CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection
The product uses a register lock bit protection mechanism, but it does not ensure that the lock bit prevents modification of system registers or controls that perform changes to important hardware system configuration.
How it's found
Security-Sensitive Hardware Controls with Missing Lock Bit Protection is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
Integrated circuits and hardware intellectual properties (IPs) might provide device configuration controls that need to be programmed after device power reset by a trusted firmware or software module, commonly set by BIOS/bootloader. After reset, there can be an expectation that the controls cannot be used to perform any further modification. This behavior is commonly implemented using a trusted lock bit, which can be set to disable 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). However, if the lock bit does not effectively write-protect all system registers or controls that could modify the protected system configuration, then an adversary may be able to use software to access the registers/controls and modify the protected hardware configuration.
Vulnerable vs. safe
Register
Field description
CRITICAL_TEMP_LIMIT
[31:8] Reserved field; Read only; Default 0[7:0] Critical temp 0-255 Centigrade; Read-write-lock; Default 125
TEMP_SENSOR_CALIB
[31:0] Thermal sensor calibration data. A slope value used to map sensor reading to a degree Centigrade. Read-write; Default 25
TEMP_SENSOR_LOCK
[31:1] Reserved field; Read only; Default 0[0] Lock bit, locks CRITICAL_TEMP_LIMIT register; Write-1-once; Default 0
TEMP_HW_SHUTDOWN
[31:2] Reserved field; Read only; Default 0[1] Enable hardware shutdown on a critical temperature detection; Read-write; Default 0
CURRENT_TEMP
[31:8] Reserved field; Read only; Default 0[7:0] Current Temp 0-255 Centigrade; Read-only; Default 0Change TEMP_HW_SHUTDOWN and TEMP_SENSOR_CALIB controls to be locked by TEMP_SENSOR_LOCK.TEMP_SENSOR_CALIB
[31:0] Thermal sensor calibration data. A slope value used to map sensor reading to a degree Centigrade. Read-write-Lock; Default 25; Locked by TEMP_SENSOR_LOCK bit[0]
TEMP_HW_SHUTDOWN
[31:2] Reserved field; Read only; Default 0[1] Enable hardware shutdown on critical temperature detection; Read-write-Lock; Default 0; Locked by TEMP_SENSOR_LOCK bit[0]Consequences
- Modify Memory: System Configuration protected by the lock bit can be modified even when the lock is set.
Mitigations
- Architecture and Design/Implementation/Testing: Security lock bit protections must be reviewed for design inconsistency and common weaknesses. Security lock programming flow and lock properties must be tested in pre-silicon and post-silicon testing.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-1233?
The product uses a register lock bit protection mechanism, but it does not ensure that the lock bit prevents modification of system registers or controls that perform changes to important hardware system configuration.
How do you find Security-Sensitive Hardware Controls with Missing Lock Bit Protection?
Security-Sensitive Hardware Controls with Missing Lock Bit Protection is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
What is the impact of CWE-1233?
Modify Memory: System Configuration protected by the lock bit can be modified even when the lock is set.
Does TurboPentest test for Security-Sensitive Hardware Controls with Missing Lock Bit Protection?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
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Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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