As SensePost grows, so does our desire to ensure a healthy balance between technical savvy and organisational skills. As a result, we are on the lookout for a Technical Project Manager based in our Pretoria office in South Africa.
Job Title: Technical Project Manager
Salary Range: Industry standard, commensurate with experience
Location: Pretoria, South Africa
About the role
New types of mobile applications based on Trusted Execution Environments (TEE) and most notably ARM TrustZone micro-kernels are emerging which require new types of security assessment tools and techniques. In this blog post we review an example TrustZone application on a Galaxy S3 phone and demonstrate how to capture communication between the Android application and TrustZone OS using an instrumented version of the Mobicore Android library. We also present a security issue in the Mobicore kernel driver that could allow unauthorised communication between low privileged Android processes and Mobicore enabled kernel drivers such as an IPSEC driver.
Mobicore OS :
The Samsung Galaxy S III was the first mobile phone that utilized ARM TrustZone feature to host and run a secure micro-kernel on the application processor. This kernel named Mobicore is isolated from the handset's Android operating system in the CPU design level. Mobicore is a micro-kernel developed by Giesecke & Devrient GmbH (G&D) which uses TrustZone security extension of ARM processors to create a secure program execution and data storage environment which sits next to the rich operating system (Android, Windows , iOS) of the Mobile phone or tablet. The following figure published by G&D demonstrates Mobicore's architecture :
The security critical applications that run inside Mobicore OS are referred to as trustlets and are developed by third-parties such as banks and content providers. The trustlet software development kit includes library files to develop, test and deploy trustlets as well as Android applications that communicate with relevant trustlets via Mobicore API for Android. Trustlets need to be encrypted, digitally signed and then remotely provisioned by G&D on the target mobile phone(s). Mobicore API for Android consists of the following 3 components:
1) Mobicore client library located at /system/lib/libMcClient.so: This is the library file used by Android OS or Dalvik applications to establish communication sessions with trustlets on the secure world
2) Mobicore Daemon located at /system/bin/mcDriverDaemon: This service proxies Mobicore commands and responses between NWd and SWd via Mobicore device driver
3) Mobicore device driver: Registers /dev/mobicore device and performs ARM Secure Monitor Calls (SMC) to switch the context from NWd to SWd
The source code for the above components can be downloaded from Google Code. I enabled the verbose debug messages in the kernel driver and recompiled a Samsung S3 kernel image for the purpose of this analysis. Please note that you need to download the relevant kernel source tree and stock ROM for your S3 phone kernel build number which can be found in "Settings->About device". After compiling the new zImage file, you would need to insert it into a custom ROM and flash your phone. To build the custom ROM I used "Android ROM Kitchen 0.217" which has the option to unpack zImage from the stock ROM, replace it with the newly compiled zImage and pack it again.
1) Android application calls mcOpenDevice() API which cause the Mobicore Daemon (/system/bin/mcDriverDaemon) to open a handle to /dev/mobicore misc device.
2) It then allocates a "Worlds share memory" (WSM) buffer by calling mcMallocWsm() that cause the Mobicore kernel driver to allocate wsm buffer with the requested size and map it to the user space application process. This shared memory buffer would later be used by the android application and trustlet to exchange commands and responses.
3) The mcOpenSession() is called with the UUID of the target trustlet (10 bytes value, for instance : ffffffff000000000003 for PlayReady DRM truslet) and allocate wsm address to establish a session with the target trustlet through the allocated shared memory.
4) Android applications have the option to attach additional memory buffers (up to 6 with maximum size of 1MB each) to the established session by calling mcMap() API. In case of PlayReady DRM trustlet which is used by the Samsung VideoHub application, two additional buffers are attached: one for sending and receiving the parameters and the other for receiving trustlet's text output.
5) The application copies the command and parameter types to the WSM along with the parameter values in second allocated buffer and then calls mcNotify() API to notify the Mobicore that a pending command is waiting in the WSM to be dispatched to the target trustlet.
6) The mcWaitNotification() API is called with the timeout value which blocks until a response received from the trustlet. If the response was not an error, the application can read trustlets' returned data, output text and parameter values from WSM and the two additional mapped buffers.
7) At the end of the session the application calls mcUnMap, mcFreeWsm and mcCloseSession .
The Mobicore kernel driver is the only component in the android operating system that interacts directly with Mobicore OS by use of ARM CPU's SMC instruction and Secure Interrupts . The interrupt number registered by Mobicore kernel driver in Samsung S3 phone is 47 that could be different for other phone or tablet boards. The Mobicore OS uses the same interrupt to notify the kernel driver in android OS when it writes back data.
Analysis of a Mobicore session:
There are currently 5 trustlets pre-loaded on the European S3 phones as listed below:
shell@android:/ # ls /data/app/mcRegistry
The 07010000000000000000000000000000.tlbin is the "Content Management" trustlet which is used by G&D to install/update other trustlets on the target phones. The 00060308060501020000000000000000.tlbin and ffffffff000000000000000000000003.tlbin are DRM related truslets developed by Discretix. I chose to analyze PlayReady DRM trustlet (ffffffff000000000000000000000003.tlbin), as it was used by the Samsung videohub application which is pre-loaded on the European S3 phones.
The videohub application dose not directly communicate with PlayReady trustlet. Instead, the Android DRM manager loads several DRM plugins including libdxdrmframeworkplugin.so which is dependent on libDxDrmServer.so library that makes Mobicore API calls. Both of these libraries are closed source and I had to perform dynamic analysis to monitor communication between libDxDrmServer.so and PlayReady trustlet. For this purpose, I could install API hooks in android DRM manager process (drmserver) and record the parameter values passed to Mobicore user library (/system/lib/libMcClient.so) by setting LD_PRELOAD environment variable in the init.rc script and flash my phone with the new ROM. I found this approach unnecessary, as the source code for Mobicore user library was available and I could add simple instrumentation code to it which saves API calls and related world shared memory buffers to a log file. In order to compile such modified Mobicore library, you would need to the place it under the Android source code tree on a 64 bit machine (Android 4.1.1 requires 64 bit machine to compile) with 30 GB disk space. To save you from this trouble, you can download a copy of my Mobicore user library from here. You need to create the empty log file at /data/local/tmp/log and replace this instrumented library with the original file (DO NOT FORGET TO BACKUP THE ORIGINAL FILE). If you reboot the phone, the Mobicore session between Android's DRM server and PlayReady trustlet will be logged into /data/local/tmp/log. A sample of such session log is shown below:
The content and address of the shared world memory and two additional mapped buffers are recorded in the above file. The command/response format in wsm buffer is very similar to APDU communication in smart card applications and this is not a surprise, as G&D has a long history in smart card technology. The next step is to interpret the command/response data, so that we can manipulate them later and observe the trustlet behavior. The trustlet's output in text format together with inspecting the assembly code of libDxDrmServer.so helped me to figure out the PlayReady trustlet command and response format as follows:
client command (wsm) : 08022000b420030000000001000000002500000028023000300000000500000000000000000000000000b0720000000000000000
client parameters (mapped buffer 1): 8f248d7e3f97ee551b9d3b0504ae535e45e99593efecd6175e15f7bdfd3f5012e603d6459066cc5c602cf3c9bf0f705b
trustlet response (wsm):08022000b420030000000081000000002500000028023000300000000500000000000000000000000000b0720000000000000000
trustltlet text output (mapped buffer 2):
SRVXInvokeCommand command 1000000 hSession=320b4
SRVXInvokeCommand. command = 0x1000000 nParamTypes=0x25
SERVICE_DRM_BBX_SetKeyToOemContext - pPrdyServiceGlobalContext is 32074
SERVICE_DRM_BBX_SetKeyToOemContext iExpectedSize match real size=48
SERVICE_DRM_BBX_SetKeyToOemContext preparing local buffer DxDecryptAsset start - iDatatLen=32, pszInData=0x4ddf4 pszIntegrity=0x4dde4
