mdw@git.distorted.org.uk Git - adns/blob - src/reply.c

   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) 2014  Mark Wooding
   9  *    Copyright (C) 1999-2000,2003,2006  Tony Finch
  10  *    Copyright (C) 1991 Massachusetts Institute of Technology
  11  *  (See the file INSTALL for full details.)
  12  *
  13  *  This program is free software; you can redistribute it and/or modify
  14  *  it under the terms of the GNU General Public License as published by
  15  *  the Free Software Foundation; either version 3, or (at your option)
  16  *  any later version.
  17  *
  18  *  This program is distributed in the hope that it will be useful,
  19  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *  GNU General Public License for more details.
  22  *
  23  *  You should have received a copy of the GNU General Public License
  24  *  along with this program; if not, write to the Free Software Foundation.
  25  */
  26
  27 #include <stdlib.h>
  28
  29 #include "internal.h"
  30
  31 void adns__procdgram(adns_state ads, const byte *dgram, int dglen,
  32                      int serv, int viatcp, struct timeval now) {
  33   int cbyte, rrstart, wantedrrs, rri, foundsoa, foundns, cname_here;
  34   int id, f1, f2, qdcount, ancount, nscount, arcount;
  35   int flg_ra, flg_rd, flg_tc, flg_qr, opcode;
  36   int rrtype, rrclass, rdlength, rdstart;
  37   int anstart, nsstart;
  38   int ownermatched, l, nrrs;
  39   unsigned long ttl, soattl;
  40   const typeinfo *typei;
  41   adns_query qu, nqu;
  42   dns_rcode rcode;
  43   adns_status st;
  44   vbuf tempvb;
  45   byte *newquery, *rrsdata;
  46   parseinfo pai;
  47
  48   if (dglen<DNS_HDRSIZE) {
  49     adns__diag(ads,serv,0,"received datagram"
  50                " too short for message header (%d)",dglen);
  51     return;
  52   }
  53   cbyte= 0;
  54   GET_W(cbyte,id);
  55   GET_B(cbyte,f1);
  56   GET_B(cbyte,f2);
  57   GET_W(cbyte,qdcount);
  58   GET_W(cbyte,ancount);
  59   GET_W(cbyte,nscount);
  60   GET_W(cbyte,arcount);
  61   assert(cbyte == DNS_HDRSIZE);
  62
  63   flg_qr= f1&0x80;
  64   opcode= (f1&0x78)>>3;
  65   flg_tc= f1&0x02;
  66   flg_rd= f1&0x01;
  67   flg_ra= f2&0x80;
  68   rcode= (f2&0x0f);
  69
  70   cname_here= 0;
  71
  72   if (!flg_qr) {
  73     adns__diag(ads,serv,0,"server sent us a query, not a response");
  74     return;
  75   }
  76   if (opcode) {
  77     adns__diag(ads,serv,0,"server sent us unknown opcode"
  78                " %d (wanted 0=QUERY)",opcode);
  79     return;
  80   }
  81
  82   qu= 0;
  83   /* See if we can find the relevant query, or leave qu=0 otherwise ... */
  84
  85   if (qdcount == 1) {
  86     for (qu= viatcp ? ads->tcpw.head : ads->udpw.head; qu; qu= nqu) {
  87       nqu= qu->next;
  88       if (qu->id != id) continue;
  89       if (dglen < qu->query_dglen) continue;
  90       if (memcmp(qu->query_dgram+DNS_HDRSIZE,
  91                  dgram+DNS_HDRSIZE,
  92                  qu->query_dglen-DNS_HDRSIZE))
  93         continue;
  94       if (viatcp) {
  95         assert(qu->state == query_tcpw);
  96       } else {
  97         assert(qu->state == query_tosend);
  98         if (!(qu->udpsent & (1<<serv))) continue;
  99       }
 100       break;
 101     }
 102     if (qu) {
 103       /* We're definitely going to do something with this query now */
 104       if (viatcp) LIST_UNLINK(ads->tcpw,qu);
 105       else LIST_UNLINK(ads->udpw,qu);
 106     }
 107   }
 108
 109   /* If we're going to ignore the packet, we return as soon as we have
 110    * failed the query (if any) and printed the warning message (if
 111    * any).
