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/*
* Webchat WebRTC application
* https://arthurdejong.org/webchat/
*
* Copyright (C) 2020 Arthur de Jong
*
* Released under the GNU General Public License, either version 3, or
* (at your option) any later version.
*/
function generateSalt() {
var numbers = window.crypto.getRandomValues(new Uint8Array(4))
const symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')
return Array.prototype.slice.call(numbers).map(x => symbols[x % 62]).join('')
}
async function getKey(hash) {
var salt = hash.slice(0, 4)
var key = await window.crypto.subtle.importKey(
'jwk',
{
k: hash.slice(4),
alg: 'A128GCM',
ext: true,
key_ops: ['encrypt', 'decrypt'],
kty: 'oct'
},
{name: 'AES-GCM', length: 128},
false, // extractable
['encrypt', 'decrypt']
)
return new Promise(resolve => {
resolve([salt, key])
})
}
async function generateKey() {
const salt = generateSalt()
const key = await window.crypto.subtle.generateKey(
{name: 'AES-GCM', length: 128},
true, // extractable
['encrypt', 'decrypt']
)
const exported = await window.crypto.subtle.exportKey('jwk', key)
return new Promise(resolve => {
resolve([salt, key, salt + exported.k])
})
}
async function encryptMessage(key, msg) {
const iv = window.crypto.getRandomValues(new Uint8Array(12))
const encrypted = await window.crypto.subtle.encrypt(
{name: 'AES-GCM', iv: iv},
key,
new TextEncoder().encode(JSON.stringify(msg))
)
return new Promise(resolve => {
resolve(new Blob([iv, new Uint8Array(encrypted)]))
})
}
async function decryptMessage(key, encrypted) {
const decrypted = await window.crypto.subtle.decrypt(
{name: 'AES-GCM', iv: new Uint8Array(encrypted.slice(0, 12))},
key,
new Uint8Array(encrypted.slice(12))
)
return new Promise(resolve => {
resolve(JSON.parse(new window.TextDecoder().decode(new Uint8Array(decrypted))))
})
}
class Server {
constructor() {
var server = this
// get key from URL
getKey(window.location.hash.slice(1)).then(function ([salt, key]) {
server.salt = salt
server.key = key
server.createSocket()
server.getRTCConfiguration()
}).catch((reason) => {
console.log(reason)
// generate a new key and store it in the URL
generateKey().then(([salt, key, hash]) => {
server.salt = salt
server.key = key
window.location.hash = '#' + hash
server.createSocket()
server.getRTCConfiguration()
})
})
}
/**
* Provide the name of the channel on the server to use for communication.
*/
async getChannel() {
const symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')
const encrypted = await window.crypto.subtle.encrypt(
{name: 'AES-GCM', iv: new Uint8Array(12)},
this.key,
new TextEncoder().encode(this.salt)
)
return new Promise(resolve => {
resolve(Array.prototype.slice.call(new Uint8Array(encrypted), 0, 16).map(x => symbols[x % 62]).join(''))
})
}
/**
* Get the RTCConfiguration that can be used for peer connections.
*/
getRTCConfiguration() {
const server = this
$.getJSON('RTCConfiguration.json')
.done(function (json) {
server.RTCConfiguration = json
server.setupHandlers()
})
.fail(function (jqxhr, textStatus, error) {
console.log('Request Failed: ' + error)
server.RTCConfiguration = {iceServers: [{urls: 'stun:stun.l.google.com:19302'}]}
server.setupHandlers()
})
}
/**
* Set up a websocket connection.
*/
createSocket() {
const server = this
this.getChannel().then(channel => {
const url = `wss://${window.location.hostname}:${window.location.port}${window.location.pathname}channel/${channel}`
const socket = new WebSocket(url)
socket.addEventListener('open', function (event) {
server.socket = socket
server.setupHandlers()
})
})
}
sendMessage(msg) {
encryptMessage(this.key, msg).then((encrypted) => {
this.socket.send(encrypted, {type: 'application/octet-stream'})
})
}
onMessage(handler) {
this.messageHandler = handler
this.setupHandlers()
}
ready(handler) {
this.readyHandler = handler
this.setupHandlers()
}
setupHandlers() {
// ensure the message handler is registered with the socket
if (this.socket && this.messageHandler) {
const messageHandler = this.messageHandler
this.messageHandler = undefined
const key = this.key
this.socket.onmessage = function (event) {
const reader = new FileReader()
reader.addEventListener('loadend', (e) => {
decryptMessage(key, e.srcElement.result).then((msg) => {
messageHandler(msg)
})
})
reader.readAsArrayBuffer(event.data)
}
}
// ensure the ready handler is called once
if (this.socket && this.RTCConfiguration && this.readyHandler) {
const readyHandler = this.readyHandler
this.readyHandler = undefined
readyHandler(this)
}
}
}
module.exports = Server
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