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Base · Medium

CWE-1292: Incorrect Conversion of Security Identifiers

The product implements a conversion mechanism to map certain bus-transaction signals to security identifiers. However, if the conversion is incorrectly implemented, untrusted agents can gain unauthori...

CWE-1292 · Base Level ·2 Mitigations

Description

The product implements a conversion mechanism to map certain bus-transaction signals to security identifiers. However, if the conversion is incorrectly implemented, untrusted agents can gain unauthorized access to the asset.

In a System-On-Chip (SoC), various integrated circuits and hardware engines generate transactions such as to access (reads/writes) assets or perform certain actions (e.g., reset, fetch, compute, etc.). Among various types of message information, a typical transaction is comprised of source identity (to identify the originator of the transaction) and a destination identity (to route the transaction to the respective entity). Sometimes the transactions are qualified with a security identifier. This security identifier helps the destination agent decide on the set of allowed actions (e.g., access an asset for read and writes). A typical bus connects several leader and follower agents. Some follower agents implement bus protocols differently from leader agents. A protocol conversion happens at a bridge to seamlessly connect different protocols on the bus. One example is a system that implements a leader with the Advanced High-performance Bus (AHB) protocol and a follower with the Open-Core Protocol (OCP). A bridge AHB-to-OCP is needed to translate the transaction from one form to the other. A common weakness that can exist in this scenario is that this conversion between protocols is implemented incorrectly, whereupon an untrusted agent may gain unauthorized access to an asset.

Potential Impact

Confidentiality, Integrity, Availability, Access Control

Modify Memory, Read Memory, DoS: Resource Consumption (Other), Execute Unauthorized Code or Commands, Gain Privileges or Assume Identity, Quality Degradation

Demonstrative Examples

Consider a system that supports AHB. Let us assume we have a follower agent that only understands OCP. To connect this follower to the leader, a bridge is introduced, i.e., AHB to OCP. The follower has assets to protect accesses from untrusted leaders, and it employs access controls based on policy, (e.g., AES-Key registers for encryption or decryption). The key is 128 bits implemented as a set of four 32-bit registers. The key registers are assets, and register AES_KEY_ACCESS_POLICY is defined to provide the necessary access controls. The AES_KEY_ACCESS_POLICY access-policy register defines which agents with a security identifier in the transaction can access the AES-key registers. The implemented AES_KEY_ACCESS_POLICY has 4 bits where each bit when "Set" allows access to the AES-Key registers to the corresponding agent that has the security identifier. The other bits from 31 through 4 are reserved and not used. During conversion of the AHB-to-OCP transaction, the security identifier information must be preserved and passed on to the follower correctly.
Bad
In AHB-to-OCP bridge, the security identifier information conversion is done incorrectly.
Because of the incorrect conversion, the security identifier information is either lost or could be modified in such a way that an untrusted leader can access the AES-Key registers.
Good
The conversion of the signals from one protocol (AHB) to another (OCP) must be done while preserving the security identifier correctly.

Mitigations & Prevention

Architecture and Design

Security identifier decoders must be reviewed for design inconsistency and common weaknesses.

Implementation

Access and programming flows must be tested in pre-silicon and post-silicon testing.

CWE-284: Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

CWE-1294: Insecure Security Identifier Mechanism

The System-on-Chip (SoC) implements a Security Identifier mechanism to differentiate what actions are allowed or disallo...

Frequently Asked Questions

What is CWE-1292?

CWE-1292 (Incorrect Conversion of Security Identifiers) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product implements a conversion mechanism to map certain bus-transaction signals to security identifiers. However, if the conversion is incorrectly implemented, untrusted agents can gain unauthori...

How can CWE-1292 be exploited?

Attackers can exploit CWE-1292 (Incorrect Conversion of Security Identifiers) to modify memory, read memory, dos: resource consumption (other), execute unauthorized code or commands, gain privileges or assume identity, quality degradation. This weakness is typically introduced during the Architecture and Design, Implementation phase of software development.

How do I prevent CWE-1292?

Key mitigations include: Security identifier decoders must be reviewed for design inconsistency and common weaknesses.

What is the severity of CWE-1292?

CWE-1292 is classified as a Base-level weakness (Medium abstraction). Its actual severity depends on the specific context and how the weakness manifests in your application.