COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1259

Improper Restriction of Security Token Assignment

The System-On-A-Chip (SoC) implements a Security Token mechanism to differentiate what actions are allowed or disallowed when a transaction originates from an entity. However, the Security Tokens are improperly protected.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The System-On-A-Chip (SoC) implements a Security Token mechanism to differentiate what actions are allowed or disallowed when a transaction originates from an entity. However, the Security Tokens are improperly protected.

Extended description

Systems-On-A-Chip (Integrated circuits and hardware engines) implement Security Tokens to differentiate and identify which actions originated from which agent. These actions may be one of the directives: 'read', 'write', 'program', 'reset', 'fetch', 'compute', etc. Security Tokens are assigned to every agent in the System that is capable of generating an action or receiving an action from another agent. Multiple Security Tokens may be assigned to an agent and may be unique based on the agent's trust level or allowed privileges. Since the Security Tokens are integral for the maintenance of security in an SoC, they need to be protected properly. A common weakness afflicting Security Tokens is improperly restricting the assignment to trusted components.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Modify Files or DirectoriesExecute Unauthorized Code or CommandsBypass Protection MechanismGain Privileges or Assume IdentityModify MemoryModify MemoryDoS: Crash, Exit, or Restart

Affected security scopes: Confidentiality, Integrity, Availability, Access Control

An improperly protected Security Token may be able to be programmed by a malicious agent (i.e., the Security Token is mutable) to spoof the action as if it originated from a trusted agent.

Defence

How is it prevented and fixed?

Architecture and Design · Implementation

Defence to apply across several lifecycle phases

Detail
- Security Token assignment review checks for design inconsistency and common weaknesses. - Security-Token definition and programming flow is tested in both pre-silicon and post-silicon testing.