CWE-622: Improper Validation of Function Hook Arguments

What is Improper Validation of Function Hook Arguments?

• Overview: Improper Validation of Function Hook Arguments (CWE-622) occurs when a product adds hooks to user-accessible API functions but fails to properly validate the arguments. This vulnerability can lead to security issues, particularly in software like antivirus or firewalls that operate with elevated privileges.

• Exploitation Methods:

• Attackers can exploit this vulnerability by passing crafted input to the hooked functions, potentially executing arbitrary code or bypassing security mechanisms.
• Common attack patterns include input manipulation, buffer overflow, and injection attacks to exploit the lack of input validation.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access, privilege escalation, and execution of malicious code.
• Potential cascading effects include system instability, data breaches, and compromise of other systems connected to the affected software.
• Business impact could involve loss of customer trust, legal ramifications, and financial losses due to data breaches or service outages.

• Prevention Guidelines:

• Specific code-level fixes include implementing thorough input validation and sanitization for all function hook arguments.
• Security best practices encompass employing the principle of least privilege, conducting regular code reviews, and using secure coding standards.
• Recommended tools and frameworks include static analysis tools to detect vulnerabilities, and security frameworks that provide input validation libraries and guidelines.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

class HookManager:
    def add_hook(self, func, *args, **kwargs):
        # Vulnerable: Arguments are passed directly to the function without validation
        func(*args, **kwargs)

def sensitive_operation(user_id):
    print(f"Performing a sensitive operation for user {user_id}")

hook_manager = HookManager()
# Improper validation could allow malicious manipulation of function arguments
hook_manager.add_hook(sensitive_operation, "admin")

Explanation:

• Vulnerability: The add_hook method directly passes user-provided arguments to the hooked function without any validation. This opens the door for unintended or malicious values to be passed, potentially leading to security issues like unauthorized access. For instance, if the sensitive_operation function expects a specific user ID format, passing arbitrary strings could lead to unauthorized actions being performed.

How to fix Improper Validation of Function Hook Arguments?

To fix this vulnerability, it's crucial to implement strict validation and sanitization of all user-supplied arguments before they are passed to the function hooks. This can be achieved by:

1. Implementing input validation: Check that all arguments meet expected formats, types, and constraints.
2. Using whitelists: Define valid values or patterns that arguments should conform to, rejecting anything that doesn't match.
3. Applying least privilege principles: Ensure that hooked functions only receive the minimal data necessary for operation.

Fixed Code Example

class HookManager:
    def add_hook(self, func, *args, **kwargs):
        # Fixed: Validate arguments before passing them to the function
        if self.validate_args(func, *args, **kwargs):
            func(*args, **kwargs)
        else:
            raise ValueError("Invalid arguments provided to hook")

    def validate_args(self, func, *args, **kwargs):
        # Example validation: Ensure user_id conforms to expected type and value
        if func == sensitive_operation:
            user_id = args[0]
            # Simple validation: user_id must be a non-empty string
            return isinstance(user_id, str) and len(user_id) > 0
        return False

def sensitive_operation(user_id):
    print(f"Performing a sensitive operation for user {user_id}")

hook_manager = HookManager()
# Now arguments are validated before being used in sensitive operations
hook_manager.add_hook(sensitive_operation, "admin")

Explanation:

• Fix Implementation: The HookManager now includes a validate_args method that ensures arguments are valid before they are used. In this example, we validate that user_id is a non-empty string which is appropriate for the sensitive_operation function. This prevents unauthorized access by ensuring only valid user IDs are processed.
• Security Control: This approach prevents unauthorized or malformed inputs from being processed, reducing the risk of security vulnerabilities. By implementing input validation, we ensure that only expected and safe data is passed to sensitive operations.