 112    */
 113   switch (rcode) {
 114   case rcode_noerror:
 115   case rcode_nxdomain:
 116     break;
 117   case rcode_formaterror:
 118     adns__warn(ads,serv,qu,"server cannot understand our query"
 119                " (Format Error)");
 120     if (qu) adns__query_fail(qu,adns_s_rcodeformaterror);
 121     return;
 122   case rcode_servfail:
 123     if (qu) adns__query_fail(qu,adns_s_rcodeservfail);
 124     else adns__debug(ads,serv,qu,"server failure on unidentifiable query");
 125     return;
 126   case rcode_notimp:
 127     adns__warn(ads,serv,qu,"server claims not to implement our query");
 128     if (qu) adns__query_fail(qu,adns_s_rcodenotimplemented);
 129     return;
 130   case rcode_refused:
 131     adns__debug(ads,serv,qu,"server refused our query");
 132     if (qu) adns__query_fail(qu,adns_s_rcoderefused);
 133     return;
 134   default:
 135     adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode);
 136     if (qu) adns__query_fail(qu,adns_s_rcodeunknown);
 137     return;
 138   }
 139
 140   if (!qu) {
 141     if (!qdcount) {
 142       adns__diag(ads,serv,0,"server sent reply without quoting our question");
 143     } else if (qdcount>1) {
 144       adns__diag(ads,serv,0,"server claimed to answer %d"
 145                  " questions with one message", qdcount);
 146     } else if (ads->iflags & adns_if_debug) {
 147       adns__vbuf_init(&tempvb);
 148       adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
 149                   id, adns__diag_domain(ads,serv,0,&tempvb,
 150                                         dgram,dglen,DNS_HDRSIZE));
 151       adns__vbuf_free(&tempvb);
 152     }
 153     return;
 154   }
 155
 156   /* We're definitely going to do something with this packet and this
 157    * query now. */
 158
 159   anstart= qu->query_dglen;
 160
 161   /* Now, take a look at the answer section, and see if it is complete.
 162    * If it has any CNAMEs we stuff them in the answer.
 163    */
 164   wantedrrs= 0;
 165   cbyte= anstart;
 166   for (rri= 0; rri<ancount; rri++) {
 167     rrstart= cbyte;
 168     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 169                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 170                      &ownermatched);
 171     if (st) { adns__query_fail(qu,st); return; }
 172     if (rrtype == -1) goto x_truncated;
 173
 174     if (rrclass != DNS_CLASS_IN) {
 175       adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d"
 176                  " (expected IN=%d)", rrclass,DNS_CLASS_IN);
 177       continue;
 178     }
 179     if (!ownermatched) {
 180       if (ads->iflags & adns_if_debug) {
 181         adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
 182                     adns__diag_domain(ads,serv,qu, &qu->vb,
 183                                       dgram,dglen,rrstart));
 184       }
 185       continue;
 186     }
 187     if (rrtype == adns_r_cname &&
 188         (qu->answer->type & adns_rrt_typemask) != adns_r_cname) {
 189       if (qu->flags & adns_qf_cname_forbid) {
 190         adns__query_fail(qu,adns_s_prohibitedcname);
 191         return;
 192       } else if (qu->cname_dgram) { /* Ignore second and subsequent CNAME(s) */
 193         adns__debug(ads,serv,qu,"allegedly canonical name %s"
 194                     " is actually alias for %s", qu->answer->cname,
 195                     adns__diag_domain(ads,serv,qu, &qu->vb,
 196                                       dgram,dglen,rdstart));
 197         adns__query_fail(qu,adns_s_prohibitedcname);
 198         return;
 199       } else if (wantedrrs) { /* Ignore CNAME(s) after RR(s). */
 200         adns__debug(ads,serv,qu,"ignoring CNAME (to %s) coexisting with RR",
 201                     adns__diag_domain(ads,serv,qu, &qu->vb,
 202                                       dgram,dglen,rdstart));
 203       } else {
 204         qu->cname_begin= rdstart;
 205         qu->cname_dglen= dglen;
 206         st= adns__parse_domain(ads,serv,qu, &qu->vb,
 207                                qu->flags & adns_qf_quotefail_cname
 208                                ? 0 : pdf_quoteok,
 209                                dgram,dglen, &rdstart,rdstart+rdlength);
 210         if (!qu->vb.used) goto x_truncated;
 211         if (st) { adns__query_fail(qu,st); return; }
 212         l= strlen(qu->vb.buf)+1;
 213         qu->answer->cname= adns__alloc_preserved(qu,l);
 214         if (!qu->answer->cname) {
 215           adns__query_fail(qu,adns_s_nomemory);
 216           return;
 217         }
 218
 219         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 220         memcpy(qu->cname_dgram,dgram,dglen);
 221
 222         memcpy(qu->answer->cname,qu->vb.buf,l);
 223         cname_here= 1;
 224         adns__update_expires(qu,ttl,now);
 225         /* If we find the answer section truncated after this point we restart
 226          * the query at the CNAME; if beforehand then we obviously have to use
 227          * TCP.  If there is no truncation we can use the whole answer if
 228          * it contains the relevant info.
 229          */
 230       }
 231     } else if (rrtype == (qu->answer->type & adns_rrt_typemask)) {
 232       wantedrrs++;
 233     } else {
 234       adns__debug(ads,serv,qu,"ignoring answer RR"
 235                   " with irrelevant type %d",rrtype);
 236     }
 237   }
 238
 239   /* We defer handling truncated responses here, in case there was a CNAME
 240    * which we could use.
