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GIT clone controller

Mutation webhook handler, injects initContainer with a properly configured git container that does a clone or checkout, taking care about permissions.

Use cases

Mounting static user-data in official images

With this approach you can still use official application images like Wordpress image without having to maintain your own images just to inject a theme, plugins or some other custom files.

Simple administrative jobs without CI system

Simply clone your scripts repository in your pod workspace, execute script and exit.

Git clone inside CI job

git-clone-controller checkout is a CLI command that could be a replacement of git clone and git checkout. Its advantage is that it is designed to be running automatic: When repository does not exist, it gets cloned, when exists, then updated with remote.

Setting up

Use helm to install git-clone-controller. For helm values please take a look at values reference.

helm repo add riotkit-org https://riotkit-org.github.io/helm-of-revolution/
helm install my-git-clone-controller riotkit-org/git-clone-controller

Example usage

Every Pod labelled with riotkit.org/git-clone-controller: "true" will be processed by git-clone-controller.

Pod annotations are the place, where git-clone-controller short specification is kept.

apiVersion: v1
kind: Pod
metadata:
    name: "tagged-pod"
    labels:
        # required: only labelled Pods are processed
        riotkit.org/git-clone-controller: "true"
    annotations:
        # required: commit/tag/branch
        git-clone-controller/revision: main
        # required: http/https url
        git-clone-controller/url: "https://github.com/jenkins-x/go-scm"
        # required: target path, where the repository should be cloned, should be placed on a shared Volume mount point with other containers in same Pod
        git-clone-controller/path: /workspace/source
        # optional: user id (will result in adding `securityContext`), in effect: running `git` as selected user and creating files as selected user
        git-clone-controller/owner: "1000"
        # optional: group id (will result in adding `securityContext`), same behavior as in "git-clone-controller/owner"
        git-clone-controller/group: "1000"
        # optional: `kind: Secret` name from same namespace as Pod is (if not specified, then global defaults from operator will be taken, or no authorization would be used)
        git-clone-controller/secretName: git-secrets
        # optional: entry name in `.data` section of selected `kind: Secret`
        git-clone-controller/secretTokenKey: jenkins-x

        # optional: entry name in `.data` section, describes the GIT username, defaults to __token__ if not specified
        #git-clone-controller/secretUsernameKey: username

        # optional: Disable cleaning up untracked and unstaged files (git clean + git reset)
        # git-clone-controller/cleanWorkspace: "false"
spec:
    restartPolicy: Never
    automountServiceAccountToken: false
    containers:
        - command:
              - /bin/sh
              - "-c"
              - "find /workspace/source; ls -la /workspace/source"
          image: busybox:latest
          name: test
          volumeMounts:
              - mountPath: /workspace/source
                name: workspace
    volumes:
        - name: workspace
          emptyDir: {}
          
    # PERMISSIONS:
    #  If `git-clone-controller/owner` and `git-clone-controller/group` specified, then `fsGroup` should have same value there
    #  so the mounted volume would have proper permissions
    securityContext:
        fsGroup: 1000

Running this example:

kubectl delete -f docs/examples/pod-tagged.yaml; kubectl apply -f docs/examples/pod-tagged.yaml

# observe checkout
kubectl logs -f tagged-pod -c git-checkout

# check the example command that will print list of files and permissions
kubectl logs -f tagged-pod

Behavior

Circumstances Behavior
Pods NOT marked with riotkit.org/git-clone-controller: "true" Do Nothing
Pods MARKED with riotkit.org/git-clone-controller: "true" Process
Missing required annotation Do not schedule that Pod
kind: Secret was specified, but is invalid Do not schedule that Pod
Unknown error while processing labelled Pod Do not schedule that Pod
GIT credentials are invalid Fail inside initContainer and don't let Pod's containers to execute
Revision is invalid Fail inside initContainer and don't let Pod's containers to execute
Volume permissions are invalid Fail inside initContainer and don't let Pod's containers to execute
Unknown error while trying to checkout/clone inside initContainer Fail inside initContainer and don't let Pod's containers to execute
There are unknown files in GIT workspace Perform git reset and git clean (can be disabled with annotation)

Security and reliability

  • Using distroless static image (No operating system, it does not contain even glibc)
  • Static golang binary, without dynamic libraries, no dependency on libc
  • No dependency on git binary, thanks to go-git
  • Namespaced kind: Secret are used close to kind: Pod
  • Admission Webhooks are limited in scope on API level - only labelled Pods are touched
  • Default Pod's securityContext runs as non-root, with high uid/gid, should work on OpenShift
  • API is using internally mutual TLS to talk with Kubernetes

Roadmap

v1

  • Injecting git-clone initContainers into labelled pods
  • Support for Git over HTTPS
  • Specifying user id (owner) of files in workspace
  • CLI command git-clone-controller clone ... and single Dockerfile for both initContainer and operator
  • Helm
  • Add configurable security context - runAs and filesystem permissions

v2

  • Namespaced CRD GitClonePermissions to specify which GIT repositories are allowed, where are the clone keys
  • chown user:group -R as an alternative to securityContext in case, when somebody would have to run initContainer as root
  • Support for Git over SSH

v3

  • Possibly: Reacting on webhooks from Gitea and GitHub to update revision on existing pods - deleting marked pods maybe?

Thanks

Special thanks to simple-kubernetes-webhook fantastic project, without it such quick development of this project would not be possible.