |
750 | ||
751 | Returns: DNS_SUCCEED successful lookup | |
752 | DNS_NOMATCH name not found | |
753 | DNS_NODATA no data found | |
754 | DNS_AGAIN soft failure, try again later | |
755 | DNS_FAIL DNS failure | |
756 | */ | |
757 | ||
758 | int | |
1dc92d5a JH |
759 | dns_lookup(dns_answer *dnsa, const uschar *name, int type, |
760 | uschar **fully_qualified_name) | |
059ec3d9 PH |
761 | { |
762 | int i; | |
1dc92d5a | 763 | const uschar *orig_name = name; |
c85b3043 | 764 | BOOL secure_so_far = TRUE; |
059ec3d9 PH |
765 | |
766 | /* Loop to follow CNAME chains so far, but no further... */ | |
767 | ||
768 | for (i = 0; i < 10; i++) | |
769 | { | |
770 | uschar data[256]; | |
771 | dns_record *rr, cname_rr, type_rr; | |
772 | dns_scan dnss; | |
773 | int datalen, rc; | |
774 | ||
775 | /* DNS lookup failures get passed straight back. */ | |
776 | ||
777 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
778 | ||
779 | /* We should have either records of the required type, or a CNAME record, | |
780 | or both. We need to know whether both exist for getting the fully qualified | |
781 | name, but avoid scanning more than necessary. Note that we must copy the | |
782 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
783 | area in the dnsa block. */ | |
784 | ||
785 | cname_rr.data = type_rr.data = NULL; | |
786 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
787 | rr != NULL; | |
788 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
789 | { | |
790 | if (rr->type == type) | |
791 | { | |
792 | if (type_rr.data == NULL) type_rr = *rr; | |
793 | if (cname_rr.data != NULL) break; | |
794 | } | |
795 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
796 | } | |
797 | ||
a2042e78 PH |
798 | /* For the first time round this loop, if a CNAME was found, take the fully |
799 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 800 | |
a2042e78 | 801 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 PH |
802 | { |
803 | if (cname_rr.data != NULL) | |
804 | { | |
805 | if (Ustrcmp(cname_rr.name, *fully_qualified_name) != 0 && | |
806 | cname_rr.name[0] != '*') | |
807 | *fully_qualified_name = string_copy_dnsdomain(cname_rr.name); | |
808 | } | |
809 | else if (type_rr.data != NULL) | |
810 | { | |
75e0e026 PH |
811 | if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 && |
812 | type_rr.name[0] != '*') | |
813 | *fully_qualified_name = string_copy_dnsdomain(type_rr.name); | |
059ec3d9 PH |
814 | } |
815 | } | |
816 | ||
817 | /* If any data records of the correct type were found, we are done. */ | |
818 | ||
c85b3043 JH |
819 | if (type_rr.data != NULL) |
820 | { | |
821 | if (!secure_so_far) /* mark insecure if any element of CNAME chain was */ | |
4a142059 | 822 | dns_set_insecure(dnsa); |
c85b3043 JH |
823 | return DNS_SUCCEED; |
824 | } | |
059ec3d9 PH |
825 | |
826 | /* If there are no data records, we need to re-scan the DNS using the | |
827 | domain given in the CNAME record, which should exist (otherwise we should | |
828 | have had a failure from dns_lookup). However code against the possibility of | |
829 | its not existing. */ | |
830 | ||
831 | if (cname_rr.data == NULL) return DNS_FAIL; | |
832 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
1dc92d5a | 833 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data)); |
059ec3d9 PH |
834 | if (datalen < 0) return DNS_FAIL; |
835 | name = data; | |
a2042e78 | 836 | |
c85b3043 JH |
837 | if (!dns_is_secure(dnsa)) |
838 | secure_so_far = FALSE; | |
839 | ||
a2042e78 | 840 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); |
059ec3d9 PH |
841 | } /* Loop back to do another lookup */ |
842 | ||
843 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
844 | right... */ | |
845 | ||
846 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
847 | return DNS_FAIL; | |
848 | } | |
849 | ||
850 | ||
851 | ||
33397d19 PH |
852 | |
853 | ||
854 | ||
855 | /************************************************ | |
856 | * Do a DNS lookup and handle virtual types * | |
857 | ************************************************/ | |
858 | ||
8e669ac1 PH |
859 | /* This function handles some invented "lookup types" that synthesize feature |
