### 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_
port = port or config.service_port("kms")
    backend_port = get_free_tcp_port()
    kms_binary = INSTALL_PATH_KMS_BINARY_PATTERN.replace(
        "<arch>", f"{platform.system().lower()}-{get_arch()}"
    )
    log_startup_message("KMS")
    start_proxy_for_service("kms", port, backend_port, update_listener)
    env_vars = {
        "PORT": str(backend_port),
        "KMS_REGION": config.DEFAULT_REGION,
        "REGION": config.DEFAULT_REGION,
        "KMS_ACCOUNT_ID": TEST_AWS_ACCOUNT_ID,
        "ACCOUNT_ID": TEST_AWS_ACCOUNT_ID,
    }
    if config.dirs.data:
        env_vars["KMS_DATA_PATH"] = config.dirs.data
    result = do_run(kms_binary, asynchronous, env_vars=env_vars)
    wait_for_port_open(backend_port)
    return result
def start_kms_moto(port=None, backend_port=None, asynchronous=None, update_listener=None):