What Is Secure Code Review? Process, Tools, and Best Practices

Secure code review is the systematic examination of software source code, with the goal of identifying and fixing security vulnerabilities.

What Is a Secure Code Review? 

Secure code review is the systematic examination of software source code, with the goal of identifying and fixing security vulnerabilities. It is becoming an integral part of the software development life cycle (SDLC) and helps improve the overall quality and security of the software. By carefully reviewing the source code, developers can detect security flaws early on, thus preventing potential breaches and attacks in the future.

Secure code reviews are not just about finding errors in the code, but also about understanding the patterns and practices that led to those errors. This involves examining the architectural design of the application, the algorithms used, the choice of data structures, and the overall coding style. By gaining insights into these aspects, developers can make more informed decisions and avoid similar mistakes in the future.

The primary objective of a secure code review is to ensure that the software complies with the best coding practices and security standards. It is a proactive approach to software development that can save time, money, and reputation by preventing security breaches and data leaks.

This is part of a series of articles about DevSecOps.

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Importance of Secure Code Review to SDLC 

In an era where software applications form the backbone of businesses, ensuring their security is paramount. This is where secure code reviews come into the picture. They serve as an essential checkpoint in the SDLC, helping detect and rectify security vulnerabilities before the software is deployed.

Implementing a secure code review in the SDLC can significantly reduce the risk of security breaches. By identifying vulnerabilities in the early stages of development, developers can fix them promptly, thus preventing potential attacks. Moreover, secure code reviews also help in maintaining code quality, as they enforce good coding practices and discourage the use of insecure or inefficient code.

Another crucial aspect of secure code review is that it fosters a culture of security within the development team. When developers are regularly involved in code reviews, they become more aware of the security implications of their code. This awareness helps them write more secure code in the future, thereby enhancing the overall security of the software.

The Secure Code Review Process 

Conducting a secure code review is not a one-time activity, but a continuous process that involves several stages. This process can be broadly divided into four stages: defining review objectives, review execution, reporting and documentation, and remediation and follow-up.

Secure Code Review Process 

Defining Review Objectives

The first step in the secure code review process is to define the objectives of the review. What are the key areas of concern? What types of vulnerabilities are we trying to detect? Answering these questions will help set the direction for the review and ensure that it is focused and effective.

This stage also involves understanding the application’s architecture and functionality, as this knowledge will guide the review process. Moreover, defining the scope of the review is also crucial, as it helps in prioritizing the code that needs to be reviewed.

Review Execution

The execution stage is where the actual code review takes place. This might involve manually reviewing source code line by line and identifying potential security vulnerabilities. The reviewers look for common security flaws such as injection attacks, cross-site scripting, insecure direct object references, and more. Alternatively, code might be reviewed by automated tools, which generate a list of discovered issues and vulnerabilities.

During the review execution, it’s important to not just focus on the vulnerabilities, but also understand the root cause of these vulnerabilities. This will help in devising effective mitigation strategies and preventing similar issues in the future.

Reporting and Documentation

Once the review is completed, the findings need to be documented and reported. This involves creating a detailed report that outlines the identified vulnerabilities, their severity, and recommended remediation steps. The report should be clear and concise, making it easy for the development team to understand and act upon the findings. Automated security testing tools can generate these reports automatically.

The report also serves as a record of the review process, providing valuable insights into the application’s security posture. It can be used for future reference and can help in tracking the progress of remediation efforts.

Remediation and Follow-Up

The final stage in the secure code review process is remediation and follow-up. Once the vulnerabilities have been identified and reported, the next step is to fix them. The development team needs to implement the recommended remediation steps and ensure that the vulnerabilities are effectively mitigated.

After the remediation is completed, a follow-up review is conducted to verify that the vulnerabilities have been properly fixed. This ensures that no loose ends are left and that the application is secure.

Tools for Secure Code Review 

Static Application Security Testing (SAST) Tools

SAST tools are designed to analyze source code at a static level, meaning they don’t require the code to be running to identify potential security issues. These tools are highly efficient for detecting common coding errors and vulnerabilities in the early stages of development, which makes them a valuable asset for any secure code review process.

SAST tools work by scanning an application’s source code line by line. They check for known patterns of insecure code, such as SQL injection, cross-site scripting, and buffer overflows. Because they analyze the code without executing it, they can detect potential security issues before the application is even run.

However, while SAST tools are efficient at detecting common vulnerabilities, they are not infallible. They can sometimes produce false positives or fail to detect more complex security vulnerabilities.

Dynamic Application Security Testing (DAST) Tools

DAST tools, on the other hand, test applications in their running state. They operate by simulating attacks on an application to identify potential vulnerabilities. This dynamic methodology allows them to detect security issues that static testing methods might miss.

Unlike SAST tools, DAST tools don’t require access to the source code. Instead, they interact with the application in the same way a potential attacker might, identifying vulnerabilities by observing the application’s responses to simulated attacks. This can make them particularly effective at identifying issues such as runtime errors and input validation errors.

However, like SAST tools, DAST tools also have their limitations. They can sometimes fail to identify hidden vulnerabilities and might also produce false positives. Furthermore, because they test applications in their running state, they can be slower and more resource-intensive than static testing methods.

Interactive Application Security Testing (IAST) Tools

IAST tools are a relatively recent addition to the secure code review toolbox. They combine aspects of both static and dynamic testing, allowing them to identify a wide range of potential security vulnerabilities.