860 | not available in the basic types. The special types all have negative values. | |
33397d19 PH |
861 | Positive type values are passed straight on to dns_lookup(). |
862 | ||
863 | Arguments: | |
864 | dnsa pointer to dns_answer structure | |
865 | name domain name to look up | |
866 | type DNS record type (T_A, T_MX, etc or a "special") | |
867 | fully_qualified_name if not NULL, return the returned name here if its | |
868 | contents are different (i.e. it must be preset) | |
869 | ||
870 | Returns: DNS_SUCCEED successful lookup | |
871 | DNS_NOMATCH name not found | |
872 | DNS_NODATA no data found | |
873 | DNS_AGAIN soft failure, try again later | |
874 | DNS_FAIL DNS failure | |
875 | */ | |
876 | ||
877 | int | |
1dc92d5a | 878 | dns_special_lookup(dns_answer *dnsa, const uschar *name, int type, |
33397d19 PH |
879 | uschar **fully_qualified_name) |
880 | { | |
881 | if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name); | |
882 | ||
ea3bc19b PH |
883 | /* The "mx hosts only" type doesn't require any special action here */ |
884 | ||
885 | if (type == T_MXH) return dns_lookup(dnsa, name, T_MX, fully_qualified_name); | |
886 | ||
8e669ac1 | 887 | /* Find nameservers for the domain or the nearest enclosing zone, excluding the |
33397d19 PH |
888 | root servers. */ |
889 | ||
890 | if (type == T_ZNS) | |
891 | { | |
1dc92d5a | 892 | const uschar *d = name; |
33397d19 PH |
893 | while (d != 0) |
894 | { | |
895 | int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name); | |
896 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
897 | while (*d != 0 && *d != '.') d++; | |
8e669ac1 | 898 | if (*d++ == 0) break; |
33397d19 | 899 | } |
8e669ac1 PH |
900 | return DNS_NOMATCH; |
901 | } | |
33397d19 | 902 | |
e5a9dba6 PH |
903 | /* Try to look up the Client SMTP Authorization SRV record for the name. If |
904 | there isn't one, search from the top downwards for a CSA record in a parent | |
905 | domain, which might be making assertions about subdomains. If we find a record | |
906 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
907 | can tell whether to look at the explicit authorization field or the subdomain | |
908 | assertion field. */ | |
909 | ||
910 | if (type == T_CSA) | |
911 | { | |
912 | uschar *srvname, *namesuff, *tld, *p; | |
913 | int priority, weight, port; | |
914 | int limit, rc, i; | |
915 | BOOL ipv6; | |
916 | dns_record *rr; | |
917 | dns_scan dnss; | |
918 | ||
919 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
920 | ||
921 | srvname = string_sprintf("_client._smtp.%s", name); | |
922 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
923 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
924 | { | |
1dc92d5a | 925 | if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name); |
e5a9dba6 PH |
926 | return rc; |
927 | } | |
928 | ||
929 | /* Search for CSA subdomain assertion SRV records from the top downwards, | |
930 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
931 | We skip the top level domains to avoid loading their nameservers and because | |
932 | we know they'll never have CSA SRV records. */ | |
933 | ||
934 | namesuff = Ustrrchr(name, '.'); | |
935 | if (namesuff == NULL) return DNS_NOMATCH; | |
936 | tld = namesuff + 1; | |
937 | ipv6 = FALSE; | |
938 | limit = dns_csa_search_limit; | |
939 | ||
940 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
941 | ||
942 | if (strcmpic(namesuff, US".arpa") == 0) | |
943 | { | |
944 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
945 | { | |
946 | namesuff -= 8; | |
947 | tld = namesuff + 1; | |
948 | limit = 3; | |
949 | } | |
950 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
951 | { | |
952 | namesuff -= 4; | |
953 | tld = namesuff + 1; | |
954 | ipv6 = TRUE; | |
955 | limit = 3; | |
956 | } | |
957 | } | |
958 | ||
959 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); | |
960 | ||
961 | /* Do not perform the search if the top level or 2nd level domains do not | |
962 | exist. This is quite common, and when it occurs all the search queries would | |
963 | go to the root or TLD name servers, which is not friendly. So we check the | |
