The CA fingerprint is not a secret. It is a public value that anyone can
read straight off the certificate, so pinning it in a Gitea secret was the
wrong shape:
- A change to it would be invisible - no commit, no review.
- Nobody with secret-write access could silently repoint the CI runner at a
different CA.
It now lives in `scripts/cluster-ca.sha256`, so changing it is a reviewable
commit. The script reads it from there, and still accepts an override as
its first argument.
This also removes the need for a `KUBE_SERVER_CA_FINGERPRINT` secret, which
the bot token cannot create anyway - the Actions secrets API is owner-only.
The behaviour is unchanged: the CA is fetched over an unverified connection
but only USED if it matches the pinned fingerprint, so an intercepted CA is
refused. Re-tested against the live API server - the matching fingerprint
refreshes the CA and kubectl then works; a wrong one is refused and the
stale CA is left in place.
The review was right on both counts, and both are fixed.
1. MITM. Fetching the CA over an unverified connection (`curl -sk`) and then
trusting it is a privilege-escalation hole: the runner holds cluster-admin
credentials, so an attacker able to intercept the fetch could hand us a CA
of their choosing and then read everything sent over the connection.
The CA is now PINNED. It is still fetched over an insecure connection, but
it is only USED if its SHA-256 fingerprint matches
`KUBE_SERVER_CA_FINGERPRINT`. An intercepted CA will not hash to the
pinned value, so it is refused. If the secret is not set, the job fails
rather than trusting an unverified CA.
2. The hardcoded cluster name. `kubectl config set-cluster default` creates a
NEW cluster entry when the kubeconfig's entry is called something else,
leaving the original (and its stale CA) in use. The name is now read from
the kubeconfig: `{.clusters[0].name}`.
The bash is also moved out of the YAML into `scripts/kube-ca-refresh.sh`, so
it can be read, reviewed and tested on its own rather than as a wall of
shell inside a workflow file.
All three paths are tested against the live API server:
- no fingerprint supplied -> refuses, exit 1
- wrong fingerprint -> refuses, exit 1
- correct fingerprint -> refreshes the CA, exit 0, kubectl then works
hermes