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
   7  *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
   8  *
   9  *  It is part of adns, which is
  10  *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
  11  *    Copyright (C) 1999 Tony Finch <dot@dotat.at>
  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 2, 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  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26  */
  27
  28 #include <stdlib.h>
  29
  30 #include "internal.h"
  31
  32 void adns__procdgram(adns_state ads, const byte *dgram, int dglen,
  33                      int serv, int viatcp, struct timeval now) {
  34   int cbyte, rrstart, wantedrrs, rri, foundsoa, foundns, cname_here;
  35   int id, f1, f2, qdcount, ancount, nscount, arcount;
  36   int flg_ra, flg_rd, flg_tc, flg_qr, opcode;
  37   int rrtype, rrclass, rdlength, rdstart;
  38   int anstart, nsstart, arstart;
  39   int ownermatched, l, nrrs;
  40   unsigned long ttl, soattl;
  41   const typeinfo *typei;
  42   adns_query qu, nqu;
  43   dns_rcode rcode;
  44   adns_status st;
  45   vbuf tempvb;
  46   byte *newquery, *rrsdata;
  47   parseinfo pai;
  48
  49   if (dglen<DNS_HDRSIZE) {
  50     adns__diag(ads,serv,0,"received datagram 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 %d (wanted 0=QUERY)",opcode);
  78     return;
  79   }
  80   if (!qdcount) {
  81     adns__diag(ads,serv,0,"server sent reply without quoting our question");
  82     return;
  83   } else if (qdcount>1) {
  84     adns__diag(ads,serv,0,"server claimed to answer %d questions with one message",
  85                qdcount);
  86     return;
  87   }
  88   for (qu= ads->timew.head; qu; qu= nqu) {
  89     nqu= qu->next;
  90     if (qu->id != id) continue;
  91     if (dglen < qu->query_dglen) continue;
  92     if (memcmp(qu->query_dgram+DNS_HDRSIZE,
  93                dgram+DNS_HDRSIZE,
  94                qu->query_dglen-DNS_HDRSIZE))
  95       continue;
  96     if (viatcp) {
  97       if (qu->state != query_tcpsent) continue;
  98     } else {
  99       if (qu->state != query_tosend) continue;
 100       if (!(qu->udpsent & (1<<serv))) continue;
 101     }
 102     break;
 103   }
 104   if (!qu) {
 105     if (ads->iflags & adns_if_debug) {
 106       adns__vbuf_init(&tempvb);
 107       adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
 108                   id, adns__diag_domain(ads,serv,0,&tempvb,dgram,dglen,DNS_HDRSIZE));
 109       adns__vbuf_free(&tempvb);
 110     }
 111     return;
 112   }
 113   anstart= qu->query_dglen;
 114   arstart= -1;
 115
 116   LIST_UNLINK(ads->timew,qu);
 117   /* We're definitely going to do something with this query now */
 118
 119   switch (rcode) {
 120   case rcode_noerror:
 121   case rcode_nxdomain:
 122     break;
 123   case rcode_formaterror:
 124     adns__warn(ads,serv,qu,"server cannot understand our query (Format Error)");
 125     adns__query_fail(qu,adns_s_rcodeformaterror);
 126     return;
 127   case rcode_servfail:
 128     adns__query_fail(qu,adns_s_rcodeservfail);
 129     return;
 130   case rcode_notimp:
 131     adns__warn(ads,serv,qu,"server claims not to implement our query");
 132     adns__query_fail(qu,adns_s_rcodenotimplemented);
 133     return;
 134   case rcode_refused:
 135     adns__warn(ads,serv,qu,"server refused our query");
 136     adns__query_fail(qu,adns_s_rcoderefused);
 137     return;
 138   default:
 139     adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode);
 140     adns__query_fail(qu,adns_s_rcodeunknown);
 141     return;
 142   }
 143
 144   /* Now, take a look at the answer section, and see if it is complete.
 145    * If it has any CNAMEs we stuff them in the answer.
