Vault Plugin: Kubernetes Auth Backend

This is a standalone backend plugin for use with Hashicorp Vault. This plugin allows for Kubernetes Service Accounts to authenticate with Vault.

Please note: We take Vault's security and our users' trust very seriously. If you believe you have found a security issue in Vault, please responsibly disclose by contacting us at [email protected].

Quick Links

• Vault Website: [https://www.vaultproject.io]
• Kubernetes Auth Docs: [https://www.vaultproject.io/docs/auth/kubernetes.html]
• Main Project Github: [https://www.github.com/hashicorp/vault]

Getting Started

This is a Vault plugin and is meant to work with Vault. This guide assumes you have already installed Vault and have a basic understanding of how Vault works.

Otherwise, first read this guide on how to get started with Vault.

To learn specifically about how plugins work, see documentation on Vault plugins.

Security Model

The current authentication model requires providing Vault with a Service Account token, which can be used to make authenticated calls to Kubernetes. This token should not typically be shared, but in order for Kubernetes to be treated as a trusted third party, Vault must validate something that Kubernetes has cryptographically signed and that conveys the identity of the token holder.

We expect Kubernetes to support less sensitive mechanisms in the future, and the Vault integration will be updated to use those mechanisms when available.

Usage

Please see documentation for the plugin on the Vault website.

This plugin is currently built into Vault and by default is accessed at auth/kubernetes. To enable this in a running Vault server:

$ vault auth enable kubernetes
Successfully enabled 'kubernetes' at 'kubernetes'!

To see all the supported paths, see the Kubernetes auth API docs.

Developing

If you wish to work on this plugin, you'll first need Go installed on your machine.

To compile a development version of this plugin, run make or make dev. This will put the plugin binary in the bin and $GOPATH/bin folders. dev mode will only generate the binary for your platform and is faster:

$ make
$ make dev

Put the plugin binary into a location of your choice. This directory will be specified as the plugin_directory in the Vault config used to start the server.

...
plugin_directory = "path/to/plugin/directory"
...

Start a Vault server with this config file:

$ vault server -config=path/to/config.hcl ...
...

Once the server is started, register the plugin in the Vault server's plugin catalog:

$ vault plugin register \
        -sha256=<expected SHA256 Hex value of the plugin binary> \
        -command="vault-plugin-auth-kubernetes" \
        auth kubernetes
...
Success! Data written to: sys/plugins/catalog/kubernetes

Note you should generate a new sha256 checksum if you have made changes to the plugin. Example using openssl:

openssl dgst -sha256 $GOPATH/vault-plugin-auth-kubernetes
...
SHA256(.../go/bin/vault-plugin-auth-kubernetes)= 896c13c0f5305daed381952a128322e02bc28a57d0c862a78cbc2ea66e8c6fa1

Enable the auth plugin backend using the Kubernetes auth plugin:

$ vault auth enable kubernetes
...

Successfully enabled 'plugin' at 'kubernetes'!

Tests

If you are developing this plugin and want to verify it is still functioning (and you haven't broken anything else), we recommend running the tests.

To run the tests, invoke make test:

$ make test

You can also specify a TESTARGS variable to filter tests like so:

$ make test TESTARGS='--run=TestConfig'

To run integration tests, you'll need kind installed.

# Create the Kubernetes cluster for testing in
make setup-kind
# Build the plugin and register it with a Vault instance running in the cluster
make setup-integration-test
# Run the integration tests against Vault inside the cluster
make integration-test