CWE-1231: Improper Prevention of Lock Bit Modification

What is Improper Prevention of Lock Bit Modification?

• Overview: CWE-1231 refers to a vulnerability where a product uses a lock bit to restrict access to certain resources, but fails to prevent this lock bit from being modified after it is set. This can occur in hardware and integrated circuits, allowing unauthorized access to protected areas.

• Exploitation Methods:

• Attackers can exploit this vulnerability by modifying or clearing the lock bit after it is set, potentially using unprotected software interfaces or exploiting design flaws.
• Common attack patterns include buffer overflows, input validation failures, or exploiting weak access controls that allow manipulation of the lock bit.

• Security Impact:

• Direct consequences include unauthorized access to protected registers or resources, leading to potential system compromise.
• Potential cascading effects involve unlocking critical system features, altering device configurations, or introducing malicious firmware.
• Business impact could include loss of intellectual property, system downtime, reputational damage, and non-compliance with security regulations.

• Prevention Guidelines:

• Specific code-level fixes include implementing strict access controls and input validation to prevent unauthorized modifications of the lock bit.
• Security best practices involve ensuring the lock bit is set early during system initialization and implementing hardware-based protections to prevent its modification.
• Recommended tools and frameworks include using static code analysis tools to identify potential vulnerabilities and adopting secure coding standards to mitigate risks.

Corgea can automatically detect and fix Improper Prevention of Lock Bit Modification 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

class LockManager:
    def __init__(self):
        self.lock_bit = False  # Lock bit initially set to False

    def lock_resource(self):
        self.lock_bit = True  # Lock the resource by setting the lock bit

    def unlock_resource(self):
        self.lock_bit = False  # Improperly allows the lock bit to be reset without restrictions

lock_manager = LockManager()
lock_manager.lock_resource()
# ... some operations ...
lock_manager.unlock_resource()  # Improperly unlocking the resource without any checks

Explanation:

• In this example, a LockManager class is responsible for managing access to a hypothetical resource.
• The lock_resource method sets a lock_bit to True, indicating that the resource is locked.
• However, the unlock_resource method can reset the lock_bit to False without any checks or restrictions, allowing unauthorized modifications.
• This lack of control over the lock bit can lead to unauthorized access or modification of the resource.

How to fix Improper Prevention of Lock Bit Modification?

To fix this vulnerability, implement strict controls over the modification of the lock bit. Consider the following best practices:

1. Immutable Lock Bit: Once the lock bit is set, it should not be changed unless specific conditions are met.
2. Authorization Check: Implement checks to ensure only authorized entities can modify the lock bit.
3. Logging and Monitoring: Log any attempts to modify the lock bit for audit purposes.
4. Use Secure Methods: Encapsulate the lock/unlock operations in secure methods with necessary checks.

Fixed Code Example

class LockManager:
    def __init__(self):
        self._lock_bit = False  # Use a private attribute for the lock bit

    def lock_resource(self):
        self._lock_bit = True  # Lock the resource by setting the lock bit

    def unlock_resource(self, auth_token):
        if self.is_authorized(auth_token):  # Check authorization before unlocking
            self._lock_bit = False
            print("Resource has been unlocked.")
        else:
            print("Unauthorized attempt to unlock the resource.")
            # Log unauthorized attempt for audit purposes

    def is_authorized(self, auth_token):
        # Assume a function to verify if the auth_token is valid
        # For demonstration, let's say it returns True for a specific token
        return auth_token == "VALID_TOKEN"

lock_manager = LockManager()
lock_manager.lock_resource()
# ... some operations ...
lock_manager.unlock_resource("VALID_TOKEN")  # Now requires an authorization token

Explanation:

• The lock_bit is now a private attribute (_lock_bit) to prevent direct modification from outside the class.
• The unlock_resource method requires an auth_token parameter, ensuring that only authorized entities can change the lock state.
• Unauthorized attempts to unlock the resource are logged and reported, enhancing security and traceability.
• The is_authorized method is a placeholder for a robust authorization mechanism, ensuring only authorized entities can modify the lock bit.