libldap4/common/getdxbyname.c

/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#ifdef LDAP_DNS
/*
 *  Copyright (c) 1995 Regents of the University of Michigan.
 *  All rights reserved.
 *
 * getdxbyname - retrieve DX records from the DNS (from TXT records for now)
 */
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#ifdef MACOS
#include <stdlib.h>
#include "macos.h"
#endif /* MACOS */

#if !defined(MACOS) && !defined(DOS) && !defined( _WIN32 )
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <resolv.h>
#endif
#include "lber.h"
#include "ldap.h"
#include "ldap-private.h"
#include "ldap-int.h"

#if defined( DOS ) || defined( _WIN32 )
#include "msdos.h"
#endif /* DOS */


#ifdef NEEDPROTOS
static char ** decode_answer( unsigned char *answer, int len );
#else /* NEEDPROTOS */
static char **decode_answer();
#endif /* NEEDPROTOS */

extern int h_errno;
extern char *h_errlist[];


#define MAX_TO_SORT 32


/*
 * getdxbyname - lookup DNS DX records for domain and return an ordered
 *  array.
 */
char **
getdxbyname( char *domain )
{
    unsigned char   buf[ PACKETSZ ];
    char        **dxs;
    int         rc;

    Debug( LDAP_DEBUG_TRACE, "getdxbyname( %s )\n", domain, 0, 0 );

    memset( buf, 0, sizeof( buf ));

    if (( rc = res_search( domain, C_IN, T_TXT, buf, sizeof( buf ))) < 0
        || ( dxs = decode_answer( buf, rc )) == NULL ) {
    /*
     * punt:  return list conisting of the original domain name only
     */
    if (( dxs = (char **)malloc( 2 * sizeof( char * ))) == NULL ||
        ( dxs[ 0 ] = strdup( domain )) == NULL ) {
        if ( dxs != NULL ) {
        free( dxs );
        }
        dxs = NULL;
    } else {
        dxs[ 1 ] = NULL;
    }
    }

    return( dxs );
}


static char **
decode_answer( unsigned char *answer, int len )
{
    HEADER      *hp;
    char        buf[ 256 ], **dxs;
    unsigned char   *eom, *p;
    int         ancount, err, rc, type, class, dx_count, rr_len;
    int         dx_pref[ MAX_TO_SORT ];

    int  _getshort( unsigned char * );
#ifdef LDAP_DEBUG
    if ( ldap_debug & LDAP_DEBUG_PACKETS ) {
/*  __p_query( answer );    */
    }
#endif /* LDAP_DEBUG */

    dxs = NULL;
    hp = (HEADER *)answer;
    eom = answer + len;

    if ( ntohs( hp->qdcount ) != 1 ) {
    h_errno = NO_RECOVERY;
    return( NULL );
    }

    ancount = ntohs( hp->ancount );
    if ( ancount < 1 ) {
    h_errno = NO_DATA;
    return( NULL );
    }

    /*
     * skip over the query
     */
    p = answer + HFIXEDSZ;
    if (( rc = dn_expand( answer, eom, p, buf, sizeof( buf ))) < 0 ) {
    h_errno = NO_RECOVERY;
    return( NULL );
    }
    p += ( rc + QFIXEDSZ );

    /*
     * pull out the answers we are interested in
     */
    err = dx_count = 0;
    while ( ancount > 0 && err == 0 && p < eom ) {
    if (( rc = dn_expand( answer, eom, p, buf, sizeof( buf ))) < 0 ) {
        err = NO_RECOVERY;
        continue;
    }
    p += rc;    /* skip over name */
    type = _getshort( p );
    p += INT16SZ;
    class = _getshort( p );
    p += INT16SZ;
    p += INT32SZ;       /* skip over TTL */
    rr_len = _getshort( p );
    p += INT16SZ;
    if ( class == C_IN && type == T_TXT ) {
        int     i, n, pref, txt_len;
        char    *q, *r;

        q = (char *)p;
        while ( q < (char *)p + rr_len && err == 0 ) {
        if ( *q >= 3 && strncasecmp( q + 1, "dx:", 3 ) == 0 ) {
            txt_len = *q - 3;
            r = q + 4;
            while ( isspace( *r )) {
            ++r;
            --txt_len;
            }
            pref = 0;
            while ( isdigit( *r )) {
            pref *= 10;
            pref += ( *r - '0' );
            ++r;
            --txt_len;
            }
            if ( dx_count < MAX_TO_SORT - 1 ) {
            dx_pref[ dx_count ] = pref;
            }
            while ( isspace( *r )) {
            ++r;
            --txt_len;
            }
            if ( dx_count == 0 ) {
            dxs = (char **)malloc( 2 * sizeof( char * ));
            } else {
            dxs = (char **)realloc( dxs,
                ( dx_count + 2 ) * sizeof( char * ));
            }
            if ( dxs == NULL || ( dxs[ dx_count ] =
                (char *)calloc( 1, txt_len + 1 )) == NULL ) {
            err = NO_RECOVERY;
            continue;
            }
            memcpy( dxs[ dx_count ], r, txt_len );
            dxs[ ++dx_count ] = NULL;
        }
        q += ( *q + 1 );    /* move past last TXT record */
        }
    }
    p += rr_len;
    }

    if ( err == 0 ) {
    if ( dx_count == 0 ) {
        err = NO_DATA;
    } else {
        /*
         * sort records based on associated preference value
         */
        int     i, j, sort_count, tmp_pref;
        char    *tmp_dx;

        sort_count = ( dx_count < MAX_TO_SORT ) ? dx_count : MAX_TO_SORT;
        for ( i = 0; i < sort_count; ++i ) {
        for ( j = i + 1; j < sort_count; ++j ) {
            if ( dx_pref[ i ] > dx_pref[ j ] ) {
            tmp_pref = dx_pref[ i ];
            dx_pref[ i ] = dx_pref[ j ];
            dx_pref[ j ] = tmp_pref;
            tmp_dx = dxs[ i ];
            dxs[ i ] = dxs[ j ];
            dxs[ j ] = tmp_dx;
            }
        }
        }
    }
    }

    h_errno = err;
    return( dxs );
}

#endif /* LDAP_DNS */