Amazon S3 Construct Library

---

> AWS CDK v1 has reached End-of-Support on 2023-06-01. > This package is no longer being updated, and users should migrate to AWS CDK v2. > > For more information on how to migrate, see the Migrating to AWS CDK v2 guide.

---

Define an unencrypted S3 bucket.

bucket = s3.Bucket(self, "MyFirstBucket")

Bucket constructs expose the following deploy-time attributes:

• bucketArn - the ARN of the bucket (i.e. arn:aws:s3:::bucket_name)
• bucketName - the name of the bucket (i.e. bucket_name)
• bucketWebsiteUrl - the Website URL of the bucket (i.e. http://bucket_name.s3-website-us-west-1.amazonaws.com)
• bucketDomainName - the URL of the bucket (i.e. bucket_name.s3.amazonaws.com)
• bucketDualStackDomainName - the dual-stack URL of the bucket (i.e. bucket_name.s3.dualstack.eu-west-1.amazonaws.com)
• bucketRegionalDomainName - the regional URL of the bucket (i.e. bucket_name.s3.eu-west-1.amazonaws.com)
• arnForObjects(pattern) - the ARN of an object or objects within the bucket (i.e. arn:aws:s3:::bucket_name/exampleobject.png or arn:aws:s3:::bucket_name/Development/*)
• urlForObject(key) - the HTTP URL of an object within the bucket (i.e. https://s3.cn-north-1.amazonaws.com.cn/china-bucket/mykey)
• virtualHostedUrlForObject(key) - the virtual-hosted style HTTP URL of an object within the bucket (i.e. https://china-bucket-s3.cn-north-1.amazonaws.com.cn/mykey)
• s3UrlForObject(key) - the S3 URL of an object within the bucket (i.e. s3://bucket/mykey)

Encryption

Define a KMS-encrypted bucket:

bucket = s3.Bucket(self, "MyEncryptedBucket",
    encryption=s3.BucketEncryption.KMS
)

# you can access the encryption key:
assert(bucket.encryption_key instanceof kms.Key)

You can also supply your own key:

my_kms_key = kms.Key(self, "MyKey")

bucket = s3.Bucket(self, "MyEncryptedBucket",
    encryption=s3.BucketEncryption.KMS,
    encryption_key=my_kms_key
)

assert(bucket.encryption_key == my_kms_key)

Enable KMS-SSE encryption via S3 Bucket Keys:

bucket = s3.Bucket(self, "MyEncryptedBucket",
    encryption=s3.BucketEncryption.KMS,
    bucket_key_enabled=True
)

Use BucketEncryption.ManagedKms to use the S3 master KMS key:

bucket = s3.Bucket(self, "Buck",
    encryption=s3.BucketEncryption.KMS_MANAGED
)

assert(bucket.encryption_key == null)

Permissions

A bucket policy will be automatically created for the bucket upon the first call to addToResourcePolicy(statement):

bucket = s3.Bucket(self, "MyBucket")
result = bucket.add_to_resource_policy(iam.PolicyStatement(
    actions=["s3:GetObject"],
    resources=[bucket.arn_for_objects("file.txt")],
    principals=[iam.AccountRootPrincipal()]
))

If you try to add a policy statement to an existing bucket, this method will not do anything:

bucket = s3.Bucket.from_bucket_name(self, "existingBucket", "bucket-name")

# No policy statement will be added to the resource
result = bucket.add_to_resource_policy(iam.PolicyStatement(
    actions=["s3:GetObject"],
    resources=[bucket.arn_for_objects("file.txt")],
    principals=[iam.AccountRootPrincipal()]
))

That's because it's not possible to tell whether the bucket already has a policy attached, let alone to re-use that policy to add more statements to it. We recommend that you always check the result of the call:

bucket = s3.Bucket(self, "MyBucket")
result = bucket.add_to_resource_policy(iam.PolicyStatement(
    actions=["s3:GetObject"],
    resources=[bucket.arn_for_objects("file.txt")],
    principals=[iam.AccountRootPrincipal()]
))

if not result.statement_added:
    pass

The bucket policy can be directly accessed after creation to add statements or adjust the removal policy.

bucket = s3.Bucket(self, "MyBucket")
bucket.policy.apply_removal_policy(cdk.RemovalPolicy.RETAIN)

Most of the time, you won't have to manipulate the bucket policy directly. Instead, buckets have "grant" methods called to give prepackaged sets of permissions to other resources. For example:

# my_lambda: lambda.Function


bucket = s3.Bucket(self, "MyBucket")
bucket.grant_read_write(my_lambda)

Will give the Lambda's execution role permissions to read and write from the bucket.

