Commit | Line | Data |
---|---|---|
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 | |
18 | test harness. It recognizes some special domain names, and uses them to force | |
433a2980 PH |
19 | failure and retry responses (optionally with a delay). Otherwise, it calls an |
20 | external utility that mocks-up a nameserver, if it can find the utility. | |
21 | If not, it passes its arguments on to res_search(). The fake nameserver may | |
22 | also return a code specifying that the name should be passed on. | |
bef5a11f PH |
23 | |
24 | Background: the original test suite required a real nameserver to carry the | |
8e013028 | 25 | test zones, whereas the new test suite has the fake server for portability. This |
e7726cbf | 26 | code supports both. |
bef5a11f PH |
27 | |
28 | Arguments: | |
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 | ||
34 | Returns: length of returned data, or -1 on error (h_errno set) | |
35 | */ | |
36 | ||
37 | static int | |
1dc92d5a | 38 | fakens_search(const uschar *domain, int type, uschar *answerptr, int size) |
bef5a11f | 39 | { |
e7726cbf | 40 | int len = Ustrlen(domain); |
433a2980 | 41 | int asize = size; /* Locally modified */ |
f3ebb786 | 42 | uschar * name; |
433a2980 PH |
43 | uschar utilname[256]; |
44 | uschar *aptr = answerptr; /* Locally modified */ | |
45 | struct stat statbuf; | |
46 | ||
47 | /* Remove terminating dot. */ | |
e7726cbf PH |
48 | |
49 | if (domain[len - 1] == '.') len--; | |
f3ebb786 | 50 | name = 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 | |
57 | if (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 |
108 | else |
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 | 115 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
116 | |
117 | return 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 | |
127 | the first time we have been here, and set the resolver options. | |
128 | ||
129 | Arguments: | |
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 | |
134 | Returns: nothing | |
135 | */ | |
136 | ||
137 | void | |
8c51eead | 138 | dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec) |
059ec3d9 | 139 | { |
5bfb4cdf PP |
140 | res_state resp = os_get_dns_resolver_res(); |
141 | ||
142 | if ((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 |
151 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
152 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 153 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
154 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
155 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
156 | |
157 | #ifdef RES_USE_EDNS0 | |
158 | if (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 | |
169 | if (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 |
180 | if (use_dnssec) |
181 | resp->options |= RES_USE_DNSSEC; | |
0fbd9bff | 182 | if (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 | 200 | if (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 |
204 | if (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 | 210 | os_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 | |
220 | a name that can be used to look up PTR records. | |
221 | ||
222 | Arguments: | |
223 | string the IP address as a string | |
224 | buffer a suitable buffer, long enough to hold the result | |
225 | ||
226 | Returns: nothing | |
227 | */ | |
228 | ||
229 | void | |
55414b25 | 230 | dns_build_reverse(const uschar *string, uschar *buffer) |
059ec3d9 | 231 | { |
55414b25 | 232 | const uschar *p = string + Ustrlen(string); |
059ec3d9 PH |
233 | uschar *pp = buffer; |
234 | ||
235 | /* Handle IPv4 address */ | |
236 | ||
237 | #if HAVE_IPV6 | |
238 | if (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 | |
254 | abbreviation in the textual form. */ | |
255 | ||
256 | #if HAVE_IPV6 | |
257 | else | |
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. |
299 | Return: TRUE for a bad result | |
300 | */ | |
301 | static BOOL | |
dd708fd7 | 302 | dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta) |
2a407b17 JH |
303 | { |
304 | return (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 |
312 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
313 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
314 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
315 | |
316 | Arguments: | |
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 | |
321 | Returns: next dns record, or NULL when no more | |
322 | */ | |
323 | ||
324 | dns_record * | |
dd708fd7 | 325 | dns_next_rr(const dns_answer *dnsa, dns_scan *dnss, int reset) |
059ec3d9 | 326 | { |
dd708fd7 | 327 | const HEADER * h = (const HEADER *)dnsa->answer; |
059ec3d9 PH |
328 | int namelen; |
329 | ||
2a407b17 JH |
330 | char * trace = NULL; |
331 | #ifdef rr_trace | |
332 | # define TRACE DEBUG(D_dns) | |
333 | #else | |
334 | trace = 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 | ||
340 | if (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 |
400 | else |
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 |
404 | contains the number of RR records left. */ | |
405 | ||
406 | if (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 | 411 | TRACE trace = "R-namelen"; |
059ec3d9 | 412 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, |
2a407b17 JH |
413 | (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME); |
414 | if (namelen < 0) goto null_return; | |
059ec3d9 PH |
415 | |
416 | /* Move the pointer past the name and fill in the rest of the data structure | |
417 | from the following bytes. */ | |
418 | ||
2a407b17 | 419 | TRACE trace = "R-name"; |
dd708fd7 | 420 | if (dnss_inc_aptr(dnsa, dnss, namelen)) goto null_return; |
2a407b17 JH |
421 | |
422 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
423 | TRACE trace = "R-class"; | |
dd708fd7 | 424 | if (dnss_inc_aptr(dnsa, dnss, 2)) goto null_return; /* Don't want class */ |
2a407b17 JH |
425 | GETLONG(dnss->srr.ttl, dnss->aptr); /* TTL */ |
426 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
427 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
428 | ||
429 | /* Unchecked increment ok here since no further access on this iteration; | |
430 | will be checked on next at "R-name". */ | |
431 | ||
432 | dnss->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 | |
435 | for convenience so that the scans can use nice-looking for loops. */ | |
436 | ||
7d8d08c4 | 437 | TRACE debug_printf("%s: return %s\n", __FUNCTION__, dns_text_type(dnss->srr.type)); |
2a407b17 JH |
438 | return &dnss->srr; |
439 | ||
440 | null_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 | 449 | authoritative (AA not set), we do not extract anything. |
8db90b31 | 450 | |
4c04137d | 451 | The AUTHORITY section contains NS records if the name in question was found, |
8688d177 JH |
452 | it contains a SOA record otherwise. (This is just from experience and some |
453 | tests, is there some spec?) | |
8db90b31 | 454 | |
8688d177 JH |
455 | Scan the whole AUTHORITY section, since it may contain other records |
456 | (e.g. NSEC3) too. | |
457 | ||
458 | Return: name for the authority, in an allocated string, or NULL if none found */ | |
09b80b4e JH |
459 | |
460 | static const uschar * | |
461 | dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */ | |
9820a77f | 462 | { |
09b80b4e | 463 | dns_scan dnss; |
dd708fd7 | 464 | const HEADER * h = (const HEADER *) dnsa->answer; |
09b80b4e | 465 | |
8688d177 | 466 | if (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 | 471 | return NULL; |
9820a77f HSHR |
472 | } |
473 | ||
474 | ||
059ec3d9 PH |
475 | |
476 | ||
1f4a55da PP |
477 | /************************************************* |
478 | * Return whether AD bit set in DNS result * | |
479 | *************************************************/ | |
480 | ||
481 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
482 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
4c04137d | 483 | (AD = Authentic Data, AA = Authoritative Answer) |
1f4a55da PP |
484 | |
485 | Argument: pointer to dns answer block | |
486 | Returns: bool indicating presence of AD bit | |
487 | */ | |
488 | ||
489 | BOOL | |
4a142059 | 490 | dns_is_secure(const dns_answer * dnsa) |
1f4a55da PP |
491 | { |
492 | #ifdef DISABLE_DNSSEC | |
493 | DEBUG(D_dns) | |
494 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
495 | return FALSE; | |
496 | #else | |
dd708fd7 | 497 | const HEADER * h = (const HEADER *) dnsa->answer; |
09b80b4e JH |
498 | const uschar * auth_name; |
499 | const uschar * trusted; | |
9820a77f | 500 | |
979c462e | 501 | if (dnsa->answerlen < 0) return FALSE; |
9820a77f | 502 | if (h->ad) return TRUE; |
9820a77f | 503 | |
979c462e JH |
504 | /* If the resolver we ask is authoritative for the domain in question, it may |
505 | not set the AD but the AA bit. If we explicitly trust the resolver for that | |
506 | domain (via a domainlist in dns_trust_aa), we return TRUE to indicate a secure | |
507 | answer. */ | |
9820a77f | 508 | |
09b80b4e JH |
509 | if ( !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 |
519 | DEBUG(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 | 523 | return TRUE; |
1f4a55da PP |
524 | #endif |
525 | } | |
526 | ||
4a142059 JH |
527 | static void |
528 | dns_set_insecure(dns_answer * dnsa) | |
529 | { | |
e87c01c7 | 530 | #ifndef DISABLE_DNSSEC |
4a142059 | 531 | HEADER * h = (HEADER *)dnsa->answer; |
8688d177 | 532 | h->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 | ||
542 | BOOL | |
979c462e | 543 | dns_is_aa(const dns_answer * dnsa) |
221dff13 | 544 | { |
e87c01c7 MH |
545 | #ifdef DISABLE_DNSSEC |
546 | return FALSE; | |
547 | #else | |
979c462e | 548 | return dnsa->answerlen >= 0 && ((const HEADER *)dnsa->answer)->aa; |
e87c01c7 | 549 | #endif |
221dff13 | 550 | } |
1f4a55da PP |
551 | |
552 | ||
553 | ||
059ec3d9 PH |
554 | /************************************************* |
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 |
559 | uses should be included here. | |
059ec3d9 PH |
560 | |
561 | Argument: record type | |
562 | Returns: pointer to string | |
563 | */ | |
564 | ||
565 | uschar * | |
566 | dns_text_type(int t) | |
567 | { | |
568 | switch(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 |
592 | static void |
593 | dns_fail_tag(uschar * buf, const uschar * name, int dns_type) | |
594 | { | |
595 | res_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 | |
598 | We truncate the name here for safety... could use a dynamic string. */ | |
599 | ||
cabf3e99 JH |
600 | sprintf(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 |
606 | times for the same domain. We need to retain the resolver options because they | |
607 | may change. For successful lookups, we rely on resolver and/or name server | |
608 | caching. | |
609 | ||
610 | Arguments: | |
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 | ||
616 | Returns: 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 | |
624 | static int | |
625 | dns_fail_return(const uschar * name, int type, time_t expiry, int rc) | |
626 | { | |
627 | uschar node_name[DNS_FAILTAG_MAX]; | |
628 | tree_node * previous, * new; | |
629 | expiring_data * e; | |
630 | ||
631 | dns_fail_tag(node_name, name, type); | |
632 | if ((previous = tree_search(tree_dns_fails, node_name))) | |
633 | e = previous->data.ptr; | |
634 | else | |
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 | ||
643 | DEBUG(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); | |
646 | e->expiry = expiry; | |
647 | e->data.val = rc; | |
648 | return rc; | |
649 | } | |
650 | ||
651 | ||
652 | /* Return the cached result of a known-bad lookup, or -1. | |
653 | */ | |
059ec3d9 | 654 | static int |
7d8d08c4 | 655 | dns_fail_cache_hit(const uschar * name, int type) |
059ec3d9 | 656 | { |
7d8d08c4 JH |
657 | uschar node_name[DNS_FAILTAG_MAX]; |
658 | tree_node * previous; | |
659 | expiring_data * e; | |
660 | int val, rc; | |
661 | ||
662 | dns_fail_tag(node_name, name, type); | |
663 | if (!(previous = tree_search(tree_dns_fails, node_name))) | |
664 | return -1; | |
665 | ||
666 | e = previous->data.ptr; | |
667 | val = e->data.val; | |
668 | rc = e->expiry && e->expiry <= time(NULL) ? -1 : val; | |
669 | ||
670 | DEBUG(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 |
679 | return rc; |
680 | } | |
681 | ||
7d8d08c4 JH |
682 | |
683 | ||
684 | /* Return the TTL suitable for an NXDOMAIN result, which is given | |
685 | in the SOA. We hope that one was returned in the lookup, and do not | |
686 | bother doing a separate lookup; if not found return a forever TTL. | |
687 | */ | |
688 | ||
3462da30 | 689 | time_t |
7d8d08c4 JH |
690 | dns_expire_from_soa(dns_answer * dnsa) |
691 | { | |
692 | const HEADER * h = (const HEADER *)dnsa->answer; | |
693 | dns_scan dnss; | |
694 | ||
695 | /* This is really gross. The successful return value from res_search() is | |
696 | the packet length, which is stored in dnsa->answerlen. If we get a | |
697 | negative DNS reply then res_search() returns -1, which causes the bounds | |
698 | checks for name decompression to fail when it is treated as a packet | |
699 | length, which in turn causes the authority search to fail. The correct | |
700 | packet length has been lost inside libresolv, so we have to guess a | |
701 | replacement value. (The only way to fix this properly would be to | |
702 | re-implement res_search() and res_query() so that they don't muddle their | |
703 | success and packet length return values.) For added safety we only reset | |
704 | the packet length if the packet header looks plausible. */ | |
705 | ||
706 | if ( 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 | ||
713 | for (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 | } | |
742 | DEBUG(D_dns) debug_printf("DNS: no SOA record found for neg-TTL\n"); | |
743 | return 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, | |
752 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
4c04137d | 753 | Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set |
059ec3d9 PH |
754 | up nameservers that produce this error continually, so there is the option of |
755 | providing a list of domains for which this is treated as a non-existent | |
756 | host. | |
757 | ||
75c121f0 JH |
758 | The 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 | |
760 | use a stack-auto variable. | |
761 | ||
059ec3d9 PH |
762 | Arguments: |
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 | ||
767 | Returns: 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 | ||
776 | int | |
7d8d08c4 | 777 | dns_basic_lookup(dns_answer * dnsa, const uschar * name, int type) |
059ec3d9 | 778 | { |
7d8d08c4 | 779 | int rc; |
059ec3d9 | 780 | #ifndef STAND_ALONE |
7d8d08c4 | 781 | const 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 |
785 | a timeout on one domain doesn't happen time and time again for messages that | |
786 | have many addresses in the same domain. We rely on the resolver and name server | |
7d8d08c4 JH |
787 | caching for successful lookups. |
788 | */ | |
059ec3d9 | 789 | |
7d8d08c4 | 790 | if ((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 |
816 | although DNS lookups may give REFUSED at the lower level, some resolvers |
817 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
818 | domains cannot be in the DNS. The check is now done by a regular expression; | |
819 | give it space for substring storage to save it having to get its own if the | |
820 | regex has substrings that are used - the default uses a conditional. | |
821 | ||
822 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
823 | lookup, which constructs the names itself, so they should be OK. Besides, | |
6219e0ec SA |
824 | bitstring labels don't conform to normal name syntax. (But they aren't used any |
825 | more.) */ | |
059ec3d9 PH |
826 | |
827 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
828 | ||
482d1455 | 829 | if (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 |
848 | number of bytes the message would need, so we need to check for this case. The |
849 | effect is to truncate overlong data. | |
850 | ||
30e18802 PH |
851 | On some systems, res_search() will recognize "A-for-A" queries and return |
852 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
853 | nameservers are also believed to do this. It is, of course, contrary to the | |
854 | specification of the DNS, so we lock it out. */ | |
855 | ||
cc00f4af | 856 | if ((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 |
861 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
862 | ||
979c462e | 863 | h_errno = 0; |
8768d548 | 864 | dnsa->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 | 868 | if (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 | |
876 | if (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 | ||
923 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
924 | name, dns_text_type(type)); | |
925 | ||
926 | return 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 | |
937 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
938 | the DNS, but you are supposed to cope with them if you find them. | |
d8d9f930 JH |
939 | By default, follow one CNAME since a resolver has been seen, faced with |
940 | an MX request and a CNAME (to an A) but no MX present, returning the CNAME. | |
059ec3d9 PH |
941 | |
942 | The assumption is made that if the resolver gives back records of the | |
943 | requested type *and* a CNAME, we don't need to make another call to look up | |
944 | the CNAME. I can't see how it could return only some of the right records. If | |
945 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
946 | won't return any. | |
947 | ||
948 | If fully_qualified_name is not NULL, set it to point to the full name | |
949 | returned by the resolver, if this is different to what it is given, unless | |
950 | the returned name starts with "*" as some nameservers seem to be returning | |
766e7a65 JH |
951 | wildcards in this form. In international mode "different" means "alabel |
952 | forms are different". | |
059ec3d9 PH |
953 | |
954 | Arguments: | |
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 | ||
961 | Returns: 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 | ||
968 | int | |
1dc92d5a | 969 | dns_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 970 | const uschar **fully_qualified_name) |
059ec3d9 | 971 | { |
1dc92d5a | 972 | const uschar *orig_name = name; |
c85b3043 | 973 | BOOL secure_so_far = TRUE; |
059ec3d9 | 974 | |
d8d9f930 JH |
975 | /* By default, assume the resolver follows CNAME chains (and returns NODATA for |
976 | an unterminated one). If it also does that for a CNAME loop, fine; if it returns | |
977 | a CNAME (maybe the last?) whine about it. However, retain the coding for dumb | |
978 | resolvers hiding behind a config variable. Loop to follow CNAME chains so far, | |
979 | but no further... The testsuite tests the latter case, mostly assuming that the | |
980 | former will work. */ | |
059ec3d9 | 981 | |
d7978c0f | 982 | for (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 | |
1062 | right... */ | |
1063 | ||
1064 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
1065 | return 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 | 1078 | not available in the basic types. The special types all have negative values. |
33397d19 PH |
1079 | Positive type values are passed straight on to dns_lookup(). |
1080 | ||
1081 | Arguments: | |
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 | ||
1088 | Returns: 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 | ||
1095 | int | |
1dc92d5a | 1096 | dns_special_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 1097 | const uschar **fully_qualified_name) |
33397d19 | 1098 | { |
d2a2c69b | 1099 | switch (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 | ||
1272 | return 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 | |
1285 | Argument: | |
1286 | dnsa the DNS answer block | |
1287 | rr the RR | |
1288 | ||
e1a3f32f | 1289 | Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun |
059ec3d9 PH |
1290 | */ |
1291 | ||
1292 | dns_address * | |
1293 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1294 | { | |
e1a3f32f JH |
1295 | dns_address * yield = NULL; |
1296 | uschar * dnsa_lim = dnsa->answer + dnsa->answerlen; | |
059ec3d9 PH |
1297 | |
1298 | if (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 |
1312 | else |
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 | ||
1325 | return yield; | |
1326 | } | |
1327 | ||
476be7e2 JH |
1328 | |
1329 | ||
1330 | void | |
1331 | dns_pattern_init(void) | |
1332 | { | |
1333 | if (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 */ |