iterator/iter_scrub.c

   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
  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
  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
 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
 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
 187 parse_get_cname_target(struct rrset_parse* rrset, uint8_t** sname,
 188         size_t* snamelen)
 189 {
 190         if(rrset->rr_count != 1) {
 191                 struct rr_parse* sig;
 192                 verbose(VERB_ALGO, "Found CNAME rrset with "
 193                         "size > 1: %u", (unsigned)rrset->rr_count);
 194                 /* use the first CNAME! */
 195                 rrset->rr_count = 1;
 196                 rrset->size = rrset->rr_first->size;
 197                 for(sig=rrset->rrsig_first; sig; sig=sig->next)
 198                         rrset->size += sig->size;
 199                 rrset->rr_last = rrset->rr_first;
 200                 rrset->rr_first->next = NULL;
 201         }
 202         if(rrset->rr_first->size < sizeof(uint16_t)+1)
 203                 return 0; /* CNAME rdata too small */
 204         *sname = rrset->rr_first->ttl_data + sizeof(uint32_t)
 205                 + sizeof(uint16_t); /* skip ttl, rdatalen */
 206         *snamelen = rrset->rr_first->size - sizeof(uint16_t);
 207         return 1;
 208 }
 209
 210 /** Synthesize CNAME from DNAME, false if too long */
 211 static int
 212 synth_cname(uint8_t* qname, size_t qnamelen, struct rrset_parse* dname_rrset,
 213         uint8_t* alias, size_t* aliaslen, sldns_buffer* pkt)
 214 {
 215         /* we already know that sname is a strict subdomain of DNAME owner */
 216         uint8_t* dtarg = NULL;
 217         size_t dtarglen;
 218         if(!parse_get_cname_target(dname_rrset, &dtarg, &dtarglen))
 219                 return 0;
 220         log_assert(qnamelen > dname_rrset->dname_len);
 221         /* DNAME from com. to net. with qname example.com. -> example.net. */
 222         /* so: \3com\0 to \3net\0 and qname \7example\3com\0 */
 223         *aliaslen = qnamelen + dtarglen - dname_rrset->dname_len;
 224         if(*aliaslen > LDNS_MAX_DOMAINLEN)
 225                 return 0; /* should have been RCODE YXDOMAIN */
 226         /* decompress dnames into buffer, we know it fits */
 227         dname_pkt_copy(pkt, alias, qname);
 228         dname_pkt_copy(pkt, alias+(qnamelen-dname_rrset->dname_len), dtarg);
 229         return 1;
 230 }
 231
 232 /** synthesize a CNAME rrset */
 233 static struct rrset_parse*
 234 synth_cname_rrset(uint8_t** sname, size_t* snamelen, uint8_t* alias,
 235         size_t aliaslen, struct regional* region, struct msg_parse* msg,
 236         struct rrset_parse* rrset, struct rrset_parse* prev,
 237         struct rrset_parse* nx, sldns_buffer* pkt)
 238 {
 239         struct rrset_parse* cn = (struct rrset_parse*)regional_alloc(region,
 240                 sizeof(struct rrset_parse));
 241         if(!cn)
 242                 return NULL;
 243         memset(cn, 0, sizeof(*cn));
 244         cn->rr_first = (struct rr_parse*)regional_alloc(region,
 245                 sizeof(struct rr_parse));
 246         if(!cn->rr_first)
 247                 return NULL;
 248         cn->rr_last = cn->rr_first;
 249         /* CNAME from sname to alias */
 250         cn->dname = (uint8_t*)regional_alloc(region, *snamelen);
 251         if(!cn->dname)
 252                 return NULL;
