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 | 43 | uschar name[256]; |
433a2980 PH |
44 | uschar utilname[256]; |
45 | uschar *aptr = answerptr; /* Locally modified */ | |
46 | struct stat statbuf; | |
47 | ||
48 | /* Remove terminating dot. */ | |
e7726cbf PH |
49 | |
50 | if (domain[len - 1] == '.') len--; | |
51 | Ustrncpy(name, domain, len); | |
52 | name[len] = 0; | |
bef5a11f | 53 | |
433a2980 PH |
54 | /* Look for the fakens utility, and if it exists, call it. */ |
55 | ||
5f3d0983 HSHR |
56 | (void)string_format(utilname, sizeof(utilname), "%s/bin/fakens", |
57 | config_main_directory); | |
433a2980 PH |
58 | |
59 | if (stat(CS utilname, &statbuf) >= 0) | |
bef5a11f | 60 | { |
433a2980 PH |
61 | pid_t pid; |
62 | int infd, outfd, rc; | |
63 | uschar *argv[5]; | |
64 | ||
3735e326 | 65 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", name, dns_text_type(type)); |
433a2980 PH |
66 | |
67 | argv[0] = utilname; | |
5f3d0983 | 68 | argv[1] = config_main_directory; |
433a2980 PH |
69 | argv[2] = name; |
70 | argv[3] = dns_text_type(type); | |
71 | argv[4] = NULL; | |
72 | ||
73 | pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE); | |
74 | if (pid < 0) | |
75 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s", | |
76 | strerror(errno)); | |
77 | ||
78 | len = 0; | |
79 | rc = -1; | |
80 | while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0) | |
81 | { | |
82 | len += rc; | |
83 | aptr += rc; /* Don't modify the actual arguments, because they */ | |
84 | asize -= rc; /* may need to be passed on to res_search(). */ | |
85 | } | |
bef5a11f | 86 | |
aa7751be | 87 | /* If we ran out of output buffer before exhausting the return, |
1fb7660f JH |
88 | carry on reading and counting it. */ |
89 | ||
90 | if (asize == 0) | |
91 | while ((rc = read(outfd, name, sizeof(name))) > 0) | |
92 | len += rc; | |
93 | ||
433a2980 PH |
94 | if (rc < 0) |
95 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s", | |
96 | strerror(errno)); | |
bef5a11f | 97 | |
433a2980 | 98 | switch(child_close(pid, 0)) |
bef5a11f | 99 | { |
433a2980 PH |
100 | case 0: return len; |
101 | case 1: h_errno = HOST_NOT_FOUND; return -1; | |
102 | case 2: h_errno = TRY_AGAIN; return -1; | |
103 | default: | |
104 | case 3: h_errno = NO_RECOVERY; return -1; | |
105 | case 4: h_errno = NO_DATA; return -1; | |
106 | case 5: /* Pass on to res_search() */ | |
107 | DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n"); | |
bef5a11f PH |
108 | } |
109 | } | |
8e013028 HSHR |
110 | else |
111 | { | |
4cea764f | 112 | DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname); |
8e013028 | 113 | } |
bef5a11f | 114 | |
433a2980 | 115 | /* fakens utility not found, or it returned "pass on" */ |
bef5a11f | 116 | |
433a2980 | 117 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
118 | |
119 | return res_search(CS domain, C_IN, type, answerptr, size); | |
bef5a11f PH |
120 | } |
121 | ||
122 | ||
059ec3d9 PH |
123 | |
124 | /************************************************* | |
125 | * Initialize and configure resolver * | |
126 | *************************************************/ | |
127 | ||
128 | /* Initialize the resolver and the storage for holding DNS answers if this is | |
129 | the first time we have been here, and set the resolver options. | |
130 | ||
131 | Arguments: | |
132 | qualify_single TRUE to set the RES_DEFNAMES option | |
133 | search_parents TRUE to set the RES_DNSRCH option | |
8c51eead | 134 | use_dnssec TRUE to set the RES_USE_DNSSEC option |
059ec3d9 PH |
135 | |
136 | Returns: nothing | |
137 | */ | |
138 | ||
139 | void | |
8c51eead | 140 | dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec) |
059ec3d9 | 141 | { |
5bfb4cdf PP |
142 | res_state resp = os_get_dns_resolver_res(); |
143 | ||
144 | if ((resp->options & RES_INIT) == 0) | |
059ec3d9 | 145 | { |
5bfb4cdf PP |
146 | DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */ |
147 | os_put_dns_resolver_res(resp); | |
059ec3d9 | 148 | res_init(); |
5bfb4cdf PP |
149 | DEBUG(D_resolver) resp->options |= RES_DEBUG; |
150 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
151 | } |
152 | ||
5bfb4cdf PP |
153 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
154 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 155 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
156 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
157 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
158 | |
159 | #ifdef RES_USE_EDNS0 | |
160 | if (dns_use_edns0 >= 0) | |
161 | { | |
162 | if (dns_use_edns0) | |
5bfb4cdf | 163 | resp->options |= RES_USE_EDNS0; |
e97d1f08 | 164 | else |
5bfb4cdf | 165 | resp->options &= ~RES_USE_EDNS0; |
e97d1f08 PP |
166 | DEBUG(D_resolver) |
167 | debug_printf("Coerced resolver EDNS0 support %s.\n", | |
168 | dns_use_edns0 ? "on" : "off"); | |
169 | } | |
170 | #else | |
171 | if (dns_use_edns0 >= 0) | |
172 | DEBUG(D_resolver) | |
173 | debug_printf("Unable to %sset EDNS0 without resolver support.\n", | |
174 | dns_use_edns0 ? "" : "un"); | |
175 | #endif | |
5bfb4cdf | 176 | |
1f4a55da PP |
177 | #ifndef DISABLE_DNSSEC |
178 | # ifdef RES_USE_DNSSEC | |
179 | # ifndef RES_USE_EDNS0 | |
180 | # error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ... | |
181 | # endif | |
8c51eead JH |
182 | if (use_dnssec) |
183 | resp->options |= RES_USE_DNSSEC; | |
0fbd9bff | 184 | if (dns_dnssec_ok >= 0) |
1f4a55da | 185 | { |
0fbd9bff | 186 | if (dns_use_edns0 == 0 && dns_dnssec_ok != 0) |
1f4a55da PP |
187 | { |
188 | DEBUG(D_resolver) | |
0fbd9bff | 189 | debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n"); |
1f4a55da PP |
190 | } |
191 | else | |
192 | { | |
0fbd9bff | 193 | if (dns_dnssec_ok) |
1f4a55da PP |
194 | resp->options |= RES_USE_DNSSEC; |
195 | else | |
196 | resp->options &= ~RES_USE_DNSSEC; | |
197 | DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n", | |
0fbd9bff | 198 | dns_dnssec_ok ? "on" : "off"); |
1f4a55da PP |
199 | } |
200 | } | |
201 | # else | |
0fbd9bff | 202 | if (dns_dnssec_ok >= 0) |
1f4a55da PP |
203 | DEBUG(D_resolver) |
204 | debug_printf("Unable to %sset DNSSEC without resolver support.\n", | |
0fbd9bff | 205 | dns_dnssec_ok ? "" : "un"); |
8c51eead JH |
206 | if (use_dnssec) |
207 | DEBUG(D_resolver) | |
93d4b03a | 208 | debug_printf("Unable to set DNSSEC without resolver support.\n"); |
1f4a55da PP |
209 | # endif |
210 | #endif /* DISABLE_DNSSEC */ | |
211 | ||
5bfb4cdf | 212 | os_put_dns_resolver_res(resp); |
059ec3d9 PH |
213 | } |
214 | ||
215 | ||
216 | ||
217 | /************************************************* | |
218 | * Build key name for PTR records * | |
219 | *************************************************/ | |
220 | ||
221 | /* This function inverts an IP address and adds the relevant domain, to produce | |
222 | a name that can be used to look up PTR records. | |
223 | ||
224 | Arguments: | |
225 | string the IP address as a string | |
226 | buffer a suitable buffer, long enough to hold the result | |
227 | ||
228 | Returns: nothing | |
229 | */ | |
230 | ||
231 | void | |
55414b25 | 232 | dns_build_reverse(const uschar *string, uschar *buffer) |
059ec3d9 | 233 | { |
55414b25 | 234 | const uschar *p = string + Ustrlen(string); |
059ec3d9 PH |
235 | uschar *pp = buffer; |
236 | ||
237 | /* Handle IPv4 address */ | |
238 | ||
239 | #if HAVE_IPV6 | |
240 | if (Ustrchr(string, ':') == NULL) | |
241 | #endif | |
242 | { | |
243 | int i; | |
244 | for (i = 0; i < 4; i++) | |
245 | { | |
55414b25 | 246 | const uschar *ppp = p; |
059ec3d9 PH |
247 | while (ppp > string && ppp[-1] != '.') ppp--; |
248 | Ustrncpy(pp, ppp, p - ppp); | |
249 | pp += p - ppp; | |
250 | *pp++ = '.'; | |
251 | p = ppp - 1; | |
252 | } | |
253 | Ustrcpy(pp, "in-addr.arpa"); | |
254 | } | |
255 | ||
256 | /* Handle IPv6 address; convert to binary so as to fill out any | |
257 | abbreviation in the textual form. */ | |
258 | ||
259 | #if HAVE_IPV6 | |
260 | else | |
261 | { | |
262 | int i; | |
263 | int v6[4]; | |
264 | (void)host_aton(string, v6); | |
265 | ||
266 | /* The original specification for IPv6 reverse lookup was to invert each | |
267 | nibble, and look in the ip6.int domain. The domain was subsequently | |
268 | changed to ip6.arpa. */ | |
269 | ||
270 | for (i = 3; i >= 0; i--) | |
271 | { | |
272 | int j; | |
273 | for (j = 0; j < 32; j += 4) | |
274 | { | |
275 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
276 | pp += 2; | |
277 | } | |
278 | } | |
279 | Ustrcpy(pp, "ip6.arpa."); | |
280 | ||
281 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
282 | with A6 records. However, it fell out of favour when they did. The | |
283 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
284 | to make this code do that, but I could not make it work on Solaris 8. The | |
285 | resolver seems to lose the initial backslash somehow. However, now that | |
286 | this style of reverse lookup has been dropped, it doesn't matter. These | |
287 | lines are left here purely for historical interest. */ | |
288 | ||
289 | /************************************************** | |
290 | Ustrcpy(pp, "\\[x"); | |
291 | pp += 3; | |
292 | ||
293 | for (i = 0; i < 4; i++) | |
294 | { | |
295 | sprintf(pp, "%08X", v6[i]); | |
296 | pp += 8; | |
297 | } | |
298 | Ustrcpy(pp, "].ip6.arpa."); | |
299 | **************************************************/ | |
300 | ||
301 | } | |
302 | #endif | |
303 | } | |
304 | ||
305 | ||
306 | ||
307 | ||
308 | /************************************************* | |
309 | * Get next DNS record from answer block * | |
310 | *************************************************/ | |
311 | ||
312 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
313 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
314 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
315 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
316 | |
317 | Arguments: | |
318 | dnsa pointer to dns answer block | |
319 | dnss pointer to dns scan block | |
320 | reset option specifing what portion to scan, as described above | |
321 | ||
322 | Returns: next dns record, or NULL when no more | |
323 | */ | |
324 | ||
325 | dns_record * | |
326 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
327 | { | |
328 | HEADER *h = (HEADER *)dnsa->answer; | |
329 | int namelen; | |
330 | ||
331 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
332 | ||
333 | if (reset != RESET_NEXT) | |
334 | { | |
335 | dnss->rrcount = ntohs(h->qdcount); | |
336 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
337 | ||
338 | /* Skip over questions; failure to expand the name just gives up */ | |
339 | ||
340 | while (dnss->rrcount-- > 0) | |
341 | { | |
342 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
343 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
344 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
345 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
