detect when challenge window is closed for Google recaptcha - javascript

I am using Google invisible recaptcha. Is there a way to detect when the challenge window is closed? By challenge window I mean window where you have to pick some images for verification.
I currently put a spinner on the button that rendered the recaptcha challenge, once the button is clicked. There is no way for the user to be prompted with another challenge window.
I am calling render function programmatically:
grecaptcha.render(htmlElement, { callback: this.verified, expiredCallback: this.resetRecaptcha, sitekey: this.siteKey, theme: "light", size: "invisible" });
I have 2 callback functions wired up the verified and the resetRecaptcha functions which look like:
function resetRecaptcha() {
grecaptcha.reset();
}
function verified(recaptchaResponse)
{
/*
which calls the server to validate
*/
}
I would have expected that grecaptcha.render has another callback that is called when the challenge screen is closed without the user verifying himself by selecting the images.

As you mention, the API doesn't support this feature.
However, you can add this feature yourself. You may use the following code with caution, Google might change its reCaptcha and by doing so break this custom code. The solution relies on two characteristics of reCaptcha, so if the code doesn't work, look there first:
the window iframe src: contains "google.com/recaptcha/api2/bframe"
the CSS opacity property: changed to 0 when the window is closed
// to begin: we listen to the click on our submit button
// where the invisible reCaptcha has been attachtted to
// when clicked the first time, we setup the close listener
recaptchaButton.addEventListener('click', function(){
if(!window.recaptchaCloseListener) initListener()
})
function initListener() {
// set a global to tell that we are listening
window.recaptchaCloseListener = true
// find the open reCaptcha window
HTMLCollection.prototype.find = Array.prototype.find
var recaptchaWindow = document
.getElementsByTagName('iframe')
.find(x=>x.src.includes('google.com/recaptcha/api2/bframe'))
.parentNode.parentNode
// and now we are listening on CSS changes on it
// when the opacity has been changed to 0 we know that
// the window has been closed
new MutationObserver(x => recaptchaWindow.style.opacity == 0 && onClose())
.observe(recaptchaWindow, { attributes: true, attributeFilter: ['style'] })
}
// now do something with this information
function onClose() {
console.log('recaptcha window has been closed')
}

As I mentioned in the comments of the answer submitted by #arcs, it is a good solution which works but it also fires onClose() when the user successfully completes the challenge. My solution is to change the onClose() function like so:
// now do something with this information
function onClose() {
if(!grecaptcha.getResponse()) {
console.log('recaptcha window has been closed')
}
}
This way, it only executes the desired code if the challenge has been closed and it has not been completed by the user, thus the response cannot be returned with grecaptcha.getResponse()

The drawback of detecting when iframe was hidden is that it fires not only when user closes captcha by clicking in background, but also when he submits the answer.
What I needed is detect only the first situation (cancel captcha).
I created a dom observer to detect when captcha is attached to DOM, then I disconnect it (because it is no longer needed) and add click handler to its background element.
Keep in mind that this solution is sensitive to any changes in DOM structure, so if google decides to change it for whatever reason, it may break.
Also remember to cleanup the observers/listeners, in my case (react) I do it in cleanup function of useEffect.
const captchaBackgroundClickHandler = () => {
...do whatever you need on captcha cancel
};
const domObserver = new MutationObserver(() => {
const iframe = document.querySelector("iframe[src^=\"https://www.google.com/recaptcha\"][src*=\"bframe\"]");
if (iframe) {
domObserver.disconnect();
captchaBackground = iframe.parentNode?.parentNode?.firstChild;
captchaBackground?.addEventListener("click", captchaBackgroundClickHandler);
}
});
domObserver.observe(document.documentElement || document.body, { childList: true, subtree: true });

To work in IE this solution needs polyfills for .include() and Array.from(), found below:
Array.from on the Internet Explorer
ie does not support 'includes' method
And the updated code:
function initListener() {
// set a global to tell that we are listening
window.recaptchaCloseListener = true
// find the open reCaptcha window
var frames = Array.from(document.getElementsByTagName('iframe'));
var recaptchaWindow;
frames.forEach(function(x){
if (x.src.includes('google.com/recaptcha/api2/bframe') ){
recaptchaWindow = x.parentNode.parentNode;
};
});
// and now we are listening on CSS changes on it
// when the opacity has been changed to 0 we know that
// the window has been closed
new MutationObserver(function(){
recaptchaWindow.style.opacity == 0 && onClose();
})
.observe(recaptchaWindow, { attributes: true, attributeFilter: ['style'] })
}

My solution:
let removeRecaptchaOverlayEventListener = null
const reassignGRecatchaExecute = () => {
if (!window.grecaptcha || !window.grecaptcha.execute) {
return
}
/* save original grecaptcha.execute */
const originalExecute = window.grecaptcha.execute
window.grecaptcha.execute = (...params) => {
try {
/* find challenge iframe */
const recaptchaIframe = [...document.body.getElementsByTagName('iframe')].find(el => el.src.match('https://www.google.com/recaptcha/api2/bframe'))
const recaptchaOverlay = recaptchaIframe.parentElement.parentElement.firstElementChild
/* detect when the recaptcha challenge window is closed and reset captcha */
!removeRecaptchaOverlayEventListener && recaptchaOverlay.addEventListener('click', window.grecaptcha.reset)
/* save remove event listener for click event */
removeRecaptchaOverlayEventListener = () => recaptchaOverlay.removeEventListener('click', window.grecaptcha.reset)
} catch (error) {
console.error(error)
} finally {
originalExecute(...params)
}
}
}
Call this function after you run window.grecaptcha.render() and before window.grecaptcha.execute()
And don't forget to remove event listener: removeRecaptchaOverlayEventListener()

For everybody that didn't quite get how it all works, here is another example with explanations that you might find useful:
So we have 2 challenges here.
1) Detect when the challenge is shown and get the overlay div of the challenge
function detectWhenReCaptchaChallengeIsShown() {
return new Promise(function(resolve) {
const targetElement = document.body;
const observerConfig = {
childList: true,
attributes: false,
attributeOldValue: false,
characterData: false,
characterDataOldValue: false,
subtree: false
};
function DOMChangeCallbackFunction(mutationRecords) {
mutationRecords.forEach((mutationRecord) => {
if (mutationRecord.addedNodes.length) {
var reCaptchaParentContainer = mutationRecord.addedNodes[0];
var reCaptchaIframe = reCaptchaParentContainer.querySelectorAll('iframe[title*="recaptcha"]');
if (reCaptchaIframe.length) {
var reCaptchaChallengeOverlayDiv = reCaptchaParentContainer.firstChild;
if (reCaptchaChallengeOverlayDiv.length) {
reCaptchaObserver.disconnect();
resolve(reCaptchaChallengeOverlayDiv);
}
}
}
});
}
const reCaptchaObserver = new MutationObserver(DOMChangeCallbackFunction);
reCaptchaObserver.observe(targetElement, observerConfig);
});
}
First, we created a target element that we would observe for Google iframe appearance. We targeted document.body as an iframe will be appended to it:
const targetElement = document.body;
Then we created a config object for MutationObserver. Here we might specify what exactly we track in DOM changes. Please note that all values are 'false' by default so we could only leave 'childList' - which means that we would observe only the child node changes for the target element - document.body in our case:
const observerConfig = {
childList: true,
attributes: false,
attributeOldValue: false,
characterData: false,
characterDataOldValue: false,
subtree: false
};
Then we created a function that would be invoked when an observer detects a specific type of DOM change that we specified in config object. The first argument represents an array of Mutation Observer objects. We grabbed the overlay div and returned in with Promise.
function DOMChangeCallbackFunction(mutationRecords) {
mutationRecords.forEach((mutationRecord) => {
if (mutationRecord.addedNodes.length) { //check only when notes were added to DOM
var reCaptchaParentContainer = mutationRecord.addedNodes[0];
var reCaptchaIframe = reCaptchaParentContainer.querySelectorAll('iframe[title*="recaptcha"]');
if (reCaptchaIframe.length) { // Google reCaptcha iframe was loaded
var reCaptchaChallengeOverlayDiv = reCaptchaParentContainer.firstChild;
if (reCaptchaChallengeOverlayDiv.length) {
reCaptchaObserver.disconnect(); // We don't want to observe more DOM changes for better performance
resolve(reCaptchaChallengeOverlayDiv); // Returning the overlay div to detect close events
}
}
}
});
}
Lastly we instantiated an observer itself and started observing DOM changes:
const reCaptchaObserver = new MutationObserver(DOMChangeCallbackFunction);
reCaptchaObserver.observe(targetElement, observerConfig);
2) Second challenge is the main question of that post - how do we detect that the challenge is closed? Well, we need help of MutationObserver again.
detectReCaptchaChallengeAppearance().then(function (reCaptchaChallengeOverlayDiv) {
var reCaptchaChallengeClosureObserver = new MutationObserver(function () {
if ((reCaptchaChallengeOverlayDiv.style.visibility === 'hidden') && !grecaptcha.getResponse()) {
// TADA!! Do something here as the challenge was either closed by hitting outside of an overlay div OR by pressing ESC key
reCaptchaChallengeClosureObserver.disconnect();
}
});
reCaptchaChallengeClosureObserver.observe(reCaptchaChallengeOverlayDiv, {
attributes: true,
attributeFilter: ['style']
});
});
So what we did is we get the Google reCaptcha challenge overlay div with the Promise we created in Step1 and then we subscribed for "style" changes on overlay div. This is because when the challenge is closed - Google fade it out.
It's important to note that the visibility will be also hidden when a person solves the captcha successfully. That is why we added !grecaptcha.getResponse() check. It will return nothing unless the challenge is resolved.
This is pretty much it - I hope that helps :)

Related

Chrome Extension And Dom Capture

I created a chrome extension for one of my pages. I'm getting the data in a dom element on the page and querying the api and calling it back. On the site where I get data, the page does not reload when switching between pages. So I can't catch Dom loading or locationchange in foreground.js because the page is not refreshed and i solve my problem by timeout.The dom in foreground.js is only triggered when the page is refreshed. The codes I wrote in settimeout are triggered when switching between pages. How can i solve this problem without timeout?
background.js CODES
chrome.tabs.onUpdated.addListener((tabId, changeInfo,tab) => {
if(changeInfo.status == "complete" && tab.status == "complete") {
chrome.scripting.executeScript({
target: {tabId: tabId},
files: ["./foreground.js"]
})
}
});
foreground.js CODES
document.addEventListener("DOMContentLoaded", () => { alert('Dom'); }); //not working
window.addEventListener('locationchange', function(){
console.log('location changed!');
}) //not working
setTimeout(() => {
let find = document.querySelector(".contentsdetailscontainer").textContent;
},1000); //this is working
foreground.js executed when document.readyState is complete, which means DOMContentLoaded has already been fired.
If at that point the needed element is not present in the DOM, you can use the Mutation Observer and wait for it.
Here is a simple example (very inefficient because it observes entire body, if only a specific element changes, you should observe it instead, so use it only as a guide):
var nodeFound = false;
const observer = new MutationObserver(() =>
{
const node = document.querySelector(".contentsdetailscontainer");
if (node && node.textContent)
{
if (!nodeFound)
{
//only show alert once per new page.
alert("node found");
nodeFound = true;
}
}
else
{
nodeFound = false; //reset in case page updated again
}
});
observer.observe(document.body, {subtree: true, childList: true});

