Krampus - Building a custom DAST that actually works

When doing application security for an API–centric enterprise spanning over thousands of micro services, Dynamic Application Security Testing (DAST) is almost a must-have. However, DAST products often fail to execute even the most rudimentary tests on internal endpoints that require a complex user flow. If an API call requires an ID that was obtained in the response BODY 5 HTTP calls ago, the chances a traditional DAST will be able to test your API are slim.In this talk we’ll present our approach for solving this issue, by leveraging existing headless-chrome test suites (built by the engineers as part of the R&D flow) to serve as the attack surface for our custom DAST solution, Krampus. By using Chromium interceptors, we were able to introduce appsec payloads into HTTP requests issued during the execution of normal 'user flow' test scenarios (and pick up the results) and have an effective DAST for internal API's and endpoints.It wasn't smooth sailing, though, with many challenges along the way. Particularly, we realized that replicating each API call & param with a separate test will mean that the number of our test calls grows exponentially, pushing up both cost and overhead. As many of our API’s also include dynamic params as part of the path, we had to build an API asset DB to understand if and when a specific URL was already tested (code for which we plan to release as open source).At the end of the talk the participants will have the tools to leverage similar testing suites in their own orgs to drastically improve the quality & coverage of the automatic testing in their environment.