Project Walkthrough

Prerequisites

In the machine tested, I used the built in wireless adapter and connected to internet through Ethernet

System Setup

Install mitmproxy

Get instruction from their site

Setup ip forwarding

The below commands assumes you're running as root:

sysctl -w net.ipv4.ip_forward=1

Setup routing using IPtables

As for my machine, my wireless adapter is named wlp3s0. Make sure that the port you will be using for mitmproxy matches the --dport option (destination port). Again, root privileges required

iptables -t nat -A PREROUTING -i wlp3s0 -p tcp --dport 80 -J REDIRECT --to-port 8080

Executing Man in the middle attack

Real execution

mitmdump -T -p 8080 -s "inject.py test.js" "~t 'text/html' ~s ~c 200"

mitmdump does what mitmproxy but in an automated way. mitmproxy allows interception but manually, hence, Testing section is for learning.

Testing (optional, if you want to know whats happening)

Run mitmproxy -T -p 8080 . The port should match the iptables destination port.

Try a site like httpbin.org. You should now be able to see traffic in the screen. Press ? for instructions.

To intercept, press i. Set the following filters:

Intercept filter: ~t "text/html" ~s ~c 200