1/* 2 * validator/val_nsec.c - validator NSEC denial of existence functions. 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 contains helper functions for the validator module. 40 * The functions help with NSEC checking, the different NSEC proofs 41 * for denial of existence, and proofs for presence of types. 42 */ 43#include "config.h" 44#include "validator/val_nsec.h" 45#include "validator/val_utils.h" 46#include "util/data/msgreply.h" 47#include "util/data/dname.h" 48#include "util/net_help.h" 49#include "util/module.h" 50#include "services/cache/rrset.h" 51 52/** get ttl of rrset */ 53static uint32_t 54rrset_get_ttl(struct ub_packed_rrset_key* k) 55{ 56 struct packed_rrset_data* d = (struct packed_rrset_data*)k->entry.data; 57 return d->ttl; 58} 59 60int 61nsecbitmap_has_type_rdata(uint8_t* bitmap, size_t len, uint16_t type) 62{ 63 /* Check type present in NSEC typemap with bitmap arg */ 64 /* bitmasks for determining type-lowerbits presence */ 65 uint8_t masks[8] = {0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01}; 66 uint8_t type_window = type>>8; 67 uint8_t type_low = type&0xff; 68 uint8_t win, winlen; 69 /* read each of the type bitmap windows and see if the searched 70 * type is amongst it */ 71 while(len > 0) { 72 if(len < 3) /* bad window, at least window# winlen bitmap */ 73 return 0; 74 win = *bitmap++; 75 winlen = *bitmap++; 76 len -= 2; 77 if(len < winlen || winlen < 1 || winlen > 32) 78 return 0; /* bad window length */ 79 if(win == type_window) { 80 /* search window bitmap for the correct byte */ 81 /* mybyte is 0 if we need the first byte */ 82 size_t mybyte = type_low>>3; 83 if(winlen <= mybyte) 84 return 0; /* window too short */ 85 return (int)(bitmap[mybyte] & masks[type_low&0x7]); 86 } else { 87 /* not the window we are looking for */ 88 bitmap += winlen; 89 len -= winlen; 90 } 91 } 92 /* end of bitmap reached, no type found */ 93 return 0; 94} 95 96int 97nsec_has_type(struct ub_packed_rrset_key* nsec, uint16_t type) 98{ 99 struct packed_rrset_data* d = (struct packed_rrset_data*)nsec-> 100 entry.data; 101 size_t len; 102 if(!d || d->count == 0 || d->rr_len[0] < 2+1) 103 return 0; 104 len = dname_valid(d->rr_data[0]+2, d->rr_len[0]-2); 105 if(!len) 106 return 0; 107 return nsecbitmap_has_type_rdata(d->rr_data[0]+2+len, 108 d->rr_len[0]-2-len, type); 109} 110 111/** 112 * Get next owner name from nsec record 113 * @param nsec: the nsec RRset. 114 * If there are multiple RRs, then this will only return one of them. 115 * @param nm: the next name is returned. 116 * @param ln: length of nm is returned. 117 * @return false on a bad NSEC RR (too short, malformed dname). 118 */ 119static int 120nsec_get_next(struct ub_packed_rrset_key* nsec, uint8_t** nm, size_t* ln) 121{ 122 struct packed_rrset_data* d = (struct packed_rrset_data*)nsec-> 123 entry.data; 124 if(!d || d->count == 0 || d->rr_len[0] < 2+1) { 125 *nm = 0; 126 *ln = 0; 127 return 0; 128 } 129 *nm = d->rr_data[0]+2; 130 *ln = dname_valid(*nm, d->rr_len[0]-2); 131 if(!*ln) { 132 *nm = 0; 133 *ln = 0; 134 return 0; 135 } 136 return 1; 137} 138 139/** 140 * For an NSEC that matches the DS queried for, check absence of DS type. 141 * 142 * @param nsec: NSEC for proof, must be trusted. 