How to add S3 BucketPolicy with AWS CDK? - amazon-web-services

Question

I wanna translate this CloudFormation piece into CDK:
Type: AWS::S3::BucketPolicy
Properties:
Bucket:
Ref: S3BucketImageUploadBuffer
PolicyDocument:
Version: "2012-10-17"
Statement:
Action:
- s3:PutObject
- s3:PutObjectAcl
Effect: Allow
Resource:
- ...
Looking at the documentation here, I don't see a way to provide the policy document itself.

Answer 1

This is an example from a working CDK-Stack:
artifactBucket.addToResourcePolicy(
new PolicyStatement({
resources: [
this.pipeline.artifactBucket.arnForObjects("*"),
this.pipeline.artifactBucket.bucketArn],
],
actions: ["s3:List*", "s3:Get*"],
principals: [new ArnPrincipal(this.deploymentRole.roleArn)]
})
);

Answer 2

Building on #Thomas Wagner's answer, this is how I did this. I was trying to limit the bucket to a given IP range:
import * as cdk from '#aws-cdk/core';
import * as s3 from '#aws-cdk/aws-s3';
import * as s3Deployment from '#aws-cdk/aws-s3-deployment';
import * as iam from '#aws-cdk/aws-iam';
export class StaticSiteStack extends cdk.Stack {
constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props);
// Bucket where frontend site goes.
const mySiteBucket = new s3.Bucket(this, 'mySiteBucket', {
websiteIndexDocument: "index.html"
});
let ipLimitPolicy = new iam.PolicyStatement({
actions: ['s3:Get*', 's3:List*'],
resources: [mySiteBucket.arnForObjects('*')],
principals: [new iam.AnyPrincipal()]
});
ipLimitPolicy.addCondition('IpAddress', {
"aws:SourceIp": ['1.2.3.4/22']
});
// Allow connections from my CIDR
mySiteBucket.addToResourcePolicy(ipLimitPolicy);
// Deploy assets
const mySiteDeploy = new s3Deployment.BucketDeployment(this, 'deployAdminSite', {
sources: [s3Deployment.Source.asset("./mysite")],
destinationBucket: mySiteBucket
});
}
}
I was able to use the s3.arnForObjects() and iam.AnyPrincipal() helper functions rather than specifying ARNs or Principals directly.
The assets I want to deploy to the bucket are kept in the root of my project directory in a directory called mysite, and then referenced via a call to s3Deployment.BucketDeployment. This can be any directory your build process has access to, of course.

Answer 3

The CDK does this a little differently. I believe you are supposed to use bucket.addToResourcePolicy, as documented here.

Answer 4

As per the original question, then the answer from #thomas-wagner is the way to go.
If anyone comes here looking for how to create the bucket policy for a CloudFront Distribution without creating a dependency on a bucket then you need to use the L1 construct CfnBucketPolicy (rough C# example below):
IOriginAccessIdentity originAccessIdentity = new OriginAccessIdentity(this, "origin-access-identity", new OriginAccessIdentityProps
{
Comment = "Origin Access Identity",
});
PolicyStatement bucketAccessPolicy = new PolicyStatement(new PolicyStatementProps
{
Effect = Effect.ALLOW,
Principals = new[]
{
originAccessIdentity.GrantPrincipal
},
Actions = new[]
{
"s3:GetObject",
},
Resources = new[]
{
Props.OriginBucket.ArnForObjects("*"),
}
});
_ = new CfnBucketPolicy(this, $"bucket-policy", new CfnBucketPolicyProps
{
Bucket = Props.OriginBucket.BucketName,
PolicyDocument = new PolicyDocument(new PolicyDocumentProps
{
Statements = new[]
{
bucketAccessPolicy,
},
}),
});
Where Props.OriginBucket is an instance of IBucket (just a bucket).