Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
f9ba5e22 | 5 | /* Copyright (c) University of Cambridge 1995 - 2018 */ |
1e1ddfac | 6 | /* Copyright (c) The Exim Maintainers 2020 */ |
059ec3d9 PH |
7 | /* See the file NOTICE for conditions of use and distribution. */ |
8 | ||
9 | /* Functions for interfacing with the DNS. */ | |
10 | ||
11 | #include "exim.h" | |
12 | ||
13 | ||
bef5a11f PH |
14 | /************************************************* |
15 | * Fake DNS resolver * | |
16 | *************************************************/ | |
17 | ||
18 | /* This function is called instead of res_search() when Exim is running in its | |
19 | test harness. It recognizes some special domain names, and uses them to force | |
433a2980 PH |
20 | failure and retry responses (optionally with a delay). Otherwise, it calls an |
21 | external utility that mocks-up a nameserver, if it can find the utility. | |
22 | If not, it passes its arguments on to res_search(). The fake nameserver may | |
23 | also return a code specifying that the name should be passed on. | |
bef5a11f PH |
24 | |
25 | Background: the original test suite required a real nameserver to carry the | |
8e013028 | 26 | test zones, whereas the new test suite has the fake server for portability. This |
e7726cbf | 27 | code supports both. |
bef5a11f PH |
28 | |
29 | Arguments: | |
e7726cbf | 30 | domain the domain name |
bef5a11f PH |
31 | type the DNS record type |
32 | answerptr where to put the answer | |
33 | size size of the answer area | |
34 | ||
35 | Returns: length of returned data, or -1 on error (h_errno set) | |
36 | */ | |
37 | ||
38 | static int | |
1dc92d5a | 39 | fakens_search(const uschar *domain, int type, uschar *answerptr, int size) |
bef5a11f | 40 | { |
e7726cbf | 41 | int len = Ustrlen(domain); |
433a2980 | 42 | int asize = size; /* Locally modified */ |
f3ebb786 | 43 | uschar * name; |
433a2980 PH |
44 | uschar utilname[256]; |
45 | uschar *aptr = answerptr; /* Locally modified */ | |
46 | struct stat statbuf; | |
47 | ||
48 | /* Remove terminating dot. */ | |
e7726cbf PH |
49 | |
50 | if (domain[len - 1] == '.') len--; | |
f3ebb786 | 51 | name = string_copyn(domain, len); |
bef5a11f | 52 | |
433a2980 PH |
53 | /* Look for the fakens utility, and if it exists, call it. */ |
54 | ||
5f3d0983 HSHR |
55 | (void)string_format(utilname, sizeof(utilname), "%s/bin/fakens", |
56 | config_main_directory); | |
433a2980 PH |
57 | |
58 | if (stat(CS utilname, &statbuf) >= 0) | |
bef5a11f | 59 | { |
433a2980 PH |
60 | pid_t pid; |
61 | int infd, outfd, rc; | |
62 | uschar *argv[5]; | |
63 | ||
eb24befc JH |
64 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", |
65 | name, dns_text_type(type)); | |
433a2980 PH |
66 | |
67 | argv[0] = utilname; | |
5f3d0983 | 68 | argv[1] = config_main_directory; |
433a2980 PH |
69 | argv[2] = name; |
70 | argv[3] = dns_text_type(type); | |
71 | argv[4] = NULL; | |
72 | ||
eb24befc | 73 | pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE, US"fakens-search"); |
433a2980 PH |
74 | if (pid < 0) |
75 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s", | |
76 | strerror(errno)); | |
77 | ||
78 | len = 0; | |
79 | rc = -1; | |
80 | while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0) | |
81 | { | |
82 | len += rc; | |
83 | aptr += rc; /* Don't modify the actual arguments, because they */ | |
84 | asize -= rc; /* may need to be passed on to res_search(). */ | |
85 | } | |
bef5a11f | 86 | |
aa7751be | 87 | /* If we ran out of output buffer before exhausting the return, |
1fb7660f JH |
88 | carry on reading and counting it. */ |
89 | ||
90 | if (asize == 0) | |
91 | while ((rc = read(outfd, name, sizeof(name))) > 0) | |
92 | len += rc; | |
93 | ||
433a2980 PH |
94 | if (rc < 0) |
95 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s", | |
96 | strerror(errno)); | |
bef5a11f | 97 | |
433a2980 | 98 | switch(child_close(pid, 0)) |
bef5a11f | 99 | { |
433a2980 PH |
100 | case 0: return len; |
101 | case 1: h_errno = HOST_NOT_FOUND; return -1; | |
102 | case 2: h_errno = TRY_AGAIN; return -1; | |
103 | default: | |
104 | case 3: h_errno = NO_RECOVERY; return -1; | |
105 | case 4: h_errno = NO_DATA; return -1; | |
106 | case 5: /* Pass on to res_search() */ | |
107 | DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n"); | |
bef5a11f PH |
108 | } |
109 | } | |
8e013028 HSHR |
110 | else |
111 | { | |
4cea764f | 112 | DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname); |
8e013028 | 113 | } |
bef5a11f | 114 | |
433a2980 | 115 | /* fakens utility not found, or it returned "pass on" */ |
bef5a11f | 116 | |
433a2980 | 117 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
118 | |
119 | return res_search(CS domain, C_IN, type, answerptr, size); | |
bef5a11f PH |
120 | } |
121 | ||
122 | ||
059ec3d9 PH |
123 | |
124 | /************************************************* | |
125 | * Initialize and configure resolver * | |
126 | *************************************************/ | |
127 | ||
128 | /* Initialize the resolver and the storage for holding DNS answers if this is | |
129 | the first time we have been here, and set the resolver options. | |
130 | ||
131 | Arguments: | |
132 | qualify_single TRUE to set the RES_DEFNAMES option | |
133 | search_parents TRUE to set the RES_DNSRCH option | |
8c51eead | 134 | use_dnssec TRUE to set the RES_USE_DNSSEC option |
059ec3d9 PH |
135 | |
136 | Returns: nothing | |
137 | */ | |
138 | ||
139 | void | |
8c51eead | 140 | dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec) |
059ec3d9 | 141 | { |
5bfb4cdf PP |
142 | res_state resp = os_get_dns_resolver_res(); |
143 | ||
144 | if ((resp->options & RES_INIT) == 0) | |
059ec3d9 | 145 | { |
5bfb4cdf PP |
146 | DEBUG(D_resolver) resp->options |= RES_DEBUG; /* For Cygwin */ |
147 | os_put_dns_resolver_res(resp); | |
059ec3d9 | 148 | res_init(); |
5bfb4cdf PP |
149 | DEBUG(D_resolver) resp->options |= RES_DEBUG; |
150 | os_put_dns_resolver_res(resp); | |
059ec3d9 PH |
151 | } |
152 | ||
5bfb4cdf PP |
153 | resp->options &= ~(RES_DNSRCH | RES_DEFNAMES); |
154 | resp->options |= (qualify_single? RES_DEFNAMES : 0) | | |
059ec3d9 | 155 | (search_parents? RES_DNSRCH : 0); |
5bfb4cdf PP |
156 | if (dns_retrans > 0) resp->retrans = dns_retrans; |
157 | if (dns_retry > 0) resp->retry = dns_retry; | |
e97d1f08 PP |
158 | |
159 | #ifdef RES_USE_EDNS0 | |
160 | if (dns_use_edns0 >= 0) | |
161 | { | |
162 | if (dns_use_edns0) | |
5bfb4cdf | 163 | resp->options |= RES_USE_EDNS0; |
e97d1f08 | 164 | else |
5bfb4cdf | 165 | resp->options &= ~RES_USE_EDNS0; |
e97d1f08 PP |
166 | DEBUG(D_resolver) |
167 | debug_printf("Coerced resolver EDNS0 support %s.\n", | |
168 | dns_use_edns0 ? "on" : "off"); | |
169 | } | |
170 | #else | |
171 | if (dns_use_edns0 >= 0) | |
172 | DEBUG(D_resolver) | |
173 | debug_printf("Unable to %sset EDNS0 without resolver support.\n", | |
174 | dns_use_edns0 ? "" : "un"); | |
