Best practices for AWS Control Tower administrators - AWS Control Tower

Best practices for AWS Control Tower administrators

This topic is intended primarily for management account administrators.

Management account administrators are responsible for explaining some tasks that AWS Control Tower guardrails prevent their member account administrators from doing. This topic describes some best practices and procedures for transferring this knowledge, and it gives other tips for setting up and maintaining your AWS Control Tower environment efficiently.

Explaining Access to Users

The AWS Control Tower console is available only to users with the management account administrator permissions. Only these users can perform administrative work within your landing zone. In accordance with best practices, this means that the majority of your users and member account administrators will never see the AWS Control Tower console. As a member of the management account administrator group, it's your responsibility to explain the following information to the users and administrators of your member accounts, as appropriate.

  • Explain which AWS resources that users and administrators have access to within the landing zone.

  • List the preventive guardrails that apply to each Organizational Unit (OU) so that the other administrators can plan and execute their AWS workloads accordingly.

Explaining Resource Access

Some administrators and other users may need an explanation of the AWS resources to which they have access to within your landing zone. This access can include programmatic access and console-based access. Generally speaking, read access and write access for AWS resources is allowed. To perform work within AWS, your users require some level of access to the specific services they need to do their jobs.

Some users, such as your AWS developers, may need to know about the resources to which they have access, so they can create engineering solutions. Other users, such as the end users of the applications that run on AWS services, do not need to know about AWS resources within your landing zone.

AWS offers tools to identify the scope of a user's AWS resource access. After you identify the scope of a user's access, you can share that information with the user, in accordance with your organization's information management policies. For more information about these tools, see the links that follow.

  • AWS access advisor – The AWS Identity and Access Management (IAM) access advisor tool lets you determine the permissions that your developers have by analyzing the last timestamp when an IAM entity, such as a user, role, or group, called an AWS service. You can audit service access and remove unnecessary permissions, and you can automate the process if needed. For more information, see our AWS Security blog post.

  • IAM policy simulator – With the IAM policy simulator, you can test and troubleshoot IAM-based and resource-based policies. For more information, see Testing IAM Policies with the IAM Policy Simulator.

  • AWS CloudTrail logs – You can review AWS CloudTrail logs to see actions taken by a user, role, or AWS service. For more information about CloudTrail, see the AWS CloudTrail User Guide.

    Actions taken by CloudTrail landing zone administrators are logged in the landing zone management account. Actions taken by member account administrators and users are logged in the shared log archive account.

    You can view a summary table of AWS Control Tower events in the Activities page.

Explaining Preventive Guardrails

A preventive guardrail ensures that your organization's accounts maintain compliance with your corporate policies. The status of a preventive guardrail is either enforced or not-enabled. A preventive guardrail prevents policy violations by using service control policies (SCPs). In comparison, a detective guardrail informs you of various events or states that exist, by means of defined AWS Config rules.

Some of your users, such as AWS developers, may need to know about the preventive guardrails that apply to any accounts and OUs they use, so they can create engineering solutions. The following procedure offers some guidance on how to provide this information for the right users, according to your organization's information management policies.

Note

This procedure assumes you've already created at least one child OU within your landing zone, as well as at least one AWS Single Sign-On user.

To show preventive guardrails for users with a need to know

  1. Sign in to the AWS Control Tower console at https://console.aws.amazon.com/controltower/.

  2. From the left navigation, choose Organizational units.

  3. From the table, choose the name of one of the OUs for which your user needs information about the applicable guardrails.

  4. Note the name of the OU and the guardrails that apply to this OU.

  5. Repeat the previous two steps for each OU about which your user needs information.

For detailed information about the guardrails and their functions, see Guardrails in AWS Control Tower.

AWS Organizations Guidance

  • You can find guidance about best practices to protect the security of your AWS Control Tower management account and member accounts in the AWS Organizations documentation.

  • Do not use AWS Organizations to update service control policies (SCPs) attached to an OU that is registered with AWS Control Tower. Doing so could result in the guardrails entering an unknown state, which will require you to repair your landing zone or re-register your OU in AWS Control Tower. Instead, you can create new SCPs and attach those to the OUs rather than editing the SCPs that AWS Control Tower has created.

