This Week In Security: It’s Con Season

August 11, 2023 by Jonathan Bennett 8 Comments

It must be Blackhat/DEFCON season. Up first in the storm of named vulnerabilities, we have Downfall. The PDF has the juicy details here. It’s quite similar to the Zenbleed issue from last week, in that it abuses speculative execution to leak data via a hidden register. Unlike Zenbleed, this isn’t direct access, but using cache timing analysis to extract individual bytes using a FLUSH+RELOAD approach.

The key to the vulnerability is the gather instruction, which pulls data from multiple locations in memory, often used to run a followup instruction on multiple bytes of data at once. The gather instruction is complex, takes multiple clock cycles to execute, and uses several tricks to execute faster, including managing buffers to avoid multiple reads. In certain cases, that instruction can be interrupted before it completes, leaving the data in the cache. And this data can be speculatively accessed and the values leaked through timing analysis.

This flaw affects 6th generation Intel Core processors through 11th. Mitigations are already rolling out via a microcode update, but do carry a performance hit for gather instructions. Continue reading “This Week In Security: It’s Con Season” →

Starlink Ground Stations Successfully Hacked

August 14, 2022 by Elliot Williams 18 Comments

Belgian security researcher [Lennert Wouters] has gotten his own code running on the Starlink “Dishy McFlatface” satellite terminals, and you can too! The hack in question is a “modchip” with an RP2040 and a MOSFET that crowbars the power rails, browning out the main CPU exactly when it’s verifying the firmware’s validity and bypassing that protection entirely. [Lennert] had previously figured out how to dump the Starlink firmware straight from the eMMC, and with the ability to upload it back, the circle of pwnership is closed. This was a talk at DEFCON, and you can check out the slides here. (PDF)

The mod chip itself was a sweet piece of work, being tailored to fit into the Starlink’s motherboard just so, and taking good advantage of the RP2040’s PIOs, which are probably the microcontroller’s superpower.

[Lennert] says he submitted his glitch attack to Starlink and they took some precautions to make the glitching harder. In particular, [Lennert] was triggering his timing off of the USART port coming up on the Starlink unit, so Starlink just shut that down. But it’s not like he couldn’t trigger on some other timing-relevant digital signal, so he chose the eMMC’s D0 data line: they’re not going to be able to boot up without it, so this hack is probably final. No shade against Starlink here. It’s almost impossible to shield a device against an attacker who has it on their bench, and [Lennert] concludes that he found no low-hanging fruit and was impressed that he had to work so hard to get root.

What can you do with this? Not much, yet. But in principle, it could be used to explore the security of the rest of the Starlink network. As reported in Wired, Starlink says that they’ve got a defence-in-depth system and that just getting into the network doesn’t really get you very far. We’ll see!

Thanks [jef] for the tip!

Great Badge Concept: A “Geiger Counter” For WiFi Deauthentication Frames

June 20, 2020 by Donald Papp 15 Comments

[Nick Price] had a wonderful concept for a DEFCON badge: a device that worked a lot like a directional Geiger counter, but chirped at detecting WiFi deauthentication packets instead of radiation. That’s a wild idea and it somehow slipped past us last year. Why detect such a thing? Well, the WiFi deauth attack is a kind of invisible toxicity, effectively jamming wireless communications by forcing users to be constantly tied up with authentication, and this device would detect it.

A few things were harder than expected, however. To make the device directional, [Nick] designed and built a PCB Yagi antenna but it wasn’t practical. Not only was it far too big, it would also have required going to four layers on a PCB that was already expensive. The solution he settled on — inspired by a friend’s joke about just dropping the badge into a Pringles can — was to surround the PCB omni antenna with a copper pipe end cap from the plumbing section of any hardware store. [Nick] figured that soldering that to the ground plane should result in a simple, cheap, and attractive directional antenna mod. Did it work? We’ll all have to wait and see.

Sadly, [Nick] wasn’t able to finish in time for last year’s DEFCON. Hardware revisions mounted, and fabrication times for his specialized PCB were longer than usual. Worse news is that this year’s is cancelled, or rather is going virtual, which means he’s going to have to deauth himself. The good news is that now he’s got another 12-month extension. Watch the brief video of the functional prototype, embedded below.

Continue reading “Great Badge Concept: A “Geiger Counter” For WiFi Deauthentication Frames” →

Developing Retro Games For Conference Badges With Kate Morris

February 26, 2020 by Lewin Day No comments

PCB badges have exploded in popularity in recent years. Starting out as a fun token of entry to a conference, they’re now being developed by all manner of independent groups, with DEFCON serving as the heart of the #badgelife movement. After DEFCON 26, Kate Morris and associates decided to undertake the development of their own badge, to celebrate the 50th anniversary of the Apollo landing. Kate’s talk at the 2019 Hackaday Superconference serves to tell the tale of creating a retro game to run on a badge platform.

Continue reading “Developing Retro Games For Conference Badges With Kate Morris” →

Reverse-Engineering Xiaomi IoT Firmware

October 24, 2019 by Sharon Lin 13 Comments

IoT devices rarely ever just do what they’re advertised. They’ll almost always take up more space than they need to – on top of that, their processor and memory alone should be enough to run a multitude of other tasks while not necessarily compromising the task they were built to do.

That’s partially the motivation for rooting any device, but for Xiaomi devices, it’s a bit more fun – that is to say, it’s a little bit harder when you’re reverse engineering its firmware from scratch.

Similar to his other DEF CON 26 talk on modifying ARM Cortex-M firmware, [Dennis Giese] returns with a walkthrough of how to reverse-engineer Xiaomi IoT devices. He starts off talking about the Xiaomi ecosystem and the drawbacks of reusing firmware across all the different devices connected to the same cloud network before jumping into the walkthrough for accessing the devices.

Continue reading “Reverse-Engineering Xiaomi IoT Firmware” →

Customizing Xiaomi ARM Cortex-M Firmware

October 19, 2019 by Sharon Lin 2 Comments

This hack was revealed a while ago at DEFCON26, but it’s still a fascinating look into vulnerabilities that affect some of the most widely used IoT devices.

[Dennis Giese] figured out a way to modify ARM Cortex-M based firmware for use in customizing the functionality of devices or removing access to the vendor. Obviously, there are more malicious activities that can be done with this type of hack, as with any exploits of firmware, but they are (also) obviously not condoned.

The talk goes into the structure of Xiaomi ecosystem and products before going into a step-by-step approach to binary patching the firmware. The first step was to acquire the firmware, either by dumping SPI flash memory (using JTAG, SWD, or desoldered Flash pins) or intercepting traffic during a firmware update and downloading the firmware. There’s also a possibility of downloading the firmware using a URL, although this can be more difficult to find.

The firmware can then be parsed, which first requires the format to be converted from a proprietary format to and ELF file. This conversion makes it easier to load into IDA pro, and gives information on the segments of the firmware and its entry point. Python tools luckily exist for converting binary files to ELF, which simplifies the task.

After loading the ELF file into the disassembler, you’ll want to find the key memory area, denoted by “TAG_MAC”, “TAG_DID”, and “TAG_KEY” in the example firmware (for storing the MAC address, device ID, and key). In order to prepare the firmware for Nexmon – a software that supported C-based firmware binary patching for ARM Cortex-A and ARM Cortex-M binaries – you’ll need to partition some space in the memory for patches and know the function names and signatures for the firmware.

The latter is done by doing a difference comparison in the disassembler between an unknown executable and the example executable.

With the necessary information gathered, you can now use Nexmon to make your modifications. The fact that this can be done for smart devices at home means that smart devices you acquire – especially those partitioned by others – may contain malicious code, so take care when handling used devices.

Continue reading “Customizing Xiaomi ARM Cortex-M Firmware” →

Faxsploit – Exploiting A Fax With A Picture

May 4, 2019 by Pedro Umbelino 26 Comments

Security researchers have found a way to remotely execute code on a fax machine by sending a specially crafted document to it. So… who cares about fax? Well apparently a lot of persons are still using it in many institutions, governments and industries, including the healthcare industry, legal, banking and commercial. Bureaucracy and old procedures tend to die hard.

This is one of those exploits that deserve proper attention, for many reasons. It is well documented and is a great piece of proper old school hacking and reverse engineering. [Eyal Itkin], [Yannay Livneh] and [Yaniv Balmas] show us their process in a nicely done article that you can read here. If you are into security hacks, it’s really worth reading and also worth watching the DEFCON video. They focused their attention in a all-in-one printer/scanner/fax and the results were as good as it gets.

Our research set out to ask what would happen if an attacker, with merely a phone line at his disposal and equipped with nothing more than his target`s fax number, was able to attack an all-in-one printer by sending a malicious fax to it.

In fact, we found several critical vulnerabilities in all-in-one printers which allowed us to ‘faxploit’ the all-in-one printer and take complete control over it by sending a maliciously crafted fax.

As the researchers note, once an all-in-one printer has been compromised, it could be used to a wide array of malicious activity, from infiltrating the internal network, to stealing printed documents even to mining Bitcoin. In theory they could even produce a fax worm, replicating via the phone line.

The attack summary video is bellow, demonstrating an exploit that allows an attacker to pivot into an internal network and taking over a Windows machine using Eternal Blue NSA exploit.

Continue reading “Faxsploit – Exploiting A Fax With A Picture” →