mdw@git.distorted.org.uk Git - adns/blob - src/reply.c

   1 /**/
   2
   3 #include "internal.h"
   4
   5 typedef enum {
   6   rcode_noerror,
   7   rcode_formaterror,
   8   rcode_servfail,
   9   rcode_nxdomain,
  10   rcode_notimp,
  11   rcode_refused
  12 } dns_rcode;
  13
  14 #define GETIL_B(cb) (dgram[*(cb)++])
  15 #define GET_B(cb,tv) ((tv)= GETIL_B((cb)))
  16 #define GET_W(cb,tv) ((tv)=0, (tv)|=(GETIL_B((cb))<<8), (tv)|=GETIL_B(cb), (tv))
  17
  18 static void vbuf__append_quoted1035(vbuf *vb, const byte *buf, int len) {
  19   char qbuf[10];
  20   int i;
  21
  22   while (len) {
  23     qbuf[0]= 0;
  24     for (i=0; i<len; i++) {
  25       ch= buf[i];
  26       if (ch == '.' || ch == '"' || ch == '(' || ch == ')' ||
  27           ch == '@' || ch == ';' || ch == '$') {
  28         sprintf(qbuf,"\\%c",ch);
  29         break;
  30       } else if (ch <= ' ' || ch >= 127) {
  31         sprintf(qbuf,"\\%03o",ch);
  32         break;
  33       }
  34     }
  35     if (!adns__vbuf_append(vb,buf,i) || !adns__vbuf_append(vb,qbuf,strlen(qbuf)))
  36       return adns_s_nolocalmem;
  37     buf+= i; len-= i;
  38   }
  39 }
  40
  41 static adns_status get_domain_perm(adns_state ads, adns_query qu, int serv,
  42                                    const byte *dgram, int dglen,
  43                                    int *cbyte_io, int max, char **domain_r) {
  44   /* Returns 0     for OK (*domain_r set) or truncated (*domain_r null)
  45    *      or any other adns_s_* value.
  46    */
  47   int cbyte, sused, lablen;
  48
  49   /* If we follow a pointer we set cbyte_io to 0 to indicate that
  50    * we've lost our original starting and ending points; we don't
  51    * put the end of the pointed-to thing into the original *cbyte_io.
  52    */
  53   cbyte= *cbyte_io;
  54   sused= qu->ans.used;
  55   *domain_r= 0;
  56   for (;;) {
  57     if (cbyte>=max) goto x_truncated;
  58     lablen= GET_B(cbyte);
  59     if (!lablen) break;
  60     if (lablen&0x0c000) {
  61       if ((lablen&0x0c000) != 0x0c0000) return adns_s_unknownreply;
  62       if (cbyte_io) { *cbyte_io= cbyte; cbyte_io= 0; }
  63       cbyte= (lablen&0x3fff) + DNS_HDR_SIZE;
  64       max= dglen;
  65       continue;
  66     }
  67     if (cbyte+lablen>=max) bgoto x_truncated;
  68     if (qu->ans.used != sused)
  69       if (!adns__vbuf_append(&qu->ans,".",1)) return adns_s_nolocalmem;
  70     if (qu->flags & adns_qf_anyquote) {
  71       if (!vbuf__append_quoted1035(&qu->ans,dgram+cbyte,lablen))
  72         return adns_s_nolocalmem;
  73     } else {
  74       if (!ctype_isalpha(dgram[cbyte])) return adns_s_invaliddomain;
  75       for (i= cbyte+1; i<cbyte+lablen; i++) {
  76         ch= dgram[cbyte];
  77         if (ch != '-' && !ctype_isalpha(ch) && !ctype_isdigit(ch))
  78           return adns_s_invaliddomain;
  79       }
  80       if (!adns__vbuf_append(&qu->ans,dgram+cbyte,lablen))
  81         return adns_s_nolocalmem;
  82     }
  83   }
  84   if (cbyte_io) *cbyte_io= cbyte;
  85   if (!adns__vbuf_append(&qu->ans,"",1)) return adns_s_nolocalmem;
  86   *domain_r= qu->ans.buf+sused;
  87   return adns_s_ok;
  88
  89  x_truncated:
  90   return cbyte_io ? -1 : adns_s_serverfaulty;
  91 }
  92
  93 static adns_status get_domain_temp(adns_state ads, adns_query qu, int serv,
  94                                    const byte *dgram, int dglen,
  95                                    int *cbyte_io, int max, char **domain_r) {
  96   int sused;
  97   adns_status st;
  98
  99   sused= qu->ans.used;
 100   st= get_domain_perm(ads,qu,serv,dgram,dglen,cbyte_io,max,domain_r);
 101   qu->ans.used= sused;
 102   return st;
 103 }
 104
 105 /* fixme: sensible comparison of owners */
