Service Bus authentication and authorization

There are two ways to authenticate and authorize access to Azure Service Bus resources: Azure Activity Directory (Azure AD) and Shared Access Signatures (SAS). This article gives you details on using these two types of security mechanisms.

Azure Active Directory

Azure AD integration for Service Bus resources provides Azure role-based access control (Azure RBAC) for fine-grained control over a client’s access to resources. You can use Azure RBAC to grant permissions to a security principal, which may be a user, a group, or an application service principal. The security principal is authenticated by Azure AD to return an OAuth 2.0 token. The token can be used to authorize a request to access an Service Bus resource (queue, topic, etc.).

For more information about authenticating with Azure AD, see the following articles:

Note

Service Bus REST API supports OAuth authentication with Azure AD.

Important

Authorizing users or applications using OAuth 2.0 token returned by Azure AD provides superior security and ease of use over shared access signatures (SAS). With Azure AD, there is no need to store the tokens in your code and risk potential security vulnerabilities. We recommend that you use using Azure AD with your Azure Service Bus applications when possible.

Shared access signature

SAS authentication enables you to grant a user access to Service Bus resources, with specific rights. SAS authentication in Service Bus involves the configuration of a cryptographic key with associated rights on a Service Bus resource. Clients can then gain access to that resource by presenting a SAS token, which consists of the resource URI being accessed and an expiry signed with the configured key.

You can configure keys for SAS on a Service Bus namespace. The key applies to all messaging entities within that namespace. You can also configure keys on Service Bus queues and topics. SAS is also supported on Azure Relay.

To use SAS, you can configure a SharedAccessAuthorizationRule object on a namespace, queue, or topic. This rule consists of the following elements:

  • KeyName: identifies the rule.
  • PrimaryKey: a cryptographic key used to sign/validate SAS tokens.
  • SecondaryKey: a cryptographic key used to sign/validate SAS tokens.
  • Rights: represents the collection of Listen, Send, or Manage rights granted.

Authorization rules configured at the namespace level can grant access to all entities in a namespace for clients with tokens signed using the corresponding key. You can configure up to 12 such authorization rules on a Service Bus namespace, queue, or topic. By default, a SharedAccessAuthorizationRule with all rights is configured for every namespace when it is first provisioned.

To access an entity, the client requires a SAS token generated using a specific SharedAccessAuthorizationRule. The SAS token is generated using the HMAC-SHA256 of a resource string that consists of the resource URI to which access is claimed, and an expiry with a cryptographic key associated with the authorization rule.

SAS authentication support for Service Bus is included in the Azure .NET SDK versions 2.0 and later. SAS includes support for a SharedAccessAuthorizationRule. All APIs that accept a connection string as a parameter include support for SAS connection strings.

Important

If you are using Azure Active Directory Access Control (also known as Access Control Service or ACS) with Service Bus, note that the support for this method is now limited and you should migrate your application to use SAS or use OAuth 2.0 authentication with Azure AD (recommended).For more information about deprecation of ACS, see this blog post.

Next steps

For more information about authenticating with Azure AD, see the following articles:

For more information about authenticating with SAS, see the following articles: