| 1 | /* |
| 2 | * reply.c |
| 3 | * - main handling and parsing routine for received datagrams |
| 4 | */ |
| 5 | /* |
| 6 | * This file is part of adns, which is |
| 7 | * Copyright (C) 1997-2000,2003,2006,2014 Ian Jackson |
| 8 | * Copyright (C) 1999-2000,2003,2006 Tony Finch |
| 9 | * Copyright (C) 1991 Massachusetts Institute of Technology |
| 10 | * (See the file INSTALL for full details.) |
| 11 | * |
| 12 | * This program is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 3, or (at your option) |
| 15 | * any later version. |
| 16 | * |
| 17 | * This program is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with this program; if not, write to the Free Software Foundation. |
| 24 | */ |
| 25 | |
| 26 | #include <stdlib.h> |
| 27 | |
| 28 | #include "internal.h" |
| 29 | |
| 30 | void adns__procdgram(adns_state ads, const byte *dgram, int dglen, |
| 31 | int serv, int viatcp, struct timeval now) { |
| 32 | int cbyte, rrstart, wantedrrs, rri, foundsoa, foundns, cname_here; |
| 33 | int id, f1, f2, qdcount, ancount, nscount, arcount; |
| 34 | int flg_ra, flg_rd, flg_tc, flg_qr, opcode; |
| 35 | int rrtype, rrclass, rdlength, rdstart; |
| 36 | int anstart, nsstart; |
| 37 | int ownermatched, l, nrrs; |
| 38 | unsigned long ttl, soattl; |
| 39 | const typeinfo *typei; |
| 40 | adns_query qu, nqu; |
| 41 | dns_rcode rcode; |
| 42 | adns_status st; |
| 43 | vbuf tempvb; |
| 44 | byte *newquery, *rrsdata; |
| 45 | parseinfo pai; |
| 46 | |
| 47 | if (dglen<DNS_HDRSIZE) { |
| 48 | adns__diag(ads,serv,0,"received datagram" |
| 49 | " too short for message header (%d)",dglen); |
| 50 | return; |
| 51 | } |
| 52 | cbyte= 0; |
| 53 | GET_W(cbyte,id); |
| 54 | GET_B(cbyte,f1); |
| 55 | GET_B(cbyte,f2); |
| 56 | GET_W(cbyte,qdcount); |
| 57 | GET_W(cbyte,ancount); |
| 58 | GET_W(cbyte,nscount); |
| 59 | GET_W(cbyte,arcount); |
| 60 | assert(cbyte == DNS_HDRSIZE); |
| 61 | |
| 62 | flg_qr= f1&0x80; |
| 63 | opcode= (f1&0x78)>>3; |
| 64 | flg_tc= f1&0x02; |
| 65 | flg_rd= f1&0x01; |
| 66 | flg_ra= f2&0x80; |
| 67 | rcode= (f2&0x0f); |
| 68 | |
| 69 | cname_here= 0; |
| 70 | |
| 71 | if (!flg_qr) { |
| 72 | adns__diag(ads,serv,0,"server sent us a query, not a response"); |
| 73 | return; |
| 74 | } |
| 75 | if (opcode) { |
| 76 | adns__diag(ads,serv,0,"server sent us unknown opcode" |
| 77 | " %d (wanted 0=QUERY)",opcode); |
| 78 | return; |
| 79 | } |
| 80 | |
| 81 | qu= 0; |
| 82 | /* See if we can find the relevant query, or leave qu=0 otherwise ... */ |
| 83 | |
| 84 | if (qdcount == 1) { |
| 85 | for (qu= viatcp ? ads->tcpw.head : ads->udpw.head; qu; qu= nqu) { |
| 86 | nqu= qu->next; |
| 87 | if (qu->id != id) continue; |
| 88 | if (dglen < qu->query_dglen) continue; |
| 89 | if (memcmp(qu->query_dgram+DNS_HDRSIZE, |
| 90 | dgram+DNS_HDRSIZE, |
| 91 | qu->query_dglen-DNS_HDRSIZE)) |
| 92 | continue; |
| 93 | if (viatcp) { |
| 94 | assert(qu->state == query_tcpw); |
| 95 | } else { |
| 96 | assert(qu->state == query_tosend); |
| 97 | if (!(qu->udpsent & (1<<serv))) continue; |
| 98 | } |
| 99 | break; |
| 100 | } |
| 101 | if (qu) { |
| 102 | /* We're definitely going to do something with this query now */ |
| 103 | if (viatcp) LIST_UNLINK(ads->tcpw,qu); |
| 104 | else LIST_UNLINK(ads->udpw,qu); |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | /* If we're going to ignore the packet, we return as soon as we have |
| 109 | * failed the query (if any) and printed the warning message (if |
| 110 | * any). |
| 111 | */ |
