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