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Vault Plugin: Azure Auth Backend

This is a standalone backend plugin for use with Hashicorp Vault. This plugin allows for Azure Managed Service Identities 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

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 token generated using Azure's Managed Service Identity, which can be used to make authenticated calls to Azure. This token should not typically be shared, but in order for Azure to be treated as a trusted third party, Vault must validate something that Azure has cryptographically signed and that conveys the identity of the token holder.

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/azure. To enable this in a running Vault server:

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

To see all the supported paths, see the Azure auth backend docs.

Developing

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

Build Plugin

If you're developing for the first time, run make bootstrap to install the necessary tools. Bootstrap will also update repository name references if that has not been performed ever before.

$ make bootstrap

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 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. It may also be specified via -dev-plugin-dir if running Vault in dev mode.

# config.hcl
plugin_directory = "path/to/plugin/directory"
...

Register Plugin

Start a Vault server with this config file:

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

Or start a Vault server in dev mode:

$ vault server -dev -dev-root-token-id=root -dev-plugin-dir="path/to/plugin/directory"

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

$ SHA256=$(openssl dgst -sha256 bin/vault-plugin-auth-azure | cut -d ' ' -f2)
$ vault plugin register \
        -sha256=$SHA256 \
        -command="vault-plugin-auth-azure" \
        auth azure-plugin
...
Success! Data written to: sys/plugins/catalog/azure-plugin

Finally, enable the auth method to use this plugin:

$ vault auth enable azure-plugin
...

Successfully enabled 'plugin' at 'azure-plugin'!

Azure Environment Setup

A Terraform configuration is included in this repository that automates provisioning of Azure resources necessary to configure and authenticate using the auth method. By default, the resources are created in westus2. See variables.tf for the available variables.

Before applying the Terraform configuration, you'll need to:

  1. Authenticate the Terraform provider to Azure
  2. Provide an SSH public key for access to the Azure VM via the TF_VAR_ssh_public_key_path variable (defaults to ~/.ssh/id_rsa.pub)

The Terraform configuration will create:

  • A service principal with necessary role assignments
  • A virtual network, subnet, and security group with only SSH access from your local machine's public IP address
  • A linux virtual machine instance

To provision the Azure resources, run the following:

$ make setup-env

The local_environment_setup.sh file will be created in the bootstrap/terraform directory as a result of running make setup-env. This file contains environment variables needed to configure the auth method. The values can also be accessed via terraform output.

To access the virtual machine via SSH:

ssh adminuser@${VM_IP_ADDRESS}

Once you're finished with plugin development, you can run the following to destroy the Azure resources:

$ make teardown-env

Configure Plugin

A scripted configuration of the plugin is provided in this repository. You can use the script or manually configure the auth method using documentation.

To apply the scripted configuration, first source the environment variables generated by the Azure environment setup:

$ source ./bootstrap/terraform/local_environment_setup.sh

Next, run the make configure target to register, enable, and configure the plugin with your local Vault instance. You can specify the plugin name, plugin directory, and mount path. Default values from the Makefile will be used if arguments aren't provided.

$ PLUGIN_NAME=vault-plugin-auth-azure \
  PLUGIN_DIR=$GOPATH/vault-plugins \
  PLUGIN_PATH=local-auth-azure \
  make configure

Tests

If you are developing this plugin and want to verify it is still functioning, 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'