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.

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.

Modes Of Introduction

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.

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Operating Systems

Class: Not OS-Specific (Undetermined)

Architectures

Class: Not Architecture-Specific (Undetermined)

Technologies

Class: System on Chip (Undetermined)

Common Consequences

Potential Mitigations

Phases : Architecture and Design

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.

Vulnerability Mapping Notes

Rationale : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comments : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Related Attack Patterns

Submission

Modifications