CWE - CWE-1317: Improper Access Control in Fabric Bridge (4.12)

Weakness ID: 1317

Abstraction: Base
Structure: Simple

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Description

The product uses a fabric bridge for transactions between two Intellectual Property (IP) blocks, but the bridge does not properly perform the expected privilege, identity, or other access control checks between those IP blocks.

Extended Description

In hardware designs, different IP blocks are connected through interconnect-bus fabrics (e.g. AHB and OCP). Within a System on Chip (SoC), the IP block subsystems could be using different bus protocols. In such a case, the IP blocks are then linked to the central bus (and to other IP blocks) through a fabric bridge. Bridges are used as bus-interconnect-routing modules that link different protocols or separate, different segments of the overall SoC interconnect.

For overall system security, it is important that the access-control privileges associated with any fabric transaction are consistently maintained and applied, even when they are routed or translated by a fabric bridge. A bridge that is connected to a fabric without security features forwards transactions to the slave without checking the privilege level of the master and results in a weakness in SoC access-control security. The same weakness occurs if a bridge does not check the hardware identity of the transaction received from the slave interface of the bridge.

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	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.	284	Improper Access Control

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.	1203	Peripherals, On-chip Fabric, and Interface/IO Problems

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
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)

Technologies

Processor Hardware (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 Access Control Availability	Technical Impact: DoS: Crash, Exit, or Restart; Bypass Protection Mechanism; Read Memory; Modify Memory	Medium

Demonstrative Examples

Example 1

This example is from CVE-2019-6260 [REF-1138]. The iLPC2AHB bridge connects a CPU (with multiple, privilege levels, such as user, super user, debug, etc.) over AHB interface to an LPC bus. Several peripherals are connected to the LPC bus. The bridge is expected to check the privilege level of the transactions initiated in the core before forwarding them to the peripherals on the LPC bus.

The bridge does not implement the checks and allows reads and writes from all privilege levels.

To address this, designers should implement hardware-based checks that are either hardcoded to block untrusted agents from accessing secure peripherals or implement firmware flows that configure the bridge to block untrusted agents from making arbitrary reads or writes.

Observed Examples

Reference	Description
CVE-2019-6260	Baseboard Management Controller (BMC) device implements Advanced High-performance Bus (AHB) bridges that do not require authentication for arbitrary read and write access to the BMC's physical address space from the host, and possibly the network [REF-1138].

Potential Mitigations

Phase: Architecture and Design

Ensure that the design includes provisions for access-control checks in the bridge for both upstream and downstream transactions.

Phase: Implementation

Implement access-control checks in the bridge for both upstream and downstream transactions.

Detection Methods

Simulation / Emulation

RTL simulation to ensure that bridge-access controls are implemented properly.

Effectiveness: High

Formal Verification

Formal verification of bridge RTL to ensure that access control cannot be bypassed.

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	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1396	Comprehensive Categorization: Access Control

Vulnerability Mapping Notes

Usage: Allowed

(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.

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-122	Privilege Abuse

References

[REF-1138] Stewart Smith. "CVE-2019-6260: Gaining control of BMC from the host processor". 2019. <https://www.flamingspork.com/blog/2019/01/23/cve-2019-6260:-gaining-control-of-bmc-from-the-host-processor/>.

Content History

Submissions
Submission Date	Submitter	Organization
2020-05-19 (CWE 4.3, 2020-12-10)	Arun Kanuparthi, Hareesh Khattri, Parbati Kumar Manna	Intel Corporation
2020-05-19 (CWE 4.3, 2020-12-10)
Modifications
Modification Date	Modifier	Organization
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Observed_Examples
2022-04-28	CWE Content Team	MITRE
2022-04-28	updated Applicable_Platforms
2022-06-28	CWE Content Team	MITRE
2022-06-28	updated Applicable_Platforms
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Demonstrative_Examples, Description, Detection_Factors, Name, Potential_Mitigations
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2022-10-13	Missing Security Checks in Fabric Bridge


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Common Weakness Enumeration

CWE-1317: Improper Access Control in Fabric Bridge

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