SSL Cracking: Can Cain&Able Help?

TL;DR

Cain&Able can assist in cracking SSL/TLS sessions, but it doesn’t do the heavy lifting itself. It primarily focuses on capturing handshakes and then relies on other tools (like John the Ripper or Hashcat) to attempt decryption if weak ciphers are used. Modern SSL configurations are very secure against Cain&Able alone.

Understanding the Process

SSL/TLS encryption protects data transmitted between a client (your browser) and a server. Cain&Able doesn’t ‘break’ this encryption directly. Instead, it tries to exploit weaknesses in how the connection is established – specifically during the handshake process.

Steps to Attempt SSL Cracking with Cain&Able

1. Capture Network Traffic: Cain&Able excels at capturing network packets. You need to be on the same local network as the target you’re trying to intercept.
   • Start Cain&Able and select your network adapter.
   • Go to ‘Sniffer’ tab, choose the correct interface, and start sniffing traffic.
2. Filter for SSL/TLS Traffic: Focus on connections using SSL/TLS.
   • In the Sniffer tab, apply a filter like ssl or tls in the ‘Filters’ section. This will show only encrypted sessions.
3. Identify Target Sessions: Locate the specific SSL/TLS session you want to try and crack.
   • Look for connections with recognizable server names (e.g., your bank, email provider).
   • The ‘Session’ tab will show details of each captured connection.
4. Attempt Handshake Decryption: Cain&Able can attempt to extract the handshake information.
   • Right-click on the target session and select ‘SSL/TLS Decode’.
   • Cain&Able will try to decode the handshake, looking for weak ciphers or exportable keys. This step often fails with modern configurations.
5. Export Handshake Data: If Cain&Able successfully extracts any data, you need to export it.
   • Right-click on the session and select ‘Save Session’. Choose a suitable format (e.g., PCAP for later analysis).
6. Crack with External Tools: This is where other tools come in.
   • John the Ripper/Hashcat: Use these password cracking tools to attempt decrypting any extracted keys or hashes. The exact commands depend on the format of the exported data and the cipher used.

Example using John the Ripper (after exporting a handshake file)

john --format=ssl handshake.pcap

Important Considerations & Limitations

• Modern SSL/TLS is Strong: Current SSL/TLS configurations use strong ciphers and Perfect Forward Secrecy (PFS), making cracking extremely difficult or impossible with Cain&Able alone.
• Man-in-the-Middle Attacks: Successful SSL cracking usually requires a Man-in-the-Middle (MITM) attack, which is illegal without permission. Cain&Able can help facilitate MITM attacks but doesn’t perform them automatically.
• Export Control: Exporting and attempting to crack SSL keys may be illegal in your jurisdiction.
• Weak Ciphers: Cain&Able is most effective against older systems using weak ciphers (e.g., DES, RC4). These are rarely used today.
• Certificate Warnings: Users often get warnings if a certificate isn’t trusted, preventing successful MITM attacks.

Alternatives

Tools like Wireshark (for packet capture and analysis) and specialized SSL/TLS testing tools are more effective for identifying vulnerabilities in SSL/TLS configurations than Cain&Able.