TETD: Trusted Execution in Trust Domains

This repository implements a full-stack prototype of TETD (Trusted Execution in Trust Domains). TETD is a lightweight framework for securely running agents inside Intel TDX Trust Domains (TDs), with coordinated VMM-side logic. It supports both exclusive and collaborative execution modes for TD-resident agents.

The prototype consists of two main components:

• TETD-G: a Linux kernel module running inside the guest TD, managing agent loading, relocation, and secure communication with the VMM.
• TETD-H: a KVM-based hypervisor extension running on the host side, responsible for managing agent memory, handling TDCALLs, and coordinating agent invocations.

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Guest-Side (TETD-G) Overview

The TETD-G kernel module manages the agent lifecycle inside the TD:

• Exclusive Mode: Agent runs directly inside TD, coordinating with VMM via TDCALL.
• Collaborative Mode: Agent relocates itself to a secret zone, with a custom page table, GDT, and IDT. Executed in an isolated enclave-like environment.

The module provides runtime debugging via /proc/tetdg_info and supports:

• Encrypted agent arguments/results
• Dynamic agent registration
• Support for a privileged admin agent to inspect/control other agents

Agent Development

TETD agents are lightweight binaries that register entry points with the TETD framework. To write a new agent:

1. Define an agent_init() function:

   void agent_init(void)
   {
       tetdg_agent_call_register(1, &my_agent_handler);
   }

2. Implement the handler:

   int my_agent_handler(void *args) {
       // process arguments, do work
       return 0;
   }

3. Add your agent to agents/Makefile.

4. Load the compiled agent into the TD along with the tetdg kernel module.

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Host-Side (TETD-H) Overview

TETD-H extends the KVM module to:

• Allocate and manage secret zones via CMA
• Intercept TDCALLs from TETD-G
• Maintain agent tables per TD
• Dynamically block/unblock pages via SEAMCALL
• Support eventfd/io_uring for agent call notification

Key VMM Features

• Handles leaf functions like:
  • TDCALL_FN_VMM_ENTER, TDCALL_FN_VMM_RESUME
  • TDCALL_FN_AGENT_ACCESS, TDCALL_FN_AGENT_DISABLE
• Supports SEAMCALLs:
  • TDH.MEM.PAGE.AUG, TDH.MEM.PAGE.REMOVE
  • TDH.MEM.RANGE.BLOCK, TDH.MEM.TRACK

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Enabling SGX-SSL for Agent Encryption

To support agent-side encryption:

1. Download and build SGX-SSL, and place it under sgx-ssl/
2. Enable ENCRYPT_REG macro in your agent or tetdg compile-time flags
3. TETD will use the crypto APIs to encrypt all agent arguments and results

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Security Notes

• The guest kernel is considered untrusted; TETD enforces memory and control-flow isolation.
• Agent relocation uses independent page tables with masked interrupts.
• Communication with the VMM is only via TDCALL, minimizing the attack surface.

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License

This prototype is released under the MIT License. See LICENSE for details.

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Contact

For research inquiries or integration into your TDX environment, please contact the maintainer or open an issue.