12 KiB
Autocert
Autocert issues X.509 certificates from your own internal certificate authority and auto-mounts them in kubernetes containers so services can use TLS.
Autocert is a kubernetes add-on that integrates with step certificates to automatically issue X.509 certificates and mount them in your containers. It also automatically renews certificates before they expire.
Key Features
- A complete public key infrastructure that you control for your kubernetes clusters
- Certificate authority that's easy to initialize and install
- Automatic injection of certificates and keys in annotated containers
- Enable on a per-namespace basis
- Namespaced installation to restrict access to privileged CA and provisioner containers
- Ability to run subordinate to an existing public key infrastructure
- Supports federatation with other roots
Example
Autocert is incredibly easy to use. To trigger automatic certificate management you simply add an annotation to your pods specifying your service's DNS hostname. Autocert will do the rest: securely issuing a certificate, mounting it in containers, and handling renewals.
$ cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata: {name: sleep}
spec:
replicas: 1
selector: {matchLabels: {app: sleep}}
template:
metadata:
annotations:
autocert.step.sm/name: sleep.default.svc.cluster.local
labels: {app: sleep}
spec:
containers:
- name: sleep
image: alpine
command: ["/bin/sleep", "86400"]
imagePullPolicy: IfNotPresent
EOF
$ kubectl exec -it sleep-f996bd578-nch7c -c sleep -- ls -lias /var/run/autocert.step.sm
total 20
1593393 4 drwxrwxrwx 2 root root 4096 Jan 17 21:27 .
1339651 4 drwxr-xr-x 1 root root 4096 Jan 17 21:27 ..
1593451 4 -rw------- 1 root root 574 Jan 17 21:27 root.crt
1593442 4 -rw-r--r-- 1 root root 1352 Jan 17 21:41 site.crt
1593443 4 -rw-r--r-- 1 root root 227 Jan 17 21:27 site.key
What are autocert certificates good for?
Autocert certificates let you secure your data plane (service-to-service) communication using mutual TLS (mTLS). Services and proxies can limit access to clients that also have a certificate issued by your certificate authority (CA). Servers can identify which client is connecting improving visibility and enabling granular access control.
Once certificates are issued you can use mTLS to secure communication in to, out of, and between kubernetes clusters. Services can use mTLS to only allow connections from clients that have their own certificate issued from your CA.
It's like your own Let's Encrypt, but you control who gets a certificate.
Getting Started
These instructions will get autocert installed quickly on an existing kubernetes cluster.
Prerequisites
Make sure you've installed step version 0.8.3 or later:
$ step version
Smallstep CLI/0.8.3 (darwin/amd64)
Release Date: 2019-01-16 01:46 UTC
You'll also need kubectl and a kubernetes cluster running version 1.9 or later:
$ kubectl version --short
Client Version: v1.13.1
Server Version: v1.10.11
You'll also need webhook admission controllers enabled in your cluster:
$ kubectl api-versions | grep "admissionregistration.k8s.io/v1beta1"
admissionregistration.k8s.io/v1beta1
We'll be creating a new kubernetes namespace and setting up some RBAC rules during installation. You'll need appropriate permissions in your cluster (e.g., you may need to be cluster-admin).
TODO: Check whether you have cluster permissions..? GKE instructions here if you don't have them.
In order to grant these permissions you may need to give yourself cluster-admin rights in your cluster. GKE, in particular, does not give the cluster owner these rights by default. You can give yourself cluster-admin rights by running:
kubectl create clusterrolebinding cluster-admin-binding \
--clusterrole cluster-admin \
--user $(gcloud config get-value account)
Install
You can install step certificates and autocert in one step by running:
curl https://github.com/smallstep/... | sh
If you don't like piping curl to sh (good for you) you can also install manually then return here to complete the quick start guide.
Enable autocert
To enable autocert for a namespace the autocert.step.sm=enabled label (the autocert webhook will not affect namespaces for which it is not enabled). To enable autocert for the default namespace run:
$ kubectl label namespace default autocert.step.sm=enabled
To check your work you can check which namespaces have autocert enabled by running:
$ kubectl get namespace -L autocert.step.sm
NAME STATUS AGE AUTOCERT.STEP.SM
default Active 59m enabled
...
Annotate pods
In addition to enabling autocert for a namespace, pods must be annotated with their name for certificates to be injected. The annotated name will appear as the common name and SAN in the issued certificate.
To trigger certificate injection pods must be annotated at creation time. You can do this in your deployment YAMLs:
$ cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata: {name: sleep}
spec:
replicas: 1
selector: {matchLabels: {app: sleep}}
template:
metadata:
annotations:
autocert.step.sm/name: sleep.default.svc.cluster.local
labels: {app: sleep}
spec:
containers:
- name: sleep
image: alpine
command: ["/bin/sleep", "86400"]
imagePullPolicy: IfNotPresent
EOF
If successful, kubectl describe pod will show a new annotation and indicate that a new mount has been created (for certificates). An init container and sidecar are also installed to handle certificate issuance and renewal, respectively.
