Reflections on Trusting TrustZone
summary
Reverse-engineered Qualcomm TrustZone (QSE/QCE) firmware with IDA Pro and firmware images pulled via DD, finds an integer overflow in SMC command length checks that lets a crafted SMC command buffer pass all sanity checks. Exploit writes a hard-coded 12-byte response header (12,12,1) into arbitrary secure memory, then performs an SMC table extension attack to redirect handler parsing and achieve arbitrary TrustZone code execution. Demo permanently unlocks a Moto X bootloader by blowing a QFuse; ADB/fastboot used for the live exploit.
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chapters (25)
- 0:00Intro
- 0:16What is TrustZone?
- 0:38TrustZone Architecture
- 2:06Real-World Uses
- 4:02Prior Work
- 5:50Motivation
- 7:26Toolchain
- 8:45Attack Surface
- 11:13Attacker Assumptions
- 13:48QSEE SCM Interface
- 14:14SCM Call-by-Register Convention
- 14:44SCM Command Structures
- 16:08Structure Sanity Checking
- 19:10Secure Memory Checking Pseudocode
- 20:19Review: Integer Overflow
- 21:04Integer Overflow Vulnerability
- 21:59Pathological Command Buffer
- 24:06What is Written to Response Header?
- 25:49Sorcery!
- 26:45Building Better Primitives
- 29:20Choosing A New Write Primitive
- 29:54SMC Handler Table
- 31:03SMC Table Extension Attack
- 32:20Arbitrary TZ Code Execution
- 36:03Lessons Learned
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