TEEPwn: Breaking TEEs by Experience

DATE: 22-25 August 2022

TIME: 09:00 to 17:00 SGT/GMT +8

It’s notoriously hard to secure a Trusted Execution Environment (TEE) due to the interaction between complex hardware and a large trusted code base (TCB). The security provided by TEEs has been broken on a wide variety of devices, including mobile phones, smart TVs and even vehicles. Publicly disclosed TEE vulnerabilities were often exploited directly from the less-trusted Rich Execution Environment (REE). Many of these vulnerabilities were speandcific for TEEs and required novel exploitation techniques.

The TEEPwn experience provides an offensive system-level perspective and dives into the darker corners of TEE Security. It is designed with a system-level approach, where you will experience powerful exploitation of TEE vulnerabilities. The TEEPwn experience is hands-on, gamified and driven by an exciting jeopardy-style Capture the Flag (CTF).

Your journey starts by achieving a comprehensive understanding of TEEs, where you will learn how hardware and software concur to enforce effective security boundaries. You will then use this understanding for identifying interesting vulnerabilities across the entire TEE attack surface. You will then be challenged along the path to exploit them in multiple scenarios. All vulnerabilities are identified and exploited on our emulated attack platform which implements an ARMv8 (64-bit) TEE based on ARM TrustZone.

You will take on different roles, as an attacker in control of:

• the REE, attempting to achieve privileged code execution in the TEE.
• the REE, trying to access assess protected by a Trusted Application (TA).
• a TA, aiming to escalate privileges to TEE OS.
• a TA, accessing the protected assets of other TAs.

TEEPwn will guide you into an unexpected range of attack vectors and TEE-specific exploitation techniques, which may be leveraged for novel and creative software exploits. refining your skills to a new level.

Topics Covered

• TEE Fundamentals
  • TEE overview
  • Security model
• ARM TrustZone-based TEEs
  • TEE SW components
  • TEE attacker model
  • TEE attack surface
• REE –> TEE attacks
  • Secure Monitor
  • TEE OS (SMC interface)
  • Exploitation:
    • Vulnerable SMC handlers
    • Broken design
    • Unchecked Pointers
    • Restricted writes
    • Range checks
• REE –> TA attacks
  • Communicating with TAs
  • Global Platform APIs
  • Exploitation:
    • Type confusion
    • TOCTOU (Double fetch)
• TA –> TEE attacks
  • TEE OS (Syscall interface)
  • Drivers
  • Exploitation:
    • Unchecked pointers from TA
    • Vulnerable crypto primitives
• TA –> TA attacks
  • State confusion