Set secure defaults for containerSecurityContext fields

[tarquin-the-brave]

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Is your feature request related to a problem? Please describe.

Consul components running with insecure kubernetes config.

Feature Description

Include secure defaults for the containerSecurityContext fields in the Helm chart.

Hi. A few weeks back I raised #602 and submitted #620 to allow the securityContext on the containers in the server and client Pods to be configured through the Helm chart.

I said once we (Microsoft Azure for Operators) had tested configuring these and found the most secure values they could take, we'd contribute those back as defaults to the chart.

It turns out our use case only needed to deploy the Consul servers via the Helm chart so we've only tested setting server.containerSecurityContext.

We found these can be set to:

server:
  containerSecurityContext:
    privileged: false
    capabilities:
      drop:
        - ALL
    allowPrivilegeEscalation: false
    readOnlyRootFilesystem: true

without affecting the functioning of the Consul server.

We haven't tested setting this for the client Pod. Looking at the client-daemonset.yaml template my guess would be that the consul container will be OK with the same securityContext as the server above.

For the initContainers client-acl-init & client-tls-init you might have to relax readOnlyRootFileSystem to false. It seems from your Pod spec that these initContainers write files to mounted volumes. I can't recall if readOnlyRootFileSystem prevents that or not, I can't tell from the docs. Something to test.

Use Case(s)

All those who deploy with the Helm chart can get the most secure container secuirtyContext values by default.

Contributions

We could contribute these defaults for the server, but I imagine you'd want to implement the "secure defaults" for the client Pod containers too, which we haven't tested.