What is Static Application Security Testing (SAST)?
Static application security testing (SAST), sometimes referred to as source code analysis or static analysis, is a white box methodology for testing that analyzes application source code before it is compiled for security vulnerabilities.
According to Gartner, the term SAST represents a set of technologies created to help developers analyze binaries, byte code, and application source code to detect coding and design conditions that flag security flaws.
SAST is a commonly used application security (AppSec) tool which identifies and helps remediate underlying the root cause of security vulnerabilities. SAST tools do not need a system to be running to perform a scan because they analyze web applications from the inside out. For example, SAST testing may be used for regulatory compliance with the payment card industry data security standard (PCI/DSS), or to improve insight into software risk.
Why SAST is important
The reality is, there are far more developers than security staff. SAST tools can analyze 100% of the codebase much more rapidly than human secure code reviews. It takes only minutes for these SAST tools to scan millions of lines of code to identify critical vulnerabilities. Ultimately, these tools help organizations achieve key goals, such as:
Shift Left Security Testing
Integrating SAST into the earliest stages of software development helps shift security testing left. Detecting proprietary code vulnerabilities and other security issues during the design stage while they are easier to resolve is an important practice.
SAST readily identifies basic coding errors so development teams can easily comply with the best practices for secure coding standards.
Integrating SAST earlier in the existing CI/CD pipeline and DevOps environment saves developers from needing to trigger or separately configure scans. This makes it more efficient, convenient and easier for them to use, and eliminates the need for developers to leave their environment to conduct scans, see results, and remediate security issues.
How does SAST work?
Because it can take place without code being executed and does not require a working application, SAST takes place very early in the software development life cycle (SDLC). This helps developers quickly resolve issues and identify vulnerabilities in the project’s initial stages without passing on vulnerabilities to the final application.
SAST testing typically happens in several steps:
- Select a static analysis tool that can comprehend the underlying software framework and perform code reviews of applications written in the right programming languages.
- Create the scanning infrastructure, and take steps to deploy the tool. This includes setting up access control and authorization, handling the licensing requirements, and procuring required resources such as databases and servers for deployment.
- Customize the tool and configure it to find additional security vulnerabilities or reduce false positives by updating existing rules or writing new ones.
- Build custom reports and create dashboards for tracking scan results as you integrate the tool into the build environment.
- Prioritize high-risk applications and onboard all applications.
- Analyze and triage scan results to remove false positives, track results, and deploy results to the proper teams for timely remediation.
- Deliver robust training and the proper governance to ensure development teams employ SAST tools properly. Include SAST and software security touchpoints within the SDLC, and as part of your application development process and into deployment.
Static vs dynamic application security testing (SAST vs DAST)
There are important differences between SAST and DAST.
Static application security testing (SAST) comes early in the CI pipeline and focuses on bytecode, source code, or binary code to identify coding patterns that are problematic or conflict with best practices. Although modern SAST supports multiple programming languages, the methodology is programming-language dependent.
Dynamic application security testing (DAST) is an approach to black-box testing. Because it requires runtime to scan applications, it is applied later in the CI/CD pipeline. DAST doesn’t depend on a specific programming language so it is a good method for preventing regressions.
Consider the major differences in DAST vs SAST:
- SAST scans source code lines for vulnerabilities. In contrast, DAST works solely on the inputs and outputs from a running application and lacks any information about its code.
- Another major difference is speed, in that especially for complex running applications, a DAST tool requires some time to execute, compared to how long the SAST tool takes to scan the source code.
In practice, given the difference between SAST and DAST tools, best practices suggest using both. A SAST tool and DAST tool complement each other, and each finds vulnerabilities the other does not.
Static vs interactive application security testing (IAST vs SAST)
Like DAST, interactive application security testing (IAST) focuses on application behavior during runtime. However, IAST analysis takes more of a hybrid approach, combining analysis of internal application flows with scanning and black-box testing. IAST is most beneficial in its ability to connect source code with DAST-like findings. But this also makes IAST both programming-language dependent (as it needs to scan source code), and restricts it to being performed later in the CI/CD pipeline.
SAST vs SCA
The SCA vs SAST comparison is somewhat of an apples to oranges analogy. Software composition analysis (SCA) focuses on the application’s third-party code dependencies. In contrast, SCA tools discover all software components including all direct and indirect dependencies and supporting libraries. SCA is very useful for applications that use many open-source libraries.
How to implement SAST
In general, there are several steps to implement SAST:
- Select the cloud or on-premises for the means of deployment. The decision depends on how much control is needed, how much scalability, cost, and other factors.
- Configure and integrate SAST into the SDLC. It is possible to analyze the source code as it’s compiled, scan it as it is merged into the code base, run SAST in IDE, or simply add SAST in your CI/CD pipeline.
- Choose the extent of the SAST analysis. A complete SAST analysis is the most comprehensive and lengthy and consists of a full scan of all applications and their code. An incremental scan analyzes only changed code. A desktop configuration scans code in real time as it’s written.
Customize the process to identify new security flaws or reduce false positives by revising old rules or creating new ones. Prioritize results based on factors such as severity of threat, compliance issues, CWE, responsibility, risk level, or vulnerability.