rpc_client.py: Allow for optional SSL_Context

[Nico-VanHaaster]

Implementing the pools protocol shows us that we must have the Private \ Public Keys available on the current pool server. As the pool server will be the central attack vector we are looking at ways to reduce the capabilities for an attacker to gain unauthorised access to the nodes which are running the pool wallets.

In the current design the private \ public keys must be stored in a physical file based on the config.yaml file path. This of course is easily accessed by an unauthorized actor.

Now one could construct the class themselves however from our understanding the only reliance on the config.yaml file is to establish the ssl_context. I am not that great at python however the change below would allow integrators to create an RPC client without the need for the files to be stored on the actual file system.

@classmethod
    async def create(cls, self_hostname: str, port: uint16, root_path, net_config, ssl_context = None):
        self = cls()
        self.url = f"https://{self_hostname}:{str(port)}/"
        self.session = aiohttp.ClientSession()
        if ssl_context  is None:
            ca_crt_path, ca_key_path = private_ssl_ca_paths(root_path, net_config)
            crt_path = root_path / net_config["daemon_ssl"]["private_crt"]
            key_path = root_path / net_config["daemon_ssl"]["private_key"]
            self.ssl_context = ssl_context_for_client(ca_crt_path, ca_key_path, crt_path, key_path)
        else:
            self.ssl_context = ssl_context
        self.closing_task = None
        return self

Ideally the pool server would have no reliance on any physical files that contain any sensitive data to operate.

Welcome thoughts.