Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
c4ceed07 | 5 | /* Copyright (c) University of Cambridge 1995 - 2012 */ |
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 | 203 | |
1f4a55da PP |
204 | #ifndef DISABLE_DNSSEC |
205 | # ifdef RES_USE_DNSSEC | |
206 | # ifndef RES_USE_EDNS0 | |
207 | # error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ... | |
208 | # endif | |
0fbd9bff | 209 | if (dns_dnssec_ok >= 0) |
1f4a55da | 210 | { |
0fbd9bff | 211 | if (dns_use_edns0 == 0 && dns_dnssec_ok != 0) |
1f4a55da PP |
212 | { |
213 | DEBUG(D_resolver) | |
0fbd9bff | 214 | debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n"); |
1f4a55da PP |
215 | } |
216 | else | |
217 | { | |
0fbd9bff | 218 | if (dns_dnssec_ok) |
1f4a55da PP |
219 | resp->options |= RES_USE_DNSSEC; |
220 | else | |
221 | resp->options &= ~RES_USE_DNSSEC; | |
222 | DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n", | |
0fbd9bff | 223 | dns_dnssec_ok ? "on" : "off"); |
1f4a55da PP |
224 | } |
225 | } | |
226 | # else | |
0fbd9bff | 227 | if (dns_dnssec_ok >= 0) |
1f4a55da PP |
228 | DEBUG(D_resolver) |
229 | debug_printf("Unable to %sset DNSSEC without resolver support.\n", | |
0fbd9bff | 230 | dns_dnssec_ok ? "" : "un"); |
1f4a55da PP |
231 | # endif |
232 | #endif /* DISABLE_DNSSEC */ | |
233 | ||
5bfb4cdf | 234 | os_put_dns_resolver_res(resp); |
059ec3d9 PH |
235 | } |
236 | ||
237 | ||
238 | ||
239 | /************************************************* | |
240 | * Build key name for PTR records * | |
241 | *************************************************/ | |
242 | ||
243 | /* This function inverts an IP address and adds the relevant domain, to produce | |
244 | a name that can be used to look up PTR records. | |
245 | ||
246 | Arguments: | |
247 | string the IP address as a string | |
248 | buffer a suitable buffer, long enough to hold the result | |
249 | ||
250 | Returns: nothing | |
251 | */ | |
252 | ||
253 | void | |
254 | dns_build_reverse(uschar *string, uschar *buffer) | |
255 | { | |
256 | uschar *p = string + Ustrlen(string); | |
257 | uschar *pp = buffer; | |
258 | ||
259 | /* Handle IPv4 address */ | |
260 | ||
261 | #if HAVE_IPV6 | |
262 | if (Ustrchr(string, ':') == NULL) | |
263 | #endif | |
264 | { | |
265 | int i; | |
266 | for (i = 0; i < 4; i++) | |
267 | { | |
268 | uschar *ppp = p; | |
269 | while (ppp > string && ppp[-1] != '.') ppp--; | |
270 | Ustrncpy(pp, ppp, p - ppp); | |
271 | pp += p - ppp; | |
272 | *pp++ = '.'; | |
273 | p = ppp - 1; | |
274 | } | |
275 | Ustrcpy(pp, "in-addr.arpa"); | |
276 | } | |
277 | ||
278 | /* Handle IPv6 address; convert to binary so as to fill out any | |
279 | abbreviation in the textual form. */ | |
280 | ||
281 | #if HAVE_IPV6 | |
282 | else | |
283 | { | |
284 | int i; | |
285 | int v6[4]; | |
286 | (void)host_aton(string, v6); | |
287 | ||
288 | /* The original specification for IPv6 reverse lookup was to invert each | |
289 | nibble, and look in the ip6.int domain. The domain was subsequently | |
290 | changed to ip6.arpa. */ | |
291 | ||
292 | for (i = 3; i >= 0; i--) | |
293 | { | |
294 | int j; | |
295 | for (j = 0; j < 32; j += 4) | |
296 | { | |
297 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
298 | pp += 2; | |
299 | } | |
300 | } | |
301 | Ustrcpy(pp, "ip6.arpa."); | |
302 | ||
303 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
304 | with A6 records. However, it fell out of favour when they did. The | |
305 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
306 | to make this code do that, but I could not make it work on Solaris 8. The | |
307 | resolver seems to lose the initial backslash somehow. However, now that | |
308 | this style of reverse lookup has been dropped, it doesn't matter. These | |
309 | lines are left here purely for historical interest. */ | |
310 | ||
311 | /************************************************** | |
312 | Ustrcpy(pp, "\\[x"); | |
313 | pp += 3; | |
314 | ||
315 | for (i = 0; i < 4; i++) | |
316 | { | |
317 | sprintf(pp, "%08X", v6[i]); | |
318 | pp += 8; | |
319 | } | |
320 | Ustrcpy(pp, "].ip6.arpa."); | |
321 | **************************************************/ | |
322 | ||
323 | } | |
324 | #endif | |
325 | } | |
326 | ||
327 | ||
328 | ||
329 | ||
330 | /************************************************* | |
331 | * Get next DNS record from answer block * | |
332 | *************************************************/ | |
333 | ||
334 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
335 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
336 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
337 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
338 | |
339 | Arguments: | |
340 | dnsa pointer to dns answer block | |
341 | dnss pointer to dns scan block | |
342 | reset option specifing what portion to scan, as described above | |
343 | ||
344 | Returns: next dns record, or NULL when no more | |
345 | */ | |
346 | ||
347 | dns_record * | |
348 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