| 112 | switch (rcode) { |
| 113 | case rcode_noerror: |
| 114 | case rcode_nxdomain: |
| 115 | break; |
| 116 | case rcode_formaterror: |
| 117 | adns__warn(ads,serv,qu,"server cannot understand our query" |
| 118 | " (Format Error)"); |
| 119 | if (qu) adns__query_fail(qu,adns_s_rcodeformaterror); |
| 120 | return; |
| 121 | case rcode_servfail: |
| 122 | if (qu) adns__query_fail(qu,adns_s_rcodeservfail); |
| 123 | else adns__debug(ads,serv,qu,"server failure on unidentifiable query"); |
| 124 | return; |
| 125 | case rcode_notimp: |
| 126 | adns__warn(ads,serv,qu,"server claims not to implement our query"); |
| 127 | if (qu) adns__query_fail(qu,adns_s_rcodenotimplemented); |
| 128 | return; |
| 129 | case rcode_refused: |
| 130 | adns__debug(ads,serv,qu,"server refused our query"); |
| 131 | if (qu) adns__query_fail(qu,adns_s_rcoderefused); |
| 132 | return; |
| 133 | default: |
| 134 | adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode); |
| 135 | if (qu) adns__query_fail(qu,adns_s_rcodeunknown); |
| 136 | return; |
| 137 | } |
| 138 | |
| 139 | if (!qu) { |
| 140 | if (!qdcount) { |
| 141 | adns__diag(ads,serv,0,"server sent reply without quoting our question"); |
| 142 | } else if (qdcount>1) { |
| 143 | adns__diag(ads,serv,0,"server claimed to answer %d" |
| 144 | " questions with one message", qdcount); |
| 145 | } else if (ads->iflags & adns_if_debug) { |
| 146 | adns__vbuf_init(&tempvb); |
| 147 | adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s", |
| 148 | id, adns__diag_domain(ads,serv,0,&tempvb, |
| 149 | dgram,dglen,DNS_HDRSIZE)); |
| 150 | adns__vbuf_free(&tempvb); |
| 151 | } |
| 152 | return; |
| 153 | } |
| 154 | |
| 155 | /* We're definitely going to do something with this packet and this |
| 156 | * query now. */ |
| 157 | |
| 158 | anstart= qu->query_dglen; |
| 159 | |
| 160 | /* Now, take a look at the answer section, and see if it is complete. |
| 161 | * If it has any CNAMEs we stuff them in the answer. |
| 162 | */ |
| 163 | wantedrrs= 0; |
| 164 | cbyte= anstart; |
| 165 | for (rri= 0; rri<ancount; rri++) { |
| 166 | rrstart= cbyte; |
| 167 | st= adns__findrr(qu,serv, dgram,dglen,&cbyte, |
| 168 | &rrtype,&rrclass,&ttl, &rdlength,&rdstart, |
| 169 | &ownermatched); |
| 170 | if (st) { adns__query_fail(qu,st); return; } |
| 171 | if (rrtype == -1) goto x_truncated; |
| 172 | |
| 173 | if (rrclass != DNS_CLASS_IN) { |
| 174 | adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d" |
| 175 | " (expected IN=%d)", rrclass,DNS_CLASS_IN); |
| 176 | continue; |
| 177 | } |
| 178 | if (!ownermatched) { |
| 179 | if (ads->iflags & adns_if_debug) { |
| 180 | adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s", |
| 181 | adns__diag_domain(ads,serv,qu, &qu->vb, |
| 182 | dgram,dglen,rrstart)); |
| 183 | } |
| 184 | continue; |
| 185 | } |
| 186 | if (rrtype == adns_r_cname && |
| 187 | (qu->answer->type & adns_rrt_typemask) != adns_r_cname) { |
| 188 | if (qu->flags & adns_qf_cname_forbid) { |
| 189 | adns__query_fail(qu,adns_s_prohibitedcname); |
| 190 | return; |
| 191 | } else if (qu->cname_dgram) { /* Ignore second and subsequent CNAME(s) */ |
| 192 | adns__debug(ads,serv,qu,"allegedly canonical name %s" |
| 193 | " is actually alias for %s", qu->answer->cname, |
| 194 | adns__diag_domain(ads,serv,qu, &qu->vb, |
| 195 | dgram,dglen,rdstart)); |
| 196 | adns__query_fail(qu,adns_s_prohibitedcname); |
| 197 | return; |
| 198 | } else if (wantedrrs) { /* Ignore CNAME(s) after RR(s). */ |
