Azure Key Vault soft-delete overview
Key Vault's soft delete feature allows recovery of the deleted vaults and vault objects, known as soft-delete. Specifically, we address the following scenarios:
- Support for recoverable deletion of a key vault
- Support for recoverable deletion of key vault objects (ex. keys, secrets, certificates)
Azure Key Vaults are tracked resources, managed by Azure Resource Manager. Azure Resource Manager also specifies a well-defined behavior for deletion, which requires that a successful DELETE operation must result in that resource not being accessible anymore. The soft-delete feature addresses the recovery of the deleted object, whether the deletion was accidental or intentional.
In the typical scenario, a user may have inadvertently deleted a key vault or a key vault object; if that key vault or key vault object were to be recoverable for a predetermined period, the user may undo the deletion and recover their data.
In a different scenario, a rogue user may attempt to delete a key vault or a key vault object, such as a key inside a vault, to cause a business disruption. Separating the deletion of the key vault or key vault object from the actual deletion of the underlying data can be used as a safety measure by, for instance, restricting permissions on data deletion to a different, trusted role. This approach effectively requires quorum for an operation which might otherwise result in an immediate data loss.
With this feature, the DELETE operation on a key vault or key vault object is a soft-delete, effectively holding the resources for a given retention period (90 days), while giving the appearance that the object is deleted. The service further provides a mechanism for recovering the deleted object, essentially undoing the deletion.
When purge protection is on, a vault or an object in deleted state cannot be purged until the retention period of 90 days has passed. These vaults and objects can still be recovered, assuring customers that the retention policy will be followed.
Permanently deleting, purging, a key vault is possible via a POST operation on the proxy resource and requires special privileges. Generally, only the subscription owner will be able to purge a key vault. The POST operation triggers the immediate and irrecoverable deletion of that vault.
- When the Azure subscription has been marked as undeletable. In this case, only the service may then perform the actual deletion, and does so as a scheduled process.
- When the --enable-purge-protection flag is enabled on the vault itself. In this case, Key Vault will wait for 90 days from when the original secret object was marked for deletion to permanently delete the object.
Key vault recovery
Upon deleting a key vault, the service creates a proxy resource under the subscription, adding sufficient metadata for recovery. The proxy resource is a stored object, available in the same location as the deleted key vault.
Key vault object recovery
Upon deleting a key vault object, such as a key, the service will place the object in a deleted state, making it inaccessible to any retrieval operations. While in this state, the key vault object can only be listed, recovered, or forcefully/permanently deleted.
At the same time, Key Vault will schedule the deletion of the underlying data corresponding to the deleted key vault or key vault object for execution after a predetermined retention interval. The DNS record corresponding to the vault is also retained for the duration of the retention interval.
Soft-delete retention period
Soft deleted resources are retained for a set period of time, 90 days. During the soft-delete retention interval, the following apply:
- You may list all of the key vaults and key vault objects in the soft-delete state for your subscription as well as access deletion and recovery information about them.
- Only users with special permissions can list deleted vaults. We recommend that our users create a custom role with these special permissions for handling deleted vaults.
- A key vault with the same name cannot be created in the same location; correspondingly, a key vault object cannot be created in a given vault if that key vault contains an object with the same name and which is in a deleted state
- Only a specifically privileged user may restore a key vault or key vault object by issuing a recover command on the corresponding proxy resource.
- The user, member of the custom role, who has the privilege to create a key vault under the resource group can restore the vault.
- Only a specifically privileged user may forcibly delete a key vault or key vault object by issuing a delete command on the corresponding proxy resource.
Unless a key vault or key vault object is recovered, at the end of the retention interval the service performs a purge of the soft-deleted key vault or key vault object and its content. Resource deletion may not be rescheduled.
In general, when an object (a key vault or a key or a secret) is in deleted state, there are only two operations possible: 'purge' and 'recover'. All the other operations will fail. Therefore, even though the object exists, no operations can be performed and hence no usage will occur, so no bill. However there are following exceptions:
- 'purge' and 'recover' actions will count towards normal key vault operations and will be billed.
- If the object is an HSM-key, the 'HSM Protected key' charge per key version per month charge will apply if a key version has been used in last 30 days. After that, since the object is in deleted state no operations can be performed against it, so no charge will apply.
The following two guides offer the primary usage scenarios for using soft-delete.