### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to sign some document using Localstack KMS inside a lambda container (also running on localstack), the localstack KMS listener returns some unknown error.

The KMS key and lambda containers have been created from the same CDK app deploy, and I can see all the resources in the localstack web console.

The test application I'm using to prove this behaviour is available here:
https://github.com/LukaHedt/localstack_kms_test

Instructions to run are in the main Readme, and the `/localstack/Readme.md` file.

`aws-sdk` returns an unknown error, and the localstack docker logs that I receive are available here:
https://pastebin.com/58Z3fXi3

Have done an amount of testing and can confidently claim the following:
- Have tested on multiple machines with the same outcome
- Doesn’t make a difference if I specify an ARN or a KeyID in the signing request
- Downgrading localstack versions either didn’t make a difference, or I couldn’t actually deploy a localstack container with version 0.12.20 or lower.

### Expected Behavior

KMS Sign should return a signature for the given payload.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

Test application demonstrating the current behaviour is available here:

https://github.com/LukaHedt/localstack_kms_test

Full instructions to run are in the `/localstack/Readme.md` file.


### Environment

```markdown
- OS: MacOS Monteray 12.3
- LocalStack: 0.14.0
```


### Anything else?

_No response_
"SizeBytes": -1,
            },
            "awsRegion": aws_stack.get_region(),
            "eventSource": "aws:dynamodb",
        }
        records = [record]
        streams_enabled_cache = {}
        table_name = data.get("TableName")
        event_sources_or_streams_enabled = has_event_sources_or_streams_enabled(
            table_name, streams_enabled_cache
        )
        if action == "UpdateItem":
            if response.status_code == 200 and event_sources_or_streams_enabled:
                existing_item = self._thread_local("existing_item")
                record["eventName"] = "INSERT" if not existing_item else "MODIFY"
                record["eventID"] = short_uid()
                updated_item = ItemFinder.find_existing_item(data)
                if not updated_item:
                    return
                record["dynamodb"]["Keys"] = data["Key"]
                if existing_item:
                    record["dynamodb"]["OldImage"] = existing_item
                record["dynamodb"]["NewImage"] = updated_item
                record["dynamodb"]["SizeBytes"] = len(json.dumps(updated_item))
                stream_spec = dynamodb_get_table_stream_specification(table_name=table_name)
                if stream_spec:
                    record["dynamodb"]["StreamViewType"] = stream_spec["StreamViewType"]
        elif action == "ExecuteStatement":
            table_name = extract_table_name_from_partiql_update(data["Statement"])
            event_sources_or_streams_enabled = table_name and has_event_sources_or_streams_enabled(