COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1222

Insufficient Granularity of Address Regions Protected by Register Locks

The product defines a large address region protected from modification by the same register lock control bit. This results in a conflict between the functional requirement that some addresses need to be writable by software during operation and the security requirement that the system configuration lock bit must be set during the boot process.

Abstraction

Variant

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product defines a large address region protected from modification by the same register lock control bit. This results in a conflict between the functional requirement that some addresses need to be writable by software during operation and the security requirement that the system configuration lock bit must be set during the boot process.

Extended description

Integrated circuits and hardware IPs can expose the device configuration controls that need to be programmed after device power reset by a trusted firmware or software module (commonly set by BIOS/bootloader) and then locked from any further modification. In hardware design, this is commonly implemented using a programmable lock bit which enables/disables writing to a protected set of registers or address regions. When the programmable lock bit is set, the relevant address region can be implemented as a hardcoded value in hardware logic that cannot be changed later. A problem can arise wherein the protected region definition is not granular enough. After the programmable lock bit has been set, then this new functionality cannot be implemented without change to the hardware design.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Such issues are introduced during hardware architecture and design since software controls and configuration are defined during these phases and identified later during Testing or System Configuration phases.

Risk

What does successful exploitation lead to?

Other

Affected security scopes: Access Control

System security configuration cannot be defined in a way that does not conflict with functional requirements of device.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
The defining of protected locked registers should be reviewed or tested early in the design phase with software teams to ensure software flows are not blocked by the security locks. As an alternative to using register lock control bits and fixed access control regions, the hardware design could use programmable security access control configuration so that device trusted firmware can configure and change the protected regions based on software usage and security models.
CWE-1222: Common Weakness Enumeration Entry CWE-1222 · DayBreach Sözlük · DayBreach