CWE-1283: Mutable Attestation or Measurement Reporting Data

What is Mutable Attestation or Measurement Reporting Data?

• Overview: This vulnerability occurs when the data used for verifying the integrity of a system's boot process can be altered by an attacker, undermining the verification process intended to ensure the system's secure startup.

• Exploitation Methods:

• Attackers can modify the register contents where the boot measurement hash is stored, allowing them to spoof legitimate measurements and disguise unauthorized changes.
• Common techniques include direct manipulation of memory registers or exploiting weak access controls to overwrite the attestation data.

• Security Impact:

• Direct consequences include the ability of attackers to bypass secure boot measures, potentially leading to the execution of unauthorized or malicious code during system startup.
• Potential cascading effects include compromised system integrity, allowing further exploitation of vulnerabilities at runtime.
• Business impact can involve data breaches, loss of customer trust, and non-compliance with security standards, leading to financial and reputational damage.

• Prevention Guidelines:

• Implement hardware-based protection mechanisms to prevent unauthorized modification of register contents, such as using Trusted Platform Modules (TPMs) or secure enclaves.
• Follow best practices in secure firmware design, ensuring that measurement registers are write-protected after initial setup.
• Use recommended tools and frameworks, such as those providing secure boot solutions and verified runtime environments, to strengthen the boot process against tampering.

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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 Attestation {
    constructor() {
        this.measurementData = {}; // Measurement data stored in an object
    }

    // Function to set measurement data
    setMeasurementData(data) {
        this.measurementData = data; // Directly assigning object makes it mutable
    }

    // Function to get measurement data
    getMeasurementData() {
        return this.measurementData; // Directly returns the mutable object
    }
}

// Example Usage
const attestation = new Attestation();
attestation.setMeasurementData({ cpu: 'Intel', ram: '16GB' });
const data = attestation.getMeasurementData();
data.cpu = 'AMD'; // Modifying measurement data externally
console.log(attestation.getMeasurementData()); // Output will reflect the change, which is a vulnerability

In this vulnerable code example, the attestation data can be modified externally after being retrieved, leading to potential security issues. The internal state is directly exposed, allowing unintended or malicious changes.

How to fix Mutable Attestation or Measurement Reporting Data?

To fix the vulnerability of mutable attestation or measurement reporting data, the best practice is to ensure data integrity through immutability. Here are some approaches:

1. Deep Copy: When setting or getting measurement data, always use a deep copy to prevent external modification. This ensures that the internal state remains unchanged even if the external reference is altered.

2. Immutable Data Structures: Use immutable data structures or libraries that enforce immutability, which can prevent accidental or malicious modifications.

3. Encapsulation: Properly encapsulate the state by not exposing internal references directly. Provide methods for controlled access and modification if necessary.

Fixed Code Example

class Attestation {
    constructor() {
        this.measurementData = {}; // Measurement data stored securely
    }

    // Function to set measurement data using a deep copy
    setMeasurementData(data) {
        // Deep copy to ensure immutability
        this.measurementData = JSON.parse(JSON.stringify(data)); 
    }

    // Function to get measurement data also using a deep copy
    getMeasurementData() {
        // Return a deep copy to prevent external modification
        return JSON.parse(JSON.stringify(this.measurementData)); 
    }
}

// Example Usage
const attestation = new Attestation();
attestation.setMeasurementData({ cpu: 'Intel', ram: '16GB' });
const data = attestation.getMeasurementData();
data.cpu = 'AMD'; // Attempt to modify copied data
console.log(attestation.getMeasurementData()); // Output will NOT reflect the change

By using a deep copy when setting and getting the measurement data, we prevent any external entity from modifying the internal state, thus fixing the CWE-1283 vulnerability. This approach maintains the integrity and authenticity of the attestation or measurement reporting data.