# BucketPolicy

The bucket policy for an Amazon S3 bucket.

Policies define the operations that are allowed on this resource.

You almost never need to define this construct directly.

All AWS resources that support resource policies have a method called
`addToResourcePolicy()`, which will automatically create a new resource
policy if one doesn't exist yet, otherwise it will add to the existing
policy.

The bucket policy method is implemented differently than `addToResourcePolicy()`
as `BucketPolicy()` creates a new policy without knowing one earlier existed.
e.g. if during Bucket creation, if `autoDeleteObject:true`, these policies are
added to the bucket policy:
   ["s3:DeleteObject*", "s3:GetBucket*", "s3:List*", "s3:PutBucketPolicy"],
and when you add a new BucketPolicy with ["s3:GetObject", "s3:ListBucket"] on
this existing bucket, invoking `BucketPolicy()` will create a new Policy
without knowing one earlier exists already, so it creates a new one.
In this case, the custom resource handler will not have access to
`s3:GetBucketTagging` action which will cause failure during deletion of stack.

Hence its strongly recommended to use `addToResourcePolicy()` method to add
new permissions to existing policy.

Extends: Construct › Resource › BucketPolicy
Implements: IResource, IEnvironmentAware, IBucketPolicyRef, IConstruct, IDependable

- CloudFormation: [`AWS::S3::BucketPolicy`](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-s3-bucketpolicy.html)
- L1 type: [`CfnBucketPolicy`](/cdk/api/v2/docs/aws-cdk-lib.aws_s3.CfnBucketPolicy.html)
- Source: [`aws-s3/lib/bucket-policy.ts`](https://github.com/aws/aws-cdk/blob/v2.275.0/packages/aws-cdk-lib/aws-s3/lib/bucket-policy.ts#L61)
- Type last changed: v2.224.0 · 13 Nov 2025

## Example

```ts
const bucketName = "amzn-s3-demo-bucket";
const accessLogsBucket = new s3.Bucket(this, 'AccessLogsBucket', {
  objectOwnership: s3.ObjectOwnership.BUCKET_OWNER_ENFORCED,
  bucketName,
});

const bucketPolicy = new s3.CfnBucketPolicy(this, "BucketPolicy", {
  bucket: bucketName,
  policyDocument: {
    Statement: [
      {
        Action: 's3:*',
        Effect: 'Deny',
        Principal: {
          AWS: '*',
        },
        Resource: [
          accessLogsBucket.bucketArn,
          `${accessLogsBucket.bucketArn}/*`
        ],
      },
    ],
    Version: '2012-10-17',
  },
});

// Wrap L1 Construct with L2 Bucket Policy Construct. Subsequent
// generated bucket policy to allow access log delivery would append
// to the current policy.
s3.BucketPolicy.fromCfnBucketPolicy(bucketPolicy);

const bucket = new s3.Bucket(this, 'MyBucket', {
  serverAccessLogsBucket: accessLogsBucket,
  serverAccessLogsPrefix: 'logs',
});
```

## Initializer

```ts
new BucketPolicy(scope: Construct, id: string, props: BucketPolicyProps)
```

## Construct Props

- `bucket`: [IBucket](/cdk/api/v2/docs/aws-cdk-lib.aws_s3.IBucket.html) (required) — The Amazon S3 bucket that the policy applies to.

- `document`: [PolicyDocument](/cdk/api/v2/docs/aws-cdk-lib.aws_iam.PolicyDocument.html) — Policy document to apply to the bucket.

  **Default:** A new empty PolicyDocument will be created.

- `removalPolicy`: [RemovalPolicy](/cdk/api/v2/docs/aws-cdk-lib.RemovalPolicy.html) = RemovalPolicy.DESTROY. — Policy to apply when the policy is removed from this stack.

## Properties

- `bucket`: [IBucket](/cdk/api/v2/docs/aws-cdk-lib.aws_s3.IBucket.html) — The Bucket this Policy applies to.

- `bucketPolicyRef`: [BucketPolicyReference](/cdk/api/v2/docs/aws-cdk-lib.interfaces.aws_s3.BucketPolicyReference.html) — A reference to a BucketPolicy resource.

- `document`: [PolicyDocument](/cdk/api/v2/docs/aws-cdk-lib.aws_iam.PolicyDocument.html) — A policy document containing permissions to add to the specified bucket.

  For more information, see Access Policy Language Overview in the Amazon
  Simple Storage Service Developer Guide.

- `env`: [ResourceEnvironment](/cdk/api/v2/docs/aws-cdk-lib.interfaces.ResourceEnvironment.html) — The environment this resource belongs to.

  For resources that are created and managed in a Stack (those created by
  creating new class instances like `new Role()`, `new Bucket()`, etc.), this
  is always the same as the environment of the stack they belong to.

  For referenced resources (those obtained from referencing methods like
  `Role.fromRoleArn()`, `Bucket.fromBucketName()`, etc.), they might be
  different than the stack they were imported into.

- `node`: [Node](/cdk/api/v2/docs/constructs.Node.html) — The tree node.

- `PROPERTY_INJECTION_ID`: string (static) — Uniquely identifies this class.

- `stack`: [Stack](/cdk/api/v2/docs/aws-cdk-lib.Stack.html) — The stack in which this resource is defined.

## Methods

- `applyCrossStackReferenceStrength(strength: ReferenceStrength): void` — Override the cross-stack reference strength for this resource.

  When set, any cross-stack reference to this resource will use the specified
  mechanism instead of the global default determined by the
  `@aws-cdk/core:defaultCrossStackReferences` context key. This is useful for
  selectively weakening specific references to avoid the "deadly embrace" problem
  without changing the app-wide default.

  **Parameters**

  - `strength` — - The reference strength to use for this resource.

- `applyRemovalPolicy(removalPolicy: RemovalPolicy): void` — Sets the removal policy for the BucketPolicy.

  **Parameters**

  - `removalPolicy` — the RemovalPolicy to set.

- `fromCfnBucketPolicy(cfnBucketPolicy: CfnBucketPolicy): BucketPolicy // chainable` (static) — Create a mutable `BucketPolicy` from a `CfnBucketPolicy`.

- `isConstruct(x: any): boolean` (static) — Checks if `x` is a construct.

  Use this method instead of `instanceof` to properly detect `Construct`
  instances, even when the construct library is symlinked.

  Explanation: in JavaScript, multiple copies of the `constructs` library on
  disk are seen as independent, completely different libraries. As a
  consequence, the class `Construct` in each copy of the `constructs` library
  is seen as a different class, and an instance of one class will not test as
  `instanceof` the other class. `npm install` will not create installations
  like this, but users may manually symlink construct libraries together or
  use a monorepo tool: in those cases, multiple copies of the `constructs`
  library can be accidentally installed, and `instanceof` will behave
  unpredictably. It is safest to avoid using `instanceof`, and using
  this type-testing method instead.

  **Parameters**

  - `x` — Any object.

  **Returns:** true if `x` is an object created from a class which extends `Construct`.

- `isOwnedResource(construct: IConstruct): boolean` (static) — Returns true if the construct was created by CDK, and false otherwise.

- `isResource(construct: IConstruct): boolean` (static) — Check whether the given construct is a Resource.

- `toString(): string` — Returns a string representation of this construct.

- `with(...mixins: IMixin[]): IConstruct` — Applies one or more mixins to this construct.

  Mixins are applied in order. The list of constructs is captured at the
  start of the call, so constructs added by a mixin will not be visited.
  Use multiple `with()` calls if subsequent mixins should apply to added
  constructs.