 146    */
 147   wantedrrs= 0;
 148   cbyte= anstart;
 149   for (rri= 0; rri<ancount; rri++) {
 150     rrstart= cbyte;
 151     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 152                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 153                      &ownermatched);
 154     if (st) { adns__query_fail(qu,st); return; }
 155     if (rrtype == -1) goto x_truncated;
 156
 157     if (rrclass != DNS_CLASS_IN) {
 158       adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d (expected IN=%d)",
 159                  rrclass,DNS_CLASS_IN);
 160       continue;
 161     }
 162     if (!ownermatched) {
 163       if (ads->iflags & adns_if_debug) {
 164         adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
 165                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rrstart));
 166       }
 167       continue;
 168     }
 169     if (rrtype == adns_r_cname &&
 170         (qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
 171       if (qu->flags & adns_qf_cname_forbid) {
 172         adns__query_fail(qu,adns_s_prohibitedcname);
 173         return;
 174       } else if (qu->cname_dgram) { /* Ignore second and subsequent CNAME(s) */
 175         adns__debug(ads,serv,qu,"allegedly canonical name %s is actually alias for %s",
 176                     qu->answer->cname,
 177                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart));
 178         adns__query_fail(qu,adns_s_prohibitedcname);
 179         return;
 180       } else if (wantedrrs) { /* Ignore CNAME(s) after RR(s). */
 181         adns__debug(ads,serv,qu,"ignoring CNAME (to %s) coexisting with RR",
 182                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart));
 183       } else {
 184         qu->cname_begin= rdstart;
 185         qu->cname_dglen= dglen;
 186         st= adns__parse_domain(ads,serv,qu, &qu->vb,
 187                                qu->flags & adns_qf_quoteok_cname ? pdf_quoteok : 0,
 188                                dgram,dglen, &rdstart,rdstart+rdlength);
 189         if (!qu->vb.used) goto x_truncated;
 190         if (st) { adns__query_fail(qu,st); return; }
 191         l= strlen(qu->vb.buf)+1;
 192         qu->answer->cname= adns__alloc_preserved(qu,l);
 193         if (!qu->answer->cname) { adns__query_fail(qu,adns_s_nomemory); return; }
 194
 195         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 196         memcpy(qu->cname_dgram,dgram,dglen);
 197
 198         memcpy(qu->answer->cname,qu->vb.buf,l);
 199         cname_here= 1;
 200         adns__update_expires(qu,ttl,now);
 201         /* If we find the answer section truncated after this point we restart
 202          * the query at the CNAME; if beforehand then we obviously have to use
 203          * TCP.  If there is no truncation we can use the whole answer if
 204          * it contains the relevant info.
 205          */
 206       }
 207     } else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
 208       wantedrrs++;
 209     } else {
 210       adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
 211     }
 212   }
 213
 214   /* We defer handling truncated responses here, in case there was a CNAME
 215    * which we could use.
 216    */
 217   if (flg_tc) goto x_truncated;
 218
 219   nsstart= cbyte;
 220
 221   if (!wantedrrs) {
 222     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 223
 224     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 225     foundsoa= 0; soattl= 0; foundns= 0;
 226     for (rri= 0; rri<nscount; rri++) {
 227       rrstart= cbyte;
 228       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 229                        &rrtype,&rrclass,&ttl, &rdlength,&rdstart, 0);
 230       if (st) { adns__query_fail(qu,st); return; }
 231       if (rrtype==-1) goto x_truncated;
 232       if (rrclass != DNS_CLASS_IN) {
 233         adns__diag(ads,serv,qu,
 234                    "ignoring authority RR with wrong class %d (expected IN=%d)",
 235                    rrclass,DNS_CLASS_IN);
 236         continue;
 237       }
 238       if (rrtype == adns_r_soa_raw) { foundsoa= 1; soattl= ttl; break; }
 239       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 240     }
 241
 242     if (rcode == rcode_nxdomain) {
 243       /* We still wanted to look for the SOA so we could find the TTL. */
 244       adns__update_expires(qu,soattl,now);
 245
 246       if (qu->flags & adns_qf_search) {
 247         adns__search_next(ads,qu,now);
 248       } else {
 249         adns__query_fail(qu,adns_s_nxdomain);
 250       }
 251       return;
 252     }
 253
 254     if (foundsoa || !foundns) {
 255       /* Aha !  A NODATA response, good. */
 256       adns__update_expires(qu,soattl,now);
 257       adns__query_fail(qu,adns_s_nodata);
 258       return;
 259     }
 260
 261     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 262      * Looks like a referral.  Just one last chance ... if we came across
 263      * a CNAME in this datagram then we should probably do our own CNAME
 264      * lookup now in the hope that we won't get a referral again.
