DevSecOps Decisioning Principles

I know you’ve heard this before, but DevOps is not about tools. At its core, DevOps is really a supply chain for efficiently delivering software. At various stages of the process, you need testing and validation to ensure the delivery of a quality product. With that in mind, DevSecOps should adhere to certain principles to best support the automated SDLC process. To this end, I’ve developed a set of fundamental propositions for the practice of good DevSecOps.

  • Security tools should integrate as decision points in a DevOps pipeline aka DevSecOps.
  • DevSecOps tool(s) should have a policy engine that can respond with a pass/fail decision for the pipeline. 
    • This optimizes response time.
    • Supports separation of duties (SoD) by externalizing security decisions outside the pipeline.
    • “Fast and frugal” decisioning is preferred over customized scoring to better support velocity and consistency. 
    • Does not exclude the need for detailed information provided as pipeline output.
  • Full inspection of the supply chain element to be decisioned, aka “slow path,” should be used when an element is unknown to the pipeline decisioner. 
  • Minimal or incremental inspection of the supply chain element to be decisioned, aka “fast path,” should be used when an element is recognized (e.g. hash) by the pipeline decisioner.
  • Decision points should have a “fast path” available, where possible, to minimize any latency introduced from security decisioning.
  • There should be no attempt to use customized risk scores in the pipeline. While temporal and contextual elements are useful in reporting and judging how to mitigate operational risk, attempts to use custom scores in a pipeline could unnecessarily complicate the decisioning process, create inconsistency and decrease performance of the pipeline.  
  • Security policy engines should not be managed by the pipeline team, but externally by a security SME, to comply with SoD and reduce opportunities for subversion of security policy decisions during automation.

Using a master policy engine, such as the Open Policy Agent (OPA), is an ideal way to “shift left” by providing a validation capability-as-a-service that can be integrated at different phases into the development and deployment of applications. Ideally, this allows the decoupling of compliance from control, reducing bottlenecks and inconsistency in the process from faulty security criteria integrated into pipeline code. By using security policy-as-code that is created and managed by security teams, DevSecOps will align more closely with the rest of the SDLC. Because at the end of the day, the supply chain is only as good as the product it delivers.

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