349 | { | |
350 | HEADER *h = (HEADER *)dnsa->answer; | |
351 | int namelen; | |
352 | ||
353 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
354 | ||
355 | if (reset != RESET_NEXT) | |
356 | { | |
357 | dnss->rrcount = ntohs(h->qdcount); | |
358 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
359 | ||
360 | /* Skip over questions; failure to expand the name just gives up */ | |
361 | ||
362 | while (dnss->rrcount-- > 0) | |
363 | { | |
364 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
365 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
366 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
367 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
368 | } | |
369 | ||
370 | /* Get the number of answer records. */ | |
371 | ||
372 | dnss->rrcount = ntohs(h->ancount); | |
373 | ||
e5a9dba6 PH |
374 | /* Skip over answers if we want to look at the authority section. Also skip |
375 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
376 | records. */ |
377 | ||
e5a9dba6 PH |
378 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
379 | ||
380 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 381 | { |
059ec3d9 PH |
382 | while (dnss->rrcount-- > 0) |
383 | { | |
384 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
385 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
386 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
387 | dnss->aptr += namelen + 8; /* skip name, type, class & TTL */ | |
388 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
389 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
390 | } | |
e5a9dba6 PH |
391 | dnss->rrcount = (reset == RESET_AUTHORITY) |
392 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
393 | } |
394 | } | |
395 | ||
059ec3d9 PH |
396 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
397 | contains the number of RR records left. */ | |
398 | ||
399 | if (dnss->rrcount-- <= 0) return NULL; | |
400 | ||
401 | /* If expanding the RR domain name fails, behave as if no more records | |
402 | (something safe). */ | |
403 | ||
404 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
405 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
406 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
407 | ||
408 | /* Move the pointer past the name and fill in the rest of the data structure | |
409 | from the following bytes. */ | |
410 | ||
411 | dnss->aptr += namelen; | |
412 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
413 | dnss->aptr += 6; /* Don't want class or TTL */ | |
414 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
415 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
416 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
417 | ||
418 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
419 | for convenience so that the scans can use nice-looking for loops. */ | |
420 | ||
421 | return &(dnss->srr); | |
422 | } | |
423 | ||
424 | ||
425 | ||
426 | ||
1f4a55da PP |
427 | /************************************************* |
428 | * Return whether AD bit set in DNS result * | |
429 | *************************************************/ | |
430 | ||
431 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
432 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
433 | (AD = Authentic Data) | |
434 | ||
435 | Argument: pointer to dns answer block | |
436 | Returns: bool indicating presence of AD bit | |
437 | */ | |
438 | ||
439 | BOOL | |
440 | dns_is_secure(dns_answer *dnsa) | |
441 | { | |
442 | #ifdef DISABLE_DNSSEC | |
443 | DEBUG(D_dns) | |
444 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
445 | return FALSE; | |
446 | #else | |
447 | HEADER *h = (HEADER *)dnsa->answer; | |
448 | return h->ad ? TRUE : FALSE; | |
449 | #endif | |
450 | } | |
451 | ||
452 | ||
453 | ||
454 | ||
059ec3d9 PH |
455 | /************************************************* |
456 | * Turn DNS type into text * | |
457 | *************************************************/ | |
458 | ||
885ccd3e PH |
459 | /* Turn the coded record type into a string for printing. All those that Exim |
460 | uses should be included here. | |
059ec3d9 PH |
461 | |
462 | Argument: record type | |
463 | Returns: pointer to string | |
464 | */ | |
465 | ||
466 | uschar * | |
467 | dns_text_type(int t) | |
468 | { | |
469 | switch(t) | |
470 | { | |
33397d19 PH |
471 | case T_A: return US"A"; |
472 | case T_MX: return US"MX"; | |
473 | case T_AAAA: return US"AAAA"; | |
474 | case T_A6: return US"A6"; | |
475 | case T_TXT: return US"TXT"; | |
eae0036b | 476 | case T_SPF: return US"SPF"; |
33397d19 | 477 | case T_PTR: return US"PTR"; |
885ccd3e | 478 | case T_SOA: return US"SOA"; |
33397d19 PH |
479 | case T_SRV: return US"SRV"; |
480 | case T_NS: return US"NS"; | |
8e669ac1 | 481 | case T_CNAME: return US"CNAME"; |
33397d19 | 482 | default: return US"?"; |
059ec3d9 PH |
483 | } |
484 | } | |
485 | ||
486 | ||
487 | ||
488 | /************************************************* | |
489 | * Cache a failed DNS lookup result * | |
490 | *************************************************/ | |
491 | ||
492 | /* We cache failed lookup results so as not to experience timeouts many | |
493 | times for the same domain. We need to retain the resolver options because they | |
494 | may change. For successful lookups, we rely on resolver and/or name server | |
495 | caching. | |
496 | ||
497 | Arguments: | |
498 | name the domain name | |
499 | type the lookup type | |
500 | rc the return code | |
501 | ||
502 | Returns: the return code | |
503 | */ | |
504 | ||
505 | static int | |
506 | dns_return(uschar *name, int type, int rc) | |
507 | { | |
5bfb4cdf | 508 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
509 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); |
510 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 511 | resp->options); |
059ec3d9 PH |
512 | node->data.val = rc; |
513 | (void)tree_insertnode(&tree_dns_fails, node); | |
514 | return rc; | |
515 | } | |
516 | ||
517 | ||
518 | ||
519 | /************************************************* | |
520 | * Do basic DNS lookup * | |
521 | *************************************************/ | |
522 | ||
523 | /* Call the resolver to look up the given domain name, using the given type, | |
524 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
525 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
526 | up nameservers that produce this error continually, so there is the option of | |
527 | providing a list of domains for which this is treated as a non-existent | |
528 | host. | |
529 | ||
530 | Arguments: | |
531 | dnsa pointer to dns_answer structure | |
532 | name name to look up | |
533 | type type of DNS record required (T_A, T_MX, etc) | |
534 | ||
535 | Returns: DNS_SUCCEED successful lookup | |
536 | DNS_NOMATCH name not found (NXDOMAIN) | |
537 | or name contains illegal characters (if checking) | |
30e18802 | 538 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
539 | DNS_NODATA domain exists, but no data for this type (NODATA) |
540 | DNS_AGAIN soft failure, try again later | |
541 | DNS_FAIL DNS failure | |
542 | */ | |
543 | ||
544 | int | |
545 | dns_basic_lookup(dns_answer *dnsa, uschar *name, int type) | |
546 | { | |
547 | #ifndef STAND_ALONE | |
7156b1ef | 548 | int rc = -1; |
059ec3d9 PH |
549 | uschar *save; |
550 | #endif | |
5bfb4cdf | 551 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
552 | |
553 | tree_node *previous; | |
554 | uschar node_name[290]; | |
555 | ||
556 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
557 | a timeout on one domain doesn't happen time and time again for messages that | |
558 | have many addresses in the same domain. We rely on the resolver and name server | |
559 | caching for successful lookups. */ | |
560 | ||
561 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 562 | resp->options); |
059ec3d9 PH |
563 | previous = tree_search(tree_dns_fails, node_name); |
564 | if (previous != NULL) | |
565 | { | |
566 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
567 | name, dns_text_type(type), | |
568 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
569 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
570 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
571 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
572 | return previous->data.val; | |
573 | } | |
574 | ||
059ec3d9 PH |
575 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
576 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
577 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
578 | domains cannot be in the DNS. The check is now done by a regular expression; | |
579 | give it space for substring storage to save it having to get its own if the | |
580 | regex has substrings that are used - the default uses a conditional. | |
581 | ||
582 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
583 | lookup, which constructs the names itself, so they should be OK. Besides, | |
584 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
585 | more.) | |
586 | ||
587 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
588 | ||
589 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
590 | ||
482d1455 | 591 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 PH |
592 | { |
593 | uschar *checkname = name; | |
594 | int ovector[3*(EXPAND_MAXN+1)]; | |
595 | ||
596 | if (regex_check_dns_names == NULL) | |
597 | regex_check_dns_names = | |
598 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
599 | ||
600 | /* For an SRV lookup, skip over the first two components (the service and | |
601 | protocol names, which both start with an underscore). */ | |
602 | ||
603 | if (type == T_SRV) | |
604 | { | |
605 | while (*checkname++ != '.'); | |
606 | while (*checkname++ != '.'); | |
607 | } | |
608 | ||
609 | if (pcre_exec(regex_check_dns_names, NULL, CS checkname, Ustrlen(checkname), | |
610 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) | |
611 | { | |
612 | DEBUG(D_dns) | |
613 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
614 | dns_text_type(type)); | |
615 | host_find_failed_syntax = TRUE; | |
616 | return DNS_NOMATCH; | |
617 | } | |
618 | } | |
619 | ||
620 | #endif /* STAND_ALONE */ | |
621 | ||
622 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
623 | number of bytes the message would need, so we need to check for this case. The |
624 | effect is to truncate overlong data. | |
625 | ||
30e18802 PH |
626 | On some systems, res_search() will recognize "A-for-A" queries and return |
627 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
628 | nameservers are also believed to do this. It is, of course, contrary to the | |
629 | specification of the DNS, so we lock it out. */ | |
630 | ||
631 | if (( | |
632 | #ifdef SUPPORT_A6 | |
633 | type == T_A6 || | |
634 | #endif | |
635 | type == T_A || type == T_AAAA) && | |
636 | string_is_ip_address(name, NULL) != 0) | |
637 | return DNS_NOMATCH; | |
638 | ||
639 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
640 | (res_search), we call fakens_search(), which recognizes certain special |
641 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
642 | ||
643 | if (running_in_test_harness) | |
644 | dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET); | |
645 | else | |
646 | dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET); | |
059ec3d9 | 647 | |
80a47a2c TK |
648 | if (dnsa->answerlen > MAXPACKET) |
649 | { | |
650 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n", | |
651 | name, dns_text_type(type), dnsa->answerlen, MAXPACKET); | |
652 | dnsa->answerlen = MAXPACKET; | |
653 | } | |
059ec3d9 PH |
654 | |
655 | if (dnsa->answerlen < 0) switch (h_errno) | |
656 | { | |
657 | case HOST_NOT_FOUND: | |
658 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
659 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
660 | return dns_return(name, type, DNS_NOMATCH); | |
661 | ||
662 | case TRY_AGAIN: | |
663 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
664 | name, dns_text_type(type)); | |
665 | ||
666 | /* Cut this out for various test programs */ | |
667 | #ifndef STAND_ALONE | |
668 | save = deliver_domain; | |
669 | deliver_domain = name; /* set $domain */ | |
670 | rc = match_isinlist(name, &dns_again_means_nonexist, 0, NULL, NULL, | |
671 | MCL_DOMAIN, TRUE, NULL); | |
672 | deliver_domain = save; | |
673 | if (rc != OK) | |
674 | { | |
675 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
676 | return dns_return(name, type, DNS_AGAIN); | |
677 | } | |
678 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
679 | "DNS_NOMATCH\n", name); | |
680 | return dns_return(name, type, DNS_NOMATCH); | |
681 | ||
682 | #else /* For stand-alone tests */ | |
683 | return dns_return(name, type, DNS_AGAIN); | |
684 | #endif | |
685 | ||
686 | case NO_RECOVERY: | |
687 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
688 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
689 | return dns_return(name, type, DNS_FAIL); | |
690 | ||
691 | case NO_DATA: | |
692 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
693 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
694 | return dns_return(name, type, DNS_NODATA); | |
695 | ||
696 | default: | |
697 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
698 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
699 | return dns_return(name, type, DNS_FAIL); | |
700 | } | |
701 | ||
702 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
703 | name, dns_text_type(type)); | |
704 | ||
705 | return DNS_SUCCEED; | |
706 | } | |
707 | ||
708 | ||
709 | ||
710 | ||
711 | /************************************************ | |
712 | * Do a DNS lookup and handle CNAMES * | |
713 | ************************************************/ | |
714 | ||
715 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
716 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
717 | the DNS, but you are supposed to cope with them if you find them. | |
718 | ||
719 | The assumption is made that if the resolver gives back records of the | |
720 | requested type *and* a CNAME, we don't need to make another call to look up | |
721 | the CNAME. I can't see how it could return only some of the right records. If | |
722 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
723 | won't return any. | |
724 | ||
725 | If fully_qualified_name is not NULL, set it to point to the full name | |
726 | returned by the resolver, if this is different to what it is given, unless | |
727 | the returned name starts with "*" as some nameservers seem to be returning | |
728 | wildcards in this form. | |
729 | ||
730 | Arguments: | |
731 | dnsa pointer to dns_answer structure | |
732 | name domain name to look up | |
733 | type DNS record type (T_A, T_MX, etc) | |
734 | fully_qualified_name if not NULL, return the returned name here if its | |
735 | contents are different (i.e. it must be preset) | |
736 | ||
737 | Returns: DNS_SUCCEED successful lookup | |
738 | DNS_NOMATCH name not found | |
739 | DNS_NODATA no data found | |
