SQL Server must prevent non-privileged users from executing privileged functions, to include disabling, circumventing, or altering implemented security safeguards/countermeasures.

From MS SQL Server 2016 Instance Security Technical Implementation Guide

Part of SRG-APP-000340-DB-000304

Associated with: CCI-002235

SV-93925r1_rule SQL Server must prevent non-privileged users from executing privileged functions, to include disabling, circumventing, or altering implemented security safeguards/countermeasures.

Vulnerability discussion

Preventing non-privileged users from executing privileged functions mitigates the risk that unauthorized individuals or processes may gain unnecessary access to information or privileges. System documentation should include a definition of the functionality considered privileged. Depending on circumstances, privileged functions can include, for example, establishing accounts, performing system integrity checks, or administering cryptographic key management activities. Non-privileged users are individuals that do not possess appropriate authorizations. Circumventing intrusion detection and prevention mechanisms or malicious code protection mechanisms are examples of privileged functions that require protection from non-privileged users. A privileged function in SQL Server/database context is any operation that modifies the structure of the database, its built-in logic, or its security settings. This would include all Data Definition Language (DDL) statements and all security-related statements. In an SQL environment, it encompasses, but is not necessarily limited to: CREATE ALTER DROP GRANT REVOKE DENY There may also be Data Manipulation Language (DML) statements that, subject to context, should be regarded as privileged. Possible examples include: TRUNCATE TABLE; DELETE, or DELETE affecting more than n rows, for some n, or DELETE without a WHERE clause; UPDATE or UPDATE affecting more than n rows, for some n, or UPDATE without a WHERE clause; Any SELECT, INSERT, UPDATE, or DELETE to an application-defined security table executed by other than a security principal. Depending on the capabilities of SQL Server and the design of the database and associated applications, the prevention of unauthorized use of privileged functions may be achieved by means of DBMS security features, database triggers, other mechanisms, or a combination of these.

Check content

Review server-level securables and built-in role membership to ensure only authorized users have privileged access and the ability to create server-level objects and grant permissions to themselves or others. Review the system documentation to determine the required levels of protection for DBMS server securables, by type of login. Review the permissions in place on the server. If the actual permissions do not match the documented requirements, this is a finding. Get all permission assignments to logins and roles: SELECT DISTINCT CASE WHEN SP.class_desc IS NOT NULL THEN CASE WHEN SP.class_desc = 'SERVER' AND S.is_linked = 0 THEN 'SERVER' WHEN SP.class_desc = 'SERVER' AND S.is_linked = 1 THEN 'SERVER (linked)' ELSE SP.class_desc END WHEN E.name IS NOT NULL THEN 'ENDPOINT' WHEN S.name IS NOT NULL AND S.is_linked = 0 THEN 'SERVER' WHEN S.name IS NOT NULL AND S.is_linked = 1 THEN 'SERVER (linked)' WHEN P.name IS NOT NULL THEN 'SERVER_PRINCIPAL' ELSE '???' END AS [Securable Class], CASE WHEN E.name IS NOT NULL THEN E.name WHEN S.name IS NOT NULL THEN S.name WHEN P.name IS NOT NULL THEN P.name ELSE '???' END AS [Securable], P1.name AS [Grantee], P1.type_desc AS [Grantee Type], sp.permission_name AS [Permission], sp.state_desc AS [State], P2.name AS [Grantor], P2.type_desc AS [Grantor Type] FROM sys.server_permissions SP INNER JOIN sys.server_principals P1 ON P1.principal_id = SP.grantee_principal_id INNER JOIN sys.server_principals P2 ON P2.principal_id = SP.grantor_principal_id FULL OUTER JOIN sys.servers S ON SP.class_desc = 'SERVER' AND S.server_id = SP.major_id FULL OUTER JOIN sys.endpoints E ON SP.class_desc = 'ENDPOINT' AND E.endpoint_id = SP.major_id FULL OUTER JOIN sys.server_principals P ON SP.class_desc = 'SERVER_PRINCIPAL' AND P.principal_id = SP.major_id Get all server role memberships: SELECT R.name AS [Role], M.name AS [Member] FROM sys.server_role_members X INNER JOIN sys.server_principals R ON R.principal_id = X.role_principal_id INNER JOIN sys.server_principals M ON M.principal_id = X.member_principal_id The CONTROL SERVER permission is similar but not identical to the sysadmin fixed server role. Permissions do not imply role memberships and role memberships do not grant permissions. (e.g., CONTROL SERVER does not imply membership in the sysadmin fixed server role.) Ensure only the documented and approved logins have privileged functions in SQL Server. If the current configuration does not match the documented baseline, this is a finding.

Fix text

Restrict the granting of permissions to server-level securables to only those authorized. Most notably, members of sysadmin and securityadmin built-in instance-level roles, CONTROL SERVER permission, and use of the GRANT with GRANT permission.

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