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) 1997-1999 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, int viatcp, 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   unsigned long ttl, soattl;
  37   const typeinfo *typei;
  38   adns_query qu, nqu;
  39   dns_rcode rcode;
  40   adns_status st;
  41   vbuf tempvb;
  42   byte *newquery, *rrsdata;
  43   parseinfo pai;
  44
  45   if (dglen<DNS_HDRSIZE) {
  46     adns__diag(ads,serv,0,"received datagram too short for message header (%d)",dglen);
  47     return;
  48   }
  49   cbyte= 0;
  50   GET_W(cbyte,id);
  51   GET_B(cbyte,f1);
  52   GET_B(cbyte,f2);
  53   GET_W(cbyte,qdcount);
  54   GET_W(cbyte,ancount);
  55   GET_W(cbyte,nscount);
  56   GET_W(cbyte,arcount);
  57   assert(cbyte == DNS_HDRSIZE);
  58
  59   flg_qr= f1&0x80;
  60   opcode= (f1&0x78)>>3;
  61   flg_tc= f1&0x02;
  62   flg_rd= f1&0x01;
  63   flg_ra= f2&0x80;
  64   rcode= (f2&0x0f);
  65
  66   cname_here= 0;
  67
  68   if (!flg_qr) {
  69     adns__diag(ads,serv,0,"server sent us a query, not a response");
  70     return;
  71   }
  72   if (opcode) {
  73     adns__diag(ads,serv,0,"server sent us unknown opcode %d (wanted 0=QUERY)",opcode);
  74     return;
  75   }
  76   if (!qdcount) {
  77     adns__diag(ads,serv,0,"server sent reply without quoting our question");
  78     return;
  79   } else if (qdcount>1) {
  80     adns__diag(ads,serv,0,"server claimed to answer %d questions with one message",
  81                qdcount);
  82     return;
  83   }
  84   for (qu= ads->timew.head; qu; qu= nqu) {
  85     nqu= qu->next;
  86     if (qu->id != id) continue;
  87     if (dglen < qu->query_dglen) continue;
  88     if (memcmp(qu->query_dgram+DNS_HDRSIZE,
  89                dgram+DNS_HDRSIZE,
  90                qu->query_dglen-DNS_HDRSIZE))
  91       continue;
  92     if (viatcp) {
  93       if (qu->state != query_tcpsent) continue;
  94     } else {
  95       if (qu->state != query_tosend) continue;
  96       if (!(qu->udpsent & (1<<serv))) continue;
  97     }
  98     break;
  99   }
 100   if (!qu) {
 101     if (ads->iflags & adns_if_debug) {
 102       adns__vbuf_init(&tempvb);
 103       adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
 104                   id, adns__diag_domain(ads,serv,0,&tempvb,dgram,dglen,DNS_HDRSIZE));
 105       adns__vbuf_free(&tempvb);
 106     }
 107     return;
 108   }
 109   anstart= qu->query_dglen;
 110   arstart= -1;
 111
 112   LIST_UNLINK(ads->timew,qu);
 113   /* We're definitely going to do something with this query now */
 114
 115   switch (rcode) {
 116   case rcode_noerror:
 117   case rcode_nxdomain:
 118     break;
 119   case rcode_formaterror:
 120     adns__warn(ads,serv,qu,"server cannot understand our query (Format Error)");
 121     adns__query_fail(qu,adns_s_rcodeformaterror);
 122     return;
 123   case rcode_servfail:
 124     adns__query_fail(qu,adns_s_rcodeservfail);
 125     return;
 126   case rcode_notimp:
 127     adns__warn(ads,serv,qu,"server claims not to implement our query");
 128     adns__query_fail(qu,adns_s_rcodenotimplemented);
 129     return;
 130   case rcode_refused:
 131     adns__warn(ads,serv,qu,"server refused our query");
 132     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     adns__query_fail(qu,adns_s_rcodeunknown);
 137     return;
 138   }
 139
 140   /* Now, take a look at the answer section, and see if it is complete.
