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.

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 maintenance 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.

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 Class: Not Technology-Specific (Undetermined Prevalence) Class: System on Chip (Undetermined Prevalence)

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".

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)

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