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, place;
  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
 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, dgram,dglen,rrstart));
 153       }
 154       continue;
 155     }
 156     if (rrtype == adns_r_cname && /* fixme - implement adns_qf_nocname */
 157         (qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
 158       if (!qu->cname_dgram) { /* Ignore second and subsequent CNAMEs */
 159         qu->cname_begin= rdstart;
 160         qu->cname_dglen= dglen;
 161         st= adns__parse_domain(ads,serv,qu, &qu->vb,
 162                                qu->flags & adns_qf_quoteok_cname ? pdf_quoteok : 0,
 163                                dgram,dglen, &rdstart,rdstart+rdlength);
 164         if (!qu->vb.used) goto x_truncated;
 165         if (st) { adns__query_fail(qu,st); return; }
 166         l= strlen(qu->vb.buf)+1;
 167         qu->answer->cname= adns__alloc_interim(qu,l);
 168         if (!qu->answer->cname) { adns__query_fail(qu,adns_s_nolocalmem); return; }
 169
 170         qu->cname_dgram= adns__alloc_mine(qu,dglen);
 171         memcpy(qu->cname_dgram,dgram,dglen);
 172
 173         memcpy(qu->answer->cname,qu->vb.buf,l);
 174         cname_here= 1;
 175         /* If we find the answer section truncated after this point we restart
 176          * the query at the CNAME; if beforehand then we obviously have to use
 177          * TCP.  If there is no truncation we can use the whole answer if
 178          * it contains the relevant info.
 179          */
 180       } else {
 181         adns__debug(ads,serv,qu,"ignoring duplicate CNAME (%s, as well as %s)",
 182                     adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart),
 183                     qu->answer->cname);
 184       }
 185     } else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
 186       wantedrrs++;
 187     } else {
 188       adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
 189     }
 190   }
 191
 192   /* We defer handling truncated responses here, in case there was a CNAME
 193    * which we could use.
 194    */
 195   if (flg_tc) goto x_truncated;
 196
 197   nsstart= cbyte;
 198
 199   if (!wantedrrs) {
 200     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 201
 202     if (rcode == rcode_nxdomain) {
 203       adns__query_fail(qu,adns_s_nxdomain);
 204       return;
 205     }
 206
 207     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 208     foundsoa= 0; foundns= 0;
 209     for (rri= 0; rri<nscount; rri++) {
 210       rrstart= cbyte;
 211       st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 212                        &rrtype,&rrclass,&rdlength,&rdstart, 0);
 213       if (st) { adns__query_fail(qu,st); return; }
 214       if (rrtype==-1) goto x_truncated;
 215       if (rrclass != DNS_CLASS_IN) {
 216         adns__diag(ads,serv,qu,
 217                    "ignoring authority RR with wrong class %d (expected IN=%d)",
 218                    rrclass,DNS_CLASS_IN);
 219         continue;
 220       }
 221       if (rrtype == adns_r_soa_raw) { foundsoa= 1; break; }
 222       else if (rrtype == adns_r_ns_raw) { foundns= 1; }
 223     }
 224
 225     if (foundsoa || !foundns) {
 226       /* Aha !  A NODATA response, good. */
 227       adns__query_fail(qu,adns_s_nodata);
 228       return;
 229     }
 230
 231     /* Now what ?  No relevant answers, no SOA, and at least some NS's.
 232      * Looks like a referral.  Just one last chance ... if we came across
 233      * a CNAME in this datagram then we should probably do our own CNAME
 234      * lookup now in the hope that we won't get a referral again.
 235      */
 236     if (cname_here) goto x_restartquery;
 237
 238     /* Bloody hell, I thought we asked for recursion ? */
 239     if (flg_rd) {
 240       adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
 241     }
 242     if (!flg_ra) {
 243       adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
 244       adns__query_fail(qu,adns_s_norecurse);
 245     } else {
 246       adns__diag(ads,serv,qu,"server claims to do recursion, but gave us a referral");
 247       adns__query_fail(qu,adns_s_serverfaulty);
 248     }
 249     return;
 250   }
 251
 252   /* Now, we have some RRs which we wanted. */
 253
 254   qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
 255   if (!qu->answer->rrs.untyped) { adns__query_fail(qu,adns_s_nolocalmem); return; }
 256
 257   typei= qu->typei;
 258   cbyte= anstart;
 259   arstart= -1;
 260   rrsdata= qu->answer->rrs.bytes;
 261
 262   if (typei->diff_needswap) {
 263     if (!adns__vbuf_ensure(&qu->vb,typei->rrsz)) {
 264       adns__query_fail(qu,adns_s_nolocalmem);
 265       return;
 266     }
 267   }
 268   nrrs= 0;
 269
 270   for (rri=0; rri<ancount; rri++) {
 271     st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
 272                      &rrtype,&rrclass,&rdlength,&rdstart,
 273                      &ownermatched);
 274     assert(!st); assert(rrtype != -1);
 275     if (rrclass != DNS_CLASS_IN ||
 276         rrtype != (qu->typei->type & adns__rrt_typemask) ||
 277         !ownermatched)
 278       continue;
 279     st= typei->parse(qu,serv, dgram,dglen, rdstart,rdstart+rdlength,
 280                      rrsdata+nrrs*typei->rrsz);
 281     if (st) { adns__query_fail(qu,st); return; }
 282     if (rdstart==-1) goto x_truncated;
 283
 284     if (typei->diff_needswap) {
 285       for (place= nrrs;
 286            place>0 && typei->diff_needswap(rrsdata+(place-1)*typei->rrsz,
 287                                            rrsdata+nrrs*typei->rrsz);
 288            place--);
 289       if (place != nrrs) {
 290         memcpy(qu->vb.buf,rrsdata+nrrs*typei->rrsz,typei->rrsz);
 291         memmove(rrsdata+(place+1)*typei->rrsz,
 292                 rrsdata+place*typei->rrsz,
 293                 (nrrs-place)*typei->rrsz);
 294         memcpy(rrsdata+place*typei->rrsz,qu->vb.buf,typei->rrsz);
 295       }
 296     }
 297     nrrs++;
 298   }
 299   assert(nrrs==wantedrrs);
 300   qu->answer->nrrs= nrrs;
 301
 302   /* This may have generated some child queries ... */
 303   if (qu->children.head) {
 304     qu->state= query_child;
 305     LIST_LINK_TAIL(ads->childw,qu);
 306     return;
 307   }
 308
 309   adns__query_done(qu);
 310   return;
 311
 312  x_truncated:
 313
 314   if (!flg_tc) {
 315     adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
 316     adns__query_fail(qu,adns_s_serverfaulty);
 317     return;
 318   }
 319   qu->flags |= adns_qf_usevc;
 320
 321  x_restartquery:
 322
 323   if (qu->cname_dgram) {
 324     st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
 325                               qu->cname_dgram, qu->cname_dglen, qu->cname_begin,
 326                               qu->typei->type, qu->flags);
 327     if (st) { adns__query_fail(qu,st); return; }
 328
 329     newquery= realloc(qu->query_dgram,qu->vb.used);
 330     if (!newquery) { adns__query_fail(qu,adns_s_nolocalmem); return; }
 331
 332     qu->query_dgram= newquery;
 333     qu->query_dglen= qu->vb.used;
 334     memcpy(newquery,qu->vb.buf,qu->vb.used);
 335   }
 336
 337   adns__reset_cnameonly(qu);
 338   adns__query_udp(qu,now);
 339 }