 265      */
 266     if (cname_here) goto x_restartquery;
 267
 268     /* Bloody hell, I thought we asked for recursion ? */
 269     if (flg_rd) {
 270       adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
 271     }
 272     if (!flg_ra) {
 273       adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
 274       adns__query_fail(qu,adns_s_norecurse);
 275     } else {
 276       adns__diag(ads,serv,qu,"server claims to do recursion, but gave us a referral");
 277       adns__query_fail(qu,adns_s_invalidresponse);
 278     }
 279     return;
 280   }
 281
 282   /* Now, we have some RRs which we wanted. */
 283
 284   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
 285   if (!qu->answer->rrs.untyped) { adns__query_fail(qu,adns_s_nomemory); return; }
 286
 287   typei= qu->typei;
 288   cbyte= anstart;
 289   rrsdata= qu->answer->rrs.bytes;
 290
 291   pai.ads= qu->ads;
 292   pai.qu= qu;
 293   pai.serv= serv;
 294   pai.dgram= dgram;
 295   pai.dglen= dglen;
 296   pai.nsstart= nsstart;
 297   pai.nscount= nscount;
 298   pai.arcount= arcount;
 299   pai.now= now;
 300
 301   for (rri=0, nrrs=0; rri<ancount; rri++) {
 302     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 303                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 304                      &ownermatched);
 305     assert(!st); assert(rrtype != -1);
 306     if (rrclass != DNS_CLASS_IN ||
 307         rrtype != (qu->typei->type & adns__rrt_typemask) ||
 308         !ownermatched)
 309       continue;
 310     adns__update_expires(qu,ttl,now);
 311     st= typei->parse(&pai, rdstart,rdstart+rdlength, rrsdata+nrrs*typei->rrsz);
 312     if (st) { adns__query_fail(qu,st); return; }
 313     if (rdstart==-1) goto x_truncated;
 314     nrrs++;
 315   }
 316   assert(nrrs==wantedrrs);
 317   qu->answer->nrrs= nrrs;
 318
 319   /* This may have generated some child queries ... */
 320   if (qu->children.head) {
 321     qu->state= query_child;
 322     LIST_LINK_TAIL(ads->childw,qu);
 323     return;
 324   }
 325   adns__query_done(qu);
 326   return;
 327
 328  x_truncated:
 329
 330   if (!flg_tc) {
 331     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 332     adns__query_fail(qu,adns_s_invalidresponse);
 333     return;
 334   }
 335   qu->flags |= adns_qf_usevc;
 336
 337  x_restartquery:
 338   if (qu->cname_dgram) {
 339     st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
 340                               qu->cname_dgram, qu->cname_dglen, qu->cname_begin,
 341                               qu->typei->type, qu->flags);
 342     if (st) { adns__query_fail(qu,st); return; }
 343
 344     newquery= realloc(qu->query_dgram,qu->vb.used);
 345     if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; }
 346
 347     qu->query_dgram= newquery;
 348     qu->query_dglen= qu->vb.used;
 349     memcpy(newquery,qu->vb.buf,qu->vb.used);
 350   }
 351
 352   if (qu->state == query_tcpsent) qu->state= query_tosend;
 353   adns__reset_preserved(qu);
 354   adns__query_send(qu,now);
 355 }