KSOPS - A Flexible Kustomize Plugin for SOPS Encrypted Resource

• Background
• Overview
• Requirements
• Installation Options
• Getting Started
• Generator Options
• Development and Testing
• Argo CD Integration 🤖

Background

At Viaduct, we manage our Kubernetes resources via the GitOps pattern; however, we could not find a solution compatible with our stack for managing secrets via the GitOps paradigm. We built KSOPS to connect kustomize to SOPS and integrated it with Argo CD to safely manage our secrets the same way we manage the rest our Kubernetes manifest.

Overview

KSOPS, or kustomize-SOPS, is a kustomize exec plugin for SOPS encrypted resources. KSOPS can be used to decrypt any Kubernetes resource, but is most commonly used to decrypt encrypted Kubernetes Secrets and ConfigMaps. As a kustomize plugin, KSOPS allows you to manage, build, and apply encrypted manifests the same way you manage the rest of your Kubernetes manifests.

Requirements

• kustomize
• XDG_CONFIG_HOME environment variable is set in your shell. If it's not set, run the following

# Don't forget to define XDG_CONFIG_HOME in your .bashrc or .zshrc
echo "export XDG_CONFIG_HOME=\$HOME/.config" >> $HOME/.zshrc
source $HOME/.zshrc

Installation

Install the Latest Release

Using curl

# Verify the $XDG_CONFIG_HOME environment variable exists then run
curl -s https://raw.githubusercontent.com/viaduct-ai/kustomize-sops/master/scripts/install-ksops-archive.sh | bash

Or using wget

# Verify the $XDG_CONFIG_HOME environment variable exists then run
wget -qcO - https://raw.githubusercontent.com/viaduct-ai/kustomize-sops/master/scripts/install-ksops-archive.sh | bash

Install from Source

# Optionally, install kustomize via
# make kustomize
# Verify the $XDG_CONFIG_HOME environment variable exists then run
make install

Getting Started (Tutorial)

0. Verify Requirements

Before continuing, verify your installation of kustomize and gpg. Below are a few non-comprehensive commands to quickly check your installations:

# Verify kustomize is installed
kustomize version

# Verify gpg is installed
gpg --help

# Verify XDG_CONFIG_HOME environment variable is set
echo $XDG_CONFIG_HOME

1. Download and install KSOPS

# Verify the $XDG_CONFIG_HOME environment variable exists then run
source <(curl -s https://raw.githubusercontent.com/viaduct-ai/kustomize-sops/master/scripts/install-ksops-archive.sh)

2. Import Test PGP Keys

To simplify local development and testing, we use PGP test keys. To import the keys, run the following command from the repository's root directory:

make import-test-keys

If you are following this tutorial, be sure to run this before the following steps. The PGP keys will also be imported when you run make test

See SOPS for details.

3. Configure SOPS via .sops.yaml

For this example and testing, KSOPS relies on the SOPS creation rules defined in .sops.yaml. To make encrypted secrets more readable, we suggest using the following encryption regex to only encrypt data and stringData values. This leaves non-sensitive fields, like the secret's name, unencrypted and human readable.

Note: You only have to modify .sops.yaml if you want to use your key management service in this example instead of the default PGP key imported in the previous step.

creation_rules:
  - encrypted_regex: "^(data|stringData)$"
    # Specify kms/pgp/etc encryption key
    # This tutorial uses a local PGP key for encryption.
    # DO NOT USE IN PRODUCTION ENV
    pgp: "FBC7B9E2A4F9289AC0C1D4843D16CEE4A27381B4"
    # Optionally you can configure to use a providers key store
    # kms: XXXXXX
    # gcp_kms: XXXXXX

4. Create a Resource

# Create a local Kubernetes Secret
cat <<EOF > secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: mysecret
type: Opaque
data:
  username: YWRtaW4=
  password: MWYyZDFlMmU2N2Rm
EOF

5. Encrypt the Resources

# Encrypt with SOPS CLI
# Specify SOPS configuration in .sops.yaml
sops -e secret.yaml > secret.enc.yaml

6. Define KSOPS kustomize Generator

# Create a local Kubernetes Secret
cat <<EOF > secret-generator.yaml
apiVersion: viaduct.ai/v1
kind: ksops
metadata:
  # Specify a name
  name: example-secret-generator
files:
  - ./secret.enc.yaml
EOF

7. Create the kustomization.yaml

Read about kustomize plugins

cat <<EOF > kustomization.yaml
generators:
  - ./secret-generator.yaml
EOF

8. Build with kustomize 🔑

# Build with kustomize to verify
# In kustomize v2 and v3 the command is
# kustomize build --enable_alpha_plugins .
kustomize build --enable-alpha-plugins .

