COMMON WEAKNESS ENUMERATIONStable

CWE-1274

Improper Access Control for Volatile Memory Containing Boot Code

The product conducts a secure-boot process that transfers bootloader code from Non-Volatile Memory (NVM) into Volatile Memory (VM), but it does not have sufficient access control or other protections for the Volatile Memory.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product conducts a secure-boot process that transfers bootloader code from Non-Volatile Memory (NVM) into Volatile Memory (VM), but it does not have sufficient access control or other protections for the Volatile Memory.

Extended description

Adversaries could bypass the secure-boot process and execute their own untrusted, malicious boot code. As a part of a secure-boot process, the read-only-memory (ROM) code for a System-on-Chip (SoC) or other system fetches bootloader code from Non-Volatile Memory (NVM) and stores the code in Volatile Memory (VM), such as dynamic, random-access memory (DRAM) or static, random-access memory (SRAM). The NVM is usually external to the SoC, while the VM is internal to the SoC. As the code is transferred from NVM to VM, it is authenticated by the SoC's ROM code.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

This weakness can be introduced during hardware architecture or design but can be identified later during testing.

Risk

What does successful exploitation lead to?

Modify MemoryExecute Unauthorized Code or CommandsGain Privileges or Assume Identity

Affected security scopes: Access Control, Integrity

If the volatile-memory-region protections or access controls are insufficient to prevent modifications from an adversary or untrusted agent, the secure boot may be bypassed or replaced with the execution of an adversary's code.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Ensure that the design of volatile-memory protections is enough to prevent modification from an adversary or untrusted code.

Testing

Testing and verification approach

Detail
Test the volatile-memory protections to ensure they are safe from modification or untrusted code.

Verification

How is it detected?

Manual Analysis

High
Ensure the volatile memory is lockable or has locks. Ensure the volatile memory is locked for writes from untrusted agents or adversaries. Try modifying the volatile memory from an untrusted agent, and ensure these writes are dropped.

Manual Analysis

Moderate
Analyze the device using the following steps: 1. Identify all fabric master agents that are active during system Boot Flow when initial code is loaded from Non-volatile storage to volatile memory. 1. Identify the volatile memory regions that are used for storing loaded system executable program. 1. During system boot, test programming the identified memory regions in step 2 from all the masters identified in step 1. Only trusted masters should be allowed to write to the memory regions. For example, pluggable device peripherals should not have write access to program load memory regions.