Authentication

Securely authenticating your applications with Azure Event Hubs is crucial for protecting your data and controlling access. Event Hubs supports several authentication methods, allowing you to choose the most suitable option for your scenario.

1. Shared Access Signatures (SAS)

SAS provides a way to authenticate access to Event Hubs resources using tokens. These tokens are generated based on a shared secret key. SAS can be used at the namespace or entity level.

Creating SAS Policies

You can create and manage SAS policies through the Azure portal, Azure CLI, or programmatically using Azure SDKs.

In the Azure portal:

Navigate to your Event Hubs namespace.
Under "Settings", select "Shared access policies".
Click "Add" to create a new policy.
Specify a policy name, select the desired permissions (Send, Listen, Manage), and optionally configure key regeneration.

Using SAS Tokens

Once a policy is created, you can obtain the primary or secondary connection string, which contains the shared key and details for constructing the SAS token.

Most Event Hubs SDKs and REST APIs accept this connection string directly, handling the token generation and management automatically.

If you need to manually construct a SAS token (less common with SDKs), you'll typically use the shared key, a security token service (STS) endpoint, and specify the expiry time.

Note: It's recommended to use the shortest possible expiry times for SAS tokens to minimize the risk of compromise if a key is leaked.

2. Azure Active Directory (Azure AD) Authentication

Azure AD authentication is the recommended method for securing Event Hubs when interacting with other Azure services or for enterprise-grade security. It allows you to use identity-based access control.

Service Principals

Service principals represent applications or services that need to access Azure resources. You can grant specific permissions to a service principal for your Event Hubs namespace or entities.

Steps:

Register an application in Azure AD: Create an application registration in your Azure AD tenant.
Create a client secret or certificate: Generate a client secret or use a certificate for the application's authentication.
Grant role assignments: Assign the appropriate Azure RBAC roles (e.g., "Azure Event Hubs Data Sender", "Azure Event Hubs Data Receiver") to the service principal at the scope of your Event Hubs namespace or specific Event Hub.

Managed Identities

Managed identities are a feature of Azure AD that provide an identity for Azure services to use when connecting to other Azure services. This eliminates the need to manage credentials in your code.

Types of Managed Identities:

System-assigned: Enabled directly on an Azure resource (e.g., a Virtual Machine, Azure Functions). The identity is tied to the lifecycle of that resource.
User-assigned: Created as a standalone Azure resource and can be assigned to one or more Azure resources.

Steps:

Enable Managed Identity: For the Azure service hosting your application, enable either system-assigned or user-assigned managed identity.
Grant role assignments: Assign the necessary Azure RBAC roles to the managed identity for your Event Hubs namespace or entities.

Using Azure AD Credentials in SDKs

When using Azure SDKs with Azure AD authentication, you'll typically use the DefaultAzureCredential class or specific credential types like TokenCredential. This class automatically attempts to authenticate using various mechanisms, including environment variables, managed identities, and service principal credentials.

Example using C# with Azure.Identity:


using Azure.Identity;
using Azure.Messaging.EventHubs.Producer;

// Option 1: Using DefaultAzureCredential (recommended for flexibility)
TokenCredential credential = new DefaultAzureCredential();

// Option 2: Using Client Secret Credential (for Service Principals)
// string tenantId = "YOUR_TENANT_ID";
// string clientId = "YOUR_CLIENT_ID";
// string clientSecret = "YOUR_CLIENT_SECRET";
// TokenCredential credential = new ClientSecretCredential(tenantId, clientId, clientSecret);

string fullyQualifiedNamespace = "your-event-hubs-namespace.servicebus.windows.net";
string eventHubName = "your-event-hub-name";

EventHubProducerClient producerClient = new EventHubProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    credential);

// ... proceed to send events

Tip: Managed identities are generally preferred for applications hosted within Azure as they simplify credential management and enhance security.

3. Other Authentication Methods

IP Filtering

While not strictly an authentication method, IP filtering can act as a network-level security measure, allowing or denying access based on source IP addresses. This is configured at the Event Hubs namespace level.

Private Endpoints

For enhanced network security, you can use Private Endpoints to ensure that access to your Event Hubs namespace occurs entirely within your virtual network, eliminating public internet exposure.

Choosing the Right Authentication Method

For simple applications or quick prototypes: SAS can be sufficient, especially when using SDKs that abstract token management.
For production applications hosted within Azure: Managed Identities are the most secure and convenient option.
For applications running outside Azure or requiring granular control: Service Principals with Azure AD authentication provide robust identity management.

Always follow the principle of least privilege by granting only the necessary permissions to your applications.

For more detailed information and examples, refer to the official Azure Event Hubs documentation:

Azure Event Hubs Security Overview Authenticate with Managed Identities Authenticate with Service Principals