CWE-1431: Driving Intermediate Cryptographic State/Results to Hardware Module Outputs

What is Driving Intermediate Cryptographic State/Results to Hardware Module Outputs?

• Overview: This vulnerability occurs when a hardware module used for cryptographic operations inadvertently exposes sensitive intermediate states or results through its output, which can be accessed by unauthorized parties.

• Exploitation Methods:

• Attackers can monitor the hardware module's output to capture sensitive cryptographic information.
• Common attack patterns include side-channel attacks, where attackers infer cryptographic keys by analyzing output data patterns.

• Security Impact:

• Direct consequences include the exposure of sensitive cryptographic keys or data.
• Potential cascading effects include the decryption of confidential information or unauthorized access to secure systems.
• Business impact can range from loss of data confidentiality to reputational damage and financial losses.

• Prevention Guidelines:

• Specific code-level fixes include ensuring that intermediate cryptographic states are not outputted or are obfuscated.
• Security best practices involve regular security audits and testing of cryptographic modules.
• Recommended tools and frameworks include those that provide secure cryptographic operations and have been vetted for information leakage vulnerabilities, such as those compliant with FIPS 140-2 or higher.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: System on Chip

Vulnerable Code Example

import hashlib

def insecure_hash(input_data):
    # Simulate intermediate cryptographic state
    intermediate_state = hashlib.sha256(input_data.encode()).digest()[:16]  # Extract part of the hash as intermediate state
    
    # Vulnerable: Intermediate state is output directly
    print("Intermediate state (vulnerable):", intermediate_state)  # This exposes sensitive information
    
    # Final cryptographic result
    final_result = hashlib.sha256(intermediate_state).hexdigest()
    return final_result

data = "sensitive information"
print("Hash:", insecure_hash(data))

Explanation:

• Line {12}: The code computes an intermediate cryptographic state during a hash operation. This state is a partial result of the hashing process.
• Line {13}: This intermediate state is exposed directly through a print statement, potentially leaking sensitive information that could be exploited by attackers if intercepted.

How to fix Driving Intermediate Cryptographic State/Results to Hardware Module Outputs?

To address this vulnerability, ensure that intermediate cryptographic states are not exposed outside of their intended use. Instead of making these states accessible via outputs like print statements or logs, handle them internally and securely. This protects against potential information leakage that could be exploited by attackers.

Specific Fixes:

1. Avoid exposing intermediate cryptographic states through outputs like print statements or logs.
2. Restrict access to cryptographic operations and results to trusted components of the system.

Fixed Code Example

import hashlib

def secure_hash(input_data):
    # Compute intermediate cryptographic state (kept internal)
    intermediate_state = hashlib.sha256(input_data.encode()).digest()[:16]  # Intermediate state is not exposed
    
    # Secure: Intermediate state is not output
    # Removed the print statement that exposed the intermediate state
    
    # Final cryptographic result
    final_result = hashlib.sha256(intermediate_state).hexdigest()  # Final result is securely derived from intermediate state
    return final_result

data = "sensitive information"
print("Hash:", secure_hash(data))

Explanation:

• Line {12}: The intermediate cryptographic state is computed but kept internal to the function. It is not exposed to any external output.
• Line {15}: The final result is computed from the intermediate state without exposing the intermediate state itself. This ensures that no sensitive data about the cryptographic process is leaked, maintaining the integrity and confidentiality of the cryptographic operations.