  • Moving individual, already enrolled, accounts into AWS Control Tower, from outside of a registered OU, causes drift that must be repaired. See Types of Governance Drift.

  • If you use AWS Organizations to create, invite, or move accounts within an organization registered with AWS Control Tower, those accounts are not enrolled by AWS Control Tower and those changes are not recorded. If you need access to these accounts through SSO, see Member Account Access.

  • If you use AWS Organizations to move an OU into an organization created by AWS Control Tower, the external OU is not registered by AWS Control Tower.

  • AWS Control Tower handles permission filtering differently than AWS Organizations does. If your accounts are provisioned with AWS Control Tower account factory, end users can see the names and parents of all OUs in the AWS Control Tower console, even if they don't have permission to retrieve those names and parents from AWS Organizations directly.

  • AWS Control Tower does not support mixed permissions on organizations, such as permission to view an OU's parent but not to view OU names. For this reason, AWS Control Tower administrators are expected to have full permissions.

AWS Single Sign-On Guidance

  • For specific information about how AWS Control Tower works with SSO based on your identity source, see Considerations for AWS Single Sign-On (SSO) customers in the Prerequisites section of the Getting Started page of this User Guide.

  • For additional information about how the behavior of AWS Control Tower interacts with AWS SSO and different identity sources, refer to Considerations for Changing Your Identity Source in the AWS SSO documentation.

  • See Managing Users and Access Through AWS Single Sign-On for more information about working with AWS Control Tower and AWS SSO.

Account Factory Guidance

  • When you use Account Factory to provision new accounts in AWS Control Tower, do not define TagOptions, enable notifications, or create a provisioned product plan. Doing so can result in a failure to provision a new account.

  • If you are authenticated as an IAM user when you provision accounts in Account Factory or when you use the Enroll account feature, be sure the IAM user is added to the AWS Service Catalog portfolio so that it has the correct permissions. Otherwise, you may receive an error message from AWS Service Catalog that is difficult to understand. Common causes for this type of error are given in the Troubleshooting guide. In particular, refer to the section entitled No Launch Paths Found Error.

  • Remember that only one account can be provisioned at a time.

Guidance on Subscribing to SNS Topics

  • The aws-controltower-AllConfigNotifications SNS topic receives all events published by AWS Config, including compliance notifications and AWS CloudWatch event notifications. For example, this topic informs you if a guardrail violation has occurred. It also gives information about other types of events. (Learn more from AWS Config about what they publish when this topic is configured.)

  • Data Events from the aws-controltower-BaselineCloudTrail trail are set to publish to the aws-controltower-AllConfigNotifications SNS topic as well.

  • To receive detailed compliance notifications, we recommend that you subscribe to the aws-controltower-AllConfigNotifications SNS topic. This topic aggregates compliance notifications from all child accounts.

  • To receive drift notifications and other notifications as well as compliance notifications, but fewer notifications overall, we recommend that you subscribe to the aws-controltower-AggregateSecurityNotifications SNS topic.

For more information about SNS topics and compliance, see Drift prevention and notification.

Guidance for KMS keys

AWS Control Tower works with AWS Key Management Service (KMS). Optionally, if you wish to encrypt and decrypt your AWS Control Tower resources with an encryption key that you manage, you can generate and configure AWS KMS keys. You can add or change a KMS key any time you update your landing zone. As a best practice, we recommend using your own KMS keys and changing them from time to time.

The AWS Key Management Service (KMS) allows you to create multi-Region KMS keys and asymmetric keys; however, AWS Control Tower does not support multi-Region keys or asymmetric keys. AWS Control Tower performs a pre-check of your existing keys. You may see an error message if you select a multi-Region key or an asymmetric key. In that case, generate another key for use with AWS Control Tower resources.

For customers who operate an AWS CloudHSM cluster: Create a custom key store associated with your CloudHSM cluster. Then you can create a KMS key, which resides in the CloudHSM custom key store you created. You can add this KMS key to AWS Control Tower.

You must make a specific update to the permissions policy of a KMS key to make it work with AWS Control Tower. For details, refer to the section called To make the key's policy update.