346 | } | |
347 | ||
348 | /* Get the number of answer records. */ | |
349 | ||
350 | dnss->rrcount = ntohs(h->ancount); | |
351 | ||
e5a9dba6 PH |
352 | /* Skip over answers if we want to look at the authority section. Also skip |
353 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
354 | records. */ |
355 | ||
e5a9dba6 PH |
356 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
357 | ||
358 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 359 | { |
059ec3d9 PH |
360 | while (dnss->rrcount-- > 0) |
361 | { | |
362 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
363 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
364 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
365 | dnss->aptr += namelen + 8; /* skip name, type, class & TTL */ | |
366 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
367 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
368 | } | |
e5a9dba6 PH |
369 | dnss->rrcount = (reset == RESET_AUTHORITY) |
370 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
371 | } |
372 | } | |
373 | ||
059ec3d9 PH |
374 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
375 | contains the number of RR records left. */ | |
376 | ||
377 | if (dnss->rrcount-- <= 0) return NULL; | |
378 | ||
379 | /* If expanding the RR domain name fails, behave as if no more records | |
380 | (something safe). */ | |
381 | ||
382 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
383 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
384 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
385 | ||
386 | /* Move the pointer past the name and fill in the rest of the data structure | |
387 | from the following bytes. */ | |
388 | ||
389 | dnss->aptr += namelen; | |
390 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
14b3c5bc JH |
391 | dnss->aptr += 2; /* Don't want class */ |
392 | GETLONG(dnss->srr.ttl, dnss->aptr); /* TTL */ | |
059ec3d9 PH |
393 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ |
394 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
395 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
396 | ||
397 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
398 | for convenience so that the scans can use nice-looking for loops. */ | |
399 | ||
400 | return &(dnss->srr); | |
401 | } | |
402 | ||
403 | ||
8db90b31 HSHR |
404 | /* Extract the AUTHORITY information from the answer. If the |
405 | answer isn't authoritive (AA not set), we do not extract anything. | |
406 | ||
407 | The AUTHORITIVE section contains NS records if | |
408 | the name in question was found, it contains a SOA record | |
409 | otherwise. (This is just from experience and some tests, is there | |
410 | some spec?) | |
411 | ||
412 | We've cycle through the AUTHORITY section, since it may contain | |
413 | other records (e.g. NSEC3) too. */ | |
09b80b4e JH |
414 | |
415 | static const uschar * | |
416 | dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */ | |
9820a77f | 417 | { |
09b80b4e JH |
418 | dns_scan dnss; |
419 | dns_record * rr; | |
420 | HEADER * h = (HEADER *) dnsa->answer; | |
421 | ||
422 | if (!h->nscount || !h->aa) return NULL; | |
423 | for (rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_AUTHORITY); | |
424 | rr; | |
425 | rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_NEXT)) | |
47c20958 | 426 | if (rr->type == (h->ancount ? T_NS : T_SOA)) return rr->name; |
09b80b4e | 427 | return NULL; |
9820a77f HSHR |
428 | } |
429 | ||
430 | ||
059ec3d9 PH |
431 | |
432 | ||
1f4a55da PP |
433 | /************************************************* |
434 | * Return whether AD bit set in DNS result * | |
435 | *************************************************/ | |
436 | ||
437 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
438 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
9820a77f | 439 | (AD = Authentic Data, AA = Authoritive Answer) |
1f4a55da PP |
440 | |
441 | Argument: pointer to dns answer block | |
442 | Returns: bool indicating presence of AD bit | |
443 | */ | |
444 | ||
445 | BOOL | |
4a142059 | 446 | dns_is_secure(const dns_answer * dnsa) |
1f4a55da PP |
447 | { |
448 | #ifdef DISABLE_DNSSEC | |
449 | DEBUG(D_dns) | |
450 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
451 | return FALSE; | |
452 | #else | |
09b80b4e JH |
453 | HEADER * h = (HEADER *) dnsa->answer; |
454 | const uschar * auth_name; | |
455 | const uschar * trusted; | |
9820a77f HSHR |
456 | |
457 | if (h->ad) return TRUE; | |
9820a77f | 458 | |
09b80b4e JH |
459 | /* If the resolver we ask is authoritive for the domain in question, it |
460 | * may not set the AD but the AA bit. If we explicitly trust | |
461 | * the resolver for that domain (via a domainlist in dns_trust_aa), | |
462 | * we return TRUE to indicate a secure answer. | |
463 | */ | |
9820a77f | 464 | |
09b80b4e JH |
465 | if ( !h->aa |
466 | || !dns_trust_aa | |
25bf2076 HSHR |
467 | || !(trusted = expand_string(dns_trust_aa)) |
468 | || !*trusted | |
09b80b4e JH |
469 | || !(auth_name = dns_extract_auth_name(dnsa)) |
470 | || OK != match_isinlist(auth_name, &trusted, 0, NULL, NULL, | |
94431adb | 471 | MCL_DOMAIN, TRUE, NULL) |
09b80b4e JH |
472 | ) |
473 | return FALSE; | |
9820a77f | 474 | |
09b80b4e JH |
475 | DEBUG(D_dns) debug_printf("DNS faked the AD bit " |
476 | "(got AA and matched with dns_trust_aa (%s in %s))\n", | |
477 | auth_name, dns_trust_aa); | |
9820a77f | 478 | |
09b80b4e | 479 | return TRUE; |
1f4a55da PP |
480 | #endif |
481 | } | |
482 | ||
4a142059 JH |
483 | static void |
484 | dns_set_insecure(dns_answer * dnsa) | |
485 | { | |
486 | HEADER * h = (HEADER *)dnsa->answer; | |
487 | h->ad = 0; | |
488 | } | |
489 | ||
221dff13 HSHR |
490 | /************************************************ |
491 | * Check whether the AA bit is set * | |
492 | * We need this to warn if we requested AD * | |
9820a77f | 493 | * from an authoritive server * |
221dff13 HSHR |
494 | ************************************************/ |
495 | ||
496 | BOOL | |
497 | dns_is_aa(const dns_answer *dnsa) | |
498 | { | |
499 | return ((HEADER*)dnsa->answer)->aa; | |
500 | } | |
1f4a55da PP |
501 | |
502 | ||
503 | ||
059ec3d9 PH |
504 | /************************************************* |
505 | * Turn DNS type into text * | |
506 | *************************************************/ | |
507 | ||
885ccd3e PH |
508 | /* Turn the coded record type into a string for printing. All those that Exim |
509 | uses should be included here. | |
059ec3d9 PH |
510 | |
511 | Argument: record type | |
512 | Returns: pointer to string | |
513 | */ | |
514 | ||
515 | uschar * | |
516 | dns_text_type(int t) | |
517 | { | |
518 | switch(t) | |
519 | { | |
33397d19 PH |
520 | case T_A: return US"A"; |
521 | case T_MX: return US"MX"; | |
522 | case T_AAAA: return US"AAAA"; | |
523 | case T_A6: return US"A6"; | |
524 | case T_TXT: return US"TXT"; | |
eae0036b | 525 | case T_SPF: return US"SPF"; |
33397d19 | 526 | case T_PTR: return US"PTR"; |
885ccd3e | 527 | case T_SOA: return US"SOA"; |
33397d19 PH |
528 | case T_SRV: return US"SRV"; |
529 | case T_NS: return US"NS"; | |
8e669ac1 | 530 | case T_CNAME: return US"CNAME"; |
1e06383a | 531 | case T_TLSA: return US"TLSA"; |
33397d19 | 532 | default: return US"?"; |
059ec3d9 PH |
533 | } |
534 | } | |
535 | ||
536 | ||
537 | ||
538 | /************************************************* | |
539 | * Cache a failed DNS lookup result * | |
540 | *************************************************/ | |
541 | ||
542 | /* We cache failed lookup results so as not to experience timeouts many | |
543 | times for the same domain. We need to retain the resolver options because they | |
544 | may change. For successful lookups, we rely on resolver and/or name server | |
545 | caching. | |
546 | ||
547 | Arguments: | |
548 | name the domain name | |
549 | type the lookup type | |
550 | rc the return code | |
551 | ||
552 | Returns: the return code | |
553 | */ | |
554 | ||
555 | static int | |
1dc92d5a | 556 | dns_return(const uschar * name, int type, int rc) |
059ec3d9 | 557 | { |
5bfb4cdf | 558 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
559 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); |
560 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 561 | resp->options); |
059ec3d9 PH |
562 | node->data.val = rc; |
563 | (void)tree_insertnode(&tree_dns_fails, node); | |
564 | return rc; | |
565 | } | |
566 | ||
059ec3d9 PH |
567 | /************************************************* |
568 | * Do basic DNS lookup * | |
569 | *************************************************/ | |
570 | ||
571 | /* Call the resolver to look up the given domain name, using the given type, | |
572 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
573 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
574 | up nameservers that produce this error continually, so there is the option of | |
575 | providing a list of domains for which this is treated as a non-existent | |
576 | host. | |
577 | ||
578 | Arguments: | |
579 | dnsa pointer to dns_answer structure | |
580 | name name to look up | |
581 | type type of DNS record required (T_A, T_MX, etc) | |
582 | ||
583 | Returns: DNS_SUCCEED successful lookup | |
584 | DNS_NOMATCH name not found (NXDOMAIN) | |
585 | or name contains illegal characters (if checking) | |
30e18802 | 586 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
587 | DNS_NODATA domain exists, but no data for this type (NODATA) |
588 | DNS_AGAIN soft failure, try again later | |
589 | DNS_FAIL DNS failure | |
590 | */ | |
591 | ||
592 | int | |
1dc92d5a | 593 | dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type) |
059ec3d9 PH |
594 | { |
595 | #ifndef STAND_ALONE | |
7156b1ef | 596 | int rc = -1; |
55414b25 | 597 | const uschar *save_domain; |
059ec3d9 | 598 | #endif |
5bfb4cdf | 599 | res_state resp = os_get_dns_resolver_res(); |
059ec3d9 PH |
600 | |
601 | tree_node *previous; | |
602 | uschar node_name[290]; | |
603 | ||
604 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
605 | a timeout on one domain doesn't happen time and time again for messages that | |
606 | have many addresses in the same domain. We rely on the resolver and name server | |
607 | caching for successful lookups. */ | |
608 | ||
609 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
5bfb4cdf | 610 | resp->options); |
059ec3d9 PH |
611 | previous = tree_search(tree_dns_fails, node_name); |
612 | if (previous != NULL) | |
613 | { | |
614 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
615 | name, dns_text_type(type), | |
616 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
617 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
618 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
619 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
620 | return previous->data.val; | |
621 | } | |
622 | ||
9d4319df JH |
623 | #ifdef EXPERIMENTAL_INTERNATIONAL |
624 | /* Convert all names to a-label form before doing lookup */ | |
625 | { | |
626 | uschar * alabel; | |
627 | uschar * errstr = NULL; | |
766e7a65 JH |
628 | DEBUG(D_dns) if (string_is_utf8(name)) |
629 | debug_printf("convert utf8 '%s' to alabel for for lookup\n", name); | |
9d4319df JH |
630 | if ((alabel = string_domain_utf8_to_alabel(name, &errstr)), errstr) |
631 | { | |
632 | DEBUG(D_dns) | |
37bf366e | 633 | debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name, |
9d4319df JH |
634 | errstr); |
635 | host_find_failed_syntax = TRUE; | |
636 | return DNS_NOMATCH; | |
637 | } | |
638 | name = alabel; | |
639 | } | |
640 | #endif | |
641 | ||
059ec3d9 PH |
642 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
643 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
644 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
645 | domains cannot be in the DNS. The check is now done by a regular expression; | |
646 | give it space for substring storage to save it having to get its own if the | |
647 | regex has substrings that are used - the default uses a conditional. | |
648 | ||
649 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
650 | lookup, which constructs the names itself, so they should be OK. Besides, | |
651 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
652 | more.) | |
653 | ||
654 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
655 | ||
656 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
657 | ||
482d1455 | 658 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 | 659 | { |
1dc92d5a | 660 | const uschar *checkname = name; |
059ec3d9 PH |
661 | int ovector[3*(EXPAND_MAXN+1)]; |
662 | ||
476be7e2 | 663 | dns_pattern_init(); |
059ec3d9 PH |
664 | |
665 | /* For an SRV lookup, skip over the first two components (the service and | |
666 | protocol names, which both start with an underscore). */ | |
667 | ||
b4161d10 | 668 | if (type == T_SRV || type == T_TLSA) |
059ec3d9 PH |
669 | { |
670 | while (*checkname++ != '.'); | |
671 | while (*checkname++ != '.'); | |
672 | } | |
673 | ||
1dc92d5a | 674 | if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname), |
059ec3d9 PH |
675 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) |
676 | { | |
677 | DEBUG(D_dns) | |
678 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
679 | dns_text_type(type)); | |
680 | host_find_failed_syntax = TRUE; | |
681 | return DNS_NOMATCH; | |
682 | } | |
683 | } | |
684 | ||
685 | #endif /* STAND_ALONE */ | |
686 | ||
687 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
688 | number of bytes the message would need, so we need to check for this case. The |
689 | effect is to truncate overlong data. | |
690 | ||
30e18802 PH |
691 | On some systems, res_search() will recognize "A-for-A" queries and return |
692 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
693 | nameservers are also believed to do this. It is, of course, contrary to the | |
694 | specification of the DNS, so we lock it out. */ | |
695 | ||
cc00f4af | 696 | if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0) |
30e18802 PH |
697 | return DNS_NOMATCH; |
698 | ||
699 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
700 | (res_search), we call fakens_search(), which recognizes certain special |
701 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
702 | ||
cc00f4af JH |
703 | dnsa->answerlen = running_in_test_harness |
704 | ? fakens_search(name, type, dnsa->answer, MAXPACKET) | |
705 | : res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET); | |
059ec3d9 | 706 | |
80a47a2c TK |
707 | if (dnsa->answerlen > MAXPACKET) |
708 | { | |
709 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n", | |
710 | name, dns_text_type(type), dnsa->answerlen, MAXPACKET); | |
711 | dnsa->answerlen = MAXPACKET; | |
712 | } | |
059ec3d9 PH |
713 | |
714 | if (dnsa->answerlen < 0) switch (h_errno) | |
715 | { | |
716 | case HOST_NOT_FOUND: | |
717 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
718 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
719 | return dns_return(name, type, DNS_NOMATCH); | |
720 | ||
721 | case TRY_AGAIN: | |
722 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
723 | name, dns_text_type(type)); | |
724 | ||
725 | /* Cut this out for various test programs */ | |
1dc92d5a | 726 | #ifndef STAND_ALONE |
55414b25 | 727 | save_domain = deliver_domain; |
1dc92d5a | 728 | deliver_domain = string_copy(name); /* set $domain */ |
55414b25 | 729 | rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL, |
059ec3d9 | 730 | MCL_DOMAIN, TRUE, NULL); |
55414b25 | 731 | deliver_domain = save_domain; |
059ec3d9 PH |
732 | if (rc != OK) |
733 | { | |
734 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
735 | return dns_return(name, type, DNS_AGAIN); | |
736 | } | |
737 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
738 | "DNS_NOMATCH\n", name); | |
739 | return dns_return(name, type, DNS_NOMATCH); | |
740 | ||
1dc92d5a | 741 | #else /* For stand-alone tests */ |
059ec3d9 | 742 | return dns_return(name, type, DNS_AGAIN); |
1dc92d5a | 743 | #endif |
059ec3d9 PH |
744 | |
745 | case NO_RECOVERY: | |
746 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
747 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
748 | return dns_return(name, type, DNS_FAIL); | |
749 | ||
750 | case NO_DATA: | |
751 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
752 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