964 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
965 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
966 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
967 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
968 | ||
969 | if (rc == DNS_NOMATCH) | |
970 | { | |
971 | /* This is really gross. The successful return value from res_search() is | |
972 | the packet length, which is stored in dnsa->answerlen. If we get a | |
973 | negative DNS reply then res_search() returns -1, which causes the bounds | |
974 | checks for name decompression to fail when it is treated as a packet | |
975 | length, which in turn causes the authority search to fail. The correct | |
976 | packet length has been lost inside libresolv, so we have to guess a | |
977 | replacement value. (The only way to fix this properly would be to | |
978 | re-implement res_search() and res_query() so that they don't muddle their | |
979 | success and packet length return values.) For added safety we only reset | |
980 | the packet length if the packet header looks plausible. */ | |
981 | ||
982 | HEADER *h = (HEADER *)dnsa->answer; | |
983 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
984 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
985 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
986 | && ntohs(h->nscount) >= 1) | |
987 | dnsa->answerlen = MAXPACKET; | |
988 | ||
989 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
990 | rr != NULL; | |
991 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
992 | if (rr->type != T_SOA) continue; | |
993 | else if (strcmpic(rr->name, US"") == 0 || | |
994 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
995 | else break; | |
996 | } | |
997 | ||
998 | for (i = 0; i < limit; i++) | |
999 | { | |
1000 | if (ipv6) | |
1001 | { | |
1002 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
1003 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
1004 | namesuff -= 8; | |
1005 | if (namesuff <= name) return DNS_NOMATCH; | |
1006 | } | |
1007 | else | |
1008 | /* Find the start of the preceding domain name label. */ | |
1009 | do | |
1010 | if (--namesuff <= name) return DNS_NOMATCH; | |
1011 | while (*namesuff != '.'); | |
1012 | ||
1013 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
1014 | ||
1015 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
1016 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
1017 | if (rc == DNS_AGAIN) return rc; | |
1018 | if (rc != DNS_SUCCEED) continue; | |
1019 | ||
1020 | /* Check that the SRV record we have found is worth returning. We don't | |
1021 | just return the first one we find, because some lower level SRV record | |
1022 | might make stricter assertions than its parent domain. */ | |
1023 | ||
1024 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1025 | rr != NULL; | |
1026 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1027 | { | |
1028 | if (rr->type != T_SRV) continue; | |
1029 | ||
1030 | /* Extract the numerical SRV fields (p is incremented) */ | |
1031 | p = rr->data; | |
1032 | GETSHORT(priority, p); | |
4a142059 | 1033 | GETSHORT(weight, p); weight = weight; /* compiler quietening */ |
e5a9dba6 PH |
1034 | GETSHORT(port, p); |
1035 | ||
1036 | /* Check the CSA version number */ | |
1037 | if (priority != 1) continue; | |
1038 | ||
1039 | /* If it's making an interesting assertion, return this response. */ | |
1040 | if (port & 1) | |
1041 | { | |
1042 | *fully_qualified_name = namesuff + 1; | |
1043 | return DNS_SUCCEED; | |
1044 | } | |
1045 | } | |
1046 | } | |
1047 | return DNS_NOMATCH; | |
1048 | } | |
1049 | ||
33397d19 PH |
1050 | /* Control should never reach here */ |
1051 | ||
1052 | return DNS_FAIL; | |
1053 | } | |
1054 | ||
1055 | ||
1056 | ||
059ec3d9 PH |
1057 | /* Support for A6 records has been commented out since they were demoted to |
1058 | experimental status at IETF 51. */ | |
1059 | ||
1060 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1061 | ||
1062 | /************************************************* | |
1063 | * Search DNS block for prefix RRs * | |
1064 | *************************************************/ | |
1065 | ||