175 | #endif | |
5bfb4cdf | 176 | |
1f4a55da PP |
177 | #ifndef DISABLE_DNSSEC |
178 | # ifdef RES_USE_DNSSEC | |
179 | # ifndef RES_USE_EDNS0 | |
180 | # error Have RES_USE_DNSSEC but not RES_USE_EDNS0? Something hinky ... | |
181 | # endif | |
8c51eead JH |
182 | if (use_dnssec) |
183 | resp->options |= RES_USE_DNSSEC; | |
0fbd9bff | 184 | if (dns_dnssec_ok >= 0) |
1f4a55da | 185 | { |
0fbd9bff | 186 | if (dns_use_edns0 == 0 && dns_dnssec_ok != 0) |
1f4a55da PP |
187 | { |
188 | DEBUG(D_resolver) | |
0fbd9bff | 189 | debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n"); |
1f4a55da PP |
190 | } |
191 | else | |
192 | { | |
0fbd9bff | 193 | if (dns_dnssec_ok) |
1f4a55da PP |
194 | resp->options |= RES_USE_DNSSEC; |
195 | else | |
196 | resp->options &= ~RES_USE_DNSSEC; | |
197 | DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n", | |
0fbd9bff | 198 | dns_dnssec_ok ? "on" : "off"); |
1f4a55da PP |
199 | } |
200 | } | |
201 | # else | |
0fbd9bff | 202 | if (dns_dnssec_ok >= 0) |
1f4a55da PP |
203 | DEBUG(D_resolver) |
204 | debug_printf("Unable to %sset DNSSEC without resolver support.\n", | |
0fbd9bff | 205 | dns_dnssec_ok ? "" : "un"); |
8c51eead JH |
206 | if (use_dnssec) |
207 | DEBUG(D_resolver) | |
93d4b03a | 208 | debug_printf("Unable to set DNSSEC without resolver support.\n"); |
1f4a55da PP |
209 | # endif |
210 | #endif /* DISABLE_DNSSEC */ | |
211 | ||
5bfb4cdf | 212 | os_put_dns_resolver_res(resp); |
059ec3d9 PH |
213 | } |
214 | ||
215 | ||
216 | ||
217 | /************************************************* | |
218 | * Build key name for PTR records * | |
219 | *************************************************/ | |
220 | ||
221 | /* This function inverts an IP address and adds the relevant domain, to produce | |
222 | a name that can be used to look up PTR records. | |
223 | ||
224 | Arguments: | |
225 | string the IP address as a string | |
059ec3d9 | 226 | |
152481a0 | 227 | Returns: an allocated string |
059ec3d9 PH |
228 | */ |
229 | ||
152481a0 JH |
230 | uschar * |
231 | dns_build_reverse(const uschar * string) | |
059ec3d9 | 232 | { |
152481a0 JH |
233 | const uschar * p = string + Ustrlen(string); |
234 | gstring * g = NULL; | |
059ec3d9 PH |
235 | |
236 | /* Handle IPv4 address */ | |
237 | ||
238 | #if HAVE_IPV6 | |
239 | if (Ustrchr(string, ':') == NULL) | |
240 | #endif | |
241 | { | |
d7978c0f | 242 | for (int i = 0; i < 4; i++) |
059ec3d9 | 243 | { |
152481a0 | 244 | const uschar * ppp = p; |
059ec3d9 | 245 | while (ppp > string && ppp[-1] != '.') ppp--; |
152481a0 JH |
246 | g = string_catn(g, ppp, p - ppp); |
247 | g = string_catn(g, US".", 1); | |
059ec3d9 PH |
248 | p = ppp - 1; |
249 | } | |
152481a0 | 250 | g = string_catn(g, US"in-addr.arpa", 12); |
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 | 259 | int v6[4]; |
152481a0 JH |
260 | |
261 | g = string_get_tainted(32, is_tainted(string)); | |
059ec3d9 PH |
262 | (void)host_aton(string, v6); |
263 | ||
264 | /* The original specification for IPv6 reverse lookup was to invert each | |
265 | nibble, and look in the ip6.int domain. The domain was subsequently | |
266 | changed to ip6.arpa. */ | |
267 | ||
d7978c0f JH |
268 | for (int i = 3; i >= 0; i--) |
269 | for (int j = 0; j < 32; j += 4) | |
152481a0 JH |
270 | g = string_fmt_append(g, "%x.", (v6[i] >> j) & 15); |
271 | g = string_catn(g, US"ip6.arpa.", 9); | |
059ec3d9 PH |
272 | |
273 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
274 | with A6 records. However, it fell out of favour when they did. The | |
275 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
276 | to make this code do that, but I could not make it work on Solaris 8. The | |
277 | resolver seems to lose the initial backslash somehow. However, now that | |
278 | this style of reverse lookup has been dropped, it doesn't matter. These | |
279 | lines are left here purely for historical interest. */ | |
280 | ||
281 | /************************************************** | |
282 | Ustrcpy(pp, "\\[x"); | |
283 | pp += 3; | |
284 | ||
d7978c0f | 285 | for (int i = 0; i < 4; i++) |
059ec3d9 PH |
286 | { |
287 | sprintf(pp, "%08X", v6[i]); | |
288 | pp += 8; | |
289 | } | |
f3ebb786 | 290 | Ustrcpy(pp, US"].ip6.arpa."); |
059ec3d9 PH |
291 | **************************************************/ |
292 | ||
293 | } | |
294 | #endif | |
152481a0 | 295 | return string_from_gstring(g); |
059ec3d9 PH |
296 | } |
297 | ||
298 | ||
299 | ||
300 | ||
2a407b17 JH |
301 | /* Increment the aptr in dnss, checking against dnsa length. |
302 | Return: TRUE for a bad result | |
303 | */ | |
304 | static BOOL | |
dd708fd7 | 305 | dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta) |
2a407b17 JH |
306 | { |
307 | return (dnss->aptr += delta) >= dnsa->answer + dnsa->answerlen; | |
308 | } | |
309 | ||
059ec3d9 PH |
310 | /************************************************* |
311 | * Get next DNS record from answer block * | |
312 | *************************************************/ | |
313 | ||
314 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
315 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
316 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
317 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
318 | |
319 | Arguments: | |
320 | dnsa pointer to dns answer block | |
321 | dnss pointer to dns scan block | |
4c04137d | 322 | reset option specifying what portion to scan, as described above |
059ec3d9 PH |
323 | |
324 | Returns: next dns record, or NULL when no more | |
325 | */ | |
326 | ||
327 | dns_record * | |
dd708fd7 | 328 | dns_next_rr(const dns_answer *dnsa, dns_scan *dnss, int reset) |
059ec3d9 | 329 | { |
dd708fd7 | 330 | const HEADER * h = (const HEADER *)dnsa->answer; |
059ec3d9 PH |
331 | int namelen; |
332 | ||
2a407b17 JH |
333 | char * trace = NULL; |
334 | #ifdef rr_trace | |
335 | # define TRACE DEBUG(D_dns) | |
336 | #else | |
337 | trace = trace; | |
338 | # define TRACE if (FALSE) | |
339 | #endif | |
340 | ||
059ec3d9 PH |
341 | /* Reset the saved data when requested to, and skip to the first required RR */ |
342 | ||
343 | if (reset != RESET_NEXT) | |
344 | { | |
345 | dnss->rrcount = ntohs(h->qdcount); | |
d093f8e5 | 346 | TRACE debug_printf("%s: reset (Q rrcount %d)\n", __FUNCTION__, dnss->rrcount); |
059ec3d9 PH |
347 | dnss->aptr = dnsa->answer + sizeof(HEADER); |
348 | ||
349 | /* Skip over questions; failure to expand the name just gives up */ | |
350 | ||
351 | while (dnss->rrcount-- > 0) | |
352 | { | |
2a407b17 | 353 | TRACE trace = "Q-namelen"; |
059ec3d9 | 354 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, |
2a407b17 JH |
355 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME); |
356 | if (namelen < 0) goto null_return; | |
357 | /* skip name & type & class */ | |
358 | TRACE trace = "Q-skip"; | |
dd708fd7 | 359 | if (dnss_inc_aptr(dnsa, dnss, namelen+4)) goto null_return; |
059ec3d9 PH |
360 | } |
361 | ||
362 | /* Get the number of answer records. */ | |
363 | ||
364 | dnss->rrcount = ntohs(h->ancount); | |
d093f8e5 | 365 | TRACE debug_printf("%s: reset (A rrcount %d)\n", __FUNCTION__, dnss->rrcount); |
059ec3d9 | 366 | |
e5a9dba6 PH |
367 | /* Skip over answers if we want to look at the authority section. Also skip |
368 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
369 | records. */ |
370 | ||
2a407b17 JH |
371 | if (reset == RESET_ADDITIONAL) |
372 | { | |
373 | TRACE debug_printf("%s: additional\n", __FUNCTION__); | |
374 | dnss->rrcount += ntohs(h->nscount); | |
d093f8e5 | 375 | TRACE debug_printf("%s: reset (NS rrcount %d)\n", __FUNCTION__, dnss->rrcount); |
2a407b17 | 376 | } |
e5a9dba6 PH |
377 | |
378 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 379 | { |
2a407b17 JH |
380 | TRACE if (reset == RESET_AUTHORITY) |
381 | debug_printf("%s: authority\n", __FUNCTION__); | |
059ec3d9 PH |
382 | while (dnss->rrcount-- > 0) |
383 | { | |
2a407b17 | 384 | TRACE trace = "A-namelen"; |
059ec3d9 | 385 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, |
2a407b17 JH |
386 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME); |
387 | if (namelen < 0) goto null_return; | |
388 | /* skip name, type, class & TTL */ | |
389 | TRACE trace = "A-hdr"; | |
dd708fd7 | 390 | if (dnss_inc_aptr(dnsa, dnss, namelen+8)) goto null_return; |
059ec3d9 | 391 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ |
2a407b17 JH |
392 | /* skip over it */ |
393 | TRACE trace = "A-skip"; | |
dd708fd7 | 394 | if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size)) goto null_return; |
059ec3d9 | 395 | } |
2a407b17 | 396 | dnss->rrcount = reset == RESET_AUTHORITY |
e5a9dba6 | 397 | ? ntohs(h->nscount) : ntohs(h->arcount); |
d093f8e5 JH |
398 | TRACE debug_printf("%s: reset (%s rrcount %d)\n", __FUNCTION__, |
399 | reset == RESET_AUTHORITY ? "NS" : "AR", dnss->rrcount); | |
059ec3d9 | 400 | } |
2a407b17 | 401 | TRACE debug_printf("%s: %d RRs to read\n", __FUNCTION__, dnss->rrcount); |
059ec3d9 | 402 | } |
2a407b17 JH |
403 | else |
404 | TRACE debug_printf("%s: next (%d left)\n", __FUNCTION__, dnss->rrcount); | |
059ec3d9 | 405 | |
059ec3d9 PH |
406 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
407 | contains the number of RR records left. */ | |
408 | ||
409 | if (dnss->rrcount-- <= 0) return NULL; | |
410 | ||
411 | /* If expanding the RR domain name fails, behave as if no more records | |
412 | (something safe). */ | |
413 | ||
2a407b17 | 414 | TRACE trace = "R-namelen"; |
059ec3d9 | 415 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, |
2a407b17 JH |
416 | (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME); |
417 | if (namelen < 0) goto null_return; | |
059ec3d9 PH |
418 | |
419 | /* Move the pointer past the name and fill in the rest of the data structure | |
420 | from the following bytes. */ | |
421 | ||
2a407b17 | 422 | TRACE trace = "R-name"; |
dd708fd7 | 423 | if (dnss_inc_aptr(dnsa, dnss, namelen)) goto null_return; |
2a407b17 JH |
424 | |
425 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
426 | TRACE trace = "R-class"; | |
dd708fd7 | 427 | if (dnss_inc_aptr(dnsa, dnss, 2)) goto null_return; /* Don't want class */ |
2a407b17 JH |
428 | GETLONG(dnss->srr.ttl, dnss->aptr); /* TTL */ |
429 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
430 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
431 | ||
432 | /* Unchecked increment ok here since no further access on this iteration; | |
433 | will be checked on next at "R-name". */ | |
434 | ||
435 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
059ec3d9 PH |
436 | |
437 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
438 | for convenience so that the scans can use nice-looking for loops. */ | |
439 | ||
7d8d08c4 | 440 | TRACE debug_printf("%s: return %s\n", __FUNCTION__, dns_text_type(dnss->srr.type)); |
2a407b17 JH |
441 | return &dnss->srr; |
442 | ||
443 | null_return: | |
d093f8e5 JH |
444 | TRACE debug_printf("%s: terminate (%d RRs left). Last op: %s; errno %d %s\n", |
445 | __FUNCTION__, dnss->rrcount, trace, errno, strerror(errno)); | |
2a407b17 JH |
446 | dnss->rrcount = 0; |
447 | return NULL; | |
059ec3d9 PH |
448 | } |
449 | ||
450 | ||
8688d177 | 451 | /* Extract the AUTHORITY information from the answer. If the answer isn't |
4c04137d | 452 | authoritative (AA not set), we do not extract anything. |
8db90b31 | 453 | |
4c04137d | 454 | The AUTHORITY section contains NS records if the name in question was found, |
8688d177 JH |
455 | it contains a SOA record otherwise. (This is just from experience and some |
456 | tests, is there some spec?) | |
8db90b31 | 457 | |
8688d177 JH |
458 | Scan the whole AUTHORITY section, since it may contain other records |
459 | (e.g. NSEC3) too. | |
460 | ||
461 | Return: name for the authority, in an allocated string, or NULL if none found */ | |
09b80b4e JH |
462 | |
463 | static const uschar * | |
464 | dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */ | |
9820a77f | 465 | { |
09b80b4e | 466 | dns_scan dnss; |
dd708fd7 | 467 | const HEADER * h = (const HEADER *) dnsa->answer; |
09b80b4e | 468 | |
8688d177 | 469 | if (h->nscount && h->aa) |
d7978c0f | 470 | for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); |
8688d177 JH |
471 | rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) |
472 | if (rr->type == (h->ancount ? T_NS : T_SOA)) | |
473 | return string_copy(rr->name); | |
09b80b4e | 474 | return NULL; |
9820a77f HSHR |
475 | } |
476 | ||
477 | ||
059ec3d9 PH |
478 | |
479 | ||
1f4a55da PP |
480 | /************************************************* |
481 | * Return whether AD bit set in DNS result * | |
482 | *************************************************/ | |
483 | ||
484 | /* We do not perform DNSSEC work ourselves; if the administrator has installed | |
485 | a verifying resolver which sets AD as appropriate, though, we'll use that. | |
4c04137d | 486 | (AD = Authentic Data, AA = Authoritative Answer) |
1f4a55da PP |
487 | |
488 | Argument: pointer to dns answer block | |
489 | Returns: bool indicating presence of AD bit | |
490 | */ | |
491 | ||
492 | BOOL | |
4a142059 | 493 | dns_is_secure(const dns_answer * dnsa) |
1f4a55da PP |
494 | { |
495 | #ifdef DISABLE_DNSSEC | |
496 | DEBUG(D_dns) | |
497 | debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n"); | |
498 | return FALSE; | |
499 | #else | |
dd708fd7 | 500 | const HEADER * h = (const HEADER *) dnsa->answer; |
09b80b4e JH |
501 | const uschar * auth_name; |
502 | const uschar * trusted; | |
9820a77f | 503 | |
979c462e | 504 | if (dnsa->answerlen < 0) return FALSE; |
dce58c04 PP |
505 | /* Beware that newer versions of glibc on Linux will filter out the ad bit |
506 | unless their shiny new RES_TRUSTAD bit is set for the resolver. */ | |
9820a77f | 507 | if (h->ad) return TRUE; |
9820a77f | 508 | |
979c462e JH |
509 | /* If the resolver we ask is authoritative for the domain in question, it may |
510 | not set the AD but the AA bit. If we explicitly trust the resolver for that | |
511 | domain (via a domainlist in dns_trust_aa), we return TRUE to indicate a secure | |
512 | answer. */ | |
9820a77f | 513 | |
09b80b4e JH |
514 | if ( !h->aa |
515 | || !dns_trust_aa | |
25bf2076 HSHR |
516 | || !(trusted = expand_string(dns_trust_aa)) |
517 | || !*trusted | |
09b80b4e JH |
518 | || !(auth_name = dns_extract_auth_name(dnsa)) |
519 | || OK != match_isinlist(auth_name, &trusted, 0, NULL, NULL, | |
94431adb | 520 | MCL_DOMAIN, TRUE, NULL) |
09b80b4e JH |
521 | ) |
522 | return FALSE; | |
9820a77f | 523 | |
09b80b4e JH |
524 | DEBUG(D_dns) debug_printf("DNS faked the AD bit " |
525 | "(got AA and matched with dns_trust_aa (%s in %s))\n", | |
526 | auth_name, dns_trust_aa); | |
9820a77f | 527 | |
09b80b4e | 528 | return TRUE; |
1f4a55da PP |
529 | #endif |
530 | } | |
531 | ||
4a142059 JH |
532 | static void |
533 | dns_set_insecure(dns_answer * dnsa) | |
534 | { | |
e87c01c7 | 535 | #ifndef DISABLE_DNSSEC |
4a142059 | 536 | HEADER * h = (HEADER *)dnsa->answer; |
8688d177 | 537 | h->aa = h->ad = 0; |
e87c01c7 | 538 | #endif |
4a142059 JH |
539 | } |
540 | ||
221dff13 HSHR |
541 | /************************************************ |
542 | * Check whether the AA bit is set * | |
543 | * We need this to warn if we requested AD * | |
4c04137d | 544 | * from an authoritative server * |
221dff13 HSHR |
545 | ************************************************/ |
546 | ||
547 | BOOL | |
979c462e | 548 | dns_is_aa(const dns_answer * dnsa) |
221dff13 | 549 | { |
e87c01c7 MH |
550 | #ifdef DISABLE_DNSSEC |
551 | return FALSE; | |
552 | #else | |
979c462e | 553 | return dnsa->answerlen >= 0 && ((const HEADER *)dnsa->answer)->aa; |
e87c01c7 | 554 | #endif |
221dff13 | 555 | } |
1f4a55da PP |
556 | |
557 | ||
558 | ||
059ec3d9 PH |
559 | /************************************************* |
560 | * Turn DNS type into text * | |
561 | *************************************************/ | |
562 | ||
885ccd3e PH |
563 | /* Turn the coded record type into a string for printing. All those that Exim |
564 | uses should be included here. | |
059ec3d9 PH |
565 | |
566 | Argument: record type | |
567 | Returns: pointer to string | |
568 | */ | |
569 | ||
570 | uschar * | |
571 | dns_text_type(int t) | |
572 | { | |
573 | switch(t) | |
574 | { | |
33397d19 PH |
575 | case T_A: return US"A"; |
576 | case T_MX: return US"MX"; | |
577 | case T_AAAA: return US"AAAA"; | |
578 | case T_A6: return US"A6"; | |
579 | case T_TXT: return US"TXT"; | |
eae0036b | 580 | case T_SPF: return US"SPF"; |
33397d19 | 581 | case T_PTR: return US"PTR"; |
885ccd3e | 582 | case T_SOA: return US"SOA"; |
33397d19 PH |
583 | case T_SRV: return US"SRV"; |
584 | case T_NS: return US"NS"; | |
8e669ac1 | 585 | case T_CNAME: return US"CNAME"; |
1e06383a | 586 | case T_TLSA: return US"TLSA"; |
33397d19 | 587 | default: return US"?"; |
059ec3d9 PH |
588 | } |
589 | } | |
590 | ||
591 | ||
592 | ||
593 | /************************************************* | |
594 | * Cache a failed DNS lookup result * | |
595 | *************************************************/ | |
596 | ||
cabf3e99 JH |
597 | static void |
598 | dns_fail_tag(uschar * buf, const uschar * name, int dns_type) | |
599 | { | |
600 | res_state resp = os_get_dns_resolver_res(); | |
7d8d08c4 JH |
601 | |
602 | /*XX buf needs to be 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1 | |
603 | We truncate the name here for safety... could use a dynamic string. */ | |
604 | ||
cabf3e99 JH |
605 | sprintf(CS buf, "%.255s-%s-%lx", name, dns_text_type(dns_type), |
606 | (unsigned long) resp->options); | |
607 | } | |
608 | ||
609 | ||
059ec3d9 PH |
610 | /* We cache failed lookup results so as not to experience timeouts many |
611 | times for the same domain. We need to retain the resolver options because they | |
612 | may change. For successful lookups, we rely on resolver and/or name server | |
613 | caching. | |
614 | ||
615 | Arguments: | |
616 | name the domain name | |
617 | type the lookup type | |
7d8d08c4 | 618 | expiry time TTL expires, or zero for unlimited |
059ec3d9 PH |
619 | rc the return code |
620 | ||
621 | Returns: the return code | |
622 | */ | |
623 | ||
3a2feed8 | 624 | /* we need: 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1 */ |
7d8d08c4 | 625 | #define DNS_FAILTAG_MAX 290 |
927e32d4 | 626 | #define DNS_FAILNODE_SIZE \ |
3a2feed8 | 627 | (sizeof(expiring_data) + sizeof(tree_node) + DNS_FAILTAG_MAX) |
7d8d08c4 JH |
628 | |
629 | static int | |
630 | dns_fail_return(const uschar * name, int type, time_t expiry, int rc) | |
631 | { | |
632 | uschar node_name[DNS_FAILTAG_MAX]; | |
633 | tree_node * previous, * new; | |
634 | expiring_data * e; | |
635 | ||
636 | dns_fail_tag(node_name, name, type); | |
637 | if ((previous = tree_search(tree_dns_fails, node_name))) | |
638 | e = previous->data.ptr; | |
639 | else | |
640 | { | |
3a2feed8 JH |
641 | e = store_get_perm(DNS_FAILNODE_SIZE, is_tainted(name)); |
642 | new = (void *)(e+1); | |
7d8d08c4 | 643 | dns_fail_tag(new->name, name, type); |
7d8d08c4 JH |
644 | new->data.ptr = e; |
645 | (void)tree_insertnode(&tree_dns_fails, new); | |
646 | } | |
647 | ||
648 | DEBUG(D_dns) debug_printf(" %s neg-cache entry for %s, ttl %d\n", | |
649 | previous ? "update" : "writing", | |
650 | node_name, expiry ? (int)(expiry - time(NULL)) : -1); | |
651 | e->expiry = expiry; | |
652 | e->data.val = rc; | |
653 | return rc; | |
654 | } | |
655 | ||
656 | ||
657 | /* Return the cached result of a known-bad lookup, or -1. | |
658 | */ | |
059ec3d9 | 659 | static int |
7d8d08c4 | 660 | dns_fail_cache_hit(const uschar * name, int type) |
059ec3d9 | 661 | { |
7d8d08c4 JH |
662 | uschar node_name[DNS_FAILTAG_MAX]; |
663 | tree_node * previous; | |
664 | expiring_data * e; | |
665 | int val, rc; | |
666 | ||
667 | dns_fail_tag(node_name, name, type); | |
668 | if (!(previous = tree_search(tree_dns_fails, node_name))) | |
669 | return -1; | |
670 | ||
671 | e = previous->data.ptr; | |
672 | val = e->data.val; | |
673 | rc = e->expiry && e->expiry <= time(NULL) ? -1 : val; | |
674 | ||
675 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: %scached value %s%s\n", | |
676 | name, dns_text_type(type), | |
677 | rc == -1 ? "" : "using ", | |
678 | val == DNS_NOMATCH ? "DNS_NOMATCH" : | |
679 | val == DNS_NODATA ? "DNS_NODATA" : | |
680 | val == DNS_AGAIN ? "DNS_AGAIN" : | |
681 | val == DNS_FAIL ? "DNS_FAIL" : "??", | |
682 | rc == -1 ? " past valid time" : ""); | |
683 | ||
059ec3d9 PH |
684 | return rc; |
685 | } | |
686 | ||
7d8d08c4 JH |
687 | |
688 | ||
7d8d08c4 JH |
689 | /* This is really gross. The successful return value from res_search() is |
690 | the packet length, which is stored in dnsa->answerlen. If we get a | |
691 | negative DNS reply then res_search() returns -1, which causes the bounds | |
692 | checks for name decompression to fail when it is treated as a packet | |
693 | length, which in turn causes the authority search to fail. The correct | |
694 | packet length has been lost inside libresolv, so we have to guess a | |
695 | replacement value. (The only way to fix this properly would be to | |
696 | re-implement res_search() and res_query() so that they don't muddle their | |
697 | success and packet length return values.) For added safety we only reset | |
698 | the packet length if the packet header looks plausible. */ | |
699 | ||
b574c5ba | 700 | static void |
a713f766 | 701 | fake_dnsa_len_for_fail(dns_answer * dnsa, int type) |
b574c5ba JH |
702 | { |
703 | const HEADER * h = (const HEADER *)dnsa->answer; | |
704 | ||
705 | if ( h->qr == 1 /* a response */ | |
706 | && h->opcode == QUERY | |
707 | && h->tc == 0 /* nmessage not truncated */ | |
7d8d08c4 | 708 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) |
b574c5ba JH |
709 | && ( ntohs(h->qdcount) == 1 /* one question record */ |
710 | || f.running_in_test_harness) | |
711 | && ntohs(h->ancount) == 0 /* no answer records */ | |
712 | && ntohs(h->nscount) >= 1) /* authority records */ | |
713 | { | |
a713f766 JH |
714 | DEBUG(D_dns) debug_printf("faking res_search(%s) response length as %d\n", |
715 | dns_text_type(type), (int)sizeof(dnsa->answer)); | |
b574c5ba JH |
716 | dnsa->answerlen = sizeof(dnsa->answer); |
717 | } | |
718 | } | |
719 | ||
720 | ||
721 | /* Return the TTL suitable for an NXDOMAIN result, which is given | |
722 | in the SOA. We hope that one was returned in the lookup, and do not | |
723 | bother doing a separate lookup; if not found return a forever TTL. | |
724 | */ | |
725 | ||
726 | time_t | |
a713f766 | 727 | dns_expire_from_soa(dns_answer * dnsa, int type) |
b574c5ba JH |
728 | { |
729 | dns_scan dnss; | |
730 | ||
a713f766 | 731 | fake_dnsa_len_for_fail(dnsa, type); |
7d8d08c4 JH |
732 | |
733 | for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
734 | rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) | |
735 | ) if (rr->type == T_SOA) | |
736 | { | |
737 | const uschar * p = rr->data; | |
738 | uschar discard_buf[256]; | |
739 | int len; | |
740 | unsigned long ttl; | |
741 | ||
742 | /* Skip the mname & rname strings */ | |
743 | ||
744 | if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
745 | p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0) | |
746 | break; | |
747 | p += len; | |
748 | if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
749 | p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0) | |
750 | break; | |
751 | p += len; | |
752 | ||
753 | /* Skip the SOA serial, refresh, retry & expire. Grab the TTL */ | |
754 | ||
d70fc283 | 755 | if (p > dnsa->answer + dnsa->answerlen - 5 * INT32SZ) |
7d8d08c4 | 756 | break; |
d70fc283 | 757 | p += 4 * INT32SZ; |
7d8d08c4 JH |
758 | GETLONG(ttl, p); |
759 | ||
760 | return time(NULL) + ttl; | |
761 | } | |
762 | DEBUG(D_dns) debug_printf("DNS: no SOA record found for neg-TTL\n"); | |
763 | return 0; | |
764 | } | |
765 | ||
766 | ||
059ec3d9 PH |
767 | /************************************************* |
768 | * Do basic DNS lookup * | |
769 | *************************************************/ | |
770 | ||
771 | /* Call the resolver to look up the given domain name, using the given type, | |
772 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
4c04137d | 773 | Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set |
059ec3d9 PH |
774 | up nameservers that produce this error continually, so there is the option of |
775 | providing a list of domains for which this is treated as a non-existent | |
776 | host. | |
777 | ||
75c121f0 JH |
778 | The dns_answer structure is pretty big; enough to hold a max-sized DNS message |
779 | - so best allocated from fast-release memory. As of writing, all our callers | |
780 | use a stack-auto variable. | |
781 | ||
059ec3d9 PH |
782 | Arguments: |
783 | dnsa pointer to dns_answer structure | |
784 | name name to look up | |
785 | type type of DNS record required (T_A, T_MX, etc) | |
786 | ||
787 | Returns: DNS_SUCCEED successful lookup | |
788 | DNS_NOMATCH name not found (NXDOMAIN) | |
789 | or name contains illegal characters (if checking) | |
30e18802 | 790 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
791 | DNS_NODATA domain exists, but no data for this type (NODATA) |
792 | DNS_AGAIN soft failure, try again later | |
793 | DNS_FAIL DNS failure | |
794 | */ | |
795 | ||
796 | int | |
7d8d08c4 | 797 | dns_basic_lookup(dns_answer * dnsa, const uschar * name, int type) |
059ec3d9 | 798 | { |
7d8d08c4 | 799 | int rc; |
059ec3d9 | 800 | #ifndef STAND_ALONE |
7d8d08c4 | 801 | const uschar * save_domain; |
059ec3d9 PH |
802 | #endif |
803 | ||
059ec3d9 PH |
804 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that |
805 | a timeout on one domain doesn't happen time and time again for messages that | |
806 | have many addresses in the same domain. We rely on the resolver and name server | |
7d8d08c4 JH |
807 | caching for successful lookups. |
808 | */ | |
059ec3d9 | 809 | |
7d8d08c4 | 810 | if ((rc = dns_fail_cache_hit(name, type)) > 0) |
979c462e JH |
811 | { |
812 | dnsa->answerlen = -1; | |
7d8d08c4 | 813 | return rc; |
979c462e | 814 | } |
059ec3d9 | 815 | |
8c5d388a | 816 | #ifdef SUPPORT_I18N |
9d4319df JH |
817 | /* Convert all names to a-label form before doing lookup */ |
818 | { | |
819 | uschar * alabel; | |
820 | uschar * errstr = NULL; | |
766e7a65 JH |
821 | DEBUG(D_dns) if (string_is_utf8(name)) |
822 | debug_printf("convert utf8 '%s' to alabel for for lookup\n", name); | |
9d4319df JH |
823 | if ((alabel = string_domain_utf8_to_alabel(name, &errstr)), errstr) |
824 | { | |
825 | DEBUG(D_dns) | |
37bf366e | 826 | debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name, |
9d4319df | 827 | errstr); |
8768d548 | 828 | f.host_find_failed_syntax = TRUE; |
9d4319df JH |
829 | return DNS_NOMATCH; |
830 | } | |
831 | name = alabel; | |
832 | } | |
833 | #endif | |
834 | ||
4c04137d | 835 | /* If configured, check the hygiene of the name passed to lookup. Otherwise, |
059ec3d9 PH |
836 | although DNS lookups may give REFUSED at the lower level, some resolvers |
837 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
838 | domains cannot be in the DNS. The check is now done by a regular expression; | |
839 | give it space for substring storage to save it having to get its own if the | |
840 | regex has substrings that are used - the default uses a conditional. | |
841 | ||
842 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
843 | lookup, which constructs the names itself, so they should be OK. Besides, | |
6219e0ec SA |
844 | bitstring labels don't conform to normal name syntax. (But they aren't used any |
845 | more.) */ | |
059ec3d9 PH |
846 | |
847 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
848 | ||
482d1455 | 849 | if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT) |
059ec3d9 | 850 | { |
059ec3d9 PH |
851 | int ovector[3*(EXPAND_MAXN+1)]; |
852 | ||
476be7e2 | 853 | dns_pattern_init(); |
6219e0ec | 854 | if (pcre_exec(regex_check_dns_names, NULL, CCS name, Ustrlen(name), |
d093f8e5 | 855 | 0, PCRE_EOPT, ovector, nelem(ovector)) < 0) |
059ec3d9 PH |
856 | { |
857 | DEBUG(D_dns) | |
858 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
859 | dns_text_type(type)); | |
8768d548 | 860 | f.host_find_failed_syntax = TRUE; |
059ec3d9 PH |
861 | return DNS_NOMATCH; |
862 | } | |
863 | } | |
864 | ||
865 | #endif /* STAND_ALONE */ | |
866 | ||
867 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
868 | number of bytes the message would need, so we need to check for this case. The |
869 | effect is to truncate overlong data. | |
870 | ||
30e18802 PH |
871 | On some systems, res_search() will recognize "A-for-A" queries and return |
872 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
873 | nameservers are also believed to do this. It is, of course, contrary to the | |
874 | specification of the DNS, so we lock it out. */ | |
875 | ||
cc00f4af | 876 | if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0) |
30e18802 PH |
877 | return DNS_NOMATCH; |
878 | ||
879 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
880 | (res_search), we call fakens_search(), which recognizes certain special |
881 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
882 | ||
979c462e | 883 | h_errno = 0; |
8768d548 | 884 | dnsa->answerlen = f.running_in_test_harness |
d093f8e5 JH |
885 | ? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer)) |
886 | : res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer)); | |
059ec3d9 | 887 | |
d093f8e5 | 888 | if (dnsa->answerlen > (int) sizeof(dnsa->answer)) |
80a47a2c | 889 | { |
9e7e0f6a JH |
890 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet" |
891 | " (size %d), truncating to %u.\n", | |
892 | name, dns_text_type(type), dnsa->answerlen, (unsigned int) sizeof(dnsa->answer)); | |
d093f8e5 | 893 | dnsa->answerlen = sizeof(dnsa->answer); |
80a47a2c | 894 | } |
059ec3d9 PH |
895 | |
896 | if (dnsa->answerlen < 0) switch (h_errno) | |
897 | { | |
898 | case HOST_NOT_FOUND: | |
4b0fe319 JH |
899 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" |
900 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
a713f766 | 901 | return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH); |
059ec3d9 PH |
902 | |
903 | case TRY_AGAIN: | |
4b0fe319 JH |
904 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", |
905 | name, dns_text_type(type)); | |
059ec3d9 | 906 | |
4b0fe319 | 907 | /* Cut this out for various test programs */ |
1dc92d5a | 908 | #ifndef STAND_ALONE |
4b0fe319 JH |
909 | save_domain = deliver_domain; |
910 | deliver_domain = string_copy(name); /* set $domain */ | |
911 | rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL, | |
912 | MCL_DOMAIN, TRUE, NULL); | |
913 | deliver_domain = save_domain; | |
914 | if (rc != OK) | |
915 | { | |
916 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
7d8d08c4 | 917 | return dns_fail_return(name, type, 0, DNS_AGAIN); |
4b0fe319 JH |
918 | } |
919 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
920 | "DNS_NOMATCH\n", name); | |
a713f766 | 921 | return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH); |
059ec3d9 | 922 | |
1dc92d5a | 923 | #else /* For stand-alone tests */ |
7d8d08c4 | 924 | return dns_fail_return(name, type, 0, DNS_AGAIN); |
1dc92d5a | 925 | #endif |
059ec3d9 PH |
926 | |
927 | case NO_RECOVERY: | |
4b0fe319 JH |
928 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" |
929 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
7d8d08c4 | 930 | return dns_fail_return(name, type, 0, DNS_FAIL); |
059ec3d9 PH |
931 | |
932 | case NO_DATA: | |
4b0fe319 JH |
933 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" |
934 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
a713f766 | 935 | return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NODATA); |
059ec3d9 PH |
936 | |
937 | default: | |
4b0fe319 JH |
938 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" |
939 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
7d8d08c4 | 940 | return dns_fail_return(name, type, 0, DNS_FAIL); |
059ec3d9 PH |
941 | } |
942 | ||
943 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
944 | name, dns_text_type(type)); | |
945 | ||
946 | return DNS_SUCCEED; | |
947 | } | |
948 | ||
949 | ||
950 | ||
951 | ||
952 | /************************************************ | |
953 | * Do a DNS lookup and handle CNAMES * | |
954 | ************************************************/ | |
955 | ||
956 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
957 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
958 | the DNS, but you are supposed to cope with them if you find them. | |
d8d9f930 JH |
959 | By default, follow one CNAME since a resolver has been seen, faced with |
960 | an MX request and a CNAME (to an A) but no MX present, returning the CNAME. | |
059ec3d9 PH |
961 | |
962 | The assumption is made that if the resolver gives back records of the | |
963 | requested type *and* a CNAME, we don't need to make another call to look up | |
964 | the CNAME. I can't see how it could return only some of the right records. If | |
965 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
966 | won't return any. | |
967 | ||
968 | If fully_qualified_name is not NULL, set it to point to the full name | |
969 | returned by the resolver, if this is different to what it is given, unless | |
970 | the returned name starts with "*" as some nameservers seem to be returning | |
766e7a65 JH |
971 | wildcards in this form. In international mode "different" means "alabel |
972 | forms are different". | |
059ec3d9 PH |
973 | |
974 | Arguments: | |
975 | dnsa pointer to dns_answer structure | |
976 | name domain name to look up | |
977 | type DNS record type (T_A, T_MX, etc) | |
978 | fully_qualified_name if not NULL, return the returned name here if its | |
979 | contents are different (i.e. it must be preset) | |
980 | ||
981 | Returns: DNS_SUCCEED successful lookup | |
982 | DNS_NOMATCH name not found | |
983 | DNS_NODATA no data found | |
984 | DNS_AGAIN soft failure, try again later | |
985 | DNS_FAIL DNS failure | |
986 | */ | |
987 | ||
988 | int | |
1dc92d5a | 989 | dns_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 990 | const uschar **fully_qualified_name) |
059ec3d9 | 991 | { |
1dc92d5a | 992 | const uschar *orig_name = name; |
c85b3043 | 993 | BOOL secure_so_far = TRUE; |
059ec3d9 | 994 | |
d8d9f930 JH |
995 | /* By default, assume the resolver follows CNAME chains (and returns NODATA for |
996 | an unterminated one). If it also does that for a CNAME loop, fine; if it returns | |
997 | a CNAME (maybe the last?) whine about it. However, retain the coding for dumb | |
998 | resolvers hiding behind a config variable. Loop to follow CNAME chains so far, | |
999 | but no further... The testsuite tests the latter case, mostly assuming that the | |
1000 | former will work. */ | |
059ec3d9 | 1001 | |
d7978c0f | 1002 | for (int i = 0; i <= dns_cname_loops; i++) |
059ec3d9 | 1003 | { |
806c3df9 | 1004 | uschar * data; |
d7978c0f | 1005 | dns_record cname_rr, type_rr; |
059ec3d9 | 1006 | dns_scan dnss; |
1b76ad22 | 1007 | int rc; |
059ec3d9 PH |
1008 | |
1009 | /* DNS lookup failures get passed straight back. */ | |
1010 | ||
dd708fd7 JH |
1011 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) |
1012 | return rc; | |
059ec3d9 PH |
1013 | |
1014 | /* We should have either records of the required type, or a CNAME record, | |
1015 | or both. We need to know whether both exist for getting the fully qualified | |
1016 | name, but avoid scanning more than necessary. Note that we must copy the | |
1017 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
1018 | area in the dnsa block. */ | |
1019 | ||
1020 | cname_rr.data = type_rr.data = NULL; | |
d7978c0f | 1021 | for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); |
8688d177 | 1022 | rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) |
059ec3d9 PH |
1023 | if (rr->type == type) |
1024 | { | |
1025 | if (type_rr.data == NULL) type_rr = *rr; | |
1026 | if (cname_rr.data != NULL) break; | |
1027 | } | |
dd708fd7 JH |
1028 | else if (rr->type == T_CNAME) |
1029 | cname_rr = *rr; | |
059ec3d9 | 1030 | |
a2042e78 PH |
1031 | /* For the first time round this loop, if a CNAME was found, take the fully |
1032 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 1033 | |
dd708fd7 | 1034 | if (i == 0 && fully_qualified_name) |
059ec3d9 | 1035 | { |
dd708fd7 JH |
1036 | uschar * rr_name = cname_rr.data |
1037 | ? cname_rr.name : type_rr.data ? type_rr.name : NULL; | |
766e7a65 JH |
1038 | if ( rr_name |
1039 | && Ustrcmp(rr_name, *fully_qualified_name) != 0 | |
1040 | && rr_name[0] != '*' | |
8c5d388a | 1041 | #ifdef SUPPORT_I18N |
766e7a65 JH |
1042 | && ( !string_is_utf8(*fully_qualified_name) |
1043 | || Ustrcmp(rr_name, | |
1044 | string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0 | |
1045 | ) | |
1046 | #endif | |
1047 | ) | |
1048 | *fully_qualified_name = string_copy_dnsdomain(rr_name); | |
059ec3d9 PH |
1049 | } |
1050 | ||
1051 | /* If any data records of the correct type were found, we are done. */ | |
1052 | ||
806c3df9 | 1053 | if (type_rr.data) |
c85b3043 JH |
1054 | { |
1055 | if (!secure_so_far) /* mark insecure if any element of CNAME chain was */ | |
4a142059 | 1056 | dns_set_insecure(dnsa); |
c85b3043 JH |
1057 | return DNS_SUCCEED; |
1058 | } | |
059ec3d9 PH |
1059 | |
1060 | /* If there are no data records, we need to re-scan the DNS using the | |
1061 | domain given in the CNAME record, which should exist (otherwise we should | |
1062 | have had a failure from dns_lookup). However code against the possibility of | |
1063 | its not existing. */ | |
1064 | ||
806c3df9 JH |
1065 | if (!cname_rr.data) |
1066 | return DNS_FAIL; | |
1067 | ||
f3ebb786 JH |
1068 | /* DNS data comes from the outside, hence tainted */ |
1069 | data = store_get(256, TRUE); | |
1b76ad22 JH |
1070 | if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, |
1071 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0) | |
806c3df9 | 1072 | return DNS_FAIL; |
059ec3d9 | 1073 | name = data; |
a2042e78 | 1074 | |
c85b3043 JH |
1075 | if (!dns_is_secure(dnsa)) |
1076 | secure_so_far = FALSE; | |
1077 | ||
a2042e78 | 1078 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); |
059ec3d9 PH |
1079 | } /* Loop back to do another lookup */ |
1080 | ||
1081 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
1082 | right... */ | |
1083 | ||
1084 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
1085 | return DNS_FAIL; | |
1086 | } | |
1087 | ||
1088 | ||
1089 | ||
33397d19 PH |
1090 | |
1091 | ||
1092 | ||
1093 | /************************************************ | |
1094 | * Do a DNS lookup and handle virtual types * | |
1095 | ************************************************/ | |
1096 | ||
9820a77f | 1097 | /* This function handles some invented "lookup types" that synthesize features |
8e669ac1 | 1098 | not available in the basic types. The special types all have negative values. |
33397d19 PH |
1099 | Positive type values are passed straight on to dns_lookup(). |
1100 | ||
1101 | Arguments: | |
1102 | dnsa pointer to dns_answer structure | |
1103 | name domain name to look up | |
1104 | type DNS record type (T_A, T_MX, etc or a "special") | |
1105 | fully_qualified_name if not NULL, return the returned name here if its | |
1106 | contents are different (i.e. it must be preset) | |
1107 | ||
1108 | Returns: DNS_SUCCEED successful lookup | |
1109 | DNS_NOMATCH name not found | |
1110 | DNS_NODATA no data found | |
1111 | DNS_AGAIN soft failure, try again later | |
1112 | DNS_FAIL DNS failure | |
1113 | */ | |
1114 | ||
1115 | int | |
1dc92d5a | 1116 | dns_special_lookup(dns_answer *dnsa, const uschar *name, int type, |
55414b25 | 1117 | const uschar **fully_qualified_name) |
33397d19 | 1118 | { |
d2a2c69b | 1119 | switch (type) |
e5a9dba6 | 1120 | { |
d2a2c69b JH |
1121 | /* The "mx hosts only" type doesn't require any special action here */ |
1122 | case T_MXH: | |
1705dd20 | 1123 | return dns_lookup(dnsa, name, T_MX, fully_qualified_name); |
d2a2c69b JH |
1124 | |
1125 | /* Find nameservers for the domain or the nearest enclosing zone, excluding | |
1126 | the root servers. */ | |
1127 | case T_ZNS: | |
1705dd20 JH |
1128 | type = T_NS; |
1129 | /* FALLTHROUGH */ | |
d2a2c69b | 1130 | case T_SOA: |
1705dd20 JH |
1131 | { |
1132 | const uschar *d = name; | |
1133 | while (d != 0) | |
1134 | { | |
1135 | int rc = dns_lookup(dnsa, d, type, fully_qualified_name); | |
1136 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
1137 | while (*d != 0 && *d != '.') d++; | |
1138 | if (*d++ == 0) break; | |
1139 | } | |
1140 | return DNS_NOMATCH; | |
1141 | } | |
d2a2c69b JH |
1142 | |
1143 | /* Try to look up the Client SMTP Authorization SRV record for the name. If | |
1144 | there isn't one, search from the top downwards for a CSA record in a parent | |
1145 | domain, which might be making assertions about subdomains. If we find a record | |
1146 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
1147 | can tell whether to look at the explicit authorization field or the subdomain | |
1148 | assertion field. */ | |
1149 | case T_CSA: | |
1705dd20 | 1150 | { |
cab0c277 | 1151 | uschar *srvname, *namesuff, *tld; |
1705dd20 JH |
1152 | int priority, weight, port; |
1153 | int limit, rc, i; | |
1154 | BOOL ipv6; | |
1155 | dns_record *rr; | |
1156 | dns_scan dnss; | |
1157 | ||
1158 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
1159 | ||
1160 | srvname = string_sprintf("_client._smtp.%s", name); | |
