gangplank

README

Gangplank

(noun): A board or ramp used as a removable footway between a ship and a pier.

Gangplank is a web application that allows users to authenticate with an OIDC provider and configure their kubectl configuration file with the OpenID Connect Tokens. Gangplank is based on Gangway, which is no longer maintained.

Deployment

Instructions for deploying gangplank 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 Gangplank comes in. Gangplank is a web application that enables the OIDC authentication flow which results in the minting of the ID Token.

Gangplank is configured as a client of an upstream Identity Service that speaks OIDC. To obtain the ID token, the user accesses Gangplank, 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 Gangplank.

Once the authentication flow is complete, the user is redirected to a Gangplank 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

Gangplank 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 version >= 1.12)
• esc for static resources.

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

Getting started is as simple as:

go get -u github.com/sighup/gangplank
cd $GOPATH/src/github.com/sighup/gangplank
make setup
make