We currently don't have direct support for secrets other than your service account's access tokens. We hope to support more arbitrary secrets in the future.
As you said, you can bake things into a base image (ew) or use your credentials to fetch them from somewhere else (I suggest Cloud Storage).
Re:Introducing Google Cloud Container Builder
by lobster_johnson on Tuesday March 07, 2017 @12:25AM
(#13808450)
The problem with uploading them somewhere is that you introduce an implicit dependency that must be documented and dealt with as part of the whole devops universe — it's just one more thing on top of a heap of other things.
It's much nicer, and more secure (in terms of locking down just one thing and not having to manage multiple to be able to centralize secrets somewhere. Whereas keeping things like this close the project is of course more convenient for developers.
Drone has tried two different systems, neither of which were ideal, and is working on a third one. I believe the third one also involves encrypted secrets committed to the project repo.
I suppose one could bake that stuff into a base image, or store it in a Kubernetes secret that the build service account has access to.