Pointer Authentication Fault Detection via Executable Memory Checks
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Solution Overview
Problem
Existing Pointer Authentication (PA) technologies lack a deterministic mechanism to distinguish between memory faults caused by PA failures and those caused by programming bugs, as both types of faults appear similar and cannot be differentiated.
Innovation Solution
A memory fault handler is configured to analyze memory pointers that trigger faults by attempting to 'fix-up' reserved bits in the pointers to a default value and checking if the resulting pointer corresponds to an executable memory location, thereby determining if the fault is due to a PA failure or a programming error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Pointer Authentication (PA) is implemented to mitigate ROP attacks, then security against ROP attacks is improved, but the ability to distinguish between PA-caused memory faults and programming bug-caused memory faults deteriorates
Solution Approach 1:
The patent introduces a memory fault handler as an intermediary component that sits between the processor and the operating system/application. This handler intercepts memory faults, analyzes their characteristics, and determines whether they originate from PA failures or programming bugs. The handler uses debugging information and pointer validation techniques to distinguish between the two causes, thereby resolving the contradiction by providing a mediation mechanism that preserves both security and fault distinguishability.
Solution Approach 2:
The patent segments the memory fault handling process into distinct analysis stages: initial fault capture, pointer validation against debugging information, characteristic analysis, and cause determination. By dividing the fault detection and analysis process into separate modular components, the system can systematically evaluate different aspects of memory faults and accurately distinguish between PA failures and programming bugs while maintaining security.
2Ease of operation
If memory fault handling is simplified to treat all faults uniformly, then ease of operation is improved, but security detection capability deteriorates
Solution Approach 1:
The patent implements dynamic memory fault handling where the response to a memory fault is not fixed but adapts based on the fault's determined cause. The system dynamically adjusts its behavior: for PA failures, it triggers security responses such as terminating the compromised process; for programming bugs, it allows appropriate debugging or error handling. This dynamic approach maintains ease of operation while preserving security detection capability through context-aware decision-making.
Solution Approach 2:
The patent changes the parameter of fault handling response based on the analyzed characteristics of the memory fault. By modifying the handling behavior according to the determined cause (PA failure vs. programming bug), the system achieves both ease of operation through automated differentiation and security detection capability through cause-specific responses. The handling parameters are adjusted dynamically based on analysis results.
Data Source
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AI summary
Handling a memory fault based on detecting whether a memory pointer was invalidated by a pointer authentication (PA) failure. After an access to a memory pointer causes a memory fault, detecting that the memory pointer was invalidated by a PA failure includes creating a new memory pointer by replacing reserved bits of the memory pointer with a default value, and determining that the new memory pointer corresponds to a memory address that falls within executable memory. This determination includes determining that the memory address is within an executable memory page, determining that a call instruction is stored at a prior memory address that immediately precedes the memory address, and/or determining that the memory address corresponds to a code section of an executable file. The PA failure is handled based on logging the PA failure, terminating the application program, and/or resuming execution at an instruction stored at the memory address.