 253         dname_pkt_copy(pkt, cn->dname, *sname);
 254         cn->dname_len = *snamelen;
 255         cn->type = LDNS_RR_TYPE_CNAME;
 256         cn->section = rrset->section;
 257         cn->rrset_class = rrset->rrset_class;
 258         cn->rr_count = 1;
 259         cn->size = sizeof(uint16_t) + aliaslen;
 260         cn->hash=pkt_hash_rrset(pkt, cn->dname, cn->type, cn->rrset_class, 0);
 261         /* allocate TTL + rdatalen + uncompressed dname */
 262         memset(cn->rr_first, 0, sizeof(struct rr_parse));
 263         cn->rr_first->outside_packet = 1;
 264         cn->rr_first->ttl_data = (uint8_t*)regional_alloc(region,
 265                 sizeof(uint32_t)+sizeof(uint16_t)+aliaslen);
 266         if(!cn->rr_first->ttl_data)
 267                 return NULL;
 268         sldns_write_uint32(cn->rr_first->ttl_data, 0); /* TTL = 0 */
 269         sldns_write_uint16(cn->rr_first->ttl_data+4, aliaslen);
 270         memmove(cn->rr_first->ttl_data+6, alias, aliaslen);
 271         cn->rr_first->size = sizeof(uint16_t)+aliaslen;
 272
 273         /* link it in */
 274         cn->rrset_all_next = nx;
 275         if(prev)
 276                 prev->rrset_all_next = cn;
 277         else    msg->rrset_first = cn;
 278         if(nx == NULL)
 279                 msg->rrset_last = cn;
 280         msg->rrset_count ++;
 281         msg->an_rrsets++;
 282         /* it is not inserted in the msg hashtable. */
 283
 284         *sname = cn->rr_first->ttl_data + sizeof(uint32_t)+sizeof(uint16_t);
 285         *snamelen = aliaslen;
 286         return cn;
 287 }
 288
 289 /** check if DNAME applies to a name */
 290 static int
 291 pkt_strict_sub(sldns_buffer* pkt, uint8_t* sname, uint8_t* dr)
 292 {
 293         uint8_t buf1[LDNS_MAX_DOMAINLEN+1];
 294         uint8_t buf2[LDNS_MAX_DOMAINLEN+1];
 295         /* decompress names */
 296         dname_pkt_copy(pkt, buf1, sname);
 297         dname_pkt_copy(pkt, buf2, dr);
 298         return dname_strict_subdomain_c(buf1, buf2);
 299 }
 300
 301 /** check subdomain with decompression */
 302 static int
 303 pkt_sub(sldns_buffer* pkt, uint8_t* comprname, uint8_t* zone)
 304 {
 305         uint8_t buf[LDNS_MAX_DOMAINLEN+1];
 306         dname_pkt_copy(pkt, buf, comprname);
 307         return dname_subdomain_c(buf, zone);
 308 }
 309
 310 /** check subdomain with decompression, compressed is parent */
 311 static int
 312 sub_of_pkt(sldns_buffer* pkt, uint8_t* zone, uint8_t* comprname)
 313 {
 314         uint8_t buf[LDNS_MAX_DOMAINLEN+1];
 315         dname_pkt_copy(pkt, buf, comprname);
 316         return dname_subdomain_c(zone, buf);
 317 }
 318
 319 /** Check if there are SOA records in the authority section (negative) */
 320 static int
 321 soa_in_auth(struct msg_parse* msg)
 322 {
 323         struct rrset_parse* rrset;
 324         for(rrset = msg->rrset_first; rrset; rrset = rrset->rrset_all_next)
 325                 if(rrset->type == LDNS_RR_TYPE_SOA &&
 326                         rrset->section == LDNS_SECTION_AUTHORITY)
 327                         return 1;
 328         return 0;
 329 }
 330
 331 /**
 332  * This routine normalizes a response. This includes removing "irrelevant"
 333  * records from the answer and additional sections and (re)synthesizing
 334  * CNAMEs from DNAMEs, if present.
 335  *
 336  * @param pkt: packet.
 337  * @param msg: msg to normalize.
 338  * @param qinfo: original query.
 339  * @param region: where to allocate synthesized CNAMEs.
 340  * @return 0 on error.
 341  */
 342 static int
 343 scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg,
 344         struct query_info* qinfo, struct regional* region)
 345 {
 346         uint8_t* sname = qinfo->qname;
 347         size_t snamelen = qinfo->qname_len;
 348         struct rrset_parse* rrset, *prev, *nsset=NULL;
 349
 350         if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR &&
 351                 FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN)
 352                 return 1;
 353
 354         /* For the ANSWER section, remove all "irrelevant" records and add
 355          * synthesized CNAMEs from DNAMEs
 356          * This will strip out-of-order CNAMEs as well. */
 357
 358         /* walk through the parse packet rrset list, keep track of previous
 359          * for insert and delete ease, and examine every RRset */
 360         prev = NULL;
 361         rrset = msg->rrset_first;
 362         while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
 363                 if(rrset->type == LDNS_RR_TYPE_DNAME &&
 364                         pkt_strict_sub(pkt, sname, rrset->dname)) {
 365                         /* check if next rrset is correct CNAME. else,
 366                          * synthesize a CNAME */
 367                         struct rrset_parse* nx = rrset->rrset_all_next;
 368                         uint8_t alias[LDNS_MAX_DOMAINLEN+1];
 369                         size_t aliaslen = 0;
 370                         if(rrset->rr_count != 1) {
 371                                 verbose(VERB_ALGO, "Found DNAME rrset with "
 372                                         "size > 1: %u",
 373                                         (unsigned)rrset->rr_count);
 374                                 return 0;
 375                         }
 376                         if(!synth_cname(sname, snamelen, rrset, alias,
 377                                 &aliaslen, pkt)) {
 378                                 verbose(VERB_ALGO, "synthesized CNAME "
 379                                         "too long");
 380                                 return 0;
 381                         }
 382                         if(nx && nx->type == LDNS_RR_TYPE_CNAME &&
 383                            dname_pkt_compare(pkt, sname, nx->dname) == 0) {
 384                                 /* check next cname */
 385                                 uint8_t* t = NULL;
 386                                 size_t tlen = 0;
 387                                 if(!parse_get_cname_target(nx, &t, &tlen))
 388                                         return 0;
 389                                 if(dname_pkt_compare(pkt, alias, t) == 0) {
 390                                         /* it's OK and better capitalized */
 391                                         prev = rrset;
 392                                         rrset = nx;
 393                                         continue;
 394                                 }
 395                                 /* synth ourselves */
 396                         }
 397                         /* synth a CNAME rrset */
 398                         prev = synth_cname_rrset(&sname, &snamelen, alias,
 399                                 aliaslen, region, msg, rrset, rrset, nx, pkt);
 400                         if(!prev) {
 401                                 log_err("out of memory synthesizing CNAME");
 402                                 return 0;
 403                         }
 404                         /* FIXME: resolve the conflict between synthesized
 405                          * CNAME ttls and the cache. */
 406                         rrset = nx;
 407                         continue;
 408
 409                 }
 410
 411                 /* The only records in the ANSWER section not allowed to */
 412                 if(dname_pkt_compare(pkt, sname, rrset->dname) != 0) {
 413                         remove_rrset("normalize: removing irrelevant RRset:",
 414                                 pkt, msg, prev, &rrset);
 415                         continue;
 416                 }
 417
 418                 /* Follow the CNAME chain. */
 419                 if(rrset->type == LDNS_RR_TYPE_CNAME) {
 420                         struct rrset_parse* nx = rrset->rrset_all_next;
 421                         uint8_t* oldsname = sname;
 422                         /* see if the next one is a DNAME, if so, swap them */
 423                         if(nx && nx->section == LDNS_SECTION_ANSWER &&
 424                                 nx->type == LDNS_RR_TYPE_DNAME &&
 425                                 nx->rr_count == 1 &&
 426                                 pkt_strict_sub(pkt, sname, nx->dname)) {
 427                                 /* there is a DNAME after this CNAME, it
 428                                  * is in the ANSWER section, and the DNAME
 429                                  * applies to the name we cover */
 430                                 /* check if the alias of the DNAME equals
 431                                  * this CNAME */
 432                                 uint8_t alias[LDNS_MAX_DOMAINLEN+1];
 433                                 size_t aliaslen = 0;
 434                                 uint8_t* t = NULL;
 435                                 size_t tlen = 0;
 436                                 if(synth_cname(sname, snamelen, nx, alias,
 437                                         &aliaslen, pkt) &&
