Fix local-scan ABI. Bug 2458
[exim.git] / src / src / dns.c
CommitLineData
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1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4
f9ba5e22 5/* Copyright (c) University of Cambridge 1995 - 2018 */
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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
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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
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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.
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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.
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27
28Arguments:
e7726cbf 29 domain the domain name
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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;
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43uschar utilname[256];
44uschar *aptr = answerptr; /* Locally modified */
45struct stat statbuf;
46
47/* Remove terminating dot. */
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48
49if (domain[len - 1] == '.') len--;
f3ebb786 50name = string_copyn(domain, len);
bef5a11f 51
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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);
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56
57if (stat(CS utilname, &statbuf) >= 0)
bef5a11f 58 {
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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));
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64
65 argv[0] = utilname;
5f3d0983 66 argv[1] = config_main_directory;
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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
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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 {
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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");
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106 }
107 }
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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);
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116
117return res_search(CS domain, C_IN, type, answerptr, size);
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118}
119
120
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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
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133
134Returns: nothing
135*/
136
137void
8c51eead 138dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec)
059ec3d9 139{
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PP
140res_state resp = os_get_dns_resolver_res();
141
142if ((resp->options & RES_INIT) == 0)
059ec3d9 143 {
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144 DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */
145 os_put_dns_resolver_res(resp);
059ec3d9 146 res_init();
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147 DEBUG(D_resolver) resp->options |= RES_DEBUG;
148 os_put_dns_resolver_res(resp);
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149 }
150
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151resp->options &= ~(RES_DNSRCH | RES_DEFNAMES);
152resp->options |= (qualify_single? RES_DEFNAMES : 0) |
059ec3d9 153 (search_parents? RES_DNSRCH : 0);
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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;
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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
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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)
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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)
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PP
201 DEBUG(D_resolver)
202 debug_printf("Unable to %sset DNSSEC without resolver support.\n",
0fbd9bff 203 dns_dnssec_ok ? "" : "un");
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204if (use_dnssec)
205 DEBUG(D_resolver)
93d4b03a 206 debug_printf("Unable to set DNSSEC without resolver support.\n");
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207# endif
208#endif /* DISABLE_DNSSEC */
209
5bfb4cdf 210os_put_dns_resolver_res(resp);
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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);
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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;
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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
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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
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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.");
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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.");
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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
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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
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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.
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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
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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
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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
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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
684/* Return the TTL suitable for an NXDOMAIN result, which is given
685in the SOA. We hope that one was returned in the lookup, and do not
686bother doing a separate lookup; if not found return a forever TTL.
687*/
688
3462da30 689time_t
7d8d08c4
JH
690dns_expire_from_soa(dns_answer * dnsa)
691{
692const HEADER * h = (const HEADER *)dnsa->answer;
693dns_scan dnss;
694
695/* This is really gross. The successful return value from res_search() is
696the packet length, which is stored in dnsa->answerlen. If we get a
697negative DNS reply then res_search() returns -1, which causes the bounds
698checks for name decompression to fail when it is treated as a packet
699length, which in turn causes the authority search to fail. The correct
700packet length has been lost inside libresolv, so we have to guess a
701replacement value. (The only way to fix this properly would be to
702re-implement res_search() and res_query() so that they don't muddle their
703success and packet length return values.) For added safety we only reset
704the packet length if the packet header looks plausible. */
705
706if ( h->qr == 1 && h->opcode == QUERY && h->tc == 0
707 && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
708 && (ntohs(h->qdcount) == 1 || f.running_in_test_harness)
709 && ntohs(h->ancount) == 0
710 && ntohs(h->nscount) >= 1)
711 dnsa->answerlen = sizeof(dnsa->answer);
712
713for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
714 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
715 ) if (rr->type == T_SOA)
716 {
717 const uschar * p = rr->data;
718 uschar discard_buf[256];
719 int len;
720 unsigned long ttl;
721
722 /* Skip the mname & rname strings */
723
724 if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
725 p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
726 break;
727 p += len;
728 if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
729 p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
730 break;
731 p += len;
732
733 /* Skip the SOA serial, refresh, retry & expire. Grab the TTL */
734
d70fc283 735 if (p > dnsa->answer + dnsa->answerlen - 5 * INT32SZ)
7d8d08c4 736 break;
d70fc283 737 p += 4 * INT32SZ;
7d8d08c4
JH
738 GETLONG(ttl, p);
739
740 return time(NULL) + ttl;
741 }
742DEBUG(D_dns) debug_printf("DNS: no SOA record found for neg-TTL\n");
743return 0;
744}
745
746
059ec3d9
PH
747/*************************************************
748* Do basic DNS lookup *
749*************************************************/
750
751/* Call the resolver to look up the given domain name, using the given type,
752and check the result. The error code TRY_AGAIN is documented as meaning "non-
4c04137d 753Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set
059ec3d9
PH
754up nameservers that produce this error continually, so there is the option of
755providing a list of domains for which this is treated as a non-existent
756host.
757
75c121f0
JH
758The dns_answer structure is pretty big; enough to hold a max-sized DNS message
759- so best allocated from fast-release memory. As of writing, all our callers
760use a stack-auto variable.
761
059ec3d9
PH
762Arguments:
763 dnsa pointer to dns_answer structure
764 name name to look up
765 type type of DNS record required (T_A, T_MX, etc)
766
767Returns: DNS_SUCCEED successful lookup
768 DNS_NOMATCH name not found (NXDOMAIN)
769 or name contains illegal characters (if checking)
30e18802 770 or name is an IP address (for IP address lookup)
059ec3d9
PH
771 DNS_NODATA domain exists, but no data for this type (NODATA)
772 DNS_AGAIN soft failure, try again later
773 DNS_FAIL DNS failure
774*/
775
776int
7d8d08c4 777dns_basic_lookup(dns_answer * dnsa, const uschar * name, int type)
059ec3d9 778{
7d8d08c4 779int rc;
059ec3d9 780#ifndef STAND_ALONE
7d8d08c4 781const uschar * save_domain;
059ec3d9
PH
782#endif
783
059ec3d9
PH
784/* DNS lookup failures of any kind are cached in a tree. This is mainly so that
785a timeout on one domain doesn't happen time and time again for messages that
786have many addresses in the same domain. We rely on the resolver and name server
7d8d08c4
JH
787caching for successful lookups.
788*/
059ec3d9 789
7d8d08c4 790if ((rc = dns_fail_cache_hit(name, type)) > 0)
979c462e
JH
791 {
792 dnsa->answerlen = -1;
7d8d08c4 793 return rc;
979c462e 794 }
059ec3d9 795
8c5d388a 796#ifdef SUPPORT_I18N
9d4319df
JH
797/* Convert all names to a-label form before doing lookup */
798 {
799 uschar * alabel;
800 uschar * errstr = NULL;
766e7a65
JH
801 DEBUG(D_dns) if (string_is_utf8(name))
802 debug_printf("convert utf8 '%s' to alabel for for lookup\n", name);
9d4319df
JH
803 if ((alabel = string_domain_utf8_to_alabel(name, &errstr)), errstr)
804 {
805 DEBUG(D_dns)
37bf366e 806 debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
9d4319df 807 errstr);
8768d548 808 f.host_find_failed_syntax = TRUE;
9d4319df
JH
809 return DNS_NOMATCH;
810 }
811 name = alabel;
812 }
813#endif
814
4c04137d 815/* If configured, check the hygiene of the name passed to lookup. Otherwise,
059ec3d9
PH
816although DNS lookups may give REFUSED at the lower level, some resolvers
817turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
818domains cannot be in the DNS. The check is now done by a regular expression;
819give it space for substring storage to save it having to get its own if the
820regex has substrings that are used - the default uses a conditional.
