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sp_control_dbmasterkey_password (Transact-SQL)

  • Стаття

Applies to: SQL Server Azure SQL Managed Instance

Adds or drops a credential containing the password needed to open a database master key (DMK).

Transact-SQL syntax conventions

Syntax

sp_control_dbmasterkey_password @db_name = 'db_name'
    , @password = 'password'
    , @action = { N'add' | N'drop' }

Arguments

@db_name = N'db_name'

Specifies the name of the database associated with this credential. Can't be a system database. @db_name is nvarchar.

@password = N'password'

Specifies the password of the DMK. @password is nvarchar.

@action = { N'add' | N'drop' }

Specifies an action for a credential for the specified database in the credential store. The value passed to @action is nvarchar.

Action Description
add Specifies that a credential for the specified database will be added to the credential store. The credential contains the password of the DMK.
drop Specifies that a credential for the specified database will be dropped from the credential store.

Remarks

When SQL Server needs a DMK to decrypt or encrypt a key, SQL Server tries to decrypt the DMK with the service master key (SMK) of the instance. If the decryption fails, SQL Server searches the credential store for credentials that have the same family GUID as the database for which it needs the key. SQL Server then tries to decrypt the DMK with each matching credential until the decryption succeeds or there are no more credentials.

Caution

Don't create a master key credential for a database that must be inaccessible to sa and other highly-privileged server principals. You can configure a database so that its key hierarchy can't be decrypted by the SMK. This option is supported as a defense-in-depth for databases that contain encrypted information that shouldn't be accessible to sa or other highly privileged server principals. Creating a credential for such a database removes this defense-in-depth, enabling sa and other highly privileged server principals to decrypt the database.

Credentials that are created by using sp_control_dbmasterkey_password are visible in the sys.master_key_passwords catalog view. The names of credentials that are created for DMKs have the following format: ##DBMKEY_<database_family_guid>_<random_password_guid>##. The password is stored as the credential secret. Each password added to the credential store has a matching row in sys.credentials.

You can't use sp_control_dbmasterkey_password to create a credential for the following system databases: master, model, msdb, or tempdb.

sp_control_dbmasterkey_password doesn't verify that the password can open the DMK of the specified database.

If you specify a password that is already stored in a credential for the specified database, sp_control_dbmasterkey_password fails.

Two databases from different server instances can share the same family GUID. If this occurs, the databases share the same DMK records in the credential store.

Parameters passed to sp_control_dbmasterkey_password don't appear in traces.

When you're using the credential that was added by using sp_control_dbmasterkey_password to open the DMK, the DMK is re-encrypted by the SMK. If the database is in read-only mode, the re-encryption operation fails, and the DMK remains unencrypted. For subsequent access to the DMK, you must use the OPEN MASTER KEY statement and a password. To avoid using a password, create the credential before you move the database to read-only mode.

Potential backward compatibility issue

Currently, the stored procedure doesn't check whether a key exists. This functionality is permitted for backward compatibility, but displays a warning. This behavior is deprecated. In a future release, the key must exist and the password used in the stored procedure sp_control_dbmasterkey_password must be the same password as one of the passwords used to encrypt the DMK.

Permissions

Requires membership in the sysadmin fixed server role, or execute permission directly on this stored procedure.

Examples

The Transact-SQL code samples in this article use the AdventureWorks2022 or AdventureWorksDW2022 sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.

A. Create a credential for the AdventureWorks master key

The following example creates a credential for the AdventureWorks2022 DMK, and saves the master key password as the secret in the credential. Because all parameters that are passed to sp_control_dbmasterkey_password must be of data type nvarchar, the text strings are converted with the casting operator N.

EXEC sp_control_dbmasterkey_password
    @db_name = N'AdventureWorks2022',
    @password = N'sdfjlkj#mM00sdfdsf98093258jJlfdk4',
    @action = N'add';
GO

B. Drop a credential for a database master key

The following example removes the credential created in example A. All parameters are required, including the password.

EXEC sp_control_dbmasterkey_password
    @db_name = N'AdventureWorks2022',
    @password = N'sdfjlkj#mM00sdfdsf98093258jJlfdk4',
    @action = N'drop';
GO

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