Problem: "I can manage all my K8s config in git, except Secrets."

Solution: Encrypt your Secret into a SealedSecret, which is safe to store - even to a public repository. The SealedSecret can be decrypted only by the controller running in the target cluster and nobody else (not even the original author) is able to obtain the original Secret from the SealedSecret.

See https://github.com/bitnami/sealed-secrets/releases for the latest release.

$ release=$(curl --silent "https://api.github.com/repos/bitnami/sealed-secrets/releases/latest" | sed -n 's/.*"tag_name": *"\([^"]*\)".*/\1/p')

# Install client-side tool into /usr/local/bin/
$ GOOS=$(go env GOOS)
$ GOARCH=$(go env GOARCH)
$ wget https://github.com/bitnami/sealed-secrets/releases/download/$release/kubeseal-$GOOS-$GOARCH
$ sudo install -m 755 kubeseal-$GOOS-$GOARCH /usr/local/bin/kubeseal

# Install server-side controller into kube-system namespace (by default)
$ kubectl create -f https://github.com/bitnami/sealed-secrets/releases/download/$release/controller.yaml

controller.yaml will create the SealedSecret third-party-resource, install the controller into kube-system namespace, create a service account and necessary RBAC roles.

After a few moments, the controller will start, generate a key pair, and be ready for operation. If it does not, check the controller logs.

The key certificate (public key portion) is used for sealing secrets, and needs to be available wherever kubeseal is going to be used. The certificate is not secret information, although you need to ensure you are using the correct file.

kubeseal will fetch the certificate from the controller at runtime (requires secure access to the Kubernetes API server), but can also be read from a local file for offline situations (eg: automated jobs). The certificate is also printed to the controller log on startup.

If you just want the latest client tool, it can be installed into $GOPATH/bin with:

% go get github.com/bitnami/sealed-secrets/cmd/kubeseal

For a more complete development environment, clone the repository and use the Makefile:

% git clone https://github.com/bitnami/sealed-secrets.git
% cd sealed-secrets

# Build client-side tool and controller binaries
% make

# Create a json/yaml-encoded Secret somehow:
# (note use of `--dry-run` - this is just a local file!)
$ kubectl create secret generic mysecret --dry-run --from-literal=foo=bar -o json >mysecret.json

# This is the important bit:
$ kubeseal <mysecret.json >mysealedsecret.json

# mysealedsecret.json is safe to upload to github, post to twitter,
# etc.  Eventually:
$ kubectl create -f mysealedsecret.json

# Profit!
$ kubectl get secret mysecret

Note the SealedSecret and Secret must have the same namespace and name. This is a feature to prevent other users on the same cluster from re-using your sealed secrets. kubeseal reads the namespace from the input secret, accepts an explicit --namespace arg, and uses the kubectl default namespace (in that order). Any labels, annotations, etc on the original Secret are preserved, but not automatically reflected in the SealedSecret.

By design, this scheme does not authenticate the user. In other words, anyone can create a SealedSecret containing any Secret they like (provided the namespace/name matches). It is up to your existing config management workflow, cluster RBAC rules, etc to ensure that only the intended SealedSecret is uploaded to the cluster. The only change from existing Kubernetes is that the contents of the Secret are now hidden while outside the cluster.

This controller adds a new SealedSecret third-party resource. The interesting part of which is a base64-encoded asymmetrically encrypted Secret.

The controller looks for a cluster-wide private/public key pair on startup, and generates a new key pair if not found. The key is persisted in a regular Secret in the same namespace as the controller. The public key portion of this (in the form of a self-signed certificate) should be made publicly available to anyone wanting to use SealedSecrets with this cluster. The certificate is printed to the controller log at startup, and available via an HTTP GET to /v1/cert.pem on the controller.

During encryption, the original Secret is JSON-encoded and symmetrically encrypted using AES-GCM with a randomly-generated single-use session key. The session key is then asymmetrically encrypted with the controller's public key using RSA-OAEP, and the original Secret's namespace/name as the OAEP input parameter (aka label). The final output is: 2 byte encrypted session key length || encrypted session key || encrypted Secret.

Note that during decryption by the controller, the SealedSecret's namespace/name is used as the OAEP input parameter, ensuring that the SealedSecret and Secret are tied to the same namespace and name.

The generated Secret is marked as "owned" by the SealedSecret and will be garbage collected if the SealedSecret is deleted.

• Will you still be able to decrypt if you no longer have access to your cluster?

No, the private key is only stored in the Secret managed by the controller (unless you have some other backup of your k8s objects). There are no backdoors - without that private key, then you can't decrypt the SealedSecrets. If you can't get to the Secret with the encryption key, and you also can't get to the decrypted versions of your Secrets live in the cluster, then you will need to regenerate new passwords for everything, seal them again with a new sealing key, etc.

• How can I do a backup of my SealedSecrets?

If you do want to make a backup of the encryption private key, it's easy to do from an account with suitable access and:

kubectl get secret -n kube-system sealed-secrets-key -o yaml >master.key

NOTE: This is the controller's public + private key and should be kept omg-safe!

To restore from a backup after some disaster, just put that secret back before starting the controller - or if the controller was already started, replace the newly-created secret and restart the controller:

kubectl replace secret -n kube-system sealed-secrets-key master.key kubectl delete pod -n kube-system -l name=sealed-secrets-controller