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ID

CWE-1292: Incorrect Conversion of Security Identifiers

Weakness ID: 1292
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ 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.
+ Extended Description

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.

+ Relationships

The table(s) below 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)
NatureTypeIDName
ChildOfPillarPillar - 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.284Improper Access Control
+ Relevant to the view "Hardware Design" (CWE-1194)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.1294Insecure Security Identifier Mechanism
+ 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.

PhaseNote
Architecture and DesignSuch issues could be introduced during hardware architecture and design, then identified later during Testing or System Configuration phases.
ImplementationSuch issues could be introduced during hardware implementation, then identified later during Testing or System Configuration phases.
+ Applicable Platforms
The listings below show 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: Language-Independent (Undetermined Prevalence)

Operating Systems

Class: OS-Independent (Undetermined Prevalence)

Architectures

Class: Architecture-Independent (Undetermined Prevalence)

Technologies

Bus/Interface IP (Undetermined Prevalence)

Class: Technology-Independent (Undetermined Prevalence)

+ Common Consequences

The table below 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.

ScopeImpactLikelihood
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; Quality Degradation

High
+ Demonstrative Examples

Example 1

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.

Register Field Description
AES_ENC_DEC_KEY_0 AES key [0:31] for encryption or decryption Default 0x00000000
AES_ENC_DEC_KEY_1 AES key [32:63] for encryption or decryption Default 0x00000000
AES_ENC_DEC_KEY_2 AES key [64:95] for encryption or decryption Default 0x00000000
AES_ENC_DEC_KEY_3 AES key [96:127] for encryption or decryption Default 0x00000000
AES_KEY_ACCESS_POLICY [31:4] Default 0x000000 [3:0] – 0x02 agent with Security Identifier “1” has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_4 registers

During conversion of the AHB-to-OCP transaction, the security identifier information must be preserved and passed on to the follower correctly.

(bad code)
Example Language: Other 
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 code)
Example Language: Other 
The conversion of the signals from one protocol (AHB) to another (OCP) must be done while preserving the security identifier correctly.
+ Potential Mitigations

Phase: Architecture and Design

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

Phase: Implementation

Access and programming flows must be tested in pre-silicon and post-silicon testing.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2020-04-29Arun Kanuparthi, Hareesh Khattri, Parbati Kumar Manna, Narasimha Kumar V MangipudiIntel Corporation
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Page Last Updated: August 20, 2020