Update on April 9, 2019: We added some text to clarify that the session token size is going to increase.

The AWS Cloud spans 61 Availability Zones within 20 geographic regions around the world, and has announced plans to expand to 12 more Availability Zones and four more Regions: Hong Kong, Bahrain, Cape Town, and Milan. Customers have told us that they want an easier way to control the Regions where their AWS accounts operate. Based on this feedback, AWS is changing the default behavior for these four and all future Regions so customers will opt in the accounts they want to operate in each new Region. For new AWS Regions, Identity and Access Management (IAM) resources such as users and roles will only be propagated to the Regions that you enable. When the next Region launches, you can enable this Region for your account using the AWS Regions setting under My Account in the AWS Management Console. You will need to enable a new Region for your account before you can create and manage resources in that Region. At this time, there are no changes to existing AWS Regions.

We recommend that you review who in your account will have access to enable and disable AWS Regions. Additionally, you can prepare for this change by setting permissions so that only approved account administrators can enable and disable AWS Regions. Starting today, you can use IAM permissions policies to control which IAM principals (users and roles) can perform these actions.

In this post, I describe the new account permissions for enabling and disabling new AWS Regions. I also describe the updates we’ve made to deny these permissions in the AWS-managed PowerUserAccess policy that many customers use to restrict access to administrative actions. For customers who use custom policies to manage administrative access, I show how to secure access to enable and disable new AWS Regions using IAM permissions policies and Service Control Policies in AWS Organizations. Finally, I explain the compatibility of Security Token Service (STS) session tokens with Regions.

IAM Permissions to enable and disable new AWS Regions for your account

To control access to enable and disable new AWS Regions for your account, you can set IAM permissions using two new account actions. By default, IAM denies access to new actions unless you have explicitly allowed these permissions in an existing policy. You can use IAM permissions policies to allow or deny the actions to enable and disable AWS Regions to IAM principals in your account. The new actions are:

Action Description account:EnableRegion Allows you to opt in an account to a new AWS Region (for Regions launched after March 20, 2019). This action propagates your IAM resources such as users and roles to the Region. account:DisableRegion Allows you to opt out an account from a new AWS Region (for Regions launched after March 20, 2019). This action removes your IAM resources such as users and roles from the Region.

When granting permissions using IAM policies, some administrators may have granted full access to AWS services except for administrative services such as IAM and Organizations. These IAM principals will automatically get access to the new administrative actions in your account to enable and disable AWS Regions. If you prefer not to provide account permissions to enable or disable AWS Regions to these principals, we recommend that you add a statement to your policies to deny access to account permissions. To do this, you can add a deny statement for account:*. As new Regions launch, you will be able to specify the Regions where these permissions are granted or denied.

At this time, the account actions to enable and disable AWS Regions apply to all upcoming AWS Regions launched after March 20, 2019. To learn more about managing access to existing AWS Regions, review my post, Easier way to control access to AWS regions using IAM policies.

Updates to AWS managed PowerUserAccess Policy

If you’re using the AWS managed PowerUserAccess policy to grant permissions to AWS services without granting access to administrative actions for IAM and Organizations, we have updated this policy as shown below to exclude access to account actions to enable and disable new AWS Regions. You do not need to take further action to restrict these actions for any IAM principals for which this policy applies. We updated the first policy statement, which now allows access to all existing and future AWS service actions except for IAM, AWS Organizations, and account. We also updated the second policy statement to allow the read-only action for listing Regions. The rest of the policy remains unchanged.

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "NotAction": [ "iam:*", "organizations:*", "account:*" ], "Resource": "*" }, { "Effect": "Allow", "Action": [ "iam:CreateServiceLinkedRole", "iam:DeleteServiceLinkedRole", "iam:ListRoles", "organizations:DescribeOrganization", "account:ListRegions" ], "Resource": "*" } ] }

Restrict Region permissions across multiple accounts using Service Control Policies in AWS Organizations

You can also centrally restrict access to enable and disable Regions for all principals across all accounts in AWS Organizations using Service Control Policies (SCPs). You would use SCPs to restrict this access if you do not anticipate using new Regions. SCPs enable administrators to set permission guardrails that apply to accounts in your organization or an organization unit. To learn more about SCPs and how to create and attach them, read About Service Control Policies.

Next, I show how to restrict the Region enable and disable actions for accounts in an AWS organization using an SCP. In the policy below, I explicitly deny using the Effect block of the policy statement. In the Action block, you add the new permissions account:EnableRegion and account:DisableRegion.

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Deny", "Action": [ "account:EnableRegion", "account:DisableRegion" ], "Resource": "*" } ] }

Once you create the policy, you can attach this policy to the root of your organization. This will restrict permissions across all accounts in your organization.

Check if users have permissions to enable or disable new AWS Regions in my account

You can use the IAM Policy Simulator to check if any IAM principal in your account has access to the new account actions for enabling and disabling Regions. The simulator evaluates the policies that you choose for a user or role and determines the effective permissions for each of the actions that you specify. Learn more about using the IAM Policy Simulator.

Region compatibility of AWS STS session tokens

For new AWS Regions, we’re also changing region compatibility for session tokens from the AWS Security Token Service (STS) global endpoint. As a best practice, we recommend using the regional STS endpoints to reduce latency. If you’re using regional STS endpoints or don’t plan to operate in new AWS Regions, then the following change doesn’t apply to you and no action is required.

If you’re using the global STS endpoint (https://sts.amazonaws.com) for session tokens and plan to operate in new AWS Regions, the session token size is going to increase such that it will be of the same size as the session token issued by regional STS endpoints. This may impact functionality if you store session tokens in any of your systems. To ensure your systems work with this change, we recommend that you update your existing systems to use regional STS endpoints using the AWS SDK.

Summary

AWS is changing the default behavior for all new Regions going forward. For new AWS Regions, you will opt in to enable your account to operate in those Regions. This makes it easier for you to select the regions where you can create and manage AWS resources. To prepare for upcoming Region launches, we recommend that you validate the capability to enable and disable AWS Regions to ensure only approved IAM principals can enable and disable AWS Regions for your account.

If you have comments about this post, submit them in the Comments section below. If you have questions about or suggestions for this solution, start a new thread on the AWS forums.

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