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Encryption

[[TOC]]

Big Bang follows a GitOps approach to managing the Big Bang Kubernetes cluster configuration. Using GitOps, we must securely store secrets in Git using encryption. The private key, which is stored in key storage, is used by the continuous deployment tool to decrypt and deploy the secrets for use in the cluster.

SOPS

Secrets Operations (SOPS) is used to securely encrypt values in YAML, JSON, ENV, INI and BINARY formats. Secrets, such as pull credentials or certificates, should be encrypted with SOPS prior to committing into a Git repository.

The private key used in SOPS should NEVER be stored in Git along side the encrypted secrets.

SOPS supports the ability to add multiple keys to the same file so multiple key pairs can use the same secret. This is useful for environments which may have different keys, but use the same secrets. For each key used, SOPS writes the public key, used to encrypt, and an encrypted copy of the data to the file. Decryption requires use of one of the private keys used. After editing, the embedded public keys are used to re-encrypt the file for all key pairs.

Create Encryption Keys

To setup Big Bang with SOPS, a key pair must be created. The private key is used for decryption and must be securely stored but accessible to the cluster. The public key is used for encryption. Follow the appropriate instructions below to create your key pair.

Key Management Key Pair Instructions Notes
GNU Privacy Guard (GPG)* gpg --full-generate-key Use key type = RSA and RSA, keysize = 4096, expiration = 0
Amazon Web Services (AWS) Key Management Service (KMS) Link Advanced setup help (e.g. roles, profiles, contexts)
Google Cloud Platform (GCP) Key Management Service (KMS) Link
HashiCorp Vault Link

*GPG is not recommended for production use because the private key can be misplaced or compromised too easily

Configure SOPS

SOPS uses .sops.yaml as a configuration file for which keys to use for newly created files. Once a file is created, the key fingerprints are stored in the file and must be re-keyed to use any changes to .sops.yaml.

  1. Follow the SOPS instructions to configure .sops.yaml based on the encryption method you used. Multiple keys of the same type can be added using the block scalar yaml construct, >-, and separating them by a comma and newline.

    If you are using the Big Bang sample files, make sure to remove the development Big Bang key.

  2. Add the following regex to only encrypt data in the yaml files

    creation_rules:
  - encrypted_regex: "^(data|stringData)$"

  3. Save .sops.yaml in the root of folder of your configuration

  4. If you have existing secrets, use the following to re-key them with the configuration in .sops.yaml

    # You must have the old private key to rekey the file
sops updatekeys <encrypted file>

Deploy Private Key

This must be completed before deploying Big Bang or else deploying Secrets will fail.

GPG

  1. Deploy your SOPS private key to a secret named sops-gpg in the cluster

    gpg --export-secret-keys --armor <new key fingerprint> | kubectl create secret generic sops-gpg -n bigbang --from-file=yourkey.asc=/dev/stdin

AWS KMS

  1. Configure your KMS key(s) in your .sops.yaml by adding the target key's ARN to the kms field within each creation rule.

    creation_rules:
  - encrypted_regex: "^(data|stringData)$"
    path_regex: ./dev/.*
    kms: "<kms_key_arn>"

  2. Ensure your cluster (specifically the flux-system/flux-controller) has access to the specified key.

    1. For AWS deployments, this can be managed via IAM roles as described in the SOPS documentation.

    2. For non-AWS deployments

      1. Create an AWS user with appropriate permissions as described in the SOPS documentation.

      2. Create a secret named sops-aws-creds in the cluster using the access creds from the target user:

        k create secret generic -n flux-system sops-aws-creds --from-literal=access_key_id=<key_id> --from-literal=access_key_secret=<key>

GCP KMS

TBD - This article may help to automate secret consumption in Kubernetes.

Azure KeyVault

TBD - This article may help to automate secret consumption in Kubernetes.

HashiCorp Vault

TBD - This article may help to automate secret consumption in Kubernetes.

Configure Big Bang

Big Bang needs to know how to retrieve the private key so it can deploy the encrypted secrets from Git. Decryption configuration is placed in the top-level manifest (e.g. dev.yaml, prod.yaml) from the Big Bang template.

GPG

By default, the Kustomization resource uses a Secret named sops-gpg for the private key as shown here:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: environment
spec:
  decryption:
    provider: sops
    secretRef:
      name: sops-gpg

AWS KMS

Configure the Kustomization resource to use sops for decryption:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: environment
spec:
  decryption:
    provider: sops

Note, we are not providing the secretRef field, which is specific to GPG

If Big Bang is deployed within AWS, KMS key access can be handled via IAM roles and permissions on the cluster resources themselves. However, if the deployment is in a different environment from the KMS keys, AWS credentials may need to be provided via a secret as follows.

Configure the flux-system kustomize-controller component with AWS credential environment variables using kustomize. Specific instructions for doing this may vary by deployment and environment but an example is covered in the bigbang template repo. Broadly speaking, adding environment variables to the kustomize-controller component can be accomplished by adding a patch to the flux/kustomization.yaml for the target deployment or environment. An example of such a kustomization.yaml is shown below:

bases:
  - ../../base/flux

patchesStrategicMerge:
  - |-
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: kustomize-controller
      namespace: flux-system
    spec:
      template:
        spec:
          containers:
          - name: manager
            env:
            - name: AWS_ACCESS_KEY_ID
              valueFrom:
                secretKeyRef:
                  name: sops-aws-creds
                  key: access_key_id
            - name: AWS_SECRET_ACCESS_KEY
              valueFrom:
                secretKeyRef:
                  name: sops-aws-creds
                  key: access_key_secret

Values should come from the sops-aws-creds secret created in AWS KMS above

TBD - Instructions on how to update for GCP, Vault