CWE-1314: Missing Write Protection for Parametric Data Values
The device does not write-protect the parametric data values for sensors that scale the sensor value, allowing untrusted software to manipulate the apparent result and potentially damage hardware or cause operational failure.
How it's found
Missing Write Protection for Parametric Data Values 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.
Various sensors are used by hardware to detect any devices operating outside of the design limits. The threshold limit values are set by hardware fuses or trusted software such as the BIOS. These limits may be related to thermal, power, voltage, current, and frequency. Hardware mechanisms may be used to protect against alteration of the threshold limit values by untrusted software. The limit values are generally programmed in standard units for the type of value being read. However, the hardware-sensor blocks may report the settings in different units depending upon sensor design and operation. The raw sensor output value is converted to the desired units using a scale conversion based on the parametric data programmed into the sensor. The final converted value is then compared with the previously programmed limits. While the limit values are usually protected, the sensor parametric data values may not be. By changing the parametric data, safe operational limits may be bypassed.
Vulnerable vs. safe
The sensor frequency value is scaled by applying the function:
where a and b are the programmable calibration data coefficients. Software sets a and b to zero ensuring the sensed
temperature is always zero.Sensed Temp = a + b * Sensor FreqThe sensor frequency value is scaled by applying the function:
where a and b are the programmable calibration data coefficients. Untrusted software is prevented from changing the values of either a or b,
preventing this method of manipulating the temperature.Sensed Temp = a + b * Sensor FreqConsequences
- Quality Degradation, DoS: Resource Consumption (Other): Sensor value manipulation, particularly thermal or power, may allow physical damage to occur or disabling of the device by a false fault shutdown causing a Denial-Of-Service.
Mitigations
- Architecture and Design: Access controls for sensor blocks should ensure that only trusted software is allowed to change threshold limits and sensor parametric data.
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-1314?
The device does not write-protect the parametric data values for sensors that scale the sensor value, allowing untrusted software to manipulate the apparent result and potentially damage hardware or cause operational failure.
How do you find Missing Write Protection for Parametric Data Values?
Missing Write Protection for Parametric Data Values 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-1314?
Quality Degradation, DoS: Resource Consumption (Other): Sensor value manipulation, particularly thermal or power, may allow physical damage to occur or disabling of the device by a false fault shutdown causing a Denial-Of-Service.
Does TurboPentest test for Missing Write Protection for Parametric Data Values?
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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