Secure Timekeeping Control Primitives for Processor Timer Integrity
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Solution Overview
Problem
Existing processors lack the ability to provide secure and trusted timekeeping that cannot be spoofed or altered by untrusted privileged system software, as the value of the Time Stamp Counter (TSC) can be modified through scaling and offsetting.
Innovation Solution
The implementation of timekeeping control primitives, including a processor with timer circuitry and logic to perform operations such as determining and storing a timer offset or its obfuscated version, ensuring secure timekeeping by preventing modification by untrusted software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the RDTSC instruction is used to read the timer value, then the timer value can be accessed by software, but the timer value can be spoofed or altered by untrusted privileged system software through scaling and offsetting
Solution Approach 1:
The patent segments the timekeeping function into two separate components: a protected hardware timekeeping unit that maintains the actual time value, and a controlled interface that allows software to read time information. This segmentation isolates the trusted time source from untrusted software that could otherwise manipulate the TSC, resolving the contradiction by providing accessibility through a controlled interface while maintaining trustworthiness through hardware protection.
Solution Approach 2:
The patent introduces an intermediary mechanism (the controlled timekeeping interface) between the hardware timer and software. This intermediary allows software to access time information through authorized instructions while preventing untrusted privileged software from directly manipulating the TSC. The intermediary enforces security policies, enabling timer value accessibility while ensuring trustworthiness by blocking spoofing attempts.
2Adaptability or versatility
If the TSC is made accessible to software for timekeeping operations, then timekeeping functionality is provided, but security vulnerabilities arise allowing privileged software to modify the TSC value
Solution Approach 1:
The patent applies preliminary anti-action by implementing hardware-based protection mechanisms that prevent privileged software from modifying the TSC before any potential attacks can occur. The timekeeping unit is designed with inherent security controls that block unauthorized write operations and scaling/offsetting attempts, thereby providing timekeeping functionality while preemptively neutralizing the vulnerability to TSC modification.
Solution Approach 2:
The patent introduces disposable or ephemeral timekeeping mechanisms where the actual time value is maintained in protected hardware that cannot be modified by software. Instead of allowing software to directly access and potentially corrupt the TSC, the system provides timekeeping functionality through controlled read-only access or through intermediate representations that are inexpensive and replaceable if compromised, thereby maintaining versatility while eliminating the security vulnerability.
Data Source
AI summary
An apparatus of an aspect includes timer circuitry to provide a timer value based at least in part on a timer offset, and an execution unit to perform operations corresponding to a timekeeping control primitive. The timekeeping control primitive is to indicate a destination storage location. The operations include to determine the timer offset based on at least one timer offset control, and to store either the timer offset, or a deterministically obfuscated version of the timer offset, in the destination storage location. Other apparatus, methods, systems, and timekeeping control primitives are disclosed.