Using MutationObserver to wait for button to appear

I am trying to create something that automatically clicks the required buttons on stackexchange type sites so that I can stop doing it myself. I am using a content script. I am trying to:
Find the button to customize cookies
click accept (they're usually all deselected with stackexchange sites)
Here is my code so far. I think it finds the right node, but clicks it too soon? I am not entirely sure since I'm new to js and whatnot.
function AcceptCustomization() {
let myNode;
let observer = new MutationObserver((mutations) => {
mutations.forEach((mutation) => {
if (!mutation.addedNodes) return
for (let i = 0; i < mutation.addedNodes.length; i++) {
// do things to your newly added nodes here
let node = mutation.addedNodes[i]
if (node.nodeType === 1) {
node
var a = node.getElementsByClassName("flex--item s-btn s-btn__primary save-preference-btn-handler onetrust-close-btn-handler js-consent-banner-hide js-consent-save")[0]
if (a) {
myNode = a
console.log(myNode)
console.log(myNode.click())
}
}
}
})
})
observer.observe(document.body, {
childList: true
, subtree: true
, attributes: false
, characterData: false
})
}
function CustomizeCookies() {
var a = document.getElementsByClassName("flex--item s-btn s-btn__filled js-cookie-settings")[0];
if (a) {
a.click();
AcceptCustomization();
}
else {
console.log(a);
}
}
CustomizeCookies();
In the future, I want to create an extension that I can use to create a sort of database of websites with corresponding button clicks. For example, if I don't have the cookie customization for a website, I would click the extension and run a script that captures my button clicks and redoes them every future time I visit (if it is not the same session).
Thanks :)

When to disconnect MutationObserver in Chrome / Web Extension?

I want to know when or if I need to disconnect a MutationObserver in my content script to avoid memory leaks.
So my content script checks all new additions to the DOM and updates the HTML accordingly. I use a MutationObserver for this which is created and started at in the content script.
My question is, does the MutationObserver destroy itself when a new page is loaded or must I listen to page changes to disconnect it and destroy it myself each time.
Here is the relevant code:
function startObserver(textSize: number, lineHeight: number, font: string = "Droid Arabic Naskh") {
let config: MutationObserverInit = {
attributes: false,
childList: true,
subtree: true,
characterData: true,
characterDataOldValue: false,
};
let callback: MutationCallback = (mutationsList: MutationRecord[]) => {
mutationsList.forEach((record: MutationRecord) => {
// If something has been added
if (record.addedNodes.length > 0) {
// For each added node
record.addedNodes.forEach((addedNode: Node) => {
// For each node with Arabic script in addedNode
getArabicTextNodesIn(addedNode).forEach((arabicNode: Node) => {
// Update arabicNode only if it hasn't been updated
if (arabicNode.parentElement && arabicNode.parentElement.getAttribute("class") != "ar") {
updateNode(arabicNode, textSize, lineHeight, font);
}
});
});
}
});
};
if (!observer) {
observer = new MutationObserver(callback);
observer.observe(document.body, config);
}
}
Found it out a long time ago thanks to #xOxxm and some personal testing and playing around but answering myself in case someone else needs this in the future
Does the MutationObserver destroy itself when a new page is loaded or must I listen to page changes to disconnect it and destroy it myself each time?
Yes the MutationObserver destroys itself upon leaving the page (the document has changed) so the above code was in fact safe and devoid of any possible memory leaks.

How to stop a new node being added to DOM using Chrome/Firefox extension?

