How to Configure Security in Microsoft SQL Server

Edited 2 weeks ago by ExtremeHow Editorial Team

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Microsoft SQL Server is a popular database management system that enables the storage, retrieval, and processing of data. However, like any system that manages sensitive data, security is extremely important. The purpose of configuring security is to protect data from unauthorized access and to ensure that only the right people have the authority to manage the data. This article provides a comprehensive guide on how to configure security in Microsoft SQL Server.

SQL Server security model

The security model in SQL Server is based on a combination of login accounts, users, and roles. These elements work together to ensure that only authorized users can access the database and perform certain operations. Let's take a closer look at each of these elements.

Login

A login is an account used to connect to a SQL Server instance. SQL Server supports several types of logins, including SQL Server authentication and Windows authentication. Windows authentication is generally preferred because it integrates with the Windows security model and is considered more secure.

To create a new login, follow these steps:

use master;
CREATE LOGIN [TestLogin] WITH PASSWORD='YourStrongPassword123';

In this example, a new SQL Server authenticated login named TestLogin is created. Always use a strong password for your login.

Users

Once a login is created for an instance, you can create a user in each specific database that this login can access. A user in the database is associated with the login, and this association allows the user to be authenticated when accessing the database.

To create a database user for the login we created earlier, use the following command:

use your database;
CREATE USER [TestUser] FOR LOGIN [TestLogin];

This command creates a user associated with the login TestLogin in the specified database (YourDatabase).

Roles

Roles are a collection of permissions that you can assign to a user or a group of users. They provide a simple way to manage permissions by grouping them into a role and then assigning users to that role.

SQL Server provides fixed server roles and fixed database roles. Fixed server roles apply to the entire instance of SQL Server, while fixed database roles apply only to a particular database.

Here's how you can add a user to a certain database role:

use your database;
EXECUTE sp_addrolemember 'db_datareader', 'TestUser';

This command adds TestUser to the db_datareader role, giving the user permission to read all data within the specified database.

Permissions

Permissions are rights to perform certain actions on SQL Server resources such as tables, views, or stored procedures. SQL Server provides a wide set of permissions, and you can grant or deny permissions to logins or users based on their security needs.

Suppose you want to allow a user to insert data into a specific table. You can run the following command:

use your database;
GRANT INSERT ON [YourTable] TO TestUser;

This command allows TestUser to insert data into the specified table (YourTable) in YourDatabase.

Encryption

SQL Server provides encryption capabilities to protect sensitive data being stored, transmitted, or exchanged between SQL Server instances and applications. This includes support for Transparent Data Encryption (TDE) and Always Encrypted.

Transparent data encryption

TDE helps keep data secure because it encrypts the data, which means the physical files on the disk are encrypted as well. However, the data still appears as plaintext to applications connecting to the database.

To implement TDE on a database, follow these steps:

use master;
Create master key encryption by password = 'YourStrongPassword123';
CREATE CERTIFICATE EncryptCert WITH SUBJECT = 'Database Encryption Certificate';
use your database;
Create database encryption key with algorithm = AES_256 Encryption by server certificate EncryptCert;
ALTER DATABASE YourDatabase SET ENCRYPTION ON;

This series of commands sets up database encryption for YourDatabase using a certificate.

Always Encrypted

Always Encrypted is designed to protect sensitive data within a SQL Server database. Only client applications that have the encryption keys can access plaintext data. Encryption occurs at the client level, so SQL Server never sees unencrypted values.

Setting up Always Encrypted requires using a column master key and a column encryption key. The column master key is stored outside of SQL Server, while the column encryption key is stored in SQL Server and is used to encrypt sensitive columns.

Typically, setting this up requires configuring encryption keys and using SQL Server Management Studio (SSMS) or a PowerShell script to change the table columns to use encryption.

Audit

Auditing in SQL Server is an integral part of security, as it helps track and log events that occur on the system. You can audit server-level events or database-level events, and SQL Server provides built-in audit objects to facilitate these activities.

Here's a basic example of creating an audit and associating it with a server-level object:

Create a server audit ServerAudit
in file(filepath = 'C:\AuditFiles\');

Change server audit ServerAudit
with (status = on);

Create a server audit specification ServerAuditSpec
ServerAudit for server audits
add(failed_login_group);

Change server audit specification ServerAuditSpec
with (status = on);

This script creates an audit that logs failed login attempts and outputs the log to the specified file location.

Security policies

SQL Server supports several security policies that help automate and manage security practices. Some notable security policies include Row-Level Security (RLS) and Dynamic Data Masking (DDM).

Row-Level Security (RLS)

RLS enables the implementation of fine-grained access control over rows in a table. This ensures that users have access only to rows for which they have authorization.

You can create RLS by defining predicate functions and security policies. The predicate function defines the logic used to filter rows.

CREATE FUNCTION dbo.fn_securitypredicate (@UserName AS sysname)
Returns Table
With SchemaBinding
As
select return 1 as result
where @username = USER_NAME();

Create a security policy SecurityPolicy
ADD FILTER PREDICATE dbo.fn_securitypredicate(username)
on your table
with (status = on);

This example filters access to YourTable based on username.

Dynamic Data Masking (DDM)

DDM is a built-in feature in SQL Server that promotes the process of hiding sensitive data when presenting data to unauthorized users. The data is stored in full, but is hidden or anonymized when retrieved.

Here's an example of setting up DDM on a table:

ALTER TABLE YourTable
ALTER COLUMN SensitiveColumn ADD MASKED WITH (FUNCTION = 'partial(2,"*",0)');

This masks the SensitiveColumn using the partial mask function, leaving the first two letters displayed and the rest of the letters masked.

Conclusion

Configuring security in Microsoft SQL Server involves several steps, from setting up logins, users, and roles to implementing encryption strategies, auditing, and security policies. Understanding the various tools and strategies at your disposal will enable you to create a strong security architecture for your SQL Server instance. Regular reviews and updates of your configuration ensure that your SQL Server security keeps pace with emerging threats.

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