CWE-1299: Missing Protection Mechanism for Alternate Hardware Interface
Weakness ID: 1299
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 lack of protections on alternate paths to access control-protected assets (such as unprotected shadow registers and other external facing unguarded interfaces) allows an attacker to bypass existing protections to the asset that are only performed against the primary path.
Extended Description
An asset inside a chip might have access-control protections through one interface. However, if all paths to the asset are not protected, an attacker might compromise the asset through alternate paths. These alternate paths could be through shadow or mirror registers inside the IP core, or could be paths from other external-facing interfaces to the IP core or SoC.
Consider an SoC with various interfaces such as UART, SMBUS, PCIe, USB, etc. If access control is implemented for SoC internal registers only over the PCIe interface, then an attacker could still modify the SoC internal registers through alternate paths by coming through interfaces such as UART, SMBUS, USB, etc.
Alternatively, attackers might be able to bypass existing protections by exploiting unprotected, shadow registers. Shadow registers and mirror registers typically refer to registers that can be accessed from multiple addresses. Writing to or reading from the aliased/mirrored address has the same effect as writing to the address of the main register. They are typically implemented within an IP core or SoC to temporarily hold certain data. These data will later be updated to the main register, and both registers will be in synch. If the shadow registers are not access-protected, attackers could simply initiate transactions to the shadow registers and compromise system security.
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.
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.
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 "Hardware Design" (CWE-1194)
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
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.
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.
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
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.
Languages
Class: Not Language-Specific (Undetermined Prevalence)
Operating Systems
Class: Not OS-Specific (Undetermined Prevalence)
Architectures
Class: Not Architecture-Specific (Undetermined Prevalence)
Class: Not Technology-Specific (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 Integrity Availability Access Control
Technical Impact: Modify Memory; Read Memory; DoS: Resource Consumption (Other); Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Alter Execution Logic; Bypass Protection Mechanism; Quality Degradation
High
Demonstrative Examples
Example 1
Register SECURE_ME is located at address 0xF00. A
mirror of this register called COPY_OF_SECURE_ME is
at location 0x800F00. The register SECURE_ME is
protected from malicious agents and only allows
access to select, while COPY_OF_SECURE_ME is not.
Access control is implemented using an allowlist (as
indicated by acl_oh_allowlist). The identity of the
initiator of the transaction is indicated by the
one hot input, incoming_id. This is checked against
the acl_oh_allowlist (which contains a list of
initiators that are allowed to access the asset).
Though this example is shown in Verilog, it will
apply to VHDL as well.
The bugged line of code is repeated in the Bad
example above. The weakness arises from the fact that the
SECURE_ME register can be modified by writing to the
shadow register COPY_OF_SECURE_ME. The address of
COPY_OF_SECURE_ME should also be included in the check.
That buggy line of code should instead be replaced as
shown in the Good Code Snippet below.
When the internal flash is protected by blocking access on the Data Bus (DBUS), it can still be indirectly accessed through the Instruction Bus (IBUS).
When GPIO is protected by blocking access to corresponding GPIO resource registers, protection can be bypassed by writing to the corresponding banked GPIO registers instead.
monitor device allows access to physical UART debug port without authentication
Potential Mitigations
Phase: Requirements
Protect assets from accesses against all potential interfaces and alternate paths.
Effectiveness: Defense in Depth
Phase: Architecture and Design
Protect assets from accesses against all potential interfaces and alternate paths.
Effectiveness: Defense in Depth
Phase: Implementation
Protect assets from accesses against all potential interfaces and alternate paths.
Effectiveness: Defense in Depth
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.
(this CWE ID could 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
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.
