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         if(qnamelen <= dname_rrset->dname_len)
 221                 return 0;
 222         if(qnamelen == 0)
 223                 return 0;
 224         log_assert(qnamelen > dname_rrset->dname_len);
 225         /* DNAME from com. to net. with qname example.com. -> example.net. */
 226         /* so: \3com\0 to \3net\0 and qname \7example\3com\0 */
 227         *aliaslen = qnamelen + dtarglen - dname_rrset->dname_len;
 228         if(*aliaslen > LDNS_MAX_DOMAINLEN)
 229                 return 0; /* should have been RCODE YXDOMAIN */
 230         /* decompress dnames into buffer, we know it fits */
 231         dname_pkt_copy(pkt, alias, qname);
 232         dname_pkt_copy(pkt, alias+(qnamelen-dname_rrset->dname_len), dtarg);
 233         return 1;
 234 }
 235
 236 /** synthesize a CNAME rrset */
 237 static struct rrset_parse*
 238 synth_cname_rrset(uint8_t** sname, size_t* snamelen, uint8_t* alias,
 239         size_t aliaslen, struct regional* region, struct msg_parse* msg,
 240         struct rrset_parse* rrset, struct rrset_parse* prev,
 241         struct rrset_parse* nx, sldns_buffer* pkt)
 242 {
 243         struct rrset_parse* cn = (struct rrset_parse*)regional_alloc(region,
 244                 sizeof(struct rrset_parse));
 245         if(!cn)
 246                 return NULL;
 247         memset(cn, 0, sizeof(*cn));
 248         cn->rr_first = (struct rr_parse*)regional_alloc(region,
 249                 sizeof(struct rr_parse));
 250         if(!cn->rr_first)
 251                 return NULL;
 252         cn->rr_last = cn->rr_first;
 253         /* CNAME from sname to alias */
 254         cn->dname = (uint8_t*)regional_alloc(region, *snamelen);
 255         if(!cn->dname)
 256                 return NULL;
 257         dname_pkt_copy(pkt, cn->dname, *sname);
 258         cn->dname_len = *snamelen;
 259         cn->type = LDNS_RR_TYPE_CNAME;
 260         cn->section = rrset->section;
 261         cn->rrset_class = rrset->rrset_class;
 262         cn->rr_count = 1;
 263         cn->size = sizeof(uint16_t) + aliaslen;
 264         cn->hash=pkt_hash_rrset(pkt, cn->dname, cn->type, cn->rrset_class, 0);
 265         /* allocate TTL + rdatalen + uncompressed dname */
 266         memset(cn->rr_first, 0, sizeof(struct rr_parse));
 267         cn->rr_first->outside_packet = 1;
 268         cn->rr_first->ttl_data = (uint8_t*)regional_alloc(region,
 269                 sizeof(uint32_t)+sizeof(uint16_t)+aliaslen);
 270         if(!cn->rr_first->ttl_data)
 271                 return NULL;
 272         sldns_write_uint32(cn->rr_first->ttl_data, 0); /* TTL = 0 */
 273         sldns_write_uint16(cn->rr_first->ttl_data+4, aliaslen);
 274         memmove(cn->rr_first->ttl_data+6, alias, aliaslen);
 275         cn->rr_first->size = sizeof(uint16_t)+aliaslen;
 276
 277         /* link it in */
 278         cn->rrset_all_next = nx;
 279         if(prev)
 280                 prev->rrset_all_next = cn;
 281         else    msg->rrset_first = cn;
 282         if(nx == NULL)
 283                 msg->rrset_last = cn;
 284         msg->rrset_count ++;
 285         msg->an_rrsets++;
 286         /* it is not inserted in the msg hashtable. */
 287
 288         *sname = cn->rr_first->ttl_data + sizeof(uint32_t)+sizeof(uint16_t);
 289         *snamelen = aliaslen;
 290         return cn;
 291 }
 292
 293 /** check if DNAME applies to a name */
 294 static int
 295 pkt_strict_sub(sldns_buffer* pkt, uint8_t* sname, uint8_t* dr)
 296 {
 297         uint8_t buf1[LDNS_MAX_DOMAINLEN+1];
 298         uint8_t buf2[LDNS_MAX_DOMAINLEN+1];
 299         /* decompress names */
 300         dname_pkt_copy(pkt, buf1, sname);
 301         dname_pkt_copy(pkt, buf2, dr);
 302         return dname_strict_subdomain_c(buf1, buf2);
 303 }
 304
 305 /** check subdomain with decompression */
 306 static int
 307 pkt_sub(sldns_buffer* pkt, uint8_t* comprname, uint8_t* zone)
 308 {
 309         uint8_t buf[LDNS_MAX_DOMAINLEN+1];
 310         dname_pkt_copy(pkt, buf, comprname);
 311         return dname_subdomain_c(buf, zone);
 312 }
 313
 314 /** check subdomain with decompression, compressed is parent */
 315 static int
 316 sub_of_pkt(sldns_buffer* pkt, uint8_t* zone, uint8_t* comprname)
 317 {
 318         uint8_t buf[LDNS_MAX_DOMAINLEN+1];
 319         dname_pkt_copy(pkt, buf, comprname);
