Authorize access to tables using Azure Active Directory
Azure Storage supports using Azure Active Directory (Azure AD) to authorize requests to table data. With Azure AD, you can use Azure role-based access control (Azure RBAC) to grant permissions to a security principal, which may be a user, group, or application service principal. The security principal is authenticated by Azure AD to return an OAuth 2.0 token. The token can then be used to authorize a request against the Table service.
Authorizing requests against Azure Storage with Azure AD provides superior security and ease of use over Shared Key authorization. Microsoft recommends using Azure AD authorization with your table applications when possible to assure access with minimum required privileges.
Authorization with Azure AD is available for all general-purpose in all public regions and national clouds. Only storage accounts created with the Azure Resource Manager deployment model support Azure AD authorization.
Overview of Azure AD for tables
When a security principal (a user, group, or application) attempts to access a table resource, the request must be authorized. With Azure AD, access to a resource is a two-step process. First, the security principal's identity is authenticated and an OAuth 2.0 token is returned. Next, the token is passed as part of a request to the Table service and used by the service to authorize access to the specified resource.
The authentication step requires that an application request an OAuth 2.0 access token at runtime. If an application is running from within an Azure entity such as an Azure VM, a virtual machine scale set, or an Azure Functions app, it can use a managed identity to access tables.
The authorization step requires that one or more Azure roles be assigned to the security principal. Azure Storage provides Azure roles that encompass common sets of permissions for table data. The roles that are assigned to a security principal determine the permissions that that principal will have. To learn more about assigning Azure roles for table access, see Assign an Azure role for access to table data.
The following table points to additional information for authorizing access to data in various scenarios:
Assign Azure roles for access rights
Azure Active Directory (Azure AD) authorizes access rights to secured resources through Azure role-based access control (Azure RBAC). Azure Storage defines a set of Azure built-in roles that encompass common sets of permissions used to access table data. You can also define custom roles for access to table data.
When an Azure role is assigned to an Azure AD security principal, Azure grants access to those resources for that security principal. An Azure AD security principal may be a user, a group, an application service principal, or a managed identity for Azure resources.
Before you assign an Azure RBAC role to a security principal, determine the scope of access that the security principal should have. Best practices dictate that it's always best to grant only the narrowest possible scope. Azure RBAC roles defined at a broader scope are inherited by the resources beneath them.
You can scope access to Azure table resources at the following levels, beginning with the narrowest scope:
- An individual table. At this scope, a role assignment applies to the specified table.
- The storage account. At this scope, a role assignment applies to all tables in the account.
- The resource group. At this scope, a role assignment applies to all of the tables in all of the storage accounts in the resource group.
- The subscription. At this scope, a role assignment applies to all of the tables in all of the storage accounts in all of the resource groups in the subscription.
- A management group. At this scope, a role assignment applies to all of the tables in all of the storage accounts in all of the resource groups in all of the subscriptions in the management group.
For more information about scope for Azure RBAC role assignments, see Understand scope for Azure RBAC.
Azure built-in roles for tables
Azure RBAC provides built-in roles for authorizing access to table data using Azure AD and OAuth. Built-in roles that provide permissions to tables in Azure Storage include:
- Storage Table Data Contributor: Use to grant read/write/delete permissions to Table storage resources.
- Storage Table Data Reader: Use to grant read-only permissions to Table storage resources.
To learn how to assign an Azure built-in role to a security principal, see Assign an Azure role for access to table data. To learn how to list Azure RBAC roles and their permissions, see List Azure role definitions.
For more information about how built-in roles are defined for Azure Storage, see Understand role definitions. For information about creating Azure custom roles, see Azure custom roles.
Only roles explicitly defined for data access permit a security principal to access table data. Built-in roles such as Owner, Contributor, and Storage Account Contributor permit a security principal to manage a storage account, but do not provide access to the table data within that account via Azure AD. However, if a role includes Microsoft.Storage/storageAccounts/listKeys/action, then a user to whom that role is assigned can access data in the storage account via Shared Key authorization with the account access keys.
For detailed information about Azure built-in roles for Azure Storage for both the data services and the management service, see the Storage section in Azure built-in roles for Azure RBAC. Additionally, for information about the different types of roles that provide permissions in Azure, see Azure roles, Azure AD roles, and classic subscription administrator roles.
Azure role assignments may take up to 30 minutes to propagate.
Access permissions for data operations
For details on the permissions required to call specific Table service operations, see Permissions for calling data operations.
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