PGP over Slack using Greasemonkey

SlackPGP.js

// ==UserScript==
// @name        SlackPGP
// @namespace   slack
// @description slackPGP
// @include     https://*.slack.com/messages/*
// @version     1
// @grant       none
// ==/UserScript==


//Evil globals
var publicKey = "0xDEADBEEF";
var privateKey = "";
var peerPublicKey;
var iStartedPGP;
var lastSent;
var myPeerId;

//Monkey patch Slack's message submit.
var submit = TS.view.submit;


function sendPublicKey() {
    $('#message-input').val('handshake:' + publicKey);
    submit();
}

/**
 * Detect the other persons ID
 * I can grab this from data hiding in the direct message channel title
 */
function getPeerId() {
    myPeerId = myPeerId || $('#channel_header_info').find('span.presence').data('member-presence');
    return myPeerId;
    console.log('Peer: ' + myPeerId);

}

/**
 Who sent this message? Me or my peer?
 */
function isFromPeer(senderId) {
    return getPeerId() === senderId;
}

/**
 * Drop in your favorite PGP library here....
 */
function encrypt(message, callback) {
    setTimeout(function () {
        console.log('encrypting with ', peerPublicKey);
        return callback('%' + message + '%');
    }, 0)
}

function decrypt(message, callback) {
    setTimeout(function () {
        console.log('dec using ', privateKey);
        return callback(message.replace(/%/g, ''));
    }, 0)
}


//Detect new message received. There's probably an event to hook into, but I'm lazy :)
$('#msgs_div').on('DOMNodeInserted', function (e) {
    var target = $(e.target);
    if (target.is('ts-message:not(.bot_message):not(.unprocessed)')) {//Ignore non-useful slack messages
        console.log('message received!');
        var container = target.find('.message_body');
        var text = container.html();
        var senderId = target.find('.message_sender').data('member-id');
        console.log(senderId + ':', text);

        if (isFromPeer(senderId)) {

            // Check to see if we're establishing the handshake
            if (text.match('^handshake:')) {
                peerPublicKey = text.split(':')[1];
                console.log('Received Key from peer');
                if (!iStartedPGP) { //If I didn't start, then send them my public key.
                    sendPublicKey();
                }
                console.log('Handshake complete');
                return;
            }

            // Otherwise decrypt the received text, and replace inline
            decrypt(text, function (plainText) {
                container.html(plainText);
            });
        }

        else {
            //Replace my encrypted text with plain, just on this client
            container.html(lastSent)
        }
    }
});


/**
 * Monkey Patch outgoing messages to make sure they're encrypted
 */
TS.view.submit = function () {

    var message = lastSent = $('#message-input').val();

    // Special case to begin an encrypted session.
    if (message === 'pgp') {
        iStartedPGP = true;
        return sendPublicKey();
    }

    encrypt(message, function (encMessage) {
        $('#message-input').val(encMessage);
        submit();
    })
};