740 | DNS_AGAIN soft failure, try again later | |
741 | DNS_FAIL DNS failure | |
742 | */ | |
743 | ||
744 | int | |
745 | dns_lookup(dns_answer *dnsa, uschar *name, int type, uschar **fully_qualified_name) | |
746 | { | |
747 | int i; | |
748 | uschar *orig_name = name; | |
749 | ||
750 | /* Loop to follow CNAME chains so far, but no further... */ | |
751 | ||
752 | for (i = 0; i < 10; i++) | |
753 | { | |
754 | uschar data[256]; | |
755 | dns_record *rr, cname_rr, type_rr; | |
756 | dns_scan dnss; | |
757 | int datalen, rc; | |
758 | ||
759 | /* DNS lookup failures get passed straight back. */ | |
760 | ||
761 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
762 | ||
763 | /* We should have either records of the required type, or a CNAME record, | |
764 | or both. We need to know whether both exist for getting the fully qualified | |
765 | name, but avoid scanning more than necessary. Note that we must copy the | |
766 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
767 | area in the dnsa block. */ | |
768 | ||
769 | cname_rr.data = type_rr.data = NULL; | |
770 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
771 | rr != NULL; | |
772 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
773 | { | |
774 | if (rr->type == type) | |
775 | { | |
776 | if (type_rr.data == NULL) type_rr = *rr; | |
777 | if (cname_rr.data != NULL) break; | |
778 | } | |
779 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
780 | } | |
781 | ||
a2042e78 PH |
782 | /* For the first time round this loop, if a CNAME was found, take the fully |
783 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 784 | |
a2042e78 | 785 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 PH |
786 | { |
787 | if (cname_rr.data != NULL) | |
788 | { | |
789 | if (Ustrcmp(cname_rr.name, *fully_qualified_name) != 0 && | |
790 | cname_rr.name[0] != '*') | |
791 | *fully_qualified_name = string_copy_dnsdomain(cname_rr.name); | |
792 | } | |
793 | else if (type_rr.data != NULL) | |
794 | { | |
75e0e026 PH |
795 | if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 && |
796 | type_rr.name[0] != '*') | |
797 | *fully_qualified_name = string_copy_dnsdomain(type_rr.name); | |
059ec3d9 PH |
798 | } |
799 | } | |
800 | ||
801 | /* If any data records of the correct type were found, we are done. */ | |
802 | ||
803 | if (type_rr.data != NULL) return DNS_SUCCEED; | |
804 | ||
805 | /* If there are no data records, we need to re-scan the DNS using the | |
806 | domain given in the CNAME record, which should exist (otherwise we should | |
807 | have had a failure from dns_lookup). However code against the possibility of | |
808 | its not existing. */ | |
809 | ||
810 | if (cname_rr.data == NULL) return DNS_FAIL; | |
811 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
812 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256); | |
813 | if (datalen < 0) return DNS_FAIL; | |
814 | name = data; | |
a2042e78 PH |
815 | |
816 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); | |
059ec3d9 PH |
817 | } /* Loop back to do another lookup */ |
818 | ||
819 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
820 | right... */ | |
821 | ||
822 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
823 | return DNS_FAIL; | |
824 | } | |
825 | ||
826 | ||
827 | ||
33397d19 PH |
828 | |
829 | ||
830 | ||
831 | /************************************************ | |
832 | * Do a DNS lookup and handle virtual types * | |
833 | ************************************************/ | |
834 | ||
8e669ac1 PH |
835 | /* This function handles some invented "lookup types" that synthesize feature |
836 | not available in the basic types. The special types all have negative values. | |
33397d19 PH |
837 | Positive type values are passed straight on to dns_lookup(). |
838 | ||
839 | Arguments: | |
840 | dnsa pointer to dns_answer structure | |
841 | name domain name to look up | |
842 | type DNS record type (T_A, T_MX, etc or a "special") | |
843 | fully_qualified_name if not NULL, return the returned name here if its | |
844 | contents are different (i.e. it must be preset) | |
845 | ||
846 | Returns: DNS_SUCCEED successful lookup | |
847 | DNS_NOMATCH name not found | |
848 | DNS_NODATA no data found | |
849 | DNS_AGAIN soft failure, try again later | |
850 | DNS_FAIL DNS failure | |
851 | */ | |
852 | ||
853 | int | |
8e669ac1 | 854 | dns_special_lookup(dns_answer *dnsa, uschar *name, int type, |
33397d19 PH |
855 | uschar **fully_qualified_name) |
856 | { | |
857 | if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name); | |
858 | ||
ea3bc19b PH |
859 | /* The "mx hosts only" type doesn't require any special action here */ |
860 | ||
861 | if (type == T_MXH) return dns_lookup(dnsa, name, T_MX, fully_qualified_name); | |
862 | ||
8e669ac1 | 863 | /* Find nameservers for the domain or the nearest enclosing zone, excluding the |
33397d19 PH |
864 | root servers. */ |
865 | ||
866 | if (type == T_ZNS) | |
867 | { | |
868 | uschar *d = name; | |
