Using Kerberos authentication for Amazon RDS for MySQL

You can use Kerberos authentication to authenticate users when they connect to your MySQL DB instance. The DB instance works with AWS Directory Service for Microsoft Active Directory (AWS Managed Microsoft AD) to enable Kerberos authentication. When users authenticate with a MySQL DB instance joined to the trusting domain, authentication requests are forwarded. Forwarded requests go to the domain directory that you create with AWS Directory Service.

Keeping all of your credentials in the same directory can save you time and effort. With this approach, you have a centralized place for storing and managing credentials for multiple DB instances. Using a directory can also improve your overall security profile.

Region and version availability

Feature availability and support varies across specific versions of each database engine, and across AWS Regions. For more information on version and Region availability of Amazon RDS with Kerberos authentication, see Supported Regions and DB engines for Kerberos authentication in Amazon RDS.

Overview of Setting up Kerberos authentication for MySQL DB instances

To set up Kerberos authentication for a MySQL DB instance, complete the following general steps, described in more detail later:

Setting up Kerberos authentication for MySQL DB instances

You use AWS Managed Microsoft AD to set up Kerberos authentication for a MySQL DB instance. To set up Kerberos authentication, you take the following steps.

Step 1: Create a directory using AWS Managed Microsoft AD

AWS Directory Service creates a fully managed Active Directory in the AWS Cloud. When you create an AWS Managed Microsoft AD directory, AWS Directory Service creates two domain controllers and Domain Name System (DNS) servers on your behalf. The directory servers are created in different subnets in a VPC. This redundancy helps make sure that your directory remains accessible even if a failure occurs.

When you create an AWS Managed Microsoft AD directory, AWS Directory Service performs the following tasks on your behalf:

When you launch an AWS Managed Microsoft AD, AWS creates an Organizational Unit (OU) that contains all of your directory's objects. This OU has the NetBIOS name that you typed when you created your directory and is located in the domain root. The domain root is owned and managed by AWS.

The Admin account that was created with your AWS Managed Microsoft AD directory has permissions for the most common administrative activities for your OU:

The Admin account also has rights to perform the following domain-wide activities:

It takes several minutes for the directory to be created. When it has been successfully created, the Status value changes to Active.

To see information about your directory, choose the directory name in the directory listing. Note the Directory ID value because you need this value when you create or modify your MySQL DB instance.

Step 2: Create the IAM role for use by Amazon RDS

For Amazon RDS to call AWS Directory Service for you, an IAM role that uses the managed IAM policy AmazonRDSDirectoryServiceAccess is required. This role allows Amazon RDS to make calls to the AWS Directory Service.

When a DB instance is created using the AWS Management Console and the console user has the iam:CreateRole permission, the console creates this role automatically. In this case, the role name is rds-directoryservice-kerberos-access-role. Otherwise, you must create the IAM role manually. When you create this IAM role, choose Directory Service, and attach the AWS managed policy AmazonRDSDirectoryServiceAccess to it.

For more information about creating IAM roles for a service, see Creating a role to delegate permissions to an AWS service in the IAM User Guide.

Optionally, you can create policies with the required permissions instead of using the managed IAM policy AmazonRDSDirectoryServiceAccess. In this case, the IAM role must have the following IAM trust policy.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "Service": [
          "directoryservice.rds.amazonaws.com",
          "rds.amazonaws.com"
        ]
      },
      "Action": "sts:AssumeRole"
    }
  ]
}		       

The role must also have the following IAM role policy.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": [
        "ds:DescribeDirectories",
        "ds:AuthorizeApplication",
        "ds:UnauthorizeApplication",
        "ds:GetAuthorizedApplicationDetails"
      ],
    "Effect": "Allow",
    "Resource": "*"
    }
  ]
}		

Step 3: Create and configure users

You can create users with the Active Directory Users and Computers tool. This tool is part of the Active Directory Domain Services and Active Directory Lightweight Directory Services tools. Users represent individual people or entities that have access to your directory.

To create users in an AWS Directory Service directory, you must be connected to an Amazon EC2 instance based on Microsoft Windows. This instance must be a member of the AWS Directory Service directory and be logged in as a user that has privileges to create users. For more information, see Manage users and groups in AWS Managed Microsoft AD in the AWS Directory Service Administration Guide.

Step 4: Create or modify a MySQL DB instance

Create or modify a MySQL DB instance for use with your directory. You can use the console, CLI, or RDS API to associate a DB instance with a directory. You can do this in one of the following ways:

Kerberos authentication is only supported for MySQL DB instances in a VPC. The DB instance can be in the same VPC as the directory, or in a different VPC. The DB instance must use a security group that allows egress within the directory's VPC so the DB instance can communicate with the directory.

When you use the console to create, modify, or restore a DB instance, choose Password and Kerberos authentication in the Database authentication section. Choose Browse Directory and then select the directory, or choose Create a new directory.

When you use the AWS CLI or RDS API, associate a DB instance with a directory. The following parameters are required for the DB instance to use the domain directory you created:

For example, the following CLI command modifies a DB instance to use a directory.

For Linux, macOS, or Unix:

aws rds modify-db-instance \
    --db-instance-identifier mydbinstance \
    --domain d-ID \
    --domain-iam-role-name role-name
            

For Windows:

aws rds modify-db-instance ^
    --db-instance-identifier mydbinstance ^
    --domain d-ID ^
    --domain-iam-role-name role-name 
            

Step 5: Create Kerberos authentication MySQL logins

Use the Amazon RDS master user credentials to connect to the MySQL DB instance as you do any other DB instance. The DB instance is joined to the AWS Managed Microsoft AD domain. Thus, you can provision MySQL logins and users from the Active Directory users in your domain. Database permissions are managed through standard MySQL permissions that are granted to and revoked from these logins.

You can allow an Active Directory user to authenticate with MySQL. To do this, first use the Amazon RDS master user credentials to connect to the MySQL DB instance as with any other DB instance. After you're logged in, create an externally authenticated user with PAM (Pluggable Authentication Modules) in MySQL by running the following command. Replace testuser with the user name.

CREATE USER 'testuser'@'%' IDENTIFIED WITH 'auth_pam';

Users (both humans and applications) from your domain can now connect to the DB instance from a domain joined client machine using Kerberos authentication.

ALTER USER 'testuser'@'%' REQUIRE SSL;

Managing a DB instance in a domain

You can use the CLI or the RDS API to manage your DB instance and its relationship with your managed Active Directory. For example, you can associate an Active Directory for Kerberos authentication and disassociate an Active Directory to disable Kerberos authentication. You can also move a DB instance to be externally authenticated by one Active Directory to another.

For example, using the Amazon RDS API, you can do the following:

Understanding domain membership

After you create or modify your DB instance, it becomes a member of the domain. You can view the status of the domain membership for the DB instance by running the describe-db-instances CLI command. The status of the DB instance can be one of the following:

A request to enable Kerberos authentication can fail because of a network connectivity issue or an incorrect IAM role. For example, suppose that you create a DB instance or modify an existing DB instance and the attempt to enable Kerberos authentication fails. If this happens, re-issue the modify command or modify the newly created DB instance to join the domain.

Connecting to MySQL with Kerberos authentication

To connect to MySQL with Kerberos authentication, you must log in using the Kerberos authentication type.

To create a database user that you can connect to using Kerberos authentication, use an IDENTIFIED WITH clause on the CREATE USER statement. For instructions, see Step 5: Create Kerberos authentication MySQL logins.

To avoid errors, use the MariaDB mysql client. You can download MariaDB software at https://downloads.mariadb.org/.

At a command prompt, connect to one of the endpoints associated with your MySQL DB instance. Follow the general procedures in Connecting to a DB instance running the MySQL database engine. When you're prompted for the password, enter the Kerberos password associated with that user name.

Restoring a MySQL DB instance and adding it to a domain

You can restore a DB snapshot or complete a point-in-time restore for a MySQL DB instance and then add it to a domain. After the DB instance is restored, modify the DB instance using the process explained in Step 4: Create or modify a MySQL DB instance to add the DB instance to a domain.

Kerberos authentication MySQL limitations

The following limitations apply to Kerberos authentication for MySQL: