### 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_
OPENSEARCH_ENDPOINT_STRATEGY = (
    os.environ.get("OPENSEARCH_ENDPOINT_STRATEGY", "").strip()
    or os.environ.get("ES_ENDPOINT_STRATEGY", "").strip()
    or "domain"
)
if OPENSEARCH_ENDPOINT_STRATEGY == "off":
    OPENSEARCH_ENDPOINT_STRATEGY = "port"
OPENSEARCH_MULTI_CLUSTER = is_env_not_false("OPENSEARCH_MULTI_CLUSTER") or is_env_true(
    "ES_MULTI_CLUSTER"
)
CONFIG_ENV_VARS = [
    "BUCKET_MARKER_LOCAL",
    "DEBUG",
    "DEFAULT_REGION",
    "DEVELOP",
    "DEVELOP_PORT",
    "DISABLE_CORS_CHECKS",
    "DISABLE_CUSTOM_CORS_APIGATEWAY",
    "DISABLE_CUSTOM_CORS_S3",
    "DISABLE_EVENTS",
    "DOCKER_BRIDGE_IP",
    "DYNAMODB_ERROR_PROBABILITY",
    "DYNAMODB_HEAP_SIZE",
    "DYNAMODB_READ_ERROR_PROBABILITY",
    "DYNAMODB_WRITE_ERROR_PROBABILITY",
    "EAGER_SERVICE_LOADING",
    "EDGE_BIND_HOST",
    "EDGE_FORWARD_URL",
    "EDGE_PORT",
    "EDGE_PORT_HTTP",