 438                                         parse_get_cname_target(rrset, &t, &tlen) &&
 439                                         dname_pkt_compare(pkt, alias, t) == 0) {
 440                                         /* the synthesized CNAME equals the
 441                                          * current CNAME.  This CNAME is the
 442                                          * one that the DNAME creates, and this
 443                                          * CNAME is better capitalised */
 444                                         verbose(VERB_ALGO, "normalize: re-order of DNAME and its CNAME");
 445                                         if(prev) prev->rrset_all_next = nx;
 446                                         else msg->rrset_first = nx;
 447                                         if(nx->rrset_all_next == NULL)
 448                                                 msg->rrset_last = rrset;
 449                                         rrset->rrset_all_next =
 450                                                 nx->rrset_all_next;
 451                                         nx->rrset_all_next = rrset;
 452                                         /* prev = nx; unused, enable if there
 453                                          * is other rrset removal code after
 454                                          * this */
 455                                 }
 456                         }
 457
 458                         /* move to next name in CNAME chain */
 459                         if(!parse_get_cname_target(rrset, &sname, &snamelen))
 460                                 return 0;
 461                         prev = rrset;
 462                         rrset = rrset->rrset_all_next;
 463                         /* in CNAME ANY response, can have data after CNAME */
 464                         if(qinfo->qtype == LDNS_RR_TYPE_ANY) {
 465                                 while(rrset && rrset->section ==
 466                                         LDNS_SECTION_ANSWER &&
 467                                         dname_pkt_compare(pkt, oldsname,
 468                                         rrset->dname) == 0) {
 469                                         prev = rrset;
 470                                         rrset = rrset->rrset_all_next;
 471                                 }
 472                         }
 473                         continue;
 474                 }
 475
 476                 /* Otherwise, make sure that the RRset matches the qtype. */
 477                 if(qinfo->qtype != LDNS_RR_TYPE_ANY &&
 478                         qinfo->qtype != rrset->type) {
 479                         remove_rrset("normalize: removing irrelevant RRset:",
 480                                 pkt, msg, prev, &rrset);
 481                         continue;
 482                 }
 483
 484                 /* Mark the additional names from relevant rrset as OK. */
 485                 /* only for RRsets that match the query name, other ones
 486                  * will be removed by sanitize, so no additional for them */
 487                 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0)
 488                         mark_additional_rrset(pkt, msg, rrset);
 489
 490                 prev = rrset;
 491                 rrset = rrset->rrset_all_next;
 492         }
 493
 494         /* Mark additional names from AUTHORITY */
 495         while(rrset && rrset->section == LDNS_SECTION_AUTHORITY) {
 496                 if(rrset->type==LDNS_RR_TYPE_DNAME ||
 497                         rrset->type==LDNS_RR_TYPE_CNAME ||
 498                         rrset->type==LDNS_RR_TYPE_A ||
 499                         rrset->type==LDNS_RR_TYPE_AAAA) {
 500                         remove_rrset("normalize: removing irrelevant "
 501                                 "RRset:", pkt, msg, prev, &rrset);
 502                         continue;
 503                 }
 504                 /* only one NS set allowed in authority section */
 505                 if(rrset->type==LDNS_RR_TYPE_NS) {
 506                         /* NS set must be pertinent to the query */
 507                         if(!sub_of_pkt(pkt, qinfo->qname, rrset->dname)) {
 508                                 remove_rrset("normalize: removing irrelevant "
 509                                         "RRset:", pkt, msg, prev, &rrset);
 510                                 continue;
 511                         }
 512                         /* we don't want NS sets for NXDOMAIN answers,
 513                          * because they could contain poisonous contents,
 514                          * from. eg. fragmentation attacks, inserted after
 515                          * long RRSIGs in the packet get to the packet
 516                          * border and such */
 517                         /* also for NODATA answers */
 518                         if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN ||
 519                            (FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR
 520                             && soa_in_auth(msg) && msg->an_rrsets == 0)) {
 521                                 remove_rrset("normalize: removing irrelevant "
 522                                         "RRset:", pkt, msg, prev, &rrset);
 523                                 continue;
 524                         }
 525                         if(nsset == NULL) {
 526                                 nsset = rrset;
 527                         } else {
 528                                 remove_rrset("normalize: removing irrelevant "
 529                                         "RRset:", pkt, msg, prev, &rrset);
 530                                 continue;
 531                         }
 532                 }
 533                 /* if this is type DS and we query for type DS we just got
 534                  * a referral answer for our type DS query, fix packet */
 535                 if(rrset->type==LDNS_RR_TYPE_DS &&
 536                         qinfo->qtype == LDNS_RR_TYPE_DS &&
 537                         dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0) {
 538                         rrset->section = LDNS_SECTION_ANSWER;
 539                         msg->ancount = rrset->rr_count + rrset->rrsig_count;
 540                         msg->nscount = 0;
 541                         msg->arcount = 0;
 542                         msg->an_rrsets = 1;
 543                         msg->ns_rrsets = 0;
 544                         msg->ar_rrsets = 0;
 545                         msg->rrset_count = 1;
 546                         msg->rrset_first = rrset;
 547                         msg->rrset_last = rrset;
 548                         rrset->rrset_all_next = NULL;
 549                         return 1;
 550                 }
 551                 mark_additional_rrset(pkt, msg, rrset);
 552                 prev = rrset;
 553                 rrset = rrset->rrset_all_next;
 554         }
 555
 556         /* For each record in the additional section, remove it if it is an
 557          * address record and not in the collection of additional names
 558          * found in ANSWER and AUTHORITY. */
 559         /* These records have not been marked OK previously */
 560         while(rrset && rrset->section == LDNS_SECTION_ADDITIONAL) {
 561                 /* FIXME: what about other types? */
 562                 if(rrset->type==LDNS_RR_TYPE_A ||
 563                         rrset->type==LDNS_RR_TYPE_AAAA)
 564                 {
 565                         if((rrset->flags & RRSET_SCRUB_OK)) {
 566                                 /* remove flag to clean up flags variable */
 567                                 rrset->flags &= ~RRSET_SCRUB_OK;
 568                         } else {
 569                                 remove_rrset("normalize: removing irrelevant "
 570                                         "RRset:", pkt, msg, prev, &rrset);
 571                                 continue;
 572                         }
 573                 }
 574                 if(rrset->type==LDNS_RR_TYPE_DNAME ||
 575                         rrset->type==LDNS_RR_TYPE_CNAME ||
 576                         rrset->type==LDNS_RR_TYPE_NS) {
 577                         remove_rrset("normalize: removing irrelevant "
 578                                 "RRset:", pkt, msg, prev, &rrset);
 579                         continue;
 580                 }
 581                 prev = rrset;
 582                 rrset = rrset->rrset_all_next;
 583         }
 584
 585         return 1;
 586 }
 587
 588 /**
 589  * Store potential poison in the cache (only if hardening disabled).
 590  * The rrset is stored in the cache but removed from the message.
 591  * So that it will be used for infrastructure purposes, but not be
 592  * returned to the client.
 593  * @param pkt: packet
 594  * @param msg: message parsed
 595  * @param env: environment with cache
 596  * @param rrset: to store.
 597  */
 598 static void
 599 store_rrset(sldns_buffer* pkt, struct msg_parse* msg, struct module_env* env,
 600         struct rrset_parse* rrset)
 601 {
 602         struct ub_packed_rrset_key* k;
 603         struct packed_rrset_data* d;
 604         struct rrset_ref ref;
 605         time_t now = *env->now;
 606
 607         k = alloc_special_obtain(env->alloc);
 608         if(!k)
 609                 return;
 610         k->entry.data = NULL;
 611         if(!parse_copy_decompress_rrset(pkt, msg, rrset, NULL, k)) {
 612                 alloc_special_release(env->alloc, k);
 613                 return;
 614         }
 615         d = (struct packed_rrset_data*)k->entry.data;
 616         packed_rrset_ttl_add(d, now);
 617         ref.key = k;
 618         ref.id = k->id;
 619         /*ignore ret: it was in the cache, ref updated */
 620         (void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, now);
 621 }
 622
 623 /**
 624  * Check if right hand name in NSEC is within zone
 625  * @param rrset: the NSEC rrset
 626  * @param zonename: the zone name.
 627  * @return true if BAD.
 628  */
 629 static int sanitize_nsec_is_overreach(struct rrset_parse* rrset,
 630         uint8_t* zonename)
 631 {
 632         struct rr_parse* rr;
 633         uint8_t* rhs;
 634         size_t len;
 635         log_assert(rrset->type == LDNS_RR_TYPE_NSEC);
 636         for(rr = rrset->rr_first; rr; rr = rr->next) {
 637                 rhs = rr->ttl_data+4+2;
 638                 len = sldns_read_uint16(rr->ttl_data+4);
 639                 if(!dname_valid(rhs, len)) {
 640                         /* malformed domain name in rdata */
 641                         return 1;
 642                 }
 643                 if(!dname_subdomain_c(rhs, zonename)) {
 644                         /* overreaching */
 645                         return 1;
 646                 }
 647         }
 648         /* all NSEC RRs OK */
 649         return 0;
 650 }
 651
 652 /**
 653  * Given a response event, remove suspect RRsets from the response.
