Authenticate Securely to Azure Services

Azure.Identity (.NET)

Authentication library for Azure SDK clients using Microsoft Entra ID (formerly Azure AD).

Installation

dotnet add package Azure.Identity

### For ASP.NET Core
dotnet add package Microsoft.Extensions.Azure

### For brokered authentication (Windows)
dotnet add package Azure.Identity.Broker

Current Versions: Stable v1.17.1, Preview v1.18.0-beta.2

Environment Variables

Service Principal with Secret

AZURE_CLIENT_ID=<application-client-id>
AZURE_TENANT_ID=<directory-tenant-id>
AZURE_CLIENT_SECRET=<client-secret-value>

Service Principal with Certificate

AZURE_CLIENT_ID=<application-client-id>
AZURE_TENANT_ID=<directory-tenant-id>
AZURE_CLIENT_CERTIFICATE_PATH=<path-to-pfx-or-pem>
AZURE_CLIENT_CERTIFICATE_PASSWORD=<certificate-password>  # Optional

Managed Identity

AZURE_CLIENT_ID=<user-assigned-managed-identity-client-id>  # Only for user-assigned

DefaultAzureCredential

The recommended credential for most scenarios. Tries multiple authentication methods in order:

Basic Usage

using Azure.Identity;
using Azure.Storage.Blobs;

var credential = new DefaultAzureCredential();
var blobClient = new BlobServiceClient(
    new Uri("https://myaccount.blob.core.windows.net"),
    credential);

ASP.NET Core with Dependency Injection

using Azure.Identity;
using Microsoft.Extensions.Azure;

builder.Services.AddAzureClients(clientBuilder =>
{
    clientBuilder.AddBlobServiceClient(
        new Uri("https://myaccount.blob.core.windows.net"));
    clientBuilder.AddSecretClient(
        new Uri("https://myvault.vault.azure.net"));
    
    // Uses DefaultAzureCredential by default
    clientBuilder.UseCredential(new DefaultAzureCredential());
});

Customizing DefaultAzureCredential

var credential = new DefaultAzureCredential(
    new DefaultAzureCredentialOptions
    {
        ExcludeEnvironmentCredential = true,
        ExcludeManagedIdentityCredential = false,
        ExcludeVisualStudioCredential = false,
        ExcludeAzureCliCredential = false,
        ExcludeInteractiveBrowserCredential = false, // Enable interactive
        TenantId = "<tenant-id>",
        ManagedIdentityClientId = "<user-assigned-mi-client-id>"
    });

Credential Types

ManagedIdentityCredential (Production)

// System-assigned managed identity
var credential = new ManagedIdentityCredential(ManagedIdentityId.SystemAssigned);

// User-assigned by client ID
var credential = new ManagedIdentityCredential(
    ManagedIdentityId.FromUserAssignedClientId("<client-id>"));

// User-assigned by resource ID
var credential = new ManagedIdentityCredential(
    ManagedIdentityId.FromUserAssignedResourceId("<resource-id>"));

ClientSecretCredential

var credential = new ClientSecretCredential(
    tenantId: "<tenant-id>",
    clientId: "<client-id>",
    clientSecret: "<client-secret>");

var client = new SecretClient(
    new Uri("https://myvault.vault.azure.net"),
    credential);

ClientCertificateCredential

var certificate = X509CertificateLoader.LoadCertificateFromFile("MyCertificate.pfx");
var credential = new ClientCertificateCredential(
    tenantId: "<tenant-id>",
    clientId: "<client-id>",
    certificate);

ChainedTokenCredential (Custom Chain)

var credential = new ChainedTokenCredential(
    new ManagedIdentityCredential(),
    new AzureCliCredential());

var client = new SecretClient(
    new Uri("https://myvault.vault.azure.net"),
    credential);

Developer Credentials

// Azure CLI
var credential = new AzureCliCredential();

// Azure PowerShell
var credential = new AzurePowerShellCredential();

// Azure Developer CLI (azd)
var credential = new AzureDeveloperCliCredential();

// Visual Studio
var credential = new VisualStudioCredential();

// Interactive Browser
var credential = new InteractiveBrowserCredential();

Environment-Based Configuration

// Production vs Development
TokenCredential credential = builder.Environment.IsProduction()
    ? new ManagedIdentityCredential("<client-id>")
    : new DefaultAzureCredential();

Sovereign Clouds

var credential = new DefaultAzureCredential(
    new DefaultAzureCredentialOptions
    {
        AuthorityHost = AzureAuthorityHosts.AzureGovernment
    });

// Available authority hosts:
// AzureAuthorityHosts.AzurePublicCloud (default)
// AzureAuthorityHosts.AzureGovernment
// AzureAuthorityHosts.AzureChina
// AzureAuthorityHosts.AzureGermany

Credential Types Reference

Best Practices

1. Use Deterministic Credentials in Production

// Development
var devCredential = new DefaultAzureCredential();

// Production - use specific credential
var prodCredential = new ManagedIdentityCredential("<client-id>");

2. Reuse Credential Instances

// Good: Single credential instance shared across clients
var credential = new DefaultAzureCredential();
var blobClient = new BlobServiceClient(blobUri, credential);
var secretClient = new SecretClient(vaultUri, credential);

3. Configure Retry Policies

var options = new ManagedIdentityCredentialOptions(
    ManagedIdentityId.FromUserAssignedClientId(clientId))
{
    Retry =
    {
        MaxRetries = 3,
        Delay = TimeSpan.FromSeconds(0.5),
    }
};
var credential = new ManagedIdentityCredential(options);

4. Enable Logging for Debugging

using Azure.Core.Diagnostics;

using AzureEventSourceListener listener = new((args, message) =>
{
    if (args is { EventSource.Name: "Azure-Identity" })
    {
        Console.WriteLine(message);
    }
}, EventLevel.LogAlways);

Error Handling

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

var client = new SecretClient(
    new Uri("https://myvault.vault.azure.net"),
    new DefaultAzureCredential());

try
{
    KeyVaultSecret secret = await client.GetSecretAsync("secret1");
}
catch (AuthenticationFailedException e)
{
    Console.WriteLine($"Authentication Failed: {e.Message}");
}
catch (CredentialUnavailableException e)
{
    Console.WriteLine($"Credential Unavailable: {e.Message}");
}

Key Exceptions

Managed Identity Support

Supported Azure services:

• Azure App Service and Azure Functions
• Azure Arc
• Azure Cloud Shell
• Azure Kubernetes Service (AKS)
• Azure Service Fabric
• Azure Virtual Machines
• Azure Virtual Machine Scale Sets

Thread Safety

All credential implementations are thread-safe. A single credential instance can be safely shared across multiple clients and threads.

Related SDKs

Reference Links

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.