 320         return dname_subdomain_c(zone, buf);
 321 }
 322
 323 /** Check if there are SOA records in the authority section (negative) */
 324 static int
 325 soa_in_auth(struct msg_parse* msg)
 326 {
 327         struct rrset_parse* rrset;
 328         for(rrset = msg->rrset_first; rrset; rrset = rrset->rrset_all_next)
 329                 if(rrset->type == LDNS_RR_TYPE_SOA &&
 330                         rrset->section == LDNS_SECTION_AUTHORITY)
 331                         return 1;
 332         return 0;
 333 }
 334
 335 /**
 336  * This routine normalizes a response. This includes removing "irrelevant"
 337  * records from the answer and additional sections and (re)synthesizing
 338  * CNAMEs from DNAMEs, if present.
 339  *
 340  * @param pkt: packet.
 341  * @param msg: msg to normalize.
 342  * @param qinfo: original query.
 343  * @param region: where to allocate synthesized CNAMEs.
 344  * @return 0 on error.
 345  */
 346 static int
 347 scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg,
 348         struct query_info* qinfo, struct regional* region)
 349 {
 350         uint8_t* sname = qinfo->qname;
 351         size_t snamelen = qinfo->qname_len;
 352         struct rrset_parse* rrset, *prev, *nsset=NULL;
 353
 354         if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR &&
 355                 FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN)
 356                 return 1;
 357
 358         /* For the ANSWER section, remove all "irrelevant" records and add
 359          * synthesized CNAMEs from DNAMEs
 360          * This will strip out-of-order CNAMEs as well. */
 361
 362         /* walk through the parse packet rrset list, keep track of previous
 363          * for insert and delete ease, and examine every RRset */
 364         prev = NULL;
 365         rrset = msg->rrset_first;
 366         while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
 367                 if(rrset->type == LDNS_RR_TYPE_DNAME &&
 368                         pkt_strict_sub(pkt, sname, rrset->dname)) {
 369                         /* check if next rrset is correct CNAME. else,
 370                          * synthesize a CNAME */
 371                         struct rrset_parse* nx = rrset->rrset_all_next;
 372                         uint8_t alias[LDNS_MAX_DOMAINLEN+1];
 373                         size_t aliaslen = 0;
 374                         if(rrset->rr_count != 1) {
 375                                 verbose(VERB_ALGO, "Found DNAME rrset with "
 376                                         "size > 1: %u",
 377                                         (unsigned)rrset->rr_count);
 378                                 return 0;
 379                         }
 380                         if(!synth_cname(sname, snamelen, rrset, alias,
 381                                 &aliaslen, pkt)) {
 382                                 verbose(VERB_ALGO, "synthesized CNAME "
 383                                         "too long");
 384                                 return 0;
 385                         }
 386                         if(nx && nx->type == LDNS_RR_TYPE_CNAME &&
 387                            dname_pkt_compare(pkt, sname, nx->dname) == 0) {
 388                                 /* check next cname */
 389                                 uint8_t* t = NULL;
 390                                 size_t tlen = 0;
 391                                 if(!parse_get_cname_target(nx, &t, &tlen))
 392                                         return 0;
 393                                 if(dname_pkt_compare(pkt, alias, t) == 0) {
 394                                         /* it's OK and better capitalized */
 395                                         prev = rrset;
 396                                         rrset = nx;
 397                                         continue;
 398                                 }
 399                                 /* synth ourselves */
 400                         }
 401                         /* synth a CNAME rrset */
 402                         prev = synth_cname_rrset(&sname, &snamelen, alias,
 403                                 aliaslen, region, msg, rrset, rrset, nx, pkt);
 404                         if(!prev) {
 405                                 log_err("out of memory synthesizing CNAME");
