### 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_
pass
SERVICE_PORTS = parse_service_ports()
def populate_config_env_var_names():
    global CONFIG_ENV_VARS
    for key, value in DEFAULT_SERVICE_PORTS.items():
        clean_key = key.upper().replace("-", "_")
        CONFIG_ENV_VARS += [
            clean_key + "_BACKEND",
            clean_key + "_PORT_EXTERNAL",
            "PROVIDER_OVERRIDE_" + clean_key,
        ]
    
    CONFIG_ENV_VARS += [
        "LOCALSTACK_" + v for v in CONFIG_ENV_VARS if not v.startswith("LOCALSTACK_")
    ]
    CONFIG_ENV_VARS = list(set(CONFIG_ENV_VARS))
populate_config_env_var_names()
def service_port(service_key: str, external: bool = False) -> int: