To convert a PuTTY SSH private key to the PEM format, you can use the PuTTYgen tool that comes with PuTTY. PuTTYgen can convert keys between different formats, including PuTTY's own format (.ppk) and the PEM format.

PPK (PuTTY Private Key):

  • Associated Tool: PuTTY
  • Format: Proprietary binary format
  • Usage: PuTTY, a popular SSH and Telnet client for Windows, uses the PPK format for storing private keys.
  • Extension: .ppk
  • Conversion: PPK keys can be converted to other formats, such as PEM, using tools like PuTTYgen (part of the PuTTY suite).

PEM (Privacy Enhanced Mail):

  • Associated Tool: OpenSSL, OpenSSH, and many other SSH clients on Unix-like systems
  • Format: ASCII text (Base64-encoded)
  • Usage: The PEM format is widely used for storing private and public keys. It is a standard format that is not tied to a specific tool or platform.
  • Extension: .pem, .key, .pvt, .priv

Identification

1. Identify the file format

  • file PuTTY-User-Key-File.ppk

Exploitation

1. Convert the file from .ppk to pem

  • puttygen PuTTY-User-Key-File.ppk -O private-openssh -o pem_file.pem
  • file pemfile.pem

Note: you can use this private key to authenticate to different services in this case SSH

2. Assign proper permissions to the key

  • chmod 600 pem_file.pem
  • ls -l pem_file.pem

3. Use it as SSH key

  • ssh root@10.10.11.227 -i pem_file.pem

Note: Incase that it is password protected you can use ssh2john to brute force it