kubeadm: check all available CA certs against pinned certs

[rojkov]

What type of PR is this?
/kind bug

What this PR does / why we need it:
Currently kubeadm produces an error upon parsing multiple certificates stored in the cluster-info configmap resulting in kubernetes/kubeadm#1399. Yet it's expected to check all available certificates in a scenario like CA key rotation. So, check all available CA certs against pinned certificate hashes.

Which issue(s) this PR fixes:
Fixes kubernetes/kubeadm#1399

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

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[neolit123]

@rojkov the PR seems good to me.
added a couple of suggested changes.

/approve
/ok-to-test
/priority backlog
/test pull-kubernetes-e2e-kind

[neolit123]

%s -> %q

[neolit123]

please modify this function to:

// parsePEMCerts decodes PEM-formatted certificates into a slice of x509.Certificates
func parsePEMCerts(certData []byte) ([]*x509.Certificate, error) {
	var certificates []*x509.Certificate
	var pemBlock *pem.Block

	for {
		pemBlock, certData = pem.Decode(certData)
		if pemBlock == nil {
			return nil, errors.New("invalid PEM data")
		}

		cert, err := x509.ParseCertificate(pemBlock.Bytes)
		if err != nil {
			return nil, errors.Wrap(err, "unable to parse certificate")
		}
		certificates = append(certificates, cert)

		if len(certData) == 0 {
			break
		}
	}
	return certificates, nil
}

note the a PEM- -> PEM change in the function comment.

[rojkov]

Thanks! Fixed

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: neolit123, rojkov

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• cmd/kubeadm/OWNERS [neolit123]

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[neolit123]

@kubernetes/sig-cluster-lifecycle-pr-reviews
for visibility before merge.

/lgtm
/hold

[bart0sh]

non -> none ?

[rojkov]

Thanks! Corrected.

[bart0sh]

/lgtm

[rojkov]

/test pull-kubernetes-e2e-gce

[yagonobre]

Thanks @rojkov
/lgtm

[bart0sh]

@neolit123 please unhold if you don't mind. Thanks.

[neolit123]

/hold cancel