denyhosts/clamscan/freshclam/dns.c

164 lines
4.3 KiB
C

/*
* Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
* Copyright (C) 2007-2013 Sourcefire, Inc.
* Copyright (C) 2004-2007 Tomasz Kojm <tkojm@clamav.net>2004 Tomasz Kojm <tkojm@clamav.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdio.h>
#include "dns.h"
#ifdef HAVE_RESOLV_H
#include <string.h>
#include <sys/types.h>
#ifndef _WIN32
#include <netinet/in.h>
#include <arpa/nameser.h>
#endif
#include <resolv.h>
#include "output.h"
#ifndef PACKETSZ
#define PACKETSZ 512
#endif
char *
dnsquery(const char *domain, int qtype, unsigned int *ttl)
{
unsigned char answer[PACKETSZ], *answend, *pt;
char *txt, host[128];
int len, type;
unsigned int cttl, size, txtlen = 0;
if (ttl)
*ttl = 0;
if (res_init() < 0) {
logg("^res_init failed\n");
return NULL;
}
logg("*Querying %s\n", domain);
memset(answer, 0, PACKETSZ);
if ((len = res_query(domain, C_IN, qtype, answer, PACKETSZ)) < 0 || len > PACKETSZ) {
#ifdef FRESHCLAM_DNS_FIX
/* The DNS server in the SpeedTouch Alcatel 510 modem can't
* handle a TXT-query, but it can resolve an ANY-query to a
* TXT-record, so we try an ANY-query now. The thing we try
* to resolve normally only has a TXT-record anyway.
*/
memset(answer, 0, PACKETSZ);
if (qtype == T_TXT)
qtype = T_ANY;
if ((len = res_query(domain, C_IN, qtype, answer, PACKETSZ)) < 0) {
logg("%cCan't query %s\n",
(qtype == T_TXT || qtype == T_ANY) ? '^' : '*', domain);
return NULL;
}
#else
logg("%cCan't query %s\n", (qtype == T_TXT) ? '^' : '*', domain);
return NULL;
#endif
}
if (qtype != T_TXT && qtype != T_ANY) {
if (ttl)
*ttl = 2;
return NULL;
}
answend = answer + len;
pt = answer + sizeof(HEADER);
if ((len = dn_expand(answer, answend, pt, host, sizeof(host))) < 0) {
logg("^dn_expand failed\n");
return NULL;
}
pt += len;
if (pt > answend - 4) {
logg("^Bad (too short) DNS reply\n");
return NULL;
}
GETSHORT(type, pt);
if (type != qtype) {
logg("^Broken DNS reply.\n");
return NULL;
}
pt += INT16SZ; /* class */
size = 0;
do { /* recurse through CNAME rr's */
pt += size;
if ((len = dn_expand(answer, answend, pt, host, sizeof(host))) < 0) {
logg("^second dn_expand failed\n");
return NULL;
}
pt += len;
if (pt > answend - 10) {
logg("^Bad (too short) DNS reply\n");
return NULL;
}
GETSHORT(type, pt);
pt += INT16SZ; /* class */
GETLONG(cttl, pt);
GETSHORT(size, pt);
if (pt + size < answer || pt + size > answend) {
logg("^DNS rr overflow\n");
return NULL;
}
} while (type == T_CNAME);
if (type != T_TXT) {
logg("^Not a TXT record\n");
return NULL;
}
if (!size || (txtlen = *pt) >= size || !txtlen) {
logg("^Broken TXT record (txtlen = %d, size = %d)\n", txtlen, size);
return NULL;
}
if (!(txt = (char *)malloc(txtlen + 1)))
return NULL;
memcpy(txt, pt + 1, txtlen);
txt[txtlen] = 0;
if (ttl)
*ttl = cttl;
return txt;
}
#else
char *
dnsquery(const char *domain, int qtype, unsigned int *ttl)
{
if (ttl)
*ttl = 1; /* ttl of 1 combined with a NULL return distinguishes a failed lookup from DNS queries not being available */
return NULL;
}
#endif