1#!/usr/bin/env python 2# - 3# SPDX-License-Identifier: BSD-2-Clause 4# 5# Copyright (c) 2020 Alexander V. Chernikov 6# 7# Redistribution and use in source and binary forms, with or without 8# modification, are permitted provided that the following conditions 9# are met: 10# 1. Redistributions of source code must retain the above copyright 11# notice, this list of conditions and the following disclaimer. 12# 2. Redistributions in binary form must reproduce the above copyright 13# notice, this list of conditions and the following disclaimer in the 14# documentation and/or other materials provided with the distribution. 15# 16# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26# SUCH DAMAGE. 27# 28# $FreeBSD$ 29# 30 31import argparse 32import logging 33logging.getLogger("scapy").setLevel(logging.CRITICAL) 34import scapy.all as sc 35import socket 36import sys 37import fcntl 38import struct 39 40 41def parse_args(): 42 parser = argparse.ArgumentParser(description='ICMP redirect generator') 43 parser.add_argument('--smac', type=str, required=True, 44 help='eth source mac') 45 parser.add_argument('--dmac', type=str, required=True, 46 help='eth dest mac') 47 parser.add_argument('--sip', type=str, required=True, 48 help='remote router source ip') 49 parser.add_argument('--dip', type=str, required=True, 50 help='local router ip') 51 parser.add_argument('--iface', type=str, required=True, 52 help='ifname to send packet to') 53 parser.add_argument('--route', type=str, required=True, 54 help='destination IP to redirect') 55 parser.add_argument('--gw', type=str, required=True, 56 help='redirect GW') 57 return parser.parse_args() 58 59 60def construct_icmp_redirect(smac, dmac, sip, dip, route_dst, route_gw): 61 e = sc.Ether(src=smac, dst=dmac) 62 l3 = sc.IP(src=sip, dst=dip) 63 icmp = sc.ICMP(type=5, code=1, gw=route_gw) 64 orig_ip = sc.IP(src=sip, dst=route_dst) 65 return e / l3 / icmp / orig_ip / sc.UDP() 66 67 68def send_packet(pkt, iface, feedback=False): 69 if feedback: 70 # Make kernel receive the packet as well 71 BIOCFEEDBACK = 0x8004427c 72 socket = sc.conf.L2socket(iface=args.iface) 73 fcntl.ioctl(socket.ins, BIOCFEEDBACK, struct.pack('I', 1)) 74 sc.sendp(pkt, socket=socket, verbose=True) 75 else: 76 sc.sendp(pkt, iface=iface, verbose=False) 77 78 79def main(): 80 args = parse_args() 81 pkt = construct_icmp_redirect(args.smac, args.dmac, args.sip, args.dip, 82 args.route, args.gw) 83 send_packet(pkt, args.iface) 84 85 86if __name__ == '__main__': 87 main() 88