 406                                 return 0;
 407                         }
 408                         /* FIXME: resolve the conflict between synthesized
 409                          * CNAME ttls and the cache. */
 410                         rrset = nx;
 411                         continue;
 412
 413                 }
 414
 415                 /* The only records in the ANSWER section not allowed to */
 416                 if(dname_pkt_compare(pkt, sname, rrset->dname) != 0) {
 417                         remove_rrset("normalize: removing irrelevant RRset:",
 418                                 pkt, msg, prev, &rrset);
 419                         continue;
 420                 }
 421
 422                 /* Follow the CNAME chain. */
 423                 if(rrset->type == LDNS_RR_TYPE_CNAME) {
 424                         struct rrset_parse* nx = rrset->rrset_all_next;
 425                         uint8_t* oldsname = sname;
 426                         /* see if the next one is a DNAME, if so, swap them */
 427                         if(nx && nx->section == LDNS_SECTION_ANSWER &&
 428                                 nx->type == LDNS_RR_TYPE_DNAME &&
 429                                 nx->rr_count == 1 &&
 430                                 pkt_strict_sub(pkt, sname, nx->dname)) {
 431                                 /* there is a DNAME after this CNAME, it
 432                                  * is in the ANSWER section, and the DNAME
 433                                  * applies to the name we cover */
 434                                 /* check if the alias of the DNAME equals
 435                                  * this CNAME */
 436                                 uint8_t alias[LDNS_MAX_DOMAINLEN+1];
 437                                 size_t aliaslen = 0;
 438                                 uint8_t* t = NULL;
 439                                 size_t tlen = 0;
 440                                 if(synth_cname(sname, snamelen, nx, alias,
 441                                         &aliaslen, pkt) &&
 442                                         parse_get_cname_target(rrset, &t, &tlen) &&
 443                                         dname_pkt_compare(pkt, alias, t) == 0) {
 444                                         /* the synthesized CNAME equals the
 445                                          * current CNAME.  This CNAME is the
 446                                          * one that the DNAME creates, and this
 447                                          * CNAME is better capitalised */
 448                                         verbose(VERB_ALGO, "normalize: re-order of DNAME and its CNAME");
 449                                         if(prev) prev->rrset_all_next = nx;
 450                                         else msg->rrset_first = nx;
 451                                         if(nx->rrset_all_next == NULL)
 452                                                 msg->rrset_last = rrset;
 453                                         rrset->rrset_all_next =
 454                                                 nx->rrset_all_next;
 455                                         nx->rrset_all_next = rrset;
 456                                         /* prev = nx; unused, enable if there
 457                                          * is other rrset removal code after
 458                                          * this */
 459                                 }
 460                         }
 461
 462                         /* move to next name in CNAME chain */
 463                         if(!parse_get_cname_target(rrset, &sname, &snamelen))
 464                                 return 0;
 465                         prev = rrset;
 466                         rrset = rrset->rrset_all_next;
 467                         /* in CNAME ANY response, can have data after CNAME */
 468                         if(qinfo->qtype == LDNS_RR_TYPE_ANY) {
 469                                 while(rrset && rrset->section ==
 470                                         LDNS_SECTION_ANSWER &&
 471                                         dname_pkt_compare(pkt, oldsname,
 472                                         rrset->dname) == 0) {
 473                                         prev = rrset;
 474                                         rrset = rrset->rrset_all_next;
