Topic: Is Armory vulnerable to USB-Stick viruses like BadBios? (Read 6759 times)

It is obvious that the kind of measure I'm talking about only makes sense if all such locations are enforcing the same security measures. A shielded front door is useless if the window right next to it is wide opened.

You don't need to rewrite the BIOS eeprom. You can stick the payload (or its bootloader) in any of the other NVRAM locations and inject it into the running BIOS during boot when the infected device is brought up.

As long as writing operations to the BIOS' eeprom are dependant on a hard jumper setting, you're going a long way to thwart root kits.

I don't think any software at all would be invulnerable to BIOS-based malware that meets the description of BadBIOS, especially if you assume BIOS-based malware that is specifically aimed at wallets.  This is independent of whether BadBIOS exists as described.

This embedded hardware is much more common and standardized than you might think. Pretty much all PCs use the same USB host chips. And for a given peripheral there's usually only a handful of chips running similar architectures available on the market. The BIOS/EFI firmware has standard extension interfaces that all vendors support and the malware would hook into to load itself.

Of course there's still a lot of engineering work that needs to be done to create such a virus, enough to put it in the category of almost-certainly-state-sponsored. But once it is isolated in the lab, it's a relatively small operation to dissect and re-purpose its various components to an existing bitcoin wallet seeking malware, for example.

For the moment we could probably suggest that this kind of attack, while extremely worrying, is limited to well-funded adversaries targeting very specific people. If this is the case then you are pretty much screwed.

In order for malware to exploit this method of infection in a more general fashion, surely there are some pretty hefty technical obstacles to overcome? How would an adversary target a machine with unknown hardware / unknown bios / unknown OS.

Someone able to do this may equally find a nice way of causing the online Armory to circumvent any air-gap-transmission system (display QR codes / output audio) to exploit a vulnerability in the offline armory.

Of course I would however never ever run Armory on Windows and would definitely prefer a bootable CD/DVD environment  such as https://bitcointalksearch.org/topic/customizable-bitcoin-livedisk-armoryelectrumvanitygen-233453 

I think, you are talking about the controller of the host interface? It can be compromised by a malformed usb frame (while doing its custom processing before passing it to the OS). That's basically, what I've written before. Of course, the malware is then able to do all other kinds of shady things with or without help of the OS and it will execute on the USB controllers internal "CPU" or the main CPU. This includes changing the BIOS and so on. This way of infection is possible, no question. The hack of the PS3 showed this very well.

However, what I've been talking about, is the controller of the pen drive itself, which manages the data flow between the host's controller and the flash-chip itself. As long as this controller is hardwired and cannot be changed by software, the host pc can't be infected with this pen drive by just plugging in and transferring data. I just refuse to accept, that the host's controller can be compromised by a malicious data payload in an usb frame (Note: I really mean the data part of the usb frame, not the header and other protocol-overhead). The host-interface should never care about the data part. And the header cannot be changed, because the flash drives's controller, which creates the frames and puts the data in, is (in this current assumption) hardwired. Of course, as soon as the data gets interpreted in some way, buffer overflows and the like can happen and cause malware to be executed.

Anyways, it's superflous, because the pen drive's controller can be reprogrammed, as I learned now. However, it still has to be seen, if the reprogramming can happen through the USB interface, or only via other ways (SPI and the like), that are not connected to the host pc in normal operation. For some USB flash drives, I'm pretty sure it's possible via USB.


I think, I realized this a long time ago, when the first proof-of-concept trojans, that could hide in the eeprom of a network card, were made public. Of course, this kind of malware can't be detected by antivirus software. However, there are already a lot of other ways to escape antivirus software with conventional, software-only malware. So I think it's rather stupid to rely on av-software alone for important things.

flipperfish, most USB controllers do some processing at that layer. That's why there is a microcontroller, after all. If there is a security hole at that layer, then a specially constructed USB device (like, say, those given out at conferences or the G8 summit) could do a buffer-overflow like attack against the microcontroller itself, before the frame is passed up to the operating system's USB stack. It then flashes the USB controller with its own custom firmware, sticks the virus payload in NVRAM for insertion into the kernel at next boot, and then passes up fixed, normal USB frames to the host OS. What you need to realize is that none of this occurs on the CPU or in main memory, so it's pretty much undetectable with the current generation of commercially available security software. When you flash the USB firmware, what do you think it does? It send commands to... the USB microcrontoller. If the virus is already in the controller, then it is perfectly capable of flashing itself without outside involvement.

And yes, using a new stick doesn't really gain you anything for the reason you mention.

Actually this was exactly my line of thinking. Device gets plugged in, hard-wired USB interface IC exchanges USB frames with host in order to recognize the device. So far no danger, because the hardwired part of the stick can't be changed. If the data in a data carrying frame could trigger an exploit? I don't know, but I suppose not, because the host interface should expect any data within the payload.

However as it turned out, most USB devices, even cheap standard USB sticks, have microcontrollers with "upgradable firmware". I don't know, if it is possible to alter the firmware through the USB interface. But for some USB sticks this must be true, as for example those sticks, who identify themselves as CD drives to the host to make autorun work, can be changed to not do this anymore. However, if the software driving the microcontroller in the stick can be altered, it is also possible for the stick to send some malicous frames, where the whole frame can be used to trigger the exploit in the host interface/driver.


I don't know if it makes sense to use "new" USB sticks. Maybe, if you don't know, where the USB sticks you already posess have been used in the past. But if the online pc is infected, a "new" USB stick doesn't help, because the online pc can infect the stick, when the unsigned transaction is copied to the stick.

Yes, but a whole bunch of USB frames get exchanged when you plug a device in, to identify the device.  As you say, a specially crafted USB frame could trigger a buffer overflow in the USB stack.  (ETA: That's more a risk with a specially designed malicious device - it's less likely a standard USB stick could be made to do this.)

Still, if you're going to dedicate an offline machine to Armory, then I think it's a reasonable precaution to spend a couple of extra bucks to buy a couple of brand new USB sticks and use them exclusively for moving Armory transactions about.  Doesn't completely remove the risk, but is a good way to minimize it.

I suppose there are two ways to view that:

a) transaction fees should not be implicit (and outputs summing to inputs, including fee should be validated downstream); or

b) the signer should state what he is spending (and the downstream should verify it) as you proposed in the above link.

Either solution could be fine.  Kind of frustrating the pace of progress on bitcoin main though one can fully appreciate the risks and resource constraints, but mostly the risks.  It is why I proposed the bitcoin-staging idea.  Now all we have to do is coax Warren Togami (formerly fedora distro founder) into taking the mantle.  He already ventured from litecoin into spinning a bitcoin-OMG release (litecoin latest fork with bitcoin parameters reinstated, to give bitcoin users the advantages of litecoin validated fixes).

Though something like that is less use to armory as armory is itself on the high value end of the bitcoin scale, and people may not use the fedora like variant on high value.

Streamline and practice a system for hard forks?

Stall and dont progress and get undertaken by faster progressing alt-coins?

Move too fast and make a security mistake.

Rock and hard-place.  Hmmm.

Adam

Whoops, totally posted to the wrong thread!  Please ignore this post...

[Post relocated to the correct thread]

Just to be clear, the issue is not the maximum size of a single transaction.  The issue is that in order for the offline computer to verify the transaction fee, you must supply every, full, supporting transaction along with the one to be signed.  The offline computer must see the tx associated with every input, so it can verify the value of each input.  Therefore, if I send you a few dust outputs contained in 100 kB transactions, then you will potentially be moving 0.5 MB of tx.  Even without me doing anything, I"ve had people report issues because they use their offline wallet to collect lots of small payments over time and then end up with 271 inputs at once.  Those are multi-megabyte transactions.  The single QR codes are just not scalable for this, requiring me to develop something that can handle wider bandwidth for those cases, anyway...

Technically, there's a trivial hard-fork solution:  https://bitcointalksearch.org/topic/sighashwithinputvalue-super-lightweight-hw-wallets-and-offline-data-181734 ... but I don't have much hope of it being adopted.  

A good virus program will go a long way in ferreting out any bad code.

I wonder if any of the ASIC designers could produce provably-secure USB controllers.

I've actually been thinking about exactly this for the last few months.

I thought I had something when I found UBS drives with a physical write lock, but that doesn't help when you need to write the unsigned transaction from the online machine to the device, and then sign it on the offline machine and write the signed version on again, which has to be moved to an online machine.

If you could communicate the unsigned transaction through QR codes, assuming the offline machine is not infected, you could write the signed version to the USB, then lock it and move it to the broadcast machine, insuring that nothing jumps to the drive.

The badBIOS analysis is wrong + comments

+

some of the comments here:
http://www.reddit.com/r/netsec/comments/1ppwet/the_badbios_analysis_is_wrong/

drazan's visualBTC android offline wallet uses "animated QR codes" which is consistent with what you said about the practical bandwidth requirements.  https://bitcointalksearch.org/topic/ann-visualbtc-android-based-hardware-offline-wallet-using-animated-qr-codes-210371

The other thing is there's a sanity size cap on a transaction: the bitcoin block size is limited to 1MB for now, and I think its probably the bitcoin developers might have to take countermeasures or non-linear size related fees if people got in the habit of creating individual transactions that use a whole block - that would limits bitcoin to one transaction per 10 minutes.


Maybe there's a market to include a PGP code signing key. and a pre-installed armory client in an armory labeled cheap android tablet with the speaker, microphone, bluetooth, wifi, and USB cables cut.  (Or one that could be made cheaper by not even including that hardware).

Then you could send it via QR video, armory signed software upgrades;)

I think a risk with USB is someone can infect the online wallet via remote internet compromise, infect a USB that gets plugged into it, and from there into the offline wallet.

Adam

I did dig into this a bit more and it seems the controllers of common usb sticks are really not as hardwired as I thought. The spec-sheet of this (http://www.phison.com/english/newProductView.asp?ID=199&SortID=60) rather cheap IC explicitly states "Firmware Upgradable". So my earlier thoughts are probably wrong.

Personally, I think this is an ideal steady-state solution once the offline system is setup.  But you can't use plain QR codes, you'll have to do QR videos.  If you have to move 2 MB to the offline computer and back... you really want those 100 QR codes to be cycled at 13.82 Hz (or any frequency that isn't a multiple of the other device sampling frequency).  Though even then, your arm might get kind of tired holding it up while it acquires all the images.  Meh. 

But there is still the concern about getting the system setup in the first place.  I guess if you have a custom OS image with the camera software pre-installed, you could use the QR thing to move the Armory offline bundle intself onto the system. 

Yeah, we really need to come up with a set of best practices, so people have some kind of guidance...