1161 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
1162 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
1163 | { | |
1164 | if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name); | |
1165 | return rc; | |
1166 | } | |
d2a2c69b | 1167 | |
1705dd20 JH |
1168 | /* Search for CSA subdomain assertion SRV records from the top downwards, |
1169 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
1170 | We skip the top level domains to avoid loading their nameservers and because | |
1171 | we know they'll never have CSA SRV records. */ | |
d2a2c69b | 1172 | |
1705dd20 JH |
1173 | namesuff = Ustrrchr(name, '.'); |
1174 | if (namesuff == NULL) return DNS_NOMATCH; | |
1175 | tld = namesuff + 1; | |
1176 | ipv6 = FALSE; | |
1177 | limit = dns_csa_search_limit; | |
1178 | ||
1179 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
1180 | ||
1181 | if (strcmpic(namesuff, US".arpa") == 0) | |
1182 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
1183 | { | |
1184 | namesuff -= 8; | |
d2a2c69b | 1185 | tld = namesuff + 1; |
1705dd20 JH |
1186 | limit = 3; |
1187 | } | |
1188 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
1189 | { | |
1190 | namesuff -= 4; | |
1191 | tld = namesuff + 1; | |
1192 | ipv6 = TRUE; | |
1193 | limit = 3; | |
1194 | } | |
d2a2c69b | 1195 | |
1705dd20 | 1196 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); |
d2a2c69b | 1197 | |
1705dd20 JH |
1198 | /* Do not perform the search if the top level or 2nd level domains do not |
1199 | exist. This is quite common, and when it occurs all the search queries would | |
1200 | go to the root or TLD name servers, which is not friendly. So we check the | |
1201 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
1202 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
1203 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
1204 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
1205 | ||
1206 | if (rc == DNS_NOMATCH) | |
1207 | { | |
a713f766 | 1208 | fake_dnsa_len_for_fail(dnsa, T_CSA); |
1705dd20 JH |
1209 | |
1210 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
8688d177 | 1211 | rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) |
1705dd20 JH |
1212 | ) |
1213 | if (rr->type != T_SOA) continue; | |
1214 | else if (strcmpic(rr->name, US"") == 0 || | |
1215 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
1216 | else break; | |
1217 | } | |
d2a2c69b | 1218 | |
1705dd20 JH |
1219 | for (i = 0; i < limit; i++) |
1220 | { | |
1221 | if (ipv6) | |
1222 | { | |
1223 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
1224 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
1225 | namesuff -= 8; | |
1226 | if (namesuff <= name) return DNS_NOMATCH; | |
1227 | } | |
1228 | else | |
1229 | /* Find the start of the preceding domain name label. */ | |
1230 | do | |
1231 | if (--namesuff <= name) return DNS_NOMATCH; | |
1232 | while (*namesuff != '.'); | |
1233 | ||
1234 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
1235 | ||
1236 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
1237 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
1238 | if (rc == DNS_AGAIN) return rc; | |
1239 | if (rc != DNS_SUCCEED) continue; | |
1240 | ||
1241 | /* Check that the SRV record we have found is worth returning. We don't | |
1242 | just return the first one we find, because some lower level SRV record | |
1243 | might make stricter assertions than its parent domain. */ | |
1244 | ||
1245 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
8688d177 | 1246 | rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == T_SRV) |
1705dd20 | 1247 | { |
dd708fd7 | 1248 | const uschar * p = rr->data; |
d2a2c69b | 1249 | |
1705dd20 | 1250 | /* Extract the numerical SRV fields (p is incremented) */ |
1705dd20 JH |
1251 | GETSHORT(priority, p); |
1252 | GETSHORT(weight, p); weight = weight; /* compiler quietening */ | |
1253 | GETSHORT(port, p); | |
d2a2c69b | 1254 | |
1705dd20 JH |
1255 | /* Check the CSA version number */ |
1256 | if (priority != 1) continue; | |
d2a2c69b | 1257 | |
1705dd20 JH |
1258 | /* If it's making an interesting assertion, return this response. */ |
1259 | if (port & 1) | |
d2a2c69b | 1260 | { |
1705dd20 JH |
1261 | *fully_qualified_name = namesuff + 1; |
1262 | return DNS_SUCCEED; | |
d2a2c69b | 1263 | } |
d2a2c69b | 1264 | } |
1705dd20 JH |
1265 | } |
1266 | return DNS_NOMATCH; | |
1267 | } | |
e5a9dba6 | 1268 | |
d2a2c69b | 1269 | default: |
1705dd20 JH |
1270 | if (type >= 0) |
1271 | return dns_lookup(dnsa, name, type, fully_qualified_name); | |
e5a9dba6 PH |
1272 | } |
1273 | ||
33397d19 PH |
1274 | /* Control should never reach here */ |
1275 | ||
1276 | return DNS_FAIL; | |
1277 | } | |
1278 | ||
1279 | ||
1280 | ||
059ec3d9 PH |
1281 | |
1282 | ||
1283 | /************************************************* | |
1284 | * Get address(es) from DNS record * | |
1285 | *************************************************/ | |
1286 | ||
d57d474f | 1287 | /* The record type is either T_A for an IPv4 address or T_AAAA for an IPv6 address. |
059ec3d9 PH |
1288 | |
1289 | Argument: | |
1290 | dnsa the DNS answer block | |
1291 | rr the RR | |
1292 | ||
e1a3f32f | 1293 | Returns: pointer to a chain of dns_address items; NULL when the dnsa was overrun |
059ec3d9 PH |
1294 | */ |
1295 | ||
1296 | dns_address * | |
1297 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1298 | { | |
e1a3f32f JH |
1299 | dns_address * yield = NULL; |
1300 | uschar * dnsa_lim = dnsa->answer + dnsa->answerlen; | |
059ec3d9 PH |
1301 | |
1302 | if (rr->type == T_A) | |
1303 | { | |
d2a2c69b | 1304 | uschar *p = US rr->data; |
e1a3f32f JH |
1305 | if (p + 4 <= dnsa_lim) |
1306 | { | |
f3ebb786 JH |
1307 | /* the IP is not regarded as tainted */ |
1308 | yield = store_get(sizeof(dns_address) + 20, FALSE); | |
e1a3f32f JH |
1309 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); |
1310 | yield->next = NULL; | |
1311 | } | |
059ec3d9 PH |
1312 | } |
1313 | ||
1314 | #if HAVE_IPV6 | |
1315 | ||
059ec3d9 PH |
1316 | else |
1317 | { | |
e1a3f32f JH |
1318 | if (rr->data + 16 <= dnsa_lim) |
1319 | { | |
d57d474f | 1320 | struct in6_addr in6; |
d7978c0f | 1321 | for (int i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i]; |
f3ebb786 | 1322 | yield = store_get(sizeof(dns_address) + 50, FALSE); |
d57d474f | 1323 | inet_ntop(AF_INET6, &in6, CS yield->address, 50); |
e1a3f32f JH |
1324 | yield->next = NULL; |
1325 | } | |
059ec3d9 PH |
1326 | } |
1327 | #endif /* HAVE_IPV6 */ | |
1328 | ||
1329 | return yield; | |
1330 | } | |
1331 | ||
476be7e2 JH |
1332 | |
1333 | ||
1334 | void | |
1335 | dns_pattern_init(void) | |
1336 | { | |
1337 | if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names) | |
1338 | regex_check_dns_names = | |
1339 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
1340 | } | |
1341 | ||
8c51eead JH |
1342 | /* vi: aw ai sw=2 |
1343 | */ | |
059ec3d9 | 1344 | /* End of dns.c */ |