### 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_
kwargs = {}
    if algo.startswith("RSA"):
        if "PKCS" in algo:
            kwargs["padding"] = padding.PKCS1v15()
        elif "PSS" in algo:
            kwargs["padding"] = padding.PSS(
                mgf=padding.MGF1(hashes.SHA256()), salt_length=padding.PSS.MAX_LENGTH
            )
        else:
            LOG.warning("Unsupported padding in SigningAlgorithm '%s'", algo)
    if "SHA_256" in algo:
        kwargs["algorithm"] = hashes.SHA256()
    elif "SHA_384" in algo:
        kwargs["algorithm"] = hashes.SHA384()
    elif "SHA_512" in algo:
        kwargs["algorithm"] = hashes.SHA512()
    else:
        LOG.warning("Unsupported hash type in SigningAlgorithm '%s'", algo)
    if algo.startswith("ECDSA"):
        kwargs["signature_algorithm"] = ec.ECDSA(algorithm=kwargs.pop("algorithm", None))
    
    signature = key_pair["_key_"].sign(data=message, **kwargs)
    result = {
        "KeyId": key_id,
        "Signature": to_str(base64.b64encode(signature)),
        "SigningAlgorithm": algo,
    }
    set_response_content(response, json.dumps(result))
    return response
def search_key_pair(data, response):