 106
 107 static adns_status get_rr_temp(adns_state ads, adns_query qu, int serv,
 108                                const byte *dgram, int dglen,
 109                                int *cbyte_io,
 110                                int *type_r, int *class_r, int *rdlen_r, int *rdstart_r,
 111                                char **owner_r) {
 112   int cbyte, tmp, rdlen;
 113
 114   cbyte= *cbyte_io;
 115   st= get_domain_temp(ads,qu,serv,dgram,dglen,&cbyte,dglen,owner_r);
 116   if (st) return st;
 117
 118   if (cbyte+10>len) goto x_truncated;
 119   GET_W(cbyte,tmp); if (type_r) *type_r= tmp;
 120   GET_W(cbyte,tmp); if (class_r) *class_r= tmp;
 121   cbyte+= 4; /* we skip the TTL */
 122   GET_W(cbyte,rdlen); if (rdlen_r) *rdlen_r= tmp;
 123   if (rdstart_r) *rdstart_r= cbyte;
 124   cbyte+= rdlen;
 125   if (cbyte>dglen) goto x_truncated;
 126   *cbyte_io= cbyte;
 127   return adns_s_ok;
 128
 129  x_truncated:
 130   *owner_r= 0; return 0;;
 131 }
 132
 133 void adns__procdgram(adns_state ads, const byte *dgram, int dglen, int serv) {
 134   int cbyte, anstart, rrstart, lablen, wantedrrs, get_t;
 135
 136   cbyte= 0;
 137
 138   if (dglen<DNS_HDR_SIZE) {
 139     adns__diag(ads,serv,"received datagram too short for message header (%d)",len);
 140     return;
 141   }
 142   GET_W(cbyte,id);
 143   GET_B(cbyte,f1);
 144   GET_B(cbyte,f2);
 145   GET_W(cbyte,qdcount);
 146   GET_W(cbyte,ancount);
 147   GET_W(cbyte,nscount);
 148   GET_W(cbyte,arcount);
 149   assert(cbyte == DNS_HDR_SIZE);
 150
 151   if (f1&0x80) {
 152     adns__diag(ads,serv,"server sent us a query, not a response");
 153     return;
 154   }
 155   if (f1&0x70) {
 156     adns__diag(ads,serv,"server sent us unknown opcode %d (wanted 0=QUERY)",
 157                (f1>>4)&0x70);
 158     return;
 159   }
 160   if (!qdcount) {
 161     adns__diag(ads,serv,"server sent reply without quoting our question");
 162     return;
 163   } else if (qdcount>1) {
 164     adns__diag(ads,serv,"server claimed to answer %d questions with one message",
 165                qdcount);
 166     return;
 167   }
 168   for (qu= ads->timew; qu= nqu; qu++) {
 169     nqu= qu->next;
 170     if (qu->id != id) continue;
 171     if (len < qu->querylen) continue;
 172     if (memcmp(qu->querymsg+DNSHDRSIZE,dgram+DNSHDRSIZE,qu->querylen-DNSHDRSIZE))
 173       continue;
 174     break;
 175   }
 176   anstart= qu->querylen;
 177   if (!qu) {
 178     adns__debug(ads,serv,"reply not found (id=%02x)",id);
 179     return;
 180   }
 181   if (!(f1&0x01)) {
 182     adns__diag(ads,serv,"server thinks we didn't ask for recursive lookup");
 183     adns__query_fail(ads,qu,adns_s_serverfaulty);
 184     return;
 185   }
 186
 187   rcode= (f1&0x0f);
 188   switch (rcode) {
 189   case rcode_noerror:
 190   case rcode_nxdomain:
 191     break;
 192   case rcode_formaterror:
 193     adns__warn(ads,serv,"server cannot understand our query (Format Error)");
 194     adns__query_fail(ads,qu,adns_s_serverfaulty);
 195     return;
 196   case rcode_servfail;
 197     adns__query_fail(ads,qu,adns_s_serverfailure);
 198     return;
 199   case rcode_notimp:
 200     adns__warn(ads,serv,"server claims not to implement our query");
 201     adns__query_fail(ads,qu,adns_s_notimplemented);
 202     return;
 203   case rcode_refused:
 204     adns__warn(ads,serv,"server refused our query");
 205     adns__query_fail(ads,qu,adns_s_refused);
 206     return;
 207   default:
 208     adns__warn(ads,serv,"server gave unknown response code %d",rcode);
 209     adns__query_fail(ads,qu,adns_s_reasonunknown);
 210     return;
 211   }
 212
 213   /* Now, take a look at the answer section, and see if it is complete.
