createSession

Creates a session that establishes temporary security credentials to support fast authentication and authorization for the Zonal endpoint APIs on directory buckets. For more information about Zonal endpoint APIs that include the Availability Zone in the request endpoint, see S3 Express One Zone APIs in the Amazon S3 User Guide.

To make Zonal endpoint API requests on a directory bucket, use the CreateSession API operation. Specifically, you grant s3express:CreateSession permission to a bucket in a bucket policy or an IAM identity-based policy. Then, you use IAM credentials to make the CreateSession API request on the bucket, which returns temporary security credentials that include the access key ID, secret access key, session token, and expiration. These credentials have associated permissions to access the Zonal endpoint APIs. After the session is created, you don’t need to use other policies to grant permissions to each Zonal endpoint API individually. Instead, in your Zonal endpoint API requests, you sign your requests by applying the temporary security credentials of the session to the request headers and following the SigV4 protocol for authentication. You also apply the session token to the x-amz-s3session-token request header for authorization. Temporary security credentials are scoped to the bucket and expire after 5 minutes. After the expiration time, any calls that you make with those credentials will fail. You must use IAM credentials again to make a CreateSession API request that generates a new set of temporary credentials for use. Temporary credentials cannot be extended or refreshed beyond the original specified interval.

If you use Amazon Web Services SDKs, SDKs handle the session token refreshes automatically to avoid service interruptions when a session expires. We recommend that you use the Amazon Web Services SDKs to initiate and manage requests to the CreateSession API. For more information, see Performance guidelines and design patterns in the Amazon S3 User Guide.

• You must make requests for this API operation to the Zonal endpoint. These endpoints support virtual-hosted-style requests in the format https://<i>bucket_name</i>.s3express-<i>az_id</i>.<i>region</i>.amazonaws.com. Path-style requests are not supported. For more information, see Regional and Zonal endpoints in the Amazon S3 User Guide.

• CopyObject API operation - Unlike other Zonal endpoint APIs, the CopyObject API operation doesn't use the temporary security credentials returned from the CreateSession API operation for authentication and authorization. For information about authentication and authorization of the CopyObject API operation on directory buckets, see CopyObject.

• HeadBucket API operation - Unlike other Zonal endpoint APIs, the HeadBucket API operation doesn't use the temporary security credentials returned from the CreateSession API operation for authentication and authorization. For information about authentication and authorization of the HeadBucket API operation on directory buckets, see HeadBucket.

Permissions

To obtain temporary security credentials, you must create a bucket policy or an IAM identity-based policy that grants s3express:CreateSession permission to the bucket. In a policy, you can have the s3express:SessionMode condition key to control who can create a ReadWrite or ReadOnly session. For more information about ReadWrite or ReadOnly sessions, see x-amz-create-session-mode. For example policies, see Example bucket policies for S3 Express One Zone and Amazon Web Services Identity and Access Management (IAM) identity-based policies for S3 Express One Zone in the Amazon S3 User Guide.

To grant cross-account access to Zonal endpoint APIs, the bucket policy should also grant both accounts the s3express:CreateSession permission.

HTTP Host header syntax

**Directory buckets ** - The HTTP Host header syntax is <i>Bucket_name</i>.s3express-<i>az_id</i>.<i>region</i>.amazonaws.com.