Troubleshooting

Sanity Checks

• Validate ksops is in the kustomize plugin path
  • $XDG_CONFIG_HOME/kustomize/plugin/viaduct.ai/v1/ksops/ksops

Check Existing Issues

Someone might have already encountered your issue.

https://github.com/viaduct-ai/kustomize-sops/issues

Generator Options

KSOPS supports kustomize exec plugins annotation based generator options. At the time of writing, the supported annotations are:

• kustomize.config.k8s.io/needs-hash
• kustomize.config.k8s.io/behavior

For information, read the kustomize generator options documentation.

Encrypted Secret Overlays w/ Generator Options

Sometimes there is a default secret as part of a project's base manifests, like the base Argo CD secret, which you want to replace in your overlay. Other times, you have parts of base secret that are common across different overlays but you want to partially update, or merge, changes specific to each overlay as well. You can achieve both of these goals by simply adding the following annotations to your encrypted secrets:

Replace a Base Secret

apiVersion: v1
kind: Secret
metadata:
  name: argocd-secret
  annotations:
    # replace the base secret data/stringData values with these encrypted data/stringData values
    kustomize.config.k8s.io/behavior: replace
type: Opaque
data:
  # Encrypted data here
stringData:
  # Encrypted data here

Merge/Patch a Base Secret

apiVersion: v1
kind: Secret
metadata:
  name: argocd-secret
  annotations:
    # merge the base secret data/stringData values with these encrypted data/stringData values
    kustomize.config.k8s.io/behavior: merge
type: Opaque
data:
  # Encrypted data here
stringData:
  # Encrypted data here

Development and Testing

Before developing or testing KSOPS, ensure all external requirements are properly installed.

# Setup development environment
make setup

Development

KSOPS implements the kustomize plugin API in ksops.go.

KSOPS's logic is intentionally simple. Given a list of SOPS encrypted Kubernetes manifests, it iterates over each file and decrypts it via SOPS decrypt library. KSOPS assumes nothing about the structure of the encrypted resource and relies on kustomize for manifest validation. KSOPS expects the encryption key to be accessible. This is important to consider when using KSOPS for CI/CD.

Testing

Testing KSOPS requires:

Everything is handled for you by make test. Just run it from the repo's root directory:

make test

Migration from KSOPS v2.x.x to v3.x.x

Required Changes

• The opt-in ksops-exec kind is deprecated. If you are using the ksops-exec kind, please migrate to ksops once you've upgrade to v3.x.x.

Background

In KSOPS v3.x.x, the kustomize plugin ksops was migrated to an exec plugin from a Go plugin because of simpler installation, dependency management, and package maintenance.

KSOPS was originally developed as a kustomize Go plugin. Up until v2.2.0 this was the only installation option, but in v2.2.0, KSOPS introduced an opt-in exec plugin under via the ksops-exec kind. Now that KSOPS is only an exec plugin, the ksops-exec kind is deprecated.

Argo CD Integration 🤖

KSOPS becomes even more powerful when integrated with a CI/CD pipeline. By combining KSOPS with Argo CD, you can manage Kubernetes secrets via the same Git Ops pattern you use to manage the rest of your kubernetes manifests. To integrate KSOPS and Argo CD, you will need to update the Argo CD ConifgMap and create a strategic merge patch or a custom Argo CD build. As an alternative you can also use the Argo CD Helm Chart with custom values. Don't forget to inject any necessary credentials (i.e AWS credentials) when deploying the Argo CD + KSOPS build!

KSOPS Docker Image

KSOPS Quay.io Image

Enable Kustomize Plugins via Argo CD ConfigMap

As of now to allow Argo CD to use kustomize plugins you must use the enable-alpha-plugins flag. This is configured by the kustomize.buildOptions setting in the Argo CD ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  labels:
    app.kubernetes.io/name: argocd-cm
    app.kubernetes.io/part-of: argocd
data:
  # For KSOPs versions < v2.5.0, use the old kustomize flag style
  # kustomize.buildOptions: "--enable_alpha_plugins"
  kustomize.buildOptions: "--enable-alpha-plugins"

KSOPS Repo Sever Patch

The simplest way to integrate KSOPS with Argo CD is with a strategic merge patch on the Argo CD repo server deployment. The patch below uses an init container to build KSOPS and volume mount to inject the KSOPS plugin and, optionally, override the kustomize executable.

