Decryption Conniption: How to Hack a Hard Forensics CTF Challenge

By /

Listen to this Post

Featured Image

Introduction

In the recent Correlation One CTF hosted with the United States Department of Defense, only three participants out of 2,000 successfully solved the Hard Forensics Challenge. The task involved memory dump analysis, TLS decryption, and extracting a password from a cleartext VNC session to decrypt a 7z file. This article breaks down the key techniques used, providing actionable commands and methodologies for cybersecurity professionals.

Learning Objectives

  • Extract SSL keys from a memory dump to decrypt TLS traffic.
  • Analyze PCAP files to identify cleartext credentials.
  • Decrypt encrypted archives using recovered passwords.

You Should Know

1. Carving SSL Keys from Memory Dumps

Command:

strings memory.dmp | grep -A 50 -B 50 "SSLKEYLOGFILE" > extracted_keys.log

Step-by-Step Guide:

  1. Use the `strings` command to extract human-readable data from the memory dump.
  2. Filter for `SSLKEYLOGFILE` entries, which contain TLS session keys.
  3. Save the output to a file for use with Wireshark or other decryption tools.

2. Decrypting TLS Traffic in Wireshark

Configuration Steps:

1. Open Wireshark and load the PCAP file.

  1. Navigate to Edit → Preferences → Protocols → TLS.
  2. Under Pre-Master-Secret log filename, point to the extracted extracted_keys.log.

4. Wireshark will now decrypt TLS traffic automatically.

3. Extracting Passwords from Cleartext VNC Sessions

Command (Using Tshark):

tshark -r traffic.pcap -Y "vnc" -T fields -e vnc.auth.password

Step-by-Step Guide:

1. Analyze the decrypted PCAP for VNC traffic.

  1. Use Tshark to filter VNC packets and extract authentication credentials.
  2. The password can then be used to decrypt the 7z archive.

4. Decrypting 7z Archives with Recovered Passwords

Command:

7z x flag.7z -p"ExtractedPassword"

Step-by-Step Guide:

  1. Once the password is obtained from VNC traffic, use it to extract the 7z file.
  2. The flag or sensitive data should now be accessible.
    1. Analyzing Memory Dumps with Volatility (Alternative Approach)

Command:

volatility -f memory.dmp --profile=Win10x64_19041 pslist

Step-by-Step Guide:

1. Identify running processes (e.g., `tvnserver` for VNC).

  1. Extract process memory to hunt for credentials or keys.
  2. Use plugins like `mimikatz` or `hashdump` if necessary.

What Undercode Say

  • Key Takeaway 1: Memory forensics is a powerful tool for recovering encryption keys and credentials.
  • Key Takeaway 2: Cleartext protocols (like VNC) remain a critical weak point in secure environments.

Analysis:

This challenge highlights the importance of memory analysis in incident response. Attackers often leave critical data (like SSL keys) in memory, and defenders must be proficient in extracting them. Additionally, unencrypted protocols like VNC should be avoided in favor of secure alternatives.

Prediction

As CTFs and real-world attacks evolve, memory forensics and TLS decryption will become even more critical. Organizations must train their teams in advanced forensic techniques to stay ahead of adversaries. Automated tools for memory analysis (like MemProcFS) will likely see increased adoption.

Would you like a deeper dive into any of these techniques? Let us know in the comments!

IT/Security Reporter URL:

Reported By: Christopher Haller – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

Join Our Cyber World:

💬 Whatsapp | 💬 Telegram

Related Posts: