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CWE-1259: Improper Restriction of Security Token Assignment

Weakness ID: 1259
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The System-On-A-Chip (SoC) implements a Security Token mechanism to differentiate what actions are allowed or disallowed when a transaction originates from an entity. However, the Security Tokens are improperly protected.
+ Extended Description
Systems-On-A-Chip (Integrated circuits and hardware engines) implement Security Tokens to differentiate and identify which actions originated from which agent. These actions may be one of the directives: 'read', 'write', 'program', 'reset', 'fetch', 'compute', etc. Security Tokens are assigned to every agent in the System that is capable of generating an action or receiving an action from another agent. Multiple Security Tokens may be assigned to an agent and may be unique based on the agent's trust level or allowed privileges. Since the Security Tokens are integral for the maintanence of security in an SoC, they need to be protected properly. A common weakness afflicting Security Tokens is improperly restricting the assignment to trusted components. Consequently, an improperly protected Security Token may be able to be programmed by a malicious agent (i.e., the Security Token is mutable) to spoof the action as if it originated from a trusted agent.
+ 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)
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)
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
PeerOfBaseBase - 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.1255Comparison Logic is Vulnerable to Power Side-Channel Attacks
+ 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.

Architecture and Design
+ 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.


Class: Language-Independent (Undetermined Prevalence)

Operating Systems

Class: OS-Independent (Undetermined Prevalence)


Class: Architecture-Independent (Undetermined Prevalence)


Processor IP Class: Technology-Independent (Undetermined Prevalence)

Class: System on Chip (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.

Access Control

Technical Impact: Modify Files or Directories; Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Gain Privileges or Assume Identity; Modify Memory; Modify Memory; DoS: Crash, Exit, or Restart

+ Demonstrative Examples

Example 1

For example, consider a system with a register for storing an AES key for encryption and decryption. The key is of 128 bits implemented as a set of four 32-bit registers. The key register assets have an associated control register, AES_KEY_ACCESS_POLICY, which provides the necessary access controls. This access-policy register defines which agents may engage in a transaction, and the type of transaction, with the AES-key registers. Each bit in this 32-bit register defines a security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., “1”) allows respective action from an agent whose identity matches the number of the bit and, if “0” (i.e., Clear), disallows the respective action to that corresponding agent.

Let’s assume the system has two agents: a Main-controller and an Aux-controller. The respective Security Tokens are “1” and “2”.

Register Description Default
AES_ENC_DEC_KEY_0 AES key [0:31] for encryption or decryption 0x00000000
AES_ENC_DEC_KEY_1 AES key [32:63] for encryption or decryption 0x00000000
AES_ENC_DEC_KEY_2 AES key [64:95] for encryption or decryption 0x00000000
AES_ENC_DEC_KEY_3 AES key [96:127] for encryption or decryption 0x00000000
AES_KEY_ACCESS_POLICY AES key access register [31:0] 0x00000002

An agent with Security Token “1” has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_3 registers. As per the above access policy, the AES-Key-access policy allows access to the AES-key registers if the security Token is “1”.

(bad code)
Example Language: Other 
The Aux-controller could program its Security Token to “1” from “2”.

The SoC does not properly protect the Security Token of the agents, and, hence, the Aux-controller in the above example can spoof the transaction (i.e., send the transaction as if it is coming from the Main-controller to access the AES-Key registers)

(good code)
Example Language: Other 
The SoC needs to protect the Security Tokens. None of the agents in the SoC should have the ability to change the Security Token.
+ Potential Mitigations

Phases: Architecture and Design; Implementation

  • Security Token assignment review checks for design inconsistency and common weaknesses.
  • Security-Token definition and programming flow is tested in both pre-silicon and post-silicon testing.
+ Notes


This entry is still under development and will continue to see updates and content improvements. Currently it is expressed as a general absence of a protection mechanism as opposed to a specific mistake, and the entry's name and description could be interpreted as applying to software.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2020-03-06Arun Kanuparthi, Hareesh Khattri, Parbati Kumar Manna, Narasimha Kumar V MangipudiIntel Corporation
+ Modifications
Modification DateModifierOrganization
2020-08-20CWE Content TeamMITRE
updated Demonstrative_Examples, Description, Modes_of_Introduction, Name, Potential_Mitigations, Related_Attack_Patterns, Relationships
2021-03-15CWE Content TeamMITRE
updated Maintenance_Notes
+ Previous Entry Names
Change DatePrevious Entry Name
2020-08-20Improper Protection of Security Identifiers
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Page Last Updated: March 15, 2021