Delegating Access with a Shared Access Signature
Updated: January 15, 2016
A shared access signature (SAS) is a URI that grants restricted access rights to Azure Storage resources. You can provide a shared access signature to clients who should not be trusted with your storage account key but to whom you wish to delegate access to certain storage account resources. By distributing a shared access signature URI to these clients, you can grant them access to a resource for a specified period of time, with a specified set of permissions.
The URI query parameters comprising the SAS token incorporate all of the information necessary to grant controlled access to a storage resource. A client who is in possession of the SAS can make a request against Azure Storage with just the SAS URI, and the information contained in the SAS token is used to authenticate the request.
Beginning with version 2015-04-05, Azure Storage supports two types of shared access signatures (SAS):
An account-level SAS, introduced with version 2015-04-05. The account SAS delegates access to resources in one or more of the storage services. All of the operations available via a service SAS are also available via an account SAS. Additionally, with the account SAS, you can delegate access to operations that apply to a given service, such as Get/Set Service Properties and Get Service Stats. You can also delegate access to read, write, and delete operations on blob containers, tables, queues, and file shares that are not permitted with a service SAS. See Constructing an Account SAS for more information about account SAS.
A service-level SAS. The service SAS delegates access to a resource in just one of the storage services: the Blob, Queue, Table, or File service. See Constructing a Service SAS and Service SAS Examples for more information about service SAS.
Stored access policies are currently not supported for account SAS.
Additionally, a service SAS can reference a stored access policy that provides an additional level of control over a set of signatures, including the ability to modify or revoke access to the resource if necessary. For more information on stored access policies, see Establishing a Stored Access Policy.