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