SAST: A guide to static application security testing

Development teams use static application security testing (SAST) to identify and address potential security vulnerabilities in their source code. Using SAST early in development identifies threats well before they can affect a live environment.

SAST is particularly important for CI/CD pipelines. These pipelines automate the integration of new code changes into the main codebase and deploy applications to production environments. SAST detects vulnerable code before it is pushed through CI/CD pipelines. This early detection leads to faster remediation and reduced risk.

The combination of speed and safety that SAST provides means that software projects can meet both performance objectives and security standards. Development teams can build and deploy applications confidently, because they know their code is ready for the production environment. SAST benefits organizations by allowing the early detection of security vulnerabilities and code flaws, minimizing the risk of security breaches in deployed applications.

This article introduces the concept of SAST and explores its role in software development. It also explains how CircleCI features can help facilitate SAST to improve overall application security.

What is SAST?

SAST is a type of security testing that involves static analysis, which means analyzing application code without executing it. This method is also known as open-box testing because it requires full visibility into the application’s architecture, including source code, configuration files, and dependencies.

SAST tools scan the code to detect potential security vulnerabilities, such as buffer overflows, SQL injection flaws, and cross-site scripting (XSS) vulnerabilities at an early stage in the software development lifecycle.

There are three main types of SAST scans that identify potential security risks:

• Source code scans analyze the application’s source code, identifying vulnerabilities based on known patterns or insecure coding practices.
• Bytecode scans focus on compiled bytecode, which is platform-independent code generated from source code. Bytecode scans are particularly useful for languages like Java or C# that compile to an intermediate form.
• Binary code scans analyze the machine-executable code generated by compiling source code. Binary scans are essential for languages that compile directly to machine code, such as C or C++.

Using these different types of SAST scans, organizations can ensure comprehensive coverage across various stages of the software development process.

Why is SAST important?

SAST allows developers to identify and address security flaws during development, reducing the risk of deploying vulnerable code in production. This proactive approach bn helps maintain the integrity of the software and protects against breaches that could compromise user data and system functionalities. It also saves development teams from long and costly rework by catching security flaws early, before they are integrated with the rest of the product.

The harmonization of speed and safety facilitated by SAST ensures that software projects meet both performance objectives and security standards. Development teams can build and deploy applications confidently, knowing that their code has undergone thorough analysis and is ready for the rigors of the production environment.

SAST is particularly effective when paired with continuous integration and continuous deployment (CI/CD) pipelines. These pipelines automate the integration of new code changes into the main codebase and deploy applications to production environments. SAST detects insecure code before it is pushed through CI/CD pipelines, which leads to faster remediation and reduced risk.

How does SAST work?

SAST tools are designed to parse the code to construct an abstract syntax tree (AST), which helps the tool understand the structure of the code and identify potential security issues based on predefined rules and patterns.

Here’s a step-by-step breakdown of how SAST typically operates:

1. Code input: Developers feed the source code, bytecode, or binary code into the SAST tool. This can be done manually or automatically as part of a CI/CD workflow.

2. Code parsing: The SAST tool parses the code to create an AST, which allows it to analyze the structural and logical flow of the code without running it.

3. Vulnerability detection: Using a set of predefined rules and patterns, the tool scans the abstract representation to identify potential security vulnerabilities. The tool may also incorporate semantic analysis to understand the context and potential implications of each piece of code.

4. Reporting: Once the analysis is complete, the SAST tool generates a report detailing the vulnerabilities found, often with severity ratings and recommendations for remediation. This report can be used by developers to understand where security issues exist and how to fix them.

5. Integration with development tools: Many SAST tools are designed to integrate seamlessly into integrated development environments (IDEs), continuous integration (CI) tools, and other software development tools. This integration allows for real-time feedback and alerts about security issues, enabling developers to address them as part of their regular coding workflow.

The effectiveness of SAST lies in its ability to provide a comprehensive security overview of the code from within, highlighting problematic areas before the code is compiled or run.

Benefits of implementing static application security testing

This section details some of the benefits that SAST provides:

• Detecting and mitigating security vulnerabilities
• Creating a more secure supply chain
• Supporting regulatory compliance

Detect and mitigate vulnerabilities sooner

One of the most significant advantages of static application security testing is its ability to identify vulnerabilities early in software development. This early detection not only enhances the application’s security posture but also saves time and resources by preventing extensive and costly repairs later on.

Create a more secure supply chain

With applications becoming more interconnected and reliant on third-party components, eliminating vulnerabilities as soon as possible is crucial to mitigate the risk of data breaches and other cyberattacks. Insecure software supply chains increase your risk exposure by compromising the integrity of software components, introducing vulnerabilities that can be exploited by malicious actors.

SAST secures the software supply chain by analyzing proprietary and third-party code components. It helps ensure that all components within an application, whether developed in-house or obtained from external sources, are free from vulnerabilities that can hinder its security. This comprehensive approach to security testing enables organizations to maintain a secure software supply chain, reducing the risk of vulnerabilities being introduced via third-party code.

Support regulatory compliance

In addition to enhancing application security, static application security testing helps organizations meet compliance requirements and adhere to industry standards. If you have specific security regulations and guidelines to meet, such as the Payment Card Industry Data Security Standard (PCI DSS) or Health Insurance Portability and Accountability Act (HIPAA), implementing SAST tools can help you maintain compliance with these standards.

You can configure your SAST tools to check for compliance with the relevant regulatory standards. Demonstrating adherence to industry standards and compliance requirements allows you to build trust with your customers, partners, and regulators.

Automating static application security testing with CI/CD

SAST tools accommodate a variety of programming languages and frameworks. To get the most out of static application security testing, though, you should integrate these tools into your CI/CD pipeline.

CircleCI offers easy CI/CD pipeline integration with several DevOps security tools, including SonarQube, Fortify, Checkmarx, and Veracode, which support languages like Java, C#, JavaScript, Python, PHP, .NET, and C/C++. These integrations allow developers to automate SAST scans and receive immediate feedback on identified vulnerabilities, enabling swift mitigation.

CircleCI orbs are reusable packages of YAML configuration that simplify the integration of third-party tools, like SAST solutions, into your CI/CD pipeline. Through CircleCI orbs, developers can quickly automate SAST scans and ensure consistent security testing throughout the development process.

To integrate SAST scans into your CI/CD pipeline using CircleCI orbs, follow these steps:

1. Browse the CircleCI orb registry to find the desired SAST tool’s orb.
2. Add the selected orb under the orbs section in your project’s .circleci/config.yml file, providing it with an alias.
3. Configure the desired SAST tool’s settings by adding the necessary parameters to the orb, as described in the orb’s documentation.
4. Add the SAST orb as a step within a job in your CI/CD pipeline. This will execute the SAST scan automatically every time new code is committed.

Incorporating SAST into a CI/CD pipeline usually means adding a SAST tool as a step in the build process. This step ensures that the SAST scan automatically executes every time new code is committed, providing immediate feedback on potential security issues. Integrating SAST into the pipeline has a positive impact on the development workflow, because it:

• Helps developers address security issues early in the development process, which reduces the risk of vulnerabilities being pushed to production.
• Streamlines the security testing process by automating scans and eliminating the need for manual testing.
• Ensures consistency in security testing by running scans with every code commit, providing a continuous feedback loop that helps maintain a high level of security across the application.

Static application security testing and DevSecOps

While SAST is an essential component of a robust security program, it alone cannot guarantee complete software security. A comprehensive security strategy involves multiple layers of protection, each addressing different aspects of application security.

Relying solely on SAST for software security has limitations:

• It focuses on analyzing the application’s source code, bytecode, or binary code, which means it may not detect vulnerabilities arising from runtime interactions or external factors.
• SAST tools can produce false positives, causing you to waste resources trying to resolve nonexistent issues.
• It typically does not cover vulnerabilities related to an application’s configuration, deployment, or operational aspects.

A comprehensive DevSecOps pipeline adopts a holistic approach to application security, integrating various testing methodologies and practices. Key components include:

• SAST for identifying potential vulnerabilities during development.
• Dynamic application security testing (DAST) for detecting runtime vulnerabilities.
• Interactive application security testing (IAST) for real-time feedback on security issues. IAST covers monitoring and observability for proactive issue resolution, secure secrets handling for sensitive information management, and continuous security updates and patch management to reduce exposure to known vulnerabilities.

Conclusion

Static application security testing plays a crucial role in modern software development, particularly in the context of CI/CD pipelines. It helps developers identify and address potential vulnerabilities earlier, which reduces the risk of vulnerabilities emerging in deployed applications.

By integrating SAST tools into CI/CD pipelines, you can ensure consistent security testing throughout the development lifecycle, ultimately enhancing the security posture of your application.

Keep in mind that SAST is only one component of a comprehensive security program. A complete DevSecOps pipeline includes multiple layers of protection, addressing important aspects of application security through techniques like DAST, IAST, monitoring and observability, secure secrets handling, and continuous security updates and patch management.

To start implementing SAST in your development pipeline, sign up for a free CircleCI account and learn more about our available security integrations.