$ kubectl describe pod sleep
Name: sleep-f996bd578-nch7c
Namespace: default
<... snip ...>
Annotations: autocert.step.sm/name: sleep.default.svc.cluster.local
autocert.step.sm/status: injected
Status: Running
<... snip ...>
Init Containers:
autocert-bootstrapper:
Image: step-k8s/bootstrapper
<... snip ...>
Containers:
sleep:
Image: alpine
<... snip ...>
Mounts:
/var/run/autocert.step.sm from certs (ro)
/var/run/secrets/kubernetes.io/serviceaccount from default-token-jn988 (ro)
autocert-renewer:
Image: step-k8s/renewer
<... snip ...>
Volumes:
certs:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
<... snip ...>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 4m2s default-scheduler Successfully assigned sleep-f996bd578-nch7c to docker-for-desktop
Normal SuccessfulMountVolume 4m2s kubelet, docker-for-desktop MountVolume.SetUp succeeded for volume "certs"
Normal SuccessfulMountVolume 4m2s kubelet, docker-for-desktop MountVolume.SetUp succeeded for volume "default-token-jn988"
Normal Pulled 4m1s kubelet, docker-for-desktop Container image "step-k8s/bootstrapper" already present on machine
Normal Created 4m1s kubelet, docker-for-desktop Created container
Normal Started 4m kubelet, docker-for-desktop Started container
Normal Pulled 4m kubelet, docker-for-desktop Container image "alpine" already present on machine
Normal Created 4m kubelet, docker-for-desktop Created container
Normal Started 3m59s kubelet, docker-for-desktop Started container
Normal Pulled 3m59s kubelet, docker-for-desktop Container image "step-k8s/renewer" already present on machine
Normal Created 3m59s kubelet, docker-for-desktop Created container
Normal Started 3m59s kubelet, docker-for-desktop Started container
Certificates are mounted to /var/run/autocert.step.sm. We can inspect this directory to make sure everything worked correctly:
$ kubectl exec -it sleep-f996bd578-nch7c -c sleep -- ls -lias /var/run/autocert.step.sm
total 20
1593393 4 drwxrwxrwx 2 root root 4096 Jan 17 21:27 .
1339651 4 drwxr-xr-x 1 root root 4096 Jan 17 21:27 ..
1593451 4 -rw------- 1 root root 574 Jan 17 21:27 root.crt
1593442 4 -rw-r--r-- 1 root root 1352 Jan 17 21:41 site.crt
1593443 4 -rw-r--r-- 1 root root 227 Jan 17 21:27 site.key
The autocert-renewer sidecare installs the step CLI tool, which we can use to inspect the issued certificate:
$ kubectl exec -it sleep-f996bd578-nch7c -c autocert-renewer -- step certificate inspect /var/run/autocert.step.sm/site.crt
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 46935033335539540860078000614852612373 (0x234f5bce23705f015a8377ab1cfd5115)
Signature Algorithm: ECDSA-SHA256
Issuer: CN=Autocert Intermediate CA
Validity
Not Before: Jan 17 21:41:04 2019 UTC
Not After : Jan 17 21:46:14 2019 UTC
Subject: CN=sleep.default.svc.cluster.local
Subject Public Key Info:
Public Key Algorithm: ECDSA
Public-Key: (256 bit)
X:
31:aa:a1:7f:c8:b4:c6:da:90:fc:b8:3a:e9:cc:48:
f9:89:b9:5d:d7:a4:63:80:76:9f:21:6d:e5:88:4c:
a8:e4
Y:
ed:21:38:57:cd:3f:32:71:6f:ca:81:34:b0:4a:bd:
a3:c4:8d:d1:87:bc:2c:4c:42:79:e5:35:49:38:3f:
b7:c8
Curve: P-256
X509v3 extensions:
X509v3 Key Usage: critical
Digital Signature, Key Encipherment
X509v3 Extended Key Usage:
TLS Web Server Authentication, TLS Web Client Authentication
X509v3 Subject Key Identifier:
43:0E:0A:50:30:A5:5B:AF:22:AC:28:49:26:53:2A:B4:D4:20:E0:E0
X509v3 Authority Key Identifier:
keyid:61:45:1E:E4:95:4C:0A:6B:37:4C:43:41:FD:54:2E:8E:5E:A2:24:EF
X509v3 Subject Alternative Name:
DNS:sleep.default.svc.cluster.local
Signature Algorithm: ECDSA-SHA256
30:44:02:20:0c:c5:ab:0d:22:17:a2:04:9f:ff:5f:b1:c0:a5:
8b:94:88:e0:40:66:e1:19:e9:34:2f:67:74:12:4f:bb:51:8b:
02:20:01:7e:0d:44:ce:b2:92:41:d5:78:0d:02:5a:68:05:7c:
c2:a9:81:28:71:5c:95:6d:56:51:49:e0:37:b7:09:87
Test your installation
To test your installation you can install the hello-mtls demo app.
- Install app, which uses mTLS and responds "hello,
identity" - Do a
kubectl runofstep-clithen get a certificate usingstepandcurl hello-mtlsfrom within the cluster - Port forward from localhost to get a certificate then
curlwith--resolve
Further reading
- Link to ExternalDNS example
- Link to multiple cluster with Service type ExternalDNS so they can communicate
Uninstall
- Delete the
sleepdeployment (if you created it) - Remove labels (show how to find labelled namespaces)
- Remove annotations (show how to find any annotated pods)
- Remove secrets (show how to find labelled secrets)
- Delete
stepnamespace