Subscription, Resource Group Lookups, And Template Deployments Under User Identity

Hey guys! As an architect diving deep into Azure deployments, one thing that's been on my mind is ensuring our deployments are executed under the context of the current user. It's a crucial aspect of maintaining security and auditability. Currently, all our ARM API operations are running under the app's identity, which is a managed identity. While this has its place, we need to shift towards a model where each operation is tied back to the logged-in user. This means ensuring that any action taken, whether it's looking up subscriptions, checking resource groups, or deploying templates, is done using the user's identity.

Why User Identity Matters

So, why is this switch to user identity so important? Let's break it down:

• Enhanced Security: When operations are performed under the app's identity, it's like having a single key to the kingdom. If that identity is compromised, an attacker could potentially perform a wide range of actions. By using user identity, we're segmenting access and limiting the blast radius of any potential security breach. Each user's actions are tied to their specific permissions, adding an extra layer of security.
• Improved Auditability: Imagine trying to track down who deployed a specific resource when all operations are under a single app identity. It's a nightmare! User identity provides a clear audit trail. We can easily see who initiated what, making it simpler to troubleshoot issues, identify unauthorized actions, and comply with regulatory requirements.
• Granular Access Control: User identity allows us to implement more granular access control. We can define specific roles and permissions for individual users or groups, ensuring that they only have access to the resources and actions they need. This principle of least privilege is a cornerstone of good security practices.
• Compliance: Many compliance regulations require that actions be attributable to specific users. By using user identity, we're better positioned to meet these requirements and demonstrate that we have proper controls in place.

Success Criteria for Implementation

To make this transition successful, we've outlined a few key criteria:

1. All ARM operations must use a token acquired for the scope https://management.azure.com/user_impersonation for the logged-in user: This is the heart of the change. We need to ensure that every call to the ARM API includes a token that represents the logged-in user. This token is obtained using the user_impersonation scope, which grants the application the ability to act on behalf of the user.
2. No ARM operations should use DefaultAzureCredential(): DefaultAzureCredential() is a convenient way to authenticate to Azure, but it can sometimes default to the app's identity. We need to explicitly avoid using it for ARM operations that should be performed under user identity. This ensures that we're always using the correct authentication context.

Diving Deeper into the Technical Aspects

Now, let's get a bit more technical and explore how we can achieve these success criteria.

Acquiring Tokens for User Impersonation

The key to performing operations under user identity is obtaining an access token with the https://management.azure.com/user_impersonation scope. There are several ways to do this, depending on the authentication flow being used.

• Interactive Login: If the user is interactively logging in (e.g., through a web browser), you can use libraries like MSAL (Microsoft Authentication Library) to acquire a token. MSAL provides methods for prompting the user to authenticate and consent to the application acting on their behalf. Once the user has authenticated, MSAL can retrieve an access token with the required scope.
• On-Behalf-Of Flow: In some scenarios, you might have a service that needs to call another service on behalf of the user. This is where the On-Behalf-Of (OBO) flow comes in. The first service receives a token representing the user, and then exchanges that token for a new token with the user_impersonation scope, which can be used to call the second service. This flow is particularly useful in multi-tier architectures.
• Azure CLI/PowerShell: If users are interacting with Azure through the CLI or PowerShell, these tools automatically handle token acquisition. You can leverage the user's existing credentials to perform ARM operations on their behalf.

Implementing the Change in Code

Let's look at some code snippets to illustrate how to implement this change. I'll use C# as an example, but the concepts apply to other languages as well.

First, let's look at how to acquire a token using MSAL:

using Microsoft.Identity.Client;

// Configuration
string clientId = "YOUR_CLIENT_ID";
string tenantId = "YOUR_TENANT_ID";
string[] scopes = { "https://management.azure.com/user_impersonation" };

// Build the MSAL application
IPublicClientApplication app = PublicClientApplicationBuilder.Create(clientId)
    .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)
    .WithRedirectUri("http://localhost") // Required for interactive login
    .Build();

// Acquire the token interactively
AuthenticationResult result = await app.AcquireTokenInteractive(scopes)
    .ExecuteAsync();

// The access token
string accessToken = result.AccessToken;

This code snippet demonstrates how to acquire a token interactively using MSAL. The AcquireTokenInteractive method prompts the user to log in and consent to the application's access. Once the token is acquired, you can use it to authenticate your ARM API calls.

Next, let's see how to use the token to call the ARM API. We'll use the Azure.ResourceManager library for this:

using Azure.ResourceManager;
using Azure.Identity;
using Azure.Core;

// Create a credential using the access token
var tokenCredential = new AzureCliCredential(new AzureCliCredentialOptions() { AuthenticationRecord = new AuthenticationRecord() { AccessToken = accessToken, Authority = new Uri({{content}}quot;https://login.microsoftonline.com/{tenantId}"), ClientId = clientId, TokenType = "Bearer" } });

// Create an ArmClient
ArmClient armClient = new ArmClient(tokenCredential);

// Get the subscription
SubscriptionResource subscription = await armClient.GetDefaultSubscriptionAsync();

// List resource groups
AsyncPageable<ResourceGroupResource> resourceGroups = subscription.GetResourceGroupsAsync();
await foreach (ResourceGroupResource resourceGroup in resourceGroups)
{
    Console.WriteLine(resourceGroup.Data.Name);
}

In this example, we create an ArmClient using a TokenCredential that's initialized with the access token we acquired earlier. This ensures that all subsequent operations performed using the ArmClient are executed under the user's identity.

Avoiding DefaultAzureCredential()

As mentioned earlier, we need to avoid using DefaultAzureCredential() for ARM operations that should be performed under user identity. DefaultAzureCredential() attempts to authenticate using a variety of methods, including managed identity, which is not what we want in this case. By explicitly using a TokenCredential with the user's access token, we ensure that we're always using the correct authentication context.

Template Deployments Under User Identity

Now, let's talk about template deployments. Deploying ARM templates under user identity is crucial for ensuring that resources are created and configured with the appropriate permissions. The process is similar to other ARM operations: we need to acquire a token with the user_impersonation scope and use it to authenticate the deployment request.

Here's an example of how to deploy a template using the Azure.ResourceManager library:

using Azure.ResourceManager.Resources;
using Azure.ResourceManager.Resources.Models;

// ... (Acquire access token as shown earlier)

// Get the resource group
ResourceGroupResource resourceGroup = await subscription.GetResourceGroupAsync("myResourceGroup");

// Read the template
string templateContent = File.ReadAllText("template.json");

// Create the deployment
ArmDeploymentContent deploymentContent = new ArmDeploymentContent(
    new ArmTemplateProperties(
        JsonSerializer.Deserialize<JsonElement>(templateContent)
    )
    {
        Mode = DeploymentMode.Incremental
    }
);

// Start the deployment
ArmDeployment deployment = await resourceGroup.GetArmDeployments().CreateOrUpdateAsync(WaitUntil.Completed, "myDeployment", deploymentContent);

Console.WriteLine({{content}}quot;Deployment status: {deployment.Data.Properties.ProvisioningState}");

In this example, we read the template content from a file and create an ArmDeploymentContent object. We then use the CreateOrUpdateAsync method to start the deployment. The key here is that the ArmClient and the ResourceGroupResource are authenticated using the user's access token, ensuring that the deployment is performed under their identity.

Best Practices and Considerations

As we implement this change, there are a few best practices and considerations to keep in mind:

• Token Caching: Access tokens have a limited lifespan. To avoid prompting the user to authenticate repeatedly, it's important to implement token caching. MSAL provides built-in token caching mechanisms that you can leverage.
• Error Handling: Token acquisition can fail for various reasons, such as the user denying consent or network connectivity issues. It's crucial to implement proper error handling and provide informative messages to the user.
• User Experience: While security is paramount, we also need to consider the user experience. Avoid prompting the user for credentials unnecessarily. Use techniques like silent token acquisition and token caching to minimize disruptions.
• Testing: Thoroughly test your implementation to ensure that operations are indeed being performed under user identity and that access control is working as expected. Use different user accounts with varying permissions to validate your setup.
• Monitoring and Auditing: Set up monitoring and auditing to track operations performed under user identity. This will help you identify any issues and ensure compliance with security policies.

Conclusion

Switching to user identity for ARM operations is a significant step towards enhancing security, improving auditability, and enabling granular access control. By following the guidelines and best practices outlined in this article, you can successfully implement this change and create a more secure and manageable Azure environment. Remember, it's all about ensuring that actions are tied back to the individual users who initiated them. Let's get this done, guys!