 141    * If it has any CNAMEs we stuff them in the answer.
 142    */
 143   wantedrrs= 0;
 144   cbyte= anstart;
 145   for (rri= 0; rri<ancount; rri++) {
 146     rrstart= cbyte;
 147     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 148                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 149                      &ownermatched);
 150     if (st) { adns__query_fail(qu,st); return; }
 151     if (rrtype == -1) goto x_truncated;
 152
 153     if (rrclass != DNS_CLASS_IN) {
 154       adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d (expected IN=%d)",
 155                  rrclass,DNS_CLASS_IN);
 156       continue;
 157     }
 158     if (!ownermatched) {
 159       if (ads->iflags & adns_if_debug) {
 160         adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
 161                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rrstart));
 162       }
 163       continue;
 164     }
 165     if (rrtype == adns_r_cname &&
 166         (qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
 167       if (qu->flags & adns_qf_cname_forbid) {
 168         adns__query_fail(qu,adns_s_prohibitedcname);
 169         return;
 170       } else if (!qu->cname_dgram) { /* Ignore second and subsequent CNAMEs */
 171         qu->cname_begin= rdstart;
 172         qu->cname_dglen= dglen;
 173         st= adns__parse_domain(ads,serv,qu, &qu->vb,
 174                                qu->flags & adns_qf_quoteok_cname ? pdf_quoteok : 0,
 175                                dgram,dglen, &rdstart,rdstart+rdlength);
 176         if (!qu->vb.used) goto x_truncated;
 177         if (st) { adns__query_fail(qu,st); return; }
 178         l= strlen(qu->vb.buf)+1;
 179         qu->answer->cname= adns__alloc_preserved(qu,l);
 180         if (!qu->answer->cname) { adns__query_fail(qu,adns_s_nomemory); return; }
 181
 182         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 183         memcpy(qu->cname_dgram,dgram,dglen);
 184
 185         memcpy(qu->answer->cname,qu->vb.buf,l);
 186         cname_here= 1;
 187         adns__update_expires(qu,ttl,now);
 188         /* If we find the answer section truncated after this point we restart
 189          * the query at the CNAME; if beforehand then we obviously have to use
 190          * TCP.  If there is no truncation we can use the whole answer if
 191          * it contains the relevant info.
 192          */
 193       } else {
 194         adns__debug(ads,serv,qu,"ignoring duplicate CNAME (%s, as well as %s)",
 195                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart),
 196                     qu->answer->cname);
 197       }
 198     } else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
 199       wantedrrs++;
 200     } else {
 201       adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
 202     }
 203   }
 204
 205   /* We defer handling truncated responses here, in case there was a CNAME
 206    * which we could use.
 207    */
 208   if (flg_tc) goto x_truncated;
 209
 210   nsstart= cbyte;
 211
 212   if (!wantedrrs) {
 213     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 214
 215     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 216     foundsoa= 0; soattl= 0; foundns= 0;
 217     for (rri= 0; rri<nscount; rri++) {
 218       rrstart= cbyte;
 219       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 220                        &rrtype,&rrclass,&ttl, &rdlength,&rdstart, 0);
 221       if (st) { adns__query_fail(qu,st); return; }
 222       if (rrtype==-1) goto x_truncated;
 223       if (rrclass != DNS_CLASS_IN) {
 224         adns__diag(ads,serv,qu,
 225                    "ignoring authority RR with wrong class %d (expected IN=%d)",
 226                    rrclass,DNS_CLASS_IN);
 227         continue;
 228       }
 229       if (rrtype == adns_r_soa_raw) { foundsoa= 1; soattl= ttl; break; }
 230       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 231     }
 232
 233     if (rcode == rcode_nxdomain) {
 234       /* We still wanted to look for the SOA so we could find the TTL. */
 235       adns__update_expires(qu,soattl,now);
 236
 237       if (qu->flags & adns_qf_search) {
 238         adns__search_next(ads,qu,now);
 239       } else {
 240         adns__query_fail(qu,adns_s_nxdomain);
 241       }
 242       return;
 243     }
 244
 245     if (foundsoa || !foundns) {
 246       /* Aha !  A NODATA response, good. */
 247       adns__update_expires(qu,soattl,now);
 248       adns__query_fail(qu,adns_s_nodata);
 249       return;
 250     }
 251
 252     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 253      * Looks like a referral.  Just one last chance ... if we came across
 254      * a CNAME in this datagram then we should probably do our own CNAME
 255      * lookup now in the hope that we won't get a referral again.