869 | while (d != 0) | |
870 | { | |
871 | int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name); | |
872 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
873 | while (*d != 0 && *d != '.') d++; | |
8e669ac1 | 874 | if (*d++ == 0) break; |
33397d19 | 875 | } |
8e669ac1 PH |
876 | return DNS_NOMATCH; |
877 | } | |
33397d19 | 878 | |
e5a9dba6 PH |
879 | /* Try to look up the Client SMTP Authorization SRV record for the name. If |
880 | there isn't one, search from the top downwards for a CSA record in a parent | |
881 | domain, which might be making assertions about subdomains. If we find a record | |
882 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
883 | can tell whether to look at the explicit authorization field or the subdomain | |
884 | assertion field. */ | |
885 | ||
886 | if (type == T_CSA) | |
887 | { | |
888 | uschar *srvname, *namesuff, *tld, *p; | |
889 | int priority, weight, port; | |
890 | int limit, rc, i; | |
891 | BOOL ipv6; | |
892 | dns_record *rr; | |
893 | dns_scan dnss; | |
894 | ||
895 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
896 | ||
897 | srvname = string_sprintf("_client._smtp.%s", name); | |
898 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
899 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
900 | { | |
901 | if (rc == DNS_SUCCEED) *fully_qualified_name = name; | |
902 | return rc; | |
903 | } | |
904 | ||
905 | /* Search for CSA subdomain assertion SRV records from the top downwards, | |
906 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
907 | We skip the top level domains to avoid loading their nameservers and because | |
908 | we know they'll never have CSA SRV records. */ | |
909 | ||
910 | namesuff = Ustrrchr(name, '.'); | |
911 | if (namesuff == NULL) return DNS_NOMATCH; | |
912 | tld = namesuff + 1; | |
913 | ipv6 = FALSE; | |
914 | limit = dns_csa_search_limit; | |
915 | ||
916 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
917 | ||
918 | if (strcmpic(namesuff, US".arpa") == 0) | |
919 | { | |
920 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
921 | { | |
922 | namesuff -= 8; | |
923 | tld = namesuff + 1; | |
924 | limit = 3; | |
925 | } | |
926 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
927 | { | |
928 | namesuff -= 4; | |
929 | tld = namesuff + 1; | |
930 | ipv6 = TRUE; | |
931 | limit = 3; | |
932 | } | |
933 | } | |
934 | ||
935 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); | |
936 | ||
937 | /* Do not perform the search if the top level or 2nd level domains do not | |
938 | exist. This is quite common, and when it occurs all the search queries would | |
939 | go to the root or TLD name servers, which is not friendly. So we check the | |
940 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
941 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
942 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
943 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
944 | ||
945 | if (rc == DNS_NOMATCH) | |
946 | { | |
947 | /* This is really gross. The successful return value from res_search() is | |
948 | the packet length, which is stored in dnsa->answerlen. If we get a | |
949 | negative DNS reply then res_search() returns -1, which causes the bounds | |
950 | checks for name decompression to fail when it is treated as a packet | |
951 | length, which in turn causes the authority search to fail. The correct | |
952 | packet length has been lost inside libresolv, so we have to guess a | |
953 | replacement value. (The only way to fix this properly would be to | |
954 | re-implement res_search() and res_query() so that they don't muddle their | |
955 | success and packet length return values.) For added safety we only reset | |
956 | the packet length if the packet header looks plausible. */ | |
957 | ||
958 | HEADER *h = (HEADER *)dnsa->answer; | |
959 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
960 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
961 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
962 | && ntohs(h->nscount) >= 1) | |
963 | dnsa->answerlen = MAXPACKET; | |
964 | ||
965 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
966 | rr != NULL; | |
967 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
968 | if (rr->type != T_SOA) continue; | |
969 | else if (strcmpic(rr->name, US"") == 0 || | |
970 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
971 | else break; | |
972 | } | |
973 | ||
974 | for (i = 0; i < limit; i++) | |
975 | { | |
976 | if (ipv6) | |
977 | { | |
978 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
979 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
980 | namesuff -= 8; | |
981 | if (namesuff <= name) return DNS_NOMATCH; | |
982 | } | |
983 | else | |
984 | /* Find the start of the preceding domain name label. */ | |
985 | do | |
986 | if (--namesuff <= name) return DNS_NOMATCH; | |
987 | while (*namesuff != '.'); | |
988 | ||
989 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
990 | ||
991 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
992 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
993 | if (rc == DNS_AGAIN) return rc; | |
994 | if (rc != DNS_SUCCEED) continue; | |
995 | ||
996 | /* Check that the SRV record we have found is worth returning. We don't | |
997 | just return the first one we find, because some lower level SRV record | |
998 | might make stricter assertions than its parent domain. */ | |
999 | ||
1000 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1001 | rr != NULL; | |
1002 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1003 | { | |
1004 | if (rr->type != T_SRV) continue; | |
1005 | ||
1006 | /* Extract the numerical SRV fields (p is incremented) */ | |
1007 | p = rr->data; | |
1008 | GETSHORT(priority, p); | |
1009 | GETSHORT(weight, p); | |
1010 | GETSHORT(port, p); | |
1011 | ||
1012 | /* Check the CSA version number */ | |
1013 | if (priority != 1) continue; | |
1014 | ||
1015 | /* If it's making an interesting assertion, return this response. */ | |
1016 | if (port & 1) | |
1017 | { | |
1018 | *fully_qualified_name = namesuff + 1; | |
1019 | return DNS_SUCCEED; | |
1020 | } | |
1021 | } | |
1022 | } | |
1023 | return DNS_NOMATCH; | |
1024 | } | |
1025 | ||
33397d19 PH |
1026 | /* Control should never reach here */ |
1027 | ||
1028 | return DNS_FAIL; | |
1029 | } | |
1030 | ||
1031 | ||
1032 | ||
059ec3d9 PH |
1033 | /* Support for A6 records has been commented out since they were demoted to |
1034 | experimental status at IETF 51. */ | |
1035 | ||
1036 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1037 | ||
1038 | /************************************************* | |
1039 | * Search DNS block for prefix RRs * | |
1040 | *************************************************/ | |
1041 | ||
1042 | /* Called from dns_complete_a6() to search an additional section or a main | |
1043 | answer section for required prefix records to complete an IPv6 address obtained | |
1044 | from an A6 record. For each prefix record, a recursive call to dns_complete_a6 | |
1045 | is made, with a new copy of the address so far. | |
1046 | ||
1047 | Arguments: | |
1048 | dnsa the DNS answer block | |
1049 | which RESET_ADDITIONAL or RESET_ANSWERS | |
1050 | name name of prefix record | |
1051 | yptrptr pointer to the pointer that points to where to hang the next | |
1052 | dns_address structure | |
1053 | bits number of bits we have already got | |
1054 | bitvec the bits we have already got | |
1055 | ||
1056 | Returns: TRUE if any records were found | |
1057 | */ | |
1058 | ||
1059 | static BOOL | |
1060 | dns_find_prefix(dns_answer *dnsa, int which, uschar *name, dns_address | |
1061 | ***yptrptr, int bits, uschar *bitvec) | |
1062 | { | |
1063 | BOOL yield = FALSE; | |
1064 | dns_record *rr; | |
1065 | dns_scan dnss; | |
1066 | ||
1067 | for (rr = dns_next_rr(dnsa, &dnss, which); | |
1068 | rr != NULL; | |
1069 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1070 | { | |
1071 | uschar cbitvec[16]; | |
1072 | if (rr->type != T_A6 || strcmpic(rr->name, name) != 0) continue; | |
1073 | yield = TRUE; | |
1074 | memcpy(cbitvec, bitvec, sizeof(cbitvec)); | |
1075 | dns_complete_a6(yptrptr, dnsa, rr, bits, cbitvec); | |
1076 | } | |
1077 | ||
1078 | return yield; | |
1079 | } | |
1080 | ||
1081 | ||
1082 | ||
1083 | /************************************************* | |
1084 | * Follow chains of A6 records * | |
1085 | *************************************************/ | |
1086 | ||
1087 | /* A6 records may be incomplete, with pointers to other records containing more | |
1088 | bits of the address. There can be a tree structure, leading to a number of | |
1089 | addresses originating from a single initial A6 record. | |
1090 | ||
1091 | Arguments: | |
1092 | yptrptr pointer to the pointer that points to where to hang the next | |
1093 | dns_address structure | |
1094 | dnsa the current DNS answer block | |
1095 | rr the RR we have at present | |
1096 | bits number of bits we have already got | |
1097 | bitvec the bits we have already got | |
1098 | ||
1099 | Returns: nothing | |
1100 | */ | |
1101 | ||
1102 | static void | |
1103 | dns_complete_a6(dns_address ***yptrptr, dns_answer *dnsa, dns_record *rr, | |
1104 | int bits, uschar *bitvec) | |
1105 | { | |
1106 | static uschar bitmask[] = { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 }; | |
1107 | uschar *p = (uschar *)(rr->data); | |
1108 | int prefix_len, suffix_len; | |
1109 | int i, j, k; | |
1110 | uschar *chainptr; | |
1111 | uschar chain[264]; | |
1112 | dns_answer cdnsa; | |
1113 | ||
1114 | /* The prefix length is the first byte. It defines the prefix which is missing | |
1115 | from the data in this record as a number of bits. Zero means this is the end of | |
1116 | a chain. The suffix is the data in this record; only sufficient bytes to hold | |
1117 | it are supplied. There may be zero bytes. We have to ignore trailing bits that | |
1118 | we have already obtained from earlier RRs in the chain. */ | |
1119 | ||
1120 | prefix_len = *p++; /* bits */ | |
1121 | suffix_len = (128 - prefix_len + 7)/8; /* bytes */ | |
1122 | ||
1123 | /* If the prefix in this record is greater than the prefix in the previous | |
1124 | record in the chain, we have to ignore the record (RFC 2874). */ | |
1125 | ||
1126 | if (prefix_len > 128 - bits) return; | |
1127 | ||
1128 | /* In this little loop, the number of bits up to and including the current byte | |
1129 | is held in k. If we have none of the bits in this byte, we can just or it into | |
1130 | the current data. If we have all of the bits in this byte, we skip it. | |
1131 | Otherwise, some masking has to be done. */ | |
1132 | ||
1133 | for (i = suffix_len - 1, j = 15, k = 8; i >= 0; i--) | |
1134 | { | |
1135 | int required = k - bits; | |
1136 | if (required >= 8) bitvec[j] |= p[i]; | |
1137 | else if (required > 0) bitvec[j] |= p[i] & bitmask[required]; | |
1138 | j--; /* I tried putting these in the "for" statement, but gcc muttered */ | |
1139 | k += 8; /* about computed values not being used. */ | |
1140 | } | |
1141 | ||
1142 | /* If the prefix_length is zero, we are at the end of a chain. Build a | |
1143 | dns_address item with the current data, hang it onto the end of the chain, | |
1144 | adjust the hanging pointer, and we are done. */ | |
1145 | ||
1146 | if (prefix_len == 0) | |
1147 | { | |
1148 | dns_address *new = store_get(sizeof(dns_address) + 50); | |
1149 | inet_ntop(AF_INET6, bitvec, CS new->address, 50); | |
1150 | new->next = NULL; | |
1151 | **yptrptr = new; | |
1152 | *yptrptr = &(new->next); | |
1153 | return; | |
1154 | } | |
1155 | ||
1156 | /* Prefix length is not zero. Reset the number of bits that we have collected | |
1157 | so far, and extract the chain name. */ | |
1158 | ||
1159 | bits = 128 - prefix_len; | |
1160 | p += suffix_len; | |
1161 | ||
1162 | chainptr = chain; | |
1163 | while ((i = *p++) != 0) | |
1164 | { | |
1165 | if (chainptr != chain) *chainptr++ = '.'; | |
1166 | memcpy(chainptr, p, i); | |
1167 | chainptr += i; | |
1168 | p += i; | |
1169 | } | |
1170 | *chainptr = 0; | |
1171 | chainptr = chain; | |
1172 | ||
1173 | /* Now scan the current DNS response record to see if the additional section | |
1174 | contains the records we want. This processing can be cut out for testing | |
1175 | purposes. */ | |
1176 | ||
1177 | if (dns_find_prefix(dnsa, RESET_ADDITIONAL, chainptr, yptrptr, bits, bitvec)) | |
1178 | return; | |
1179 | ||
1180 | /* No chain records were found in the current DNS response block. Do a new DNS | |
1181 | lookup to try to find these records. This opens up the possibility of DNS | |
1182 | failures. We ignore them at this point; if all branches of the tree fail, there | |
1183 | will be no addresses at the end. */ | |
1184 | ||
1185 | if (dns_lookup(&cdnsa, chainptr, T_A6, NULL) == DNS_SUCCEED) | |
1186 | (void)dns_find_prefix(&cdnsa, RESET_ANSWERS, chainptr, yptrptr, bits, bitvec); | |
1187 | } | |
1188 | #endif /* HAVE_IPV6 && defined(SUPPORT_A6) */ | |
1189 | ||
1190 | ||
1191 | ||
1192 | ||
1193 | /************************************************* | |
1194 | * Get address(es) from DNS record * | |
1195 | *************************************************/ | |
1196 | ||
1197 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
1198 | supported) for an IPv6 address. In the A6 case, there may be several addresses, | |
1199 | generated by following chains. A recursive function does all the hard work. A6 | |
1200 | records now look like passing into history, so the code is only included when | |
1201 | explicitly asked for. | |
1202 | ||
1203 | Argument: | |
1204 | dnsa the DNS answer block | |
1205 | rr the RR | |
1206 | ||
1207 | Returns: pointer a chain of dns_address items | |
1208 | */ | |
1209 | ||
1210 | dns_address * | |
1211 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1212 | { | |
1213 | dns_address *yield = NULL; | |
1214 | ||
1215 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1216 | dns_address **yieldptr = &yield; | |
1217 | uschar bitvec[16]; | |
1218 | #else | |
1219 | dnsa = dnsa; /* Stop picky compilers warning */ | |
1220 | #endif | |
1221 | ||
1222 | if (rr->type == T_A) | |
1223 | { | |
1224 | uschar *p = (uschar *)(rr->data); | |
1225 | yield = store_get(sizeof(dns_address) + 20); | |
1226 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1227 | yield->next = NULL; | |
1228 | } | |
1229 | ||
1230 | #if HAVE_IPV6 | |
1231 | ||
1232 | #ifdef SUPPORT_A6 | |
1233 | else if (rr->type == T_A6) | |
1234 | { | |
1235 | memset(bitvec, 0, sizeof(bitvec)); | |
1236 | dns_complete_a6(&yieldptr, dnsa, rr, 0, bitvec); | |
1237 | } | |
1238 | #endif /* SUPPORT_A6 */ | |
1239 | ||
1240 | else | |
1241 | { | |
1242 | yield = store_get(sizeof(dns_address) + 50); | |
1243 | inet_ntop(AF_INET6, (uschar *)(rr->data), CS yield->address, 50); | |
1244 | yield->next = NULL; | |
1245 | } | |
1246 | #endif /* HAVE_IPV6 */ | |
1247 | ||
1248 | return yield; | |
1249 | } | |
1250 | ||
1251 | /* End of dns.c */ |