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 */ 62static void 63remove_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 */ 90static int 91has_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 */ 110static int 111get_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 */ 150static void 151mark_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 */ 186static int 187parse_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 */ 225static int 226synth_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 */ 251static struct rrset_parse* 252synth_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 */ 308static int 309pkt_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 */ 320static int 321pkt_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 */ 329static int 330sub_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) */ 338static int 339soa_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/** 350 * This routine normalizes a response. This includes removing "irrelevant" 351 * records from the answer and additional sections and (re)synthesizing 352 * CNAMEs from DNAMEs, if present. 353 * 354 * @param pkt: packet. 355 * @param msg: msg to normalize. 356 * @param qinfo: original query. 357 * @param region: where to allocate synthesized CNAMEs. 358 * @return 0 on error. 359 */ 360static int 361scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg, 362 struct query_info* qinfo, struct regional* region) 363{ 364 uint8_t* sname = qinfo->qname; 365 size_t snamelen = qinfo->qname_len; 366 struct rrset_parse* rrset, *prev, *nsset=NULL; 367 368 if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR && 369 FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN) 370 return 1; 371 372 /* For the ANSWER section, remove all "irrelevant" records and add 373 * synthesized CNAMEs from DNAMEs 374 * This will strip out-of-order CNAMEs as well. */ 375 376 /* walk through the parse packet rrset list, keep track of previous 377 * for insert and delete ease, and examine every RRset */ 378 prev = NULL; 379 rrset = msg->rrset_first; 380 while(rrset && rrset->section == LDNS_SECTION_ANSWER) { 381 if(rrset->type == LDNS_RR_TYPE_DNAME && 382 pkt_strict_sub(pkt, sname, rrset->dname)) { 383 /* check if next rrset is correct CNAME. else, 384 * synthesize a CNAME */ 385 struct rrset_parse* nx = rrset->rrset_all_next; 386 uint8_t alias[LDNS_MAX_DOMAINLEN+1]; 387 size_t aliaslen = 0; 388 if(rrset->rr_count != 1) { 389 verbose(VERB_ALGO, "Found DNAME rrset with " 390 "size > 1: %u", 391 (unsigned)rrset->rr_count); 392 return 0; 393 } 394 if(!synth_cname(sname, snamelen, rrset, alias, 395 &aliaslen, pkt)) { 396 verbose(VERB_ALGO, "synthesized CNAME " 397 "too long"); 398 return 0; 399 } 400 if(nx && nx->type == LDNS_RR_TYPE_CNAME && 401 dname_pkt_compare(pkt, sname, nx->dname) == 0) { 402 /* check next cname */ 403 uint8_t* t = NULL; 404 size_t tlen = 0; 405 if(!parse_get_cname_target(nx, &t, &tlen, pkt)) 406 return 0; 407 if(dname_pkt_compare(pkt, alias, t) == 0) { 408 /* it's OK and better capitalized */ 409 prev = rrset; 410 rrset = nx; 411 continue; 412 } 413 /* synth ourselves */ 414 } 415 /* synth a CNAME rrset */ 416 prev = synth_cname_rrset(&sname, &snamelen, alias, 417 aliaslen, region, msg, rrset, rrset, nx, pkt); 418 if(!prev) { 419 log_err("out of memory synthesizing CNAME"); 420 return 0; 421 } 422 /* FIXME: resolve the conflict between synthesized 423 * CNAME ttls and the cache. */ 424 rrset = nx; 425 continue; 426 427 } 428 429 /* The only records in the ANSWER section not allowed to */ 430 if(dname_pkt_compare(pkt, sname, rrset->dname) != 0) { 431 remove_rrset("normalize: removing irrelevant RRset:", 432 pkt, msg, prev, &rrset); 433 continue; 434 } 435 436 /* Follow the CNAME chain. */ 437 if(rrset->type == LDNS_RR_TYPE_CNAME) { 438 struct rrset_parse* nx = rrset->rrset_all_next; 439 uint8_t* oldsname = sname; 440 /* see if the next one is a DNAME, if so, swap them */ 441 if(nx && nx->section == LDNS_SECTION_ANSWER && 442 nx->type == LDNS_RR_TYPE_DNAME && 443 nx->rr_count == 1 && 444 pkt_strict_sub(pkt, sname, nx->dname)) { 445 /* there is a DNAME after this CNAME, it 446 * is in the ANSWER section, and the DNAME 447 * applies to the name we cover */ 448 /* check if the alias of the DNAME equals 449 * this CNAME */ 450 uint8_t alias[LDNS_MAX_DOMAINLEN+1]; 451 size_t aliaslen = 0; 452 uint8_t* t = NULL; 453 size_t tlen = 0; 454 if(synth_cname(sname, snamelen, nx, alias, 455 &aliaslen, pkt) && 456 parse_get_cname_target(rrset, &t, &tlen, pkt) && 457 dname_pkt_compare(pkt, alias, t) == 0) { 458 /* the synthesized CNAME equals the 459 * current CNAME. This CNAME is the 460 * one that the DNAME creates, and this 461 * CNAME is better capitalised */ 462 verbose(VERB_ALGO, "normalize: re-order of DNAME and its CNAME"); 463 if(prev) prev->rrset_all_next = nx; 464 else msg->rrset_first = nx; 465 if(nx->rrset_all_next == NULL) 466 msg->rrset_last = rrset; 467 rrset->rrset_all_next = 468 nx->rrset_all_next; 469 nx->rrset_all_next = rrset; 470 /* prev = nx; unused, enable if there 471 * is other rrset removal code after 472 * this */ 473 } 474 } 475 476 /* move to next name in CNAME chain */ 477 if(!parse_get_cname_target(rrset, &sname, &snamelen, pkt)) 478 return 0; 479 prev = rrset; 480 rrset = rrset->rrset_all_next; 481 /* in CNAME ANY response, can have data after CNAME */ 482 if(qinfo->qtype == LDNS_RR_TYPE_ANY) { 483 while(rrset && rrset->section == 484 LDNS_SECTION_ANSWER && 485 dname_pkt_compare(pkt, oldsname, 486 rrset->dname) == 0) { 487 prev = rrset; 488 rrset = rrset->rrset_all_next; 489 } 490 } 491 continue; 492 } 493 494 /* Otherwise, make sure that the RRset matches the qtype. */ 495 if(qinfo->qtype != LDNS_RR_TYPE_ANY && 496 qinfo->qtype != rrset->type) { 497 remove_rrset("normalize: removing irrelevant RRset:", 498 pkt, msg, prev, &rrset); 499 continue; 500 } 501 502 /* Mark the additional names from relevant rrset as OK. */ 503 /* only for RRsets that match the query name, other ones 504 * will be removed by sanitize, so no additional for them */ 505 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0) 506 mark_additional_rrset(pkt, msg, rrset); 507 508 prev = rrset; 509 rrset = rrset->rrset_all_next; 510 } 511 512 /* Mark additional names from AUTHORITY */ 513 while(rrset && rrset->section == LDNS_SECTION_AUTHORITY) { 514 if(rrset->type==LDNS_RR_TYPE_DNAME || 515 rrset->type==LDNS_RR_TYPE_CNAME || 516 rrset->type==LDNS_RR_TYPE_A || 517 rrset->type==LDNS_RR_TYPE_AAAA) { 518 remove_rrset("normalize: removing irrelevant " 519 "RRset:", pkt, msg, prev, &rrset); 520 continue; 521 } 522 /* only one NS set allowed in authority section */ 523 if(rrset->type==LDNS_RR_TYPE_NS) { 524 /* NS set must be pertinent to the query */ 525 if(!sub_of_pkt(pkt, qinfo->qname, rrset->dname)) { 526 remove_rrset("normalize: removing irrelevant " 527 "RRset:", pkt, msg, prev, &rrset); 528 continue; 529 } 530 /* we don't want NS sets for NXDOMAIN answers, 531 * because they could contain poisonous contents, 532 * from. eg. fragmentation attacks, inserted after 533 * long RRSIGs in the packet get to the packet 534 * border and such */ 535 /* also for NODATA answers */ 536 if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN || 537 (FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR 538 && soa_in_auth(msg) && msg->an_rrsets == 0)) { 539 remove_rrset("normalize: removing irrelevant " 540 "RRset:", pkt, msg, prev, &rrset); 541 continue; 542 } 543 if(nsset == NULL) { 544 nsset = rrset; 545 } else { 546 remove_rrset("normalize: removing irrelevant " 547 "RRset:", pkt, msg, prev, &rrset); 548 continue; 549 } 550 } 551 /* if this is type DS and we query for type DS we just got 552 * a referral answer for our type DS query, fix packet */ 553 if(rrset->type==LDNS_RR_TYPE_DS && 554 qinfo->qtype == LDNS_RR_TYPE_DS && 555 dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0) { 556 rrset->section = LDNS_SECTION_ANSWER; 557 msg->ancount = rrset->rr_count + rrset->rrsig_count; 558 msg->nscount = 0; 559 msg->arcount = 0; 560 msg->an_rrsets = 1; 561 msg->ns_rrsets = 0; 562 msg->ar_rrsets = 0; 563 msg->rrset_count = 1; 564 msg->rrset_first = rrset; 565 msg->rrset_last = rrset; 566 rrset->rrset_all_next = NULL; 567 return 1; 568 } 569 mark_additional_rrset(pkt, msg, rrset); 570 prev = rrset; 571 rrset = rrset->rrset_all_next; 572 } 573 574 /* For each record in the additional section, remove it if it is an 575 * address record and not in the collection of additional names 576 * found in ANSWER and AUTHORITY. */ 577 /* These records have not been marked OK previously */ 578 while(rrset && rrset->section == LDNS_SECTION_ADDITIONAL) { 579 /* FIXME: what about other types? */ 580 if(rrset->type==LDNS_RR_TYPE_A || 581 rrset->type==LDNS_RR_TYPE_AAAA) 582 { 583 if((rrset->flags & RRSET_SCRUB_OK)) { 584 /* remove flag to clean up flags variable */ 585 rrset->flags &= ~RRSET_SCRUB_OK; 586 } else { 587 remove_rrset("normalize: removing irrelevant " 588 "RRset:", pkt, msg, prev, &rrset); 589 continue; 590 } 591 } 592 if(rrset->type==LDNS_RR_TYPE_DNAME || 593 rrset->type==LDNS_RR_TYPE_CNAME || 594 rrset->type==LDNS_RR_TYPE_NS) { 595 remove_rrset("normalize: removing irrelevant " 596 "RRset:", pkt, msg, prev, &rrset); 597 continue; 598 } 599 prev = rrset; 600 rrset = rrset->rrset_all_next; 601 } 602 603 return 1; 604} 605 606/** 607 * Store potential poison in the cache (only if hardening disabled). 608 * The rrset is stored in the cache but removed from the message. 609 * So that it will be used for infrastructure purposes, but not be 610 * returned to the client. 611 * @param pkt: packet 612 * @param msg: message parsed 613 * @param env: environment with cache 614 * @param rrset: to store. 615 */ 616static void 617store_rrset(sldns_buffer* pkt, struct msg_parse* msg, struct module_env* env, 618 struct rrset_parse* rrset) 619{ 620 struct ub_packed_rrset_key* k; 621 struct packed_rrset_data* d; 622 struct rrset_ref ref; 623 time_t now = *env->now; 624 625 k = alloc_special_obtain(env->alloc); 626 if(!k) 627 return; 628 k->entry.data = NULL; 629 if(!parse_copy_decompress_rrset(pkt, msg, rrset, NULL, k)) { 630 alloc_special_release(env->alloc, k); 631 return; 632 } 633 d = (struct packed_rrset_data*)k->entry.data; 634 packed_rrset_ttl_add(d, now); 635 ref.key = k; 636 ref.id = k->id; 637 /*ignore ret: it was in the cache, ref updated */ 638 (void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, now); 639} 640 641/** 642 * Check if right hand name in NSEC is within zone 643 * @param rrset: the NSEC rrset 644 * @param zonename: the zone name. 645 * @return true if BAD. 646 */ 647static int sanitize_nsec_is_overreach(struct