821
822This test is omitted for PTR records. These occur only in calls from the dnsdb
823lookup, which constructs the names itself, so they should be OK. Besides,
6219e0ec
SA
824bitstring labels don't conform to normal name syntax. (But they aren't used any
825more.) */
059ec3d9
PH
826
827#ifndef STAND_ALONE /* Omit this for stand-alone tests */
828
482d1455 829if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)
059ec3d9 830 {
059ec3d9
PH
831 int ovector[3*(EXPAND_MAXN+1)];
832
476be7e2 833 dns_pattern_init();
6219e0ec 834 if (pcre_exec(regex_check_dns_names, NULL, CCS name, Ustrlen(name),
d093f8e5 835 0, PCRE_EOPT, ovector, nelem(ovector)) < 0)
059ec3d9
PH
836 {
837 DEBUG(D_dns)
838 debug_printf("DNS name syntax check failed: %s (%s)\n", name,
839 dns_text_type(type));
8768d548 840 f.host_find_failed_syntax = TRUE;
059ec3d9
PH
841 return DNS_NOMATCH;
842 }
843 }
844
845#endif /* STAND_ALONE */
846
847/* Call the resolver; for an overlong response, res_search() will return the
bef5a11f
PH
848number of bytes the message would need, so we need to check for this case. The
849effect is to truncate overlong data.
850
30e18802
PH
851On some systems, res_search() will recognize "A-for-A" queries and return
852the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some
853nameservers are also believed to do this. It is, of course, contrary to the
854specification of the DNS, so we lock it out. */
855
cc00f4af 856if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0)
30e18802
PH
857 return DNS_NOMATCH;
858
859/* If we are running in the test harness, instead of calling the normal resolver
bef5a11f
PH
860(res_search), we call fakens_search(), which recognizes certain special
861domains, and interfaces to a fake nameserver for certain special zones. */
862
979c462e 863h_errno = 0;
8768d548 864dnsa->answerlen = f.running_in_test_harness
d093f8e5
JH
865 ? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer))
866 : res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer));
059ec3d9 867
d093f8e5 868if (dnsa->answerlen > (int) sizeof(dnsa->answer))
80a47a2c 869 {
9e7e0f6a
JH
870 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet"
871 " (size %d), truncating to %u.\n",
872 name, dns_text_type(type), dnsa->answerlen, (unsigned int) sizeof(dnsa->answer));
d093f8e5 873 dnsa->answerlen = sizeof(dnsa->answer);
80a47a2c 874 }
059ec3d9
PH
875
876if (dnsa->answerlen < 0) switch (h_errno)
877 {
878 case HOST_NOT_FOUND:
4b0fe319
JH
879 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n"
880 "returning DNS_NOMATCH\n", name, dns_text_type(type));
7d8d08c4 881 return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NOMATCH);
059ec3d9
PH
882
883 case TRY_AGAIN:
4b0fe319
JH
884 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
885 name, dns_text_type(type));
059ec3d9 886
4b0fe319 887 /* Cut this out for various test programs */
1dc92d5a 888#ifndef STAND_ALONE
4b0fe319
JH
889 save_domain = deliver_domain;
890 deliver_domain = string_copy(name); /* set $domain */
891 rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
892 MCL_DOMAIN, TRUE, NULL);
893 deliver_domain = save_domain;
894 if (rc != OK)
895 {
896 DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
7d8d08c4 897 return dns_fail_return(name, type, 0, DNS_AGAIN);
4b0fe319
JH
898 }
899 DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
900 "DNS_NOMATCH\n", name);
7d8d08c4 901 return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NOMATCH);
059ec3d9 902
1dc92d5a 903#else /* For stand-alone tests */
7d8d08c4 904 return dns_fail_return(name, type, 0, DNS_AGAIN);
1dc92d5a 905#endif
059ec3d9
PH
906
907 case NO_RECOVERY:
4b0fe319
JH
908 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
909 "returning DNS_FAIL\n", name, dns_text_type(type));
7d8d08c4 910 return dns_fail_return(name, type, 0, DNS_FAIL);
059ec3d9
PH
911
912 case NO_DATA:
4b0fe319
JH
913 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n"
914 "returning DNS_NODATA\n", name, dns_text_type(type));
7d8d08c4 915 return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NODATA);
059ec3d9
PH
916
917 default:
4b0fe319
JH
918 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
919 "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
7d8d08c4 920 return dns_fail_return(name, type, 0, DNS_FAIL);
059ec3d9
PH
921 }
922
923DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n",
924 name, dns_text_type(type));
925
926return DNS_SUCCEED;
927}
928
929
930
931
932/************************************************
933* Do a DNS lookup and handle CNAMES *
934************************************************/
935
936/* Look up the given domain name, using the given type. Follow CNAMEs if
937necessary, but only so many times. There aren't supposed to be CNAME chains in
938the DNS, but you are supposed to cope with them if you find them.
d8d9f930
JH
939By default, follow one CNAME since a resolver has been seen, faced with
940an MX request and a CNAME (to an A) but no MX present, returning the CNAME.
059ec3d9
PH
941
942The assumption is made that if the resolver gives back records of the
943requested type *and* a CNAME, we don't need to make another call to look up
944the CNAME. I can't see how it could return only some of the right records. If
945it's done a CNAME lookup in the past, it will have all of them; if not, it
946won't return any.
947
948If fully_qualified_name is not NULL, set it to point to the full name
949returned by the resolver, if this is different to what it is given, unless
950the returned name starts with "*" as some nameservers seem to be returning
766e7a65
JH
951wildcards in this form. In international mode "different" means "alabel
952forms are different".
059ec3d9
PH
953
954Arguments:
955 dnsa pointer to dns_answer structure
956 name domain name to look up
957 type DNS record type (T_A, T_MX, etc)
958 fully_qualified_name if not NULL, return the returned name here if its
959 contents are different (i.e. it must be preset)
960
961Returns: DNS_SUCCEED successful lookup
962 DNS_NOMATCH name not found
963 DNS_NODATA no data found
964 DNS_AGAIN soft failure, try again later
965 DNS_FAIL DNS failure
966*/
967
968int
1dc92d5a 969dns_lookup(dns_answer *dnsa, const uschar *name, int type,
55414b25 970 const uschar **fully_qualified_name)
059ec3d9 971{
1dc92d5a 972const uschar *orig_name = name;
c85b3043 973BOOL secure_so_far = TRUE;
059ec3d9 974
d8d9f930
JH
975/* By default, assume the resolver follows CNAME chains (and returns NODATA for
976an unterminated one). If it also does that for a CNAME loop, fine; if it returns
977a CNAME (maybe the last?) whine about it. However, retain the coding for dumb
978resolvers hiding behind a config variable. Loop to follow CNAME chains so far,
979but no further... The testsuite tests the latter case, mostly assuming that the
980former will work. */
059ec3d9 981
d7978c0f 982for (int i = 0; i <= dns_cname_loops; i++)
059ec3d9 983 {
806c3df9 984 uschar * data;
d7978c0f 985 dns_record cname_rr, type_rr;
059ec3d9 986 dns_scan dnss;
1b76ad22 987 int rc;
059ec3d9
PH
988
989 /* DNS lookup failures get passed straight back. */
990
dd708fd7
JH
991 if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED)
992 return rc;
059ec3d9
PH
993
994 /* We should have either records of the required type, or a CNAME record,
995 or both. We need to know whether both exist for getting the fully qualified
996 name, but avoid scanning more than necessary. Note that we must copy the
997 contents of any rr blocks returned by dns_next_rr() as they use the same
998 area in the dnsa block. */
999
1000 cname_rr.data = type_rr.data = NULL;
d7978c0f 1001 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
8688d177 1002 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
059ec3d9
PH
1003 if (rr->type == type)
1004 {
1005 if (type_rr.data == NULL) type_rr = *rr;
1006 if (cname_rr.data != NULL) break;
1007 }
dd708fd7
JH
1008 else if (rr->type == T_CNAME)
1009 cname_rr = *rr;
059ec3d9 1010
a2042e78
PH
1011 /* For the first time round this loop, if a CNAME was found, take the fully
1012 qualified name from it; otherwise from the first data record, if present. */
059ec3d9 1013
dd708fd7 1014 if (i == 0 && fully_qualified_name)
059ec3d9 1015 {
dd708fd7
JH
1016 uschar * rr_name = cname_rr.data
1017 ? cname_rr.name : type_rr.data ? type_rr.name : NULL;
766e7a65
JH
1018 if ( rr_name
1019 && Ustrcmp(rr_name, *fully_qualified_name) != 0
1020 && rr_name[0] != '*'
8c5d388a 1021#ifdef SUPPORT_I18N
766e7a65
JH
1022 && ( !string_is_utf8(*fully_qualified_name)
1023 || Ustrcmp(rr_name,
1024 string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0
1025 )
1026#endif
1027 )
1028 *fully_qualified_name = string_copy_dnsdomain(rr_name);
059ec3d9
PH
1029 }
1030
1031 /* If any data records of the correct type were found, we are done. */
1032
806c3df9 1033 if (type_rr.data)
c85b3043
JH
1034 {
1035 if (!secure_so_far) /* mark insecure if any element of CNAME chain was */
4a142059 1036 dns_set_insecure(dnsa);
c85b3043
JH
1037 return DNS_SUCCEED;
1038 }
059ec3d9
PH
1039
1040 /* If there are no data records, we need to re-scan the DNS using the
1041 domain given in the CNAME record, which should exist (otherwise we should
1042 have had a failure from dns_lookup). However code against the possibility of
1043 its not existing. */
1044
806c3df9
JH
1045 if (!cname_rr.data)
1046 return DNS_FAIL;
1047
f3ebb786
JH
1048 /* DNS data comes from the outside, hence tainted */
1049 data = store_get(256, TRUE);
1b76ad22
JH
1050 if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
1051 cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
806c3df9 1052 return DNS_FAIL;
059ec3d9 1053 name = data;
a2042e78 1054
c85b3043
JH
1055 if (!dns_is_secure(dnsa))
1056 secure_so_far = FALSE;
1057
a2042e78 1058 DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name);
059ec3d9
PH
1059 } /* Loop back to do another lookup */
1060
1061/*Control reaches here after 10 times round the CNAME loop. Something isn't
1062right... */
1063
1064log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name);
1065return DNS_FAIL;
1066}
1067
1068
1069
33397d19
PH
1070
1071
1072
1073/************************************************
1074* Do a DNS lookup and handle virtual types *
1075************************************************/
1076
9820a77f 1077/* This function handles some invented "lookup types" that synthesize features
8e669ac1 1078not available in the basic types. The special types all have negative values.
33397d19
PH
1079Positive type values are passed straight on to dns_lookup().
1080
1081Arguments:
1082 dnsa pointer to dns_answer structure
1083 name domain name to look up
1084 type DNS record type (T_A, T_MX, etc or a "special")
1085 fully_qualified_name if not NULL, return the returned name here if its
1086 contents are different (i.e. it must be preset)
1087
1088Returns: DNS_SUCCEED successful lookup
1089 DNS_NOMATCH name not found
1090 DNS_NODATA no data found
1091 DNS_AGAIN soft failure, try again later
1092 DNS_FAIL DNS failure
1093*/
1094
1095int
1dc92d5a 1096dns_special_lookup(dns_answer *dnsa, const uschar *name, int type,
55414b25 1097 const uschar **fully_qualified_name)
33397d19 1098{
d2a2c69b 1099switch (type)
e5a9dba6 1100 {
d2a2c69b
JH
1101 /* The "mx hosts only" type doesn't require any special action here */
1102 case T_MXH:
1705dd20 1103 return dns_lookup(dnsa, name, T_MX, fully_qualified_name);
d2a2c69b
JH
1104
1105 /* Find nameservers for the domain or the nearest enclosing zone, excluding
1106 the root servers. */
1107 case T_ZNS:
1705dd20
JH
1108 type = T_NS;
1109 /* FALLTHROUGH */
d2a2c69b 1110 case T_SOA:
1705dd20
JH
1111 {
1112 const uschar *d = name;
1113 while (d != 0)
1114 {
1115 int rc = dns_lookup(dnsa, d, type, fully_qualified_name);
1116 if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
1117 while (*d != 0 && *d != '.') d++;
1118 if (*d++ == 0) break;
1119 }
1120 return DNS_NOMATCH;
1121 }
d2a2c69b
JH
1122
1123 /* Try to look up the Client SMTP Authorization SRV record for the name. If
1124 there isn't one, search from the top downwards for a CSA record in a parent
1125 domain, which might be making assertions about subdomains. If we find a record
1126 we set fully_qualified_name to whichever lookup succeeded, so that the caller
1127 can tell whether to look at the explicit authorization field or the subdomain
1128 assertion field. */
1129 case T_CSA:
1705dd20 1130 {
cab0c277 1131 uschar *srvname, *namesuff, *tld;
1705dd20
JH
1132 int priority, weight, port;
1133 int limit, rc, i;
1134 BOOL ipv6;
1135 dns_record *rr;
1136 dns_scan dnss;
1137
1138 DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
1139
1140 srvname = string_sprintf("_client._smtp.%s", name);
1141 rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
1142 if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
1143 {
1144 if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
1145 return rc;
1146 }
d2a2c69b 1147
1705dd20
JH
1148 /* Search for CSA subdomain assertion SRV records from the top downwards,
1149 starting with the 2nd level domain. This order maximizes cache-friendliness.
1150 We skip the top level domains to avoid loading their nameservers and because
1151 we know they'll never have CSA SRV records. */
d2a2c69b 1152
1705dd20
JH
1153 namesuff = Ustrrchr(name, '.');
1154 if (namesuff == NULL) return DNS_NOMATCH;
1155 tld = namesuff + 1;
1156 ipv6 = FALSE;
1157 limit = dns_csa_search_limit;
1158
1159 /* Use more appropriate search parameters if we are in the reverse DNS. */
1160
1161 if (strcmpic(namesuff, US".arpa") == 0)
1162 if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
1163 {
1164 namesuff -= 8;
d2a2c69b 1165 tld = namesuff + 1;
1705dd20
JH
1166 limit = 3;
1167 }
1168 else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
1169 {
1170 namesuff -= 4;
1171 tld = namesuff + 1;
1172 ipv6 = TRUE;
1173 limit = 3;
1174 }
d2a2c69b 1175
1705dd20 1176 DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);
d2a2c69b 1177
1705dd20
JH
1178 /* Do not perform the search if the top level or 2nd level domains do not
1179 exist. This is quite common, and when it occurs all the search queries would
1180 go to the root or TLD name servers, which is not friendly. So we check the
1181 AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
1182 the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
1183 If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
1184 the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */
1185
1186 if (rc == DNS_NOMATCH)
1187 {
1188 /* This is really gross. The successful return value from res_search() is
1189 the packet length, which is stored in dnsa->answerlen. If we get a
1190 negative DNS reply then res_search() returns -1, which causes the bounds
1191 checks for name decompression to fail when it is treated as a packet
1192 length, which in turn causes the authority search to fail. The correct
1193 packet length has been lost inside libresolv, so we have to guess a
1194 replacement value. (The only way to fix this properly would be to
1195 re-implement res_search() and res_query() so that they don't muddle their
1196 success and packet length return values.) For added safety we only reset
1197 the packet length if the packet header looks plausible. */
1198
dd708fd7 1199 const HEADER * h = (const HEADER *)dnsa->answer;
1705dd20
JH
1200 if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
1201 && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
1202 && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
1203 && ntohs(h->nscount) >= 1)
75c121f0 1204 dnsa->answerlen = sizeof(dnsa->answer);
1705dd20
JH
1205
1206 for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
8688d177 1207 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
1705dd20
JH
1208 )
1209 if (rr->type != T_SOA) continue;
1210 else if (strcmpic(rr->name, US"") == 0 ||
1211 strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
1212 else break;
1213 }
d2a2c69b 1214
1705dd20
JH
1215 for (i = 0; i < limit; i++)
1216 {
1217 if (ipv6)
1218 {
1219 /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
1220 address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
1221 namesuff -= 8;
1222 if (namesuff <= name) return DNS_NOMATCH;
1223 }
1224 else
1225 /* Find the start of the preceding domain name label. */
1226 do
1227 if (--namesuff <= name) return DNS_NOMATCH;
1228 while (*namesuff != '.');
1229
