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