1066 | /* Called from dns_complete_a6() to search an additional section or a main | |
1067 | answer section for required prefix records to complete an IPv6 address obtained | |
1068 | from an A6 record. For each prefix record, a recursive call to dns_complete_a6 | |
1069 | is made, with a new copy of the address so far. | |
1070 | ||
1071 | Arguments: | |
1072 | dnsa the DNS answer block | |
1073 | which RESET_ADDITIONAL or RESET_ANSWERS | |
1074 | name name of prefix record | |
1075 | yptrptr pointer to the pointer that points to where to hang the next | |
1076 | dns_address structure | |
1077 | bits number of bits we have already got | |
1078 | bitvec the bits we have already got | |
1079 | ||
1080 | Returns: TRUE if any records were found | |
1081 | */ | |
1082 | ||
1083 | static BOOL | |
1084 | dns_find_prefix(dns_answer *dnsa, int which, uschar *name, dns_address | |
1085 | ***yptrptr, int bits, uschar *bitvec) | |
1086 | { | |
1087 | BOOL yield = FALSE; | |
1088 | dns_record *rr; | |
1089 | dns_scan dnss; | |
1090 | ||
1091 | for (rr = dns_next_rr(dnsa, &dnss, which); | |
1092 | rr != NULL; | |
1093 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1094 | { | |
1095 | uschar cbitvec[16]; | |
1096 | if (rr->type != T_A6 || strcmpic(rr->name, name) != 0) continue; | |
1097 | yield = TRUE; | |
1098 | memcpy(cbitvec, bitvec, sizeof(cbitvec)); | |
1099 | dns_complete_a6(yptrptr, dnsa, rr, bits, cbitvec); | |
1100 | } | |
1101 | ||
1102 | return yield; | |
1103 | } | |
1104 | ||
1105 | ||
1106 | ||
1107 | /************************************************* | |
1108 | * Follow chains of A6 records * | |
1109 | *************************************************/ | |
1110 | ||
1111 | /* A6 records may be incomplete, with pointers to other records containing more | |
1112 | bits of the address. There can be a tree structure, leading to a number of | |
1113 | addresses originating from a single initial A6 record. | |
1114 | ||
1115 | Arguments: | |
1116 | yptrptr pointer to the pointer that points to where to hang the next | |
1117 | dns_address structure | |
1118 | dnsa the current DNS answer block | |
1119 | rr the RR we have at present | |
1120 | bits number of bits we have already got | |
1121 | bitvec the bits we have already got | |
1122 | ||
1123 | Returns: nothing | |
1124 | */ | |
1125 | ||
1126 | static void | |
1127 | dns_complete_a6(dns_address ***yptrptr, dns_answer *dnsa, dns_record *rr, | |
1128 | int bits, uschar *bitvec) | |
1129 | { | |
1130 | static uschar bitmask[] = { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 }; | |
1131 | uschar *p = (uschar *)(rr->data); | |
1132 | int prefix_len, suffix_len; | |
1133 | int i, j, k; | |
1134 | uschar *chainptr; | |
1135 | uschar chain[264]; | |
1136 | dns_answer cdnsa; | |
1137 | ||
1138 | /* The prefix length is the first byte. It defines the prefix which is missing | |
1139 | from the data in this record as a number of bits. Zero means this is the end of | |
1140 | a chain. The suffix is the data in this record; only sufficient bytes to hold | |
1141 | it are supplied. There may be zero bytes. We have to ignore trailing bits that | |
1142 | we have already obtained from earlier RRs in the chain. */ | |
1143 | ||
1144 | prefix_len = *p++; /* bits */ | |
1145 | suffix_len = (128 - prefix_len + 7)/8; /* bytes */ | |
1146 | ||
1147 | /* If the prefix in this record is greater than the prefix in the previous | |
1148 | record in the chain, we have to ignore the record (RFC 2874). */ | |
1149 | ||
1150 | if (prefix_len > 128 - bits) return; | |
1151 | ||
1152 | /* In this little loop, the number of bits up to and including the current byte | |
1153 | is held in k. If we have none of the bits in this byte, we can just or it into | |
1154 | the current data. If we have all of the bits in this byte, we skip it. | |
1155 | Otherwise, some masking has to be done. */ | |
1156 | ||
1157 | for (i = suffix_len - 1, j = 15, k = 8; i >= 0; i--) | |
1158 | { | |
1159 | int required = k - bits; | |
1160 | if (required >= 8) bitvec[j] |= p[i]; | |
1161 | else if (required > 0) bitvec[j] |= p[i] & bitmask[required]; | |
1162 | j--; /* I tried putting these in the "for" statement, but gcc muttered */ | |
1163 | k += 8; /* about computed values not being used. */ | |
1164 | } | |
1165 | ||
1166 | /* If the prefix_length is zero, we are at the end of a chain. Build a | |
1167 | dns_address item with the current data, hang it onto the end of the chain, | |
1168 | adjust the hanging pointer, and we are done. */ | |
1169 | ||
1170 | if (prefix_len == 0) | |
1171 | { | |
1172 | dns_address *new = store_get(sizeof(dns_address) + 50); | |
1173 | inet_ntop(AF_INET6, bitvec, CS new->address, 50); | |
1174 | new->next = NULL; | |
1175 | **yptrptr = new; | |
1176 | *yptrptr = &(new->next); | |
1177 | return; | |
1178 | } | |
1179 | ||
1180 | /* Prefix length is not zero. Reset the number of bits that we have collected | |
1181 | so far, and extract the chain name. */ | |
1182 | ||
1183 | bits = 128 - prefix_len; | |
1184 | p += suffix_len; | |
1185 | ||
1186 | chainptr = chain; | |
1187 | while ((i = *p++) != 0) | |
1188 | { | |
1189 | if (chainptr != chain) *chainptr++ = '.'; | |
1190 | memcpy(chainptr, p, i); | |
1191 | chainptr += i; | |
1192 | p += i; | |
1193 | } | |
1194 | *chainptr = 0; | |
1195 | chainptr = chain; | |
1196 | ||
1197 | /* Now scan the current DNS response record to see if the additional section | |
1198 | contains the records we want. This processing can be cut out for testing | |
1199 | purposes. */ | |
1200 | ||
1201 | if (dns_find_prefix(dnsa, RESET_ADDITIONAL, chainptr, yptrptr, bits, bitvec)) | |
1202 | return; | |
1203 | ||
1204 | /* No chain records were found in the current DNS response block. Do a new DNS | |
1205 | lookup to try to find these records. This opens up the possibility of DNS | |
1206 | failures. We ignore them at this point; if all branches of the tree fail, there | |
1207 | will be no addresses at the end. */ | |
1208 | ||
1209 | if (dns_lookup(&cdnsa, chainptr, T_A6, NULL) == DNS_SUCCEED) | |
1210 | (void)dns_find_prefix(&cdnsa, RESET_ANSWERS, chainptr, yptrptr, bits, bitvec); | |
1211 | } | |
1212 | #endif /* HAVE_IPV6 && defined(SUPPORT_A6) */ | |
1213 | ||
1214 | ||
1215 | ||
1216 | ||
1217 | /************************************************* | |
1218 | * Get address(es) from DNS record * | |
1219 | *************************************************/ | |
1220 | ||
1221 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
1222 | supported) for an IPv6 address. In the A6 case, there may be several addresses, | |
1223 | generated by following chains. A recursive function does all the hard work. A6 | |
1224 | records now look like passing into history, so the code is only included when | |
1225 | explicitly asked for. | |
1226 | ||
1227 | Argument: | |
1228 | dnsa the DNS answer block | |
1229 | rr the RR | |
1230 | ||
1231 | Returns: pointer a chain of dns_address items | |
1232 | */ | |
1233 | ||
1234 | dns_address * | |
1235 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1236 | { | |
1237 | dns_address *yield = NULL; | |
1238 | ||
1239 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1240 | dns_address **yieldptr = &yield; | |
1241 | uschar bitvec[16]; | |
1242 | #else | |
1243 | dnsa = dnsa; /* Stop picky compilers warning */ | |
1244 | #endif | |
1245 | ||
1246 | if (rr->type == T_A) | |
1247 | { | |
1248 | uschar *p = (uschar *)(rr->data); | |
1249 | yield = store_get(sizeof(dns_address) + 20); | |
1250 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1251 | yield->next = NULL; | |
1252 | } | |
1253 | ||
1254 | #if HAVE_IPV6 | |
1255 | ||
1256 | #ifdef SUPPORT_A6 | |
1257 | else if (rr->type == T_A6) | |
1258 | { | |
1259 | memset(bitvec, 0, sizeof(bitvec)); | |
1260 | dns_complete_a6(&yieldptr, dnsa, rr, 0, bitvec); | |
1261 | } | |
1262 | #endif /* SUPPORT_A6 */ | |
1263 | ||
1264 | else | |
1265 | { | |
1266 | yield = store_get(sizeof(dns_address) + 50); | |
1267 | inet_ntop(AF_INET6, (uschar *)(rr->data), CS yield->address, 50); | |
1268 | yield->next = NULL; | |
1269 | } | |
1270 | #endif /* HAVE_IPV6 */ | |
1271 | ||
1272 | return yield; | |
1273 | } | |
1274 | ||
8c51eead JH |
1275 | /* vi: aw ai sw=2 |
1276 | */ | |
059ec3d9 | 1277 | /* End of dns.c */ |