/* * Copyright (c) 2017, Matias Fontanini * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following disclaimer * in the documentation and/or other materials provided with the * distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * */ #include #include using std::cout; using std::endl; using namespace Tins; PacketSender sender; bool callback(const PDU& pdu) { // The packet probably looks like this: // // EthernetII / IP / UDP / RawPDU // // So we retrieve each layer, and construct a // DNS PDU from the RawPDU layer contents. EthernetII eth = pdu.rfind_pdu(); IP ip = eth.rfind_pdu(); UDP udp = ip.rfind_pdu(); DNS dns = udp.rfind_pdu().to(); // Is it a DNS query? if (dns.type() == DNS::QUERY) { // Let's see if there's any query for an "A" record. for (const auto& query : dns.queries()) { if (query.query_type() == DNS::A) { // Here's one! Let's add an answer. dns.add_answer( DNS::resource( query.dname(), "127.0.0.1", DNS::A, query.query_class(), // 777 is just a random TTL 777 ) ); } } // Have we added some answers? if (dns.answers_count() > 0) { // It's a response now dns.type(DNS::RESPONSE); // Recursion is available(just in case) dns.recursion_available(1); // Build our packet auto pkt = EthernetII(eth.src_addr(), eth.dst_addr()) / IP(ip.src_addr(), ip.dst_addr()) / UDP(udp.sport(), udp.dport()) / dns; // Send it! sender.send(pkt); } } return true; } int main(int argc, char* argv[]) { if(argc != 2) { cout << "Usage: " <<* argv << " " << endl; return 1; } // Sniff on the provided interface in promiscuous mode SnifferConfiguration config; config.set_promisc_mode(true); // Use immediate mode so we get the packets as fast as we can config.set_immediate_mode(true); // Only capture udp packets sent to port 53 config.set_filter("udp and dst port 53"); Sniffer sniffer(argv[1], config); // All packets will be sent through the provided interface sender.default_interface(argv[1]); // Start the capture sniffer.sniff_loop(callback); }