Azure SQL Database Security: Authentication

Introduction

Authentication is the process of verifying the identity of a user or application attempting to connect to Azure SQL Database. Secure authentication is a cornerstone of protecting your sensitive data. Azure SQL Database supports two primary authentication mechanisms: SQL Authentication and Azure Active Directory (Azure AD) Authentication.

This document provides a comprehensive reference for understanding and implementing authentication for Azure SQL Database.

Authentication Methods

Azure SQL Database offers flexible authentication options to suit various security and management requirements:

SQL Authentication: Uses a username and password to authenticate users.
Azure Active Directory (Azure AD) Authentication: Leverages Azure AD identities (users, groups, service principals) for authentication, providing enhanced security and centralized management.

SQL Authentication

SQL Authentication is a straightforward method that relies on a username and password combination created directly within SQL Database. It is suitable for simple scenarios or when Azure AD integration is not feasible.

Creating Logins

Logins are server-level principals that allow you to connect to the SQL Database server. They are created using T-SQL commands.


CREATE LOGIN MyLogin WITH PASSWORD = 'ComplexPassword123!';
GO

For enhanced security, always use strong, complex passwords.

Creating Users

Once a login is created, you need to create a database user associated with that login to grant access to specific databases.


USE MyDatabase;
GO
CREATE USER MyUser FOR LOGIN MyLogin;
GO

Permissions

After creating a user, you can grant specific permissions to control what actions they can perform within the database.


-- Grant SELECT permission on a table
GRANT SELECT ON dbo.MyTable TO MyUser;
GO

-- Grant CONNECT permission to a user
GRANT CONNECT TO MyUser;
GO

Roles can also be used to simplify permission management.

Azure Active Directory (Azure AD) Authentication

Azure AD Authentication offers a more robust and secure approach by integrating with Azure's identity and access management service. This allows you to use centralized identities for access control across various Azure resources.

Overview

Azure AD authentication allows you to authenticate users, groups, and service principals (applications) to Azure SQL Database using their Azure AD credentials. This eliminates the need to manage separate SQL logins and passwords for each database, simplifying administration and enhancing security.

Enabling Azure AD Authentication

To enable Azure AD authentication, you need to configure your Azure SQL Database server to use your Azure AD tenant. This involves setting an Azure AD administrator for the server.

Azure Portal Steps:

Navigate to your Azure SQL Database server in the Azure portal.
Under "Settings", select "Azure Active Directory".
Click "Set admin".
Choose an Azure AD administrator account or group and save the changes.

Connecting with Azure AD

Clients can connect to Azure SQL Database using Azure AD authentication by using tools like Azure Data Studio, SQL Server Management Studio (SSMS), or programmatically via ADAL or MSAL libraries. Authentication can be performed using Azure AD Universal with MFA, Service Principal, or Managed Identity.

Example connection string snippet:


Server=tcp:your_server_name.database.windows.net,1433;Database=your_database_name;Authentication="Active Directory Interactive";

Managing Azure AD Identities

You can create database users for Azure AD users, groups, and service principals. This is done using T-SQL after enabling Azure AD authentication on the server.


USE MyDatabase;
GO

-- Create a user for an Azure AD user
CREATE USER [user@yourdomain.com] FROM EXTERNAL PROVIDER;
GO

-- Create a user for an Azure AD group
CREATE USER [MyAzureADGroup] FROM EXTERNAL PROVIDER;
GO

-- Grant permissions to the Azure AD user
GRANT SELECT ON dbo.MyTable TO [user@yourdomain.com];
GO

Best Practices

Prefer Azure AD Authentication: For enhanced security, centralized management, and support for Multi-Factor Authentication (MFA).
Use Least Privilege: Grant only the necessary permissions to users and applications.
Strong Passwords for SQL Authentication: If using SQL authentication, enforce complex password policies and rotate passwords regularly.
Regularly Audit Access: Monitor login attempts and access patterns to detect suspicious activity.
Use Service Principals or Managed Identities for Applications: Avoid using SQL authentication for applications; leverage Azure AD service principals or managed identities instead.
Limit Public Access: Configure firewall rules to restrict access to your Azure SQL Database to only authorized IP addresses or virtual networks.

Tip

Consider using Azure AD Privileged Identity Management (PIM) to manage just-in-time (JIT) privileged access to your Azure SQL Database.