CWE-1189 Improper Isolation of Shared Resources on System-on-a-Chip (SoC)

The System-On-a-Chip (SoC) does not properly isolate shared resources between trusted and untrusted agents.

A System-On-a-Chip (SoC) has a lot of functionality, but it may have a limited number of pins or pads. A pin can only perform one function at a time. However, it can be configured to perform multiple different functions. This technique is called pin multiplexing. Similarly, several resources on the chip may be shared to multiplex and support different features or functions. When such resources are shared between trusted and untrusted agents, untrusted agents may be able to access the assets intended to be accessed only by the trusted agents.

• Access Control: Bypass Protection Mechanism — If resources being used by a trusted user are shared with an untrusted user, the untrusted user may be able to modify the functionality of the shared resource of the trusted user. • Integrity: Quality Degradation — The functionality of the shared resource may be intentionally degraded.

• [Architecture and Design] When sharing resources, avoid mixing agents of varying trust levels. Untrusted agents should not share resources with trusted agents.

• Automated Dynamic Analysis: Pre-silicon / post-silicon: Test access to shared systems resources (memory ranges, control registers, etc.) from untrusted software to verify that the assets are not incorrectly exposed to untrusted agents. Note that access to shared resources can be dynamically allowed or revoked based on system flows. Security testing should cover such dynamic shared resource allocation and access control modification flows.

• CVE-2020-8698: Processor has improper isolation of shared resources allowing for information disclosure. • CVE-2019-6260: Baseboard Management Controller (BMC) device implements Advanced High-performance Bus (AHB) bridges that do not require authentication for arbitrary read and write access to the BMC's physical address space from the host, and possibly the network [REF-1138].