143 * @param qinfo: what is queried for. 144 * @return if secure the nsec proves that no DS is present, or 145 * insecure if it proves it is not a delegation point. 146 * or bogus if something was wrong. 147 */ 148static enum sec_status 149val_nsec_proves_no_ds(struct ub_packed_rrset_key* nsec, 150 struct query_info* qinfo) 151{ 152 log_assert(qinfo->qtype == LDNS_RR_TYPE_DS); 153 log_assert(ntohs(nsec->rk.type) == LDNS_RR_TYPE_NSEC); 154 155 if(nsec_has_type(nsec, LDNS_RR_TYPE_SOA) && qinfo->qname_len != 1) { 156 /* SOA present means that this is the NSEC from the child, 157 * not the parent (so it is the wrong one). */ 158 return sec_status_bogus; 159 } 160 if(nsec_has_type(nsec, LDNS_RR_TYPE_DS)) { 161 /* DS present means that there should have been a positive 162 * response to the DS query, so there is something wrong. */ 163 return sec_status_bogus; 164 } 165 166 if(!nsec_has_type(nsec, LDNS_RR_TYPE_NS)) { 167 /* If there is no NS at this point at all, then this 168 * doesn't prove anything one way or the other. */ 169 return sec_status_insecure; 170 } 171 /* Otherwise, this proves no DS. */ 172 return sec_status_secure; 173} 174 175/** check security status from cache or verify rrset, returns true if secure */ 176static int 177nsec_verify_rrset(struct module_env* env, struct val_env* ve, 178 struct ub_packed_rrset_key* nsec, struct key_entry_key* kkey, 179 char** reason, struct module_qstate* qstate) 180{ 181 struct packed_rrset_data* d = (struct packed_rrset_data*) 182 nsec->entry.data; 183 if(d->security == sec_status_secure) 184 return 1; 185 rrset_check_sec_status(env->rrset_cache, nsec, *env->now); 186 if(d->security == sec_status_secure) 187 return 1; 188 d->security = val_verify_rrset_entry(env, ve, nsec, kkey, reason, 189 LDNS_SECTION_AUTHORITY, qstate); 190 if(d->security == sec_status_secure) { 191 rrset_update_sec_status(env->rrset_cache, nsec, *env->now); 192 return 1; 193 } 194 return 0; 195} 196 197enum sec_status 198val_nsec_prove_nodata_dsreply(struct module_env* env, struct val_env* ve, 199 struct query_info* qinfo, struct reply_info* rep, 200 struct key_entry_key* kkey, time_t* proof_ttl, char** reason, 201 struct module_qstate* qstate) 202{ 203 struct ub_packed_rrset_key* nsec = reply_find_rrset_section_ns( 204 rep, qinfo->qname, qinfo->qname_len, LDNS_RR_TYPE_NSEC, 205 qinfo->qclass); 206 enum sec_status sec; 207 size_t i; 208 uint8_t* wc = NULL, *ce = NULL; 209 int valid_nsec = 0; 210 struct ub_packed_rrset_key* wc_nsec = NULL; 211 212 /* If we have a NSEC at the same name, it must prove one 213 * of two things 214 * -- 215 * 1) this is a delegation point and there is no DS 216 * 2) this is not a delegation point */ 217 if(nsec) { 218 if(!nsec_verify_rrset(env, ve, nsec, kkey, reason, qstate)) { 219 verbose(VERB_ALGO, "NSEC RRset for the " 220 "referral did not verify."); 221 return sec_status_bogus; 222 } 223 sec = val_nsec_proves_no_ds(nsec, qinfo); 224 if(sec == sec_status_bogus) { 225 /* something was wrong. */ 226 *reason = "NSEC does not prove absence of DS"; 227 return sec; 228 } else if(sec == sec_status_insecure) { 229 /* this wasn't a delegation point. */ 230 return sec; 231 } else if(sec == sec_status_secure) { 232 /* this proved no DS. */ 233 *proof_ttl = ub_packed_rrset_ttl(nsec); 