 475                                 }
 476                         }
 477                         continue;
 478                 }
 479
 480                 /* Otherwise, make sure that the RRset matches the qtype. */
 481                 if(qinfo->qtype != LDNS_RR_TYPE_ANY &&
 482                         qinfo->qtype != rrset->type) {
 483                         remove_rrset("normalize: removing irrelevant RRset:",
 484                                 pkt, msg, prev, &rrset);
 485                         continue;
 486                 }
 487
 488                 /* Mark the additional names from relevant rrset as OK. */
 489                 /* only for RRsets that match the query name, other ones
 490                  * will be removed by sanitize, so no additional for them */
 491                 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0)
 492                         mark_additional_rrset(pkt, msg, rrset);
 493
 494                 prev = rrset;
 495                 rrset = rrset->rrset_all_next;
 496         }
 497
 498         /* Mark additional names from AUTHORITY */
 499         while(rrset && rrset->section == LDNS_SECTION_AUTHORITY) {
 500                 if(rrset->type==LDNS_RR_TYPE_DNAME ||
 501                         rrset->type==LDNS_RR_TYPE_CNAME ||
 502                         rrset->type==LDNS_RR_TYPE_A ||
 503                         rrset->type==LDNS_RR_TYPE_AAAA) {
 504                         remove_rrset("normalize: removing irrelevant "
 505                                 "RRset:", pkt, msg, prev, &rrset);
 506                         continue;
 507                 }
 508                 /* only one NS set allowed in authority section */
 509                 if(rrset->type==LDNS_RR_TYPE_NS) {
 510                         /* NS set must be pertinent to the query */
 511                         if(!sub_of_pkt(pkt, qinfo->qname, rrset->dname)) {
 512                                 remove_rrset("normalize: removing irrelevant "
 513                                         "RRset:", pkt, msg, prev, &rrset);
 514                                 continue;
 515                         }
 516                         /* we don't want NS sets for NXDOMAIN answers,
 517                          * because they could contain poisonous contents,
 518                          * from. eg. fragmentation attacks, inserted after
 519                          * long RRSIGs in the packet get to the packet
 520                          * border and such */
 521                         /* also for NODATA answers */
 522                         if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN ||
 523                            (FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR
 524                             && soa_in_auth(msg) && msg->an_rrsets == 0)) {
 525                                 remove_rrset("normalize: removing irrelevant "
 526                                         "RRset:", pkt, msg, prev, &rrset);
 527                                 continue;
 528                         }
 529                         if(nsset == NULL) {
 530                                 nsset = rrset;
 531                         } else {
 532                                 remove_rrset("normalize: removing irrelevant "
 533                                         "RRset:", pkt, msg, prev, &rrset);
 534                                 continue;
 535                         }
 536                 }
 537                 /* if this is type DS and we query for type DS we just got
 538                  * a referral answer for our type DS query, fix packet */
 539                 if(rrset->type==LDNS_RR_TYPE_DS &&
 540                         qinfo->qtype == LDNS_RR_TYPE_DS &&
 541                         dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0) {
 542                         rrset->section = LDNS_SECTION_ANSWER;
 543                         msg->ancount = rrset->rr_count + rrset->rrsig_count;
 544                         msg->nscount = 0;
 545                         msg->arcount = 0;
 546                         msg->an_rrsets = 1;
 547                         msg->ns_rrsets = 0;
 548                         msg->ar_rrsets = 0;
 549                         msg->rrset_count = 1;
 550                         msg->rrset_first = rrset;
 551                         msg->rrset_last = rrset;
