CWE-1189

Base Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Stable MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE
Improper Isolation of Shared Resources on System-on-a-Chip (SoC)

Description

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.

Consequences

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.

Mitigations

Phase: Architecture and Design

When sharing resources, avoid mixing agents of varying trust levels. Untrusted agents should not share resources with trusted agents.

Detection

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.