brigade-dockerhub-gateway

Brigade Docker Hub Gateway

This is a work-in-progress Brigade 2 compatible gateway that receives events (webhooks) from Docker Hub and propagates them into Brigade 2's event bus.

Installation

Prerequisites:

• A Kubernetes cluster:

  • For which you have the admin cluster role
  • That is already running Brigade 2
  • Capable of provisioning a public IP address for a service of type LoadBalancer. (This means you won't have much luck running the gateway locally in the likes of kind or minikube unless you're able and willing to mess with port forwarding settings on your router, which we won't be covering here.)

• kubectl, helm (commands below require Helm 3.7.0+), and brig (the Brigade 2 CLI)

1. Create a Service Account for the Gateway

Note: To proceed beyond this point, you'll need to be logged into Brigade 2 as the "root" user (not recommended) or (preferably) as a user with the ADMIN role. Further discussion of this is beyond the scope of this documentation. Please refer to Brigade's own documentation.

Using Brigade 2's brig CLI, create a service account for the gateway to use:

$ brig service-account create \
    --id brigade-dockerhub-gateway \
    --description brigade-dockerhub-gateway

Make note of the token returned. This value will be used in another step. It is your only opportunity to access this value, as Brigade does not save it.

Authorize this service account to create new events:

$ brig role grant EVENT_CREATOR \
    --service-account brigade-dockerhub-gateway \
    --source brigade.sh/dockerhub

Note: The --source brigade.sh/dockerhub option specifies that this service account can be used only to create events having a value of brigade.sh/dockerhub in the event's source field. This is a security measure that prevents the gateway from using this token for impersonating other gateways.

2. Install the Docker Hub Gateway

For now, we're using the GitHub Container Registry (which is an OCI registry) to host our Helm chart. Helm 3.7 has experimental support for OCI registries. In the event that the Helm 3.7 dependency proves troublesome for users, or in the event that this experimental feature goes away, or isn't working like we'd hope, we will revisit this choice before going GA.

First, be sure you are using Helm 3.7.0 or greater and enable experimental OCI support:

$ export HELM_EXPERIMENTAL_OCI=1

As this chart requires custom configuration as described above to function properly, we'll need to create a chart values file with said config.

Use the following command to extract the full set of configuration options into a file you can modify:

$ helm inspect values oci://ghcr.io/brigadecore/brigade-dockerhub-gateway \
    --version v0.4.1 > ~/brigade-dockerhub-gateway-values.yaml

Edit ~/brigade-dockerhub-gateway-values.yaml, making the following changes:

• host: Set this to the host name where you'd like the gateway to be accessible.

• brigade.apiAddress: Address of the Brigade API server, beginning with https://

• brigade.apiToken: Service account token from step 2

• service.type: If you plan to enable ingress (advanced), you can leave this as its default -- ClusterIP. If you do not plan to enable ingress, you probably will want to change this value to LoadBalancer.

• tokens: This field should define tokens that can be used by clients to send events (webhooks) to this gateway. Note that keys are completely ignored by the gateway and only the values (tokens) matter. The keys only serve as recognizable token identifiers for human operators.

Save your changes to ~/brigade-dockerhub-gateway-values.yaml and use the following command to install the gateway using the above customizations:

$ helm install brigade-dockerhub-gateway \
    oci://ghcr.io/brigadecore/brigade-dockerhub-gateway
    --version v0.4.1 \
    --create-namespace \
    --namespace brigade-dockerhub-gateway \
    --values ~/brigade-dockerhub-gateway-values.yaml \
    --wait \
    --timeout 300s

3. (RECOMMENDED) Create a DNS Entry

If you overrode defaults and set service.type to LoadBalancer, use this command to find the gateway's public IP address:

$ kubectl get svc brigade-dockerhub-gateway \
    --namespace brigade-dockerhub-gateway \
    --output jsonpath='{.status.loadBalancer.ingress[0].ip}'

If you overrode defaults and enabled support for an ingress controller, you probably know what you're doing well enough to track down the correct IP without our help. 😉

With this public IP in hand, edit your name servers and add an A record pointing your domain to the public IP.

4. Create Webhooks

In your browser, go to your Docker Hub repository for which you'd like to send webhooks to this gateway. From the tabs across the top of the page, select Webhooks.

• In the Webhook name field, add a meaningful name for the webhook.

• In the Webhook URL field, use a value of the form https://<DNS hostname or publicIP>/events?access_token=<url-encoded token>.

• Click Create

Note: Docker Hub doesn't provide any reasonable mechanism for authenticating to the endpoints to which events (webhooks) are sent. Due to this, the only viable approach to authentication is to include a token (a shared secret) in the webhook URL as depicted above. Users are cautioned that even with TLS in play, this is not entirely secure because web servers, reverse proxies, and other infrastructure are apt to capture entire URLs, including query parameters, in their access logs. If your threat model suggests this is an intolerable degree of risk, then do not use this gateway and, more generally, do not use Docker Hub webhooks.

5. Add a Brigade Project

You can create any number of Brigade projects (or modify an existing one) to listen for events that were sent from a Docker Hub repository to your gateway and, in turn, emitted into Brigade's event bus. You can subscribe to all event types emitted by the gateway, or just specific ones.

In the example project definition below, we subscribe to all events emitted by the gateway, provided they've originated from the fictitious example-org/example-repo repository (see the repo qualifier).

apiVersion: brigade.sh/v2
kind: Project
metadata:
  id: dockerhub-demo
description: A project that demonstrates integration with Docker Hub
spec:
  eventSubscriptions:
  - source: brigade.sh/dockerhub
    types:
    - *
    qualifiers:
      repo: example-org/example-repo
  workerTemplate:
    defaultConfigFiles:
      brigade.js: |-
        const { events } = require("@brigadecore/brigadier");

        events.on("brigade.sh/dockerhub", "push", () => {
          console.log("Someone pushed an image to the example-org/example-repo repository!");
        });

        events.process();

In the alternative example below, we subscribe only to push events:

apiVersion: brigade.sh/v2
kind: Project
metadata:
  id: dockerhub-demo
description: A project that demonstrates integration with Docker Hub
spec:
  eventSubscriptions:
  - source: brigade.sh/dockerhub
    types:
    - push
    qualifiers:
      repo: example-org/example-repo
  workerTemplate:
    defaultConfigFiles:
      brigade.js: |-
        const { events } = require("@brigadecore/brigadier");

        events.on("brigade.sh/dockerhub", "push", () => {
          console.log("Someone pushed an image to the example-org/example-repo repository!");
        });

        events.process();

Assuming this file were named project.yaml, you can create the project like so:

$ brig project create --file project.yaml

Push an image to the Docker Hub repo for which you configured webhooks to send an event (webhook) to your gateway. The gateway, in turn, will emit the event into Brigade's event bus. Brigade should initialize a worker (containerized event handler) for every project that has subscribed to the event, and the worker should execute the brigade.js script that was embedded in the example project definition.

List the events for the dockerhub-demo project to confirm this:

$ brig event list --project dockerhub-demo

Full coverage of brig commands is beyond the scope of this documentation, but at this point, additional brig commands can be applied to monitor the event's status and view logs produced in the course of handling the event.

Events Received and Emitted by this Gateway

Events received by this gateway from Docker Hub are, in turn, emitted into Brigade's event bus.

Docker Hub only supports one type of event (webhook) and that is the push event.

Examples Projects

See examples/ for complete Brigade projects that demonstrate various scenarios.

Contributing

The Brigade project accepts contributions via GitHub pull requests. The Contributing document outlines the process to help get your contribution accepted.

Support & Feedback

We have a slack channel! Kubernetes/#brigade Feel free to join for any support questions or feedback, we are happy to help. To report an issue or to request a feature open an issue here

Code of Conduct

Participation in the Brigade project is governed by the CNCF Code of Conduct.