CreateSession
Creates a session that establishes temporary security credentials to support fast authentication and authorization for the Zonal endpoint API operations on directory buckets. For more information about Zonal endpoint API operations 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 API operations. 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 SDKs, SDKs handle the session token refreshes automatically to avoid service interruptions when a session expires. We recommend that you use the Amazon 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.
Note
-
You must make requests for this API operation to the Zonal endpoint. These endpoints support virtual-hosted-style requests in the format
https://bucket_name.s3express-az_id.region.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 API operations, theCopyObject
API operation doesn't use the temporary security credentials returned from theCreateSession
API operation for authentication and authorization. For information about authentication and authorization of theCopyObject
API operation on directory buckets, see CopyObject. -
HeadBucket
API operation - Unlike other Zonal endpoint API operations, theHeadBucket
API operation doesn't use the temporary security credentials returned from theCreateSession
API operation for authentication and authorization. For information about authentication and authorization of theHeadBucket
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 thes3express:SessionMode
condition key to control who can create aReadWrite
orReadOnly
session. For more information aboutReadWrite
orReadOnly
sessions, seex-amz-create-session-mode
. For example policies, see Example bucket policies for S3 Express One Zone and Amazon 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 API operations, the bucket policy should also grant both accounts the
s3express:CreateSession
permission.If you want to encrypt objects with SSE-KMS, you must also have the
kms:GenerateDataKey
and thekms:Decrypt
permissions in IAM identity-based policies and Amazon KMS key policies for the target Amazon KMS key. - Encryption
-
For directory buckets, there are only two supported options for server-side encryption: server-side encryption with Amazon S3 managed keys (SSE-S3) (
AES256
) and server-side encryption with Amazon KMS keys (SSE-KMS) (aws:kms
). We recommend that the bucket's default encryption uses the desired encryption configuration and you don't override the bucket default encryption in yourCreateSession
requests orPUT
object requests. Then, new objects are automatically encrypted with the desired encryption settings. For more information, see Protecting data with server-side encryption in the Amazon S3 User Guide. For more information about the encryption overriding behaviors in directory buckets, see Specifying server-side encryption with Amazon KMS for new object uploads.For Zonal endpoint (object-level) API operations except CopyObject and UploadPartCopy, you authenticate and authorize requests through CreateSession for low latency. To encrypt new objects in a directory bucket with SSE-KMS, you must specify SSE-KMS as the directory bucket's default encryption configuration with a KMS key (specifically, a customer managed key). Then, when a session is created for Zonal endpoint API operations, new objects are automatically encrypted and decrypted with SSE-KMS and S3 Bucket Keys during the session.
Note
Only 1 customer managed key is supported per directory bucket for the lifetime of the bucket. The Amazon managed key (
aws/s3
) isn't supported. After you specify SSE-KMS as your bucket's default encryption configuration with a customer managed key, you can't change the customer managed key for the bucket's SSE-KMS configuration.In the Zonal endpoint API calls (except CopyObject and UploadPartCopy) using the REST API, you can't override the values of the encryption settings (
x-amz-server-side-encryption
,x-amz-server-side-encryption-aws-kms-key-id
,x-amz-server-side-encryption-context
, andx-amz-server-side-encryption-bucket-key-enabled
) from theCreateSession
request. You don't need to explicitly specify these encryption settings values in Zonal endpoint API calls, and Amazon S3 will use the encryption settings values from theCreateSession
request to protect new objects in the directory bucket.Note
When you use the CLI or the Amazon SDKs, for
CreateSession
, the session token refreshes automatically to avoid service interruptions when a session expires. The CLI or the Amazon SDKs use the bucket's default encryption configuration for theCreateSession
request. It's not supported to override the encryption settings values in theCreateSession
request. Also, in the Zonal endpoint API calls (except CopyObject and UploadPartCopy), it's not supported to override the values of the encryption settings from theCreateSession
request. - HTTP Host header syntax
-
Directory buckets - The HTTP Host header syntax is
Bucket_name.s3express-az_id.region.amazonaws.com
.
Request Syntax
GET /?session HTTP/1.1
Host: Bucket
.s3.amazonaws.com
x-amz-create-session-mode: SessionMode
x-amz-server-side-encryption: ServerSideEncryption
x-amz-server-side-encryption-aws-kms-key-id: SSEKMSKeyId
x-amz-server-side-encryption-context: SSEKMSEncryptionContext
x-amz-server-side-encryption-bucket-key-enabled: BucketKeyEnabled
URI Request Parameters
The request uses the following URI parameters.
- Bucket
-
The name of the bucket that you create a session for.
Required: Yes
- x-amz-create-session-mode
-
Specifies the mode of the session that will be created, either
ReadWrite
orReadOnly
. By default, aReadWrite
session is created. AReadWrite
session is capable of executing all the Zonal endpoint API operations on a directory bucket. AReadOnly
session is constrained to execute the following Zonal endpoint API operations:GetObject
,HeadObject
,ListObjectsV2
,GetObjectAttributes
,ListParts
, andListMultipartUploads
.Valid Values:
ReadOnly | ReadWrite
- x-amz-server-side-encryption
-
The server-side encryption algorithm to use when you store objects in the directory bucket.
