2.2.12 Cycle 12 - Sending messages across the network

Design

Objectives

Since the project is getting near the end of the time period allowed for development and the validation/transaction part of the blockchain doesn't exist outside of the theoretical space yet, but the majority communication layer is nearly finished I think it would be a good idea to get general communication working such that by the end of the allowed period of development the project exists in a form that is somewhat usable.

This form would effectively end up being a decentralised messaging service, which although is not quite the full blockchain that I was aiming for in the first place, still utilises a lot of the same networking and logic - due to effectively being a demo of the decentralised communication layer.

To do this, I will need to introduce a few new features that will build upon what I have created in previous cycles:

Generating message objects that state who created the object and provides a signature to prove it.
Sending these messages to all references stored on the node.
Receiving, validating, logging and forwarding these messages.

With these features the messages being sent will be very similar to the transactions that were initially hypothesised in the analysis of this project, however instead of being sent in bulk during block creation, will instead be sent individually whenever nodes feel like it.

This will then allow for the adaption of these messages into blocks in a future cycle if there is enough time to continue on this path, meaning that in any form this is not a detour of the theorised final project, just a way to create a demo that uses everything that has been created so far.

Usability Features

Receiving messages - Only store valid messages so as to prevent the waste of storage on a user's computer that comes with storing invalid messages.
Logging - Continuous logging should be made while the program operates so that the user can check what is going on with their node by checking the terminal output/logs.

Key Variables

Variable Name

Use

Broadcast_Message_Contents

This object holds a message received or created for broadcasting, it holds all necessary data such as the sender, timestamp, contents, etc. It's useful for ensuring that messages broadcasted across the message are all consistently typed.

Broadcast_Message

This object wraps the Broadcast_Message_Contents object and contains a signature that confirms that the sender did in fact send and approve a message.

Pseudocode

The API endpoint

This is the endpoint at which other nodes will send their own messages to be broadcasted onwards, although it also includes some logic to ensure that the messages received are indeed valid before the node will send them onwards.

// internal imports
IMPORT database
IMPORT cryptography
IMPORT configuration

// external imports
IMPORT json
IMPORT vweb
IMPORT time
IMPORT net.http

//objects
OBJECT Broadcast_Message_Contents {
	sender	
	receiver 
	data	
	time	
}

OBJECT Broadcast_Message {
	message	
	signature
}

EXTENT OBJECT Web_Server:
	// setup the api route as using the POST http method.
	FUNCTION broadcast_route(this) METHOD POST:
		db := this.db
		body := this.req.data
		decoded := {}
	
		TRY:
			decoded = json.decode(Broadcast_Message, body)
		CATCH:
			OUTPUT "[Broadcaster] Message received that cannot be decoded: $body"
			RETURN app.server_error(403)
		END TRY
	
		valid_message = cryptography.verify(decoded.message.sender, json.encode(decoded.message).bytes(), decoded.signature)
	
		IF (valid_message):
			OUTPUT "[Broadcaster] Message received from $decoded.message.sender is valid, checking if seen before..."
			
			// check if message has been recieved before
			parsed_signature = decoded.signature.str()
			parsed_sender = decoded.message.sender.str()
			parsed_receiver = decoded.message.receiver.str()
	
			// check if message has been recieved before
			message_seen_before = db.get_message(parsed_signature, parsed_sender, parsed_receiver, decoded.message.time, decoded.message.data).length > 0
	
			IF (!message_seen_before):
				OUTPUT "[Broadcaster] Have not seen message before.\n[Broadcaster] Saving message to database."
				
				message_db = {
					timestamp: decoded.message.time
					contents: decoded.message.data
					sender: parsed_sender
					receiver: parsed_receiver
					signature: parsed_signature
				}
				
				// save to database/file system/etc
				SAVE message_db
				
				OUTPUT "[Database] Saved message to database."
	
				OUTPUT "\n[Broadcaster] Received message:\n[Broadcaster] Sender: $decoded.message.sender\n[Broadcaster] Sent at: $decoded.message.time\n[Broadcaster] Message: $decoded.message.data\n"
				forward_to_all(db, decoded)
				RETURN this.ok("Message received and forwarded.")
			END IF
	
			OUTPUT "[Broadcaster] Have seen message before."
			RETURN this.ok("Message received but not forwarded.")
	
		ELSE:
			OUTPUT "[Broadcaster] Received an invalid message"
			RETURN this.server_error(403)
		END IF
	
		OUTPUT "[Broadcaster] Shouldn't have reached this part of the code - please report as a bug."
		RETURN app.server_error(403)
	END FUNCTION
END OBJECT EXTEND

Functionality for internal use

These are the functions that will allow the node to handle sending messages internally and these functions will be called by other sections - such as the dashboard page also being developed in this cycle.

FUNCTION forward_to_all(db, msg):
	OUTPUT "[Broadcaster] Sending message to all known nodes."

	// get all known nodes - file/db/etc
	refs = GET ALL node_references

	FOR (ref IN refs):
		// start the send function on a new thread
		GO send(ref.domain, ref.ws, msg)
	END FOR

	OUTPUT "[Broadcaster] Sent message to all known nodes."
END FUNCTION

FUNCTION send(ref string, ws bool, msg Broadcast_Message) bool {
	println("[Broadcaster] Attempting to send message to $ref")
	IF (ws) {
		OUTPUT "[Broadcaster] Websockets are not implemented yet, cannot send message."
		RETURN false
	END IF
	
	raw_response = {}
	
	TRY:
		raw_response = http.post("$ref/broadcast", json.encode(msg))
	CATCH:
		OUTPUT "[Broadcaster] Failed to send a message to $ref, Node is probably offline. Error: $err"
		RETURN false
	END TRY

	IF (raw_response.status_code != 200):
		OUTPUT "[Broadcaster] $ref responded to message with an error. Code: $raw_response.status_code"
		RETURN false
	END IF

	OUTPUT "[Broadcaster] Successfully Sent message to $ref"
	return true
END FUNCTION

FUNCTION broadcast_message(db database.DatabaseConnection, data string){
	send_message(db, data, "".bytes())
END FUNCTION

FUNCTION send_message(db, data, receiver):
	OUTPUT "[Broadcaster] Assembling message with data: $data"
	config = configuration.get_config()
	keys = cryptography.get_keys(config.key_path)

	contents = Broadcast_Message_Contents{
		sender: config.self.key
		receiver: receiver
		time: time.now().str()
		data: data
	}

	message = Broadcast_Message{
		signature: keys.sign(json.encode(contents).bytes())
		message: contents
	}

	OUTPUT "[Database] Saving message to database."
	db_msg = {
		timestamp: contents.time
		sender: contents.sender.str()
		receiver: contents.receiver.str()
		contents: contents.data
		signature: message.signature.str()
	}

	// save to a file/database/etc
	SAVE db_msg
	
	OUTPUT "[Database] Message saved."

	OUTPUT "[Broadcaster] Message assembled, broadcasting to refs..."
	forward_to_all(db, message)
END FUNCTION

Development

An addition that I ended up creating for this cycle that wasn't originally planned but was very useful to test and use the functionality created was a basic html page that was hosted on the http server to allow a user to send and view messages in an easy to use, simple web page.

Paired with all the new broadcasting functionality that allows messages to be shared across the network and the development for this cycle ends up being a lot more substantial than the pseudocode would make it appear, hence the outcome section simply includes two relevant files in their entirety as they were both created during this cycle and both contain relevant code.

The first being the broadcast file that shows all the code written to send messages across the network and forward those that have been received and checked to be valid.

Then the second being the user sided dashboard that helps to provide a nice way to view and contribute to these messages.

Outcome

Due to the majority of the changes in this cycle taking place whilst I was also working on the development of the database addition of the cycle after this one, the code shown below includes references to an early version of the database module but would have the same primary logic if it was using the old referencing style.

The broadcast file

This file is split up into three key sections: the setup; the api endpoints; and the internal functions; this is because although it would be briefer to just show the api endpoints and the internal functions, the setup helps to give more context to those two sections so I included it anyway.

File setup

This shows the setup of the file where various internal and external modules are imported and then then two structs used for message generation are setup for use in the sections below.

module server

// internal imports
import database
import cryptography
import configuration

// external imports
import json
import vweb
import time
import net.http

//structs
struct Broadcast_Message_Contents {
	sender	[]u8
	receiver []u8
	data	string
	time	string
}

struct Broadcast_Message {
	message	Broadcast_Message_Contents
	signature []u8
}

The api endpoint

['/broadcast'; post]
pub fn (mut app App) broadcast_route() vweb.Result {
	db := app.db
	body := app.req.data

	decoded := json.decode(Broadcast_Message, body) or {
		eprintln("[Broadcaster] Message received that cannot be decoded: $body")
		return app.server_error(403)
	}

	valid_message := cryptography.verify(decoded.message.sender, json.encode(decoded.message).bytes(), decoded.signature)

	if valid_message {
		println("[Broadcaster] Message received from $decoded.message.sender is valid, checking if seen before...")
		// check if message has been recieved before
		parsed_signature := decoded.signature.str()
		parsed_sender := decoded.message.sender.str()
		parsed_receiver := decoded.message.receiver.str()

		// check if message has been recieved before
		message_seen_before := db.get_message(parsed_signature, parsed_sender, parsed_receiver, decoded.message.time, decoded.message.data).len > 0

		if !message_seen_before {
			println("[Broadcaster] Have not seen message before.\n[Broadcaster] Saving message to database.")
			
			message_db := database.Message_Table{
				timestamp: decoded.message.time
				contents: decoded.message.data
				sender: parsed_sender
				receiver: parsed_receiver
				signature: parsed_signature
			}

			sql db.connection {
				insert message_db into database.Message_Table
			}
			println("[Database] Saved message to database.")

			println("\n[Broadcaster] Received message:\n[Broadcaster] Sender: $decoded.message.sender\n[Broadcaster] Sent at: $decoded.message.time\n[Broadcaster] Message: $decoded.message.data\n")
			forward_to_all(db, decoded)
			return app.ok("Message received and forwarded.")
		}

		println("[Broadcaster] Have seen message before.")
		return app.ok("Message received but not forwarded.")

	} else {
		eprintln("[Broadcaster] Received an invalid message")
		return app.server_error(403)
	}

	println("[Broadcaster] Shouldn't have reached this part of the code - please report as a bug.")
	return app.server_error(403)
}

Functionality for internal use.

pub fn forward_to_all(db database.DatabaseConnection, msg Broadcast_Message) {
	println("[Broadcaster] Sending message to all known nodes.")

	// get all known nodes
	refs := sql db.connection {
		select from database.Reference_Table
	}

	for ref in refs {
		go send(ref.domain, ref.ws, msg)
	}

	println("[Broadcaster] Sent message to all known nodes.")
}

pub fn send(ref string, ws bool, msg Broadcast_Message) bool {
	println("[Broadcaster] Attempting to send message to $ref")
	if ws {
		eprintln("[Broadcaster] Websockets are not implemented yet, cannot send message.")
		return false
	}

	raw_response := http.post("$ref/broadcast", json.encode(msg)) or {
		eprintln("[Broadcaster] Failed to send a message to $ref, Node is probably offline. Error: $err")
		return false
	}

	if raw_response.status_code != 200 {
		eprintln("[Broadcaster] $ref responded to message with an error. Code: $raw_response.status_code")
		return false
	}

	println("[Broadcaster] Successfully Sent message to $ref")
	return true
}

pub fn broadcast_message(db database.DatabaseConnection, data string){
	send_message(db, data, "".bytes())
}

pub fn send_message(db database.DatabaseConnection, data string, receiver []u8) {
	println("[Broadcaster] Assembling message with data: $data")
	config := configuration.get_config()
	keys := cryptography.get_keys(config.key_path)

	contents := Broadcast_Message_Contents{
		sender: config.self.key
		receiver: receiver
		time: time.now().str()
		data: data
	}

	message := Broadcast_Message{
		signature: keys.sign(json.encode(contents).bytes())
		message: contents
	}

	println("[Database] Saving message to database.")
	db_msg := database.Message_Table{
		timestamp: contents.time
		sender: contents.sender.str()
		receiver: contents.receiver.str()
		contents: contents.data
		signature: message.signature.str()
	}

	sql db.connection {
		insert db_msg into database.Message_Table
	}
	println("[Database] Message saved.")


	println("[Broadcaster] Message assembled, broadcasting to refs...")
	forward_to_all(db, message)
}

The dashboard file

This file houses all the logic and code for the http dashboard that is hosted the same way that the api endpoints are, with a basic token system to allow a node's 'owner' to send messages from anywhere that can access the node's api server

File setup

This just shows the setup for modules and constants needed by other parts of the code and contains no actual logic.

module server

// external modules
import vweb
import crypto.rand
import json
import net.http

// internal modules
import configuration
import utils

// constants
const token_path = "$configuration.base_path/tokens.json"

// structs
struct MessageInfo {
	pub:
		sender string
		timestamp string
		contents string
}

Http endpoints

Both of these endpoints reference http pages to be hosted by the api server, I have decided not to include the html files because they are both quite a lot of lines due to housing html, javascript and css code all within the same file, but the files can be found here.

['/dashboard'; get]
pub fn (mut app App) dashboard_page() vweb.Result {
	if !is_logged_in(app) {
		return app.redirect('/login')
	}

	raw_message_objs := app.db.get_latest_messages(0, 25)
	mut message_objs := []MessageInfo{}

	for msg in raw_message_objs {
		mut sender := ""

		data := json.decode([]u8, msg.sender) or {
			// eprintln("Error decoding JSON of sender: $err")
			sender = msg.sender
			[]u8{}
		}

		for item in data {
			// Big O notation of O(n^2) so not great, but should be a small list
			sender += item.hex()
		}

		message_objs << MessageInfo{
			sender: sender
			timestamp: msg.timestamp
			contents: msg.contents
		}
	}

	return $vweb.html()
}


['/login'; get]
pub fn (mut app App) login_page() vweb.Result {
	if is_logged_in(app) {
		return app.redirect('/dashboard')
	}
	return $vweb.html()
}

Api endpoints

All of the endpoints in this section are accessed by html requests within code and are not meant to be accessed directly by users, and handle the token logic to provide a somewhat secure method of allowing a node's owner to talk to the node over the internet. This is not the most secure way this could've been done but should be fine by now.

['/dashboard/gentoken'; get]
pub fn (mut app App) gentoken_route() vweb.Result {
	config := configuration.get_config()
	// Generate a new token
	token := (rand.int_u64(4294967295) or { return app.server_error(500) }).str()
	cur_tokens := utils.read_file(token_path, true)

	if !cur_tokens.loaded {
		if !utils.save_file(token_path, json.encode([token]), 0) {
			eprintln("[Server] Failed to save token to file.")
		}
	} else {
		mut prev_tokens := json.decode([]string, cur_tokens.data) or {
			eprintln("[Server] Failed to load previous tokens, overwriting...")
			[]string{}
		}
		prev_tokens << token

		if !utils.save_file(token_path, json.encode(prev_tokens), 0) {
			eprintln("[Server] Failed to save token to file.")
		}
	}

	println("\n\n[Server] Generated new token: $token\n[Server] Enter it at http://localhost:$config.port/dashboard to login \n\n")
	
	// Confirm the token has been sent
	return app.ok("ok")
}

['/dashboard/login'; post]
pub fn (mut app App) login_route() vweb.Result {
	data := app.Context.req.data

	prev_tokens_raw := utils.read_file(token_path, true)

	if !prev_tokens_raw.loaded {
		eprintln("[Server] Failed to load token storage.")
		return app.server_error(401)
	}

	prev_tokens := json.decode([]string, prev_tokens_raw.data) or {
		eprintln("[Server] Failed to decode token data.")
		return app.server_error(401)
	}

	if data in prev_tokens {
		println("[Server] Token supplied valid.")
		cookie := http.Cookie{
			name: "token"
			value: data
			max_age: 3600
			secure: false
		}

		app.set_cookie(cookie)
		return app.ok("ok")
	}

	eprintln("[Server] Token supplied not valid.")
	println("[Server] Supplied data $data, tokens available: $prev_tokens")
	return app.server_error(401)
}

['/dashboard/send_message'; post]
pub fn (mut app App) send_message_route() vweb.Result {
	if !is_logged_in(app) {
		return app.server_error(401)
	}

	data := app.Context.req.data
	send_message(app.db, data, []u8{})
	return app.ok("ok")
}

Internal functionality

The only function in this section just allows the various api endpoints to check if a user has a valid login token and responds with a boolean value to tell the requesting function whether or not they are logged in or not.

fn is_logged_in(app App) bool {
	cookie := app.get_cookie('token') or {
			eprintln("[Server] Failed to get cookie. Error: $err")
			return false
		}

	if cookie == '' {
		return false
	}

	prev_tokens_raw := utils.read_file(token_path, true)

	if !prev_tokens_raw.loaded {
		eprintln("[Server] Failed to load token storage.")
		return false
	}

	prev_tokens := json.decode([]string, prev_tokens_raw.data) or {
		eprintln("[Server] Failed to decode token data.")
		return false
	}

	if cookie in prev_tokens {
		println("[Server] Token supplied valid.")
		// now get the node's data and do stuff with it
		return true
	}

	eprintln("[Server] Token supplied not valid.")
	println("[Server] Supplied data $cookie, tokens available: $prev_tokens")
	return false
}

Challenges

One of the key challenges this cycle was to figure out how to give access to the dashboard to the node's owner and not to other users without having to make them send any private data over a network as it is fairly probable that the software will be running without https as it isn't required for any other part of the software.

The method I created to handle this is very simple but should be secure enough for now and simply relies upon the user trying to login having access to the terminal output of the software at login time.

This is because the security method is based upon a basic cookie and token system where the user clicks "get a token" to generate a new token that is then outputted in the software's terminal output, they can then copy this token into the input field to login where it is submitted as a form of password. Assuming this token is correct, the user's browser is then sent a cookie holding this token so that any other request sent by the user contains this token and verifies that they have control of this node.

Testing

Tests

Test

Instructions

What I expect

What actually happens

Passed?

Navigate to 'https://localhost:8000/dashboard'

The dashboard page should redirect to the login page with an option to input a token or generate one.

As Expected

Click the 'generate token' button

A token to be output in the node's terminal output.

As Expected

Enter an invalid token into the input field and click 'submit'

The dashboard should not give the user access.

As Expected

Enter an valid token into the input field and click 'submit'

The dashboard should give the user acess to itself.

As Expected

Type a message and click send.

The node should receive the message from the dashboard and attempt to send it across the network.

As Expected

Connect to and then send a message to another node using the dashboard.

The node should connect to a pre-existing node and then send a message to it after a message is sent from the dashboard.

As Expected

Send a message to the node from another node.

The node on the receipient end of test 6 should receive the same message as was sent from the other node.

As Expected

Previous2.2.11 Cycle 11 - Remembering Nodes Next2.2.13 Cycle 13 - Introducing a sql database

Last updated 2 years ago

Design

Objectives

Usability Features

Key Variables

Pseudocode

The API endpoint

Functionality for internal use

Development

Outcome

The broadcast file

File setup

The api endpoint

Functionality for internal use.

The dashboard file

File setup

Http endpoints

Api endpoints

Internal functionality

Challenges

Testing

Tests

Evidence