I'm trying to solve an issue with my AWS Cloudformation template. The template I have includes a VPC with a private subnet, and a VPC endpoint to allow connections to S3 buckets. The bucket itself includes 3 buckets, and I have a couple of preexisting buckets already said up in the same region (in this case, eu-west-1).

I use aws-cli to log into an EC2 instance in the private subnet, then use aws-cli commands to access S3 (e.g. sudo aws s3 ls bucketname)

My problem is that I can only list the content of pre-existing buckets in that region, or new buckets that I create manually through the website. When I try to list cloudformation-generated buckets it just hangs and times out:

[ec2-user@ip-10-44-1-129 ~]$ sudo aws s3 ls testbucket
HTTPSConnectionPool(host='vltestbucketxxx.s3.amazonaws.com', port=443): Max retries exceeded with url: /?delimiter=%2F&prefix=&encoding-type=url (Caused by ConnectTimeoutError(<botocore.awsrequest.AWSHTTPSConnection object at 0x7f2cc0bcf110>, 'Connection to vltestbucketxxx.s3.amazonaws.com timed out. (connect timeout=60)'))

It does not seem to be related to the VPC endpoint (setting the config to allow everything has no effect)

{
    "Statement": [
        {
            "Action": "*",
            "Effect": "Allow",
            "Resource": "*",
            "Principal": "*"
        }
    ]
}

nor does accesscontrol seem to affect it.

{
  "Resources": {
    "testbucket": {
      "Type": "AWS::S3::Bucket",
      "Properties": {
        "AccessControl": "PublicReadWrite",
        "BucketName": "testbucket"
      }
    }
  }
}

Bucket policies don't seem to be the issue either (I've generated buckets with no policy attached, and again only the cloudformation generated ones time out). On the website, configuration for a bucket that connects and one that times out looks identical to me.

Trying to access buckets in other regions also times out, but as I understood it cloudformation generates buckets in the same region as the VPC, so that shouldn't be it (the website also shows the buckets to be in the same region).

Does anyone have an idea of what the issue might be?

Edit: I can connect from the VPC public subnet, so maybe it is an endpoint problem after all?