Network Tunneling with Chisel: Security and Practical Examples

Introduction

In today’s complex network structure, secure and flexible access has become more important than ever. Chisel is a powerful tool that responds to this need with its TCP/UDP tunneling capabilities. In this article, we will present some practical examples of how Chisel can be used.

Basic Features of Chisel:

Chisel is an open-source tool developed using the Go language. It can operate in both client and server modes and provides secure connections with SSL/TLS encryption. Here are some of Chisel’s notable features:

• Reverse Connection Tunnels
• Multiple Tunnel Support
• SSL/TLS Encryption
• Simple Command Line Interface
• Cross-Platform Compatibility

Advanced Usage Scenario: Bypassing Firewalls and Conducting Covert Scanning

In this scenario, we will use Chisel to bypass a firewall and perform covert scanning on the target network.

Help Menu

┌──(root㉿denizhalil)-[/home/denizhalil]
└─$ chisel --help       

  Usage: chisel [command] [--help]

  Version: 1.9.1-0kali1 (go1.21.3)

  Commands:
    server - runs chisel in server mode
    client - runs chisel in client mode

  Read more:
    https://github.com/jpillora/chisel

Step 1: Setting Up Chisel Server on the Main Machine

On the main machine, start the Chisel server by running the following command:

$ chisel server -p 8000 --reverse

This command starts a Chisel server that listens on port 8000 and accepts reverse connections.

Step 2: Setting Up Chisel Client on the Target Machine

On the target machine, start the Chisel client with the following command:

$ chisel client <SERVER IP>:8000 R:socks

This command creates a SOCKS proxy tunnel from the target machine to the main machine.

Step 3: Configuring Proxy Settings

On the main machine, go to the bottom of the /etc/proxychains.conf file and edit it. The content of the file should be as follows:

[ProxyList]
socks4  127.0.0.1 1080 # you should change here 

This setting specifies a SOCKS4 proxy on the local machine on port 1080.

Step 4: Conducting Covert Scanning

Now, you can perform covert scanning using proxychains. For example, to scan a website, you can use the following command:

$ proxychains nmap -sT -p 80 <TARGET IP>

This command uses the nmap tool to scan port 80 on the target IP address, directing all traffic through Chisel.

Conclusion:

Chisel is a powerful and flexible solution for secure network tunneling. Whether for corporate access, remote work, or educational purposes, it is a valuable tool in various scenarios. However, it is important to remember that the use of Chisel should be within ethical standards and legal limits. Necessary permissions should be obtained before intervening in any network.