CWE-1291: Public Key Re-Use for Signing both Debug and Production Code

What is Public Key Re-Use for Signing both Debug and Production Code?

• Overview: The vulnerability occurs when the same public key is used to sign both debug and production code, risking exposure of debug capabilities in production environments.

• Exploitation Methods:

• Attackers can exploit leaked debug firmware signed with the same key to access production systems.
• Common attack patterns include using leaked keys to run debug firmware on production hardware, revealing internal functionality and bypassing security controls.

• Security Impact:

• Direct consequences include unauthorized access to production systems' debug features.
• Potential cascading effects include system compromise, data theft, and unauthorized modifications.
• Business impact could involve intellectual property theft, system downtime, and reputational damage.

• Prevention Guidelines:

• Use distinct public keys for signing debug and production code.
• Implement strict key management practices to prevent leakage.
• Employ code-signing tools and frameworks that support separate key usage for different environments, ensuring proper key rotation and lifecycle management.

Corgea can automatically detect and fix Public Key Re-Use for Signing both Debug and Production Code in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not Technology-Specific

Vulnerable Code Example

from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding, rsa

# Load a single public key for verifying both debug and production signatures
with open("public_key.pem", "rb") as key_file:
    public_key = serialization.load_pem_public_key(key_file.read())

def verify_signature(data, signature, debug=False):
    try:
        if debug:
            # Debug verification
            public_key.verify(
                signature,
                data,
                padding.PSS(
                    mgf=padding.MGF1(hashes.SHA256()),
                    salt_length=padding.PSS.MAX_LENGTH
                ),
                hashes.SHA256()
            )
            print("Debug signature verified.")
        else:
            # Production verification
            public_key.verify(
                signature,
                data,
                padding.PSS(
                    mgf=padding.MGF1(hashes.SHA256()),
                    salt_length=padding.PSS.MAX_LENGTH
                ),
                hashes.SHA256()
            )
            print("Production signature verified.")
    except Exception as e:
        print("Verification failed:", e)

Explanation:

• Vulnerability: The same public key {8-10} is used for verifying both debug and production signatures. If the debug environment is compromised, attackers could potentially use the same key to verify malicious code in the production environment.

How to fix Public Key Re-Use for Signing both Debug and Production Code?

To fix this vulnerability, separate keys should be used for different environments. This ensures that if one key is compromised (e.g., the debug key), it does not affect the security of the production environment. Here are the steps to address this issue:

1. Use Separate Keys: Generate and use separate public keys for verifying debug and production signatures.
2. Secure Storage: Store keys securely and restrict access to production keys to only necessary personnel or systems.

Fixed Code Example

from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding, rsa

# Load separate public keys for verifying debug and production signatures
with open("debug_public_key.pem", "rb") as debug_key_file:
    debug_public_key = serialization.load_pem_public_key(debug_key_file.read())

with open("production_public_key.pem", "rb") as prod_key_file:
    production_public_key = serialization.load_pem_public_key(prod_key_file.read())

def verify_signature(data, signature, debug=False):
    try:
        if debug:
            # Use the debug public key for verification
            debug_public_key.verify(
                signature,
                data,
                padding.PSS(
                    mgf=padding.MGF1(hashes.SHA256()),
                    salt_length=padding.PSS.MAX_LENGTH
                ),
                hashes.SHA256()
            )
            print("Debug signature verified.")
        else:
            # Use the production public key for verification
            production_public_key.verify(
                signature,
                data,
                padding.PSS(
                    mgf=padding.MGF1(hashes.SHA256()),
                    salt_length=padding.PSS.MAX_LENGTH
                ),
                hashes.SHA256()
            )
            print("Production signature verified.")
    except Exception as e:
        print("Verification failed:", e)

Explanation:

• Fixed Lines: Separate public keys {8-16} are loaded for debug and production, ensuring that each environment is independently secure.
• Security Controls:
  • The debug and production environments have distinct keys {18-20, 23-25}, minimizing risk if one is compromised.
  • Proper key management practices should be implemented to ensure keys are stored securely and access is controlled.
• Code Improvement: The function name is changed to verify_signature to clarify its purpose, and exception handling is added to manage verification failures gracefully.