234 return sec; 235 } 236 /* if unchecked, fall through to next proof */ 237 } 238 239 /* Otherwise, there is no NSEC at qname. This could be an ENT. 240 * (ENT=empty non terminal). If not, this is broken. */ 241 242 /* verify NSEC rrsets in auth section */ 243 for(i=rep->an_numrrsets; i < rep->an_numrrsets+rep->ns_numrrsets; 244 i++) { 245 if(rep->rrsets[i]->rk.type != htons(LDNS_RR_TYPE_NSEC)) 246 continue; 247 if(!nsec_verify_rrset(env, ve, rep->rrsets[i], kkey, reason, 248 qstate)) { 249 verbose(VERB_ALGO, "NSEC for empty non-terminal " 250 "did not verify."); 251 return sec_status_bogus; 252 } 253 if(nsec_proves_nodata(rep->rrsets[i], qinfo, &wc)) { 254 verbose(VERB_ALGO, "NSEC for empty non-terminal " 255 "proved no DS."); 256 *proof_ttl = rrset_get_ttl(rep->rrsets[i]); 257 if(wc && dname_is_wild(rep->rrsets[i]->rk.dname)) 258 wc_nsec = rep->rrsets[i]; 259 valid_nsec = 1; 260 } 261 if(val_nsec_proves_name_error(rep->rrsets[i], qinfo->qname)) { 262 ce = nsec_closest_encloser(qinfo->qname, 263 rep->rrsets[i]); 264 } 265 } 266 if(wc && !ce) 267 valid_nsec = 0; 268 else if(wc && ce) { 269 /* ce and wc must match */ 270 if(query_dname_compare(wc, ce) != 0) 271 valid_nsec = 0; 272 else if(!wc_nsec) 273 valid_nsec = 0; 274 } 275 if(valid_nsec) { 276 if(wc) { 277 /* check if this is a delegation */ 278 *reason = "NSEC for wildcard does not prove absence of DS"; 279 return val_nsec_proves_no_ds(wc_nsec, qinfo); 280 } 281 /* valid nsec proves empty nonterminal */ 282 return sec_status_insecure; 283 } 284 285 /* NSEC proof did not conclusively point to DS or no DS */ 286 return sec_status_unchecked; 287} 288 289int nsec_proves_nodata(struct ub_packed_rrset_key* nsec, 290 struct query_info* qinfo, uint8_t** wc) 291{ 292 log_assert(wc); 293 if(query_dname_compare(nsec->rk.dname, qinfo->qname) != 0) { 294 uint8_t* nm; 295 size_t ln; 296 297 /* empty-non-terminal checking. 298 * Done before wildcard, because this is an exact match, 299 * and would prevent a wildcard from matching. */ 300 301 /* If the nsec is proving that qname is an ENT, the nsec owner 302 * will be less than qname, and the next name will be a child 303 * domain of the qname. */ 304 if(!nsec_get_next(nsec, &nm, &ln)) 305 return 0; /* bad nsec */ 306 if(dname_strict_subdomain_c(nm, qinfo->qname) && 307 dname_canonical_compare(nsec->rk.dname, 308 qinfo->qname) < 0) { 309 return 1; /* proves ENT */ 310 } 311 312 /* wildcard checking. */ 313 314 /* If this is a wildcard NSEC, make sure that a) it was 315 * possible to have generated qname from the wildcard and 316 * b) the type map does not contain qtype. Note that this 317 * does NOT prove that this wildcard was the applicable 318 * wildcard. */ 319 if(dname_is_wild(nsec->rk.dname)) { 320 /* the purported closest encloser. */ 321 uint8_t* ce = nsec->rk.dname; 322 size_t ce_len = nsec->rk.dname_len; 323 dname_remove_label(&ce, &ce_len); 324 325 /* The qname must be a strict subdomain of the 326 * closest encloser, for the wildcard to apply 327 */ 328 if(dname_strict_subdomain_c(qinfo->qname, ce)) { 329 /* here we have a matching NSEC for the qname, 330 * perform matching NSEC checks */ 331 if(nsec_has_type(nsec, LDNS_RR_TYPE_CNAME)) { 332 /* should have gotten the wildcard CNAME */ 333 return 0; 334 } 335 if(nsec_has_type(nsec, LDNS_RR_TYPE_NS) && 336 !nsec_has_type(nsec, LDNS_RR_TYPE_SOA)) { 337 /* wrong parentside (wildcard) NSEC used */ 338 return 0; 339 } 340 if(nsec_has_type(nsec, qinfo->qtype)) { 341 return 0; 342 } 343 *wc = ce; 344 return 1; 345 } 346 } else { 347 /* See if the next owner name covers a wildcard 348 * empty non-terminal. */ 349 while (dname_canonical_compare(nsec->rk.dname, nm) < 0) { 350 /* wildcard does not apply if qname below 351 * the name that exists under the '*' */ 352 if (dname_subdomain_c(qinfo->qname, nm)) 353 break; 354 /* but if it is a wildcard and qname is below 355 * it, then the wildcard applies. The wildcard 356 * is an empty nonterminal. nodata proven. */ 357 if (dname_is_wild(nm)) { 358 size_t ce_len = ln; 359 uint8_t* ce = nm; 360 dname_remove_label(&ce, &ce_len); 361 if(dname_strict_subdomain_c(qinfo->qname, ce)) { 362 *wc = ce; 363 return 1; 364 } 365 } 366 dname_remove_label(&nm, &ln); 367 } 368 } 369 370 /* Otherwise, this NSEC does not prove ENT and is not a 371 * wildcard, so it does not prove NODATA. */ 372 return 0; 373 } 374 375 /* If the qtype exists, then we should have gotten it. */ 376 if(nsec_has_type(nsec, qinfo->qtype)) { 377 return 0; 378 } 379 380 /* if the name is a CNAME node, then we should have gotten the CNAME*/ 381 if(nsec_has_type(nsec, LDNS_RR_TYPE_CNAME)) { 382 return 0; 383 } 384 385 /* If an NS set exists at this name, and NOT a SOA (so this is a 386 * zone cut, not a zone apex), then we should have gotten a 387 * referral (or we just got the wrong NSEC). 388 * The reverse of this check is used when qtype is DS, since that 389 * must use the NSEC from above the zone cut. */ 390 if(qinfo->qtype != LDNS_RR_TYPE_DS && 391 nsec_has_type(nsec, LDNS_RR_TYPE_NS) && 392 !nsec_has_type(nsec, LDNS_RR_TYPE_SOA)) { 393 return 0; 394 } else if(qinfo->qtype == LDNS_RR_TYPE_DS && 395 nsec_has_type(nsec, LDNS_RR_TYPE_SOA) && 396 !dname_is_root(qinfo->qname)) { 397 return 0; 398 } 399 400 return 1; 401} 402 403int 404val_nsec_proves_name_error(struct ub_packed_rrset_key* nsec, uint8_t* qname) 405{ 406 uint8_t* owner = nsec->rk.dname; 407 uint8_t* next; 408 size_t nlen; 409 if(!nsec_get_next(nsec, &next, &nlen)) 410 return 0; 411 412 /* If NSEC owner == qname, then this NSEC proves that qname exists. */ 413 if(query_dname_compare(qname, owner) == 0) { 414 return 0; 415 } 416 417 /* If NSEC is a parent of qname, we need to check the type map 418 * If the parent name has a DNAME or is a delegation point, then 419 * this NSEC is being misused. */ 420 if(dname_subdomain_c(qname, owner) && 421 (nsec_has_type(nsec, LDNS_RR_TYPE_DNAME) || 422 (nsec_has_type(nsec, LDNS_RR_TYPE_NS) 423 && !nsec_has_type(nsec, LDNS_RR_TYPE_SOA)) 424 )) { 425 return 0; 426 } 427 428 if(query_dname_compare(owner, next) == 0) { 429 /* this nsec is the only nsec */ 430 /* zone.name NSEC zone.name, disproves everything else */ 431 /* but only for subdomains of that zone */ 432 if(dname_strict_subdomain_c(qname, next)) 433 return 1; 434 } 435 else if(dname_canonical_compare(owner, next) > 0) { 436 /* this is the last nsec, ....