Setting up Kerberos authentication for Oracle DB instances - Amazon Relational Database Service

Setting up Kerberos authentication for Oracle DB instances

Use AWS Directory Service for Microsoft Active Directory, also called AWS Managed Microsoft AD, to set up Kerberos authentication for an Oracle DB instance. To set up Kerberos authentication, complete the following steps:

Note

During the setup, RDS creates an Oracle database user named managed_service_user@example.com with the CREATE SESSION privilege, where example.com is your domain name. This user corresponds to the user that Directory Service creates inside your Managed Active Directory. Periodically, RDS uses the credentials provided by the Directory Service to log in to your Oracle database. Afterwards, RDS immediately destroys the ticket cache.

Step 1: Create a directory using the 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:

  • Sets up an Active Directory within the VPC.

  • Creates a directory administrator account with the user name Admin and the specified password. You use this account to manage your directory.

    Note

    Be sure to save this password. AWS Directory Service doesn't store it. You can reset it, but you can't retrieve it.

  • Creates a security group for the directory controllers.

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:

  • Create, update, or delete users

  • Add resources to your domain such as file or print servers, and then assign permissions for those resources to users in your OU

  • Create additional OUs and containers

  • Delegate authority

  • Restore deleted objects from the Active Directory Recycle Bin

  • Run AD and DNS Windows PowerShell modules on the Active Directory Web Service

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

  • Manage DNS configurations (add, remove, or update records, zones, and forwarders)

  • View DNS event logs

  • View security event logs

To create the directory, use the AWS Management Console, the AWS CLI, or the AWS Directory Service API. Make sure to open the relevant outbound ports on the directory security group so that the directory can communicate with the Oracle DB instance.

To create a directory with AWS Managed Microsoft AD

  1. Sign in to the AWS Management Console and open the AWS Directory Service console at https://console.aws.amazon.com/directoryservicev2/.

  2. In the navigation pane, choose Directories and choose Set up Directory.

  3. Choose AWS Managed Microsoft AD. AWS Managed Microsoft AD is the only option that you can currently use with Amazon RDS.

  4. Enter the following information:

    Directory DNS name

    The fully qualified name for the directory, such as corp.example.com.

    Directory NetBIOS name

    The short name for the directory, such as CORP.

    Directory description

    (Optional) A description for the directory.

    Admin password

    The password for the directory administrator. The directory creation process creates an administrator account with the user name Admin and this password.

    The directory administrator password and can't include the word "admin." The password is case-sensitive and must be 8–64 characters in length. It must also contain at least one character from three of the following four categories:

    • Lowercase letters (a–z)

    • Uppercase letters (A–Z)

    • Numbers (0–9)

    • Non-alphanumeric characters (~!@#$%^&*_-+=`|\(){}[]:;"'<>,.?/)

    Confirm password

    The administrator password retyped.

  5. Choose Next.

  6. Enter the following information in the Networking section and then choose Next:

    VPC

    The VPC for the directory. Create the Oracle DB instance in this same VPC.

    Subnets

    Subnets for the directory servers. The two subnets must be in different Availability Zones.

  7. Review the directory information and make any necessary changes. When the information is correct, choose Create directory.

    
							Directory details page during creation

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 Oracle DB instance.


					Directory details page

Step 2: Create a trust

If you plan to use AWS Managed Microsoft AD only, move on to Step 3: Create an IAM role for use by Amazon RDS.

To get Kerberos authentication using an on-premises or self-hosted Microsoft Active Directory, create a forest trust or external trust. The trust can be one-way or two-way. For more information about setting up forest trusts using AWS Directory Service, see When to create a trust relationship in the AWS Directory Service Administration Guide.

Step 3: Create an 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.

Note

For the role to allow access, the AWS Security Token Service (AWS STS) endpoint must be activated in the correct AWS Region for your AWS account. AWS STS endpoints are active by default in all AWS Regions, and you can use them without any further actions. For more information, see Activating and deactivating AWS STS in an AWS Region in the IAM User Guide.

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.

Note

The IAM role used for Windows Authentication for RDS for Microsoft SQL Server can't be used for RDS for Oracle.

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 4: Create and configure users

You can create users with the Active Directory Users and Computers tool, which is one of the Active Directory Domain Services and Active Directory Lightweight Directory Services tools. In this case, users are individual people or entities that have access to your directory.

To create users in an AWS Directory Service directory, you must be connected to a Windows-based Amazon EC2 instance that is a member of the AWS Directory Service directory. At the same time, you must be logged in as a user that has privileges to create users. For more information about creating users in your Microsoft Active Directory, see Manage users and groups in AWS Managed Microsoft AD in the AWS Directory Service Administration Guide.

Step 5: Enable cross-VPC traffic between the directory and the DB instance

If you plan to locate the directory and the DB instance in the same VPC, skip this step and move on to Step 6: Create or modify an Oracle DB instance.

If you plan to locate the directory and the DB instance in different AWS accounts or VPCs, configure cross-VPC traffic using VPC peering or AWS Transit Gateway. The following procedure enables traffic between VPCs using VPC peering. Follow the instructions in What is VPC peering? in the Amazon Virtual Private Cloud Peering Guide.