753 | return dns_return(name, type, DNS_NODATA); | |
754 | ||
755 | default: | |
756 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
757 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
758 | return dns_return(name, type, DNS_FAIL); | |
759 | } | |
760 | ||
761 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
762 | name, dns_text_type(type)); | |
763 | ||
764 | return DNS_SUCCEED; | |
765 | } | |
766 | ||
767 | ||
768 | ||
769 | ||
770 | /************************************************ | |
771 | * Do a DNS lookup and handle CNAMES * | |
772 | ************************************************/ | |
773 | ||
774 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
775 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
776 | the DNS, but you are supposed to cope with them if you find them. | |
777 | ||
778 | The assumption is made that if the resolver gives back records of the | |
779 | requested type *and* a CNAME, we don't need to make another call to look up | |
780 | the CNAME. I can't see how it could return only some of the right records. If | |
781 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
782 | won't return any. | |
783 | ||
784 | If fully_qualified_name is not NULL, set it to point to the full name | |
785 | returned by the resolver, if this is different to what it is given, unless | |
786 | the returned name starts with "*" as some nameservers seem to be returning | |
766e7a65 JH |
787 | wildcards in this form. In international mode "different" means "alabel |
788 | forms are different". | |
059ec3d9 PH |
789 | |
790 | Arguments: | |
791 | dnsa pointer to dns_answer structure | |
792 | name domain name to look up | |
793 | type DNS record type (T_A, T_MX, etc) | |
794 | fully_qualified_name if not NULL, return the returned name here if its | |
795 | contents are different (i.e. it must be preset) | |
796 | ||
797 | Returns: DNS_SUCCEED successful lookup | |
798 | DNS_NOMATCH name not found | |
799 | DNS_NODATA no data found | |
800 | DNS_AGAIN soft failure, try again later | |
801 | DNS_FAIL DNS failure | |
802 | */ | |
803 | ||
804 | int | |
1dc92d5a | 805 | dns_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 806 | const uschar **fully_qualified_name) |
059ec3d9 PH |
807 | { |
808 | int i; | |
1dc92d5a | 809 | const uschar *orig_name = name; |
c85b3043 | 810 | BOOL secure_so_far = TRUE; |
059ec3d9 PH |
811 | |
812 | /* Loop to follow CNAME chains so far, but no further... */ | |
813 | ||
814 | for (i = 0; i < 10; i++) | |
815 | { | |
816 | uschar data[256]; | |
817 | dns_record *rr, cname_rr, type_rr; | |
818 | dns_scan dnss; | |
819 | int datalen, rc; | |
820 | ||
821 | /* DNS lookup failures get passed straight back. */ | |
822 | ||
823 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
824 | ||
825 | /* We should have either records of the required type, or a CNAME record, | |
826 | or both. We need to know whether both exist for getting the fully qualified | |
827 | name, but avoid scanning more than necessary. Note that we must copy the | |
828 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
829 | area in the dnsa block. */ | |
830 | ||
831 | cname_rr.data = type_rr.data = NULL; | |
832 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1705dd20 | 833 | rr; |
059ec3d9 PH |
834 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) |
835 | { | |
836 | if (rr->type == type) | |
837 | { | |
838 | if (type_rr.data == NULL) type_rr = *rr; | |
839 | if (cname_rr.data != NULL) break; | |
840 | } | |
841 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
842 | } | |
843 | ||
a2042e78 PH |
844 | /* For the first time round this loop, if a CNAME was found, take the fully |
845 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 846 | |
a2042e78 | 847 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 | 848 | { |
766e7a65 JH |
849 | uschar * rr_name = cname_rr.data ? cname_rr.name |
850 | : type_rr.data ? type_rr.name : NULL; | |
851 | if ( rr_name | |
852 | && Ustrcmp(rr_name, *fully_qualified_name) != 0 | |
853 | && rr_name[0] != '*' | |
854 | #ifdef EXPERIMENTAL_INTERNATIONAL | |
855 | && ( !string_is_utf8(*fully_qualified_name) | |
856 | || Ustrcmp(rr_name, | |
857 | string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0 | |
858 | ) | |
859 | #endif | |
860 | ) | |
861 | *fully_qualified_name = string_copy_dnsdomain(rr_name); | |
059ec3d9 PH |
862 | } |
863 | ||
864 | /* If any data records of the correct type were found, we are done. */ | |
865 | ||
c85b3043 JH |
866 | if (type_rr.data != NULL) |
867 | { | |
868 | if (!secure_so_far) /* mark insecure if any element of CNAME chain was */ | |
4a142059 | 869 | dns_set_insecure(dnsa); |
c85b3043 JH |
870 | return DNS_SUCCEED; |
871 | } | |
059ec3d9 PH |
872 | |
873 | /* If there are no data records, we need to re-scan the DNS using the | |
874 | domain given in the CNAME record, which should exist (otherwise we should | |
875 | have had a failure from dns_lookup). However code against the possibility of | |
876 | its not existing. */ | |
877 | ||
878 | if (cname_rr.data == NULL) return DNS_FAIL; | |
879 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
1dc92d5a | 880 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data)); |
059ec3d9 PH |
881 | if (datalen < 0) return DNS_FAIL; |
882 | name = data; | |
a2042e78 | 883 | |
c85b3043 JH |
884 | if (!dns_is_secure(dnsa)) |
885 | secure_so_far = FALSE; | |
886 | ||