For directory buckets, there are only two supported options for server-side encryption: server-side encryption with Amazon S3 managed keys (SSE-S3) (
AES256
) and server-side encryption with Amazon KMS keys (SSE-KMS) (aws:kms
). By default, Amazon S3 encrypts data with SSE-S3. For more information, see Protecting data with server-side encryption in the Amazon S3 User Guide.Valid Values:
AES256 | aws:kms | aws:kms:dsse
- x-amz-server-side-encryption-aws-kms-key-id
-
If you specify
x-amz-server-side-encryption
withaws:kms
, you must specify thex-amz-server-side-encryption-aws-kms-key-id
header with the ID (Key ID or Key ARN) of the Amazon KMS symmetric encryption customer managed key to use. Otherwise, you get an HTTP400 Bad Request
error. Only use the key ID or key ARN. The key alias format of the KMS key isn't supported. Also, if the KMS key doesn't exist in the same account that't issuing the command, you must use the full Key ARN not the Key ID.Your SSE-KMS configuration can only support 1 customer managed key per directory bucket for the lifetime of the bucket. The Amazon managed key (
aws/s3
) isn't supported. - x-amz-server-side-encryption-bucket-key-enabled
-
Specifies whether Amazon S3 should use an S3 Bucket Key for object encryption with server-side encryption using Amazon KMS keys (SSE-KMS).
S3 Bucket Keys are always enabled for
GET
andPUT
operations in a directory bucket and can’t be disabled. S3 Bucket Keys aren't supported, when you copy SSE-KMS encrypted objects from general purpose buckets to directory buckets, from directory buckets to general purpose buckets, or between directory buckets, through CopyObject, UploadPartCopy, the Copy operation in Batch Operations, or the import jobs. In this case, Amazon S3 makes a call to Amazon KMS every time a copy request is made for a KMS-encrypted object. - x-amz-server-side-encryption-context
-
Specifies the Amazon KMS Encryption Context as an additional encryption context to use for object encryption. The value of this header is a Base64-encoded string of a UTF-8 encoded JSON, which contains the encryption context as key-value pairs. This value is stored as object metadata and automatically gets passed on to Amazon KMS for future
GetObject
operations on this object.General purpose buckets - This value must be explicitly added during
CopyObject
operations if you want an additional encryption context for your object. For more information, see Encryption context in the Amazon S3 User Guide.Directory buckets - You can optionally provide an explicit encryption context value. The value must match the default encryption context - the bucket Amazon Resource Name (ARN). An additional encryption context value is not supported.
Request Body
The request does not have a request body.
Response Syntax
HTTP/1.1 200
x-amz-server-side-encryption: ServerSideEncryption
x-amz-server-side-encryption-aws-kms-key-id: SSEKMSKeyId
x-amz-server-side-encryption-context: SSEKMSEncryptionContext
x-amz-server-side-encryption-bucket-key-enabled: BucketKeyEnabled
<?xml version="1.0" encoding="UTF-8"?>
<CreateSessionOutput>
<Credentials>
<AccessKeyId>string</AccessKeyId>
<Expiration>timestamp</Expiration>
<SecretAccessKey>string</SecretAccessKey>
<SessionToken>string</SessionToken>
</Credentials>
</CreateSessionOutput>
Response Elements
If the action is successful, the service sends back an HTTP 200 response.
The response returns the following HTTP headers.
- x-amz-server-side-encryption
-
The server-side encryption algorithm used when you store objects in the directory bucket.
Valid Values:
AES256 | aws:kms | aws:kms:dsse
- x-amz-server-side-encryption-aws-kms-key-id
-
If you specify
x-amz-server-side-encryption
withaws:kms
, this header indicates the ID of the Amazon KMS symmetric encryption customer managed key that was used for object encryption. - x-amz-server-side-encryption-bucket-key-enabled
-
Indicates whether to use an S3 Bucket Key for server-side encryption with Amazon KMS keys (SSE-KMS).
- x-amz-server-side-encryption-context
-
If present, indicates the Amazon KMS Encryption Context to use for object encryption. The value of this header is a Base64-encoded string of a UTF-8 encoded JSON, which contains the encryption context as key-value pairs. This value is stored as object metadata and automatically gets passed on to Amazon KMS for future
GetObject
operations on this object.
The following data is returned in XML format by the service.
- CreateSessionOutput
-
Root level tag for the CreateSessionOutput parameters.
Required: Yes
- Credentials
-
The established temporary security credentials for the created session.
Type: SessionCredentials data type
Errors
- NoSuchBucket
-
The specified bucket does not exist.
HTTP Status Code: 404
See Also
For more information about using this API in one of the language-specific Amazon SDKs, see the following: