What is Static Application Security Testing (SAST)?
Static application testing is a concept that most software developers who have worked with any IDE are familiar with. It is what gives an alert when you try to use an undefined variable, the wrong variable type, unreachable methods, among others. Static Application Security Testing (SAST) is a subcategory of these tests, focused on testing for security vulnerabilities within the code. It is also known as white-box testing because the software developer tests the underlying application code.
Why do we need SAST?
Some of the main threats that SAST will easily detect include SQL injection, input validation, cross-site scripting, buffer overflows, among others.
Several SAST tools can be used to ensure that security vulnerabilities are flagged fast and early. Some of these tools can also be easily injected into CI/CD pipelines to ensure vulnerabilities in developers’ code are not passed on to the application. Another important quality of SAST is that it can be automated to save time and increase its effectiveness.
In this article, you’ll learn about how SAST performs static analysis, its differences with DAST, the tools you can use, and the benefits of using SAST in static code analysis.
SAST vs. DAST: What’s the difference?
Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST), are both software security testing methodologies that approach the task differently.
In this section, we’ll cover the differences between SAST and DAST. We’ll also briefly discuss the use of DAST to complement SAST in static analysis.
Before we get started, let’s define DAST and understand how it works.
What is Dynamic Application Security Testing (DAST)?
DAST is performed on running web applications to help in finding runtime security vulnerabilities. It is also known as black-box testing because the software developer has no access to the underlying framework.
Some of the security issues that DAST is very good at detecting include insecure server configurations, SQL injection, and path traversal, among others.
Below are the differences between the SAST and DAST:
- Test target
SAST is performed on the code before it’s compiled while DAST is performed on software that has already been built, deployed, and running.
- Time consumed in fixing security vulnerabilities
It takes less time to fix the vulnerabilities after performing SAST. This is because the test will point you to the exact code that can potentially expose the application upon compilation. DAST takes more time to fix the vulnerabilities detected. This is because the problems are detected after the software development process is complete.
- Runtime Problems
SAST tools cannot detect security risks that are runtime-related while DAST can identify vulnerabilities that are runtime-related.
- Total time consumed while testing
SAST takes a lot of time, in total, to test and verify all the code required to compile an application. DAST, on the other hand, takes a relatively shorter time because an application is tested at once. Additionally, all the security vulnerabilities are addressed together.
- Source code requirement
DAST requires the source code to be compiled and run for it to be performed. SAST does not require the software to be run. Instead, it analyzes binaries and byte code without any executions. This is why it gives the fastest feedback.
- The number of vulnerabilities flagged
SAST will flag many segments of code that aren’t critical vulnerabilities. The developer will therefore spend a lot of time isolating real threats and false positives. DAST scans give fewer false positives compared to SAST scans.
It is important to note that vulnerabilities that are found by DAST tools aren’t always found by SAST scans.
Therefore, these two testing methodologies are complementary and will offer higher software security. This is because some security flaws will not show up until the software is in a runtime environment. On the other hand, you save time when you fix vulnerabilities as early as possible by shifting left.
The best way to utilize SAST and DAST results in the software development life cycle is to compare them and isolate the most critical vulnerabilities. For instance, if there is SQL injection or Cross-Site scripting in both reports, resolve them first. After addressing the security vulnerabilities common in both tests, you can then address the security risks only found in individual test results.
Before we move to the next section let’s briefly look at IAST.
What is interactive application security testing (IAST)?
This is a test that automatically checks for vulnerabilities in the software as the application is running. IAST works inside the application and reports the security risks in real-time. It only tests the software functionalities that are being executed by the user which is different from what SAST and DAST do.
Why companies should use SAST tools
- Allows shift-left
Shift-left is a relatively new concept that came with the agile software development methodology. It aims to create a ‘fail as fast as possible’ environment to avoid wasting time on the wrong code.
SAST is flexible and can even be done on the IDE before the developer commits changes to the source code. This shift left approach ensures that all code is tested for security vulnerabilities before getting to the source code.
It also ensures that the developer does not waste time committing suspicious changes to the source code.