DxDecryptAsset calling Oem_Aes_SetKey DxDecryptAsset
calling DRM_Aes_CtrProcessData DxDecryptAsset
calling DRM_HMAC_CreateMAC iDatatLen=32 DxDecryptAsset
after calling DRM_HMAC_CreateMAC DxDecryptAsset
By mapping the information disclosed in the trustlet text output to the client command the following format was derived:
08022000 : virtual memory address of the text output buffer in the secure world (little endian format of 0x200208)
b4200300 : PlayReady session ID
00000001: Command ID (0x1000000)
00000000: Error code (0x0 = no error, is set by truslet after mcWaitNotification)
25000000: Parameter type (0x25)
28023000: virtual memory address of the parameters buffer in the secure world (little endian format of 0x300228)
30000000: Parameters length in bytes (0x30, encrypted key length)
05000000: encryption key type (0x5)
The trustlet receives client supplied memory addresses as input data which could be manipulated by an attacker. We'll test this attack later. The captured PlayReady session involved 18 command/response pairs that correspond to the following high level diagram of PlayReady DRM algorithm published by G&D. I couldn't find more detailed specification of the PlayReady DRM on the MSDN or other web sites. But at this stage, I was not interested in the implementation details of the PlayReady schema, as I didn't want to attack the DRM itself, but wanted to find any exploitable issue such as a buffer overflow or memory disclosure in the trustlet.
An attacker would need to know the "sequence number" of an already established netlink connection between a kernel component such as IPSEC and Mobicore driver in order to exploit this vulnerability. This sequence numbers were incremental starting from zero but currently there is no kernel component on the Samsung phone that uses the Mobicore API, thus this issue was not a high risk. We notified the vendor about this issue 6 months ago but haven't received any response regarding the planned fix. The following figures demonstrate exploitation of this issue from an Android unprivileged process :
|0||Memory address of the mapped output buffer in trustlet process (original value=0x08022000)||for values<0x8022000 the fuzzer crashed|
values >0x8022000 no errors
|41||memory address of the parameter mapped buffer in trusltet process (original value=0x28023000)||0x00001000<value<0x28023000 the fuzzer crashed|
value>=00001000 trustlet exits with "parameter refers to secure memory area"
value>0x28023000 no errors
|49||Parameter length (encryption key or certificate file length)||For large numbers the trustlet exits with "malloc() failed" message|
We demonstrated that intercepting and manipulating the worlds share memory (WSM) data can be used to gain better knowledge about the internal workings of Mobicore trustlets. We believe that this method can be combined with the side channel measurements to perform blackbox security assessment of the mobile TEE applications. The context switching and memory sharing between normal and secure world could be subjected to side channel attacks in specific cases and we are focusing our future research on this area.
One of the things we try and get across in our training - is that pen-testing requires out of the box thinking. It's also about solving puzzles and making things work the way you want them to. It's about identifying the small vulnerabilities (which are often easy to spot), and trying to leverage them into something useful. A key process we strive to do at SensePost, when performing these penetration tests, is about having fun.
However, since we're not presenting our HBN Combat course at BlackHat this year, we thought we'd treat people to a nice, mind-boggling challenge prior to BlackHat. Furthermore, instead of opting for the normal crypto or reversing-type challenges which seem to have become the norm, we thought we'd make it an infrastructure challenge for once. In other words, people get to compromise real, live boxen. We've also made it real-world, this is something you might be faced with when performing a infrastructure test.
You've been tasked with performing an infrastructure assessment against ACME Bank. You've fired up your favorite foot printing tool, run through the usual intelligence gathering methodology and noticed they seem to have a minute Internet footprint. So small, in fact, that the only entry point you have is what appears to be a router at 188.8.131.52.