IAST tools work by monitoring an application during its execution, identifying vulnerabilities by analyzing its behavior and data flow. This allows them to detect a variety of security issues, including those that might be missed by static or dynamic testing methods alone.

While IAST tools can provide a comprehensive secure code review, they also have their challenges. They can be complex to set up and manage, and like DAST tools, they can be resource-intensive. Furthermore, because they operate during the execution of an application, they can potentially impact its performance.

Software Composition Analysis (SCA) Tools

SCA tools are designed to analyze the components of an application, including its libraries, frameworks, and other open source components. They identify potential security vulnerabilities by checking these components against databases of known vulnerabilities.

SCA tools are particularly useful for applications that make heavy use of open source components, as these can sometimes introduce security vulnerabilities. By identifying these vulnerabilities early in the development process, SCA tools can help to ensure that an application is secure before it is deployed.

However, like other secure code review tools, SCA tools are not without their limitations. They can sometimes produce false positives, and they might not always be up to date with the latest vulnerability databases. Therefore, while they can be a valuable part of a secure code review, they should be used in conjunction with other tools and methods.

Manual Code Review Tools

Last but not least, manual code review tools are an essential part of any secure code review process. While automated tools can identify a wide range of potential vulnerabilities, they cannot replace the judgment and expertise of a human reviewer.

Manual code review tools typically include features such as syntax highlighting, code comparison, and annotation capabilities. These can make it easier for reviewers to examine code and identify potential security issues.

However, manual code reviews can be time-consuming and require a significant level of expertise. Therefore, they should be used in conjunction with automated tools to ensure a comprehensive and efficient secure code review.

Best Practices for Secure Code Review 

Creating a Secure Coding Policy

The first step towards a robust secure code review process is creating a secure coding policy. This policy provides a clear framework for developers to follow when writing code. It’s not just about listing out what programmers should and shouldn’t do—it’s about defining the principles that govern secure coding within your organization.

Your secure coding policy should be comprehensive, covering all aspects of coding—from data handling and user input validation to error handling and logging. It should also be specific to your organization’s needs and the kind of software you’re developing. For instance, if you’re dealing with sensitive user data, your policy might include strict guidelines on encryption and data protection.

It’s also crucial to remember that a secure coding policy isn’t a one-off document. As new threats emerge and technologies evolve, you’ll need to update your policy regularly. This ensures that your software remains secure against the latest security threats.

Training and Awareness for Secure Coding

Another critical aspect of secure code review is fostering a culture of security awareness among your development team. This means training your developers not just to write secure code, but to think with a security mindset. When security becomes second nature to your developers, they’ll be more likely to spot potential vulnerabilities during the coding process, reducing the risk of security flaws making it to the final product.

Training in secure coding should be regular and ongoing, and it should cover a wide range of topics—from understanding common security vulnerabilities to secure coding techniques and best practices. It’s also a good idea to provide resources for self-learning, such as online courses, webinars, and e-books. This allows developers to learn at their own pace and delve deeper into areas of interest.

Importantly, training should be practical and hands-on. This could involve code review exercises, where developers are given a piece of code and asked to identify potential security flaws, or secure coding workshops, where developers can learn new techniques and apply them in a safe environment.

Continuous Integration and Continuous Deployment (CI/CD) Security

When it comes to secure code review, it’s not just about the code—it’s also about the processes and tools you use to develop that code. One of these is continuous integration and continuous deployment (CI/CD), a development practice that involves integrating code changes regularly and deploying software quickly and efficiently.

The primary benefit of CI/CD is that it allows you to catch and fix security issues early in the development process. However, it’s crucial to ensure that your CI/CD pipeline is secure. This means implementing strong access controls, using secure configuration settings, and regularly evaluating your CI/CD tools for vulnerabilities.

It’s also important to incorporate automated security testing into your CI/CD pipeline. This involves using tools like static application security testing (SAST) and dynamic application security testing (DAST) to automatically scan your code for security flaws. Not only does this save time and resources, it also helps to ensure that no vulnerabilities slip through the cracks.

Regular Review and Updating of Practices

Finally, a crucial part of secure code review is regularly reviewing and updating your practices. This involves conducting periodic audits of your secure coding policy and training programs, assessing your CI/CD security, and staying up-to-date with the latest security trends and threats.

This regular review process allows you to identify gaps in your security practices and take steps to address them. It also ensures that your coding practices stay aligned with the evolving security landscape.

As part of this process, it’s also important to foster a culture of continuous learning and improvement. Encourage your developers to share their knowledge and experiences, and create opportunities for learning and growth.

Secure Code Review with Aqua Security

Aqua helps secure code during the review process with automated SAST scanning.

It looks at the code to identify vulnerabilities, and more importantly reduces false positives with the added context to prioritize and intelligently suggest remediation. 

Aqua SAST delivers findings directly in the developer’s IDE, so checking code is as simple as writing it and automating the scan, then leveraging suggested fixes to minimize time spent on remediation.

The Cloud Native Experts
"The Cloud Native Experts" at Aqua Security specialize in cloud technology and cybersecurity. They focus on advancing cloud-native applications, offering insights into containers, Kubernetes, and cloud infrastructure. Their work revolves around enhancing security in cloud environments and developing solutions to new challenges.