Revert "preallocate store for config", which appears to have been a mis-merge. Bug...
[exim.git] / src / src / dns.c
CommitLineData
059ec3d9
PH
1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4
f9ba5e22 5/* Copyright (c) University of Cambridge 1995 - 2018 */
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
bef5a11f
PH
13/*************************************************
14* Fake DNS resolver *
15*************************************************/
16
17/* This function is called instead of res_search() when Exim is running in its
18test harness. It recognizes some special domain names, and uses them to force
433a2980
PH
19failure and retry responses (optionally with a delay). Otherwise, it calls an
20external utility that mocks-up a nameserver, if it can find the utility.
21If not, it passes its arguments on to res_search(). The fake nameserver may
22also return a code specifying that the name should be passed on.
bef5a11f
PH
23
24Background: the original test suite required a real nameserver to carry the
8e013028 25test zones, whereas the new test suite has the fake server for portability. This
e7726cbf 26code supports both.
bef5a11f
PH
27
28Arguments:
e7726cbf 29 domain the domain name
bef5a11f
PH
30 type the DNS record type
31 answerptr where to put the answer
32 size size of the answer area
33
34Returns: length of returned data, or -1 on error (h_errno set)
35*/
36
37static int
1dc92d5a 38fakens_search(const uschar *domain, int type, uschar *answerptr, int size)
bef5a11f 39{
e7726cbf 40int len = Ustrlen(domain);
433a2980 41int asize = size; /* Locally modified */
f3ebb786 42uschar * name;
433a2980
PH
43uschar utilname[256];
44uschar *aptr = answerptr; /* Locally modified */
45struct stat statbuf;
46
47/* Remove terminating dot. */
e7726cbf
PH
48
49if (domain[len - 1] == '.') len--;
f3ebb786 50name = string_copyn(domain, len);
bef5a11f 51
433a2980
PH
52/* Look for the fakens utility, and if it exists, call it. */
53
5f3d0983
HSHR
54(void)string_format(utilname, sizeof(utilname), "%s/bin/fakens",
55 config_main_directory);
433a2980
PH
56
57if (stat(CS utilname, &statbuf) >= 0)
bef5a11f 58 {
433a2980
PH
59 pid_t pid;
60 int infd, outfd, rc;
61 uschar *argv[5];
62
3735e326 63 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", name, dns_text_type(type));
433a2980
PH
64
65 argv[0] = utilname;
5f3d0983 66 argv[1] = config_main_directory;
433a2980
PH
67 argv[2] = name;
68 argv[3] = dns_text_type(type);
69 argv[4] = NULL;
70
71 pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE);
72 if (pid < 0)
73 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s",
74 strerror(errno));
75
76 len = 0;
77 rc = -1;
78 while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0)
79 {
80 len += rc;
81 aptr += rc; /* Don't modify the actual arguments, because they */
82 asize -= rc; /* may need to be passed on to res_search(). */
83 }
bef5a11f 84
aa7751be 85 /* If we ran out of output buffer before exhausting the return,
1fb7660f
JH
86 carry on reading and counting it. */
87
88 if (asize == 0)
89 while ((rc = read(outfd, name, sizeof(name))) > 0)
90 len += rc;
91
433a2980
PH
92 if (rc < 0)
93 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s",
94 strerror(errno));
bef5a11f 95
433a2980 96 switch(child_close(pid, 0))
bef5a11f 97 {
433a2980
PH
98 case 0: return len;
99 case 1: h_errno = HOST_NOT_FOUND; return -1;
100 case 2: h_errno = TRY_AGAIN; return -1;
101 default:
102 case 3: h_errno = NO_RECOVERY; return -1;
103 case 4: h_errno = NO_DATA; return -1;
104 case 5: /* Pass on to res_search() */
105 DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n");
bef5a11f
PH
106 }
107 }
8e013028
HSHR
108else
109 {
4cea764f 110 DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname);
8e013028 111 }
bef5a11f 112
433a2980 113/* fakens utility not found, or it returned "pass on" */
bef5a11f 114
433a2980 115DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain);
e7726cbf
PH
116
117return res_search(CS domain, C_IN, type, answerptr, size);
bef5a11f
PH
118}
119
120
059ec3d9
PH
121
122/*************************************************
123* Initialize and configure resolver *
124*************************************************/
125
126/* Initialize the resolver and the storage for holding DNS answers if this is
127the first time we have been here, and set the resolver options.
128
129Arguments:
130 qualify_single TRUE to set the RES_DEFNAMES option
131 search_parents TRUE to set the RES_DNSRCH option
8c51eead 132 use_dnssec TRUE to set the RES_USE_DNSSEC option
059ec3d9
PH
133
134Returns: nothing
135*/
136
137void
8c51eead 138dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec)
059ec3d9 139{
5bfb4cdf
PP
140res_state resp = os_get_dns_resolver_res();
141
142if ((resp->options & RES_INIT) == 0)
059ec3d9 143 {
5bfb4cdf
PP
144 DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */
145 os_put_dns_resolver_res(resp);
059ec3d9 146 res_init();
5bfb4cdf
PP
147 DEBUG(D_resolver) resp->options |= RES_DEBUG;
148 os_put_dns_resolver_res(resp);
059ec3d9
PH
149 }
150
5bfb4cdf
PP
151resp->options &= ~(RES_DNSRCH | RES_DEFNAMES);
152resp->options |= (qualify_single? RES_DEFNAMES : 0) |
059ec3d9 153 (search_parents? RES_DNSRCH : 0);
5bfb4cdf
PP
154if (dns_retrans > 0) resp->retrans = dns_retrans;
155if (dns_retry > 0) resp->retry = dns_retry;
e97d1f08
PP
156
157#ifdef RES_USE_EDNS0
158if (dns_use_edns0 >= 0)
159 {
160 if (dns_use_edns0)
5bfb4cdf 161 resp->options |= RES_USE_EDNS0;
e97d1f08 162 else
5bfb4cdf 163 resp->options &= ~RES_USE_EDNS0;
e97d1f08
PP
164 DEBUG(D_resolver)
165 debug_printf("Coerced resolver EDNS0 support %s.\n",
166 dns_use_edns0 ? "on" : "off");
167 }
168#else
169if (dns_use_edns0 >= 0)
170 DEBUG(D_resolver)
171 debug_printf("Unable to %sset EDNS0 without resolver support.\n",
172 dns_use_edns0 ? "" : "un");
173#endif
5bfb4cdf 174
1f4a55da
PP
175#ifndef DISABLE_DNSSEC
176# ifdef RES_USE_DNSSEC
177# ifndef RES_USE_EDNS0
178# error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ...
179# endif
8c51eead
JH
180if (use_dnssec)
181 resp->options |= RES_USE_DNSSEC;
0fbd9bff 182if (dns_dnssec_ok >= 0)
1f4a55da 183 {
0fbd9bff 184 if (dns_use_edns0 == 0 && dns_dnssec_ok != 0)
1f4a55da
PP
185 {
186 DEBUG(D_resolver)
0fbd9bff 187 debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n");
1f4a55da
PP
188 }
189 else
190 {
0fbd9bff 191 if (dns_dnssec_ok)
1f4a55da
PP
192 resp->options |= RES_USE_DNSSEC;
193 else
194 resp->options &= ~RES_USE_DNSSEC;
195 DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n",
0fbd9bff 196 dns_dnssec_ok ? "on" : "off");
1f4a55da
PP
197 }
198 }
199# else
0fbd9bff 200if (dns_dnssec_ok >= 0)
1f4a55da
PP
201 DEBUG(D_resolver)
202 debug_printf("Unable to %sset DNSSEC without resolver support.\n",
0fbd9bff 203 dns_dnssec_ok ? "" : "un");
8c51eead
JH
204if (use_dnssec)
205 DEBUG(D_resolver)
93d4b03a 206 debug_printf("Unable to set DNSSEC without resolver support.\n");
1f4a55da
PP
207# endif
208#endif /* DISABLE_DNSSEC */
209
5bfb4cdf 210os_put_dns_resolver_res(resp);
059ec3d9
PH
211}
212
213
214
215/*************************************************
216* Build key name for PTR records *
217*************************************************/
218
219/* This function inverts an IP address and adds the relevant domain, to produce
220a name that can be used to look up PTR records.
221
222Arguments:
223 string the IP address as a string
224 buffer a suitable buffer, long enough to hold the result
225
226Returns: nothing
227*/
228
229void
55414b25 230dns_build_reverse(const uschar *string, uschar *buffer)
059ec3d9 231{
55414b25 232const uschar *p = string + Ustrlen(string);
059ec3d9
PH
233uschar *pp = buffer;
234
235/* Handle IPv4 address */
236
237#if HAVE_IPV6
238if (Ustrchr(string, ':') == NULL)
239#endif
240 {
d7978c0f 241 for (int i = 0; i < 4; i++)
059ec3d9 242 {
55414b25 243 const uschar *ppp = p;
059ec3d9
PH
244 while (ppp > string && ppp[-1] != '.') ppp--;
245 Ustrncpy(pp, ppp, p - ppp);
246 pp += p - ppp;
247 *pp++ = '.';
248 p = ppp - 1;
249 }
f3ebb786 250 Ustrcpy(pp, US"in-addr.arpa");
059ec3d9
PH
251 }
252
253/* Handle IPv6 address; convert to binary so as to fill out any
254abbreviation in the textual form. */
255
256#if HAVE_IPV6
257else
258 {
059ec3d9
PH
259 int v6[4];
260 (void)host_aton(string, v6);
261
262 /* The original specification for IPv6 reverse lookup was to invert each
263 nibble, and look in the ip6.int domain. The domain was subsequently
264 changed to ip6.arpa. */
265
d7978c0f
JH
266 for (int i = 3; i >= 0; i--)
267 for (int j = 0; j < 32; j += 4)
5976eb99 268 pp += sprintf(CS pp, "%x.", (v6[i] >> j) & 15);
f3ebb786 269 Ustrcpy(pp, US"ip6.arpa.");
059ec3d9
PH
270
271 /* Another way of doing IPv6 reverse lookups was proposed in conjunction
272 with A6 records. However, it fell out of favour when they did. The
273 alternative was to construct a binary key, and look in ip6.arpa. I tried
274 to make this code do that, but I could not make it work on Solaris 8. The
275 resolver seems to lose the initial backslash somehow. However, now that
276 this style of reverse lookup has been dropped, it doesn't matter. These
277 lines are left here purely for historical interest. */
278
279 /**************************************************
280 Ustrcpy(pp, "\\[x");
281 pp += 3;
282
d7978c0f 283 for (int i = 0; i < 4; i++)
059ec3d9
PH
284 {
285 sprintf(pp, "%08X", v6[i]);
286 pp += 8;
287 }
f3ebb786 288 Ustrcpy(pp, US"].ip6.arpa.");
059ec3d9
PH
289 **************************************************/
290
291 }
292#endif
293}
294
295
296
297
2a407b17
JH
298/* Increment the aptr in dnss, checking against dnsa length.
299Return: TRUE for a bad result
300*/
301static BOOL
dd708fd7 302dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta)
2a407b17
JH
303{
304return (dnss->aptr += delta) >= dnsa->answer + dnsa->answerlen;
305}
306
059ec3d9
PH
307/*************************************************
308* Get next DNS record from answer block *
309*************************************************/
310
311/* Call this with reset == RESET_ANSWERS to scan the answer block, reset ==
e5a9dba6
PH
312RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to
313scan the additional records, and reset == RESET_NEXT to get the next record.
314The result is in static storage which must be copied if it is to be preserved.
059ec3d9
PH
315
316Arguments:
317 dnsa pointer to dns answer block
318 dnss pointer to dns scan block
4c04137d 319 reset option specifying what portion to scan, as described above
059ec3d9
PH
320
321Returns: next dns record, or NULL when no more
322*/
323
324dns_record *
dd708fd7 325dns_next_rr(const dns_answer *dnsa, dns_scan *dnss, int reset)
059ec3d9 326{
dd708fd7 327const HEADER * h = (const HEADER *)dnsa->answer;
059ec3d9
PH
328int namelen;
329
2a407b17
JH
330char * trace = NULL;
331#ifdef rr_trace
332# define TRACE DEBUG(D_dns)
333#else
334trace = trace;
335# define TRACE if (FALSE)
336#endif
337
059ec3d9
PH
338/* Reset the saved data when requested to, and skip to the first required RR */
339
340if (reset != RESET_NEXT)
341 {
342 dnss->rrcount = ntohs(h->qdcount);
d093f8e5 343 TRACE debug_printf("%s: reset (Q rrcount %d)\n", __FUNCTION__, dnss->rrcount);
059ec3d9
PH
344 dnss->aptr = dnsa->answer + sizeof(HEADER);
345
346 /* Skip over questions; failure to expand the name just gives up */
347
348 while (dnss->rrcount-- > 0)
349 {
2a407b17 350 TRACE trace = "Q-namelen";
059ec3d9 351 namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
2a407b17
JH
352 dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
353 if (namelen < 0) goto null_return;
354 /* skip name & type & class */
355 TRACE trace = "Q-skip";
dd708fd7 356 if (dnss_inc_aptr(dnsa, dnss, namelen+4)) goto null_return;
059ec3d9
PH
357 }
358
359 /* Get the number of answer records. */
360
361 dnss->rrcount = ntohs(h->ancount);
d093f8e5 362 TRACE debug_printf("%s: reset (A rrcount %d)\n", __FUNCTION__, dnss->rrcount);
059ec3d9 363
e5a9dba6
PH
364 /* Skip over answers if we want to look at the authority section. Also skip
365 the NS records (i.e. authority section) if wanting to look at the additional
059ec3d9
PH
366 records. */
367
2a407b17
JH
368 if (reset == RESET_ADDITIONAL)
369 {
370 TRACE debug_printf("%s: additional\n", __FUNCTION__);
371 dnss->rrcount += ntohs(h->nscount);
d093f8e5 372 TRACE debug_printf("%s: reset (NS rrcount %d)\n", __FUNCTION__, dnss->rrcount);
2a407b17 373 }
e5a9dba6
PH
374
375 if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL)
059ec3d9 376 {
2a407b17
JH
377 TRACE if (reset == RESET_AUTHORITY)
378 debug_printf("%s: authority\n", __FUNCTION__);
059ec3d9
PH
379 while (dnss->rrcount-- > 0)
380 {
2a407b17 381 TRACE trace = "A-namelen";
059ec3d9 382 namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
2a407b17
JH
383 dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
384 if (namelen < 0) goto null_return;
385 /* skip name, type, class & TTL */
386 TRACE trace = "A-hdr";
dd708fd7 387 if (dnss_inc_aptr(dnsa, dnss, namelen+8)) goto null_return;
059ec3d9 388 GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */
2a407b17
JH
389 /* skip over it */
390 TRACE trace = "A-skip";
dd708fd7 391 if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size)) goto null_return;
059ec3d9 392 }
2a407b17 393 dnss->rrcount = reset == RESET_AUTHORITY
e5a9dba6 394 ? ntohs(h->nscount) : ntohs(h->arcount);
d093f8e5
JH
395 TRACE debug_printf("%s: reset (%s rrcount %d)\n", __FUNCTION__,
396 reset == RESET_AUTHORITY ? "NS" : "AR", dnss->rrcount);
059ec3d9 397 }
2a407b17 398 TRACE debug_printf("%s: %d RRs to read\n", __FUNCTION__, dnss->rrcount);
059ec3d9 399 }
2a407b17
JH
400else
401 TRACE debug_printf("%s: next (%d left)\n", __FUNCTION__, dnss->rrcount);
059ec3d9 402
059ec3d9
PH
403/* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount
404contains the number of RR records left. */
405
406if (dnss->rrcount-- <= 0) return NULL;
407
408/* If expanding the RR domain name fails, behave as if no more records
409(something safe). */
410
2a407b17 411TRACE trace = "R-namelen";
059ec3d9 412namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr,
2a407b17
JH
413 (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
414if (namelen < 0) goto null_return;
059ec3d9
PH
415
416/* Move the pointer past the name and fill in the rest of the data structure
417from the following bytes. */
418
2a407b17 419TRACE trace = "R-name";
dd708fd7 420if (dnss_inc_aptr(dnsa, dnss, namelen)) goto null_return;
2a407b17
JH
421
422GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */
423TRACE trace = "R-class";
dd708fd7 424if (dnss_inc_aptr(dnsa, dnss, 2)) goto null_return; /* Don't want class */
2a407b17
JH
425GETLONG(dnss->srr.ttl, dnss->aptr); /* TTL */
426GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */
427dnss->srr.data = dnss->aptr; /* The record's data follows */
428
429/* Unchecked increment ok here since no further access on this iteration;
430will be checked on next at "R-name". */
431
432dnss->aptr += dnss->srr.size; /* Advance to next RR */
059ec3d9
PH
433
434/* Return a pointer to the dns_record structure within the dns_answer. This is
435for convenience so that the scans can use nice-looking for loops. */
436
7d8d08c4 437TRACE debug_printf("%s: return %s\n", __FUNCTION__, dns_text_type(dnss->srr.type));
2a407b17
JH
438return &dnss->srr;
439
440null_return:
d093f8e5
JH
441 TRACE debug_printf("%s: terminate (%d RRs left). Last op: %s; errno %d %s\n",
442 __FUNCTION__, dnss->rrcount, trace, errno, strerror(errno));
2a407b17
JH
443 dnss->rrcount = 0;
444 return NULL;
059ec3d9
PH
445}
446
447
8688d177 448/* Extract the AUTHORITY information from the answer. If the answer isn't
4c04137d 449authoritative (AA not set), we do not extract anything.
8db90b31 450
4c04137d 451The AUTHORITY section contains NS records if the name in question was found,
8688d177
JH
452it contains a SOA record otherwise. (This is just from experience and some
453tests, is there some spec?)
8db90b31 454
8688d177
JH
455Scan the whole AUTHORITY section, since it may contain other records
456(e.g. NSEC3) too.
457
458Return: name for the authority, in an allocated string, or NULL if none found */
09b80b4e
JH
459
460static const uschar *
461dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */
9820a77f 462{
09b80b4e 463dns_scan dnss;
dd708fd7 464const HEADER * h = (const HEADER *) dnsa->answer;
09b80b4e 465
8688d177 466if (h->nscount && h->aa)
d7978c0f 467 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
8688d177
JH
468 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
469 if (rr->type == (h->ancount ? T_NS : T_SOA))
470 return string_copy(rr->name);
09b80b4e 471return NULL;
9820a77f
HSHR
472}
473
474
059ec3d9
PH
475
476
477/*************************************************
1f4a55da
PP
478* Return whether AD bit set in DNS result *
479*************************************************/
480
481/* We do not perform DNSSEC work ourselves; if the administrator has installed
482a verifying resolver which sets AD as appropriate, though, we'll use that.
4c04137d 483(AD = Authentic Data, AA = Authoritative Answer)
1f4a55da
PP
484
485Argument: pointer to dns answer block
486Returns: bool indicating presence of AD bit
487*/
488
489BOOL
4a142059 490dns_is_secure(const dns_answer * dnsa)
1f4a55da
PP
491{
492#ifdef DISABLE_DNSSEC
493DEBUG(D_dns)
494 debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n");
495return FALSE;
496#else
dd708fd7 497const HEADER * h = (const HEADER *) dnsa->answer;
09b80b4e
JH
498const uschar * auth_name;
499const uschar * trusted;
9820a77f 500
979c462e 501if (dnsa->answerlen < 0) return FALSE;
9820a77f 502if (h->ad) return TRUE;
9820a77f 503
979c462e
JH
504/* If the resolver we ask is authoritative for the domain in question, it may
505not set the AD but the AA bit. If we explicitly trust the resolver for that
506domain (via a domainlist in dns_trust_aa), we return TRUE to indicate a secure
507answer. */
9820a77f 508
09b80b4e
JH
509if ( !h->aa
510 || !dns_trust_aa
25bf2076
HSHR
511 || !(trusted = expand_string(dns_trust_aa))
512 || !*trusted
09b80b4e
JH
513 || !(auth_name = dns_extract_auth_name(dnsa))
514 || OK != match_isinlist(auth_name, &trusted, 0, NULL, NULL,
94431adb 515 MCL_DOMAIN, TRUE, NULL)
09b80b4e
JH
516 )
517 return FALSE;
9820a77f 518
09b80b4e
JH
519DEBUG(D_dns) debug_printf("DNS faked the AD bit "
520 "(got AA and matched with dns_trust_aa (%s in %s))\n",
521 auth_name, dns_trust_aa);
9820a77f 522
09b80b4e 523return TRUE;
1f4a55da
PP
524#endif
525}
526
4a142059
JH
527static void
528dns_set_insecure(dns_answer * dnsa)
529{
e87c01c7 530#ifndef DISABLE_DNSSEC
4a142059 531HEADER * h = (HEADER *)dnsa->answer;
8688d177 532h->aa = h->ad = 0;
e87c01c7 533#endif
4a142059
JH
534}
535
221dff13
HSHR
536/************************************************
537 * Check whether the AA bit is set *
538 * We need this to warn if we requested AD *
4c04137d 539 * from an authoritative server *
221dff13
HSHR
540 ************************************************/
541
542BOOL
979c462e 543dns_is_aa(const dns_answer * dnsa)
221dff13 544{
e87c01c7
MH
545#ifdef DISABLE_DNSSEC
546return FALSE;
547#else
979c462e 548return dnsa->answerlen >= 0 && ((const HEADER *)dnsa->answer)->aa;
e87c01c7 549#endif
221dff13 550}
1f4a55da
PP
551
552
553
554/*************************************************
059ec3d9
PH
555* Turn DNS type into text *
556*************************************************/
557
885ccd3e
PH
558/* Turn the coded record type into a string for printing. All those that Exim
559uses should be included here.
059ec3d9
PH
560
561Argument: record type
562Returns: pointer to string
563*/
564
565uschar *
566dns_text_type(int t)
567{
568switch(t)
569 {
33397d19
PH
570 case T_A: return US"A";
571 case T_MX: return US"MX";
572 case T_AAAA: return US"AAAA";
573 case T_A6: return US"A6";
574 case T_TXT: return US"TXT";
eae0036b 575 case T_SPF: return US"SPF";
33397d19 576 case T_PTR: return US"PTR";
885ccd3e 577 case T_SOA: return US"SOA";
33397d19
PH
578 case T_SRV: return US"SRV";
579 case T_NS: return US"NS";
8e669ac1 580 case T_CNAME: return US"CNAME";
1e06383a 581 case T_TLSA: return US"TLSA";
33397d19 582 default: return US"?";
059ec3d9
PH
583 }
584}
585
586
587
588/*************************************************
589* Cache a failed DNS lookup result *
590*************************************************/
591
cabf3e99
JH
592static void
593dns_fail_tag(uschar * buf, const uschar * name, int dns_type)
594{
595res_state resp = os_get_dns_resolver_res();
7d8d08c4
JH
596
597/*XX buf needs to be 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1
598We truncate the name here for safety... could use a dynamic string. */
599
cabf3e99
JH
600sprintf(CS buf, "%.255s-%s-%lx", name, dns_text_type(dns_type),
601 (unsigned long) resp->options);
602}
603
604
059ec3d9
PH
605/* We cache failed lookup results so as not to experience timeouts many
606times for the same domain. We need to retain the resolver options because they
607may change. For successful lookups, we rely on resolver and/or name server
608caching.
609
610Arguments:
611 name the domain name
612 type the lookup type
7d8d08c4 613 expiry time TTL expires, or zero for unlimited
059ec3d9
PH
614 rc the return code
615
616Returns: the return code
617*/
618
3a2feed8 619/* we need: 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1 */
7d8d08c4 620#define DNS_FAILTAG_MAX 290
927e32d4 621#define DNS_FAILNODE_SIZE \
3a2feed8 622 (sizeof(expiring_data) + sizeof(tree_node) + DNS_FAILTAG_MAX)
7d8d08c4
JH
623
624static int
625dns_fail_return(const uschar * name, int type, time_t expiry, int rc)
626{
627uschar node_name[DNS_FAILTAG_MAX];
628tree_node * previous, * new;
629expiring_data * e;
630
631dns_fail_tag(node_name, name, type);
632if ((previous = tree_search(tree_dns_fails, node_name)))
633 e = previous->data.ptr;
634else
635 {
3a2feed8
JH
636 e = store_get_perm(DNS_FAILNODE_SIZE, is_tainted(name));
637 new = (void *)(e+1);
7d8d08c4 638 dns_fail_tag(new->name, name, type);
7d8d08c4
JH
639 new->data.ptr = e;
640 (void)tree_insertnode(&tree_dns_fails, new);
641 }
642
643DEBUG(D_dns) debug_printf(" %s neg-cache entry for %s, ttl %d\n",
644 previous ? "update" : "writing",
645 node_name, expiry ? (int)(expiry - time(NULL)) : -1);
646e->expiry = expiry;
647e->data.val = rc;
648return rc;
649}
650
651
652/* Return the cached result of a known-bad lookup, or -1.
653*/
059ec3d9 654static int
7d8d08c4 655dns_fail_cache_hit(const uschar * name, int type)
059ec3d9 656{
7d8d08c4
JH
657uschar node_name[DNS_FAILTAG_MAX];
658tree_node * previous;
659expiring_data * e;
660int val, rc;
661
662dns_fail_tag(node_name, name, type);
663if (!(previous = tree_search(tree_dns_fails, node_name)))
664 return -1;
665
666e = previous->data.ptr;
667val = e->data.val;
668rc = e->expiry && e->expiry <= time(NULL) ? -1 : val;
669
670DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: %scached value %s%s\n",
671 name, dns_text_type(type),
672 rc == -1 ? "" : "using ",
673 val == DNS_NOMATCH ? "DNS_NOMATCH" :
674 val == DNS_NODATA ? "DNS_NODATA" :
675 val == DNS_AGAIN ? "DNS_AGAIN" :
676 val == DNS_FAIL ? "DNS_FAIL" : "??",
677 rc == -1 ? " past valid time" : "");
678
059ec3d9
PH
679return rc;
680}
681
7d8d08c4
JH
682
683
7d8d08c4
JH
684/* This is really gross. The successful return value from res_search() is
685the packet length, which is stored in dnsa->answerlen. If we get a
686negative DNS reply then res_search() returns -1, which causes the bounds
687checks for name decompression to fail when it is treated as a packet
688length, which in turn causes the authority search to fail. The correct
689packet length has been lost inside libresolv, so we have to guess a
690replacement value. (The only way to fix this properly would be to
691re-implement res_search() and res_query() so that they don't muddle their
692success and packet length return values.) For added safety we only reset
693the packet length if the packet header looks plausible. */
694
b574c5ba 695static void
a713f766 696fake_dnsa_len_for_fail(dns_answer * dnsa, int type)
b574c5ba
JH
697{
698const HEADER * h = (const HEADER *)dnsa->answer;
699
700if ( h->qr == 1 /* a response */
701 && h->opcode == QUERY
702 && h->tc == 0 /* nmessage not truncated */
7d8d08c4 703 && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
b574c5ba
JH
704 && ( ntohs(h->qdcount) == 1 /* one question record */
705 || f.running_in_test_harness)
706 && ntohs(h->ancount) == 0 /* no answer records */
707 && ntohs(h->nscount) >= 1) /* authority records */
708 {
a713f766
JH
709 DEBUG(D_dns) debug_printf("faking res_search(%s) response length as %d\n",
710 dns_text_type(type), (int)sizeof(dnsa->answer));
b574c5ba
JH
711 dnsa->answerlen = sizeof(dnsa->answer);
712 }
713}
714
715
716/* Return the TTL suitable for an NXDOMAIN result, which is given
717in the SOA. We hope that one was returned in the lookup, and do not
718bother doing a separate lookup; if not found return a forever TTL.
719*/
720
721time_t
a713f766 722dns_expire_from_soa(dns_answer * dnsa, int type)
b574c5ba
JH
723{
724dns_scan dnss;
725
a713f766 726fake_dnsa_len_for_fail(dnsa, type);
7d8d08c4
JH
727
728for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
729 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
730 ) if (rr->type == T_SOA)
731 {
732 const uschar * p = rr->data;
733 uschar discard_buf[256];
734 int len;
735 unsigned long ttl;
736
737 /* Skip the mname & rname strings */
738
739 if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
740 p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
741 break;
742 p += len;
743 if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
744 p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
745 break;
746 p += len;
747
748 /* Skip the SOA serial, refresh, retry & expire. Grab the TTL */
749
d70fc283 750 if (p > dnsa->answer + dnsa->answerlen - 5 * INT32SZ)
7d8d08c4 751 break;
d70fc283 752 p += 4 * INT32SZ;
7d8d08c4
JH
753 GETLONG(ttl, p);
754
755 return time(NULL) + ttl;
756 }
757DEBUG(D_dns) debug_printf("DNS: no SOA record found for neg-TTL\n");
758return 0;
759}
760
761
059ec3d9
PH
762/*************************************************
763* Do basic DNS lookup *
764*************************************************/
765
766/* Call the resolver to look up the given domain name, using the given type,
767and check the result. The error code TRY_AGAIN is documented as meaning "non-
4c04137d 768Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set
059ec3d9
PH
769up nameservers that produce this error continually, so there is the option of
770providing a list of domains for which this is treated as a non-existent
771host.
772
75c121f0
JH
773The dns_answer structure is pretty big; enough to hold a max-sized DNS message
774- so best allocated from fast-release memory. As of writing, all our callers
775use a stack-auto variable.
776
059ec3d9
PH
777Arguments:
778 dnsa pointer to dns_answer structure
779 name name to look up
780 type type of DNS record required (T_A, T_MX, etc)
781
782Returns: DNS_SUCCEED successful lookup
783 DNS_NOMATCH name not found (NXDOMAIN)
784 or name contains illegal characters (if checking)
30e18802 785 or name is an IP address (for IP address lookup)
059ec3d9
PH
786 DNS_NODATA domain exists, but no data for this type (NODATA)
787 DNS_AGAIN soft failure, try again later
788 DNS_FAIL DNS failure
789*/
790
791int
7d8d08c4 792dns_basic_lookup(dns_answer * dnsa, const uschar * name, int type)
059ec3d9 793{
7d8d08c4 794int rc;
059ec3d9 795#ifndef STAND_ALONE
7d8d08c4 796const uschar * save_domain;
059ec3d9
PH
797#endif
798
059ec3d9
PH
799/* DNS lookup failures of any kind are cached in a tree. This is mainly so that
800a timeout on one domain doesn't happen time and time again for messages that
801have many addresses in the same domain. We rely on the resolver and name server
7d8d08c4
JH
802caching for successful lookups.
803*/
059ec3d9 804
7d8d08c4 805if ((rc = dns_fail_cache_hit(name, type)) > 0)
979c462e
JH
806 {
807 dnsa->answerlen = -1;
7d8d08c4 808 return rc;
979c462e 809 }
059ec3d9 810
8c5d388a 811#ifdef SUPPORT_I18N
9d4319df
JH
812/* Convert all names to a-label form before doing lookup */
813 {
814 uschar * alabel;
815 uschar * errstr = NULL;
766e7a65
JH
816 DEBUG(D_dns) if (string_is_utf8(name))
817 debug_printf("convert utf8 '%s' to alabel for for lookup\n", name);
9d4319df
JH
818 if ((alabel = string_domain_utf8_to_alabel(name, &errstr)), errstr)
819 {
820 DEBUG(D_dns)
37bf366e 821 debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
9d4319df 822 errstr);
8768d548 823 f.host_find_failed_syntax = TRUE;
9d4319df
JH
824 return DNS_NOMATCH;
825 }
826 name = alabel;
827 }
828#endif
829
4c04137d 830/* If configured, check the hygiene of the name passed to lookup. Otherwise,
059ec3d9
PH
831although DNS lookups may give REFUSED at the lower level, some resolvers
832turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
833domains cannot be in the DNS. The check is now done by a regular expression;
834give it space for substring storage to save it having to get its own if the
835regex has substrings that are used - the default uses a conditional.
836
837This test is omitted for PTR records. These occur only in calls from the dnsdb
838lookup, which constructs the names itself, so they should be OK. Besides,
6219e0ec
SA
839bitstring labels don't conform to normal name syntax. (But they aren't used any
840more.) */
059ec3d9
PH
841
842#ifndef STAND_ALONE /* Omit this for stand-alone tests */
843
482d1455 844if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)
059ec3d9 845 {
059ec3d9
PH
846 int ovector[3*(EXPAND_MAXN+1)];
847
476be7e2 848 dns_pattern_init();
6219e0ec 849 if (pcre_exec(regex_check_dns_names, NULL, CCS name, Ustrlen(name),
d093f8e5 850 0, PCRE_EOPT, ovector, nelem(ovector)) < 0)
059ec3d9
PH
851 {
852 DEBUG(D_dns)
853 debug_printf("DNS name syntax check failed: %s (%s)\n", name,
854 dns_text_type(type));
8768d548 855 f.host_find_failed_syntax = TRUE;
059ec3d9
PH
856 return DNS_NOMATCH;
857 }
858 }
859
860#endif /* STAND_ALONE */
861
862/* Call the resolver; for an overlong response, res_search() will return the
bef5a11f
PH
863number of bytes the message would need, so we need to check for this case. The
864effect is to truncate overlong data.
865
30e18802
PH
866On some systems, res_search() will recognize "A-for-A" queries and return
867the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some
868nameservers are also believed to do this. It is, of course, contrary to the
869specification of the DNS, so we lock it out. */
870
cc00f4af 871if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0)
30e18802
PH
872 return DNS_NOMATCH;
873
874/* If we are running in the test harness, instead of calling the normal resolver
bef5a11f
PH
875(res_search), we call fakens_search(), which recognizes certain special
876domains, and interfaces to a fake nameserver for certain special zones. */
877
979c462e 878h_errno = 0;
8768d548 879dnsa->answerlen = f.running_in_test_harness
d093f8e5
JH
880 ? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer))
881 : res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer));
059ec3d9 882
d093f8e5 883if (dnsa->answerlen > (int) sizeof(dnsa->answer))
80a47a2c 884 {
9e7e0f6a
JH
885 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet"
886 " (size %d), truncating to %u.\n",
887 name, dns_text_type(type), dnsa->answerlen, (unsigned int) sizeof(dnsa->answer));
d093f8e5 888 dnsa->answerlen = sizeof(dnsa->answer);
80a47a2c 889 }
059ec3d9
PH
890
891if (dnsa->answerlen < 0) switch (h_errno)
892 {
893 case HOST_NOT_FOUND:
4b0fe319
JH
894 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n"
895 "returning DNS_NOMATCH\n", name, dns_text_type(type));
a713f766 896 return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH);
059ec3d9
PH
897
898 case TRY_AGAIN:
4b0fe319
JH
899 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
900 name, dns_text_type(type));
059ec3d9 901
4b0fe319 902 /* Cut this out for various test programs */
1dc92d5a 903#ifndef STAND_ALONE
4b0fe319
JH
904 save_domain = deliver_domain;
905 deliver_domain = string_copy(name); /* set $domain */
906 rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
907 MCL_DOMAIN, TRUE, NULL);
908 deliver_domain = save_domain;
909 if (rc != OK)
910 {
911 DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
7d8d08c4 912 return dns_fail_return(name, type, 0, DNS_AGAIN);
4b0fe319
JH
913 }
914 DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
915 "DNS_NOMATCH\n", name);
a713f766 916 return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH);
059ec3d9 917
1dc92d5a 918#else /* For stand-alone tests */
7d8d08c4 919 return dns_fail_return(name, type, 0, DNS_AGAIN);
1dc92d5a 920#endif
059ec3d9
PH
921
922 case NO_RECOVERY:
4b0fe319
JH
923 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
924 "returning DNS_FAIL\n", name, dns_text_type(type));
7d8d08c4 925 return dns_fail_return(name, type, 0, DNS_FAIL);
059ec3d9
PH
926
927 case NO_DATA:
4b0fe319
JH
928 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n"
929 "returning DNS_NODATA\n", name, dns_text_type(type));
a713f766 930 return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NODATA);
059ec3d9
PH
931
932 default:
4b0fe319
JH
933 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
934 "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
7d8d08c4 935 return dns_fail_return(name, type, 0, DNS_FAIL);
059ec3d9
PH
936 }
937
938DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n",
939 name, dns_text_type(type));
940
941return DNS_SUCCEED;
942}
943
944
945
946
947/************************************************
948* Do a DNS lookup and handle CNAMES *
949************************************************/
950
951/* Look up the given domain name, using the given type. Follow CNAMEs if
952necessary, but only so many times. There aren't supposed to be CNAME chains in
953the DNS, but you are supposed to cope with them if you find them.
d8d9f930
JH
954By default, follow one CNAME since a resolver has been seen, faced with
955an MX request and a CNAME (to an A) but no MX present, returning the CNAME.
059ec3d9
PH
956
957The assumption is made that if the resolver gives back records of the
958requested type *and* a CNAME, we don't need to make another call to look up
959the CNAME. I can't see how it could return only some of the right records. If
960it's done a CNAME lookup in the past, it will have all of them; if not, it
961won't return any.
962
963If fully_qualified_name is not NULL, set it to point to the full name
964returned by the resolver, if this is different to what it is given, unless
965the returned name starts with "*" as some nameservers seem to be returning
766e7a65
JH
966wildcards in this form. In international mode "different" means "alabel
967forms are different".
059ec3d9
PH
968
969Arguments:
970 dnsa pointer to dns_answer structure
971 name domain name to look up
972 type DNS record type (T_A, T_MX, etc)
973 fully_qualified_name if not NULL, return the returned name here if its
974 contents are different (i.e. it must be preset)
975
976Returns: DNS_SUCCEED successful lookup
977 DNS_NOMATCH name not found
978 DNS_NODATA no data found
979 DNS_AGAIN soft failure, try again later
980 DNS_FAIL DNS failure
981*/
982
983int
1dc92d5a 984dns_lookup(dns_answer *dnsa, const uschar *name, int type,
55414b25 985 const uschar **fully_qualified_name)
059ec3d9 986{
1dc92d5a 987const uschar *orig_name = name;
c85b3043 988BOOL secure_so_far = TRUE;
059ec3d9 989
d8d9f930
JH
990/* By default, assume the resolver follows CNAME chains (and returns NODATA for
991an unterminated one). If it also does that for a CNAME loop, fine; if it returns
992a CNAME (maybe the last?) whine about it. However, retain the coding for dumb
993resolvers hiding behind a config variable. Loop to follow CNAME chains so far,
994but no further... The testsuite tests the latter case, mostly assuming that the
995former will work. */
059ec3d9 996
d7978c0f 997for (int i = 0; i <= dns_cname_loops; i++)
059ec3d9 998 {
806c3df9 999 uschar * data;
d7978c0f 1000 dns_record cname_rr, type_rr;
059ec3d9 1001 dns_scan dnss;
1b76ad22 1002 int rc;
059ec3d9
PH
1003
1004 /* DNS lookup failures get passed straight back. */
1005
dd708fd7
JH
1006 if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED)
1007 return rc;
059ec3d9
PH
1008
1009 /* We should have either records of the required type, or a CNAME record,
1010 or both. We need to know whether both exist for getting the fully qualified
1011 name, but avoid scanning more than necessary. Note that we must copy the
1012 contents of any rr blocks returned by dns_next_rr() as they use the same
1013 area in the dnsa block. */
1014
1015 cname_rr.data = type_rr.data = NULL;
d7978c0f 1016 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
8688d177 1017 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
059ec3d9
PH
1018 if (rr->type == type)
1019 {
1020 if (type_rr.data == NULL) type_rr = *rr;
1021 if (cname_rr.data != NULL) break;
1022 }
dd708fd7
JH
1023 else if (rr->type == T_CNAME)
1024 cname_rr = *rr;
059ec3d9 1025
a2042e78
PH
1026 /* For the first time round this loop, if a CNAME was found, take the fully
1027 qualified name from it; otherwise from the first data record, if present. */
059ec3d9 1028
dd708fd7 1029 if (i == 0 && fully_qualified_name)
059ec3d9 1030 {
dd708fd7
JH
1031 uschar * rr_name = cname_rr.data
1032 ? cname_rr.name : type_rr.data ? type_rr.name : NULL;
766e7a65
JH
1033 if ( rr_name
1034 && Ustrcmp(rr_name, *fully_qualified_name) != 0
1035 && rr_name[0] != '*'
8c5d388a 1036#ifdef SUPPORT_I18N
766e7a65
JH
1037 && ( !string_is_utf8(*fully_qualified_name)
1038 || Ustrcmp(rr_name,
1039 string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0
1040 )
1041#endif
1042 )
1043 *fully_qualified_name = string_copy_dnsdomain(rr_name);
059ec3d9
PH
1044 }
1045
1046 /* If any data records of the correct type were found, we are done. */
1047
806c3df9 1048 if (type_rr.data)
c85b3043
JH
1049 {
1050 if (!secure_so_far) /* mark insecure if any element of CNAME chain was */
4a142059 1051 dns_set_insecure(dnsa);
c85b3043
JH
1052 return DNS_SUCCEED;
1053 }
059ec3d9
PH
1054
1055 /* If there are no data records, we need to re-scan the DNS using the
1056 domain given in the CNAME record, which should exist (otherwise we should
1057 have had a failure from dns_lookup). However code against the possibility of
1058 its not existing. */
1059
806c3df9
JH
1060 if (!cname_rr.data)
1061 return DNS_FAIL;
1062
f3ebb786
JH
1063 /* DNS data comes from the outside, hence tainted */
1064 data = store_get(256, TRUE);
1b76ad22
JH
1065 if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
1066 cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
806c3df9 1067 return DNS_FAIL;
059ec3d9 1068 name = data;
a2042e78 1069
c85b3043
JH
1070 if (!dns_is_secure(dnsa))
1071 secure_so_far = FALSE;
1072
a2042e78 1073 DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name);
059ec3d9
PH
1074 } /* Loop back to do another lookup */
1075
1076/*Control reaches here after 10 times round the CNAME loop. Something isn't
1077right... */
1078
1079log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name);
1080return DNS_FAIL;
1081}
1082
1083
1084
33397d19
PH
1085
1086
1087
1088/************************************************
1089* Do a DNS lookup and handle virtual types *
1090************************************************/
1091
9820a77f 1092/* This function handles some invented "lookup types" that synthesize features
8e669ac1 1093not available in the basic types. The special types all have negative values.
33397d19
PH
1094Positive type values are passed straight on to dns_lookup().
1095
1096Arguments:
1097 dnsa pointer to dns_answer structure
1098 name domain name to look up
1099 type DNS record type (T_A, T_MX, etc or a "special")
1100 fully_qualified_name if not NULL, return the returned name here if its
1101 contents are different (i.e. it must be preset)
1102
1103Returns: DNS_SUCCEED successful lookup
1104 DNS_NOMATCH name not found
1105 DNS_NODATA no data found
1106 DNS_AGAIN soft failure, try again later
1107 DNS_FAIL DNS failure
1108*/
1109
1110int
1dc92d5a 1111dns_special_lookup(dns_answer *dnsa, const uschar *name, int type,
55414b25 1112 const uschar **fully_qualified_name)
33397d19 1113{
d2a2c69b 1114switch (type)
e5a9dba6 1115 {
d2a2c69b
JH
1116 /* The "mx hosts only" type doesn't require any special action here */
1117 case T_MXH:
1705dd20 1118 return dns_lookup(dnsa, name, T_MX, fully_qualified_name);
d2a2c69b
JH
1119
1120 /* Find nameservers for the domain or the nearest enclosing zone, excluding
1121 the root servers. */
1122 case T_ZNS:
1705dd20
JH
1123 type = T_NS;
1124 /* FALLTHROUGH */
d2a2c69b 1125 case T_SOA:
1705dd20
JH
1126 {
1127 const uschar *d = name;
1128 while (d != 0)
1129 {
1130 int rc = dns_lookup(dnsa, d, type, fully_qualified_name);
1131 if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
1132 while (*d != 0 && *d != '.') d++;
1133 if (*d++ == 0) break;
1134 }
1135 return DNS_NOMATCH;
1136 }
d2a2c69b
JH
1137
1138 /* Try to look up the Client SMTP Authorization SRV record for the name. If
1139 there isn't one, search from the top downwards for a CSA record in a parent
1140 domain, which might be making assertions about subdomains. If we find a record
1141 we set fully_qualified_name to whichever lookup succeeded, so that the caller
1142 can tell whether to look at the explicit authorization field or the subdomain
1143 assertion field. */
1144 case T_CSA:
1705dd20 1145 {
cab0c277 1146 uschar *srvname, *namesuff, *tld;
1705dd20
JH
1147 int priority, weight, port;
1148 int limit, rc, i;
1149 BOOL ipv6;
1150 dns_record *rr;
1151 dns_scan dnss;
1152
1153 DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
1154
1155 srvname = string_sprintf("_client._smtp.%s", name);
1156 rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
1157 if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
1158 {
1159 if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
1160 return rc;
1161 }
d2a2c69b 1162
1705dd20
JH
1163 /* Search for CSA subdomain assertion SRV records from the top downwards,
1164 starting with the 2nd level domain. This order maximizes cache-friendliness.
1165 We skip the top level domains to avoid loading their nameservers and because
1166 we know they'll never have CSA SRV records. */
d2a2c69b 1167
1705dd20
JH
1168 namesuff = Ustrrchr(name, '.');
1169 if (namesuff == NULL) return DNS_NOMATCH;
1170 tld = namesuff + 1;
1171 ipv6 = FALSE;
1172 limit = dns_csa_search_limit;
1173
1174 /* Use more appropriate search parameters if we are in the reverse DNS. */
1175
1176 if (strcmpic(namesuff, US".arpa") == 0)
1177 if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
1178 {
1179 namesuff -= 8;
d2a2c69b 1180 tld = namesuff + 1;
1705dd20
JH
1181 limit = 3;
1182 }
1183 else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
1184 {
1185 namesuff -= 4;
1186 tld = namesuff + 1;
1187 ipv6 = TRUE;
1188 limit = 3;
1189 }
d2a2c69b 1190
1705dd20 1191 DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);
d2a2c69b 1192
1705dd20
JH
1193 /* Do not perform the search if the top level or 2nd level domains do not
1194 exist. This is quite common, and when it occurs all the search queries would
1195 go to the root or TLD name servers, which is not friendly. So we check the
1196 AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
1197 the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
1198 If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
1199 the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */
1200
1201 if (rc == DNS_NOMATCH)
1202 {
a713f766 1203 fake_dnsa_len_for_fail(dnsa, T_CSA);
1705dd20
JH
1204
1205 for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
8688d177 1206 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
1705dd20
JH
1207 )
1208 if (rr->type != T_SOA) continue;
1209 else if (strcmpic(rr->name, US"") == 0 ||
1210 strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
1211 else break;
1212 }
d2a2c69b 1213
1705dd20
JH
1214 for (i = 0; i < limit; i++)
1215 {
1216 if (ipv6)
1217 {
1218 /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
1219 address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
1220 namesuff -= 8;
1221 if (namesuff <= name) return DNS_NOMATCH;
1222 }
1223 else
1224 /* Find the start of the preceding domain name label. */
1225 do
1226 if (--namesuff <= name) return DNS_NOMATCH;
1227 while (*namesuff != '.');
1228
1229 DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);
1230
1231 srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
1232 rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
1233 if (rc == DNS_AGAIN) return rc;
1234 if (rc != DNS_SUCCEED) continue;
1235
1236 /* Check that the SRV record we have found is worth returning. We don't
1237 just return the first one we find, because some lower level SRV record
1238 might make stricter assertions than its parent domain. */
1239
1240 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
8688d177 1241 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == T_SRV)
1705dd20 1242 {
dd708fd7 1243 const uschar * p = rr->data;
d2a2c69b 1244
1705dd20 1245 /* Extract the numerical SRV fields (p is incremented) */
1705dd20
JH
1246 GETSHORT(priority, p);
1247 GETSHORT(weight, p); weight = weight; /* compiler quietening */
1248 GETSHORT(port, p);
d2a2c69b 1249
1705dd20
JH
1250 /* Check the CSA version number */
1251 if (priority != 1) continue;
d2a2c69b 1252
1705dd20
JH
1253 /* If it's making an interesting assertion, return this response. */
1254 if (port & 1)
d2a2c69b 1255 {
1705dd20
JH
1256 *fully_qualified_name = namesuff + 1;
1257 return DNS_SUCCEED;
d2a2c69b 1258 }
d2a2c69b 1259 }
1705dd20
JH
1260 }
1261 return DNS_NOMATCH;
1262 }
e5a9dba6 1263
d2a2c69b 1264 default:
1705dd20
JH
1265 if (type >= 0)
1266 return dns_lookup(dnsa, name, type, fully_qualified_name);
e5a9dba6
PH
1267 }
1268
33397d19
PH
1269/* Control should never reach here */
1270
1271return DNS_FAIL;
1272}
1273
1274
1275
059ec3d9
PH
1276
1277
1278/*************************************************
1279* Get address(es) from DNS record *
1280*************************************************/
1281
d57d474f 1282/* The record type is either T_A for an IPv4 address or T_AAAA for an IPv6 address.
059ec3d9
PH
1283
1284Argument:
1285 dnsa the DNS answer block
1286 rr the RR
1287
e1a3f32f 1288Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun
059ec3d9
PH
1289*/
1290
1291dns_address *
1292dns_address_from_rr(dns_answer *dnsa, dns_record *rr)
1293{
e1a3f32f
JH
1294dns_address * yield = NULL;
1295uschar * dnsa_lim = dnsa->answer + dnsa->answerlen;
059ec3d9
PH
1296
1297if (rr->type == T_A)
1298 {
d2a2c69b 1299 uschar *p = US rr->data;
e1a3f32f
JH
1300 if (p + 4 <= dnsa_lim)
1301 {
f3ebb786
JH
1302 /* the IP is not regarded as tainted */
1303 yield = store_get(sizeof(dns_address) + 20, FALSE);
e1a3f32f
JH
1304 (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
1305 yield->next = NULL;
1306 }
059ec3d9
PH
1307 }
1308
1309#if HAVE_IPV6
1310
059ec3d9
PH
1311else
1312 {
e1a3f32f
JH
1313 if (rr->data + 16 <= dnsa_lim)
1314 {
d57d474f 1315 struct in6_addr in6;
d7978c0f 1316 for (int i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];
f3ebb786 1317 yield = store_get(sizeof(dns_address) + 50, FALSE);
d57d474f 1318 inet_ntop(AF_INET6, &in6, CS yield->address, 50);
e1a3f32f
JH
1319 yield->next = NULL;
1320 }
059ec3d9
PH
1321 }
1322#endif /* HAVE_IPV6 */
1323
1324return yield;
1325}
1326
476be7e2
JH
1327
1328
1329void
1330dns_pattern_init(void)
1331{
1332if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names)
1333 regex_check_dns_names =
1334 regex_must_compile(check_dns_names_pattern, FALSE, TRUE);
1335}
1336
8c51eead
JH
1337/* vi: aw ai sw=2
1338*/
059ec3d9 1339/* End of dns.c */