1230 DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);
1231
1232 srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
1233 rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
1234 if (rc == DNS_AGAIN) return rc;
1235 if (rc != DNS_SUCCEED) continue;
1236
1237 /* Check that the SRV record we have found is worth returning. We don't
1238 just return the first one we find, because some lower level SRV record
1239 might make stricter assertions than its parent domain. */
1240
1241 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
8688d177 1242 rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == T_SRV)
1705dd20 1243 {
dd708fd7 1244 const uschar * p = rr->data;
d2a2c69b 1245
1705dd20 1246 /* Extract the numerical SRV fields (p is incremented) */
1705dd20
JH
1247 GETSHORT(priority, p);
1248 GETSHORT(weight, p); weight = weight; /* compiler quietening */
1249 GETSHORT(port, p);
d2a2c69b 1250
1705dd20
JH
1251 /* Check the CSA version number */
1252 if (priority != 1) continue;
d2a2c69b 1253
1705dd20
JH
1254 /* If it's making an interesting assertion, return this response. */
1255 if (port & 1)
d2a2c69b 1256 {
1705dd20
JH
1257 *fully_qualified_name = namesuff + 1;
1258 return DNS_SUCCEED;
d2a2c69b 1259 }
d2a2c69b 1260 }
1705dd20
JH
1261 }
1262 return DNS_NOMATCH;
1263 }
e5a9dba6 1264
d2a2c69b 1265 default:
1705dd20
JH
1266 if (type >= 0)
1267 return dns_lookup(dnsa, name, type, fully_qualified_name);
e5a9dba6
PH
1268 }
1269
33397d19
PH
1270/* Control should never reach here */
1271
1272return DNS_FAIL;
1273}
1274
1275
1276
059ec3d9
PH
1277
1278
1279/*************************************************
1280* Get address(es) from DNS record *
1281*************************************************/
1282
d57d474f 1283/* The record type is either T_A for an IPv4 address or T_AAAA for an IPv6 address.
059ec3d9
PH
1284
1285Argument:
1286 dnsa the DNS answer block
1287 rr the RR
1288
e1a3f32f 1289Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun
059ec3d9
PH
1290*/
1291
1292dns_address *
1293dns_address_from_rr(dns_answer *dnsa, dns_record *rr)
1294{
e1a3f32f
JH
1295dns_address * yield = NULL;
1296uschar * dnsa_lim = dnsa->answer + dnsa->answerlen;
059ec3d9
PH
1297
1298if (rr->type == T_A)
1299 {
d2a2c69b 1300 uschar *p = US rr->data;
e1a3f32f
JH
1301 if (p + 4 <= dnsa_lim)
1302 {
f3ebb786
JH
1303 /* the IP is not regarded as tainted */
1304 yield = store_get(sizeof(dns_address) + 20, FALSE);
e1a3f32f
JH
1305 (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
1306 yield->next = NULL;
1307 }
059ec3d9
PH
1308 }
1309
1310#if HAVE_IPV6
1311
059ec3d9
PH
1312else
1313 {
e1a3f32f
JH
1314 if (rr->data + 16 <= dnsa_lim)
1315 {
d57d474f 1316 struct in6_addr in6;
d7978c0f 1317 for (int i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];
f3ebb786 1318 yield = store_get(sizeof(dns_address) + 50, FALSE);
d57d474f 1319 inet_ntop(AF_INET6, &in6, CS yield->address, 50);
e1a3f32f
JH
1320 yield->next = NULL;
1321 }
059ec3d9
PH
1322 }
1323#endif /* HAVE_IPV6 */
1324
1325return yield;
1326}
1327
476be7e2
JH
1328
1329
1330void
1331dns_pattern_init(void)
1332{
1333if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names)
1334 regex_check_dns_names =
1335 regex_must_compile(check_dns_names_pattern, FALSE, TRUE);
1336}
1337
8c51eead
JH
1338/* vi: aw ai sw=2
1339*/
059ec3d9 1340/* End of dns.c */