1 /*
2 * iterator/iter_scrub.c - scrubbing, normalization, sanitization of DNS msgs.
3 *
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
5 *
6 * This software is open source.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
14 *
15 * Redistributions in binary form must reproduce the above copyright notice,
16 * this list of conditions and the following disclaimer in the documentation
17 * and/or other materials provided with the distribution.
18 *
19 * Neither the name of the NLNET LABS nor the names of its contributors may
20 * be used to endorse or promote products derived from this software without
21 * specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
29 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36 /**
37 * \file
38 *
39 * This file has routine(s) for cleaning up incoming DNS messages from
40 * possible useless or malicious junk in it.
41 */
42 #include "config.h"
43 #include "iterator/iter_scrub.h"
44 #include "iterator/iterator.h"
45 #include "iterator/iter_priv.h"
46 #include "services/cache/rrset.h"
47 #include "util/log.h"
48 #include "util/net_help.h"
49 #include "util/regional.h"
50 #include "util/config_file.h"
51 #include "util/module.h"
52 #include "util/data/msgparse.h"
53 #include "util/data/dname.h"
54 #include "util/data/msgreply.h"
55 #include "util/alloc.h"
56 #include "sldns/sbuffer.h"
57
58 /** RRset flag used during scrubbing. The RRset is OK. */
59 #define RRSET_SCRUB_OK 0x80
60
61 /** remove rrset, update loop variables */
62 static void
remove_rrset(const char * str,sldns_buffer * pkt,struct msg_parse * msg,struct rrset_parse * prev,struct rrset_parse ** rrset)63 remove_rrset(const char* str, sldns_buffer* pkt, struct msg_parse* msg,
64 struct rrset_parse* prev, struct rrset_parse** rrset)
65 {
66 if(verbosity >= VERB_QUERY && str
67 && (*rrset)->dname_len <= LDNS_MAX_DOMAINLEN) {
68 uint8_t buf[LDNS_MAX_DOMAINLEN+1];
69 dname_pkt_copy(pkt, buf, (*rrset)->dname);
70 log_nametypeclass(VERB_QUERY, str, buf,
71 (*rrset)->type, ntohs((*rrset)->rrset_class));
72 }
73 if(prev)
74 prev->rrset_all_next = (*rrset)->rrset_all_next;
75 else msg->rrset_first = (*rrset)->rrset_all_next;
76 if(msg->rrset_last == *rrset)
77 msg->rrset_last = prev;
78 msg->rrset_count --;
79 switch((*rrset)->section) {
80 case LDNS_SECTION_ANSWER: msg->an_rrsets--; break;
81 case LDNS_SECTION_AUTHORITY: msg->ns_rrsets--; break;
82 case LDNS_SECTION_ADDITIONAL: msg->ar_rrsets--; break;
83 default: log_assert(0);
84 }
85 msgparse_bucket_remove(msg, *rrset);
86 *rrset = (*rrset)->rrset_all_next;
87 }
88
89 /** return true if rr type has additional names in it */
90 static int
has_additional(uint16_t t)91 has_additional(uint16_t t)
92 {
93 switch(t) {
94 case LDNS_RR_TYPE_MB:
95 case LDNS_RR_TYPE_MD:
96 case LDNS_RR_TYPE_MF:
97 case LDNS_RR_TYPE_NS:
98 case LDNS_RR_TYPE_MX:
99 case LDNS_RR_TYPE_KX:
100 case LDNS_RR_TYPE_SRV:
101 return 1;
102 case LDNS_RR_TYPE_NAPTR:
103 /* TODO: NAPTR not supported, glue stripped off */
104 return 0;
105 }
106 return 0;
107 }
108
109 /** get additional name from rrset RR, return false if no name present */
110 static int
get_additional_name(struct rrset_parse * rrset,struct rr_parse * rr,uint8_t ** nm,size_t * nmlen,sldns_buffer * pkt)111 get_additional_name(struct rrset_parse* rrset, struct rr_parse* rr,
112 uint8_t** nm, size_t* nmlen, sldns_buffer* pkt)
113 {
114 size_t offset = 0;
115 size_t len, oldpos;
116 switch(rrset->type) {
117 case LDNS_RR_TYPE_MB:
118 case LDNS_RR_TYPE_MD:
119 case LDNS_RR_TYPE_MF:
120 case LDNS_RR_TYPE_NS:
121 offset = 0;
122 break;
123 case LDNS_RR_TYPE_MX:
124 case LDNS_RR_TYPE_KX:
125 offset = 2;
126 break;
127 case LDNS_RR_TYPE_SRV:
128 offset = 6;
129 break;
130 case LDNS_RR_TYPE_NAPTR:
131 /* TODO: NAPTR not supported, glue stripped off */
132 return 0;
133 default:
134 return 0;
135 }
136 len = sldns_read_uint16(rr->ttl_data+sizeof(uint32_t));
137 if(len < offset+1)
138 return 0; /* rdata field too small */
139 *nm = rr->ttl_data+sizeof(uint32_t)+sizeof(uint16_t)+offset;
140 oldpos = sldns_buffer_position(pkt);
141 sldns_buffer_set_position(pkt, (size_t)(*nm - sldns_buffer_begin(pkt)));
142 *nmlen = pkt_dname_len(pkt);
143 sldns_buffer_set_position(pkt, oldpos);
144 if(*nmlen == 0)
145 return 0;
146 return 1;
147 }
148
149 /** Place mark on rrsets in additional section they are OK */
150 static void
mark_additional_rrset(sldns_buffer * pkt,struct msg_parse * msg,struct rrset_parse * rrset)151 mark_additional_rrset(sldns_buffer* pkt, struct msg_parse* msg,
152 struct rrset_parse* rrset)
153 {
154 /* Mark A and AAAA for NS as appropriate additional section info. */
155 uint8_t* nm = NULL;
156 size_t nmlen = 0;
157 struct rr_parse* rr;
158
159 if(!has_additional(rrset->type))
160 return;
161 for(rr = rrset->rr_first; rr; rr = rr->next) {
162 if(get_additional_name(rrset, rr, &nm, &nmlen, pkt)) {
163 /* mark A */
164 hashvalue_type h = pkt_hash_rrset(pkt, nm,
165 LDNS_RR_TYPE_A, rrset->rrset_class, 0);
166 struct rrset_parse* r = msgparse_hashtable_lookup(
167 msg, pkt, h, 0, nm, nmlen,
168 LDNS_RR_TYPE_A, rrset->rrset_class);
169 if(r && r->section == LDNS_SECTION_ADDITIONAL) {
170 r->flags |= RRSET_SCRUB_OK;
171 }
172
173 /* mark AAAA */
174 h = pkt_hash_rrset(pkt, nm, LDNS_RR_TYPE_AAAA,
175 rrset->rrset_class, 0);
176 r = msgparse_hashtable_lookup(msg, pkt, h, 0, nm,
177 nmlen, LDNS_RR_TYPE_AAAA, rrset->rrset_class);
178 if(r && r->section == LDNS_SECTION_ADDITIONAL) {
179 r->flags |= RRSET_SCRUB_OK;
180 }
181 }
182 }
183 }
184
185 /** Get target name of a CNAME */
186 static int
parse_get_cname_target(struct rrset_parse * rrset,uint8_t ** sname,size_t * snamelen,sldns_buffer * pkt)187 parse_get_cname_target(struct rrset_parse* rrset, uint8_t** sname,
188 size_t* snamelen, sldns_buffer* pkt)
189 {
190 size_t oldpos, dlen;
191 if(rrset->rr_count != 1) {
192 struct rr_parse* sig;
193 verbose(VERB_ALGO, "Found CNAME rrset with "
194 "size > 1: %u", (unsigned)rrset->rr_count);
195 /* use the first CNAME! */
196 rrset->rr_count = 1;
197 rrset->size = rrset->rr_first->size;
198 for(sig=rrset->rrsig_first; sig; sig=sig->next)
199 rrset->size += sig->size;
200 rrset->rr_last = rrset->rr_first;
201 rrset->rr_first->next = NULL;
202 }
203 if(rrset->rr_first->size < sizeof(uint16_t)+1)
204 return 0; /* CNAME rdata too small */
205 *sname = rrset->rr_first->ttl_data + sizeof(uint32_t)
206 + sizeof(uint16_t); /* skip ttl, rdatalen */
207 *snamelen = rrset->rr_first->size - sizeof(uint16_t);
208
209 if(rrset->rr_first->outside_packet) {
210 if(!dname_valid(*sname, *snamelen))
211 return 0;
212 return 1;
213 }
214 oldpos = sldns_buffer_position(pkt);
215 sldns_buffer_set_position(pkt, (size_t)(*sname - sldns_buffer_begin(pkt)));
216 dlen = pkt_dname_len(pkt);
217 sldns_buffer_set_position(pkt, oldpos);
218 if(dlen == 0)
219 return 0; /* parse fail on the rdata name */
220 *snamelen = dlen;
221 return 1;
222 }
223
224 /** Synthesize CNAME from DNAME, false if too long */
225 static int
synth_cname(uint8_t * qname,size_t qnamelen,struct rrset_parse * dname_rrset,uint8_t * alias,size_t * aliaslen,sldns_buffer * pkt)226 synth_cname(uint8_t* qname, size_t qnamelen, struct rrset_parse* dname_rrset,
227 uint8_t* alias, size_t* aliaslen, sldns_buffer* pkt)
228 {
229 /* we already know that sname is a strict subdomain of DNAME owner */
230 uint8_t* dtarg = NULL;
231 size_t dtarglen;
232 if(!parse_get_cname_target(dname_rrset, &dtarg, &dtarglen, pkt))
233 return 0;
234 if(qnamelen <= dname_rrset->dname_len)
235 return 0;
236 if(qnamelen == 0)
237 return 0;
238 log_assert(qnamelen > dname_rrset->dname_len);
239 /* DNAME from com. to net. with qname example.com. -> example.net. */
240 /* so: \3com\0 to \3net\0 and qname \7example\3com\0 */
241 *aliaslen = qnamelen + dtarglen - dname_rrset->dname_len;
242 if(*aliaslen > LDNS_MAX_DOMAINLEN)
243 return 0; /* should have been RCODE YXDOMAIN */
244 /* decompress dnames into buffer, we know it fits */
245 dname_pkt_copy(pkt, alias, qname);
246 dname_pkt_copy(pkt, alias+(qnamelen-dname_rrset->dname_len), dtarg);
247 return 1;
248 }
249
250 /** synthesize a CNAME rrset */
251 static struct rrset_parse*
synth_cname_rrset(uint8_t ** sname,size_t * snamelen,uint8_t * alias,size_t aliaslen,struct regional * region,struct msg_parse * msg,struct rrset_parse * rrset,struct rrset_parse * prev,struct rrset_parse * nx,sldns_buffer * pkt)252 synth_cname_rrset(uint8_t** sname, size_t* snamelen, uint8_t* alias,
253 size_t aliaslen, struct regional* region, struct msg_parse* msg,
254 struct rrset_parse* rrset, struct rrset_parse* prev,
255 struct rrset_parse* nx, sldns_buffer* pkt)
256 {
257 struct rrset_parse* cn = (struct rrset_parse*)regional_alloc(region,
258 sizeof(struct rrset_parse));
259 if(!cn)
260 return NULL;
261 memset(cn, 0, sizeof(*cn));
262 cn->rr_first = (struct rr_parse*)regional_alloc(region,
263 sizeof(struct rr_parse));
264 if(!cn->rr_first)
265 return NULL;
266 cn->rr_last = cn->rr_first;
267 /* CNAME from sname to alias */
268 cn->dname = (uint8_t*)regional_alloc(region, *snamelen);
269 if(!cn->dname)
270 return NULL;
271 dname_pkt_copy(pkt, cn->dname, *sname);
272 cn->dname_len = *snamelen;
273 cn->type = LDNS_RR_TYPE_CNAME;
274 cn->section = rrset->section;
275 cn->rrset_class = rrset->rrset_class;
276 cn->rr_count = 1;
277 cn->size = sizeof(uint16_t) + aliaslen;
278 cn->hash=pkt_hash_rrset(pkt, cn->dname, cn->type, cn->rrset_class, 0);
279 /* allocate TTL + rdatalen + uncompressed dname */
280 memset(cn->rr_first, 0, sizeof(struct rr_parse));
281 cn->rr_first->outside_packet = 1;
282 cn->rr_first->ttl_data = (uint8_t*)regional_alloc(region,
283 sizeof(uint32_t)+sizeof(uint16_t)+aliaslen);
284 if(!cn->rr_first->ttl_data)
285 return NULL;
286 sldns_write_uint32(cn->rr_first->ttl_data, 0); /* TTL = 0 */
287 sldns_write_uint16(cn->rr_first->ttl_data+4, aliaslen);
288 memmove(cn->rr_first->ttl_data+6, alias, aliaslen);
289 cn->rr_first->size = sizeof(uint16_t)+aliaslen;
290
291 /* link it in */
292 cn->rrset_all_next = nx;
293 if(prev)
294 prev->rrset_all_next = cn;
295 else msg->rrset_first = cn;
296 if(nx == NULL)
297 msg->rrset_last = cn;
298 msg->rrset_count ++;
299 msg->an_rrsets++;
300 /* it is not inserted in the msg hashtable. */
301
302 *sname = cn->rr_first->ttl_data + sizeof(uint32_t)+sizeof(uint16_t);
303 *snamelen = aliaslen;
304 return cn;
305 }
306
307 /** check if DNAME applies to a name */
308 static int
pkt_strict_sub(sldns_buffer * pkt,uint8_t * sname,uint8_t * dr)309 pkt_strict_sub(sldns_buffer* pkt, uint8_t* sname, uint8_t* dr)
310 {
311 uint8_t buf1[LDNS_MAX_DOMAINLEN+1];
312 uint8_t buf2[LDNS_MAX_DOMAINLEN+1];
313 /* decompress names */
314 dname_pkt_copy(pkt, buf1, sname);
315 dname_pkt_copy(pkt, buf2, dr);
316 return dname_strict_subdomain_c(buf1, buf2);
317 }
318
319 /** check subdomain with decompression */
320 static int
pkt_sub(sldns_buffer * pkt,uint8_t * comprname,uint8_t * zone)321 pkt_sub(sldns_buffer* pkt, uint8_t* comprname, uint8_t* zone)
322 {
323 uint8_t buf[LDNS_MAX_DOMAINLEN+1];
324 dname_pkt_copy(pkt, buf, comprname);
325 return dname_subdomain_c(buf, zone);
326 }
327
328 /** check subdomain with decompression, compressed is parent */
329 static int
sub_of_pkt(sldns_buffer * pkt,uint8_t * zone,uint8_t * comprname)330 sub_of_pkt(sldns_buffer* pkt, uint8_t* zone, uint8_t* comprname)
331 {
332 uint8_t buf[LDNS_MAX_DOMAINLEN+1];
333 dname_pkt_copy(pkt, buf, comprname);
334 return dname_subdomain_c(zone, buf);
335 }
336
337 /** Check if there are SOA records in the authority section (negative) */
338 static int
soa_in_auth(struct msg_parse * msg)339 soa_in_auth(struct msg_parse* msg)
340 {
341 struct rrset_parse* rrset;
342 for(rrset = msg->rrset_first; rrset; rrset = rrset->rrset_all_next)
343 if(rrset->type == LDNS_RR_TYPE_SOA &&
344 rrset->section == LDNS_SECTION_AUTHORITY)
345 return 1;
346 return 0;
347 }
348
349 /** Check if type is allowed in the authority section */
350 static int
type_allowed_in_authority_section(uint16_t tp)351 type_allowed_in_authority_section(uint16_t tp)
352 {
353 if(tp == LDNS_RR_TYPE_SOA || tp == LDNS_RR_TYPE_NS ||
354 tp == LDNS_RR_TYPE_DS || tp == LDNS_RR_TYPE_NSEC ||
355 tp == LDNS_RR_TYPE_NSEC3)
356 return 1;
357 return 0;
358 }
359
360 /** Check if type is allowed in the additional section */
361 static int
type_allowed_in_additional_section(uint16_t tp)362 type_allowed_in_additional_section(uint16_t tp)
363 {
364 if(tp == LDNS_RR_TYPE_A || tp == LDNS_RR_TYPE_AAAA)
365 return 1;
366 return 0;
367 }
368
369 /**
370 * This routine normalizes a response. This includes removing "irrelevant"
371 * records from the answer and additional sections and (re)synthesizing
372 * CNAMEs from DNAMEs, if present.
373 *
374 * @param pkt: packet.
375 * @param msg: msg to normalize.
376 * @param qinfo: original query.
377 * @param region: where to allocate synthesized CNAMEs.
378 * @param env: module env with config options.
379 * @return 0 on error.
380 */
381 static int
scrub_normalize(sldns_buffer * pkt,struct msg_parse * msg,struct query_info * qinfo,struct regional * region,struct module_env * env)382 scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg,
383 struct query_info* qinfo, struct regional* region,
384 struct module_env* env)
385 {
386 uint8_t* sname = qinfo->qname;
387 size_t snamelen = qinfo->qname_len;
388 struct rrset_parse* rrset, *prev, *nsset=NULL;
389
390 if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR &&
391 FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN)
392 return 1;
393
394 /* For the ANSWER section, remove all "irrelevant" records and add
395 * synthesized CNAMEs from DNAMEs
396 * This will strip out-of-order CNAMEs as well. */
397
398 /* walk through the parse packet rrset list, keep track of previous
399 * for insert and delete ease, and examine every RRset */
400 prev = NULL;
401 rrset = msg->rrset_first;
402 while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
403 if(rrset->type == LDNS_RR_TYPE_DNAME &&
404 pkt_strict_sub(pkt, sname, rrset->dname)) {
405 /* check if next rrset is correct CNAME. else,
406 * synthesize a CNAME */
407 struct rrset_parse* nx = rrset->rrset_all_next;
408 uint8_t alias[LDNS_MAX_DOMAINLEN+1];
409 size_t aliaslen = 0;
410 if(rrset->rr_count != 1) {
411 verbose(VERB_ALGO, "Found DNAME rrset with "
412 "size > 1: %u",
413 (unsigned)rrset->rr_count);
414 return 0;
415 }
416 if(!synth_cname(sname, snamelen, rrset, alias,
417 &aliaslen, pkt)) {
418 verbose(VERB_ALGO, "synthesized CNAME "
419 "too long");
420 return 0;
421 }
422 if(nx && nx->type == LDNS_RR_TYPE_CNAME &&
423 dname_pkt_compare(pkt, sname, nx->dname) == 0) {
424 /* check next cname */
425 uint8_t* t = NULL;
426 size_t tlen = 0;
427 if(!parse_get_cname_target(nx, &t, &tlen, pkt))
428 return 0;
429 if(dname_pkt_compare(pkt, alias, t) == 0) {
430 /* it's OK and better capitalized */
431 prev = rrset;
432 rrset = nx;
433 continue;
434 }
435 /* synth ourselves */
436 }
437 /* synth a CNAME rrset */
438 prev = synth_cname_rrset(&sname, &snamelen, alias,
439 aliaslen, region, msg, rrset, rrset, nx, pkt);
440 if(!prev) {
441 log_err("out of memory synthesizing CNAME");
442 return 0;
443 }
444 /* FIXME: resolve the conflict between synthesized
445 * CNAME ttls and the cache. */
446 rrset = nx;
447 continue;
448
449 }
450
451 /* The only records in the ANSWER section not allowed to */
452 if(dname_pkt_compare(pkt, sname, rrset->dname) != 0) {
453 remove_rrset("normalize: removing irrelevant RRset:",
454 pkt, msg, prev, &rrset);
455 continue;
456 }
457
458 /* Follow the CNAME chain. */
459 if(rrset->type == LDNS_RR_TYPE_CNAME) {
460 struct rrset_parse* nx = rrset->rrset_all_next;
461 uint8_t* oldsname = sname;
462 /* see if the next one is a DNAME, if so, swap them */
463 if(nx && nx->section == LDNS_SECTION_ANSWER &&
464 nx->type == LDNS_RR_TYPE_DNAME &&
465 nx->rr_count == 1 &&
466 pkt_strict_sub(pkt, sname, nx->dname)) {
467 /* there is a DNAME after this CNAME, it
468 * is in the ANSWER section, and the DNAME
469 * applies to the name we cover */
470 /* check if the alias of the DNAME equals
471 * this CNAME */
472 uint8_t alias[LDNS_MAX_DOMAINLEN+1];
473 size_t aliaslen = 0;
474 uint8_t* t = NULL;
475 size_t tlen = 0;
476 if(synth_cname(sname, snamelen, nx, alias,
477 &aliaslen, pkt) &&
478 parse_get_cname_target(rrset, &t, &tlen, pkt) &&
479 dname_pkt_compare(pkt, alias, t) == 0) {
480 /* the synthesized CNAME equals the
481 * current CNAME. This CNAME is the
482 * one that the DNAME creates, and this
483 * CNAME is better capitalised */
484 verbose(VERB_ALGO, "normalize: re-order of DNAME and its CNAME");
485 if(prev) prev->rrset_all_next = nx;
486 else msg->rrset_first = nx;
487 if(nx->rrset_all_next == NULL)
488 msg->rrset_last = rrset;
489 rrset->rrset_all_next =
490 nx->rrset_all_next;
491 nx->rrset_all_next = rrset;
492 /* prev = nx; unused, enable if there
493 * is other rrset removal code after
494 * this */
495 }
496 }
497
498 /* move to next name in CNAME chain */
499 if(!parse_get_cname_target(rrset, &sname, &snamelen, pkt))
500 return 0;
501 prev = rrset;
502 rrset = rrset->rrset_all_next;
503 /* in CNAME ANY response, can have data after CNAME */
504 if(qinfo->qtype == LDNS_RR_TYPE_ANY) {
505 while(rrset && rrset->section ==
506 LDNS_SECTION_ANSWER &&
507 dname_pkt_compare(pkt, oldsname,
508 rrset->dname) == 0) {
509 prev = rrset;
510 rrset = rrset->rrset_all_next;
511 }
512 }
513 continue;
514 }
515
516 /* Otherwise, make sure that the RRset matches the qtype. */
517 if(qinfo->qtype != LDNS_RR_TYPE_ANY &&
518 qinfo->qtype != rrset->type) {
519 remove_rrset("normalize: removing irrelevant RRset:",
520 pkt, msg, prev, &rrset);
521 continue;
522 }
523
524 /* Mark the additional names from relevant rrset as OK. */
525 /* only for RRsets that match the query name, other ones
526 * will be removed by sanitize, so no additional for them */
527 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0)
528 mark_additional_rrset(pkt, msg, rrset);
529
530 prev = rrset;
531 rrset = rrset->rrset_all_next;
532 }
533
534 /* Mark additional names from AUTHORITY */
535 while(rrset && rrset->section == LDNS_SECTION_AUTHORITY) {
536 /* protect internals of recursor by making sure to del these */
537 if(rrset->type==LDNS_RR_TYPE_DNAME ||
538 rrset->type==LDNS_RR_TYPE_CNAME ||
539 rrset->type==LDNS_RR_TYPE_A ||
540 rrset->type==LDNS_RR_TYPE_AAAA) {
541 remove_rrset("normalize: removing irrelevant "
542 "RRset:", pkt, msg, prev, &rrset);
543 continue;
544 }
545 /* Allowed list of types in the authority section */
546 if(env->cfg->harden_unknown_additional &&
547 !type_allowed_in_authority_section(rrset->type)) {
548 remove_rrset("normalize: removing irrelevant "
549 "RRset:", pkt, msg, prev, &rrset);
550 continue;
551 }
552 /* only one NS set allowed in authority section */
553 if(rrset->type==LDNS_RR_TYPE_NS) {
554 /* NS set must be pertinent to the query */
555 if(!sub_of_pkt(pkt, qinfo->qname, rrset->dname)) {
556 remove_rrset("normalize: removing irrelevant "
557 "RRset:", pkt, msg, prev, &rrset);
558 continue;
559 }
560 /* we don't want NS sets for NXDOMAIN answers,
561 * because they could contain poisonous contents,
562 * from. eg. fragmentation attacks, inserted after
563 * long RRSIGs in the packet get to the packet
564 * border and such */
565 /* also for NODATA answers */
566 if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN ||
567 (FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR
568 && soa_in_auth(msg) && msg->an_rrsets == 0)) {
569 remove_rrset("normalize: removing irrelevant "
570 "RRset:", pkt, msg, prev, &rrset);
571 continue;
572 }
573 if(nsset == NULL) {
574 nsset = rrset;
575 } else {
576 remove_rrset("normalize: removing irrelevant "
577 "RRset:", pkt, msg, prev, &rrset);
578 continue;
579 }
580 }
581 /* if this is type DS and we query for type DS we just got
582 * a referral answer for our type DS query, fix packet */
583 if(rrset->type==LDNS_RR_TYPE_DS &&
584 qinfo->qtype == LDNS_RR_TYPE_DS &&
585 dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0) {
586 rrset->section = LDNS_SECTION_ANSWER;
587 msg->ancount = rrset->rr_count + rrset->rrsig_count;
588 msg->nscount = 0;
589 msg->arcount = 0;
590 msg->an_rrsets = 1;
591 msg->ns_rrsets = 0;
592 msg->ar_rrsets = 0;
593 msg->rrset_count = 1;
594 msg->rrset_first = rrset;
595 msg->rrset_last = rrset;
596 rrset->rrset_all_next = NULL;
597 return 1;
598 }
599 mark_additional_rrset(pkt, msg, rrset);
600 prev = rrset;
601 rrset = rrset->rrset_all_next;
602 }
603
604 /* For each record in the additional section, remove it if it is an
605 * address record and not in the collection of additional names
606 * found in ANSWER and AUTHORITY. */
607 /* These records have not been marked OK previously */
608 while(rrset && rrset->section == LDNS_SECTION_ADDITIONAL) {
609 if(rrset->type==LDNS_RR_TYPE_A ||
610 rrset->type==LDNS_RR_TYPE_AAAA)
611 {
612 if((rrset->flags & RRSET_SCRUB_OK)) {
613 /* remove flag to clean up flags variable */
614 rrset->flags &= ~RRSET_SCRUB_OK;
615 } else {
616 remove_rrset("normalize: removing irrelevant "
617 "RRset:", pkt, msg, prev, &rrset);
618 continue;
619 }
620 }
621 /* protect internals of recursor by making sure to del these */
622 if(rrset->type==LDNS_RR_TYPE_DNAME ||
623 rrset->type==LDNS_RR_TYPE_CNAME ||
624 rrset->type==LDNS_RR_TYPE_NS) {
625 remove_rrset("normalize: removing irrelevant "
626 "RRset:", pkt, msg, prev, &rrset);
627 continue;
628 }
629 /* Allowed list of types in the additional section */
630 if(env->cfg->harden_unknown_additional &&
631 !type_allowed_in_additional_section(rrset->type)) {
632 remove_rrset("normalize: removing irrelevant "
633 "RRset:", pkt, msg, prev, &rrset);
634 continue;
635 }
636 prev = rrset;
637 rrset = rrset->rrset_all_next;
638 }
639
640 return 1;
641 }
642
643 /**
644 * Store potential poison in the cache (only if hardening disabled).
645 * The rrset is stored in the cache but removed from the message.
646 * So that it will be used for infrastructure purposes, but not be
647 * returned to the client.
648 * @param pkt: packet
649 * @param msg: message parsed
650 * @param env: environment with cache
651 * @param rrset: to store.
652 */
653 static void
store_rrset(sldns_buffer * pkt,struct msg_parse * msg,struct module_env * env,struct rrset_parse * rrset)654 store_rrset(sldns_buffer* pkt, struct msg_parse* msg, struct module_env* env,
655 struct rrset_parse* rrset)
656 {
657 struct ub_packed_rrset_key* k;
658 struct packed_rrset_data* d;
659 struct rrset_ref ref;
660 time_t now = *env->now;
661
662 k = alloc_special_obtain(env->alloc);
663 if(!k)
664 return;
665 k->entry.data = NULL;
666 if(!parse_copy_decompress_rrset(pkt, msg, rrset, NULL, k)) {
667 alloc_special_release(env->alloc, k);
668 return;
669 }
670 d = (struct packed_rrset_data*)k->entry.data;
671 packed_rrset_ttl_add(d, now);
672 ref.key = k;
673 ref.id = k->id;
674 /*ignore ret: it was in the cache, ref updated */
675 (void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, now);
676 }
677
678 /**
679 * Check if right hand name in NSEC is within zone
680 * @param pkt: the packet buffer for decompression.
681 * @param rrset: the NSEC rrset
682 * @param zonename: the zone name.
683 * @return true if BAD.
684 */
sanitize_nsec_is_overreach(sldns_buffer * pkt,struct rrset_parse * rrset,uint8_t * zonename)685 static int sanitize_nsec_is_overreach(sldns_buffer* pkt,
686 struct rrset_parse* rrset, uint8_t* zonename)
687 {
688 struct rr_parse* rr;
689 uint8_t* rhs;
690 size_t len;
691 log_assert(rrset->type == LDNS_RR_TYPE_NSEC);
692 for(rr = rrset->rr_first; rr; rr = rr->next) {
693 size_t pos = sldns_buffer_position(pkt);
694 size_t rhspos;
695 rhs = rr->ttl_data+4+2;
696 len = sldns_read_uint16(rr->ttl_data+4);
697 rhspos = rhs-sldns_buffer_begin(pkt);
698 sldns_buffer_set_position(pkt, rhspos);
699 if(pkt_dname_len(pkt) == 0) {
700 /* malformed */
701 sldns_buffer_set_position(pkt, pos);
702 return 1;
703 }
704 if(sldns_buffer_position(pkt)-rhspos > len) {
705 /* outside of rdata boundaries */
706 sldns_buffer_set_position(pkt, pos);
707 return 1;
708 }
709 sldns_buffer_set_position(pkt, pos);
710 if(!pkt_sub(pkt, rhs, zonename)) {
711 /* overreaching */
712 return 1;
713 }
714 }
715 /* all NSEC RRs OK */
716 return 0;
717 }
718
719 /** Remove individual RRs, if the length is wrong. Returns true if the RRset
720 * has been removed. */
721 static int
scrub_sanitize_rr_length(sldns_buffer * pkt,struct msg_parse * msg,struct rrset_parse * prev,struct rrset_parse ** rrset,int * added_ede,struct module_qstate * qstate)722 scrub_sanitize_rr_length(sldns_buffer* pkt, struct msg_parse* msg,
723 struct rrset_parse* prev, struct rrset_parse** rrset, int* added_ede,
724 struct module_qstate* qstate)
725 {
726 struct rr_parse* rr, *rr_prev = NULL;
727 for(rr = (*rrset)->rr_first; rr; rr = rr->next) {
728
729 /* Sanity check for length of records
730 * An A record should be 6 bytes only
731 * (2 bytes for length and 4 for IPv4 addr)*/
732 if((*rrset)->type == LDNS_RR_TYPE_A && rr->size != 6 ) {
733 if(!*added_ede) {
734 *added_ede = 1;
735 errinf_ede(qstate, "sanitize: records of inappropriate length have been removed.",
736 LDNS_EDE_OTHER);
737 }
738 if(msgparse_rrset_remove_rr("sanitize: removing type A RR of inappropriate length:",
739 pkt, *rrset, rr_prev, rr, NULL, 0)) {
740 remove_rrset("sanitize: removing type A RRset of inappropriate length:",
741 pkt, msg, prev, rrset);
742 return 1;
743 }
744 continue;
745 }
746
747 /* Sanity check for length of records
748 * An AAAA record should be 18 bytes only
749 * (2 bytes for length and 16 for IPv6 addr)*/
750 if((*rrset)->type == LDNS_RR_TYPE_AAAA && rr->size != 18 ) {
751 if(!*added_ede) {
752 *added_ede = 1;
753 errinf_ede(qstate, "sanitize: records of inappropriate length have been removed.",
754 LDNS_EDE_OTHER);
755 }
756 if(msgparse_rrset_remove_rr("sanitize: removing type AAAA RR of inappropriate length:",
757 pkt, *rrset, rr_prev, rr, NULL, 0)) {
758 remove_rrset("sanitize: removing type AAAA RRset of inappropriate length:",
759 pkt, msg, prev, rrset);
760 return 1;
761 }
762 continue;
763 }
764 rr_prev = rr;
765 }
766 return 0;
767 }
768
769 /**
770 * Given a response event, remove suspect RRsets from the response.
771 * "Suspect" rrsets are potentially poison. Note that this routine expects
772 * the response to be in a "normalized" state -- that is, all "irrelevant"
773 * RRsets have already been removed, CNAMEs are in order, etc.
774 *
775 * @param pkt: packet.
776 * @param msg: msg to normalize.
777 * @param qinfo: the question originally asked.
778 * @param zonename: name of server zone.
779 * @param env: module environment with config and cache.
780 * @param ie: iterator environment with private address data.
781 * @param qstate: for setting errinf for EDE error messages.
782 * @return 0 on error.
783 */
784 static int
scrub_sanitize(sldns_buffer * pkt,struct msg_parse * msg,struct query_info * qinfo,uint8_t * zonename,struct module_env * env,struct iter_env * ie,struct module_qstate * qstate)785 scrub_sanitize(sldns_buffer* pkt, struct msg_parse* msg,
786 struct query_info* qinfo, uint8_t* zonename, struct module_env* env,
787 struct iter_env* ie, struct module_qstate* qstate)
788 {
789 int del_addi = 0; /* if additional-holding rrsets are deleted, we
790 do not trust the normalized additional-A-AAAA any more */
791 int added_rrlen_ede = 0;
792 struct rrset_parse* rrset, *prev;
793 prev = NULL;
794 rrset = msg->rrset_first;
795
796 /* the first DNAME is allowed to stay. It needs checking before
797 * it can be used from the cache. After normalization, an initial
798 * DNAME will have a correctly synthesized CNAME after it. */
799 if(rrset && rrset->type == LDNS_RR_TYPE_DNAME &&
800 rrset->section == LDNS_SECTION_ANSWER &&
801 pkt_strict_sub(pkt, qinfo->qname, rrset->dname) &&
802 pkt_sub(pkt, rrset->dname, zonename)) {
803 prev = rrset; /* DNAME allowed to stay in answer section */
804 rrset = rrset->rrset_all_next;
805 }
806
807 /* remove all records from the answer section that are
808 * not the same domain name as the query domain name.
809 * The answer section should contain rrsets with the same name
810 * as the question. For DNAMEs a CNAME has been synthesized.
811 * Wildcards have the query name in answer section.
812 * ANY queries get query name in answer section.
813 * Remainders of CNAME chains are cut off and resolved by iterator. */
814 while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
815 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) != 0) {
816 if(has_additional(rrset->type)) del_addi = 1;
817 remove_rrset("sanitize: removing extraneous answer "
818 "RRset:", pkt, msg, prev, &rrset);
819 continue;
820 }
821 prev = rrset;
822 rrset = rrset->rrset_all_next;
823 }
824
825 /* At this point, we brutally remove ALL rrsets that aren't
826 * children of the originating zone. The idea here is that,
827 * as far as we know, the server that we contacted is ONLY
828 * authoritative for the originating zone. It, of course, MAY
829 * be authoritative for any other zones, and of course, MAY
830 * NOT be authoritative for some subdomains of the originating
831 * zone. */
832 prev = NULL;
833 rrset = msg->rrset_first;
834 while(rrset) {
835
836 /* Sanity check for length of records */
837 if(rrset->type == LDNS_RR_TYPE_A ||
838 rrset->type == LDNS_RR_TYPE_AAAA) {
839 if(scrub_sanitize_rr_length(pkt, msg, prev, &rrset,
840 &added_rrlen_ede, qstate))
841 continue;
842 }
843
844 /* remove private addresses */
845 if( (rrset->type == LDNS_RR_TYPE_A ||
846 rrset->type == LDNS_RR_TYPE_AAAA)) {
847
848 /* do not set servfail since this leads to too
849 * many drops of other people using rfc1918 space */
850 /* also do not remove entire rrset, unless all records
851 * in it are bad */
852 if(priv_rrset_bad(ie->priv, pkt, rrset)) {
853 remove_rrset(NULL, pkt, msg, prev, &rrset);
854 continue;
855 }
856 }
857
858 /* skip DNAME records -- they will always be followed by a
859 * synthesized CNAME, which will be relevant.
860 * FIXME: should this do something differently with DNAME
861 * rrsets NOT in Section.ANSWER? */
862 /* But since DNAME records are also subdomains of the zone,
863 * same check can be used */
864
865 if(!pkt_sub(pkt, rrset->dname, zonename)) {
866 if(msg->an_rrsets == 0 &&
867 rrset->type == LDNS_RR_TYPE_NS &&
868 rrset->section == LDNS_SECTION_AUTHORITY &&
869 FLAGS_GET_RCODE(msg->flags) ==
870 LDNS_RCODE_NOERROR && !soa_in_auth(msg) &&
871 sub_of_pkt(pkt, zonename, rrset->dname)) {
872 /* noerror, nodata and this NS rrset is above
873 * the zone. This is LAME!
874 * Leave in the NS for lame classification. */
875 /* remove everything from the additional
876 * (we dont want its glue that was approved
877 * during the normalize action) */
878 del_addi = 1;
879 } else if(!env->cfg->harden_glue && (
880 rrset->type == LDNS_RR_TYPE_A ||
881 rrset->type == LDNS_RR_TYPE_AAAA)) {
882 /* store in cache! Since it is relevant
883 * (from normalize) it will be picked up
884 * from the cache to be used later */
885 store_rrset(pkt, msg, env, rrset);
886 remove_rrset("sanitize: storing potential "
887 "poison RRset:", pkt, msg, prev, &rrset);
888 continue;
889 } else {
890 if(has_additional(rrset->type)) del_addi = 1;
891 remove_rrset("sanitize: removing potential "
892 "poison RRset:", pkt, msg, prev, &rrset);
893 continue;
894 }
895 }
896 if(del_addi && rrset->section == LDNS_SECTION_ADDITIONAL) {
897 remove_rrset("sanitize: removing potential "
898 "poison reference RRset:", pkt, msg, prev, &rrset);
899 continue;
900 }
901 /* check if right hand side of NSEC is within zone */
902 if(rrset->type == LDNS_RR_TYPE_NSEC &&
903 sanitize_nsec_is_overreach(pkt, rrset, zonename)) {
904 remove_rrset("sanitize: removing overreaching NSEC "
905 "RRset:", pkt, msg, prev, &rrset);
906 continue;
907 }
908 prev = rrset;
909 rrset = rrset->rrset_all_next;
910 }
911 return 1;
912 }
913
914 int
scrub_message(sldns_buffer * pkt,struct msg_parse * msg,struct query_info * qinfo,uint8_t * zonename,struct regional * region,struct module_env * env,struct module_qstate * qstate,struct iter_env * ie)915 scrub_message(sldns_buffer* pkt, struct msg_parse* msg,
916 struct query_info* qinfo, uint8_t* zonename, struct regional* region,
917 struct module_env* env, struct module_qstate* qstate,
918 struct iter_env* ie)
919 {
920 /* basic sanity checks */
921 log_nametypeclass(VERB_ALGO, "scrub for", zonename, LDNS_RR_TYPE_NS,
922 qinfo->qclass);
923 if(msg->qdcount > 1)
924 return 0;
925 if( !(msg->flags&BIT_QR) )
926 return 0;
927 msg->flags &= ~(BIT_AD|BIT_Z); /* force off bit AD and Z */
928
929 /* make sure that a query is echoed back when NOERROR or NXDOMAIN */
930 /* this is not required for basic operation but is a forgery
931 * resistance (security) feature */
932 if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR ||
933 FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) &&
934 msg->qdcount == 0)
935 return 0;
936
937 /* if a query is echoed back, make sure it is correct. Otherwise,
938 * this may be not a reply to our query. */
939 if(msg->qdcount == 1) {
940 if(dname_pkt_compare(pkt, msg->qname, qinfo->qname) != 0)
941 return 0;
942 if(msg->qtype != qinfo->qtype || msg->qclass != qinfo->qclass)
943 return 0;
944 }
945
946 /* normalize the response, this cleans up the additional. */
947 if(!scrub_normalize(pkt, msg, qinfo, region, env))
948 return 0;
949 /* delete all out-of-zone information */
950 if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie, qstate))
951 return 0;
952 return 1;
953 }
954