To enable cross-VPC traffic using VPC peering

  1. Set up appropriate VPC routing rules to ensure that network traffic can flow both ways.

  2. Ensure that the DB instance's security group can receive inbound traffic from the directory's security group. For more information, see Best practices for AWS Managed Microsoft AD in the AWS Directory Service Administration Guide.

  3. Ensure that there is no network access control list (ACL) rule to block traffic.

If a different AWS account owns the directory, you must share the directory.

To share the directory between AWS accounts

  1. Start sharing the directory with the AWS account that the DB instance will be created in by following the instructions in Tutorial: Sharing your AWS Managed Microsoft AD directory for seamless EC2 Domain-join in the AWS Directory Service Administration Guide.

  2. Sign in to the AWS Directory Service console using the account for the DB instance, and ensure that the domain has the SHARED status before proceeding.

  3. While signed into the AWS Directory Service console using the account for the DB instance, note the Directory ID value. You use this directory ID to join the DB instance to the domain.

Step 6: Create or modify an Oracle DB instance

Create or modify an Oracle 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 Oracle DB instances in a VPC. The DB instance can be in the same VPC as the directory, or in a different VPC. When you create or modify the DB instance, do the following:

  • Provide the domain identifier (d-* identifier) that was generated when you created your directory.

  • Provide the name of the IAM role that you created.

  • Ensure that the DB instance security group can receive inbound traffic from the directory security group and send outbound traffic to the directory.

When you use the console to create 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.


					Kerberos authentication setting when creating a DB instance

When you use the console to modify or restore a DB instance, choose the directory in the Kerberos authentication section, or choose Create a new directory.


					Kerberos authentication setting when modifying or restoring a DB instance

When you use the AWS CLI, the following parameters are required for the DB instance to be able to use the directory that you created:

  • For the --domain parameter, use the domain identifier ("d-*" identifier) generated when you created the directory.

  • For the --domain-iam-role-name parameter, use the role you created that uses the managed IAM policy AmazonRDSDirectoryServiceAccess.

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
Important

If you modify a DB instance to enable Kerberos authentication, reboot the DB instance after making the change.

Note

MANAGED_SERVICE_USER is a service account whose name is randomly generated by Directory Service for RDS. During the Kerberos authentication setup, RDS for Oracle creates a user with the same name and assigns it the CREATE SESSION privilege. The Oracle DB user is identified externally as MANAGED_SERVICE_USER@EXAMPLE.COM, where EXAMPLE.COM is the name of your domain. Periodically, RDS uses the credentials provided by the Directory Service to log in to your Oracle database. Afterward, RDS immediately destroys the ticket cache.

Step 7: Create Kerberos authentication Oracle logins

Use the Amazon RDS master user credentials to connect to the Oracle 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 Oracle logins and users from the Microsoft Active Directory users and groups in your domain. To manage database permissions, you grant and revoke standard Oracle permissions to these logins.

To allow a Microsoft Active Directory user to authenticate with Oracle

  1. Connect to the Oracle DB instance using your Amazon RDS master user credentials.

  2. Create an externally authenticated user in Oracle database.

    In the following example, replace KRBUSER@CORP.EXAMPLE.COM with the user name and domain name.

    CREATE USER "KRBUSER@CORP.EXAMPLE.COM" IDENTIFIED EXTERNALLY; GRANT CREATE SESSION TO "KRBUSER@CORP.EXAMPLE.COM";

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

Step 8: Configure an Oracle client

To configure an Oracle client, meet the following requirements:

  • Create a configuration file named krb5.conf (Linux) or krb5.ini (Windows) to point to the domain. Configure the Oracle client to use this configuration file.

  • Verify that traffic can flow between the client host and AWS Directory Service over DNS port 53 and Kerberos ports (88 and 464 for managed AWS Directory Service) over TCP/UDP.

  • Verify that traffic can flow between the client host and the DB instance over the database port.

Following is sample content for AWS Managed Microsoft AD.

[libdefaults] default_realm = EXAMPLE.COM [realms] EXAMPLE.COM = { kdc = example.com admin_server = example.com } [domain_realm] .example.com = EXAMPLE.COM example.com = EXAMPLE.COM

Following is sample content for on-premise Microsoft AD. In your krb5.conf or krb5.ini file, replace on-prem-ad-server-name with the name of your on-premises AD server.

[libdefaults] default_realm = ONPREM.COM [realms] AWSAD.COM = { kdc = awsad.com admin_server = awsad.com } ONPREM.COM = { kdc = on-prem-ad-server-name admin_server = on-prem-ad-server-name } [domain_realm] .awsad.com = AWSAD.COM awsad.com= AWSAD.COM .onprem.com = ONPREM.COM onprem.com= ONPREM.COM
Note

After you configure your krb5.ini or krb5.conf file, we recommend that you reboot the server.

The following is sample sqlnet.ora content for a SQL*Plus configuration:

SQLNET.AUTHENTICATION_SERVICES=(KERBEROS5PRE,KERBEROS5) SQLNET.KERBEROS5_CONF=path_to_krb5.conf_file

For an example of a SQL Developer configuration, see Document 1609359.1 from Oracle Support.