Proxies
A proxy is when a device or service sits in the middle of a connection and acts as a mediator.
- HTTP Proxies: BurpSuite
- Postman, mitm_relay
- SOCKS/SSH Proxy (for pivoting): Chisel, ptunnel, sshuttle.
There are many types of proxy services, but the key ones are:
- Dedicated Proxy
/Forward Proxy: The Forward Proxy, is what most people imagine a proxy to be. A Forward Proxy is when a client makes a request to a computer, and that computer carries out the request. For example, in a corporate network, sensitive computers may not have direct access to the Internet. To access a website, they must go through a proxy (or web filter). - Reverse Proxy: As you may have guessed, a reverse proxy, is the reverse of a Forward Proxy. Instead of being designed to filter outgoing requests, it filters incoming ones. The most common goal with a Reverse Proxy, is to listen on an address and forward it to a closed-off network. Many organizations use CloudFlare as they have a robust network that can withstand most DDOS Attacks.
- Transparent Proxy
Setting up Postman with BurpSuite
1 - Postman > Settings
2 - Proxy tab. Check:
- Use the system proxy
- Add a custom proxy configuration
- HTTP
- HTTPS
- 127.0.0.1
- 8080
3 - BurpSuite. Settup proxy listener
4 - Burp Suite. Intercept mode on
5 - Postman. Send the interesting request from your collection
6 - Your BurpSuite will intercept that traffic. Now you can send it to Intruder, Repeater, Sequencer...
Setting up mitm_relay with Burpsuite
In DVTA we will configure the server to the IP of the local machine. In my lab set up my IP was 10.0.2.15.
In FTP, we will configure the listening port to 2111. Also we will disable IP check for this lab setup to work.
From https://github.com/jrmdev/mitm_relay:
This is what we're doing:
1. DVTA application sends traffic to port 21, so to intercept it we configure MITM_relay to be listening on port 21.
2. mitm_relay encapsulates the application traffic )no matter the protocol, into HTTP protocol so BurpSuite can read it
3. Burp Suite will read the traffic. And we can tamper here our code.
4. mitm_relay will "unfunnel" the traffic from the HTPP protocol into the raw one
5. In a lab setup FTP server will be in the same network, so to not get in conflict with mitm_relay we will modify FTP listen port to 2111. In real life this change is not necessary
Running mitm_relay:
python mitm_relay.py -l 0.0.0.0 -r tcp:21:10.0.2.15:2111 -p 127.0.0.1:8080
# -l listening address for mitm_relay (0.0.0.0 means we all listening in all interfaces)
# -r relay configuration: <protocol>:<listeningPort>:<IPofDestinationserver>:<listeningPortonDestinationServer>
# -p Proxy configuration: <IPofProxy>:<portOfProxy>
And this is how the interception looks like:
