Design for Seaweed-FS security

Design Objectives
	Security can mean many different things. The original vision is that: if you have one machine lying around
	somewhere with some disk space, it should be able to join your file system to contribute some disk space and
	network bandwidth.

	To achieve this purpose, the security should be able to:
	1. Secure the inter-server communication. Only real cluster servers can join and communicate.
	2. allow clients to securely write to volume servers

Non Objective
	Multi-tenant support. Avoid filers or clients cross-updating files.
	User specific access control.

Design Architect
	master, and volume servers all talk securely via 2-way SSL for admin.
	upon joining, master gives its secret key to volume servers.
	filer or clients talk to master to get secret key, and use the key to generate JWT to write on volume server.
	A side benefit:
		a time limited read feature?
	4. volume server needs to expose https ports

HTTP Connections
	clear http
		filer~>master, need to get a JWT from master
		filer~>volume
	2-way https
		master~ssl~>volume
		volume~ssl~>master

file uploading:
	when volume server starts, it asks master for the secret key to decode JWT
	when filer/clients wants to upload, master generate a JWT
		filer~>volume(public port)
		master~>volume(public port)