content.js

function popup(value)
//generate a popup div for the data
{
    div=document.createElement("div");
    div.style.position="fixed";
    div.style.top="50%";
    div.style.left="50%";
    div.style.height="25%";
    div.style.width="25%";
    div.style.border="1px black rigid";

    close=document.createElement("span");
    close.innerText="X";
    close.addEventListener("click",(event)=>
    {
        event.target.parentElement.remove();
    });
    close.position="relative";
    close.left="99%";
    close.bottom="99%";
    
    text=document.createElement("textarea");
    text.value=value;
    text.style.height="95%";
    text.style.width="100%";

    div.appendChild(close);
    div.appendChild(text);
    document.body.appendChild(div);
}

function pass()
//an html div to input password
{
    return;
}

function errorhandle(err)
//handles all errors
{
    console.error(err);
}

function digest(key,callback) 
//converts ArrayBuffer of any size to 256 bit by hashing SHA256
//generates the cryptoKey object using the 256 bit hashed
//calls the callback that contains the calls to AES encrypt/decrypt
{
    crypto.subtle.digest(
        {
        "name":"SHA-256"
        },
        key).then((hashed)=>
            {
                //make key for AES-GCM
                crypto.subtle.importKey(
                    "raw",
                    hashed,
                    {
                        name:"AES-GCM"
                    },
                    false,
                    ["encrypt","decrypt"]
                ).then(callback);
            });
}

let targetc=null;
let keys="";

document.addEventListener("mousedown", function(event)
//stores which element was clicked last time
{
    //right click
    if(event.button == 2)
    { 
        targetc=event.target;
        targetc.val=(a=0)=>
        {
            //gmail uses editable div, as a fix uses this function
            if(a)
            {
                /*if(targetc.tagName=="DIV")
                    targetc.innerText=a;
                else
                    targetc.value=a;
                */
               popup(a);
            }
            else
            {
                if(targetc.tagName=="DIV")
                    return targetc.innerText;
                else
                    return targetc.value;
            }
        };
    }
}, true);

/*

The main part of the code starts here. By adding an event listener to messages from main.js.
These msgs are commands whether to encrypt or decrypt

*/
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse)
//recieve the msg from main.js telling whether to encrypt/decrypt 
{
    if(request.id=="encrypt")
    {
        keys=prompt("Enter password:");//TODO: make it an htm prompt with input type password
        if(keys=="") //if password input step was cancelled
            return;
        keys=new TextEncoder().encode(keys).buffer; //convert text to ArrayBuffer
        digest(keys,(key)=>
            {
                crypto.subtle.encrypt(
                    {
                        name:"AES-GCM",
                        iv: new Uint8Array([1,2,3,4,5,6,7,8,9,0,11,12]) //SHOUlD be random. but cant be
                    },
                    key,
                    new TextEncoder().encode(targetc.val()).buffer //get data from editable as ArrayBuffer
                ).then((encoded)=>
                {
                    targetc.val(btoa(new Uint8Array(encoded).toString()));//convert the result to array and to base64
                }).catch((err)=>{errorhandle(err)});
            });
    }
    if(request.id=="decrypt")
    {
        keys=prompt("Enter password:");
        if(keys=="")
            return;
        keys=new TextEncoder().encode(keys).buffer;
        digest(keys,(key)=>
            {
                crypto.subtle.decrypt(
                    {
                        name:"AES-GCM",
                        iv: new Uint8Array([1,2,3,4,5,6,7,8,9,0,11,12])
                    },
                    key,
                    new Uint8Array(atob(targetc.val()).split(",").map(Number)) //decode base64, convert to unt8Array
                ).then((encoded)=>
                    {
                        targetc.val(new TextDecoder().decode(encoded)); //decode the output
                    }
                ).catch((err)=>{errorhandle(err)});
            });
    }
});