tpm-malcrypt

An example malicious payload controller and obfuscator assisted by TPM-protected keys.

malcrypter

This is the offline (server-side) component that generates the executed payload from the decrypter stub and your choice of encrypted payload.

Installation:

1. Grab PyDbg from: http://www.lfd.uci.edu/~gohlke/pythonlibs/
2. Within CMD: SET VS90COMNTOOLS=%VS120COMNTOOLS%
3. pip install pefile pycrypto

malcrypt

This is a Windows VS2013 solution containing two projects. The logic can be rewritten on OSX or Linux, depending on the intended target.

Part 1: tpm-keyextract

Detect a TPM on a client and create a new encryption keypair using standard protections. Return the public key component to be transmitted back to a encrypted PE generator.

Part 2: malcrypt

Using an input public key and input malicious payload, generate and return a self-decrypting PE that decrypts and executes in-memory.

Although the output PE can be executed on any machine, only a target machine will have the private key pair in it's crypto-store. Thus only a target machine will decrypt and executed the original input payload.

The malcrypt application involves several components and processes:

• Target OS crypto-store accesses.
• An in-memory decryption/execution stub.
• An encryptor and PE section injector.

For the crypto-store access, malcrypt assumes the input public key was created with no or known controls by tpm-keyextract. The security of the private key is not critical to malcrypt if a TPM was used to generate the key pair. Malcrypt intends to limit the execution of the input payload to a target system. There are trusted computing concerns related to proving a TPM was used to create the keypair, but they are outside the scope of the example PoC implementation.

References

• The original TPM Malware: https://www.cs.utexas.edu/~adunn/pubs/malware-tpm.pdf
• DEF CON 22 WAGONBED: https://www.defcon.org/html/defcon-22/dc-22-speakers.html#Datko
• Windows PCP Tool: http://research.microsoft.com/en-us/downloads/74c45746-24ad-4cb7-ba4b-0c6df2f92d5d/

License

MIT and Microsoft MSR-LA.