What is Static Application Security Testing (SAST) and how does it work?

What is SAST?

Static Application Security Testing (SAST), or static analysis, is a method of testing and analysing source code. This method allows organisations to analyse their source code and detect vulnerabilities that could make their applications prone to attacks.

This methodology has been used in application security for over 15 years and is especially useful for helping developers spot possible security weaknesses in the early stages of software development.

Learn more about the different types of AppSec tools and how SAST fits into the mix

How Does SAST Work?

As the ‘static’ in the name implies, SAST tests work with static code (code at rest). This means you don’t have to run the code to test for any vulnerabilities.

These are the 6 steps to a SAST test:

• Tool finalisation - Select a static analysis tool that can review your programming language.  

• Infrastructure and tool deployment - Create the scanning infrastructure. This includes licensing, authorization, and resource procurement. 

• Tool customisation -  Make custom tweaks to the tool according to your software needs. This could include decreasing false positives or discovering other security vulnerabilities by writing new rules or updating current ones.  You can also fine-tune the tool to suit your organization’s needs.

• Prioritisation and onboard application - When the tool is prepared, onboard your applications, prioritizing the high-risk applications first. Eventually, every application should be onboarded and regularly scanned.

• Analyse scan results - Filter out the false positives. Once they’re removed the results should be handed to the deployment team for remediation.

• Governance and training - Ensure the scanning tools are being used properly. SAST should be included in your application development process.

Remember: the best time to implement SAST is during the early stages of development. However, it’s important to note that SAST tools should be an integral part of an ongoing process. SAST scans should be employed regularly, such as every time code is checked in, or during a code release.

What Kind of Vulnerabilities can SAST Tools Detect?

Some of the most common flaws encountered by SAST scans are:

• SQL injection: These attacks consist of malicious SQL queries inserted into an application through user input. An injection can modify or read information from a database, alter permissions or even extend commands to the operating system itself.
  
  
• Input validation: Similar to SQL injections, systems should have some form of input validation to catch any potential injections or other malicious code. This parses information provided by users and filters it before being accepted by the system.
  
  
• Stack buffer overflows: A classic exploit that is still a popular target today, these occur when a program tries to accept more data than it can. This can lead to crashes, data corruption, or malicious code being run.

Advantages of SAST Tools 

SAST tools are a great way of shifting security left. Shifting left means security testing starts from the beginning of the development process instead of implementing scans later on.

The earlier you start testing the better. If you find your security weaknesses right from the start of your design stage, the effort it will take to fix them will be greatly reduced when compared to late-stage testing.

The worst-case scenario is finding security flaws very close to, or even after, the release date, which often means added stress and costs.

DISADVANTAGES OF SAST TOOLS

While SAST may be an excellent methodology, it still has flaws that you should be aware of.

The most significant disadvantage of using SAST tools is that they only run on static code, meaning that they can’t find runtime issues or bugs that may only appear after the code has been compiled. This can also become a bigger issue if you don’t have access to the source code of a product you might be using or rely on many dependencies.

SAST tools also typically only support one language, meaning that you’ll need to rely on more than one tool in most cases. This can lead to many overhead costs or time spent configuring multiple tools, especially if you rely on more than one programming language.

The final notable disadvantage is that SAST tools don’t work well within a microservice architecture. This can be a significant issue, as this architecture is popular among most organisations. 

If you’re looking to incorporate application testing, SAST is a fantastic start. However, by solely using this type of testing you’re unlikely to meet the highest level of security your applications require. Application Security Orchestration & Correlation tools, such as Uleska, can incorporate SAST and other application security tools to offer you a complete automated package.

SAST vs DAST

While SAST can detect vulnerabilities without running the code, DAST (Dynamic Application Security Testing) can find them in a running application.

While SAST testing is completed by the developers themselves or by someone who has access to the code, DASTs are conducted from the outside in, with the tester being unaware of which technologies and frameworks compose the software. SAST is a type of white-box testing, which is often referred to as the developer approach, while DAST is a type of black-box testing, often described as the hacker approach.

DAST works by deploying fault injection techniques on an application, such as sending malicious data to the software to identify common security issues.  Another great feature of DAST is discovering problems related to runtime, something which isn’t possible with SAST.

In most cases, organisations should be utilising both SAST and DAST tools. This allows for the most coverage possible, with a wide net to catch any issues that may arise in development. However, in some cases you may want to only rely on one, in which case you’d need to weigh each individual method.

As both SAST and DAST have their own set of advantages and disadvantages, they’re often used in tandem. SAST won’t discover runtime errors, whilst DAST fails to flag coding errors.

BEST SAST TOOLS

There are several options for SAST tools to be incorporated into your SDLC. Here's a quick list to get you started:

GitLab offers an ideal SAST tool with any tier of their CI/CD product, with extensive documentation. They provide a fantastic platform for not only a CI/CD pipeline, but also a robust version control system that is entirely open-source.

Veracode advertises a speedy tool with quick SAST scans of around 90 seconds (on average). They also offer a low rate of false positives and a rapid setup speed, so your teams can get up and running as fast as possible. They also support over 25 different programming languages to fit almost any organisation.

WhiteSource also boasts a fast product, with their SAST tool claiming to be ten times faster than traditional SAST solutions. Their product is also run entirely locally, so you don’t need to upload your source code to the cloud. WhiteSource also supports more than 27 different programming languages, putting them on par with Veracode.

Conclusion

If you’re a developer interested in SAST testing, the tools mentioned in this article are a great place to start. Try to implement them as early as possible in your SDLC, as they will allow you to catch potential issues early in development, before they get out of hand. 

In today’s world, it is strongly recommended to include security testing in your application development. By using SAST and DAST together, you can benefit from a fast and effective approach to creating more secure applications.  

Who is Uleska?

Uleska helps security and development teams manage application security at scale by automating and orchestrating their preferred security tools within CI/CD.

With Uleska, teams can confidently start an AppSec program using open-source, commercial, and custom tools and then quickly change, add or scale tools as the technology and business needs evolve. Uleska also brings speed and scale when integrating into development tools, and reporting of metrics and risk.

By bringing security, DevOps and development teams together, we help reduce manual tasks so application security takes less time, cost and can scale, allowing teams to focus resources on the issues and metrics that matter.