CWE - CWE-1239: Improper Zeroization of Hardware Register (4.11)

Weakness ID: 1239

Abstraction: Variant
Structure: Simple

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Description

The hardware product does not properly clear sensitive information from built-in registers when the user of the hardware block changes.

Extended Description

Hardware logic operates on data stored in registers local to the hardware block. Most hardware IPs, including cryptographic accelerators, rely on registers to buffer I/O, store intermediate values, and interface with software. The result of this is that sensitive information, such as passwords or encryption keys, can exist in locations not transparent to the user of the hardware logic. When a different entity obtains access to the IP due to a change in operating mode or conditions, the new entity can extract information belonging to the previous user if no mechanisms are in place to clear register contents. It is important to clear information stored in the hardware if a physical attack on the product is detected, or if the user of the hardware block changes. The process of clearing register contents in a hardware IP is referred to as zeroization in standards for cryptographic hardware modules such as FIPS-140-2 [REF-267].

Relationships

This table 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)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	226	Sensitive Information in Resource Not Removed Before Reuse

Relevant to the view "Hardware Design" (CWE-1194)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	226	Sensitive Information in Resource Not Removed Before Reuse

Modes Of Introduction

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.

Phase	Note
Architecture and Design	Lack of hardware mechanisms to zeroize or clear registers in the design or specification.
Implementation	Mechanisms to zeroize and clear registers are in the design but implemented incorrectly.
Operation	Hardware-provided zeroization mechanisms are not used appropriately by the IP user (ex. firmware), or data remanence issues are not taken into account.

Applicable Platforms

This listing shows 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.

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Operating Systems

Class: Not OS-Specific (Undetermined Prevalence)

Architectures

Class: Not Architecture-Specific (Undetermined Prevalence)

Technologies

Class: System on Chip (Undetermined Prevalence)

Common Consequences

This table 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.

Scope	Impact	Likelihood
Confidentiality	Technical Impact: Varies by Context The consequences will depend on the information disclosed due to the vulnerability.

Demonstrative Examples

Example 1

Suppose a hardware IP for implementing an encryption routine works as expected, but it leaves the intermediate results in some registers that can be accessed. Exactly why this access happens is immaterial - it might be unintentional or intentional, where the designer wanted a "quick fix" for something.

Potential Mitigations

Phase: Architecture and Design

Every register potentially containing sensitive information must have a policy specifying how and when information is cleared, in addition to clarifying if it is the responsibility of the hardware logic or IP user to initiate the zeroization procedure at the appropriate time.

Note: Unfortunately, data disclosure can occur even after information has been overwritten/zeroized from the digital perspective. Physical characteristics of the memory can reveal the history of previously written data. For example, if the same value is written repeatedly to a memory location, the corresponding memory cells can become physically altered to a degree that even if the original data is erased it can still be recovered through physical characterization of the memory cells [REF-1055].

Memberships

This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1416	Comprehensive Categorization: Resource Lifecycle Management

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-150	Collect Data from Common Resource Locations
CAPEC-204	Lifting Sensitive Data Embedded in Cache
CAPEC-37	Retrieve Embedded Sensitive Data
CAPEC-545	Pull Data from System Resources

References

[REF-267] Information Technology Laboratory, National Institute of Standards and Technology. "SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2001-05-25. <https://csrc.nist.gov/csrc/media/publications/fips/140/2/final/documents/fips1402.pdf>. URL validated: 2023-04-07.

[REF-1055] Peter Gutmann. "Data Remanence in Semiconductor Devices". 10th USENIX Security Symposium. 2001-08. <https://www.usenix.org/legacy/events/sec01/full_papers/gutmann/gutmann.pdf>.

Content History

Submissions
Submission Date	Submitter	Organization
2020-02-08	Nicole Fern	Tortuga Logic
2020-02-08
Modifications
Modification Date	Modifier	Organization
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Related_Attack_Patterns
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated References, Relationships


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CWE-1239: Improper Zeroization of Hardware Register

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