How to access Key Vault with Azure Managed Service Identity in node?

Question

I follow the instruction here to create an Managed Service Identity. So now in my environment variable, I have MSI_ENDPOINT and MSI_SECRET.

In my typescript (node.js) project, I imported the following project:

import {KeyVaultCredentials, KeyVaultClient} from "azure-keyvault";
import {AuthenticationContext, ErrorResponse, TokenResponse} from "adal-node";

If I wasn't using MSI, I could access my key vault using the following code:

let keyVaultCredentials = new KeyVaultCredentials(KeyVault.createAuthenticator(this.clientID, this.clientKey));
let keyVaultClient = new KeyVaultClient(keyVaultCredentials);
private static createAuthenticator(clientID: string, clientKey: string){
  return (challenge, callback) => {
  let context = new AuthenticationContext(challenge.authorization);
  return context.acquireTokenWithClientCredentials(
      challenge.resource,
      clientID,
      clientKey,
      function (err, tokenResponse:TokenResponse | ErrorResponse) {
          if (err) {
              CLogger.log("error", "Error occurred while acquiring token with key vault credentials: " + JSON.stringify(err));
              throw new Error("Error occurred while acquiring token with key vault credentials. Check log files");
          }
          if(<TokenResponse>tokenResponse){
              let authorizationValue = (<TokenResponse>tokenResponse).tokenType + " " + (<TokenResponse>tokenResponse).accessToken;
              return callback(null, authorizationValue);
          }
      });
  }
}

I have no idea how to get access token with MSI enabled, please help.

Answer 1

With the new Azure SDK for js, you can authenticate your application with managed service by implementing class DefaultAzureCredential from package @azure/identity.

const {DefaultAzureCredential} = require('@azure/identity');
const {SecretClient} = require('@azure/keyvault-secrets');

const credential = new DefaultAzureCredential();
  
const vaultName = "<key-vault-name>";
const url = `https://${vaultName}.vault.azure.net`;
  
const client = new SecretClient(url, credential);

client.setSecret(secretName, "MySecretValue");
........

It supports both service principal and managed identity authentication.

To run it on a local environment you must set three environment variables: AZURE_TENANT_ID, AZURE_CLIENT_ID and AZURE_CLIENT_SECRET to be able to connect with a service principal.

On Azure, if those variables are not defined, it will try to authenticate with managed identity.

There is a quickstart guide here.

Answer 2

Using the loginWithAppServiceMSI() method from ms-rest-azure will autodetect if you're on a WebApp and get the token from the MSI endpoint. Then, the code is simply:

function getKeyVaultCredentials(){
    return msRestAzure.loginWithAppServiceMSI({resource: 'https://vault.azure.net'});
}

function getKeyVaultSecret(credentials) {
    let keyVaultClient = new KeyVault.KeyVaultClient(credentials);
    return keyVaultClient.getSecret(KEY_VAULT_URI, 'secret', "");
}

getKeyVaultCredentials().then(
    getKeyVaultSecret
).then(function (secret){
    console.log(`Your secret value is: ${secret.value}.`);
}).catch(function (err) {
    throw (err);
});

I'd recommend checking the full documentation here