Ensure only the default permissions specified by Microsoft are granted to the public server role

MediumLevel 1Automatedmssql

Description

public is a special fixed server role containing all logins. Unlike other fixed server roles, permissions can be changed for the public role. In keeping with the principle of least privileges, the public server role should not be used to grant permissions at the server scope as these would be inherited by all users. Every SQL Server login belongs to the public role and cannot be removed from this role. Therefore, any permissions granted to this role will be available to all logins unless they have been explicitly denied to specific logins or user-defined server roles.

How it is checked

Audit method: SQL query

sql_query

sqlcmd -b -h -1 -W -Q "SET NOCOUNT ON; SELECT COUNT(*) FROM master.sys.server_permissions WHERE (grantee_principal_id = SUSER_SID(N'public') AND state_desc LIKE 'GRANT%') AND NOT (state_desc = 'GRANT' AND permission_name = 'VIEW ANY DATABASE' AND class_desc = 'SERVER') AND NOT (state_desc = 'GRANT' AND permission_name = 'CONNECT' AND class_desc = 'ENDPOINT' AND major_id IN (2,3,4,5));"

Expected output: 0

How it is fixed

Fix method: Guidance or infrastructure patch

1. Add the extraneous permissions found in the Audit query results to the specific logins to user-defined server roles which require the access. 2. Revoke the <permission_name> from the public role as shown below USE [master] GO REVOKE <permission_name> FROM public; GO

Properties

Operating systems: Any
Tags: access-controliammssqlsqlserver-2022
Reference: CIS Microsoft SQL Server 2022 Benchmark v1.3.0 - 3.8 Ensure only the default permissions specified by Microsoft are granted to the public server role

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target mssql