Motivation

This PR implements a small workaround for S3 Virtual-Hosted requests done without an s3. prefixed endpoint.

We sometimes have the case that we cannot update the S3-only endpoint URL for some tools interacting with LocalStack, like IaC (CDK, for ex.) or SDKs.

For context, we implemented a prefixed endpoint for S3 to make sure we can properly parse the request, and know what is the bucket name in the host (anything before the s3. prefix, if there is anything, otherwise, we fallback to the path style access).

This can lead to issues where a request done to http://test-bucket.localhost.localstack.cloud:4566/test-key would not be properly parsed, because S3 would not try to parse the bucket name out of the host, and see test-key as the bucket name.

This workaround allows the S3 parser to parse the request if and only if there is something before the LOCALSTACK_HOST environment variable. This can enable some use-cases, but not all. We're still not entirely sure this could not lead to more complications, like requests being interpreted as virtual-hosted when not (what about the location service, which could have an endpoint named http://location.localhost.localstack.cloud:4566, this request would be directed to the location service even though it could be a valid bucket name. Or deadline)

We can park this work for now and revisit if we have a strong need for it. It was validated that it did fix some simple use-cases, but it has some other limitations:

• non-signed requests in Virtual-Hosted mode won't work as they won't be flagged as S3 requests
• CORS behavior will not work for non-prefixed S3 endpoint in virtual-hosted mode

\cc @joe4dev

Changes

• add a workaround in the S3 Parser to properly detect Virtual-Hosted requests if the Host contains the LOCALSTACK_HOST value and be able to parse the request

TODO

We still need to add some tests around the limitations to have them documented and tested