| 199 | adns__debug(ads,serv,qu,"ignoring CNAME (to %s) coexisting with RR", |
| 200 | adns__diag_domain(ads,serv,qu, &qu->vb, |
| 201 | dgram,dglen,rdstart)); |
| 202 | } else { |
| 203 | qu->cname_begin= rdstart; |
| 204 | qu->cname_dglen= dglen; |
| 205 | st= adns__parse_domain(ads,serv,qu, &qu->vb, |
| 206 | qu->flags & adns_qf_quotefail_cname |
| 207 | ? 0 : pdf_quoteok, |
| 208 | dgram,dglen, &rdstart,rdstart+rdlength); |
| 209 | if (!qu->vb.used) goto x_truncated; |
| 210 | if (st) { adns__query_fail(qu,st); return; } |
| 211 | l= strlen(qu->vb.buf)+1; |
| 212 | qu->answer->cname= adns__alloc_preserved(qu,l); |
| 213 | if (!qu->answer->cname) { |
| 214 | adns__query_fail(qu,adns_s_nomemory); |
| 215 | return; |
| 216 | } |
| 217 | |
| 218 | qu->cname_dgram= adns__alloc_mine(qu,dglen); |
| 219 | memcpy(qu->cname_dgram,dgram,dglen); |
| 220 | |
| 221 | memcpy(qu->answer->cname,qu->vb.buf,l); |
| 222 | cname_here= 1; |
| 223 | adns__update_expires(qu,ttl,now); |
| 224 | /* If we find the answer section truncated after this point we restart |
| 225 | * the query at the CNAME; if beforehand then we obviously have to use |
| 226 | * TCP. If there is no truncation we can use the whole answer if |
| 227 | * it contains the relevant info. |
| 228 | */ |
| 229 | } |
| 230 | } else if (rrtype == (qu->answer->type & adns_rrt_typemask)) { |
| 231 | wantedrrs++; |
| 232 | } else { |
| 233 | adns__debug(ads,serv,qu,"ignoring answer RR" |
| 234 | " with irrelevant type %d",rrtype); |
| 235 | } |
| 236 | } |
| 237 | |
| 238 | /* We defer handling truncated responses here, in case there was a CNAME |
| 239 | * which we could use. |
| 240 | */ |
| 241 | if (flg_tc) goto x_truncated; |
| 242 | |
| 243 | nsstart= cbyte; |
| 244 | |
| 245 | if (!wantedrrs) { |
| 246 | /* Oops, NODATA or NXDOMAIN or perhaps a referral |
| 247 | * (which would be a problem) */ |
| 248 | |
| 249 | /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records |
| 250 | * in authority section */ |
| 251 | foundsoa= 0; soattl= 0; foundns= 0; |
| 252 | for (rri= 0; rri<nscount; rri++) { |
| 253 | rrstart= cbyte; |
| 254 | st= adns__findrr(qu,serv, dgram,dglen,&cbyte, |
| 255 | &rrtype,&rrclass,&ttl, &rdlength,&rdstart, 0); |
| 256 | if (st) { adns__query_fail(qu,st); return; } |
| 257 | if (rrtype==-1) goto x_truncated; |
| 258 | if (rrclass != DNS_CLASS_IN) { |
| 259 | adns__diag(ads,serv,qu, |
| 260 | "ignoring authority RR with wrong class %d" |
| 261 | " (expected IN=%d)", rrclass,DNS_CLASS_IN); |
| 262 | continue; |
| 263 | } |
| 264 | if (rrtype == adns_r_soa_raw) { foundsoa= 1; soattl= ttl; break; } |
| 265 | else if (rrtype == adns_r_ns_raw) { foundns= 1; } |
| 266 | } |
| 267 | |
| 268 | if (rcode == rcode_nxdomain) { |
| 269 | /* We still wanted to look for the SOA so we could find the TTL. */ |
| 270 | adns__update_expires(qu,soattl,now); |
| 271 | |
| 272 | if (qu->flags & adns_qf_search && !qu->cname_dgram) { |
| 273 | adns__search_next(ads,qu,now); |
| 274 | } else { |
| 275 | adns__query_fail(qu,adns_s_nxdomain); |
| 276 | } |
| 277 | return; |
| 278 | } |
| 279 | |
| 280 | if (foundsoa || !foundns) { |
| 281 | /* Aha ! A NODATA response, good. */ |
| 282 | adns__update_expires(qu,soattl,now); |
| 283 | adns__query_fail(qu,adns_s_nodata); |
| 284 | return; |
| 285 | } |
| 286 | |
| 287 | /* Now what ? No relevant answers, no SOA, and at least some NS's. |
| 288 | * Looks like a referral. Just one last chance ... if we came across |
