Quickstart: Azure Key Vault client library for .NET (SDK v4)

03/12/2020
5 minutes to read

Get started with the Azure Key Vault client library for .NET. Follow the steps below to install the package and try out example code for basic tasks.

Azure Key Vault helps safeguard cryptographic keys and secrets used by cloud applications and services. Use the Key Vault client library for .NET to:

Increase security and control over keys and passwords.
Create and import encryption keys in minutes.
Reduce latency with cloud scale and global redundancy.
Simplify and automate tasks for TLS/SSL certificates.
Use FIPS 140-2 Level 2 validated HSMs.

API reference documentation | Library source code | Package (NuGet)

Prerequisites

An Azure subscription - create one for free.
The .NET Core 3.1 SDK or later.
Azure CLI or Azure PowerShell

This quickstart assumes you are running dotnet, Azure CLI, and Windows commands in a Windows terminal (such as PowerShell Core, Windows PowerShell, or the Azure Cloud Shell).

Setting up

Create new .NET console app

In a console window, use the dotnet new command to create a new .NET console app with the name key-vault-console-app.

dotnet new console -n key-vault-console-app

Change your directory to the newly created app folder. You can build the application with:

dotnet build

The build output should contain no warnings or errors.

Build succeeded.
 0 Warning(s)
 0 Error(s)

Install the package

From the console window, install the Azure Key Vault client library for .NET:

dotnet add package Azure.Security.KeyVault.Secrets

For this quickstart, you will need to install the following packages as well:

dotnet add package Azure.Identity

Create a resource group and key vault

This quickstart uses a pre-created Azure key vault. You can create a key vault by following the steps in the Azure CLI quickstart, Azure PowerShell quickstart, or Azure portal quickstart.

Alternatively, you can simply run the Azure CLI or Azure PowerShell commands below.

Important

Each key vault must have a unique name. Replace with the name of your key vault in the following examples.

az group create --name "myResourceGroup" -l "EastUS"

az keyvault create --name "<your-unique-keyvault-name>" -g "myResourceGroup"

New-AzResourceGroup -Name myResourceGroup -Location EastUS

New-AzKeyVault -Name "<your-unique-keyvault-name>" -ResourceGroupName "myResourceGroup" -Location "EastUS"

Create a service principal

The simplest way to authenticate a cloud-based application is with a managed identity; see Use an App Service managed identity to access Azure Key Vault for details.

For the sake of simplicity however, this quickstart creates a desktop application, which requires the use of a service principal and an access control policy. Your service principal requires a unique name in the format "http://<my-unique-service-principal-name>".

Create a service principal using the Azure CLI az ad sp create-for-rbac command:

az ad sp create-for-rbac -n "http://<my-unique-service-principal-name>" --sdk-auth

This operation will return a series of key / value pairs.

{
  "clientId": "7da18cae-779c-41fc-992e-0527854c6583",
  "clientSecret": "b421b443-1669-4cd7-b5b1-394d5c945002",
  "subscriptionId": "443e30da-feca-47c4-b68f-1636b75e16b3",
  "tenantId": "35ad10f1-7799-4766-9acf-f2d946161b77",
  "activeDirectoryEndpointUrl": "https://login.microsoftonline.com",
  "resourceManagerEndpointUrl": "https://management.azure.com/",
  "sqlManagementEndpointUrl": "https://management.core.windows.net:8443/",
  "galleryEndpointUrl": "https://gallery.azure.com/",
  "managementEndpointUrl": "https://management.core.windows.net/"
}

Give the service principal access to your key vault

Create an access policy for your key vault that grants permission to your service principal by passing clientId to the az keyvault set-policy command. Give the service principal get, list, and set permissions for both keys and secrets.

az keyvault set-policy -n <your-unique-keyvault-name> --spn <clientId-of-your-service-principal> --secret-permissions delete get list set --key-permissions create decrypt delete encrypt get list unwrapKey wrapKey

Set environmental variables

The DefaultAzureCredential method in our application relies on three environmental variables: AZURE_CLIENT_ID, AZURE_CLIENT_SECRET, and AZURE_TENANT_ID. Set these variables to the clientId, clientSecret, and tenantId values that were returned in the "Create a service principal" step using the export VARNAME=VALUE format. (This method only sets the variables for your current shell and processes created from the shell; to permanently add these variables to your environment, edit your /etc/environment file.)

