Explanation of Secure Code Review

Table of contents

Prologue

Code review is a very effective technique for identifying security flaws. Code review along with manual penetration testing and automated tools can contribute to the cost effectiveness of an application security verification effort significantly.

What is the Significance of Secure Code

• With the advancements connectivity, technologies and protocols, developers can make mistakes in numerous way and can lead to security related problems and have become very crucial in the recent years.

• It can be observed that the ability to invent technology has outstripped the ability to secure it.

• It is not easy to distinguish good code from insecure code since software is essentially just a black-box.

What is Secure Code Review

• Secure code review is of paramount importance in the world of software development and cybersecurity.
• It refers to the practice of writing code in a way that minimizes vulnerabilities and weaknesses, making software less susceptible to security breaches, data leaks, and other malicious activities.
• Code review helps ensure that the application has been developed in such as way that it is capable of being “self-defending” in the environment it is meant for.

A general rule of thumb is that a penetration test should not uncover any additional application vulnerabilities in the developed code once the application has undergone a proper security code review.

Code Review Preparation and Practices

Code review preparation is a critical step in ensuring a successful and productive code review process. Proper preparation helps both the author of the code and the reviewers help to identify and address issues efficiently.

Here are some essential steps to prepare for a code review:

• Understand the Purpose and Scope :

  • Clearly define the purpose of the code review, whether it’s for finding defects, improving code quality, or ensuring adherence to coding standards.
  • Determine the scope of the review, which specific files or components will be reviewed, and any specific focus areas.

• Review Your Code First :

  • Before submitting your code for review, conduct a thorough self-review. Look for common coding issues, logic errors, and adherence to coding standards.
  • Try to fix any obvious problems and make your code as clean and functional as possible.

• Documentation :

  • Ensure that your code is well-documented, including comments explaining the purpose of functions, classes, and complex code blocks.
  • Provide any necessary background information, context, and reasoning for design decisions.

• Code Style and Standards :

  • Follow coding conventions and style guidelines relevant to the project or organization.

• Testing :

  • Ensure that your code has been thoroughly tested, including unit tests, integration tests, and any relevant regression tests.
  • If the project follows a test-driven development (TDD) approach, it is important that the tests pass.

• Check for Known Issues :

  • Use static code analysis tools and linters to catch common coding issues and adhere to best practices.
  • Check for any code smells or anti-patterns and try to refactor them before the review.

• Functional Testing :

  • If possible, conduct functional testing to ensure that the changes do not introduce new bugs or regressions in the application’s behavior.

• Commit Messages :

  • Write clear and informative commit messages that summarize the purpose and impact of each commit. This helps reviewers understand the context of your changes.

• Be Open to Feedback :

  • The goal of the code review is to improve the code so it is important to be open to the constructive criticism.

• Collaborative Environment :

  • Foster a collaborative environment where reviewers and authors work together to enhance code quality.

• Iterative Improvement :

  • Use the feedback from code reviews as a learning opportunity. Apply the lessons learned in future code development to continually improve your coding skills.

Agile SDLC Secure Code Review Example

Planning ~

1. Identify Security Stakeholder Stories
2. Identify Security Controls
3. Identify Security Test Cases

Sprints ~

1. Secure Coding
2. Security Test Cases
3. Peer Review (including security code review)
4. Penetration Testing (high risk or with major releases)

Deployment ~

1. Secure Configuration Management
2. Secure Deployment

Secure Development Metrics

1. Defect Density : It refers to a measurement that calculates the number of security defects or vulnerabilities found in a piece of code relative to a specific unit of measurement, typically lines of code (LoC).

The formula for calculating defect density is as follows:

Defect Density = Number of Security Defects
                -----------------------------
                Total Lines of Code (LoC) or Function Points (FP)

Where

• Number of Security Defects is the total count of identified security vulnerabilities, weaknesses, or issues found during a code review or security assessment.
• The denominator lines of code (LoC) or function points (FP), represents the size of the codebase under review.

2. Function Point : The estimation of software size by measuring functionality. It includes a combination of a number of statements performing a specific task, independent of the underlying programming languages or development methodology.

3. Risk Density : Similar to defect density, but issues discovered are rated by risk (high, medium & low).

This can be used to gain insight into the quality of the code being developed through a

[X Risk / LoC] 
or
[Y Risk / Function Point] value.

(X&Y being high, medium or low risks) as defined by internal application development policies and standards.

Benefits of Secure Code Review

• Security Defects (Vulnerabilities) are identified early
• Reliable code base
• Technical architecture/library related issues can be resolved early

Scope & Ownership of Secure Code Review

What to review on priority

• Critical components
• Reusable code
• Interface code

When to review code for security

• Initial prototype
• Before major release & production release
• When application code is stable

Who to review code for security

• Technical architects
• Developers

Final Takeaway

Secure code reviews are essential for building resilient software systems and protecting against security threats. They complement other security practices like penetration testing and vulnerability scanning, providing a proactive means of identifying and addressing security issues early in the development process, which ultimately leads to more secure and reliable software.