Manage AWS STS in an AWS Region

A Regional endpoint is the URL of the entry point within a particular region for an AWS web service. AWS recommends using Regional AWS Security Token Service (AWS STS) endpoints instead of the global endpoint to reduce latency, build in redundancy, and increase session token validity. Although the global (legacy) AWS STS endpoint https://sts.amazonaws.com is highly available, it’s hosted in a single AWS Region, US East (N. Virginia), and like other endpoints, it doesn’t provide automatic failover to endpoints in other Regions.

• Reduce latency – By making your AWS STS calls to an endpoint that is geographically closer to your services and applications, you can access AWS STS services with lower latency and better response times.

• Build in redundancy – You can limit the effects of a failure within a workload to a limited number of components with a predictable scope of impact containment. Using regional AWS STS endpoints lets you align the scope of your components with the scope of your session tokens. For more information about this reliability pillar, see Use fault isolation to protect your workload in the AWS Well-Architected Framework.

• Increase session token validity – Session tokens from Regional AWS STS endpoints are valid in all AWS Regions. Session tokens from the global STS endpoint are valid only in AWS Regions that are enabled by default. If you intend to enable a new Region for your account, you can use session tokens from Regional AWS STS endpoints. If you choose to use the global endpoint, you must change the Region compatibility of AWS STS session tokens for the global endpoint. Doing so ensures that tokens are valid in all AWS Regions.

For a list of AWS STS Regions and their endpoints, see AWS STS Regions and endpoints.

Activating and deactivating AWS STS in an AWS Region

When you activate STS endpoints for a Region, AWS STS can issue temporary credentials to users and roles in your account that make an AWS STS request. Those credentials can then be used in any Region that is enabled by default or is manually enabled. For Regions that are enabled by default, you must activate the Regional STS endpoint in the account where the temporary credentials are generated. It does not matter whether a user is signed into the same account or a different account when they make the request. For Regions that are manually enabled, you must activate the Region in both the account making the request and the account where the temporary credentials are generated.

For example, imagine a user in account A wants to send an sts:AssumeRole API request to the AWS STS Regional endpoint https://sts.us-west-2.amazonaws.com. The request is for temporary credentials for the role named Developer in account B. Because the request is to create credentials for an entity in account B, account B must activate the us-west-2 Region. Users from account A (or any other account) can call the us-west-2 AWS STS endpoint to request credentials for account B whether or not the Region is activated in their accounts.

Note

Active Regions are available to everyone that uses temporary credentials in that account. To control which IAM users or roles can access the Region, use the aws:RequestedRegion condition key in your permissions policies.

To activate or deactivate AWS STS in a Region that is enabled by default (console)

1. Sign in as a root user or a user with permissions to perform IAM administration tasks.

2. Open the IAM console and in the navigation pane choose Account settings.

3. In the Security Token Service (STS) section Endpoints, find the Region that you want to configure, and then choose Active or Inactive in the STS status column.

4. In the dialog box that opens, choose Activate or Deactivate.

For Regions that must be enabled, we activate AWS STS automatically when you enable the Region. After you enable a Region, AWS STS is always active for the Region and you cannot deactivate it. To learn about enabling Regions that are disabled by default, see Specifying which AWS Regions your account can use in the AWS Account Management Reference Guide.

Writing code to use AWS STS Regions

After you activate a Region, you can direct AWS STS API calls to that Region. The following Java code snippet demonstrates how to configure an AWSSecurityTokenService object to make requests to the Europe (Milan) (eu-south-1) Region.

EndpointConfiguration regionEndpointConfig = new EndpointConfiguration("https://sts.eu-south-1.amazonaws.com", "eu-south-1");
AWSSecurityTokenService stsRegionalClient = AWSSecurityTokenServiceClientBuilder.standard()
.withCredentials(credentials)
.withEndpointConfiguration(regionEndpointConfig)
.build();

AWS STS recommends that you make calls to a Regional endpoint. To learn how to manually enable a Region, see Specify which AWS Regions your account can use in the AWS Account Management Reference Guide.

In the example, the first line instantiates an EndpointConfiguration object called regionEndpointConfig, passing the URL of the endpoint and the AWS Region as the parameters.

To learn how to set AWS STS regional endpoints using an environment variable for AWS SDKs, see AWS STS Regionalized endpoints in the AWS SDKs and Tools Reference Guide.

For all other language and programming environment combinations, refer to the documentation for the relevant SDK.

Managing global endpoint session tokens

Most AWS Regions are enabled for operations in all AWS services by default. Those Regions are automatically activated for use with AWS STS. Some Regions, such as Asia Pacific (Hong Kong), must be manually enabled. To learn more about enabling and disabling AWS Regions, see Specify which AWS Regions your account can use in the AWS Account Management Reference Guide. When you enable these AWS Regions, they are automatically activated for use with AWS STS. You cannot activate the AWS STS endpoint for a Region that is disabled. Session tokens that are valid in all AWS Regions include more characters than tokens that are valid in Regions that are enabled by default. Changing this setting might affect existing systems where you temporarily store tokens.

You can change this setting using the AWS Management Console, AWS CLI, or AWS API.

To change the Region compatibility of session tokens for the global endpoint (console)

1. Sign in as a root user or a user with permissions to perform IAM administration tasks. To change the compatibility of session tokens, you must have a policy that allows the iam:SetSecurityTokenServicePreferences action.

2. Open the IAM console. In the navigation pane, choose Account settings.

3. Under Security Token Service (STS) section Session Tokens from the STS endpoints. The Global endpoint indicates Valid only in AWS Regions enabled by default. Choose Change.

4. In the Change region compatibility dialog box, select All AWS Regions. Then choose Save changes.

   Note

   Session tokens that are valid in all AWS Region include more characters than tokens that are valid in Regions that are enabled by default. Changing this setting might affect existing systems where you temporarily store tokens.

To change the Region compatibility of session tokens for the global endpoint (AWS CLI)

Set the session token version. Version 1 tokens are valid only in AWS Regions that are available by default. These tokens do not work in manually enabled Regions, such as Asia Pacific (Hong Kong). Version 2 tokens are valid in all Regions. However, version 2 tokens include more characters and might affect systems where you temporarily store tokens.

• aws iam set-security-token-service-preferences

To change the Region compatibility of session tokens for the global endpoint (AWS API)

Set the session token version. Version 1 tokens are valid only in AWS Regions that are available by default. These tokens do not work in manually enabled Regions, such as Asia Pacific (Hong Kong). Version 2 tokens are valid in all Regions. However, version 2 tokens include more characters and might affect systems where you temporarily store tokens.

• SetSecurityTokenServicePreferences