rrset_parse* rrset, 648 uint8_t* zonename) 649{ 650 struct rr_parse* rr; 651 uint8_t* rhs; 652 size_t len; 653 log_assert(rrset->type == LDNS_RR_TYPE_NSEC); 654 for(rr = rrset->rr_first; rr; rr = rr->next) { 655 rhs = rr->ttl_data+4+2; 656 len = sldns_read_uint16(rr->ttl_data+4); 657 if(!dname_valid(rhs, len)) { 658 /* malformed domain name in rdata */ 659 return 1; 660 } 661 if(!dname_subdomain_c(rhs, zonename)) { 662 /* overreaching */ 663 return 1; 664 } 665 } 666 /* all NSEC RRs OK */ 667 return 0; 668} 669 670/** 671 * Given a response event, remove suspect RRsets from the response. 672 * "Suspect" rrsets are potentially poison. Note that this routine expects 673 * the response to be in a "normalized" state -- that is, all "irrelevant" 674 * RRsets have already been removed, CNAMEs are in order, etc. 675 * 676 * @param pkt: packet. 677 * @param msg: msg to normalize. 678 * @param qinfo: the question originally asked. 679 * @param zonename: name of server zone. 680 * @param env: module environment with config and cache. 681 * @param ie: iterator environment with private address data. 682 * @return 0 on error. 683 */ 684static int 685scrub_sanitize(sldns_buffer* pkt, struct msg_parse* msg, 686 struct query_info* qinfo, uint8_t* zonename, struct module_env* env, 687 struct iter_env* ie) 688{ 689 int del_addi = 0; /* if additional-holding rrsets are deleted, we 690 do not trust the normalized additional-A-AAAA any more */ 691 struct rrset_parse* rrset, *prev; 692 prev = NULL; 693 rrset = msg->rrset_first; 694 695 /* the first DNAME is allowed to stay. It needs checking before 696 * it can be used from the cache. After normalization, an initial 697 * DNAME will have a correctly synthesized CNAME after it. */ 698 if(rrset && rrset->type == LDNS_RR_TYPE_DNAME && 699 rrset->section == LDNS_SECTION_ANSWER && 700 pkt_strict_sub(pkt, qinfo->qname, rrset->dname) && 701 pkt_sub(pkt, rrset->dname, zonename)) { 702 prev = rrset; /* DNAME allowed to stay in answer section */ 703 rrset = rrset->rrset_all_next; 704 } 705 706 /* remove all records from the answer section that are 707 * not the same domain name as the query domain name. 708 * The answer section should contain rrsets with the same name 709 * as the question. For DNAMEs a CNAME has been synthesized. 710 * Wildcards have the query name in answer section. 711 * ANY queries get query name in answer section. 712 * Remainders of CNAME chains are cut off and resolved by iterator. */ 713 while(rrset && rrset->section == LDNS_SECTION_ANSWER) { 714 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) != 0) { 715 if(has_additional(rrset->type)) del_addi = 1; 716 remove_rrset("sanitize: removing extraneous answer " 717 "RRset:", pkt, msg, prev, &rrset); 718 continue; 719 } 720 prev = rrset; 721 rrset = rrset->rrset_all_next; 722 } 723 724 /* At this point, we brutally remove ALL rrsets that aren't 725 * children of the originating zone. The idea here is that, 726 * as far as we know, the server that we contacted is ONLY 727 * authoritative for the originating zone. It, of course, MAY 728 * be authoritative for any other zones, and of course, MAY 729 * NOT be authoritative for some subdomains of the originating 730 * zone. */ 731 prev = NULL; 732 rrset = msg->rrset_first; 733 while(rrset) { 734 735 /* remove private addresses */ 736 if( (rrset->type == LDNS_RR_TYPE_A || 737 rrset->type == LDNS_RR_TYPE_AAAA)) { 738 739 /* do not set servfail since this leads to too 740 * many drops of other people using rfc1918 space */ 741 /* also do not remove entire rrset, unless all records 742 * in it are bad */ 743 if(priv_rrset_bad(ie->priv, pkt, rrset)) { 744 remove_rrset(NULL, pkt, msg, prev, &rrset); 745 continue; 746 } 747 } 748 749 /* skip DNAME records -- they will always be followed by a 750 * synthesized CNAME, which will be relevant. 