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 Copyright (C) 1997, 1998 Ian Jackson
   7  *
   8  *  This program is free software; you can redistribute it and/or modify
   9  *  it under the terms of the GNU General Public License as published by
  10  *  the Free Software Foundation; either version 2, or (at your option)
  11  *  any later version.
  12  *
  13  *  This program is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *  GNU General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU General Public License
  19  *  along with this program; if not, write to the Free Software Foundation,
  20  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  21  */
  22
  23 #include <stdlib.h>
  24 #include <string.h>
  25
  26 #include "internal.h"
  27
  28 void adns__procdgram(adns_state ads, const byte *dgram, int dglen,
  29                      int serv, struct timeval now) {
  30   int cbyte, rrstart, wantedrrs, rri, foundsoa, foundns, cname_here;
  31   int id, f1, f2, qdcount, ancount, nscount, arcount;
  32   int flg_ra, flg_rd, flg_tc, flg_qr, opcode;
  33   int rrtype, rrclass, rdlength, rdstart;
  34   int anstart, nsstart, arstart;
  35   int ownermatched, l, nrrs;
  36   const typeinfo *typei;
  37   adns_query qu, nqu;
  38   dns_rcode rcode;
  39   adns_status st;
  40   vbuf tempvb;
  41   byte *newquery, *rrsdata;
  42   parseinfo pai;
  43
  44   if (dglen<DNS_HDRSIZE) {
  45     adns__diag(ads,serv,0,"received datagram too short for message header (%d)",dglen);
  46     return;
  47   }
  48   cbyte= 0;
  49   GET_W(cbyte,id);
  50   GET_B(cbyte,f1);
  51   GET_B(cbyte,f2);
  52   GET_W(cbyte,qdcount);
  53   GET_W(cbyte,ancount);
  54   GET_W(cbyte,nscount);
  55   GET_W(cbyte,arcount);
  56   assert(cbyte == DNS_HDRSIZE);
  57
  58   flg_qr= f1&0x80;
  59   opcode= (f1&0x78)>>3;
  60   flg_tc= f1&0x02;
  61   flg_rd= f1&0x01;
  62   flg_ra= f2&0x80;
  63   rcode= (f2&0x0f);
  64
  65   cname_here= 0;
  66
  67   if (!flg_qr) {
  68     adns__diag(ads,serv,0,"server sent us a query, not a response");
  69     return;
  70   }
  71   if (opcode) {
  72     adns__diag(ads,serv,0,"server sent us unknown opcode %d (wanted 0=QUERY)",opcode);
  73     return;
  74   }
  75   if (!qdcount) {
  76     adns__diag(ads,serv,0,"server sent reply without quoting our question");
  77     return;
  78   } else if (qdcount>1) {
  79     adns__diag(ads,serv,0,"server claimed to answer %d questions with one message",
  80                qdcount);
  81     return;
  82   }
  83   for (qu= ads->timew.head; qu; qu= nqu) {
  84     nqu= qu->next;
  85     if (qu->id != id) continue;
  86     if (dglen < qu->query_dglen) continue;
  87     if (memcmp(qu->query_dgram+DNS_HDRSIZE,
  88                dgram+DNS_HDRSIZE,
  89                qu->query_dglen-DNS_HDRSIZE))
  90       continue;
  91     break;
  92   }
  93   if (!qu) {
  94     if (ads->iflags & adns_if_debug) {
  95       adns__vbuf_init(&tempvb);
  96       adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
  97                   id, adns__diag_domain(ads,serv,0,&tempvb,dgram,dglen,DNS_HDRSIZE));
  98       adns__vbuf_free(&tempvb);
  99     }
 100     return;
 101   }
 102   anstart= qu->query_dglen;
 103   arstart= -1;
 104
 105   LIST_UNLINK(ads->timew,qu);
 106   /* We're definitely going to do something with this query now */
 107
 108   switch (rcode) {
 109   case rcode_noerror:
 110   case rcode_nxdomain:
 111     break;
 112   case rcode_formaterror:
 113     adns__warn(ads,serv,qu,"server cannot understand our query (Format Error)");
 114     adns__query_fail(qu,adns_s_rcodeformaterror);
 115     return;
 116   case rcode_servfail:
 117     adns__query_fail(qu,adns_s_rcodeservfail);
 118     return;
 119   case rcode_notimp:
 120     adns__warn(ads,serv,qu,"server claims not to implement our query");
 121     adns__query_fail(qu,adns_s_rcodenotimplemented);
 122     return;
 123   case rcode_refused:
 124     adns__warn(ads,serv,qu,"server refused our query");
 125     adns__query_fail(qu,adns_s_rcoderefused);
 126     return;
 127   default:
 128     adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode);
 129     adns__query_fail(qu,adns_s_rcodeunknown);
 130     return;
 131   }
 132
 133   /* Now, take a look at the answer section, and see if it is complete.
