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Using custom root certificates with Minikube

If you were to draw a coordinate system for software, where the x-axis was “important to use” and the y-axis was “enjoyable to use”, x509 certificates would be at the extreme edge of the bottom right of quadrant four. Much as I dislike them, they are absolutely critical to securing practically everything we do. As is the case with most companies, Scribd uses custom root certificates to establish a controlled chain of trust for internal resources. A sensible practice, but can be a great learning exercise, causing you to discover all the various ways in which trust is defined and managed in a modern development environment.

This week I’m doing a wee bit of Kubernetes work, which has required the use of Minikube for local testing before I push specs and containers into merge requests. As luck would have it, everything I’m touching also requires accessing internal tools and services, secured by our internal chain of trust. While my laptop already has our certificate added to its trust store, the virtual machine which Minikube provisions to run the local Kubernetes cluster does not. As such, it also needs to be taught about the custom root certificate before I can pull from our internal registry.

Fortunately, adding a custom root certificate has gotten much easier in recent years with Minikube. Following this comment from GitHub, it’s as easy as two commands:

mkdir -p ~/.minikube/files/etc/ssl/certs &&
    cp ~/my-special-corporate.crt

With the PEM-formatted certificate in place, minikube start will copy the file into the appropriate destination once the virtual machine boots, and the Docker daemon will then be able to verify the certificate for my-private-registry.corp.

From there it’s very smooth sailing to pull containers from the private registry via Kubernetes pod definitions.

Trust anchors away!