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|
#!/bin/sh
set -e
usage() {
cat <<EOF
Generate certificate suitable for use with an sidecar-injector webhook service.
This script uses k8s' CertificateSigningRequest API to a generate a
certificate signed by k8s CA suitable for use with sidecar-injector webhook
services. This requires permissions to create and approve CSR. See
https://kubernetes.io/docs/tasks/tls/managing-tls-in-a-cluster for
detailed explantion and additional instructions.
The server key/cert k8s CA cert are stored in a k8s secret.
usage: ${0} [OPTIONS]
The following flags are required.
--service Service name of webhook.
--namespace Namespace where webhook service and secret reside.
--secret Secret name for CA certificate and server certificate/key pair.
EOF
exit 1
}
while [ $# -gt 0 ]; do
case ${1} in
--service)
service="$2"
shift
;;
--secret)
secret="$2"
shift
;;
--namespace)
namespace="$2"
shift
;;
*)
usage
;;
esac
shift
done
[ -z ${service} ] && service=danm-webhook-svc
[ -z ${secret} ] && secret=danm-webhook-certs
[ -z ${namespace} ] && namespace=kube-system
if [ ! -x "$(command -v openssl)" ]; then
echo "openssl not found"
exit 1
fi
csrName=${service}.${namespace}
tmpdir=$(mktemp -d)
echo "creating certs in tmpdir ${tmpdir} "
cat <<EOF >> ${tmpdir}/csr.conf
[req]
req_extensions = v3_req
distinguished_name = req_distinguished_name
[req_distinguished_name]
[ v3_req ]
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names
[alt_names]
DNS.1 = ${service}
DNS.2 = ${service}.${namespace}
DNS.3 = ${service}.${namespace}.svc
EOF
openssl genrsa -out ${tmpdir}/server-key.pem 2048
openssl req -new -key ${tmpdir}/server-key.pem -subj "/CN=${service}.${namespace}.svc" -out ${tmpdir}/server.csr -config ${tmpdir}/csr.conf
# clean-up any previously created CSR for our service. Ignore errors if not present.
kubectl delete csr ${csrName} 2>/dev/null || true
# create server cert/key CSR and send to k8s API
cat <<EOF | kubectl create -f -
apiVersion: certificates.k8s.io/v1beta1
kind: CertificateSigningRequest
metadata:
name: ${csrName}
spec:
groups:
- system:authenticated
request: $(cat ${tmpdir}/server.csr | base64 | tr -d '\n')
usages:
- digital signature
- key encipherment
- server auth
EOF
# verify CSR has been created
while true; do
kubectl get csr ${csrName}
if [ "$?" -eq 0 ]; then
break
fi
done
# approve and fetch the signed certificate
kubectl certificate approve ${csrName}
# verify certificate has been signed
for x in $(seq 10); do
serverCert=$(kubectl get csr ${csrName} -o jsonpath='{.status.certificate}')
if [ -n ${serverCert} ]; then
break
fi
sleep 1
done
echo ${serverCert} | openssl base64 -d -A -out ${tmpdir}/server-cert.pem
# create the secret with CA cert and server cert/key
kubectl create secret generic ${secret} \
--from-file=key.pem=${tmpdir}/server-key.pem \
--from-file=cert.pem=${tmpdir}/server-cert.pem \
--dry-run -o yaml |
kubectl -n ${namespace} apply -f -
|