- Ease of automation
It can easily be integrated into a DevOps pipeline to ensure the applications being processed are secure and sustainable. The SAST tools can be injected in the pre-commit stage, commit stage, test stage, and build stage.
- By performing SAST in the pre-commit stage, you’ll find security vulnerabilities before committing the changes to the source code repository. This also allows for the updating of the threat model when new assets or controls are included in the application.
Lastly, because it can be performed within the IDE, it can provide development teams with a limited level of instant security issues feedback as they write their code.
- Commit time testing is automated and will be triggered by changes in the source code repository. It ensures that the buildable source code is secure at all times. This is because some code snippets can be secure on their own but expose the application when added to the source code due to code dependence.
- Clear feedback
Because the test is run on code, the feedback that is given specifically points to where the security vulnerabilities are. This makes it easier for the developer to verify whether there is a need to adjust the highlighted code.
For instance, assume a line of code opens up an insecure connection to the database and doesn’t close it after fetching the data. The feedback will contain details of the exact point where the connection was opened. This will make it easier for the developer to correct the issue without having to scan many lines of code.
- Faster feedback
SAST works by checking for vulnerability patterns based on internationally recognized coding standards for quality, security, and safety. The feedback received from tests is therefore not hard to understand and in most cases can easily be corrected.
However, this makes it inadequate when working with complex APIs whose code structures are not familiar to it. It is also not very effective in testing code requiring the use of imported libraries.
- Better for collaboration
The ability to shift left makes it the best security test methodology for static codes being created by development teams. It gives every team member the ability to test what they are working on independent of the other members.
This increases their confidence because they know the likelihood of their commits being flagged by a SAST is low. It also makes the software development process more efficient.
Top 6 SAST tools
Below are the top 6 Static Application Security Testing tools currently available.
This is one of the scalable SAST solutions that only work on Java, C, C++, and C# code bases. It works well along with other IDE error checkers. It is based on coding and security standards set by CWE, OWASP, PCI DSS, STIG, CERT, ISO/IEC 17961, and DISA.
You can add to its effectiveness in static analysis by customizing the rules and checks. It can also be injected into a CI/CD pipeline for pre-commit and post-commit checks leading to more secure software.
This is a flexible and accurate static analysis tool that can find security flaws within your code and suggest possible solutions. It requires no configuration and supports multiple languages. This makes it a good place to start if you are a beginner in static code analysis.
This software as a service SAST tool flags the security threats in static code and offers possible solutions to fix them. It also has a low false-positive count compared to traditional SAST tools. Since it is offered as SaaS, the overhead of setting it up is pretty low. Additionally, it has an easy-to-use modern user interface and can also perform interactive application security testing (IAST).
The downside is that it doesn’t offer a free version for new users to try and analyze application source code for a better understanding of how it works.
This is a free open-source static analysis tool that checks and identifies OWS’s top 10 web application security flaws. The tool is updated and maintained by a community of developers. One of the advantages of this tool is that it is free to use and you can always customize it to fit your security needs.
This is a SAST tool with machine learning capability which helps in reducing the number of false positives in the SAST results. Apart from scanning and identifying the security issues, it also offers solutions to the flagged vulnerabilities. It is very robust and this makes the results it gives more reliable.
This is a shift-left security testing tool that performs SAST analysis on Node.js applications. It is a specialized tool that creates robust scenarios for testing code. The results from this tool are very reliable and can be received early in the software development process. Additionally, it can be integrated into IDEs as well as CI/CD pipelines to perform pre-commit and post-commit checks.
How to choose the right SAST tool for your organization?
There are many other Static Application Security Testing tools out there that are similar to the ones listed above or offer extra features.
Some of the factors that should be considered when choosing a SAST tool include
- Ease of operation and customization
- The number of false-positives
- Presentability of the findings
- Ease of integration with CI/CD
- Automation capabilities
Static application security testing (SAST) is very important when you want to create sustainable web applications. It can be integrated into the software development lifecycle by using it with the IDE. It can also be injected into a CI/CD pipeline in cases where the company uses the agile software development approach.
Lastly, Its effectiveness is further increased when combined with a complementary testing methodology such as DAST.