 214    * If it has any CNAMEs we stuff them in the answer.
 215    */
 216   wantedrrs= 0;
 217   for (rri= 0; rri<ancount; rri++) {
 218     rrstart= cbyte;
 219     st= get_rr_temp(ads,qu,serv,
 220                     dgram,dglen,
 221                     &cbyte,
 222                     &rrtype,&rrclass,&rdlength,&cowner);
 223     if (st) adns__query_fail(ads,qu,st);
 224     if (rrclass != DNS_CLASS_IN) {
 225       adns__diag(ads,serv,"ignoring RR with wrong class %d (expected IN=%d)",
 226                  rrclass,DNS_CLASS_IN);
 227       continue;
 228     }
 229     if (strcmp_quoted1035(cowner, qu->cname ? qu->cname : qu->owner)) {
 230       adns__debug(ads,serv,"ignoring answer RR with irrelevant owner \"%s\"",cowner);
 231       continue;
 232     }
 233     if (!qu->cname &&
 234         (qu->type & adns__rrt_typemask) != adns_cname &&
 235         rrtype == adns_cname) { /* Ignore second and subsequent CNAMEs */
 236       qu->cname= get_domain_perm(ads,qu,dgram,len,rdstart,rdstart+rdlength);
 237         /* If we find the answer section truncated after this point we restart
 238          * the query at the CNAME; otherwise we can use it as-is.
 239          */
 240     } else if (rrtype == (qu->type & adns__rrt_typemask)) {
 241       wantedrrs++;
 242     } else {
 243       adns__debug(ads,serv,"ignoring answer RR with irrelevant type %d",rrtype);
 244     }
 245   }
 246
 247   /* If we got here then the answer section is intact. */
 248   nsstart= cbyte;
 249
 250   if (!wantedrrs) {
 251     /* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
 252
 253     if (rcode == rcode_nxdomain) {
 254       adnns__query_finish(ads,qu,adns_s_nxdomain);
 255       return;
 256     }
 257
 258     /* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
 259     for (rri= 0; rri<nscount; rri++) {
 260
 261     }
 262     } else {
 263
 264
 265   if (!(f2&0x80)) {
 266     adns__diag(ads,serv,"server is not willing to do recursive lookups for us");
 267     adns__query_fail(ads,qu,adns_s_norecurse);
 268     return;
 269   }
 270
 271
 272         ) {
 273     if (type
 274       if (cbyte+lab
 275       if (anstart > dgend) { truncated(ads,qu,f1); return; }
 276   }
 277     for
 278
 279     /* Look for CNAMEs in the answer section */
 280
 281   }
 282
 283
 284     adns__diag(ads,serv,"server refused our query");
 285
 286     case rcode_
 287
 288   case 0: /* NOERROR
 289     break;
 290   case 1: /* Format error */
 291   case 3: /* Name Error */
 292
 293   qr= f1&0x80;
 294
 295
 296   adns__diag(ads,serv,"received datagram size %d",len);
 297
 298 }