CWE-1291: Public Key Re-Use for Signing both Debug and Production Code
Weakness ID: 1291
Vulnerability Mapping:ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction:
BaseBase - 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.
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Description
The same public key is used for signing both debug and production code.
Extended Description
A common usage of public-key cryptography is to verify the integrity and authenticity of another entity (for example a firmware binary). If a company wants to ensure that its firmware runs only on its own hardware, before the firmware runs, an encrypted hash of the firmware image will be decrypted with the public key and then verified against the now-computed hash of the firmware image. This means that the public key forms the root of trust, which necessitates that the public key itself must be protected and used properly.
During the development phase, debug firmware enables many hardware debug hooks, debug modes, and debug messages for testing. Those debug facilities provide significant, additional views about the firmware's capability and, in some cases, additional capability into the chip or SoC. If compromised, these capabilities could be exploited by an attacker to take full control of the system.
Once the product exits the manufacturing stage and enters production, it is good practice to use a different public key. Debug firmware images are known to leak. With the debug key being reused as the production key, the debug image will also work on the production image. Thus, it will open all the internal, debug capabilities to the attacker.
If a different public key is used for the production image, even if the attacker gains access to the debug firmware image, they will not be able to run it on a production machine. Thus, damage will be limited to the intellectual property leakage resulting from the debug image.
Dimensions
The Dimensions table provides information about the
different dimensions associated with this weakness. The Type identifies the dimension type,
while the Value provides the specific value for that dimension.
Type
Value
Behavior-Type
Re-Use
Resource-Type
Key
Resource-Property
Public
Behavior-Type
Signing
Code-Type
Code
Code-Property
Debug and Production
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.
Impact
Details
Read Memory; Modify Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Varies by Context
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, Overlaps, and CanAlsoBe are defined to show similar weaknesses that the user
may want to explore.
Relevant to the view "Complete Weakness Hierarchy" (View-1000)
Nature
Type
ID
Name
ChildOf
Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.
Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.
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(s)
Note
Implementation
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.
Type
Applicable Platforms
Notes
Languages
Class: Not Language-Specific
(Undetermined Prevalence)
Operating Systems
Class: Not OS-Specific
(Undetermined Prevalence)
Architectures
Class: Not Architecture-Specific
(Undetermined Prevalence)
Technologies
Class: Not Technology-Specific
(Undetermined Prevalence)
Demonstrative Examples
Example 1
This example illustrates the danger of using the same public key for debug and production.
(bad code)
Example Language: Other
Suppose the product design requires frugality of silicon real estate. Assume that originally the architecture allows just enough storage for two 2048-bit RSA keys in the fuse: one to be used for debug and the other for production. However, in the meantime, a business decision is taken to make the security future-proof beyond 2030, which means the architecture needs to use the NIST-recommended 3072-bit keys instead of the originally-planned 2048-bit keys. This means that, at most, one key can be fully stored in the fuses, not two. So the product design team decides to use the same public key for debug and production.
(informative)
Example Language: Other
Increase the storage so that two different keys of the required size can be stored.
Weakness Ordinalities
Ordinality
Description
Primary
(where the weakness exists independent of other weaknesses)
Detection
Methods
Method
Details
Architecture or Design Review
Compare the debug key with the production key to make sure that they are not the same.
Effectiveness: High
Dynamic Analysis with Manual Results Interpretation
Compare the debug key with the production key to make sure that they are not the same.
Effectiveness: High
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
Grouping - a CWE entry that contains a set of other entries that share a common characteristic.
(this CWE ID may be used to map to real-world vulnerabilities)
Reason
Acceptable-Use
Rationale
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comments
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
Description
The Dimensions table provides information about the
different dimensions associated with this weakness. The Type identifies the dimension type,
while the Value provides the specific value for that dimension.
