IrisCTF 2025 - "Shake My Hand" Writeup & Walkthrough

This is an interactive Python writeup and walkthrough for the "Shake My Hand" 2025 Iris CTF challenge.

Features

• Step-by-step TCP handshake demonstration
• Real-time packet crafting and analysis with Scapy
• ASCII art interface

Requirements

• Python 3.x
• Scapy library (pip install scapy)
• Windows/Linux compatible

Install/run with PIP

1. Install with "pip install shakemyhand-walkthrough"
2. Enter "shakemyhand-walkthrough" at terminal.

Manual install/run

Download shakemyhand-walkthrough.py, make sure you have scapy installed (pip install scapy) and run the file with "python ./shakemyhand-walkthrough.py"

Additional Information

This program uses built-in Scapy modules and functions to craft and manipulate network packets:

• IP: Used to create and configure the IP headers of the packets.
• TCP: Used to create and configure the TCP headers of the packets.
• Raw: Used to add raw payload data to the packets.
• raw: Converts crafted packets into raw bytes for transmission.
• base64: Encodes raw bytes into a base64 string.

You can learn more about how this program utilizes Scapy to solve the challenge by refering to the following functions in the code:

• create_syn: Crafts a SYN packet to initiate the TCP handshake.
• create_ack: Creates an ACK packet to acknowledge the server's SYN-ACK.
• create_response: Sends a PSH+ACK packet with data.
• decode_and_show: Decodes a base64 packet and logs details about IP/TCP layers, sequence/ack numbers, flags, and payload.

See code comments for additional information on script functionality.