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Table of Contents

Securely store Micronaut Application secrets in Azure Key Vault

Learn how to create secrets in Azure Key Vault and easily access them in a Micronaut application.

Authors: Slavko Bodvanski, Sergio del Amo, John Shingler

Micronaut Version: 3.9.2

1. Getting Started

In this guide, we will create a Micronaut application written in Kotlin.

2. What you will need

To complete this guide, you will need the following:

  • Some time on your hands

  • A decent text editor or IDE

  • JDK 1.8 or greater installed with JAVA_HOME configured appropriately

3. Creating the Application

Download the complete solution of the Access a database with Micronaut Data JDBC guide. You will use the sample application as a starting point.

4. Micronaut Azure Key Vault Dependencies

Add the following dependency:

pom.xml
<dependency>
    <groupId>io.micronaut.azure</groupId>
    <artifactId>micronaut-azure-secret-manager</artifactId>
    <scope>compile</scope>
</dependency>

5. Update the Application configuration to use Azure Key Vault secrets

5.1. Add the Azure Key Vault secret placeholders to the Application Configuration

src/main/resources/application.yml
datasources:
  default:
+   username: ${JDBC-USER}
+   password: ${JDBC-PASSWORD}
The Azure Key Vault secrets naming convention does not allow "_" to be used as a word joiner. Therefore, when adding JDBC secret placeholders, you should use "-" instead (e.q. JDBC-USER, JDBC-PASSWORD).

5.2. Enable Distributed Configuration

Create a bootstrap.yml file in the resources directory to enable distributed configuration. Add the following:

src/main/resources/bootstrap.yml
micronaut:
  application:
    name: micronautguide (1)
  config-client:
    enabled: true (2)
1 Set the application name in bootstrap.yml instead of application.yml so that it is available when reading configuration from distributed sources. properties
2 Set microanut.config-client.enabled: true which is used to read and resolve configuration from distributed sources.

5.3. Clean up Application Configuration

If application.yml sets micronaut.application.name, remove it. You moved it to bootstrap.yml.

src/main/resources/application.yml
- micronaut:
-  application:
-    name: micronautguide

5.4. Disable Distributed Configuration for Test

To disable distributed configuration for tests, create a bootstrap-test.yml file:

src/test/resources/bootstrap-test.yml
micronaut:
  config-client:
    enabled: false

5.5. Azure Bootstrap Configuration

Add the following configuration for Azure bootstrap.yml:

src/main/resources/bootstrap.yml
azure:
  credential:
    client-secret:
      client-id: ${AZURE_CLIENT_ID} (1)
      tenant-id: ${AZURE_TENANT_ID} (2)
      secret: ${AZURE_SECRET_VALUE} (3)
  key-vault:
    vault-url: ${AZURE_VAULT_URI} (4)
1 The client ID of the trusted application that you will register in Azure Portal
2 The tenant ID
3 The secret value of the registered application
4 The Azure Key Vault resource URI
More details on how to obtain these values are provided in the Azure Portal section below.

5.6. Clean up the Application Configuration

Remove the redundant application name entry from the application.yml.

src/main/resources/application.yml
- micronaut:
-  application:
-    name: micronautguide

6. Store JDBC secrets in Azure Key Vault using Azure Portal

Create Azure Key Vault service resource.

azure vault create vault resouce


When Key Vault service deployment is ready, go to the resource to create secrets. Before clicking on the Secrets option in the left menu list, copy the Vault URI from the main screen section. You will need to set it as an environment variable to integrate Azure Key Vault into your application.

azure vault obtain vault uri


Create new secrets for JDBC user and password. Click on the Secrets option in the left menu, then click on Generate/Import.

azure vault create secret jdbc user


azure vault create secret jdbc password


Go to App registration to register your application with the Microsoft identity platform. After registering your application, copy the secret Application (client) ID, and Directory (tenant) ID. You will use them later as environment variables to connect to Azure Key Vault.

azure register application


Navigate to your application profile to generate application credentials that you will use to authenticate with the Azure Key Vault service. In the left menu, click on the Certificates & secrets. To generate the application credentials, click on the Client secrets tab and then on the New client secret button. Copy the secret value. You must set it along the Application (client) ID, Directory (tenant) ID, and Vault URI as environment variables.

The client’s secret value cannot be viewed, except immediately after creation. Be sure to save the secret when created before leaving the page
azure register application add client secret


To finish the Key Vault setup process. You will need to assign a proper policy to the Key Vault resource.

  • Go to your Key Vault resource profile.

  • Click on the Access policies option in the left menu.

  • Select Get and List options from the Secret Management Operations list.

  • Finally, create an access policy.

azure vault create policy


Prior to completing the policy creation process, a security principal should be assigned. The policy should refer to your application acting as a security principal.

azure vault create principal


7. Running the Application

With almost everything in place, you can start the application and try it out. First, set environment variables to configure the application datasource, then start the application.

Create environment variables for AZURE_CLIENT_ID, AZURE_TENANT_ID, AZURE_SECRET_VALUE, and AZURE_VAULT_URI, which will be used in the Micronaut app’s application.yml datasource:

export AZURE_CLIENT_ID=<the client id from the Azure configuratipn step>
export AZURE_TENANT_ID=<the tenant id from the Azure configuratipn step>
export AZURE_SECRET_VALUE=<the sercet value from the Azure configuratipn step>
export AZURE_VAULT_URI=<the vault URI from the Azure configuratipn step>

To run the application, use the ./mvnw mn:run command, which starts the application on port 8080.

You can test the application in a web browser or with cURL.

Run from a terminal window to create a Genre:

curl -X "POST" "http://localhost:8080/genres" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{ "name": "music" }'

and run this to list the genres:

curl http://localhost:8080/genres/list

8. Cleaning Up

After you have finished this guide, you can clean up the resources you created on Azure Cloud so you won’t be billed for them in the future.

9. Next steps

Explore more features with Micronaut Guides.

Read more about:

10. Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.