Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
3386088d | 5 | /* Copyright (c) University of Cambridge 1995 - 2015 */ |
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 | ||
059ec3d9 | 13 | |
bef5a11f PH |
14 | /************************************************* |
15 | * Fake DNS resolver * | |
16 | *************************************************/ | |
17 | ||
18 | /* This function is called instead of res_search() when Exim is running in its | |
19 | test harness. It recognizes some special domain names, and uses them to force | |
433a2980 PH |
20 | failure and retry responses (optionally with a delay). Otherwise, it calls an |
21 | external utility that mocks-up a nameserver, if it can find the utility. | |
22 | If not, it passes its arguments on to res_search(). The fake nameserver may | |
23 | also return a code specifying that the name should be passed on. | |
bef5a11f PH |
24 | |
25 | Background: the original test suite required a real nameserver to carry the | |
8e013028 | 26 | test zones, whereas the new test suite has the fake server for portability. This |
e7726cbf | 27 | code supports both. |
bef5a11f PH |
28 | |
29 | Arguments: | |
e7726cbf | 30 | domain the domain name |
bef5a11f PH |
31 | type the DNS record type |
32 | answerptr where to put the answer | |
33 | size size of the answer area | |
34 | ||
35 | Returns: length of returned data, or -1 on error (h_errno set) | |
36 | */ | |
37 | ||
38 | static int | |
1dc92d5a | 39 | fakens_search(const uschar *domain, int type, uschar *answerptr, int size) |
bef5a11f | 40 | { |
e7726cbf | 41 | int len = Ustrlen(domain); |
433a2980 | 42 | int asize = size; /* Locally modified */ |
e7726cbf PH |
43 | uschar *endname; |
44 | uschar name[256]; | |
433a2980 PH |
45 | uschar utilname[256]; |
46 | uschar *aptr = answerptr; /* Locally modified */ | |
47 | struct stat statbuf; | |
48 | ||
49 | /* Remove terminating dot. */ | |
e7726cbf PH |
50 | |
51 | if (domain[len - 1] == '.') len--; | |
52 | Ustrncpy(name, domain, len); | |
53 | name[len] = 0; | |
54 | endname = name + len; | |
bef5a11f | 55 | |
433a2980 PH |
56 | /* Look for the fakens utility, and if it exists, call it. */ |
57 | ||
5f3d0983 HSHR |
58 | (void)string_format(utilname, sizeof(utilname), "%s/bin/fakens", |
59 | config_main_directory); | |
433a2980 PH |
60 | |
61 | if (stat(CS utilname, &statbuf) >= 0) | |
bef5a11f | 62 | { |
433a2980 PH |
63 | pid_t pid; |
64 | int infd, outfd, rc; | |
65 | uschar *argv[5]; | |
66 | ||
3735e326 | 67 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", name, dns_text_type(type)); |
433a2980 PH |
68 | |
69 | argv[0] = utilname; | |
5f3d0983 | 70 | argv[1] = config_main_directory; |
433a2980 PH |
71 | argv[2] = name; |
72 | argv[3] = dns_text_type(type); | |
73 | argv[4] = NULL; | |
74 | ||
75 | pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE); | |
76 | if (pid < 0) | |
77 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s", | |
78 | strerror(errno)); | |
79 | ||
80 | len = 0; | |
81 | rc = -1; | |
82 | while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0) | |
83 | { | |
84 | len += rc; | |
85 | aptr += rc; /* Don't modify the actual arguments, because they */ | |
86 | asize -= rc; /* may need to be passed on to res_search(). */ | |
87 | } | |
bef5a11f | 88 | |
1fb7660f JH |
89 | /* If we ran out of output buffer before exhasting the return, |
90 | carry on reading and counting it. */ | |
91 | ||
92 | if (asize == 0) | |
93 | while ((rc = read(outfd, name, sizeof(name))) > 0) | |
94 | len += rc; | |
95 | ||
433a2980 PH |
96 | if (rc < 0) |
97 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s", | |
98 | strerror(errno)); | |
bef5a11f | 99 | |
433a2980 | 100 | switch(child_close(pid, 0)) |
bef5a11f | 101 | { |
433a2980 PH |
102 | case 0: return len; |
103 | case 1: h_errno = HOST_NOT_FOUND; return -1; | |
104 | case 2: h_errno = TRY_AGAIN; return -1; | |
105 | default: | |
106 | case 3: h_errno = NO_RECOVERY; return -1; | |
107 | case 4: h_errno = NO_DATA; return -1; | |
108 | case 5: /* Pass on to res_search() */ | |
109 | DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n"); | |
bef5a11f PH |
110 | } |
111 | } | |
8e013028 HSHR |
112 | else |
113 | { | |
4cea764f | 114 | DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname); |
8e013028 | 115 | } |
bef5a11f | 116 | |
433a2980 | 117 | /* fakens utility not found, or it returned "pass on" */ |
bef5a11f | 118 | |
433a2980 | 119 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
120 | |
121 | return res_search(CS domain, C_IN, type, answerptr, size); | |
bef5a11f PH |
122 | } |
123 | ||
124 | ||
059ec3d9 PH |
125 | |
126 | /************************************************* | |
127 | * Initialize and configure resolver * | |
128 | *************************************************/ | |
129 | ||
130 | /* Initialize the resolver and the storage for holding DNS answers if this is | |
131 | the first time we have been here, and set the resolver options. | |
132 | ||
133 | Arguments: | |
134 | qualify_single TRUE to set the RES_DEFNAMES option | |
135 | search_parents TRUE to set the RES_DNSRCH option | |
8c51eead | 136 | use_dnssec TRUE to set the RES_USE_DNSSEC option |
059ec3d9 PH |
137 | |
138 | Returns: nothing | |
139 | */ | |
140 | ||
141 | void | |
8c51eead | 142 | dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec) |
059ec3d9 | 143 | { |
5bfb4cdf PP |
144 | res_state resp = os_get_dns_resolver_res(); |
145 | ||
146 | if ((resp->options & RES_INIT) == 0) | |
059ec3d9 | 147 | { |
5bfb4cdf PP |
148 | DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */ |
149 | os_put_dns_resolver_res(resp); | |
059ec3d9 | 150 | res_init(); |
5bfb4cdf PP |
151 | DEBUG(D_resolver) resp->options |= RES_DEBUG; |
152 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
153 | } |
154 | ||
5bfb4cdf PP |
155 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
156 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 157 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
158 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
159 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
160 | |
161 | #ifdef RES_USE_EDNS0 | |
162 | if (dns_use_edns0 >= 0) | |
163 | { | |
164 | if (dns_use_edns0) | |
5bfb4cdf | 165 | resp->options |= RES_USE_EDNS0; |
e97d1f08 | 166 | else |
5bfb4cdf | 167 | resp->options &= ~RES_USE_EDNS0; |
e97d1f08 PP |
168 | DEBUG(D_resolver) |
169 | debug_printf("Coerced resolver EDNS0 support %s.\n", | |
170 | dns_use_edns0 ? "on" : "off"); | |
171 | } | |
172 | #else | |
173 | if (dns_use_edns0 >= 0) | |
174 | DEBUG(D_resolver) | |
175 | debug_printf("Unable to %sset EDNS0 without resolver support.\n", | |
176 | dns_use_edns0 ? "" : "un"); | |
177 | #endif | |
5bfb4cdf | 178 | |
1f4a55da PP |
179 | #ifndef DISABLE_DNSSEC |
180 | # ifdef RES_USE_DNSSEC | |
181 | # ifndef RES_USE_EDNS0 | |
182 | # error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ... | |
183 | # endif | |
8c51eead JH |
184 | if (use_dnssec) |
185 | resp->options |= RES_USE_DNSSEC; | |
0fbd9bff | 186 | if (dns_dnssec_ok >= 0) |
1f4a55da | 187 | { |
0fbd9bff | 188 | if (dns_use_edns0 == 0 && dns_dnssec_ok != 0) |
1f4a55da PP |
189 | { |
190 | DEBUG(D_resolver) | |
0fbd9bff | 191 | debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n"); |
1f4a55da PP |
192 | } |
193 | else | |
194 | { | |
0fbd9bff | 195 | if (dns_dnssec_ok) |
1f4a55da PP |
196 | resp->options |= RES_USE_DNSSEC; |
197 | else | |
198 | resp->options &= ~RES_USE_DNSSEC; | |
199 | DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n", | |
0fbd9bff | 200 | dns_dnssec_ok ? "on" : "off"); |
1f4a55da PP |
201 | } |
202 | } | |
203 | # else | |
0fbd9bff | 204 | if (dns_dnssec_ok >= 0) |
1f4a55da PP |
205 | DEBUG(D_resolver) |
206 | debug_printf("Unable to %sset DNSSEC without resolver support.\n", | |
0fbd9bff | 207 | dns_dnssec_ok ? "" : "un"); |
8c51eead JH |
208 | if (use_dnssec) |
209 | DEBUG(D_resolver) | |
93d4b03a | 210 | debug_printf("Unable to set DNSSEC without resolver support.\n"); |
1f4a55da PP |
211 | # endif |
212 | #endif /* DISABLE_DNSSEC */ | |
213 | ||
5bfb4cdf | 214 | os_put_dns_resolver_res(resp); |
059ec3d9 PH |
215 | } |
216 | ||
217 | ||
218 | ||
219 | /************************************************* | |
220 | * Build key name for PTR records * | |
221 | *************************************************/ | |
222 | ||
223 | /* This function inverts an IP address and adds the relevant domain, to produce | |
224 | a name that can be used to look up PTR records. | |
225 | ||
226 | Arguments: | |
227 | string the IP address as a string | |
228 | buffer a suitable buffer, long enough to hold the result | |
229 | ||
230 | Returns: nothing | |
231 | */ | |
232 | ||
233 | void | |
55414b25 | 234 | dns_build_reverse(const uschar *string, uschar *buffer) |
059ec3d9 | 235 | { |
55414b25 | 236 | const uschar *p = string + Ustrlen(string); |
059ec3d9 PH |
237 | uschar *pp = buffer; |
238 | ||
239 | /* Handle IPv4 address */ | |
240 | ||
241 | #if HAVE_IPV6 | |
242 | if (Ustrchr(string, ':') == NULL) | |
243 | #endif | |
244 | { | |
245 | int i; | |
246 | for (i = 0; i < 4; i++) | |
247 | { | |
55414b25 | 248 | const uschar *ppp = p; |
059ec3d9 PH |
249 | while (ppp > string && ppp[-1] != '.') ppp--; |
250 | Ustrncpy(pp, ppp, p - ppp); | |
251 | pp += p - ppp; | |
252 | *pp++ = '.'; | |
253 | p = ppp - 1; | |
254 | } | |
255 | Ustrcpy(pp, "in-addr.arpa"); | |
256 | } | |
257 | ||
258 | /* Handle IPv6 address; convert to binary so as to fill out any | |
259 | abbreviation in the textual form. */ | |
260 | ||
261 | #if HAVE_IPV6 | |
262 | else | |
263 | { | |
264 | int i; | |
265 | int v6[4]; | |
266 | (void)host_aton(string, v6); | |
267 | ||
268 | /* The original specification for IPv6 reverse lookup was to invert each | |
269 | nibble, and look in the ip6.int domain. The domain was subsequently | |
270 | changed to ip6.arpa. */ | |
271 | ||
272 | for (i = 3; i >= 0; i--) | |
273 | { | |
274 | int j; | |
275 | for (j = 0; j < 32; j += 4) | |
276 | { | |
277 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
278 | pp += 2; | |
279 | } | |
280 | } | |
281 | Ustrcpy(pp, "ip6.arpa."); | |
282 | ||
283 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
284 | with A6 records. However, it fell out of favour when they did. The | |
285 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
286 | to make this code do that, but I could not make it work on Solaris 8. The | |
287 | resolver seems to lose the initial backslash somehow. However, now that | |
288 | this style of reverse lookup has been dropped, it doesn't matter. These | |
289 | lines are left here purely for historical interest. */ | |
290 | ||
291 | /************************************************** | |
292 | Ustrcpy(pp, "\\[x"); | |
293 | pp += 3; | |
294 | ||
295 | for (i = 0; i < 4; i++) | |
296 | { | |
297 | sprintf(pp, "%08X", v6[i]); | |
298 | pp += 8; | |
299 | } | |
300 | Ustrcpy(pp, "].ip6.arpa."); | |
301 | **************************************************/ | |
302 | ||
303 | } | |
304 | #endif | |
305 | } | |
306 | ||
307 | ||
308 | ||
309 | ||
310 | /************************************************* | |
311 | * Get next DNS record from answer block * | |
