Man-In-The-Middle

SNIFFlab – Create Your Own MITM Test Environment

Essentially it’s a WiFi hotspot that is continually collecting all the packets transmitted across it. All connected clients’ HTTPS communications are subjected to a “Man-in-the-middle” attack, whereby they can later be decrypted for analysis

What is SNIFFLab MITM Test Environment

In our environment, dubbed Snifflab, a researcher simply connects to the Snifflab WiFi network, is prompted to install a custom certificate authority on the device, and then can use their device as needed for the test.

All traffic on the network is logged by a Raspberry Pi dedicated to that task. The traffic is cloned by a Great Scott Gadgets Throwing Star LAN Tap, which routes it both to its destination, and to our Raspberry Pi. The Pi continually collects packet data, creating new packet capture (pcap) files at a regular interval, or once the active file reaches a configurable size. Saved files are regularly transferred to another machine for persistent storage. Users with SSH access to the Pi can also manually restart the pcap service, to get instant access to the captured packets, instead of waiting for the interval.

The custom certificate that each client must install enables the proxy server through which SNIFFlab routes its traffic to intercept HTTPS requests to the outside world, and re-encrypt them using certificates generated on-the-fly. This allows for the researcher to later decrypt most captured network traffic sent over HTTPS.

 

Using SNIFFLab MITM Enivronment

sniffer.py command line arguments

-i (specify the network interface)
-s (specify the file size limit)
-t (specify the time interval, in seconds, between new PCAP files)
-f (specify a filename suffix to append to each PCAP.
-u (specify a ssh username for a remote backup)
-h (specify a ssh host for remote backup)
-p (specify the path on the remote host for backup)

Firewall rules on DD-WRT router to send traffic to MITM proxy box

Make sure the network interface (vlan1 here) is correct.

PROXYIP=your.proxy.ip
iptables -t mangle -A PREROUTING -j ACCEPT -p tcp -m multiport --dports 80,443 -s $PROXYIP
iptables -t mangle -A PREROUTING -j MARK --set-mark 3 -p tcp -m multiport --dports 80,443
ip rule add fwmark 3 table 2
ip route add default via $PROXYIP dev vlan1 table 2

PCAP machine scripts

/etc/network/interfaces

auto lo

iface lo inet loopback

iface eth0 inet manual

iface eth1 inet manual

allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp

auto bond0
iface bond0 inet dhcp
bond-mode 3
bond-miimon 100
slaves eth0 eth1

/etc/wpa_supplicant/wpa_supplicant.conf

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
        ssid=""
        psk=hashofyourpassword
        proto=RSN
        key_mgmt=WPA-PSK
        pairwise=TKIP
        auth_alg=OPEN
}

Getting the network running correctly on boot

/etc/init.d/network.sh

#!/bin/sh
### BEGIN INIT INFO
# Provides:		network.sh
# Short-Description:	Ensure WiFi as well as Ethernet interfaces are up
# Description:
# Default-Start:	2 3 4 5
# Default-Stop:		0 1 6
# Required-Start:	$remote_fs $syslog
# Required-Stop:	$remote_fs $syslog
### END INIT INFO
sudo ifplugd eth0 --kill
sudo ifup wlan0
sudo ifup eth0
sudo ifup eth1
sudo ifconfig eth1 promisc
sudo ifconfig eth0 promisc
exit 0

Start capturing packets on startup — create a sniffer service

/etc/init/sniffer.conf

#sniffer.conf
start on runlevel [2345]
stop on runlevel [016]

script
	cd /home/pi/snifflab
	exec python sniffer.py -i bond0 -s 100 -t 1200
end script

MITM proxy service

mitm.conf

start on filesystem

script
	sudo iptables -A PREROUTING -t nat -i em1 -p tcp -m multiport --dports 80,443 -j REDIRECT --to-port 4567
	SSLKEYLOGFILE=/var/log/mitmkeys.log
	export SSLKEYLOGFILE
	echo "MITM Keys being logged here: $SSLKEYLOGFILE"
	exec mitmdump -T --host --conf=/etc/mitmproxy/common.conf
end script

Script to backup pcaps to local machine

#!/bin/bash
remote_server=yourservername
pcap_dir=/pcaps
keylogfile=/var/log/mitmkeys.log
local_dir=~/Documents/snifflab

rsync -a "$remote_server":$pcap_dir $local_dir
scp "$remote_server":$keylogfile $local_dir

Download SNIFFLab

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Icarus

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