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 "internal.h"
  24
  25 static void cname_recurse(adns_query qu, adns_queryflags xflags) {
  26   adns__diag(qu->ads,-1,qu,"cname following not implemented fixme");
  27   adns__query_fail(qu,adns_s_notimplemented);
  28 }
  29
  30 void adns__procdgram(adns_state ads, const byte *dgram, int dglen,
  31                      int serv, 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, ownermatched, l;
  36   int anstart, nsstart, arstart;
  37   adns_query qu, nqu;
  38   dns_rcode rcode;
  39   adns_status st;
  40   vbuf tempvb;
  41
  42   if (dglen<DNS_HDRSIZE) {
  43     adns__diag(ads,serv,0,"received datagram too short for message header (%d)",dglen);
  44     return;
  45   }
  46   cbyte= 0;
  47   GET_W(cbyte,id);
  48   GET_B(cbyte,f1);
  49   GET_B(cbyte,f2);
  50   GET_W(cbyte,qdcount);
  51   GET_W(cbyte,ancount);
  52   GET_W(cbyte,nscount);
  53   GET_W(cbyte,arcount);
  54   assert(cbyte == DNS_HDRSIZE);
  55
  56   flg_qr= f1&0x80;
  57   opcode= (f1&0x78)>>3;
  58   flg_tc= f1&0x20;
  59   flg_rd= f1&0x01;
  60   flg_ra= f2&0x80;
  61   rcode= (f2&0x0f);
  62
  63   cname_here= 0;
  64
  65   if (!flg_qr) {
  66     adns__diag(ads,serv,0,"server sent us a query, not a response");
  67     return;
  68   }
  69   if (opcode) {
  70     adns__diag(ads,serv,0,"server sent us unknown opcode %d (wanted 0=QUERY)",opcode);
  71     return;
  72   }
  73   if (!qdcount) {
  74     adns__diag(ads,serv,0,"server sent reply without quoting our question");
  75     return;
  76   } else if (qdcount>1) {
  77     adns__diag(ads,serv,0,"server claimed to answer %d questions with one message",
  78                qdcount);
  79     return;
  80   }
  81   for (qu= ads->timew.head; qu; qu= nqu) {
  82     nqu= qu->next;
  83     if (qu->id != id) continue;
  84     if (dglen < qu->query_dglen) continue;
  85     if (memcmp(qu->query_dgram+DNS_HDRSIZE,
  86                dgram+DNS_HDRSIZE,
  87                qu->query_dglen-DNS_HDRSIZE))
  88       continue;
  89     break;
  90   }
  91   if (!qu) {
  92     if (ads->iflags & adns_if_debug) {
  93       adns__vbuf_init(&tempvb);
  94       adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
  95                   id, adns__diag_domain(ads,serv,0,&tempvb,adns_qf_anyquote,
  96                                         dgram,dglen,DNS_HDRSIZE));
  97       adns__vbuf_free(&tempvb);
  98     }
  99     return;
 100   }
 101   anstart= qu->query_dglen;
 102
 103   LIST_UNLINK(ads->timew,qu);
 104   /* We're definitely going to do something with this query now */
 105
 106   switch (rcode) {
 107   case rcode_noerror:
 108   case rcode_nxdomain:
 109     break;
 110   case rcode_formaterror:
 111     adns__warn(ads,serv,qu,"server cannot understand our query (Format Error)");
 112     adns__query_fail(qu,adns_s_serverfaulty);
 113     return;
 114   case rcode_servfail:
 115     adns__query_fail(qu,adns_s_servfail);
 116     return;
 117   case rcode_notimp:
 118     adns__warn(ads,serv,qu,"server claims not to implement our query");
 119     adns__query_fail(qu,adns_s_notimplemented);
 120     return;
 121   case rcode_refused:
 122     adns__warn(ads,serv,qu,"server refused our query");
 123     adns__query_fail(qu,adns_s_refused);
 124     return;
 125   default:
 126     adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode);
 127     adns__query_fail(qu,adns_s_reasonunknown);
 128     return;
 129   }
 130
 131   /* Now, take a look at the answer section, and see if it is complete.
 132    * If it has any CNAMEs we stuff them in the answer.
 133    */
 134   wantedrrs= 0;
 135   cbyte= anstart;
 136   for (rri= 0; rri<ancount; rri++) {
 137     rrstart= cbyte;
 138     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 139                      &rrtype,&rrclass,&rdlength,&rdstart,
 140                      &ownermatched);
 141     if (st) { adns__query_fail(qu,st); return; }
 142     if (rrtype == -1) goto x_truncated;
 143
 144     if (rrclass != DNS_CLASS_IN) {
 145       adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d (expected IN=%d)",
 146                  rrclass,DNS_CLASS_IN);
 147       continue;
 148     }
 149     if (!ownermatched) {
 150       if (ads->iflags & adns_if_debug) {
 151         adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
 152                     adns__diag_domain(ads,serv,qu, &qu->vb,qu->flags,
 153                                       dgram,dglen,rrstart));
 154       }
 155       continue;
 156     }
 157     if (rrtype == adns_r_cname &&
 158         (qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
 159       if (!qu->cname_dgram) { /* Ignore second and subsequent CNAMEs */
 160         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 161         if (!qu->cname_dgram) return;
 162         qu->cname_begin= rdstart;
 163         qu->cname_dglen= dglen;
 164         st= adns__parse_domain(ads,serv,qu, &qu->vb,qu->flags,
 165                                dgram,dglen, &rdstart,rdstart+rdlength);
 166         if (!qu->vb.used) goto x_truncated;
 167         if (st) { adns__query_fail(qu,st); return; }
 168         l= strlen(qu->vb.buf)+1;
 169         qu->answer->cname= adns__alloc_interim(qu,l);
 170         if (!qu->answer->cname) return;
 171         memcpy(qu->answer->cname,qu->vb.buf,l);
 172         cname_here= 1;
 173         /* If we find the answer section truncated after this point we restart
 174          * the query at the CNAME; if beforehand then we obviously have to use
 175          * TCP.  If there is no truncation we can use the whole answer if
 176          * it contains the relevant info.
 177          */
 178       } else {
 179         adns__debug(ads,serv,qu,"ignoring duplicate CNAME (%s, as well as %s)",
 180                     adns__diag_domain(ads,serv,qu, &qu->vb,qu->flags,
 181                                       dgram,dglen,rdstart),
 182                     qu->answer->cname);
 183       }
 184     } else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
 185       wantedrrs++;
 186     } else {
 187       adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
 188     }
 189   }
 190
 191   /* If we got here then the answer section is intact. */
 192   nsstart= cbyte;
 193
 194   if (!wantedrrs) {
 195     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 196
 197     if (rcode == rcode_nxdomain) {
 198       adns__query_fail(qu,adns_s_nxdomain);
 199       return;
 200     }
 201
 202     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 203     foundsoa= 0; foundns= 0;
 204     for (rri= 0; rri<nscount; rri++) {
 205       rrstart= cbyte;
 206       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 207                        &rrtype,&rrclass,&rdlength,&rdstart, 0);
 208       if (st) { adns__query_fail(qu,st); return; }
 209       if (rrtype==-1) goto x_truncated;
 210       if (rrclass != DNS_CLASS_IN) {
 211         adns__diag(ads,serv,qu,
 212                    "ignoring authority RR with wrong class %d (expected IN=%d)",
 213                    rrclass,DNS_CLASS_IN);
 214         continue;
 215       }
 216       if (rrtype == adns_r_soa_raw) { foundsoa= 1; break; }
 217       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 218     }
 219
 220     if (foundsoa || !foundns) {
 221       /* Aha !  A NODATA response, good. */
 222       adns__query_fail(qu,adns_s_nodata);
 223       return;
 224     }
 225
 226     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 227      * Looks like a referral.  Just one last chance ... if we came across
 228      * a CNAME in this datagram then we should probably do our own CNAME
 229      * lookup now in the hope that we won't get a referral again.
 230      */
 231     if (cname_here) { cname_recurse(qu,0); return; }
 232
 233     /* Bloody hell, I thought we asked for recursion ? */
 234     if (flg_rd) {
 235       adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
 236     }
 237     if (!flg_ra) {
 238       adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
 239       adns__query_fail(qu,adns_s_norecurse);
 240     } else {
 241       adns__diag(ads,serv,qu,"server claims to do recursion, but gave us a referral");
 242       adns__query_fail(qu,adns_s_serverfaulty);
 243     }
 244     return;
 245   }
 246
 247   /* Now, we have some RRs which we wanted. */
 248
 249   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
 250   if (!qu->answer->rrs.untyped) return;
 251
 252   cbyte= anstart;
 253   arstart= -1;
 254   for (rri=0; rri<ancount; rri++) {
 255     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 256                      &rrtype,&rrclass,&rdlength,&rdstart,
 257                      &ownermatched);
 258     assert(!st); assert(rrtype != -1);
 259     if (rrclass != DNS_CLASS_IN ||
 260         rrtype != (qu->typei->type & adns__rrt_typemask) ||
 261         !ownermatched)
 262       continue;
 263     assert(qu->answer->nrrs<wantedrrs);
 264     st= qu->typei->parse(qu,serv,
 265                          dgram,dglen, rdstart,rdstart+rdlength,
 266                          qu->answer->rrs.bytes+qu->answer->nrrs*qu->typei->rrsz);
 267     if (st) { adns__query_fail(qu,st); return; }
 268     if (rdstart==-1) goto x_truncated;
 269     qu->answer->nrrs++;
 270   }
 271
 272   /* This may have generated some child queries ... */
 273   if (qu->children.head) {
 274     qu->state= query_child;
 275     LIST_LINK_TAIL(ads->childw,qu);
 276     return;
 277   }
 278
 279   adns__query_done(qu);
 280   return;
 281
 282  x_truncated:
 283   if (!flg_tc) {
 284     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 285     adns__query_fail(qu,adns_s_serverfaulty);
 286     return;
 287   }
 288   if (qu->cname_dgram) { cname_recurse(qu,adns_qf_usevc); return; }
 289   adns__reset_cnameonly(qu);
 290   qu->flags |= adns_qf_usevc;
 291   adns__query_udp(qu,now);
 292 }