751 * FIXME: should this do something differently with DNAME 752 * rrsets NOT in Section.ANSWER? */ 753 /* But since DNAME records are also subdomains of the zone, 754 * same check can be used */ 755 756 if(!pkt_sub(pkt, rrset->dname, zonename)) { 757 if(msg->an_rrsets == 0 && 758 rrset->type == LDNS_RR_TYPE_NS && 759 rrset->section == LDNS_SECTION_AUTHORITY && 760 FLAGS_GET_RCODE(msg->flags) == 761 LDNS_RCODE_NOERROR && !soa_in_auth(msg) && 762 sub_of_pkt(pkt, zonename, rrset->dname)) { 763 /* noerror, nodata and this NS rrset is above 764 * the zone. This is LAME! 765 * Leave in the NS for lame classification. */ 766 /* remove everything from the additional 767 * (we dont want its glue that was approved 768 * during the normalize action) */ 769 del_addi = 1; 770 } else if(!env->cfg->harden_glue && ( 771 rrset->type == LDNS_RR_TYPE_A || 772 rrset->type == LDNS_RR_TYPE_AAAA)) { 773 /* store in cache! Since it is relevant 774 * (from normalize) it will be picked up 775 * from the cache to be used later */ 776 store_rrset(pkt, msg, env, rrset); 777 remove_rrset("sanitize: storing potential " 778 "poison RRset:", pkt, msg, prev, &rrset); 779 continue; 780 } else { 781 if(has_additional(rrset->type)) del_addi = 1; 782 remove_rrset("sanitize: removing potential " 783 "poison RRset:", pkt, msg, prev, &rrset); 784 continue; 785 } 786 } 787 if(del_addi && rrset->section == LDNS_SECTION_ADDITIONAL) { 788 remove_rrset("sanitize: removing potential " 789 "poison reference RRset:", pkt, msg, prev, &rrset); 790 continue; 791 } 792 /* check if right hand side of NSEC is within zone */ 793 if(rrset->type == LDNS_RR_TYPE_NSEC && 794 sanitize_nsec_is_overreach(rrset, zonename)) { 795 remove_rrset("sanitize: removing overreaching NSEC " 796 "RRset:", pkt, msg, prev, &rrset); 797 continue; 798 } 799 prev = rrset; 800 rrset = rrset->rrset_all_next; 801 } 802 return 1; 803} 804 805int 806scrub_message(sldns_buffer* pkt, struct msg_parse* msg, 807 struct query_info* qinfo, uint8_t* zonename, struct regional* region, 808 struct module_env* env, struct iter_env* ie) 809{ 810 /* basic sanity checks */ 811 log_nametypeclass(VERB_ALGO, "scrub for", zonename, LDNS_RR_TYPE_NS, 812 qinfo->qclass); 813 if(msg->qdcount > 1) 814 return 0; 815 if( !(msg->flags&BIT_QR) ) 816 return 0; 817 msg->flags &= ~(BIT_AD|BIT_Z); /* force off bit AD and Z */ 818 819 /* make sure that a query is echoed back when NOERROR or NXDOMAIN */ 820 /* this is not required for basic operation but is a forgery 821 * resistance (security) feature */ 822 if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR || 823 FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) && 824 msg->qdcount == 0) 825 return 0; 826 827 /* if a query is echoed back, make sure it is correct. Otherwise, 828 * this may be not a reply to our query. */ 829 if(msg->qdcount == 1) { 830 if(dname_pkt_compare(pkt, msg->qname, qinfo->qname) != 0) 831 return 0; 832 if(msg->qtype != qinfo->qtype || msg->qclass != qinfo->qclass) 833 return 0; 834 } 835 836 /* normalize the response, this cleans up the additional. */ 837 if(!scrub_normalize(pkt, msg, qinfo, region)) 838 return 0; 839 /* delete all out-of-zone information */ 840 if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie)) 841 return 0; 842 return 1; 843} 844