Cloudformation VPC S3 interface endpoint with PrivateDnsEnabled and PrivateDnsOnlyForInboundResolverEndpoint set to false

Question

So im trying to create S3 VPC interface endpoint using Cloudformation.

there is a field called "PrivateDnsOnlyForInboundResolverEndpoint" which is set to true automatically by default if I enable "private DNS names" to true.

I want to create the endpoint with private DNS names enabled but PrivateDnsOnlyForInboundResolverEndpoint set to false, for some reason I`m not able to to that.

There is no mention for it in the https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-vpcendpoint.html

Also, it seems to be available only for the AWS cli https://docs.aws.amazon.com/AmazonS3/latest/userguide/privatelink-interface-endpoints.html

Any suggestions ?

My current template looks like so:

```
AWSTemplateFormatVersion: '2010-09-09'
Description: CloudFormation template to create VPC interface endpoint for S3
Parameters:
  VPCId:
    Type: String
    Description: VPC to create the endpoint in
  SubnetId1:
    Type: String
    Description: Subnet ID for endpoint
Resources:
  S3VPCEndpoint:
    Type: 'AWS::EC2::VPCEndpoint'
    Properties:
      VpcId: !Ref VPCId
      SubnetIds: [!Ref SubnetId1]
      ServiceName: 'com.amazonaws.us-east-2.s3'
      VpcEndpointType: Interface
      PrivateDnsEnabled: true
```

I would imagine it would like so:
```
DnsOptions:
  PrivateDnsOnlyForInboundResolverEndpoint: false
```

Answer

This can be achieved by invoking a lambda function from CloudFormation template with below steps.

1/ Create a lambda function with IAM permissions which can take input from CloudFormation, create vpc endpoint and return response to CloudFormation. https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2/client/create_vpc_endpoint.html
2/ Update CloudFormation template to invoke this lambda function

Ref: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/walkthrough-custom-resources-lambda-lookup-amiids.html

Answer

I also have this problem and have resorted to just manually creating the endpoints outside of the CF template. Cloudformation has a surprising number of bugs and limited features/properties of resources missing etc.

To add more context, I specifically have this problem 'PrivateDnsOnlyForInboundResolverEndpoint' only for the S3 endpoint interface type.  I have successfully created an ec2 endpoint interface without a problem. My new solution is to use a Gateway endpoint for  S3 instead.

Answer

I agree with you. It seems that there is no way to specify "PrivateDnsOnlyForInboundResolverEndpoint" field via AWS CloudFormation.
You may use [Former2](https://www.former2.com/) to confirm whether such field existis or not by scanning existing VPCEndpoint resource.

Cloudformation VPC S3 interface endpoint with PrivateDnsEnabled and PrivateDnsOnlyForInboundResolverEndpoint set to false

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