Obtain access to a host on the internal network and put your name on the wall of fame. The first name on the wall wins.
If one takes a quick glimpse at the target, it will be obvious that the person who makes the first break is probably going to be able to control what other people do (with great power comes great responsibility). Also, there is probably a relatively high chance of people inadvertently blocking themselves off from the target. As such, the challenge is going to be reset to "factory default" at 04h00 MT every day.
We've created a very cool SensePost Blackhat USA 2013 t-shirt and this is limited edition to SensePost staff only, but for the person who gets the first name on the wall, we think you deserve your own.
Have fun, happy haxoring, and hope to see you all at BlackHat.
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:
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.
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.
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".
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.
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.
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.
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.
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.
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.
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...
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!
BlackOps you say?
At SensePost we have quite a range of courses in our Hacking by Numbers series. We feel each one has its own special place. I've delivered almost all the courses over the years, but my somewhat biased favourite is our relatively new BlackOps Edition. Myself (Glenn) and Vlad will be presenting this course at BlackHat Vegas in July.
Where Does BlackOps fit in?
Our introductory courses (Cadet and Bootcamp) are meant to establish the hacker mindset - they introduce the student to psychological aspects of an attacker, and build on that to demonstrate real world capability. BlackOps is designed for students who understand the basics of hacking (either from attending Bootcamp/Cadet, or from other experience) and want to acquire deeper knowledge of techniques. We built the course based on our 12 years of experience of performing security assessments.
But really, what's the course about?
This course is aimed at those who've been penetration testing for a while, but still feel a bit lost when they've compromised a host, or network and want to know the best possible approach to take for the next step. All of the labs in this course come from real life assessments, with the final lab being a full-blown social engineering attack against an admin with pivoting, exfiltration and the works. Specifically, we're going to cover the following topics:
1. Introduction to Scripting
A hacker who can automate a task is an efficient and effective attacker.
2. Advanced Targeting
A hacker who can quickly and effectively identify targets is a successful attacker. We'll be looking at non-standard techniques for identifying targets, such as mDNS, IPv6, and even Pastebin.
You may know how to roll a generic metasploit payload, but we'll be looking at some lesser utilised approaches to compromis. From WPAD injection, to rogue routers in IPv6, to good old smbrelay attacks.
4. Privilege Escalation
Following on somewhat succinctly, how do you elevate your privileges after compromising a box? Everyone wants to be root or enterprise admin.
Once you've compromised a lowly developer's test server on the edge of the network, or the receptionist PC, how do you bounce through that box to get to the good stuff, three DMZs deep? We'll show you how.
A good hacker knows that finding the jewels is only half the battle - smuggling them out can be just as hard. We'll look at how we can use non-standard communication channels to exfiltrate data out of a compromised network. Company X has just deployed a really expensive DLP solution, but you really need to get this data out, how do you bypass it?
7. Client Side Attacks
The weakest layer of the OSI stack - the human. Made über popular over the past 18 months, this is Unit 61398 in action.
8. Camouflage (new for Vegas 2013!)
During the infiltration phase of any attack, a hacker will ultimately need to try and execute code on the target system - whether achieved by means of phishing, payload delivery through an exploit or social engineering - running the code on the target system is the ultimate goal of most cyber attacks in the wild. What this means is that an attacker will need to be capable of bypassing any host-based protection software deployed on the target system for successful exploitation.
This module will run you through the techniques, methods and software currently used by the those targeting large corporates to achieve AV immunity in under any circumstances.
Each module of the above modules is followed by a practical lab to allow you to practise your newly acquired skills. The course finishes with a Capture-the-Flag, with a grand prize. Honestly, this final lab is enjoyable and guaranteed to bring a smile on your face whilst doing it.
We're looking forward to sharing out knowledge, experience, and passion for security with you. Please sign up here.
-Glenn & Vlad