Επεξεργασία

Κοινή χρήση μέσω

TRUSTWORTHY database property

  • Άρθρο

Applies to: SQL Server Azure SQL Managed Instance

The TRUSTWORTHY database property is used to indicate whether the instance of SQL Server trusts the database and the contents within it. By default, this setting is OFF, but can be set to ON by using the ALTER DATABASE statement. For example: ALTER DATABASE AdventureWorks2022 SET TRUSTWORTHY ON;.

Note

To set this option, you must be a member of the sysadmin fixed server role.

We recommend that you leave the TRUSTWORTHY database property set to OFF to mitigate certain threats that can exist as a result of attaching a database that contains one of the following objects:

Both situations require a specific degree of privilege and are protected by appropriate mechanisms when they're used in the context of a database that is already attached to an instance of SQL Server. However, if the database is taken offline, if you have access to the database file you can potentially attach it to an instance of SQL Server of your choice and add malicious content to the database. When databases are detached and attached in SQL Server, certain permissions are set on the data and log files that restrict access to the database files.

Because a database that is attached to an instance of SQL Server can't be immediately trusted, the database isn't allowed to access resources beyond the scope of the database until the database is explicitly marked trustworthy. Therefore, if you back up or detach a database that has the TRUSTWORTHY option ON and you attach or restore the database to the same or another SQL Server instance, the TRUSTWORTHY property is set to OFF when attach or restore is completed. Also, modules that are designed to access resources outside the database, and assemblies with either the EXTERNAL_ACCESS and UNSAFE permission setting, have extra requirements to run successfully.

Note

By default, the TRUSTWORTHY setting is set to ON for the msdb database. If you change this setting from its default value, it might result in unexpected behavior by SQL Server components that use the msdb database.

If the TRUSTWORTHY setting is set to ON, and if the owner of the database is a member of a group that has administrative credentials, such as the sysadmin group, the database owner can then be able to create and run unsafe assemblies that can compromise the instance of the SQL Server.

More information

In an Internet Service Provider (ISP) environment (for example, in a web-hosting service), each customer is permitted to manage their own database and is restricted from accessing system databases and other user databases. For example, the databases of two competing companies could be hosted by the same ISP and exist in the same instance of SQL Server. Dangerous code could be added to a user database when the database is attached to its original instance, and the code would be enabled on the ISP instance when the database is deployed. This situation makes controlling cross-database access crucial.

If the same general entity owns and manages each database, it's still not a good practice to establish a trust relationship with a database unless an application-specific feature, such as a cross-database Service Broker communication, is required. A trust relationship between databases can be established by enabling cross-database ownership chaining or by marking a database as trusted by the instance using the TRUSTWORTHY property. The is_trustworthy_on column of the sys.databases catalog view indicates if a database has its TRUSTWORTHY property set.

The best practices for database ownership and trust include the following:

  • Have distinct owners for databases. Not all databases should be owned by the system administrator.
  • Limit the number of owners for each database.
  • Confer trust selectively.
  • Leave the cross db ownership chaining setting set to OFF unless multiple databases are deployed at a single unit.
  • Migrate usage to selective trust instead of using the TRUSTWORTHY property.

The following code sample can be used to obtain a list of databases that have the TRUSTWORTHY property set to ON and whose database owner belongs to the sysadmin server role.

SELECT SUSER_SNAME(owner_sid) AS DBOWNER,
    d.name AS DATABASENAME
FROM sys.server_principals r
INNER JOIN sys.server_role_members m ON r.principal_id = m.role_principal_id
INNER JOIN sys.server_principals p ON p.principal_id = m.member_principal_id
INNER JOIN sys.databases d ON suser_sname(d.owner_sid) = p.name
WHERE is_trustworthy_on = 1
    AND d.name NOT IN ('msdb')
    AND r.type = 'R'
    AND r.name = N'sysadmin';
GO

You can run the following query to determine the TRUSTWORTHY property of the msdb database:

SELECT name,
    trustworthy_setting = CASE is_trustworthy_on
        WHEN 1 THEN 'Trustworthy setting is ON for msdb'
        ELSE 'Trustworthy setting is OFF for msdb'
        END
FROM sys.databases
WHERE database_id = 4;
GO

If this query shows that the TRUSTWORTHY property is set to OFF, you can run the following query to set the TRUSTWORTHY property to ON.

ALTER DATABASE msdb SET TRUSTWORTHY ON;
GO

Warning

There are ways to elevate a user with the db_owner role to become a sysadmin when setting TRUSTWORTHY to ON. Use caution when using the TRUSTWORTHY property. The following SQL code can be used to obtain a list of database users in a database that are granted the db_owner role.

SELECT    roles.principal_id    AS RolePrincipalID
   ,    roles.name       AS RolePrincipalName
   ,    database_role_members.member_principal_id  AS MemberPrincipalID
   ,    members.name      AS MemberPrincipalName
FROM sys.database_role_members AS database_role_members  
JOIN sys.database_principals AS roles  
   ON database_role_members.role_principal_id = roles.principal_id  
JOIN sys.database_principals AS members  
   ON database_role_members.member_principal_id = members.principal_id where  roles.name='db_owner' and members.name <>'dbo'
GO

Next steps