 241    */
 242   if (flg_tc) goto x_truncated;
 243
 244   nsstart= cbyte;
 245
 246   if (!wantedrrs) {
 247     /* Oops, NODATA or NXDOMAIN or perhaps a referral
 248      * (which would be a problem) */
 249
 250     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records
 251      * in authority section */
 252     foundsoa= 0; soattl= 0; foundns= 0;
 253     for (rri= 0; rri<nscount; rri++) {
 254       rrstart= cbyte;
 255       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 256                        &rrtype,&rrclass,&ttl, &rdlength,&rdstart, 0);
 257       if (st) { adns__query_fail(qu,st); return; }
 258       if (rrtype==-1) goto x_truncated;
 259       if (rrclass != DNS_CLASS_IN) {
 260         adns__diag(ads,serv,qu,
 261                    "ignoring authority RR with wrong class %d"
 262                    " (expected IN=%d)", rrclass,DNS_CLASS_IN);
 263         continue;
 264       }
 265       if (rrtype == adns_r_soa_raw) { foundsoa= 1; soattl= ttl; break; }
 266       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 267     }
 268
 269     if (rcode == rcode_nxdomain) {
 270       /* We still wanted to look for the SOA so we could find the TTL. */
 271       adns__update_expires(qu,soattl,now);
 272
 273       if (qu->flags & adns_qf_search && !qu->cname_dgram) {
 274         adns__search_next(ads,qu,now);
 275       } else {
 276         adns__query_fail(qu,adns_s_nxdomain);
 277       }
 278       return;
 279     }
 280
 281     if (foundsoa || !foundns) {
 282       /* Aha !  A NODATA response, good. */
 283       adns__update_expires(qu,soattl,now);
 284       adns__query_fail(qu,adns_s_nodata);
 285       return;
 286     }
 287
 288     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 289      * Looks like a referral.  Just one last chance ... if we came across
 290      * a CNAME in this datagram then we should probably do our own CNAME
 291      * lookup now in the hope that we won't get a referral again.
 292      */
 293     if (cname_here) goto x_restartquery;
 294
 295     /* Bloody hell, I thought we asked for recursion ? */
 296     if (!flg_ra) {
 297       adns__diag(ads,serv,qu,"server is not willing"
 298                  " to do recursive lookups for us");
 299       adns__query_fail(qu,adns_s_norecurse);
 300     } else {
 301       if (!flg_rd)
 302         adns__diag(ads,serv,qu,"server thinks"
 303                    " we didn't ask for recursive lookup");
 304       else
 305         adns__debug(ads,serv,qu,"server claims to do recursion,"
 306                     " but gave us a referral");
 307       adns__query_fail(qu,adns_s_invalidresponse);
 308     }
 309     return;
 310   }
 311
 312   /* Now, we have some RRs which we wanted. */
 313
 314   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->answer->rrsz*wantedrrs);
 315   if (!qu->answer->rrs.untyped) {
 316     adns__query_fail(qu,adns_s_nomemory);
 317     return;
 318   }
 319
 320   typei= qu->typei;
 321   cbyte= anstart;
 322   rrsdata= qu->answer->rrs.bytes;
 323
 324   pai.ads= qu->ads;
 325   pai.qu= qu;
 326   pai.serv= serv;
 327   pai.dgram= dgram;
 328   pai.dglen= dglen;
 329   pai.nsstart= nsstart;
 330   pai.nscount= nscount;
 331   pai.arcount= arcount;
 332   pai.now= now;
 333
 334   for (rri=0, nrrs=0; rri<ancount; rri++) {
 335     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 336                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 337                      &ownermatched);
 338     assert(!st); assert(rrtype != -1);
 339     if (rrclass != DNS_CLASS_IN ||
 340         rrtype != (qu->answer->type & adns_rrt_typemask) ||
 341         !ownermatched)
 342       continue;
 343     adns__update_expires(qu,ttl,now);
 344     st= typei->parse(&pai, rdstart,rdstart+rdlength,
 345                      rrsdata+nrrs*qu->answer->rrsz);
 346     if (st) { adns__query_fail(qu,st); return; }
 347     if (rdstart==-1) goto x_truncated;
 348     nrrs++;
 349   }
 350   assert(nrrs==wantedrrs);
 351   qu->answer->nrrs= nrrs;
 352
 353   /* This may have generated some child queries ... */
 354   if (qu->children.head) {
 355     qu->state= query_childw;
 356     LIST_LINK_TAIL(ads->childw,qu);
 357     return;
 358   }
 359   adns__query_done(qu);
 360   return;
 361
 362  x_truncated:
 363
 364   if (!flg_tc) {
 365     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 366     adns__query_fail(qu,adns_s_invalidresponse);
 367     return;
 368   }
 369   qu->flags |= adns_qf_usevc;
 370
 371  x_restartquery:
 372   if (qu->cname_dgram) {
 373     st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
 374                               qu->cname_dgram,qu->cname_dglen,qu->cname_begin,
 375                               qu->answer->type, qu->flags);
 376     if (st) { adns__query_fail(qu,st); return; }
 377
 378     newquery= realloc(qu->query_dgram,qu->vb.used);
 379     if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; }
 380
 381     qu->query_dgram= newquery;
 382     qu->query_dglen= qu->vb.used;
 383     memcpy(newquery,qu->vb.buf,qu->vb.used);
 384   }
 385
 386   if (qu->state == query_tcpw) qu->state= query_tosend;
 387   qu->retries= 0;
 388   adns__reset_preserved(qu);
 389   adns__query_send(qu,now);
 390 }