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      1 /* Copyright 1998 by the Massachusetts Institute of Technology.
      2  *
      3  * Permission to use, copy, modify, and distribute this
      4  * software and its documentation for any purpose and without
      5  * fee is hereby granted, provided that the above copyright
      6  * notice appear in all copies and that both that copyright
      7  * notice and this permission notice appear in supporting
      8  * documentation, and that the name of M.I.T. not be used in
      9  * advertising or publicity pertaining to distribution of the
     10  * software without specific, written prior permission.
     11  * M.I.T. makes no representations about the suitability of
     12  * this software for any purpose.  It is provided "as is"
     13  * without express or implied warranty.
     14  */
     15 
     16 /*
     17  * ares_parse_ns_reply created by Vlad Dinulescu <vlad.dinulescu (at) avira.com>
     18  *      on behalf of AVIRA Gmbh - http://www.avira.com
     19  */
     20 
     21 #include "ares_setup.h"
     22 
     23 #ifdef HAVE_SYS_SOCKET_H
     24 #  include <sys/socket.h>
     25 #endif
     26 #ifdef HAVE_NETINET_IN_H
     27 #  include <netinet/in.h>
     28 #endif
     29 #ifdef HAVE_NETDB_H
     30 #  include <netdb.h>
     31 #endif
     32 #ifdef HAVE_ARPA_INET_H
     33 #  include <arpa/inet.h>
     34 #endif
     35 #ifdef HAVE_ARPA_NAMESER_H
     36 #  include <arpa/nameser.h>
     37 #else
     38 #  include "nameser.h"
     39 #endif
     40 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
     41 #  include <arpa/nameser_compat.h>
     42 #endif
     43 
     44 #include <stdlib.h>
     45 #include <string.h>
     46 #include "ares.h"
     47 #include "ares_dns.h"
     48 #include "ares_private.h"
     49 
     50 int ares_parse_ns_reply( const unsigned char* abuf, int alen,
     51                          struct hostent** host )
     52 {
     53   unsigned int qdcount, ancount;
     54   int status, i, rr_type, rr_class, rr_len;
     55   int nameservers_num;
     56   long len;
     57   const unsigned char *aptr;
     58   char* hostname, *rr_name, *rr_data, **nameservers;
     59   struct hostent *hostent;
     60 
     61   /* Set *host to NULL for all failure cases. */
     62   *host = NULL;
     63 
     64   /* Give up if abuf doesn't have room for a header. */
     65   if ( alen < HFIXEDSZ )
     66     return ARES_EBADRESP;
     67 
     68   /* Fetch the question and answer count from the header. */
     69   qdcount = DNS_HEADER_QDCOUNT( abuf );
     70   ancount = DNS_HEADER_ANCOUNT( abuf );
     71   if ( qdcount != 1 )
     72     return ARES_EBADRESP;
     73 
     74   /* Expand the name from the question, and skip past the question. */
     75   aptr = abuf + HFIXEDSZ;
     76   status = ares__expand_name_for_response( aptr, abuf, alen, &hostname, &len);
     77   if ( status != ARES_SUCCESS )
     78     return status;
     79   if ( aptr + len + QFIXEDSZ > abuf + alen )
     80   {
     81     free( hostname );
     82     return ARES_EBADRESP;
     83   }
     84   aptr += len + QFIXEDSZ;
     85 
     86   /* Allocate nameservers array; ancount gives an upper bound */
     87   nameservers = malloc( ( ancount + 1 ) * sizeof( char * ) );
     88   if ( !nameservers )
     89   {
     90     free( hostname );
     91     return ARES_ENOMEM;
     92   }
     93   nameservers_num = 0;
     94 
     95   /* Examine each answer resource record (RR) in turn. */
     96   for ( i = 0; i < ( int ) ancount; i++ )
     97   {
     98     /* Decode the RR up to the data field. */
     99     status = ares__expand_name_for_response( aptr, abuf, alen, &rr_name, &len );
    100     if ( status != ARES_SUCCESS )
    101       break;
    102     aptr += len;
    103     if ( aptr + RRFIXEDSZ > abuf + alen )
    104     {
    105       status = ARES_EBADRESP;
    106       free(rr_name);
    107       break;
    108     }
    109     rr_type = DNS_RR_TYPE( aptr );
    110     rr_class = DNS_RR_CLASS( aptr );
    111     rr_len = DNS_RR_LEN( aptr );
    112     aptr += RRFIXEDSZ;
    113 
    114     if ( rr_class == C_IN && rr_type == T_NS )
    115     {
    116       /* Decode the RR data and add it to the nameservers list */
    117       status = ares__expand_name_for_response( aptr, abuf, alen, &rr_data,
    118                                                &len);
    119       if ( status != ARES_SUCCESS )
    120       {
    121         free(rr_name);
    122         break;
    123       }
    124 
    125       nameservers[nameservers_num] = malloc(strlen(rr_data)+1);
    126 
    127       if (nameservers[nameservers_num]==NULL)
    128       {
    129         free(rr_name);
    130         free(rr_data);
    131         status=ARES_ENOMEM;
    132         break;
    133       }
    134       strcpy(nameservers[nameservers_num],rr_data);
    135       free(rr_data);
    136 
    137       nameservers_num++;
    138     }
    139 
    140     free( rr_name );
    141 
    142     aptr += rr_len;
    143     if ( aptr > abuf + alen )
    144     {
    145       status = ARES_EBADRESP;
    146       break;
    147     }
    148   }
    149 
    150   if ( status == ARES_SUCCESS && nameservers_num == 0 )
    151   {
    152     status = ARES_ENODATA;
    153   }
    154   if ( status == ARES_SUCCESS )
    155   {
    156     /* We got our answer.  Allocate memory to build the host entry. */
    157     nameservers[nameservers_num] = NULL;
    158     hostent = malloc( sizeof( struct hostent ) );
    159     if ( hostent )
    160     {
    161       hostent->h_addr_list = malloc( 1 * sizeof( char * ) );
    162       if ( hostent->h_addr_list )
    163       {
    164         /* Fill in the hostent and return successfully. */
    165         hostent->h_name = hostname;
    166         hostent->h_aliases = nameservers;
    167         hostent->h_addrtype = AF_INET;
    168         hostent->h_length = sizeof( struct in_addr );
    169         hostent->h_addr_list[0] = NULL;
    170         *host = hostent;
    171         return ARES_SUCCESS;
    172       }
    173       free( hostent );
    174     }
    175     status = ARES_ENOMEM;
    176   }
    177   for ( i = 0; i < nameservers_num; i++ )
    178     free( nameservers[i] );
    179   free( nameservers );
    180   free( hostname );
    181   return status;
    182 }
    183