 256      */
 257     if (cname_here) goto x_restartquery;
 258
 259     /* Bloody hell, I thought we asked for recursion ? */
 260     if (flg_rd) {
 261       adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
 262     }
 263     if (!flg_ra) {
 264       adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
 265       adns__query_fail(qu,adns_s_norecurse);
 266     } else {
 267       adns__diag(ads,serv,qu,"server claims to do recursion, but gave us a referral");
 268       adns__query_fail(qu,adns_s_invalidresponse);
 269     }
 270     return;
 271   }
 272
 273   /* Now, we have some RRs which we wanted. */
 274
 275   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
 276   if (!qu->answer->rrs.untyped) { adns__query_fail(qu,adns_s_nomemory); return; }
 277
 278   typei= qu->typei;
 279   cbyte= anstart;
 280   rrsdata= qu->answer->rrs.bytes;
 281
 282   pai.ads= qu->ads;
 283   pai.qu= qu;
 284   pai.serv= serv;
 285   pai.dgram= dgram;
 286   pai.dglen= dglen;
 287   pai.nsstart= nsstart;
 288   pai.nscount= nscount;
 289   pai.arcount= arcount;
 290   pai.now= now;
 291
 292   for (rri=0, nrrs=0; rri<ancount; rri++) {
 293     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 294                      &rrtype,&rrclass,&ttl, &rdlength,&rdstart,
 295                      &ownermatched);
 296     assert(!st); assert(rrtype != -1);
 297     if (rrclass != DNS_CLASS_IN ||
 298         rrtype != (qu->typei->type & adns__rrt_typemask) ||
 299         !ownermatched)
 300       continue;
 301     adns__update_expires(qu,ttl,now);
 302     st= typei->parse(&pai, rdstart,rdstart+rdlength, rrsdata+nrrs*typei->rrsz);
 303     if (st) { adns__query_fail(qu,st); return; }
 304     if (rdstart==-1) goto x_truncated;
 305     nrrs++;
 306   }
 307   assert(nrrs==wantedrrs);
 308   qu->answer->nrrs= nrrs;
 309
 310   /* This may have generated some child queries ... */
 311   if (qu->children.head) {
 312     qu->state= query_child;
 313     LIST_LINK_TAIL(ads->childw,qu);
 314     return;
 315   }
 316   adns__query_done(qu);
 317   return;
 318
 319  x_truncated:
 320
 321   if (!flg_tc) {
 322     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 323     adns__query_fail(qu,adns_s_invalidresponse);
 324     return;
 325   }
 326   qu->flags |= adns_qf_usevc;
 327
 328  x_restartquery:
 329   if (qu->cname_dgram) {
 330     st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
 331                               qu->cname_dgram, qu->cname_dglen, qu->cname_begin,
 332                               qu->typei->type, qu->flags);
 333     if (st) { adns__query_fail(qu,st); return; }
 334
 335     newquery= realloc(qu->query_dgram,qu->vb.used);
 336     if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; }
 337
 338     qu->query_dgram= newquery;
 339     qu->query_dglen= qu->vb.used;
 340     memcpy(newquery,qu->vb.buf,qu->vb.used);
 341   }
 342
 343   if (qu->state == query_tcpsent) qu->state= query_tosend;
 344   adns__reset_preserved(qu);
 345   adns__query_send(qu,now);
 346 }