CWE-1233: Improper Hardware Lock Protection for Security Sensitive Controls
The product implements a register lock bit protection feature that permits security sensitive controls to modify the protected configuration.
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. This is commonly implemented using a trusted lock bit, which when set disables writes to a protected set of registers or address regions. The lock protection is intended to prevent modification of certain system configuration (e.g., memory/memory protection unit configuration). If any system registers/controls that can modify the protected configuration are not write-protected by the lock, they can then be leveraged by software to modify the protected configuration.
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.
For example, consider the example design below or a digital thermal sensor used in the design to detect overheating of the silicon to trigger a system shutdown. The system critical temperature limit (CRITICAL_TEMP_LIMIT) and thermal sensor calibration (TEMP_SENSOR_CALIB) data have to be programmed by the firmware.
Example Language: Other
In this example note that only the CRITICAL_TEMP_LIMIT register is protected by the TEMP_SENSOR_LOCK bit, while the security design intent is to protect any modification of the critical temperature detection and response.
The response of the system, if the system heats to a critical temperature, is controlled by TEMP_HW_SHUTDOWN bit , which is not lockable. Also, the TEMP_SENSOR_CALIB register is not protected by the lock bit.
By modifying the temperature sensor calibration, the conversion of the sensor data to a degree centigrade can be changed, such that the current temperature will never be detected to exceed critical temperature value programmed by the protected lock.
Similarly, by modifying the TEMP_HW_SHUTDOWN.Enable bit, the system response detection of the current temperature exceeding critical temperature can be disabled.
Change TEMP_HW_SHUTDOWN and TEMP_SENSOR_CALIB controls to be locked by TEMP_SENSOR_LOCK.
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