First egress rule in matrix, authentik and monitoring. It allows DNS, the cluster
ranges and the whole internet, and denies only 169.254.0.0/16 - link-local, where
Hetzner serves instance metadata unauthenticated to any pod.
Deliberately narrow. The textbook cut, 0.0.0.0/0 except RFC1918, would have severed
two things here, both over 10.0.0.3 on the private Hetzner network: Alloy writes
metrics and logs there, and the TURN rotation reaches Gitea through a hostAlias to
that address. Private ranges therefore stay open.
The payoff is modest and should be stated as such: measured from a pod, the service
answers with instance-id, hostname, region, MAC and network config, while userdata
and public-keys are empty. No credentials are exposed here, unlike the AWS case this
hardening usually targets. It costs nothing though, and it closes the class.
Two preconditions checked rather than assumed, because both are the usual way this
breaks: kube-system carries kubernetes.io/metadata.name so the DNS rule actually
matches, and the cluster is IPv4-only so 0.0.0.0/0 really does cover everything.
Rollback is deleting the one policy per namespace.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Thore CimbalandClaude Opus 5
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