I am writing an extension to detect some malicious behavior of some scripts. These scripts add some nodes into the DOM after page gets loaded. I am able to get these nodes using
document.addEventListener("DOMNodeInserted", checkContents, false);
But how can I stop them from being loaded? Can this be done in Chrome or Firefox?
Use MutationObserver with childList and subtree.
var grid = iframe.contentDocument.getElementById('newtab-grid');
var mobs = new iframe.contentWindow.MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
console.log(mutation.type, mutation);
if (mutation.addedNodes && mutation.addedNodes.length > 0) {
var link = mutation.target.querySelector('.newtab-link');
if (link) {
link.setAttribute('target', '_parent');
console.log('set target on this el')
} else {
console.log('this ell has no link BUT it was an added el')
}
}
});
});
mobs.observe(grid, {
childList: !0,
subtree: !0
});
now this will tell you when its addingNodes and it gives you what was added in mutation.addedNodes. you can iterate throuh that and remove what was added. I'm not sure if you can prevent it from adding, but you can definitely remove it after it was added.
https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver?redirectlocale=en-US&redirectslug=DOM%2FMutationObserver#MutationObserverInit

Capture (screenshot) of inactive tab

Would like to capture image of possibly inactive tab.
Problem is that when using the approach displayed here the tab often does not get time to load before capture is done, resulting in failure.
The chrome.tabs.update() call-back is executed before the tab can be captured.
I have also tried to add listeners to events like tabs.onActivated and tabs.onHighlighted and doing the capture when those are fired, but the result is the same. And, as a given by that, I have also tried highlighted instead of active on chrome.tabs.update() – and combination of both; with listeners and call-backs.
The only way to make it work partially better is by using setTimeout() , but that is very hackish, not reliable and ugly. The fact one have to activate a tab before capture is somewhat noisy – but if one have to add delays the issue becomes somewhat worse.
This is more like a convenience feature for my extension, but would be nice to make it work.
/* Not the real code, but the same logic. */
var request_tab = 25,
request_win = 123
old_tab;
/* Check which tab is active in requested window. */
chrome.tabs.query({
active : true,
windowId : request_win
}, function (re) {
old_tab = re[0].id;
if (old_tab !== request_tab) {
/* Requested tab is inactive. */
/* Activate requested tab. */
chrome.tabs.update(request_tab, {
active: true
}, function () {
/* Request capture */ /* CB TOO SOON! */
chrome.tabs.captureVisibleTab(request_window, {
format : 'png'
}, function (data) {
/* ... data ... */
/* Put back old tab */
chrome.tabs.update(old_tab, {
active: true
});
})
});
} else {
/* Requested tab is active. */
/* Request capture. */
chrome.tabs.captureVisibleTab(request_window, {
format : 'png'
}, function (data) {
/* ... data ... */
})
}
});
Since that you are updating the tab using the chrome.tabs.update() method, the callback will be called as soon as the tab properties are changed, but, obviously, before the page is loaded. To work around this you should remember that the tab isn't yet ready and, using the chrome.tabs.onUpdated event, check when it's ready and you can use chrome.tabs.captureVisibleTab().
Here is the solution:
var request_tab = 25,
request_win = 123,
waiting = false,
// ^^^ Variable used to check if tab has loaded
old_tab;
// Check which tab is active in requested window.
chrome.tabs.query({
active : true,
windowId : request_win
}, function (re) {
old_tab = re[0].id;
if (old_tab !== request_tab) {
// Requested tab is inactive
// Activate requested tab
chrome.tabs.update(request_tab, { active: true });
// Tab isn't ready, you can't capture yet
// Set waiting = true and wait...
waiting = true;
} else {
// Requested tab is active
// Request capture
chrome.tabs.captureVisibleTab(request_window, {
format : 'png'
}, function (data) {
// Elaborate data...
})
}
});
chrome.tabs.onUpdated.addListener(function(tabID, info, tab) {
// If the tab wasn't ready (waiting is true)
// Then check if it's now ready and, if so, capture
if (waiting && tab.status == "complete" && tab.id == request_tab) {
// Now you can capture the tab
chrome.tabs.captureVisibleTab(request_window, {
format : 'png'
}, function (data) {
// Elaborate data...
// Put back old tab
// And set waiting back to false
chrome.tabs.update(old_tab, { active: true });
waiting = false;
});
}
});

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