# argo-cd-repo-server-ksops-patch.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: argocd-repo-server
spec:
  template:
    spec:
      # 1. Define an emptyDir volume which will hold the custom binaries
      volumes:
        - name: custom-tools
          emptyDir: {}
      # 2. Use an init container to download/copy custom binaries into the emptyDir
      initContainers:
        - name: install-ksops
          image: viaductoss/ksops:v3.0.2
          command: ["/bin/sh", "-c"]
          args:
            - echo "Installing KSOPS...";
              mv ksops /custom-tools/;
              mv $GOPATH/bin/kustomize /custom-tools/;
              echo "Done.";
          volumeMounts:
            - mountPath: /custom-tools
              name: custom-tools
      # 3. Volume mount the custom binary to the bin directory (overriding the existing version)
      containers:
        - name: argocd-repo-server
          volumeMounts:
            - mountPath: /usr/local/bin/kustomize
              name: custom-tools
              subPath: kustomize
              # Verify this matches a XDG_CONFIG_HOME=/.config env variable
            - mountPath: /.config/kustomize/plugin/viaduct.ai/v1/ksops/ksops
              name: custom-tools
              subPath: ksops
          # 4. Set the XDG_CONFIG_HOME env variable to allow kustomize to detect the plugin
          env:
            - name: XDG_CONFIG_HOME
              value: /.config
        ## If you use AWS or GCP KMS, don't forget to include the necessary credentials to decrypt the secrets!
        #  - name: AWS_ACCESS_KEY_ID
        #    valueFrom:
        #      secretKeyRef:
        #        name: argocd-aws-credentials
        #        key: accesskey
        #  - name: AWS_SECRET_ACCESS_KEY
        #    valueFrom:
        #      secretKeyRef:
        #        name: argocd-aws-credentials
        #        key: secretkey

Custom Argo CD w/ KSOPS Dockerfile

Alternatively, for more control and faster pod start times you can build a custom docker image.

ARG ARGO_CD_VERSION="v1.7.7"
# https://github.com/argoproj/argo-cd/blob/master/Dockerfile
ARG KSOPS_VERSION="v3.0.2"

#--------------------------------------------#
#--------Build KSOPS and Kustomize-----------#
#--------------------------------------------#

FROM viaductoss/ksops:$KSOPS_VERSION as ksops-builder

#--------------------------------------------#
#--------Build Custom Argo Image-------------#
#--------------------------------------------#

FROM argoproj/argocd:$ARGO_CD_VERSION

# Switch to root for the ability to perform install
USER root

# Set the kustomize home directory
ENV XDG_CONFIG_HOME=$HOME/.config
ENV KUSTOMIZE_PLUGIN_PATH=$XDG_CONFIG_HOME/kustomize/plugin/

ARG PKG_NAME=ksops

# Override the default kustomize executable with the Go built version
COPY --from=ksops-builder /go/bin/kustomize /usr/local/bin/kustomize

# Copy the plugin to kustomize plugin path
COPY --from=ksops-builder /go/src/github.com/viaduct-ai/kustomize-sops/*  $KUSTOMIZE_PLUGIN_PATH/viaduct.ai/v1/${PKG_NAME}/

# Switch back to non-root user
USER argocd

Argo CD Helm Chart with Custom Tooling

We can setup KSOPS custom tooling in the Argo CD Chart with the following values:

# Enable Kustomize Alpha Plugins via Argo CD ConfigMap, required for ksops
server:
  config:
    kustomize.buildOptions: "--enable-alpha-plugins"

repoServer:
  # Set the XDG_CONFIG_HOME env variable to allow kustomize to detect the plugin
  env:
    - name: XDG_CONFIG_HOME
      value: /.config

  # Use init containers to configure custom tooling
  # https://argoproj.github.io/argo-cd/operator-manual/custom_tools/
  volumes:
    - name: custom-tools
      emptyDir: {}

  initContainers:
    - name: install-ksops
      image: viaductoss/ksops:v3.0.2
      command: ["/bin/sh", "-c"]
      args:
        - echo "Installing KSOPS...";
          mv ksops /custom-tools/;
          mv $GOPATH/bin/kustomize /custom-tools/;
          echo "Done.";
      volumeMounts:
        - mountPath: /custom-tools
          name: custom-tools
  volumeMounts:
    - mountPath: /usr/local/bin/kustomize
      name: custom-tools
      subPath: kustomize
      # Verify this matches a XDG_CONFIG_HOME=/.config env variable
    - mountPath: /.config/kustomize/plugin/viaduct.ai/v1/ksops/ksops
      name: custom-tools
      subPath: ksops