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Define a stored access policy

  • Artikkeli

A stored access policy provides an additional level of control over service-level shared access signatures (SASs) on the server side. Establishing a stored access policy serves to group shared access signatures and to provide additional restrictions for signatures that are bound by the policy.

You can use a stored access policy to change the start time, expiry time, or permissions for a signature. You can also use a stored access policy to revoke a signature after it has been issued.

The following storage resources support stored access policies:

  • Blob containers
  • File shares
  • Queues
  • Tables

Note

A stored access policy on a container can be associated with a shared access signature that grants permissions to the container itself or to the blobs that it contains. Similarly, a stored access policy on a file share can be associated with a shared access signature that grants permissions to the share itself or to the files that it contains.

Stored access policies are not supported for the user delegation SAS or the account SAS.

Create or modify a stored access policy

The access policy for a shared access signature consists of the start time, expiry time, and permissions for the signature. You can specify either of the following options or combine them:

  • All of these parameters on the signature URI and none on the stored access policy
  • All of these parameters on the stored access policy and none on the URI

However, you can't specify a parameter on both the SAS token and the stored access policy.

To create or modify a stored access policy, call the Set ACL operation for the resource (see Set Container ACL, Set Queue ACL, Set Table ACL, or Set Share ACL) with a request body that specifies the terms of the access policy. The body of the request includes a unique signed identifier of your choosing, up to 64 characters in length. The body of the request also includes optional parameters of the access policy, as follows:

<?xml version="1.0" encoding="utf-8"?>  
<SignedIdentifiers>  
  <SignedIdentifier>
    <Id>unique-64-char-value</Id>  
    <AccessPolicy>  
      <Start>start-time</Start>  
      <Expiry>expiry-time</Expiry>  
      <Permission>abbreviated-permission-list</Permission>  
    </AccessPolicy>  
  </SignedIdentifier>  
</SignedIdentifiers>

You can set a maximum of five access policies on a container, table, queue, or share at a time. Each SignedIdentifier field, with its unique Id field, corresponds to one access policy. Trying to set more than five access policies at one time causes the service to return status code 400 (Bad Request).

Note

When you create or update a stored access policy on a container, table, queue, or share, the change might take up to 30 seconds to take effect. During this interval, requests against a shared access signature that's associated with the stored access policy might fail with status code 403 (Forbidden), until the access policy becomes active.

You can't specify range restrictions for table entities (startpk, startrk, endpk, and endrk) in a stored access policy.

Modify or revoke a stored access policy

To modify the parameters of a stored access policy, you can call the access control list (ACL) operation for the resource type to replace the existing policy. In that operation, specify a new start time, expiry time, or set of permissions.

For example, if your existing policy grants read and write permissions to a resource, you can modify it to grant only read permissions for all future requests. In this case, the signed identifier of the new policy, as specified by the ID field, would be identical to the signed identifier of the policy that you're replacing.

To revoke a stored access policy, you can delete it, rename it by changing the signed identifier, or change the expiry time to a value in the past. Changing the signed identifier breaks the associations between any existing signatures and the stored access policy. Changing the expiry time to a value in the past causes any associated signatures to expire. Deleting or modifying the stored access policy immediately affects all of the shared access signatures associated with it.

To remove a single access policy, call the resource's Set ACL operation. Pass in the set of signed identifiers that you want to maintain on the container. To remove all access policies from the resource, call the Set ACL operation with an empty request body.

See also