(bigger) NSEC zonename(smaller) */ 437 /* the names after the last (owner) name do not exist 438 * there are no names before the zone name in the zone 439 * but the qname must be a subdomain of the zone name(next). */ 440 if(dname_canonical_compare(owner, qname) < 0 && 441 dname_strict_subdomain_c(qname, next)) 442 return 1; 443 } else { 444 /* regular NSEC, (smaller) NSEC (larger) */ 445 if(dname_canonical_compare(owner, qname) < 0 && 446 dname_canonical_compare(qname, next) < 0) { 447 return 1; 448 } 449 } 450 return 0; 451} 452 453int val_nsec_proves_insecuredelegation(struct ub_packed_rrset_key* nsec, 454 struct query_info* qinfo) 455{ 456 if(nsec_has_type(nsec, LDNS_RR_TYPE_NS) && 457 !nsec_has_type(nsec, LDNS_RR_TYPE_DS) && 458 !nsec_has_type(nsec, LDNS_RR_TYPE_SOA)) { 459 /* see if nsec signals an insecure delegation */ 460 if(qinfo->qtype == LDNS_RR_TYPE_DS) { 461 /* if type is DS and qname is equal to nsec, then it 462 * is an exact match nsec, result not insecure */ 463 if(dname_strict_subdomain_c(qinfo->qname, 464 nsec->rk.dname)) 465 return 1; 466 } else { 467 if(dname_subdomain_c(qinfo->qname, nsec->rk.dname)) 468 return 1; 469 } 470 } 471 return 0; 472} 473 474uint8_t* 475nsec_closest_encloser(uint8_t* qname, struct ub_packed_rrset_key* nsec) 476{ 477 uint8_t* next; 478 size_t nlen; 479 uint8_t* common1, *common2; 480 if(!nsec_get_next(nsec, &next, &nlen)) 481 return NULL; 482 /* longest common with owner or next name */ 483 common1 = dname_get_shared_topdomain(nsec->rk.dname, qname); 484 common2 = dname_get_shared_topdomain(next, qname); 485 if(dname_count_labels(common1) > dname_count_labels(common2)) 486 return common1; 487 return common2; 488} 489 490int val_nsec_proves_positive_wildcard(struct ub_packed_rrset_key* nsec, 491 struct query_info* qinf, uint8_t* wc) 492{ 493 uint8_t* ce; 494 /* 1) prove that qname doesn't exist and 495 * 2) that the correct wildcard was used 496 * nsec has been verified already. */ 497 if(!val_nsec_proves_name_error(nsec, qinf->qname)) 498 return 0; 499 /* check wildcard name */ 500 ce = nsec_closest_encloser(qinf->qname, nsec); 501 if(!ce) 502 return 0; 503 if(query_dname_compare(wc, ce) != 0) { 504 return 0; 505 } 506 return 1; 507} 508 509int 510val_nsec_proves_no_wc(struct ub_packed_rrset_key* nsec, uint8_t* qname, 511 size_t qnamelen) 512{ 513 /* Determine if a NSEC record proves the non-existence of a 514 * wildcard that could have produced qname. */ 515 int labs; 516 uint8_t* ce = nsec_closest_encloser(qname, nsec); 517 uint8_t* strip; 518 size_t striplen; 519 uint8_t buf[LDNS_MAX_DOMAINLEN+3]; 520 if(!ce) 521 return 0; 522 /* we can subtract the closest encloser count - since that is the 523 * largest shared topdomain with owner and next NSEC name, 524 * because the NSEC is no proof for names shorter than the owner 525 * and next names. */ 526 labs = dname_count_labels(qname) - dname_count_labels(ce); 527 528 if(labs > 0) { 529 /* i is number of labels to strip off qname, prepend * wild */ 530 strip = qname; 531 striplen = qnamelen; 532 dname_remove_labels(&strip, &striplen, labs); 533 if(striplen > LDNS_MAX_DOMAINLEN-2) 534 return 0; /* too long to prepend wildcard */ 535 buf[0] = 1; 536 buf[1] = (uint8_t)'*'; 537 memmove(buf+2, strip, striplen); 538 if(val_nsec_proves_name_error(nsec, buf)) { 539 return 1; 540 } 541 } 542 return 0; 543} 544