 654  * "Suspect" rrsets are potentially poison. Note that this routine expects
 655  * the response to be in a "normalized" state -- that is, all "irrelevant"
 656  * RRsets have already been removed, CNAMEs are in order, etc.
 657  *
 658  * @param pkt: packet.
 659  * @param msg: msg to normalize.
 660  * @param qinfo: the question originally asked.
 661  * @param zonename: name of server zone.
 662  * @param env: module environment with config and cache.
 663  * @param ie: iterator environment with private address data.
 664  * @return 0 on error.
 665  */
 666 static int
 667 scrub_sanitize(sldns_buffer* pkt, struct msg_parse* msg,
 668         struct query_info* qinfo, uint8_t* zonename, struct module_env* env,
 669         struct iter_env* ie)
 670 {
 671         int del_addi = 0; /* if additional-holding rrsets are deleted, we
 672                 do not trust the normalized additional-A-AAAA any more */
 673         struct rrset_parse* rrset, *prev;
 674         prev = NULL;
 675         rrset = msg->rrset_first;
 676
 677         /* the first DNAME is allowed to stay. It needs checking before
 678          * it can be used from the cache. After normalization, an initial
 679          * DNAME will have a correctly synthesized CNAME after it. */
 680         if(rrset && rrset->type == LDNS_RR_TYPE_DNAME &&
 681                 rrset->section == LDNS_SECTION_ANSWER &&
 682                 pkt_strict_sub(pkt, qinfo->qname, rrset->dname) &&
 683                 pkt_sub(pkt, rrset->dname, zonename)) {
 684                 prev = rrset; /* DNAME allowed to stay in answer section */
 685                 rrset = rrset->rrset_all_next;
 686         }
 687
 688         /* remove all records from the answer section that are
 689          * not the same domain name as the query domain name.
 690          * The answer section should contain rrsets with the same name
 691          * as the question. For DNAMEs a CNAME has been synthesized.
 692          * Wildcards have the query name in answer section.
 693          * ANY queries get query name in answer section.
 694          * Remainders of CNAME chains are cut off and resolved by iterator. */
 695         while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
 696                 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) != 0) {
 697                         if(has_additional(rrset->type)) del_addi = 1;
 698                         remove_rrset("sanitize: removing extraneous answer "
 699                                 "RRset:", pkt, msg, prev, &rrset);
 700                         continue;
 701                 }
 702                 prev = rrset;
 703                 rrset = rrset->rrset_all_next;
 704         }
 705
 706         /* At this point, we brutally remove ALL rrsets that aren't
 707          * children of the originating zone. The idea here is that,
 708          * as far as we know, the server that we contacted is ONLY
 709          * authoritative for the originating zone. It, of course, MAY
 710          * be authoritative for any other zones, and of course, MAY
 711          * NOT be authoritative for some subdomains of the originating
 712          * zone. */
 713         prev = NULL;
 714         rrset = msg->rrset_first;
 715         while(rrset) {
 716
 717                 /* remove private addresses */
 718                 if( (rrset->type == LDNS_RR_TYPE_A ||
 719                         rrset->type == LDNS_RR_TYPE_AAAA)) {
 720
 721                         /* do not set servfail since this leads to too
 722                          * many drops of other people using rfc1918 space */
 723                         /* also do not remove entire rrset, unless all records
 724                          * in it are bad */
 725                         if(priv_rrset_bad(ie->priv, pkt, rrset)) {
 726                                 remove_rrset(NULL, pkt, msg, prev, &rrset);
 727                                 continue;
 728                         }
 729                 }
 730
 731                 /* skip DNAME records -- they will always be followed by a
 732                  * synthesized CNAME, which will be relevant.
 733                  * FIXME: should this do something differently with DNAME
 734                  * rrsets NOT in Section.ANSWER? */
 735                 /* But since DNAME records are also subdomains of the zone,
 736                  * same check can be used */
 737
 738                 if(!pkt_sub(pkt, rrset->dname, zonename)) {
 739                         if(msg->an_rrsets == 0 &&
 740                                 rrset->type == LDNS_RR_TYPE_NS &&
 741                                 rrset->section == LDNS_SECTION_AUTHORITY &&
 742                                 FLAGS_GET_RCODE(msg->flags) ==
 743                                 LDNS_RCODE_NOERROR && !soa_in_auth(msg) &&
 744                                 sub_of_pkt(pkt, zonename, rrset->dname)) {
 745                                 /* noerror, nodata and this NS rrset is above
 746                                  * the zone. This is LAME!
 747                                  * Leave in the NS for lame classification. */
 748                                 /* remove everything from the additional
 749                                  * (we dont want its glue that was approved
 750                                  * during the normalize action) */
 751                                 del_addi = 1;
 752                         } else if(!env->cfg->harden_glue && (
 753                                 rrset->type == LDNS_RR_TYPE_A ||
 754                                 rrset->type == LDNS_RR_TYPE_AAAA)) {
 755                                 /* store in cache! Since it is relevant
 756                                  * (from normalize) it will be picked up
 757                                  * from the cache to be used later */
 758                                 store_rrset(pkt, msg, env, rrset);
 759                                 remove_rrset("sanitize: storing potential "
 760                                 "poison RRset:", pkt, msg, prev, &rrset);
 761                                 continue;
 762                         } else {
 763                                 if(has_additional(rrset->type)) del_addi = 1;
 764                                 remove_rrset("sanitize: removing potential "
 765                                 "poison RRset:", pkt, msg, prev, &rrset);
 766                                 continue;
 767                         }
 768                 }
 769                 if(del_addi && rrset->section == LDNS_SECTION_ADDITIONAL) {
 770                         remove_rrset("sanitize: removing potential "
 771                         "poison reference RRset:", pkt, msg, prev, &rrset);
 772                         continue;
 773                 }
 774                 /* check if right hand side of NSEC is within zone */
 775                 if(rrset->type == LDNS_RR_TYPE_NSEC &&
 776                         sanitize_nsec_is_overreach(rrset, zonename)) {
 777                         remove_rrset("sanitize: removing overreaching NSEC "
 778                                 "RRset:", pkt, msg, prev, &rrset);
 779                         continue;
 780                 }
 781                 prev = rrset;
 782                 rrset = rrset->rrset_all_next;
 783         }
 784         return 1;
 785 }
 786
 787 int
 788 scrub_message(sldns_buffer* pkt, struct msg_parse* msg,
 789         struct query_info* qinfo, uint8_t* zonename, struct regional* region,
 790         struct module_env* env, struct iter_env* ie)
 791 {
 792         /* basic sanity checks */
 793         log_nametypeclass(VERB_ALGO, "scrub for", zonename, LDNS_RR_TYPE_NS,
 794                 qinfo->qclass);
 795         if(msg->qdcount > 1)
 796                 return 0;
 797         if( !(msg->flags&BIT_QR) )
 798                 return 0;
 799         msg->flags &= ~(BIT_AD|BIT_Z); /* force off bit AD and Z */
 800
 801         /* make sure that a query is echoed back when NOERROR or NXDOMAIN */
 802         /* this is not required for basic operation but is a forgery
 803          * resistance (security) feature */
 804         if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR ||
 805                 FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) &&
 806                 msg->qdcount == 0)
 807                 return 0;
 808
 809         /* if a query is echoed back, make sure it is correct. Otherwise,
 810          * this may be not a reply to our query. */
 811         if(msg->qdcount == 1) {
 812                 if(dname_pkt_compare(pkt, msg->qname, qinfo->qname) != 0)
 813                         return 0;
 814                 if(msg->qtype != qinfo->qtype || msg->qclass != qinfo->qclass)
 815                         return 0;
 816         }
 817
 818         /* normalize the response, this cleans up the additional.  */
 819         if(!scrub_normalize(pkt, msg, qinfo, region))
 820                 return 0;
 821         /* delete all out-of-zone information */
 822         if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie))
 823                 return 0;
 824         return 1;
 825 }