AWS Foundational Security Best Practices

Enforcing SSL

To require all requests use Secure Socket Layer (SSL):

bucket = s3.Bucket(self, "Bucket",
    enforce_sSL=True
)

Sharing buckets between stacks

To use a bucket in a different stack in the same CDK application, pass the object to the other stack:

#
# Stack that defines the bucket
#
class Producer(cdk.Stack):

    def __init__(self, scope, id, *, description=None, env=None, stackName=None, tags=None, synthesizer=None, terminationProtection=None, analyticsReporting=None):
        super().__init__(scope, id, description=description, env=env, stackName=stackName, tags=tags, synthesizer=synthesizer, terminationProtection=terminationProtection, analyticsReporting=analyticsReporting)

        bucket = s3.Bucket(self, "MyBucket",
            removal_policy=cdk.RemovalPolicy.DESTROY
        )
        self.my_bucket = bucket

#
# Stack that consumes the bucket
#
class Consumer(cdk.Stack):
    def __init__(self, scope, id, *, userBucket, description=None, env=None, stackName=None, tags=None, synthesizer=None, terminationProtection=None, analyticsReporting=None):
        super().__init__(scope, id, userBucket=userBucket, description=description, env=env, stackName=stackName, tags=tags, synthesizer=synthesizer, terminationProtection=terminationProtection, analyticsReporting=analyticsReporting)

        user = iam.User(self, "MyUser")
        user_bucket.grant_read_write(user)

producer = Producer(app, "ProducerStack")
Consumer(app, "ConsumerStack", user_bucket=producer.my_bucket)

Importing existing buckets

To import an existing bucket into your CDK application, use the Bucket.fromBucketAttributes factory method. This method accepts BucketAttributes which describes the properties of an already existing bucket:

# my_lambda: lambda.Function

bucket = s3.Bucket.from_bucket_attributes(self, "ImportedBucket",
    bucket_arn="arn:aws:s3:::my-bucket"
)

# now you can just call methods on the bucket
bucket.add_event_notification(s3.EventType.OBJECT_CREATED, s3n.LambdaDestination(my_lambda), prefix="home/myusername/*")

Alternatively, short-hand factories are available as Bucket.fromBucketName and Bucket.fromBucketArn, which will derive all bucket attributes from the bucket name or ARN respectively:

by_name = s3.Bucket.from_bucket_name(self, "BucketByName", "my-bucket")
by_arn = s3.Bucket.from_bucket_arn(self, "BucketByArn", "arn:aws:s3:::my-bucket")

The bucket's region defaults to the current stack's region, but can also be explicitly set in cases where one of the bucket's regional properties needs to contain the correct values.

my_cross_region_bucket = s3.Bucket.from_bucket_attributes(self, "CrossRegionImport",
    bucket_arn="arn:aws:s3:::my-bucket",
    region="us-east-1"
)

Bucket Notifications

The Amazon S3 notification feature enables you to receive notifications when certain events happen in your bucket as described under [S3 Bucket Notifications] of the S3 Developer Guide.

To subscribe for bucket notifications, use the bucket.addEventNotification method. The bucket.addObjectCreatedNotification and bucket.addObjectRemovedNotification can also be used for these common use cases.

The following example will subscribe an SNS topic to be notified of all s3:ObjectCreated:* events:

bucket = s3.Bucket(self, "MyBucket")
topic = sns.Topic(self, "MyTopic")
bucket.add_event_notification(s3.EventType.OBJECT_CREATED, s3n.SnsDestination(topic))

This call will also ensure that the topic policy can accept notifications for this specific bucket.

Supported S3 notification targets are exposed by the @aws-cdk/aws-s3-notifications package.

It is also possible to specify S3 object key filters when subscribing. The following example will notify myQueue when objects prefixed with foo/ and have the .jpg suffix are removed from the bucket.

# my_queue: sqs.Queue

bucket = s3.Bucket(self, "MyBucket")
bucket.add_event_notification(s3.EventType.OBJECT_REMOVED,
    s3n.SqsDestination(my_queue), prefix="foo/", suffix=".jpg")

Adding notifications on existing buckets:

# topic: sns.Topic

bucket = s3.Bucket.from_bucket_attributes(self, "ImportedBucket",
    bucket_arn="arn:aws:s3:::my-bucket"
)
bucket.add_event_notification(s3.EventType.OBJECT_CREATED, s3n.SnsDestination(topic))

When you add an event notification to a bucket, a custom resource is created to manage the notifications. By default, a new role is created for the Lambda function that implements this feature. If you want to use your own role instead, you should provide it in the Bucket constructor:

# my_role: iam.IRole

bucket = s3.Bucket(self, "MyBucket",
    notifications_handler_role=my_role
)

Whatever role you provide, the CDK will try to modify it by adding the permissions from AWSLambdaBasicExecutionRole (an AWS managed policy) as well as the permissions s3:PutBucketNotification and s3:GetBucketNotification. If you’re passing an imported role, and you don’t want this to happen, configure it to be immutable:

imported_role = iam.Role.from_role_arn(self, "role", "arn:aws:iam::123456789012:role/RoleName",
    mutable=False
)

> If you provide an imported immutable role, make sure that it has at least all > the permissions mentioned above. Otherwise, the deployment will fail!