 552                         rrset->rrset_all_next = NULL;
 553                         return 1;
 554                 }
 555                 mark_additional_rrset(pkt, msg, rrset);
 556                 prev = rrset;
 557                 rrset = rrset->rrset_all_next;
 558         }
 559
 560         /* For each record in the additional section, remove it if it is an
 561          * address record and not in the collection of additional names
 562          * found in ANSWER and AUTHORITY. */
 563         /* These records have not been marked OK previously */
 564         while(rrset && rrset->section == LDNS_SECTION_ADDITIONAL) {
 565                 /* FIXME: what about other types? */
 566                 if(rrset->type==LDNS_RR_TYPE_A ||
 567                         rrset->type==LDNS_RR_TYPE_AAAA)
 568                 {
 569                         if((rrset->flags & RRSET_SCRUB_OK)) {
 570                                 /* remove flag to clean up flags variable */
 571                                 rrset->flags &= ~RRSET_SCRUB_OK;
 572                         } else {
 573                                 remove_rrset("normalize: removing irrelevant "
 574                                         "RRset:", pkt, msg, prev, &rrset);
 575                                 continue;
 576                         }
 577                 }
 578                 if(rrset->type==LDNS_RR_TYPE_DNAME ||
 579                         rrset->type==LDNS_RR_TYPE_CNAME ||
 580                         rrset->type==LDNS_RR_TYPE_NS) {
 581                         remove_rrset("normalize: removing irrelevant "
 582                                 "RRset:", pkt, msg, prev, &rrset);
 583                         continue;
 584                 }
 585                 prev = rrset;
 586                 rrset = rrset->rrset_all_next;
 587         }
 588
 589         return 1;
 590 }
 591
 592 /**
 593  * Store potential poison in the cache (only if hardening disabled).
 594  * The rrset is stored in the cache but removed from the message.
 595  * So that it will be used for infrastructure purposes, but not be
 596  * returned to the client.
 597  * @param pkt: packet
 598  * @param msg: message parsed
 599  * @param env: environment with cache
 600  * @param rrset: to store.
 601  */
 602 static void
 603 store_rrset(sldns_buffer* pkt, struct msg_parse* msg, struct module_env* env,
 604         struct rrset_parse* rrset)
 605 {
 606         struct ub_packed_rrset_key* k;
 607         struct packed_rrset_data* d;
 608         struct rrset_ref ref;
 609         time_t now = *env->now;
 610
 611         k = alloc_special_obtain(env->alloc);
 612         if(!k)
 613                 return;
 614         k->entry.data = NULL;
 615         if(!parse_copy_decompress_rrset(pkt, msg, rrset, NULL, k)) {
 616                 alloc_special_release(env->alloc, k);
 617                 return;
 618         }
 619         d = (struct packed_rrset_data*)k->entry.data;
 620         packed_rrset_ttl_add(d, now);
 621         ref.key = k;
 622         ref.id = k->id;
 623         /*ignore ret: it was in the cache, ref updated */
 624         (void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, now);
 625 }
 626
 627 /**
 628  * Check if right hand name in NSEC is within zone
 629  * @param rrset: the NSEC rrset
 630  * @param zonename: the zone name.
 631  * @return true if BAD.
 632  */
 633 static int sanitize_nsec_is_overreach(struct rrset_parse* rrset,
 634         uint8_t* zonename)
 635 {
 636         struct rr_parse* rr;
 637         uint8_t* rhs;
 638         size_t len;
 639         log_assert(rrset->type == LDNS_RR_TYPE_NSEC);
 640         for(rr = rrset->rr_first; rr; rr = rr->next) {
 641                 rhs = rr->ttl_data+4+2;
 642                 len = sldns_read_uint16(rr->ttl_data+4);
 643                 if(!dname_valid(rhs, len)) {
 644                         /* malformed domain name in rdata */
 645                         return 1;
 646                 }
 647                 if(!dname_subdomain_c(rhs, zonename)) {
 648                         /* overreaching */
 649                         return 1;
 650                 }
 651         }
 652         /* all NSEC RRs OK */
 653         return 0;
 654 }
 655
 656 /**
 657  * Given a response event, remove suspect RRsets from the response.
 658  * "Suspect" rrsets are potentially poison. Note that this routine expects
 659  * the response to be in a "normalized" state -- that is, all "irrelevant"
 660  * RRsets have already been removed, CNAMEs are in order, etc.
 661  *
 662  * @param pkt: packet.
 663  * @param msg: msg to normalize.
 664  * @param qinfo: the question originally asked.
 665  * @param zonename: name of server zone.
 666  * @param env: module environment with config and cache.
 667  * @param ie: iterator environment with private address data.
 668  * @return 0 on error.
 669  */
 670 static int
 671 scrub_sanitize(sldns_buffer* pkt, struct msg_parse* msg,
 672         struct query_info* qinfo, uint8_t* zonename, struct module_env* env,
 673         struct iter_env* ie)
 674 {
 675         int del_addi = 0; /* if additional-holding rrsets are deleted, we
 676                 do not trust the normalized additional-A-AAAA any more */
 677         struct rrset_parse* rrset, *prev;
 678         prev = NULL;
 679         rrset = msg->rrset_first;
 680
 681         /* the first DNAME is allowed to stay. It needs checking before
 682          * it can be used from the cache. After normalization, an initial
 683          * DNAME will have a correctly synthesized CNAME after it. */
 684         if(rrset && rrset->type == LDNS_RR_TYPE_DNAME &&
 685                 rrset->section == LDNS_SECTION_ANSWER &&
 686                 pkt_strict_sub(pkt, qinfo->qname, rrset->dname) &&
 687                 pkt_sub(pkt, rrset->dname, zonename)) {
 688                 prev = rrset; /* DNAME allowed to stay in answer section */
 689                 rrset = rrset->rrset_all_next;
 690         }
 691
 692         /* remove all records from the answer section that are
 693          * not the same domain name as the query domain name.
 694          * The answer section should contain rrsets with the same name
 695          * as the question. For DNAMEs a CNAME has been synthesized.
 696          * Wildcards have the query name in answer section.
 697          * ANY queries get query name in answer section.
 698          * Remainders of CNAME chains are cut off and resolved by iterator. */
 699         while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
 700                 if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) != 0) {
 701                         if(has_additional(rrset->type)) del_addi = 1;
 702                         remove_rrset("sanitize: removing extraneous answer "
 703                                 "RRset:", pkt, msg, prev, &rrset);
 704                         continue;
 705                 }
 706                 prev = rrset;
 707                 rrset = rrset->rrset_all_next;
 708         }
 709
 710         /* At this point, we brutally remove ALL rrsets that aren't
 711          * children of the originating zone. The idea here is that,
 712          * as far as we know, the server that we contacted is ONLY
 713          * authoritative for the originating zone. It, of course, MAY
 714          * be authoritative for any other zones, and of course, MAY
 715          * NOT be authoritative for some subdomains of the originating
 716          * zone. */
 717         prev = NULL;
 718         rrset = msg->rrset_first;
 719         while(rrset) {
 720
 721                 /* remove private addresses */
 722                 if( (rrset->type == LDNS_RR_TYPE_A ||
 723                         rrset->type == LDNS_RR_TYPE_AAAA)) {
 724
 725                         /* do not set servfail since this leads to too
 726                          * many drops of other people using rfc1918 space */
 727                         /* also do not remove entire rrset, unless all records
 728                          * in it are bad */
 729                         if(priv_rrset_bad(ie->priv, pkt, rrset)) {
 730                                 remove_rrset(NULL, pkt, msg, prev, &rrset);
 731                                 continue;
 732                         }
 733                 }
 734
 735                 /* skip DNAME records -- they will always be followed by a
 736                  * synthesized CNAME, which will be relevant.
 737                  * FIXME: should this do something differently with DNAME
 738                  * rrsets NOT in Section.ANSWER? */
 739                 /* But since DNAME records are also subdomains of the zone,
 740                  * same check can be used */
 741
 742                 if(!pkt_sub(pkt, rrset->dname, zonename)) {
 743                         if(msg->an_rrsets == 0 &&
 744                                 rrset->type == LDNS_RR_TYPE_NS &&
 745                                 rrset->section == LDNS_SECTION_AUTHORITY &&
 746                                 FLAGS_GET_RCODE(msg->flags) ==
 747                                 LDNS_RCODE_NOERROR && !soa_in_auth(msg) &&
 748                                 sub_of_pkt(pkt, zonename, rrset->dname)) {
 749                                 /* noerror, nodata and this NS rrset is above
 750                                  * the zone. This is LAME!
 751                                  * Leave in the NS for lame classification. */
 752                                 /* remove everything from the additional
 753                                  * (we dont want its glue that was approved
 754                                  * during the normalize action) */
 755                                 del_addi = 1;
 756                         } else if(!env->cfg->harden_glue && (
 757                                 rrset->type == LDNS_RR_TYPE_A ||
 758                                 rrset->type == LDNS_RR_TYPE_AAAA)) {
 759                                 /* store in cache! Since it is relevant
 760                                  * (from normalize) it will be picked up
 761                                  * from the cache to be used later */
 762                                 store_rrset(pkt, msg, env, rrset);
 763                                 remove_rrset("sanitize: storing potential "
 764                                 "poison RRset:", pkt, msg, prev, &rrset);
 765                                 continue;
 766                         } else {
 767                                 if(has_additional(rrset->type)) del_addi = 1;
 768                                 remove_rrset("sanitize: removing potential "
 769                                 "poison RRset:", pkt, msg, prev, &rrset);
 770                                 continue;
 771                         }
 772                 }
 773                 if(del_addi && rrset->section == LDNS_SECTION_ADDITIONAL) {
 774                         remove_rrset("sanitize: removing potential "
 775                         "poison reference RRset:", pkt, msg, prev, &rrset);
 776                         continue;
 777                 }
 778                 /* check if right hand side of NSEC is within zone */
 779                 if(rrset->type == LDNS_RR_TYPE_NSEC &&
 780                         sanitize_nsec_is_overreach(rrset, zonename)) {
 781                         remove_rrset("sanitize: removing overreaching NSEC "
 782                                 "RRset:", pkt, msg, prev, &rrset);
 783                         continue;
 784                 }
 785                 prev = rrset;
 786                 rrset = rrset->rrset_all_next;
 787         }
 788         return 1;
 789 }
 790
 791 int
 792 scrub_message(sldns_buffer* pkt, struct msg_parse* msg,
 793         struct query_info* qinfo, uint8_t* zonename, struct regional* region,
 794         struct module_env* env, struct iter_env* ie)
 795 {
 796         /* basic sanity checks */
 797         log_nametypeclass(VERB_ALGO, "scrub for", zonename, LDNS_RR_TYPE_NS,
 798                 qinfo->qclass);
 799         if(msg->qdcount > 1)
 800                 return 0;
 801         if( !(msg->flags&BIT_QR) )
 802                 return 0;
 803         msg->flags &= ~(BIT_AD|BIT_Z); /* force off bit AD and Z */
 804
 805         /* make sure that a query is echoed back when NOERROR or NXDOMAIN */
 806         /* this is not required for basic operation but is a forgery
 807          * resistance (security) feature */
 808         if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR ||
 809                 FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) &&
 810                 msg->qdcount == 0)
 811                 return 0;
 812
 813         /* if a query is echoed back, make sure it is correct. Otherwise,
 814          * this may be not a reply to our query. */
 815         if(msg->qdcount == 1) {
 816                 if(dname_pkt_compare(pkt, msg->qname, qinfo->qname) != 0)
 817                         return 0;
 818                 if(msg->qtype != qinfo->qtype || msg->qclass != qinfo->qclass)
 819                         return 0;
 820         }
 821
 822         /* normalize the response, this cleans up the additional.  */
 823         if(!scrub_normalize(pkt, msg, qinfo, region))
 824                 return 0;
 825         /* delete all out-of-zone information */
 826         if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie))
 827                 return 0;
 828         return 1;
 829 }