Azure Identity library for .NET

Authentication library for Azure SDK clients using Microsoft Entra ID.

Installation

dotnet add package Azure.Identity

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

# For brokered authentication and Visual Studio Code credential support
dotnet add package Azure.Identity.Broker

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. See DefaultAzureCredential overview for the current credential chain order and defaults.

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>"));

// User-assigned by object ID
var credential = new ManagedIdentityCredential(
    ManagedIdentityId.FromUserAssignedObjectId("<object-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

Credential Types Reference

Category	Credential	Purpose
Chains	DefaultAzureCredential	Preconfigured chain for dev-to-prod
	ChainedTokenCredential	Custom credential chain
Azure-Hosted	ManagedIdentityCredential	Azure managed identity
	WorkloadIdentityCredential	Kubernetes workload identity
	EnvironmentCredential	Environment variables
Service Principal	ClientSecretCredential	Client ID + secret
	ClientCertificateCredential	Client ID + certificate
	ClientAssertionCredential	Signed client assertion
User	InteractiveBrowserCredential	Browser-based auth
	DeviceCodeCredential	Device code flow
	OnBehalfOfCredential	Delegated identity
Developer	AzureCliCredential	Azure CLI
	AzurePowerShellCredential	Azure PowerShell
	AzureDeveloperCliCredential	Azure Developer CLI
	VisualStudioCredential	Visual Studio

Best Practices

1. Use Deterministic Credentials in Production

// Development
var devCredential = new DefaultAzureCredential();

// Production - use specific credential
var prodCredential = new ManagedIdentityCredential(
    ManagedIdentityId.FromUserAssignedClientId("<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

Exception	Description
AuthenticationFailedException	Base exception for authentication errors
CredentialUnavailableException	Credential cannot authenticate in current environment
AuthenticationRequiredException	Interactive authentication is required

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 packages

Package	Purpose	Install
Azure.Identity	Authentication (this library)	dotnet add package Azure.Identity
Microsoft.Extensions.Azure	DI integration	dotnet add package Microsoft.Extensions.Azure
Azure.Identity.Broker	Brokered auth	dotnet add package Azure.Identity.Broker

Reference Links

Resource	URL
NuGet Package	https://www.nuget.org/packages/Azure.Identity
API Reference	https://learn.microsoft.com/dotnet/api/azure.identity
Credential Chains	https://aka.ms/azsdk/net/identity/credential-chains
Best Practices	https://learn.microsoft.com/dotnet/azure/sdk/authentication/best-practices
GitHub Source	https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/identity/Azure.Identity