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March 5, 2019 21:09
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Script to mint k8s user certificates and concatenate them into a single config
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#!/bin/bash | |
set -eu -o pipefail | |
REQUEST_ID=$(uuidgen) | |
BASE64_DECODE_FLAG="-D" | |
BASE64_WRAP_FLAG="" | |
CLUSTER_NAME=$1 | |
mkdir -p build | |
mkdir -p ~/.kube/configs/ | |
pushd build | |
cat > csr <<EOF | |
{ | |
"hosts": [], | |
"CN": "${CLUSTER_NAME}-${USER}", | |
"names": [ | |
{ | |
"O": "system:masters" | |
} | |
], | |
"key": { | |
"algo": "ecdsa", | |
"size": 256 | |
} | |
} | |
EOF | |
cat csr | cfssl genkey - | cfssljson -bare server | |
cat <<EOF | kubectl create -f - | |
apiVersion: certificates.k8s.io/v1beta1 | |
kind: CertificateSigningRequest | |
metadata: | |
name: ${REQUEST_ID} | |
spec: | |
groups: | |
- system:authenticated | |
request: $(cat server.csr | base64 | tr -d '\n') | |
usages: | |
- digital signature | |
- key encipherment | |
- server auth | |
EOF | |
kubectl certificate approve ${REQUEST_ID} | |
kubectl get csr ${REQUEST_ID} -o jsonpath='{.status.certificate}' \ | |
| base64 ${BASE64_DECODE_FLAG} > server.crt | |
CLUSTER_DNS=$(kubectl get pods -n kube-system -l k8s-app=kube-dns -o jsonpath='{.items[0].metadata.name}') | |
if [[ $CLUSTER_DNS == "coredns"* ]]; then | |
kubectl -n kube-system exec ${CLUSTER_DNS} -c coredns -- /bin/cat /var/run/secrets/kubernetes.io/serviceaccount/ca.crt > ca.crt | |
else | |
kubectl -n kube-system exec ${CLUSTER_DNS} -c kubedns -- /bin/cat /var/run/secrets/kubernetes.io/serviceaccount/ca.crt > ca.crt | |
fi | |
# Case we're running coreDNS instead | |
if [ "$?" -eq "0" ]; then | |
kubectl -n kube-system exec $(kubectl get pods -n kube-system -l k8s-app=kube-dns -o jsonpath='{.items[0].metadata.name}') -c coredns -- /bin/cat /var/run/secrets/kubernetes.io/serviceaccount/ca.crt > ca.crt | |
fi | |
# Extract cluster IP from the current context | |
CURRENT_CONTEXT=$(kubectl config current-context) | |
CURRENT_CLUSTER=$(kubectl config view -o jsonpath="{.contexts[?(@.name == \"${CURRENT_CONTEXT}\"})].context.cluster}") | |
CURRENT_CLUSTER_ADDR=$(kubectl config view -o jsonpath="{.clusters[?(@.name == \"${CURRENT_CLUSTER}\"})].cluster.server}") | |
cat > ~/.kube/configs/${CLUSTER_NAME} <<EOF | |
apiVersion: v1 | |
clusters: | |
- cluster: | |
certificate-authority-data: $(cat ca.crt | base64 ${BASE64_WRAP_FLAG}) | |
server: ${CURRENT_CLUSTER_ADDR} | |
name: ${CLUSTER_NAME} | |
contexts: | |
- context: | |
cluster: ${CLUSTER_NAME} | |
user: ${CLUSTER_NAME}-${USER} | |
name: ${CLUSTER_NAME} | |
current-context: ${CLUSTER_NAME} | |
kind: Config | |
preferences: {} | |
users: | |
- name: ${CLUSTER_NAME}-${USER} | |
user: | |
client-certificate-data: $(cat server.crt | base64 ${BASE64_WRAP_FLAG}) | |
client-key-data: $(cat server-key.pem | base64 ${BASE64_WRAP_FLAG}) | |
EOF | |
popd | |
rm -rf build | |
KUBECONFIG=$(realpath ~/.kube/configs/* | paste -sd ":" - ) kubectl config view --merge --flatten > ~/.kube/config |
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Added a little bit of logic to address wether you're runnig coreDNS or kubeDNS