CWE-1231: Improper Implementation of Lock Protection Registers
The product incorrectly implements register lock bit protection features such that protected controls can be programmed even after the lock has been set.
In integrated circuits and hardware IPs, device configuration controls are commonly programmed after a device power reset by a trusted firmware or software module (e.g., BIOS/bootloader) and then locked from any further modification. This is commonly implemented using a trusted lock bit, which when set disables writes to a protected set of registers or address regions. Design or coding errors in the implementation of the lock bit protection feature may allow the lock bit to be modified or cleared by software after being set to unlock the system.
The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
Relevant to the view "Hardware Design" (CWE-1194)
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Class: Language-Independent (Undetermined Prevalence)
Class: OS-Independent (Undetermined Prevalence)
Class: Architecture-Independent (Undetermined Prevalence)
Class: Technology-Independent (Undetermined Prevalence)
The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Consider the example design below or a digital thermal sensor used in the design to detect overheating of the silicon and trigger system shutdown. The system critical temperature limit (CRITICAL_TEMP_LIMIT) and thermal sensor calibration (TEMP_SENSOR_CALIB) data have to be programmed by firmware and then the register needs to be locked (TEMP_SENSOR_LOCK).
Example Language: Other
In this example note that the response of the system if the system heats to critical temperature is controlled by TEMP_HW_SHUTDOWN bit , which is not lockable. Thus, the intended security property of the critical temperature sensor cannot be fully protected,since software can misconfigure the TEMP_HW_SHUTDOWN register even after the lock bit is set to disable the shutdown response.
Change TEMP_HW_SHUTDOWN field to be locked by TEMP_SENSOR_LOCK.
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