312 | *************************************************/ | |
313 | ||
314 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
315 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
316 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
317 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
318 | |
319 | Arguments: | |
320 | dnsa pointer to dns answer block | |
321 | dnss pointer to dns scan block | |
322 | reset option specifing what portion to scan, as described above | |
323 | ||
324 | Returns: next dns record, or NULL when no more | |
325 | */ | |
326 | ||
327 | dns_record * | |
328 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
329 | { | |
330 | HEADER *h = (HEADER *)dnsa->answer; | |
331 | int namelen; | |
332 | ||
333 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
334 | ||
335 | if (reset != RESET_NEXT) | |
336 | { | |
337 | dnss->rrcount = ntohs(h->qdcount); | |
338 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
339 | ||
340 | /* Skip over questions; failure to expand the name just gives up */ | |
341 | ||
342 | while (dnss->rrcount-- > 0) | |
343 | { | |
344 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
345 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
346 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
347 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
348 | } | |
349 | ||
350 | /* Get the number of answer records. */ | |
351 | ||
352 | dnss->rrcount = ntohs(h->ancount); | |
353 | ||
e5a9dba6 PH |
354 | /* Skip over answers if we want to look at the authority section. Also skip |
355 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
356 | records. */ |
357 | ||
e5a9dba6 PH |
358 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
359 | ||
360 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 361 | { |
059ec3d9 PH |
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 + 8; /* skip name, type, class & TTL */ | |
368 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
369 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
370 | } | |
e5a9dba6 PH |
371 | dnss->rrcount = (reset == RESET_AUTHORITY) |
372 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
373 | } |
374 | } | |
375 | ||
059ec3d9 PH |
376 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
377 | contains the number of RR records left. */ | |
378 | ||
379 | if (dnss->rrcount-- <= 0) return NULL; | |
380 | ||
381 | /* If expanding the RR domain name fails, behave as if no more records | |
382 | (something safe). */ | |
383 | ||
384 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
385 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
386 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
387 | ||
388 | /* Move the pointer past the name and fill in the rest of the data structure | |
389 | from the following bytes. */ | |
390 | ||
391 | dnss->aptr += namelen; | |
392 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
393 | dnss->aptr += 6; /* Don't want class or TTL */ | |
394 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
395 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
396 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
397 | ||
398 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
399 | for convenience so that the scans can use nice-looking for loops. */ | |
400 | ||
401 | return &(dnss->srr); | |
402 | } | |
403 | ||
404 | ||
8db90b31 HSHR |
405 | /* Extract the AUTHORITY information from the answer. If the |
406 | answer isn't authoritive (AA not set), we do not extract anything. | |
407 | ||
408 | The AUTHORITIVE section contains NS records if | |
409 | the name in question was found, it contains a SOA record | |
410 | otherwise. (This is just from experience and some tests, is there | |
411 | some spec?) | |
412 | ||
413 | We've cycle through the AUTHORITY section, since it may contain | |
414 | other records (e.g. NSEC3) too. */ | |
09b80b4e JH |
415 | |
416 | static const uschar * | |
417 | dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */ | |
9820a77f | 418 | { |
09b80b4e JH |
419 | dns_scan dnss; |
420 | dns_record * rr; | |
421 | HEADER * h = (HEADER *) dnsa->answer; | |
422 | ||
423 | if (!h->nscount || !h->aa) return NULL; | |
424 | for (rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_AUTHORITY); | |
425 | rr; | |
426 | rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_NEXT)) | |
8db90b31 | 427 | if (rr->type == h->ancount ? T_NS : T_SOA) return rr->name; |
09b80b4e | 428 | return NULL; |
9820a77f HSHR |
429 | } |
430 | ||
431 | ||
059ec3d9 PH |
432 | |
433 | ||
1f4a55da PP |
434 | /************************************************* |
435 | * Return whether AD bit set in DNS result * | |
436 | *************************************************/ | |
437 | ||
438 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
439 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
9820a77f | 440 | (AD = Authentic Data, AA = Authoritive Answer) |
1f4a55da PP |
441 | |
442 | Argument: pointer to dns answer block | |
443 | Returns: bool indicating presence of AD bit | |
444 | */ | |
445 | ||
446 | BOOL | |
4a142059 | 447 | dns_is_secure(const dns_answer * dnsa) |
1f4a55da PP |
448 | { |
449 | #ifdef DISABLE_DNSSEC | |
450 | DEBUG(D_dns) | |
451 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
452 | return FALSE; | |
453 | #else | |
09b80b4e JH |
454 | HEADER * h = (HEADER *) dnsa->answer; |
455 | const uschar * auth_name; | |
456 | const uschar * trusted; | |
9820a77f HSHR |
457 | |
458 | if (h->ad) return TRUE; | |
9820a77f | 459 | |
09b80b4e JH |
460 | /* If the resolver we ask is authoritive for the domain in question, it |
461 | * may not set the AD but the AA bit. If we explicitly trust | |
462 | * the resolver for that domain (via a domainlist in dns_trust_aa), | |
463 | * we return TRUE to indicate a secure answer. | |
464 | */ | |
9820a77f | 465 | |
09b80b4e JH |
466 | if ( !h->aa |
467 | || !dns_trust_aa | |
25bf2076 HSHR |
468 | || !(trusted = expand_string(dns_trust_aa)) |
469 | || !*trusted | |
09b80b4e JH |
470 | || !(auth_name = dns_extract_auth_name(dnsa)) |
471 | || OK != match_isinlist(auth_name, &trusted, 0, NULL, NULL, | |
472 | MCL_DOMAIN, TRUE, NULL) | |
473 | ) | |
474 | return FALSE; | |
9820a77f | 475 | |
09b80b4e JH |
476 | DEBUG(D_dns) debug_printf("DNS faked the AD bit " |
477 | "(got AA and matched with dns_trust_aa (%s in %s))\n", | |
478 | auth_name, dns_trust_aa); | |
9820a77f | 479 | |
09b80b4e | 480 | return TRUE; |
1f4a55da PP |
481 | #endif |
482 | } | |
483 | ||
4a142059 JH |
484 | static void |
485 | dns_set_insecure(dns_answer * dnsa) | |
486 | { | |
487 | HEADER * h = (HEADER *)dnsa->answer; | |
488 | h->ad = 0; | |
489 | } | |
490 | ||
221dff13 HSHR |
491 | /************************************************ |
492 | * Check whether the AA bit is set * | |
493 | * We need this to warn if we requested AD * | |
9820a77f | 494 | * from an authoritive server * |
221dff13 HSHR |
495 | ************************************************/ |
496 | ||
497 | BOOL | |
498 | dns_is_aa(const dns_answer *dnsa) | |
499 | { | |
500 | return ((HEADER*)dnsa->answer)->aa; | |
501 | } | |
1f4a55da PP |
502 | |
503 | ||
504 | ||
059ec3d9 PH |
505 | /************************************************* |
506 | * Turn DNS type into text * | |
507 | *************************************************/ | |
508 | ||
885ccd3e PH |
509 | /* Turn the coded record type into a string for printing. All those that Exim |
510 | uses should be included here. | |
059ec3d9 PH |
511 | |
512 | Argument: record type | |
513 | Returns: pointer to string | |
514 | */ | |
515 | ||
516 | uschar * | |
517 | dns_text_type(int t) | |
518 | { | |
519 | switch(t) | |
520 | { | |
33397d19 PH |
521 | case T_A: return US"A"; |
522 | case T_MX: return US"MX"; | |
523 | case T_AAAA: return US"AAAA"; | |
524 | case T_A6: return US"A6"; | |
525 | case T_TXT: return US"TXT"; | |
eae0036b | 526 | case T_SPF: return US"SPF"; |
33397d19 | 527 | case T_PTR: return US"PTR"; |
885ccd3e | 528 | case T_SOA: return US"SOA"; |
33397d19 PH |
529 | case T_SRV: return US"SRV"; |
530 | case T_NS: return US"NS"; | |
8e669ac1 | 531 | case T_CNAME: return US"CNAME"; |
1e06383a | 532 | case T_TLSA: return US"TLSA"; |
33397d19 | 533 | default: return US"?"; |
059ec3d9 PH |
534 | } |
535 | } | |
536 | ||
537 | ||
538 | ||
539 | /************************************************* | |
540 | * Cache a failed DNS lookup result * | |
541 | *************************************************/ | |
542 | ||
543 | /* We cache failed lookup results so as not to experience timeouts many | |
544 | times for the same domain. We need to retain the resolver options because they | |
545 | may change. For successful lookups, we rely on resolver and/or name server | |
546 | caching. | |
547 | ||
548 | Arguments: | |
549 | name the domain name | |
550 | type the lookup type | |
551 | rc the return code | |
552 | ||
553 | Returns: the return code | |
554 | */ | |
555 | ||
556 | static int | |
1dc92d5a | 557 | dns_return(const uschar * name, int type, int rc) |
059ec3d9 | 558 | { |
5bfb4cdf | 559 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
560 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); |
561 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 562 | resp->options); |
059ec3d9 PH |
563 | node->data.val = rc; |
564 | (void)tree_insertnode(&tree_dns_fails, node); | |
565 | return rc; | |
566 | } | |
567 | ||
059ec3d9 PH |
568 | /************************************************* |
569 | * Do basic DNS lookup * | |
570 | *************************************************/ | |
571 | ||
572 | /* Call the resolver to look up the given domain name, using the given type, | |
573 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
574 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
575 | up nameservers that produce this error continually, so there is the option of | |
576 | providing a list of domains for which this is treated as a non-existent | |
577 | host. | |
578 | ||
579 | Arguments: | |
580 | dnsa pointer to dns_answer structure | |
581 | name name to look up | |
582 | type type of DNS record required (T_A, T_MX, etc) | |
583 | ||
584 | Returns: DNS_SUCCEED successful lookup | |
585 | DNS_NOMATCH name not found (NXDOMAIN) | |
586 | or name contains illegal characters (if checking) | |
30e18802 | 587 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
588 | DNS_NODATA domain exists, but no data for this type (NODATA) |
589 | DNS_AGAIN soft failure, try again later | |
590 | DNS_FAIL DNS failure | |
591 | */ | |
592 | ||
593 | int | |
1dc92d5a | 594 | dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type) |
059ec3d9 PH |
595 | { |
596 | #ifndef STAND_ALONE | |
7156b1ef | 597 | int rc = -1; |
55414b25 | 598 | const uschar *save_domain; |
059ec3d9 | 599 | #endif |
5bfb4cdf | 600 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
601 | |
602 | tree_node *previous; | |
603 | uschar node_name[290]; | |
604 | ||
605 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
606 | a timeout on one domain doesn't happen time and time again for messages that | |
607 | have many addresses in the same domain. We rely on the resolver and name server | |
608 | caching for successful lookups. */ | |
609 | ||
610 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 611 | resp->options); |
059ec3d9 PH |
612 | previous = tree_search(tree_dns_fails, node_name); |
613 | if (previous != NULL) | |
614 | { | |
615 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
616 | name, dns_text_type(type), | |
617 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
618 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
619 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
620 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
621 | return previous->data.val; | |
622 | } | |
623 | ||
9d4319df JH |
624 | #ifdef EXPERIMENTAL_INTERNATIONAL |
625 | /* Convert all names to a-label form before doing lookup */ | |
626 | { | |
627 | uschar * alabel; | |
628 | uschar * errstr = NULL; | |
766e7a65 JH |
629 | DEBUG(D_dns) if (string_is_utf8(name)) |
630 | debug_printf("convert utf8 '%s' to alabel for for lookup\n", name); | |
9d4319df JH |
631 | if ((alabel = string_domain_utf8_to_alabel(name, &errstr)), errstr) |
632 | { | |
633 | DEBUG(D_dns) | |
37bf366e | 634 | debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name, |
9d4319df JH |
635 | errstr); |
636 | host_find_failed_syntax = TRUE; | |
637 | return DNS_NOMATCH; | |
638 | } | |
639 | name = alabel; | |
640 | } | |
641 | #endif | |
642 | ||
059ec3d9 PH |
643 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
644 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
645 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
646 | domains cannot be in the DNS. The check is now done by a regular expression; | |
647 | give it space for substring storage to save it having to get its own if the | |
648 | regex has substrings that are used - the default uses a conditional. | |
649 | ||
650 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
651 | lookup, which constructs the names itself, so they should be OK. Besides, | |
652 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
653 | more.) | |
654 | ||
655 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
656 | ||
657 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
658 | ||
482d1455 | 659 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 | 660 | { |
1dc92d5a | 661 | const uschar *checkname = name; |
059ec3d9 PH |
662 | int ovector[3*(EXPAND_MAXN+1)]; |
663 | ||
476be7e2 | 664 | dns_pattern_init(); |
059ec3d9 PH |
665 | |
666 | /* For an SRV lookup, skip over the first two components (the service and | |
667 | protocol names, which both start with an underscore). */ | |
668 | ||
b4161d10 | 669 | if (type == T_SRV || type == T_TLSA) |
059ec3d9 PH |
670 | { |
671 | while (*checkname++ != '.'); | |
672 | while (*checkname++ != '.'); | |
673 | } | |
674 | ||
1dc92d5a | 675 | if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname), |
059ec3d9 PH |
676 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) |
677 | { | |
678 | DEBUG(D_dns) | |
679 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
680 | dns_text_type(type)); | |
681 | host_find_failed_syntax = TRUE; | |
682 | return DNS_NOMATCH; | |
683 | } | |
684 | } | |
685 | ||
686 | #endif /* STAND_ALONE */ | |
687 | ||
688 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
689 | number of bytes the message would need, so we need to check for this case. The |
690 | effect is to truncate overlong data. | |
691 | ||
30e18802 PH |
692 | On some systems, res_search() will recognize "A-for-A" queries and return |
693 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
694 | nameservers are also believed to do this. It is, of course, contrary to the | |
695 | specification of the DNS, so we lock it out. */ | |
696 | ||
cc00f4af | 697 | if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0) |
30e18802 PH |
698 | return DNS_NOMATCH; |
699 | ||
700 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
701 | (res_search), we call fakens_search(), which recognizes certain special |
702 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
703 | ||
cc00f4af JH |
704 | dnsa->answerlen = running_in_test_harness |
705 | ? fakens_search(name, type, dnsa->answer, MAXPACKET) | |
706 | : res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET); | |
059ec3d9 | 707 | |
80a47a2c TK |
708 | if (dnsa->answerlen > MAXPACKET) |
709 | { | |
710 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n", | |
711 | name, dns_text_type(type), dnsa->answerlen, MAXPACKET); | |
712 | dnsa->answerlen = MAXPACKET; | |
713 | } | |
059ec3d9 PH |
714 | |
715 | if (dnsa->answerlen < 0) switch (h_errno) | |
716 | { | |
717 | case HOST_NOT_FOUND: | |
718 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
719 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
720 | return dns_return(name, type, DNS_NOMATCH); | |
721 | ||
722 | case TRY_AGAIN: | |
723 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
724 | name, dns_text_type(type)); | |
725 | ||
726 | /* Cut this out for various test programs */ | |
1dc92d5a | 727 | #ifndef STAND_ALONE |
55414b25 | 728 | save_domain = deliver_domain; |
1dc92d5a | 729 | deliver_domain = string_copy(name); /* set $domain */ |
55414b25 | 730 | rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL, |
059ec3d9 | 731 | MCL_DOMAIN, TRUE, NULL); |
55414b25 | 732 | deliver_domain = save_domain; |
059ec3d9 PH |
733 | if (rc != OK) |
734 | { | |
735 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
736 | return dns_return(name, type, DNS_AGAIN); | |
737 | } | |
738 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
739 | "DNS_NOMATCH\n", name); | |
740 | return dns_return(name, type, DNS_NOMATCH); | |
741 | ||
1dc92d5a | 742 | #else /* For stand-alone tests */ |
059ec3d9 | 743 | return dns_return(name, type, DNS_AGAIN); |
1dc92d5a | 744 | #endif |
059ec3d9 PH |
745 | |
746 | case NO_RECOVERY: | |
747 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
748 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
749 | return dns_return(name, type, DNS_FAIL); | |
750 | ||
751 | case NO_DATA: | |
752 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
753 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
754 | return dns_return(name, type, DNS_NODATA); | |
755 | ||
756 | default: | |
757 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
758 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
759 | return dns_return(name, type, DNS_FAIL); | |
760 | } | |
761 | ||
762 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
763 | name, dns_text_type(type)); | |
764 | ||
765 | return DNS_SUCCEED; | |
766 | } | |
767 | ||
768 | ||
769 | ||
770 | ||
771 | /************************************************ | |
772 | * Do a DNS lookup and handle CNAMES * | |
773 | ************************************************/ | |
774 | ||
775 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
776 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
777 | the DNS, but you are supposed to cope with them if you find them. | |
778 | ||
779 | The assumption is made that if the resolver gives back records of the | |
780 | requested type *and* a CNAME, we don't need to make another call to look up | |
781 | the CNAME. I can't see how it could return only some of the right records. If | |
782 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
783 | won't return any. | |
784 | ||
785 | If fully_qualified_name is not NULL, set it to point to the full name | |
786 | returned by the resolver, if this is different to what it is given, unless | |
787 | the returned name starts with "*" as some nameservers seem to be returning | |
766e7a65 JH |
788 | wildcards in this form. In international mode "different" means "alabel |
789 | forms are different". | |
059ec3d9 PH |
790 | |
791 | Arguments: | |
792 | dnsa pointer to dns_answer structure | |
793 | name domain name to look up | |
794 | type DNS record type (T_A, T_MX, etc) | |
795 | fully_qualified_name if not NULL, return the returned name here if its | |
796 | contents are different (i.e. it must be preset) | |
797 | ||
798 | Returns: DNS_SUCCEED successful lookup | |
799 | DNS_NOMATCH name not found | |
800 | DNS_NODATA no data found | |
801 | DNS_AGAIN soft failure, try again later | |
802 | DNS_FAIL DNS failure | |
803 | */ | |
804 | ||
805 | int | |
1dc92d5a | 806 | dns_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 807 | const uschar **fully_qualified_name) |
059ec3d9 PH |
808 | { |
809 | int i; | |
1dc92d5a | 810 | const uschar *orig_name = name; |
c85b3043 | 811 | BOOL secure_so_far = TRUE; |
059ec3d9 PH |
812 | |
813 | /* Loop to follow CNAME chains so far, but no further... */ | |
814 | ||
815 | for (i = 0; i < 10; i++) | |
816 | { | |
817 | uschar data[256]; | |
818 | dns_record *rr, cname_rr, type_rr; | |
819 | dns_scan dnss; | |
820 | int datalen, rc; | |
821 | ||
822 | /* DNS lookup failures get passed straight back. */ | |
823 | ||
824 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
825 | ||
826 | /* We should have either records of the required type, or a CNAME record, | |
827 | or both. We need to know whether both exist for getting the fully qualified | |
828 | name, but avoid scanning more than necessary. Note that we must copy the | |
829 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
830 | area in the dnsa block. */ | |
831 | ||
832 | cname_rr.data = type_rr.data = NULL; | |
833 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1705dd20 | 834 | rr; |
059ec3d9 PH |
835 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) |
836 | { | |
837 | if (rr->type == type) | |
838 | { | |
839 | if (type_rr.data == NULL) type_rr = *rr; | |
840 | if (cname_rr.data != NULL) break; | |
841 | } | |
842 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
843 | } | |
844 | ||
a2042e78 PH |
845 | /* For the first time round this loop, if a CNAME was found, take the fully |
846 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 847 | |
a2042e78 | 848 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 | 849 | { |
766e7a65 JH |
850 | uschar * rr_name = cname_rr.data ? cname_rr.name |
851 | : type_rr.data ? type_rr.name : NULL; | |
852 | if ( rr_name | |
853 | && Ustrcmp(rr_name, *fully_qualified_name) != 0 | |
854 | && rr_name[0] != '*' | |
855 | #ifdef EXPERIMENTAL_INTERNATIONAL | |
856 | && ( !string_is_utf8(*fully_qualified_name) | |
857 | || Ustrcmp(rr_name, | |
858 | string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0 | |
859 | ) | |
860 | #endif | |
861 | ) | |
862 | *fully_qualified_name = string_copy_dnsdomain(rr_name); | |
059ec3d9 PH |
863 | } |
864 | ||
865 | /* If any data records of the correct type were found, we are done. */ | |
866 | ||
c85b3043 JH |
867 | if (type_rr.data != NULL) |
868 | { | |
869 | if (!secure_so_far) /* mark insecure if any element of CNAME chain was */ | |
4a142059 | 870 | dns_set_insecure(dnsa); |
c85b3043 JH |
871 | return DNS_SUCCEED; |
872 | } | |
059ec3d9 PH |
873 | |
874 | /* If there are no data records, we need to re-scan the DNS using the | |
875 | domain given in the CNAME record, which should exist (otherwise we should | |
876 | have had a failure from dns_lookup). However code against the possibility of | |
877 | its not existing. */ | |
878 | ||
879 | if (cname_rr.data == NULL) return DNS_FAIL; | |
880 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
1dc92d5a | 881 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data)); |
059ec3d9 PH |
882 | if (datalen < 0) return DNS_FAIL; |
883 | name = data; | |
a2042e78 | 884 | |
c85b3043 JH |
885 | if (!dns_is_secure(dnsa)) |
886 | secure_so_far = FALSE; | |
887 | ||
a2042e78 | 888 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); |
059ec3d9 PH |
889 | } /* Loop back to do another lookup */ |
890 | ||
891 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
892 | right... */ | |
893 | ||
894 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
895 | return DNS_FAIL; | |
896 | } | |
897 | ||
898 | ||
899 | ||
33397d19 PH |
900 | |
901 | ||
902 | ||
903 | /************************************************ | |
904 | * Do a DNS lookup and handle virtual types * | |
905 | ************************************************/ | |
906 | ||
9820a77f | 907 | /* This function handles some invented "lookup types" that synthesize features |
8e669ac1 | 908 | not available in the basic types. The special types all have negative values. |
33397d19 PH |
909 | Positive type values are passed straight on to dns_lookup(). |
910 | ||
911 | Arguments: | |
912 | dnsa pointer to dns_answer structure | |
913 | name domain name to look up | |
914 | type DNS record type (T_A, T_MX, etc or a "special") | |
915 | fully_qualified_name if not NULL, return the returned name here if its | |
916 | contents are different (i.e. it must be preset) | |
917 | ||
918 | Returns: DNS_SUCCEED successful lookup | |
919 | DNS_NOMATCH name not found | |
920 | DNS_NODATA no data found | |
921 | DNS_AGAIN soft failure, try again later | |
922 | DNS_FAIL DNS failure | |
923 | */ | |
924 | ||
925 | int | |
1dc92d5a | 926 | dns_special_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 927 | const uschar **fully_qualified_name) |
33397d19 | 928 | { |
d2a2c69b | 929 | switch (type) |
e5a9dba6 | 930 | { |
d2a2c69b JH |
931 | /* The "mx hosts only" type doesn't require any special action here */ |
932 | case T_MXH: | |
1705dd20 | 933 | return dns_lookup(dnsa, name, T_MX, fully_qualified_name); |
d2a2c69b JH |
934 | |
935 | /* Find nameservers for the domain or the nearest enclosing zone, excluding | |
936 | the root servers. */ | |
937 | case T_ZNS: | |
1705dd20 JH |
938 | type = T_NS; |
939 | /* FALLTHROUGH */ | |
d2a2c69b | 940 | case T_SOA: |
1705dd20 JH |
941 | { |
942 | const uschar *d = name; | |
943 | while (d != 0) | |
944 | { | |
945 | int rc = dns_lookup(dnsa, d, type, fully_qualified_name); | |
946 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
947 | while (*d != 0 && *d != '.') d++; | |
948 | if (*d++ == 0) break; | |
949 | } | |
950 | return DNS_NOMATCH; | |
951 | } | |
d2a2c69b JH |
952 | |
953 | /* Try to look up the Client SMTP Authorization SRV record for the name. If | |
954 | there isn't one, search from the top downwards for a CSA record in a parent | |
955 | domain, which might be making assertions about subdomains. If we find a record | |
956 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
957 | can tell whether to look at the explicit authorization field or the subdomain | |
958 | assertion field. */ | |
959 | case T_CSA: | |
1705dd20 JH |
960 | { |
961 | uschar *srvname, *namesuff, *tld, *p; | |
962 | int priority, weight, port; | |
963 | int limit, rc, i; | |
964 | BOOL ipv6; | |
965 | dns_record *rr; | |
966 | dns_scan dnss; | |
967 | ||
968 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
969 | ||
970 | srvname = string_sprintf("_client._smtp.%s", name); | |
971 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
972 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
973 | { | |
974 | if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name); | |
975 | return rc; | |
976 | } | |
d2a2c69b | 977 | |
1705dd20 JH |
978 | /* Search for CSA subdomain assertion SRV records from the top downwards, |
979 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
980 | We skip the top level domains to avoid loading their nameservers and because | |
981 | we know they'll never have CSA SRV records. */ | |
d2a2c69b | 982 | |
1705dd20 JH |
983 | namesuff = Ustrrchr(name, '.'); |
984 | if (namesuff == NULL) return DNS_NOMATCH; | |
985 | tld = namesuff + 1; | |
986 | ipv6 = FALSE; | |
987 | limit = dns_csa_search_limit; | |
988 | ||
989 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
990 | ||
991 | if (strcmpic(namesuff, US".arpa") == 0) | |
992 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
993 | { | |
994 | namesuff -= 8; | |
d2a2c69b | 995 | tld = namesuff + 1; |
1705dd20 JH |
996 | limit = 3; |
997 | } | |
998 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
999 | { | |
1000 | namesuff -= 4; | |
1001 | tld = namesuff + 1; | |
1002 | ipv6 = TRUE; | |
1003 | limit = 3; | |
1004 | } | |
d2a2c69b | 1005 | |
1705dd20 | 1006 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); |
d2a2c69b | 1007 | |
1705dd20 JH |
1008 | /* Do not perform the search if the top level or 2nd level domains do not |
1009 | exist. This is quite common, and when it occurs all the search queries would | |
1010 | go to the root or TLD name servers, which is not friendly. So we check the | |
1011 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
1012 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
1013 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
1014 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
1015 | ||
1016 | if (rc == DNS_NOMATCH) | |
1017 | { | |
1018 | /* This is really gross. The successful return value from res_search() is | |
1019 | the packet length, which is stored in dnsa->answerlen. If we get a | |
1020 | negative DNS reply then res_search() returns -1, which causes the bounds | |
1021 | checks for name decompression to fail when it is treated as a packet | |
1022 | length, which in turn causes the authority search to fail. The correct | |
1023 | packet length has been lost inside libresolv, so we have to guess a | |
1024 | replacement value. (The only way to fix this properly would be to | |
1025 | re-implement res_search() and res_query() so that they don't muddle their | |
1026 | success and packet length return values.) For added safety we only reset | |
1027 | the packet length if the packet header looks plausible. */ | |
1028 | ||
1029 | HEADER *h = (HEADER *)dnsa->answer; | |
1030 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
1031 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
1032 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
1033 | && ntohs(h->nscount) >= 1) | |
1034 | dnsa->answerlen = MAXPACKET; | |
1035 | ||
1036 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
1037 | rr; | |
1038 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) | |
1039 | ) | |
1040 | if (rr->type != T_SOA) continue; | |
1041 | else if (strcmpic(rr->name, US"") == 0 || | |
1042 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
1043 | else break; | |
1044 | } | |
d2a2c69b | 1045 | |
1705dd20 JH |
1046 | for (i = 0; i < limit; i++) |
1047 | { | |
1048 | if (ipv6) | |
1049 | { | |
1050 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
1051 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
1052 | namesuff -= 8; | |
1053 | if (namesuff <= name) return DNS_NOMATCH; | |
1054 | } | |
1055 | else | |
1056 | /* Find the start of the preceding domain name label. */ | |
1057 | do | |
1058 | if (--namesuff <= name) return DNS_NOMATCH; | |
1059 | while (*namesuff != '.'); | |
1060 | ||
1061 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
1062 | ||
1063 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
1064 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
1065 | if (rc == DNS_AGAIN) return rc; | |
1066 | if (rc != DNS_SUCCEED) continue; | |
1067 | ||
1068 | /* Check that the SRV record we have found is worth returning. We don't | |
1069 | just return the first one we find, because some lower level SRV record | |
1070 | might make stricter assertions than its parent domain. */ | |
1071 | ||
1072 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1073 | rr; | |
1074 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1075 | { | |
1076 | if (rr->type != T_SRV) continue; | |
d2a2c69b | 1077 | |
1705dd20 JH |
1078 | /* Extract the numerical SRV fields (p is incremented) */ |
1079 | p = rr->data; | |
1080 | GETSHORT(priority, p); | |
1081 | GETSHORT(weight, p); weight = weight; /* compiler quietening */ | |
1082 | GETSHORT(port, p); | |
d2a2c69b | 1083 | |
1705dd20 JH |
1084 | /* Check the CSA version number */ |
1085 | if (priority != 1) continue; | |
d2a2c69b | 1086 | |
1705dd20 JH |
1087 | /* If it's making an interesting assertion, return this response. */ |
1088 | if (port & 1) | |
d2a2c69b | 1089 | { |
1705dd20 JH |
1090 | *fully_qualified_name = namesuff + 1; |
1091 | return DNS_SUCCEED; | |
d2a2c69b | 1092 | } |
d2a2c69b | 1093 | } |
1705dd20 JH |
1094 | } |
1095 | return DNS_NOMATCH; | |
1096 | } | |
e5a9dba6 | 1097 | |
d2a2c69b | 1098 | default: |
1705dd20 JH |
1099 | if (type >= 0) |
1100 | return dns_lookup(dnsa, name, type, fully_qualified_name); | |
e5a9dba6 PH |
1101 | } |
1102 | ||
33397d19 PH |
1103 | /* Control should never reach here */ |
1104 | ||
1105 | return DNS_FAIL; | |
1106 | } | |
1107 | ||
1108 | ||
1109 | ||
059ec3d9 PH |
1110 | |
1111 | ||
1112 | /************************************************* | |
1113 | * Get address(es) from DNS record * | |
1114 | *************************************************/ | |
1115 | ||
1116 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
d2a2c69b | 1117 | supported) for an IPv6 address. |
059ec3d9 PH |
1118 | |
1119 | Argument: | |
1120 | dnsa the DNS answer block | |
1121 | rr the RR | |
1122 | ||
e1a3f32f | 1123 | Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun |
059ec3d9 PH |
1124 | */ |
1125 | ||
1126 | dns_address * | |
1127 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1128 | { | |
e1a3f32f JH |
1129 | dns_address * yield = NULL; |
1130 | uschar * dnsa_lim = dnsa->answer + dnsa->answerlen; | |
059ec3d9 PH |
1131 | |
1132 | if (rr->type == T_A) | |
1133 | { | |
d2a2c69b | 1134 | uschar *p = US rr->data; |
e1a3f32f JH |
1135 | if (p + 4 <= dnsa_lim) |
1136 | { | |
1137 | yield = store_get(sizeof(dns_address) + 20); | |
1138 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1139 | yield->next = NULL; | |
1140 | } | |
059ec3d9 PH |
1141 | } |
1142 | ||
1143 | #if HAVE_IPV6 | |
1144 | ||
059ec3d9 PH |
1145 | else |
1146 | { | |
e1a3f32f JH |
1147 | if (rr->data + 16 <= dnsa_lim) |
1148 | { | |
1149 | yield = store_get(sizeof(dns_address) + 50); | |
1150 | inet_ntop(AF_INET6, US rr->data, CS yield->address, 50); | |
1151 | yield->next = NULL; | |
1152 | } | |
059ec3d9 PH |
1153 | } |
1154 | #endif /* HAVE_IPV6 */ | |
1155 | ||
1156 | return yield; | |
1157 | } | |
1158 | ||
476be7e2 JH |
1159 | |
1160 | ||
1161 | void | |
1162 | dns_pattern_init(void) | |
1163 | { | |
1164 | if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names) | |
1165 | regex_check_dns_names = | |
1166 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
1167 | } | |
1168 | ||
8c51eead JH |
1169 | /* vi: aw ai sw=2 |
1170 | */ | |
059ec3d9 | 1171 | /* End of dns.c */ |