You will also need to save your key vault name as an environment variable called KEY_VAULT_NAME.

export AZURE_CLIENT_ID=<your-clientID>

export AZURE_CLIENT_SECRET=<your-clientSecret>

export AZURE_TENANT_ID=<your-tenantId>

export KEY_VAULT_NAME=<your-key-vault-name>

Object model

The Azure Key Vault client library for .NET allows you to manage keys and related assets such as certificates and secrets. The code samples below will show you how to create a client, set a secret, retrieve a secret, and delete a secret.

The entire console app is available at https://github.com/Azure-Samples/key-vault-dotnet-core-quickstart/tree/master/key-vault-console-app.

Code examples

Add directives

Add the following directives to the top of your code:

using System;
using Azure.Identity;
using Azure.Security.KeyVault.Secrets;

Authenticate and create a client

Authenticating to your key vault and creating a key vault client depends on the environmental variables in the Set environmental variables step above. The name of your key vault is expanded to the key vault URI, in the format "https://<your-key-vault-name>.vault.azure.net". Below code is using 'DefaultAzureCredential()' for authentication to key vault, which is reading environment variables to retrieve access token.

string keyVaultName = Environment.GetEnvironmentVariable("KEY_VAULT_NAME");
var kvUri = "https://" + keyVaultName + ".vault.azure.net";

var client = new SecretClient(new Uri(kvUri), new DefaultAzureCredential());

Save a secret

Now that your application is authenticated, you can put a secret into your keyvault using the client.SetSecret method This requires a name for the secret -- we're using "mySecret" in this sample.

client.SetSecret(secretName, secretValue);

You can verify that the secret has been set with the az keyvault secret show command:

az keyvault secret show --vault-name <your-unique-keyvault-name> --name mySecret

(Get-AzKeyVaultSecret -VaultName <your-unique-keyvault-name> -Name mySecret).SecretValueText

Retrieve a secret

You can now retrieve the previously set value with the client.GetSecret method.

KeyVaultSecret secret = client.GetSecret(secretName);

Your secret is now saved as secret.Value.

Delete a secret

Finally, let's delete the secret from your key vault with the client.DeleteSecret method.

client.StartDeleteSecret(secretName);

You can verify that the secret is gone with the az keyvault secret show command:

az keyvault secret show --vault-name <your-unique-keyvault-name> --name mySecret

(Get-AzKeyVaultSecret -VaultName <your-unique-keyvault-name> -Name mySecret).SecretValueText

Clean up resources

When no longer needed, you can use the Azure CLI or Azure PowerShell to remove your key vault and the corresponding resource group.

Delete a Key Vault

az keyvault delete --name <your-unique-keyvault-name>

Remove-AzKeyVault -VaultName <your-unique-keyvault-name>

Purge a Key Vault

az keyvault purge --location eastus --name <your-unique-keyvault-name>

Remove-AzKeyVault -VaultName <your-unique-keyvault-name> -InRemovedState -Location eastus

Delete a resource group

az group delete -g "myResourceGroup"

Remove-AzResourceGroup -Name "myResourceGroup"

Sample code

using System;
using Azure.Identity;
using Azure.Security.KeyVault.Secrets;

namespace key_vault_console_app
{
    class Program
    {
        static void Main(string[] args)
        {
            string secretName = "mySecret";

            string keyVaultName = Environment.GetEnvironmentVariable("KEY_VAULT_NAME");
            var kvUri = "https://" + keyVaultName + ".vault.azure.net";

            var client = new SecretClient(new Uri(kvUri), new DefaultAzureCredential());

            Console.Write("Input the value of your secret > ");
            string secretValue = Console.ReadLine();

            Console.Write("Creating a secret in " + keyVaultName + " called '" + secretName + "' with the value '" + secretValue + "` ...");

            client.SetSecret(secretName, secretValue);

            Console.WriteLine(" done.");

            Console.WriteLine("Forgetting your secret.");
            secretValue = "";
            Console.WriteLine("Your secret is '" + secretValue + "'.");

            Console.WriteLine("Retrieving your secret from " + keyVaultName + ".");

            KeyVaultSecret secret = client.GetSecret(secretName);

            Console.WriteLine("Your secret is '" + secret.Value + "'.");

            Console.Write("Deleting your secret from " + keyVaultName + " ...");

            client.StartDeleteSecret(secretName);

            System.Threading.Thread.Sleep(5000);
            Console.WriteLine(" done.");

        }
    }
}

Next steps

In this quickstart you created a key vault, stored a secret, and retrieved that secret. See the entire console app in GitHub.

To learn more about Key Vault and how to integrate it with your applications, continue on to the articles below.

Read an Overview of Azure Key Vault
See the Azure Key Vault developer's guide
Review Azure Key Vault best practices