 134    * If it has any CNAMEs we stuff them in the answer.
 135    */
 136   wantedrrs= 0;
 137   cbyte= anstart;
 138   for (rri= 0; rri<ancount; rri++) {
 139     rrstart= cbyte;
 140     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 141                      &rrtype,&rrclass,&rdlength,&rdstart,
 142                      &ownermatched);
 143     if (st) { adns__query_fail(qu,st); return; }
 144     if (rrtype == -1) goto x_truncated;
 145
 146     if (rrclass != DNS_CLASS_IN) {
 147       adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d (expected IN=%d)",
 148                  rrclass,DNS_CLASS_IN);
 149       continue;
 150     }
 151     if (!ownermatched) {
 152       if (ads->iflags & adns_if_debug) {
 153         adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
 154                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rrstart));
 155       }
 156       continue;
 157     }
 158     if (rrtype == adns_r_cname && /* fixme - implement adns_qf_nocname */
 159         (qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
 160       if (qu->flags & adns_qf_cname_forbid) {
 161         adns__query_fail(qu,adns_s_prohibitedcname);
 162         return;
 163       } else if (!qu->cname_dgram) { /* Ignore second and subsequent CNAMEs */
 164         qu->cname_begin= rdstart;
 165         qu->cname_dglen= dglen;
 166         st= adns__parse_domain(ads,serv,qu, &qu->vb,
 167                                qu->flags & adns_qf_quoteok_cname ? pdf_quoteok : 0,
 168                                dgram,dglen, &rdstart,rdstart+rdlength);
 169         if (!qu->vb.used) goto x_truncated;
 170         if (st) { adns__query_fail(qu,st); return; }
 171         l= strlen(qu->vb.buf)+1;
 172         qu->answer->cname= adns__alloc_interim(qu,l);
 173         if (!qu->answer->cname) { adns__query_fail(qu,adns_s_nomemory); return; }
 174
 175         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 176         memcpy(qu->cname_dgram,dgram,dglen);
 177
 178         memcpy(qu->answer->cname,qu->vb.buf,l);
 179         cname_here= 1;
 180         /* If we find the answer section truncated after this point we restart
 181          * the query at the CNAME; if beforehand then we obviously have to use
 182          * TCP.  If there is no truncation we can use the whole answer if
 183          * it contains the relevant info.
 184          */
 185       } else {
 186         adns__debug(ads,serv,qu,"ignoring duplicate CNAME (%s, as well as %s)",
 187                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart),
 188                     qu->answer->cname);
 189       }
 190     } else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
 191       wantedrrs++;
 192     } else {
 193       adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
 194     }
 195   }
 196
 197   /* We defer handling truncated responses here, in case there was a CNAME
 198    * which we could use.
 199    */
 200   if (flg_tc) goto x_truncated;
 201
 202   nsstart= cbyte;
 203
 204   if (!wantedrrs) {
 205     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 206
 207     if (rcode == rcode_nxdomain) {
 208       adns__query_fail(qu,adns_s_nxdomain);
 209       return;
 210     }
 211
 212     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 213     foundsoa= 0; foundns= 0;
 214     for (rri= 0; rri<nscount; rri++) {
 215       rrstart= cbyte;
 216       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 217                        &rrtype,&rrclass,&rdlength,&rdstart, 0);
 218       if (st) { adns__query_fail(qu,st); return; }
 219       if (rrtype==-1) goto x_truncated;
 220       if (rrclass != DNS_CLASS_IN) {
 221         adns__diag(ads,serv,qu,
 222                    "ignoring authority RR with wrong class %d (expected IN=%d)",
 223                    rrclass,DNS_CLASS_IN);
 224         continue;
 225       }
 226       if (rrtype == adns_r_soa_raw) { foundsoa= 1; break; }
 227       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 228     }
 229
 230     if (foundsoa || !foundns) {
 231       /* Aha !  A NODATA response, good. */
 232       adns__query_fail(qu,adns_s_nodata);
 233       return;
 234     }
 235
 236     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 237      * Looks like a referral.  Just one last chance ... if we came across
 238      * a CNAME in this datagram then we should probably do our own CNAME
 239      * lookup now in the hope that we won't get a referral again.
 240      */
 241     if (cname_here) goto x_restartquery;
 242
 243     /* Bloody hell, I thought we asked for recursion ? */
 244     if (flg_rd) {
 245       adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
 246     }
 247     if (!flg_ra) {
 248       adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
 249       adns__query_fail(qu,adns_s_norecurse);
 250     } else {
 251       adns__diag(ads,serv,qu,"server claims to do recursion, but gave us a referral");
 252       adns__query_fail(qu,adns_s_invalidresponse);
 253     }
 254     return;
 255   }
 256
 257   /* Now, we have some RRs which we wanted. */
 258
 259   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
 260   if (!qu->answer->rrs.untyped) { adns__query_fail(qu,adns_s_nomemory); return; }
 261
 262   typei= qu->typei;
 263   cbyte= anstart;
 264   rrsdata= qu->answer->rrs.bytes;
 265
 266   pai.ads= qu->ads;
 267   pai.qu= qu;
 268   pai.serv= serv;
 269   pai.dgram= dgram;
 270   pai.dglen= dglen;
 271   pai.nsstart= nsstart;
 272   pai.nscount= nscount;
 273   pai.arcount= arcount;
 274   pai.now= now;
 275
 276   for (rri=0, nrrs=0; rri<ancount; rri++) {
 277     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 278                      &rrtype,&rrclass,&rdlength,&rdstart,
 279                      &ownermatched);
 280     assert(!st); assert(rrtype != -1);
 281     if (rrclass != DNS_CLASS_IN ||
 282         rrtype != (qu->typei->type & adns__rrt_typemask) ||
 283         !ownermatched)
 284       continue;
 285     st= typei->parse(&pai, rdstart,rdstart+rdlength, rrsdata+nrrs*typei->rrsz);
 286     if (st) { adns__query_fail(qu,st); return; }
 287     if (rdstart==-1) goto x_truncated;
 288     nrrs++;
 289   }
 290   assert(nrrs==wantedrrs);
 291   qu->answer->nrrs= nrrs;
 292
 293   /* This may have generated some child queries ... */
 294   if (qu->children.head) {
 295     qu->state= query_child;
 296     LIST_LINK_TAIL(ads->childw,qu);
 297     return;
 298   }
 299
 300   adns__query_done(qu);
 301   return;
 302
 303  x_truncated:
 304
 305   if (!flg_tc) {
 306     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 307     adns__query_fail(qu,adns_s_invalidresponse);
 308     return;
 309   }
 310   qu->flags |= adns_qf_usevc;
 311
 312  x_restartquery:
 313
 314   if (qu->cname_dgram) {
 315     st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
 316                               qu->cname_dgram, qu->cname_dglen, qu->cname_begin,
 317                               qu->typei->type, qu->flags);
 318     if (st) { adns__query_fail(qu,st); return; }
 319
 320     newquery= realloc(qu->query_dgram,qu->vb.used);
 321     if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; }
 322
 323     qu->query_dgram= newquery;
 324     qu->query_dglen= qu->vb.used;
 325     memcpy(newquery,qu->vb.buf,qu->vb.used);
 326   }
 327
 328   adns__reset_cnameonly(qu);
 329   adns__query_udp(qu,now);
 330 }