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