| 289 | * a CNAME in this datagram then we should probably do our own CNAME |
| 290 | * lookup now in the hope that we won't get a referral again. |
| 291 | */ |
| 292 | if (cname_here) goto x_restartquery; |
| 293 | |
| 294 | /* Bloody hell, I thought we asked for recursion ? */ |
| 295 | if (!flg_ra) { |
| 296 | adns__diag(ads,serv,qu,"server is not willing" |
| 297 | " to do recursive lookups for us"); |
| 298 | adns__query_fail(qu,adns_s_norecurse); |
| 299 | } else { |
| 300 | if (!flg_rd) |
| 301 | adns__diag(ads,serv,qu,"server thinks" |
| 302 | " we didn't ask for recursive lookup"); |
| 303 | else |
| 304 | adns__debug(ads,serv,qu,"server claims to do recursion," |
| 305 | " but gave us a referral"); |
| 306 | adns__query_fail(qu,adns_s_invalidresponse); |
| 307 | } |
| 308 | return; |
| 309 | } |
| 310 | |
| 311 | /* Now, we have some RRs which we wanted. */ |
| 312 | |
| 313 | qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->answer->rrsz*wantedrrs); |
| 314 | if (!qu->answer->rrs.untyped) { |
| 315 | adns__query_fail(qu,adns_s_nomemory); |
| 316 | return; |
| 317 | } |
| 318 | |
| 319 | typei= qu->typei; |
| 320 | cbyte= anstart; |
| 321 | rrsdata= qu->answer->rrs.bytes; |
| 322 | |
| 323 | pai.ads= qu->ads; |
| 324 | pai.qu= qu; |
| 325 | pai.serv= serv; |
| 326 | pai.dgram= dgram; |
| 327 | pai.dglen= dglen; |
| 328 | pai.nsstart= nsstart; |
| 329 | pai.nscount= nscount; |
| 330 | pai.arcount= arcount; |
| 331 | pai.now= now; |
| 332 | |
| 333 | for (rri=0, nrrs=0; rri<ancount; rri++) { |
| 334 | st= adns__findrr(qu,serv, dgram,dglen,&cbyte, |
| 335 | &rrtype,&rrclass,&ttl, &rdlength,&rdstart, |
| 336 | &ownermatched); |
| 337 | assert(!st); assert(rrtype != -1); |
| 338 | if (rrclass != DNS_CLASS_IN || |
| 339 | rrtype != (qu->answer->type & adns_rrt_typemask) || |
| 340 | !ownermatched) |
| 341 | continue; |
| 342 | adns__update_expires(qu,ttl,now); |
| 343 | st= typei->parse(&pai, rdstart,rdstart+rdlength, |
| 344 | rrsdata+nrrs*qu->answer->rrsz); |
| 345 | if (st) { adns__query_fail(qu,st); return; } |
| 346 | if (rdstart==-1) goto x_truncated; |
| 347 | nrrs++; |
| 348 | } |
| 349 | assert(nrrs==wantedrrs); |
| 350 | qu->answer->nrrs= nrrs; |
| 351 | |
| 352 | /* This may have generated some child queries ... */ |
| 353 | if (qu->children.head) { |
| 354 | qu->state= query_childw; |
| 355 | LIST_LINK_TAIL(ads->childw,qu); |
| 356 | return; |
| 357 | } |
| 358 | adns__query_done(qu); |
| 359 | return; |
| 360 | |
| 361 | x_truncated: |
| 362 | |
| 363 | if (!flg_tc) { |
| 364 | adns__diag(ads,serv,qu,"server sent datagram which points outside itself"); |
| 365 | adns__query_fail(qu,adns_s_invalidresponse); |
| 366 | return; |
| 367 | } |
| 368 | qu->flags |= adns_qf_usevc; |
| 369 | |
| 370 | x_restartquery: |
| 371 | if (qu->cname_dgram) { |
| 372 | st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id, |
| 373 | qu->cname_dgram,qu->cname_dglen,qu->cname_begin, |
| 374 | qu->answer->type, qu->flags); |
| 375 | if (st) { adns__query_fail(qu,st); return; } |
| 376 | |
| 377 | newquery= realloc(qu->query_dgram,qu->vb.used); |
| 378 | if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; } |
| 379 | |
| 380 | qu->query_dgram= newquery; |
| 381 | qu->query_dglen= qu->vb.used; |
| 382 | memcpy(newquery,qu->vb.buf,qu->vb.used); |
| 383 | } |
| 384 | |
| 385 | if (qu->state == query_tcpw) qu->state= query_tosend; |
| 386 | qu->retries= 0; |
| 387 | adns__reset_preserved(qu); |
| 388 | adns__query_send(qu,now); |
| 389 | } |