Détail du CWE-1223

A write-once register in hardware design is programmable by an untrusted software component earlier than the trusted software component, resulting in a race condition issue.

Integrated circuits and hardware IP software programmable controls and settings are commonly stored in register circuits. These register contents have to be initialized at hardware reset to defined default values that are hard coded in the hardware description language (HDL) code of the hardware unit. A common security protection method used to protect register settings from modification by software is to make them write-once. This means the hardware implementation only allows writing to such registers once, and they become read-only after having been written once by software. This is useful to allow initial boot software to configure systems settings to secure values while blocking runtime software from modifying such hardware settings.

Implementation issues in hardware design of such controls can expose such registers to a race condition security flaw. For example, consider a hardware design that has two different software/firmware modules executing in parallel. One module is trusted (module A) and another is untrusted (module B). In this design it could be possible for Module B to send write cycles to the write-once register before Module A. Since the field is write-once the programmed value from Module A will be ignored and the pre-empted value programmed by Module B will be used by hardware.

Modes d'introduction

Architecture and Design : This weakness can appear in designs that use register write-once attributes with two or more software/firmware modules with varying levels of trust executing in parallel.

Plateformes applicables

Langue

Name: Verilog (Undetermined)
Name: VHDL (Undetermined)

Technologies

Class: System on Chip (Undetermined)

Conséquences courantes

Mesures d’atténuation potentielles

Phases : Architecture and Design
During hardware design all register write-once or sticky fields must be evaluated for proper configuration.
Phases : Testing
The testing phase should use automated tools to test that values are not reprogrammable and that write-once fields lock on writing zeros.

Notes de cartographie des vulnérabilités

Justification : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Commentaire : 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.

Modèles d'attaque associés

Soumission

Modifications