CWE-1041: Use of Redundant Code

What is Use of Redundant Code?

• Overview: Use of Redundant Code refers to the presence of multiple functions, methods, procedures, or macros within a software product that contain the same code. This redundancy complicates maintenance, potentially leading to overlooked vulnerabilities, as fixing an issue in one instance might not automatically fix it in others.

• Exploitation Methods:

• Attackers exploit this vulnerability indirectly by taking advantage of the increased likelihood of unpatched or inconsistently patched code across redundant implementations.
• Common attack patterns include targeting known vulnerabilities that may have been patched in some instances but left open in redundant code segments.

• Security Impact:

• Direct consequences include an increased likelihood of vulnerabilities remaining unpatched in some instances.
• Potential cascading effects involve prolonged exposure to security risks due to overlooked redundant code.
• Business impact may include increased maintenance costs and prolonged vulnerability exposure, which could lead to data breaches or service disruptions.

• Prevention Guidelines:

• Specific code-level fixes include refactoring to eliminate redundant code, ensuring a single source of truth for each functional logic.
• Security best practices involve regular code reviews and the use of version control systems to track changes and eliminate duplications.
• Recommended tools and frameworks include static analysis tools that can identify redundant code and refactoring tools to help consolidate duplicate logic.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

def calculate_discount(amount):
    # Redundant code: The same discount logic is repeated in multiple functions
    discount = amount * 0.1  # Calculate 10% discount
    if discount > 50:
        discount = 50
    return amount - discount

def apply_discount(amount):
    # Redundant code: The same discount logic is repeated in multiple functions
    discount = amount * 0.1  # Calculate 10% discount
    if discount > 50:
        discount = 50
    return amount - discount

Explanation

The above code demonstrates a common issue of redundant code, where the same logic for calculating a discount is repeated in multiple functions. This redundancy can lead to maintenance difficulties, as any changes to the discount logic must be made in every place the logic is repeated. This increases the risk of errors and inconsistencies, especially if the logic is updated or needs to be secured against manipulation.

How to fix Use of Redundant Code?

To resolve this issue, the discount calculation logic should be encapsulated in a single function. This adheres to the DRY (Don't Repeat Yourself) principle, which helps in maintaining consistency and ease of updates. By centralizing the logic, we also reduce the risk of errors and potential security vulnerabilities.

Fixed Code Example

def calculate_discount(amount):
    discount = compute_discount(amount)  # Use centralized function
    return amount - discount

def apply_discount(amount):
    discount = compute_discount(amount)  # Use centralized function
    return amount - discount

def compute_discount(amount):  # Centralized discount logic
    discount = amount * 0.1
    if discount > 50:
        discount = 50
    return discount

Explanation

In the fixed code, the discount calculation logic has been extracted into a single function named compute_discount(). Both calculate_discount() and apply_discount() now call this function to obtain the discount amount. This ensures that any changes to the discount logic need to be made only in one place, enhancing maintainability and reducing the likelihood of errors. This approach not only simplifies future updates but also reduces the potential for inconsistencies, thereby improving the overall security posture of the application.