EventBridge notifications

Amazon S3 can send events to Amazon EventBridge whenever certain events happen in your bucket. Unlike other destinations, you don't need to select which event types you want to deliver.

The following example will enable EventBridge notifications:

bucket = s3.Bucket(self, "MyEventBridgeBucket",
    event_bridge_enabled=True
)

Block Public Access

Use blockPublicAccess to specify block public access settings on the bucket.

Enable all block public access settings:

bucket = s3.Bucket(self, "MyBlockedBucket",
    block_public_access=s3.BlockPublicAccess.BLOCK_ALL
)

Block and ignore public ACLs:

bucket = s3.Bucket(self, "MyBlockedBucket",
    block_public_access=s3.BlockPublicAccess.BLOCK_ACLS
)

Alternatively, specify the settings manually:

bucket = s3.Bucket(self, "MyBlockedBucket",
    block_public_access=s3.BlockPublicAccess(block_public_policy=True)
)

When blockPublicPolicy is set to true, grantPublicRead() throws an error.

Logging configuration

Use serverAccessLogsBucket to describe where server access logs are to be stored.

access_logs_bucket = s3.Bucket(self, "AccessLogsBucket")

bucket = s3.Bucket(self, "MyBucket",
    server_access_logs_bucket=access_logs_bucket
)

It's also possible to specify a prefix for Amazon S3 to assign to all log object keys.

access_logs_bucket = s3.Bucket(self, "AccessLogsBucket")

bucket = s3.Bucket(self, "MyBucket",
    server_access_logs_bucket=access_logs_bucket,
    server_access_logs_prefix="logs"
)

S3 Inventory

An inventory contains a list of the objects in the source bucket and metadata for each object. The inventory lists are stored in the destination bucket as a CSV file compressed with GZIP, as an Apache optimized row columnar (ORC) file compressed with ZLIB, or as an Apache Parquet (Parquet) file compressed with Snappy.

You can configure multiple inventory lists for a bucket. You can configure what object metadata to include in the inventory, whether to list all object versions or only current versions, where to store the inventory list file output, and whether to generate the inventory on a daily or weekly basis.

inventory_bucket = s3.Bucket(self, "InventoryBucket")

data_bucket = s3.Bucket(self, "DataBucket",
    inventories=[s3.Inventory(
        frequency=s3.InventoryFrequency.DAILY,
        include_object_versions=s3.InventoryObjectVersion.CURRENT,
        destination=s3.InventoryDestination(
            bucket=inventory_bucket
        )
    ), s3.Inventory(
        frequency=s3.InventoryFrequency.WEEKLY,
        include_object_versions=s3.InventoryObjectVersion.ALL,
        destination=s3.InventoryDestination(
            bucket=inventory_bucket,
            prefix="with-all-versions"
        )
    )
    ]
)

If the destination bucket is created as part of the same CDK application, the necessary permissions will be automatically added to the bucket policy. However, if you use an imported bucket (i.e Bucket.fromXXX()), you'll have to make sure it contains the following policy document:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "InventoryAndAnalyticsExamplePolicy",
      "Effect": "Allow",
      "Principal": { "Service": "s3.amazonaws.com" },
      "Action": "s3:PutObject",
      "Resource": ["arn:aws:s3:::destinationBucket/*"]
    }
  ]
}

Website redirection

You can use the two following properties to specify the bucket redirection policy. Please note that these methods cannot both be applied to the same bucket.

Static redirection

You can statically redirect a to a given Bucket URL or any other host name with websiteRedirect:

bucket = s3.Bucket(self, "MyRedirectedBucket",
    website_redirect=s3.RedirectTarget(host_name="www.example.com")
)

Routing rules

Alternatively, you can also define multiple websiteRoutingRules, to define complex, conditional redirections:

bucket = s3.Bucket(self, "MyRedirectedBucket",
    website_routing_rules=[s3.RoutingRule(
        host_name="www.example.com",
        http_redirect_code="302",
        protocol=s3.RedirectProtocol.HTTPS,
        replace_key=s3.ReplaceKey.prefix_with("test/"),
        condition=s3.RoutingRuleCondition(
            http_error_code_returned_equals="200",
            key_prefix_equals="prefix"
        )
    )]
)

Filling the bucket as part of deployment

To put files into a bucket as part of a deployment (for example, to host a website), see the @aws-cdk/aws-s3-deployment package, which provides a resource that can do just that.

The URL for objects

S3 provides two types of URLs for accessing objects via HTTP(S). Path-Style and Virtual Hosted-Style URL. Path-Style is a classic way and will be deprecated. We recommend to use Virtual Hosted-Style URL for newly made bucket.

You can generate both of them.

bucket = s3.Bucket(self, "MyBucket")
bucket.url_for_object("objectname") # Path-Style URL
bucket.virtual_hosted_url_for_object("objectname") # Virtual Hosted-Style URL
bucket.virtual_hosted_url_for_object("objectname", regional=False)

Object Ownership

You can use one of following properties to specify the bucket object Ownership.

Object writer

The Uploading account will own the object.

s3.Bucket(self, "MyBucket",
    object_ownership=s3.ObjectOwnership.OBJECT_WRITER
)

Bucket owner preferred

The bucket owner will own the object if the object is uploaded with the bucket-owner-full-control canned ACL. Without this setting and canned ACL, the object is uploaded and remains owned by the uploading account.

s3.Bucket(self, "MyBucket",
    object_ownership=s3.ObjectOwnership.BUCKET_OWNER_PREFERRED
)

Bucket owner enforced (recommended)

ACLs are disabled, and the bucket owner automatically owns and has full control over every object in the bucket. ACLs no longer affect permissions to data in the S3 bucket. The bucket uses policies to define access control.

s3.Bucket(self, "MyBucket",
    object_ownership=s3.ObjectOwnership.BUCKET_OWNER_ENFORCED
)

Bucket deletion

When a bucket is removed from a stack (or the stack is deleted), the S3 bucket will be removed according to its removal policy (which by default will simply orphan the bucket and leave it in your AWS account). If the removal policy is set to RemovalPolicy.DESTROY, the bucket will be deleted as long as it does not contain any objects.

To override this and force all objects to get deleted during bucket deletion, enable theautoDeleteObjects option.

bucket = s3.Bucket(self, "MyTempFileBucket",
    removal_policy=cdk.RemovalPolicy.DESTROY,
    auto_delete_objects=True
)

Warning if you have deployed a bucket with autoDeleteObjects: true, switching this to false in a CDK version before 1.126.0 will lead to all objects in the bucket being deleted. Be sure to update your bucket resources by deploying with CDK version 1.126.0 or later before switching this value to false.

Transfer Acceleration

Transfer Acceleration can be configured to enable fast, easy, and secure transfers of files over long distances:

bucket = s3.Bucket(self, "MyBucket",
    transfer_acceleration=True
)

To access the bucket that is enabled for Transfer Acceleration, you must use a special endpoint. The URL can be generated using method transferAccelerationUrlForObject:

bucket = s3.Bucket(self, "MyBucket",
    transfer_acceleration=True
)
bucket.transfer_acceleration_url_for_object("objectname")

Intelligent Tiering

Intelligent Tiering can be configured to automatically move files to glacier:

s3.Bucket(self, "MyBucket",
    intelligent_tiering_configurations=[s3.IntelligentTieringConfiguration(
        name="foo",
        prefix="folder/name",
        archive_access_tier_time=cdk.Duration.days(90),
        deep_archive_access_tier_time=cdk.Duration.days(180),
        tags=[s3.Tag(key="tagname", value="tagvalue")]
    )]
)

Lifecycle Rule

Managing lifecycle can be configured transition or expiration actions.

bucket = s3.Bucket(self, "MyBucket",
    lifecycle_rules=[s3.LifecycleRule(
        abort_incomplete_multipart_upload_after=cdk.Duration.minutes(30),
        enabled=False,
        expiration=cdk.Duration.days(30),
        expiration_date=Date(),
        expired_object_delete_marker=False,
        id="id",
        noncurrent_version_expiration=cdk.Duration.days(30),

        # the properties below are optional
        noncurrent_versions_to_retain=123,
        noncurrent_version_transitions=[s3.NoncurrentVersionTransition(
            storage_class=s3.StorageClass.GLACIER,
            transition_after=cdk.Duration.days(30),

            # the properties below are optional
            noncurrent_versions_to_retain=123
        )],
        object_size_greater_than=500,
        prefix="prefix",
        object_size_less_than=10000,
        transitions=[s3.Transition(
            storage_class=s3.StorageClass.GLACIER,

            # the properties below are optional
            transition_after=cdk.Duration.days(30),
            transition_date=Date()
        )]
    )]
)