CWE-1315: Improper Setting of Bus Controlling Capability in Fabric End-point

What is Improper Setting of Bus Controlling Capability in Fabric End-point?

• Overview: Improper Setting of Bus Controlling Capability in Fabric End-point refers to a vulnerability where a configurable register bit in a fabric interface allows a device meant to be a responder to control transactions. This can occur if the bit is incorrectly set by default or by firmware.

• Exploitation Methods:

• Attackers can exploit this vulnerability by gaining control of a responder device and using it to initiate transactions on the fabric.
• Common attack patterns include manipulating firmware to change register settings or exploiting a default misconfiguration.

• Security Impact:

• Direct consequences include unauthorized control over data transactions between devices on the fabric.
• Potential cascading effects involve compromised data integrity and confidentiality across the system.
• Business impact could involve data breaches, loss of sensitive information, and damage to company reputation.

• Prevention Guidelines:

• Specific code-level fixes include ensuring that register bits are correctly set at design time and verified during firmware updates.
• Security best practices involve implementing strict access controls and validation checks for firmware updates.
• Recommended tools and frameworks include using security-focused static analysis tools to detect configuration issues and employing robust firmware security and update mechanisms.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not Technology-Specific

Vulnerable Code Example

class FabricController:
    def __init__(self):
        self.endpoints = []

    def add_endpoint(self, endpoint):
        # Improperly setting bus control capability without validation
        endpoint['can_control_bus'] = True  # Automatically grants control to any endpoint
        self.endpoints.append(endpoint)

# Example usage
controller = FabricController()
controller.add_endpoint({'id': 'endpoint_1'})  # Any endpoint can become a bus controller

Vulnerability Explanation:

• The add_endpoint method in this vulnerable code automatically assigns bus controlling capability (can_control_bus) to all endpoints without any validation or authorization checks.
• This flaw allows any endpoint to control bus transactions, potentially leading to unauthorized access, data corruption, or other security breaches.

How to fix Improper Setting of Bus Controlling Capability in Fabric End-point?

To securely manage bus controlling capabilities:

1. Authorization Checks: Ensure that only authorized endpoints are granted bus controlling permissions.
2. Validation Logic: Implement validation logic to verify if an endpoint should be allowed to control the bus.
3. Role-based Access: Use a role-based approach to manage permissions, ensuring that only endpoints with the appropriate role can be assigned bus controlling capabilities.
4. Logging and Monitoring: Implement logging and monitoring of endpoint configurations to detect any unauthorized changes.

Fixed Code Example

class FabricController:
    def __init__(self):
        self.endpoints = []

    def add_endpoint(self, endpoint, can_control=False):
        # Validate if the endpoint is authorized to control the bus
        if self.is_authorized(endpoint):
            endpoint['can_control_bus'] = can_control
        else:
            endpoint['can_control_bus'] = False  # Securely defaults to no control capability

        self.endpoints.append(endpoint)

    def is_authorized(self, endpoint):
        # Implement actual authorization logic
        # For demonstration, assume a simple rule based on endpoint ID
        authorized_ids = {'authorized_endpoint_1', 'authorized_endpoint_2'}
        return endpoint['id'] in authorized_ids

# Example usage
controller = FabricController()
controller.add_endpoint({'id': 'authorized_endpoint_1'}, can_control=True)  # Authorized endpoint
controller.add_endpoint({'id': 'unauthorized_endpoint'}, can_control=True)  # Unauthorized endpoint, will not control the bus

Fix Explanation:

• Authorization Check: Introduced the is_authorized method to verify if an endpoint is permitted to have bus controlling capabilities.
• Controlled Assignment: The add_endpoint method now checks if an endpoint is authorized before granting it the ability to control the bus, preventing unauthorized access.
• Secure Defaults: If an endpoint is not authorized, it is explicitly set not to control the bus, ensuring a secure default state.
• Example Usage: Demonstrates how authorized and unauthorized endpoints are handled differently, ensuring secure management of bus control capabilities.