a2042e78 | 887 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); |
059ec3d9 PH |
888 | } /* Loop back to do another lookup */ |
889 | ||
890 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
891 | right... */ | |
892 | ||
893 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
894 | return DNS_FAIL; | |
895 | } | |
896 | ||
897 | ||
898 | ||
33397d19 PH |
899 | |
900 | ||
901 | ||
902 | /************************************************ | |
903 | * Do a DNS lookup and handle virtual types * | |
904 | ************************************************/ | |
905 | ||
9820a77f | 906 | /* This function handles some invented "lookup types" that synthesize features |
8e669ac1 | 907 | not available in the basic types. The special types all have negative values. |
33397d19 PH |
908 | Positive type values are passed straight on to dns_lookup(). |
909 | ||
910 | Arguments: | |
911 | dnsa pointer to dns_answer structure | |
912 | name domain name to look up | |
913 | type DNS record type (T_A, T_MX, etc or a "special") | |
914 | fully_qualified_name if not NULL, return the returned name here if its | |
915 | contents are different (i.e. it must be preset) | |
916 | ||
917 | Returns: DNS_SUCCEED successful lookup | |
918 | DNS_NOMATCH name not found | |
919 | DNS_NODATA no data found | |
920 | DNS_AGAIN soft failure, try again later | |
921 | DNS_FAIL DNS failure | |
922 | */ | |
923 | ||
924 | int | |
1dc92d5a | 925 | dns_special_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 926 | const uschar **fully_qualified_name) |
33397d19 | 927 | { |
d2a2c69b | 928 | switch (type) |
e5a9dba6 | 929 | { |
d2a2c69b JH |
930 | /* The "mx hosts only" type doesn't require any special action here */ |
931 | case T_MXH: | |
1705dd20 | 932 | return dns_lookup(dnsa, name, T_MX, fully_qualified_name); |
d2a2c69b JH |
933 | |
934 | /* Find nameservers for the domain or the nearest enclosing zone, excluding | |
935 | the root servers. */ | |
936 | case T_ZNS: | |
1705dd20 JH |
937 | type = T_NS; |
938 | /* FALLTHROUGH */ | |
d2a2c69b | 939 | case T_SOA: |
1705dd20 JH |
940 | { |
941 | const uschar *d = name; | |
942 | while (d != 0) | |
943 | { | |
944 | int rc = dns_lookup(dnsa, d, type, fully_qualified_name); | |
945 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
946 | while (*d != 0 && *d != '.') d++; | |
947 | if (*d++ == 0) break; | |
948 | } | |
949 | return DNS_NOMATCH; | |
950 | } | |
d2a2c69b JH |
951 | |
952 | /* Try to look up the Client SMTP Authorization SRV record for the name. If | |
953 | there isn't one, search from the top downwards for a CSA record in a parent | |
954 | domain, which might be making assertions about subdomains. If we find a record | |
955 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
956 | can tell whether to look at the explicit authorization field or the subdomain | |
957 | assertion field. */ | |
958 | case T_CSA: | |
1705dd20 JH |
959 | { |
960 | uschar *srvname, *namesuff, *tld, *p; | |
961 | int priority, weight, port; | |
962 | int limit, rc, i; | |
963 | BOOL ipv6; | |
964 | dns_record *rr; | |
965 | dns_scan dnss; | |
966 | ||
967 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
968 | ||
969 | srvname = string_sprintf("_client._smtp.%s", name); | |
970 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
971 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
972 | { | |
973 | if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name); | |
974 | return rc; | |
975 | } | |
d2a2c69b | 976 | |
1705dd20 JH |
977 | /* Search for CSA subdomain assertion SRV records from the top downwards, |
978 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
979 | We skip the top level domains to avoid loading their nameservers and because | |
980 | we know they'll never have CSA SRV records. */ | |
d2a2c69b | 981 | |
1705dd20 JH |
982 | namesuff = Ustrrchr(name, '.'); |
983 | if (namesuff == NULL) return DNS_NOMATCH; | |
984 | tld = namesuff + 1; | |
985 | ipv6 = FALSE; | |
986 | limit = dns_csa_search_limit; | |
987 | ||
988 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
989 | ||
990 | if (strcmpic(namesuff, US".arpa") == 0) | |
991 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
992 | { | |
993 | namesuff -= 8; | |
d2a2c69b | 994 | tld = namesuff + 1; |
1705dd20 JH |
995 | limit = 3; |
996 | } | |
997 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
998 | { | |
999 | namesuff -= 4; | |
1000 | tld = namesuff + 1; | |
1001 | ipv6 = TRUE; | |
1002 | limit = 3; | |
1003 | } | |
d2a2c69b | 1004 | |
1705dd20 | 1005 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); |
d2a2c69b | 1006 | |
1705dd20 JH |
1007 | /* Do not perform the search if the top level or 2nd level domains do not |
1008 | exist. This is quite common, and when it occurs all the search queries would | |
1009 | go to the root or TLD name servers, which is not friendly. So we check the | |
1010 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
1011 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
1012 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
1013 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
1014 | ||
1015 | if (rc == DNS_NOMATCH) | |
1016 | { | |
1017 | /* This is really gross. The successful return value from res_search() is | |
1018 | the packet length, which is stored in dnsa->answerlen. If we get a | |
1019 | negative DNS reply then res_search() returns -1, which causes the bounds | |
1020 | checks for name decompression to fail when it is treated as a packet | |
1021 | length, which in turn causes the authority search to fail. The correct | |
1022 | packet length has been lost inside libresolv, so we have to guess a | |
1023 | replacement value. (The only way to fix this properly would be to | |
1024 | re-implement res_search() and res_query() so that they don't muddle their | |
1025 | success and packet length return values.) For added safety we only reset | |
1026 | the packet length if the packet header looks plausible. */ | |
1027 | ||
1028 | HEADER *h = (HEADER *)dnsa->answer; | |
1029 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
1030 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
1031 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
1032 | && ntohs(h->nscount) >= 1) | |
1033 | dnsa->answerlen = MAXPACKET; | |
1034 | ||
1035 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
1036 | rr; | |
1037 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) | |
1038 | ) | |
1039 | if (rr->type != T_SOA) continue; | |
1040 | else if (strcmpic(rr->name, US"") == 0 || | |
1041 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
1042 | else break; | |
1043 | } | |
d2a2c69b | 1044 | |
1705dd20 JH |
1045 | for (i = 0; i < limit; i++) |
1046 | { | |
1047 | if (ipv6) | |
1048 | { | |
1049 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
1050 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
1051 | namesuff -= 8; | |
1052 | if (namesuff <= name) return DNS_NOMATCH; | |
1053 | } | |
1054 | else | |
1055 | /* Find the start of the preceding domain name label. */ | |
1056 | do | |
1057 | if (--namesuff <= name) return DNS_NOMATCH; | |
1058 | while (*namesuff != '.'); | |
1059 | ||
1060 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
1061 | ||
1062 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
1063 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
1064 | if (rc == DNS_AGAIN) return rc; | |
1065 | if (rc != DNS_SUCCEED) continue; | |
1066 | ||
1067 | /* Check that the SRV record we have found is worth returning. We don't | |
1068 | just return the first one we find, because some lower level SRV record | |
1069 | might make stricter assertions than its parent domain. */ | |
1070 | ||
1071 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
1072 | rr; | |
1073 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
1074 | { | |
1075 | if (rr->type != T_SRV) continue; | |
d2a2c69b | 1076 | |
1705dd20 JH |
1077 | /* Extract the numerical SRV fields (p is incremented) */ |
1078 | p = rr->data; | |
1079 | GETSHORT(priority, p); | |
1080 | GETSHORT(weight, p); weight = weight; /* compiler quietening */ | |
1081 | GETSHORT(port, p); | |
d2a2c69b | 1082 | |
1705dd20 JH |
1083 | /* Check the CSA version number */ |
1084 | if (priority != 1) continue; | |
d2a2c69b | 1085 | |
1705dd20 JH |
1086 | /* If it's making an interesting assertion, return this response. */ |
1087 | if (port & 1) | |
d2a2c69b | 1088 | { |
1705dd20 JH |
1089 | *fully_qualified_name = namesuff + 1; |
1090 | return DNS_SUCCEED; | |
d2a2c69b | 1091 | } |
d2a2c69b | 1092 | } |
1705dd20 JH |
1093 | } |
1094 | return DNS_NOMATCH; | |
1095 | } | |
e5a9dba6 | 1096 | |
d2a2c69b | 1097 | default: |
1705dd20 JH |
1098 | if (type >= 0) |
1099 | return dns_lookup(dnsa, name, type, fully_qualified_name); | |
e5a9dba6 PH |
1100 | } |
1101 | ||
33397d19 PH |
1102 | /* Control should never reach here */ |
1103 | ||
1104 | return DNS_FAIL; | |
1105 | } | |
1106 | ||
1107 | ||
1108 | ||
059ec3d9 PH |
1109 | |
1110 | ||
1111 | /************************************************* | |
1112 | * Get address(es) from DNS record * | |
1113 | *************************************************/ | |
1114 | ||
1115 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
d2a2c69b | 1116 | supported) for an IPv6 address. |
059ec3d9 PH |
1117 | |
1118 | Argument: | |
1119 | dnsa the DNS answer block | |
1120 | rr the RR | |
1121 | ||
e1a3f32f | 1122 | Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun |
059ec3d9 PH |
1123 | */ |
1124 | ||
1125 | dns_address * | |
1126 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1127 | { | |
e1a3f32f JH |
1128 | dns_address * yield = NULL; |
1129 | uschar * dnsa_lim = dnsa->answer + dnsa->answerlen; | |
059ec3d9 PH |
1130 | |
1131 | if (rr->type == T_A) | |
1132 | { | |
d2a2c69b | 1133 | uschar *p = US rr->data; |
e1a3f32f JH |
1134 | if (p + 4 <= dnsa_lim) |
1135 | { | |
1136 | yield = store_get(sizeof(dns_address) + 20); | |
1137 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1138 | yield->next = NULL; | |
1139 | } | |
059ec3d9 PH |
1140 | } |
1141 | ||
1142 | #if HAVE_IPV6 | |
1143 | ||
059ec3d9 PH |
1144 | else |
1145 | { | |
e1a3f32f JH |
1146 | if (rr->data + 16 <= dnsa_lim) |
1147 | { | |
1148 | yield = store_get(sizeof(dns_address) + 50); | |
1149 | inet_ntop(AF_INET6, US rr->data, CS yield->address, 50); | |
1150 | yield->next = NULL; | |
1151 | } | |
059ec3d9 PH |
1152 | } |
1153 | #endif /* HAVE_IPV6 */ | |
1154 | ||
1155 | return yield; | |
1156 | } | |
1157 | ||
476be7e2 JH |
1158 | |
1159 | ||
1160 | void | |
1161 | dns_pattern_init(void) | |
1162 | { | |
1163 | if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names) | |
1164 | regex_check_dns_names = | |
1165 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
1166 | } | |
1167 | ||
8c51eead JH |
1168 | /* vi: aw ai sw=2 |
1169 | */ | |
059ec3d9 | 1170 | /* End of dns.c */ |