gangway

(noun): An opening in the bulwark of the ship to allow passengers to board or leave the ship.

An application that can be used to easily enable authentication flows via OIDC for a kubernetes cluster. Kubernetes supports OpenID Connect Tokens as a way to identify users who access the cluster. Gangway allows users to self-configure their kubectl configuration in a few short steps.

Deployment

Instructions for deploying gangway for common cloud providers can be found here.

How It Works

Kubernetes supports OpenID Connect (OIDC) as a user authentication mechanism. OIDC is an authentication protocol that allows servers to verify the identity of a user by way of an ID Token.

When using OIDC to authenticate with Kubernetes, the client (e.g. kubectl) sends the ID token alongside all requests to the API server. On the server side, the Kubernetes API server verifies the token to ensure it is valid and has not expired. Once verified, the API server extracts username and group membership information from the token, and continues processing the request.

In order to obtain the ID token, the user must go through the OIDC authentication process. This is where Gangway comes in. Gangway is a web application that enables the OIDC authentication flow which results in the minting of the ID Token.

Gangway is configured as a client of an upstream Identity Service that speaks OIDC. To obtain the ID token, the user accesses Gangway, initiates the OIDC flow by clicking the "Log In" button, and completes the flow by authenticating with the upstream Identity Service. The user's credentials are never shared with Gangway.

Once the authentication flow is complete, the user is redirected to a Gangway page that provides instructions on how to configure kubectl to use the ID token.

The following sequence diagram details the authentication flow:

API-Server flags

gangway requires that the Kubernetes API server is configured for OIDC:

https://kubernetes.io/docs/admin/authentication/#configuring-the-api-server

kube-apiserver
...
--oidc-issuer-url="https://example.auth0.com/"
--oidc-client-id=3YM4ue8MoXgBkvCIHh00000000000
--oidc-username-claim=email
--oidc-groups-claim=groups

Build

Requirements for building

• Go (built with 1.10)
• esc for static resources.
• dep for dependency management.

A Makefile is provided for building tasks. The options are as follows

Getting started is as simple as:

go get -u github.com/heptiolabs/gangway
cd $GOPATH/src/github.com/heptiolabs/gangway
make setup
make