Static code analysis for security

There is a strong correlation between code quality and security: more bugs lead to more security vulnerabilities. Simple coding mistakes can cause serious security problems, like in the case of Apple’s ‘goto fail’ and OpenSSL’s ‘Heartbleed‘, highlighting the need for disciplined engineering and testing culture.

I touched upon embedding security in modern software development practices in my previous blogs on agile security and DevSecOps culture and recommended some tools to help automate managing vulnerabilities in open source libraries, help preventing committing secrets in code and integrating application security testing in the CI/CD pipeline. In this blog I would like to touch upon the connection between code quality and security and explore static code analysis.

An open source tool that is gaining a lot of momentum in this space is Semgrep. It supports multiple languages and integrates well in the CI/CD pipeline. You can run Semgrep out of a Docker container and the test results are conveniently displayed in the command line interface.

The rule set is still relatively limited compared to other established players and it might find fewer issues. You can write your own rules, however, and things are bound to improve as the tool continues to develop with contributions from the community.

A more well-known tool in this space is SonarQube. You can still use a free Community Edition for basic testing but advanced enterprise-level features would require a paid subscription. CI/CD integration is possible, inter plugins (like the one for ESLint) are also available.

SonarQube has a dashboard view which scores your code across reliability, security, maintainability and other metrics.

As with any tool of this type, to get the best use out of it, some initial configuration is required to reduce the number of false positives, so don’t be discouraged by the high number of bugs or “code smells” being discovered initially.

Keeping in mind the fact that no amount of automation can guarantee finding all the vulnerabilities, I found SonarQube’s analysis around Security Hotspots particularly interesting. It also estimates a time required to pay down the tech debt which can serve as a good indicator of maintainability of your codebase.

It is important to remember that static code analysis tools are not a substitute for the testing culture, code reviews, threat modelling and secure software engineering. They can, however, be a useful set of guardrails for engineers and act as an additional layer in your defence in depth strategy. Although these tools are unlikely to catch all the issues, they can certainly help raise awareness among software developers about quality and security improvements, alert about potential vulnerabilities before they become a problem and prevent the accumulation of tech and security debt in your company.

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