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 Propertiesand
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.