5 ms·

This seems a bit misleading to me. From README.md: This project aims to be useful when you get/find a USB key that you can't trust, and you want to look at

This seems a bit misleading to me. From README.md: This project aims to be useful when you get/find a USB key that you can't trust, and you want to look at its contents without taking the risk of plugging it into your computer directly. Its method of operation is given as: The content of the untrusted key will be copied or/and converted to the second (blank) key following these rules (based on the mime type as determined by libmagic) This process does not make the key trustworthy. From the BadUSB intro: Once reprogrammed, benign devices can turn malicious in many ways, including: 1. A device can emulate a keyboard and issue commands on behalf of the logged-in user [...] 2. A modified thumb drive or external hard disk can [...] boot a small virus, which infects the computer’s operating system prior to boot. Assuming that the first USB stick can infect the second USB stick, CIRClean will not protect you against these attacks.

leni536 10y ago
They can mitigate against badUSB by only whitelisting the generic USB mass storage class driver. No keyboard, no mouse, etc... I am not confident they do this though.
- A1kmm 10y ago
  Looks like they don't, but they turn off usbhid on that particular port: https://github.com/CIRCL/Circlean/blob/master/circlean_fs/root_partition/etc/udev/rules.d/50-blockhid.rules https://github.com/CIRCL/Circlean/blob/master/circlean_fs/ro... However, that could be bypassed if the USB key acted like a USB hub with a keyboard attached. If you do get a keyboard working, it looks like you can just log in with raspberry / raspberry and then full privileged access since sudo from the raspberry user, and /dev/kmem from root is enabled. That would allow arbitrary content to be copied on to the user supplied USB, and depending on the device, possibly firmware reprogramming.
  - leni536 10y ago
    Huh, at least it seems that they care about this attach vector. Blacklisting seems to be the wrong approach.
- lucb1e 10y ago
  > They can mitigate against badUSB by only whitelisting I'd say just don't run a graphical environment or, if you do, lock it. With a normal password, good luck to the USB thumb drive that pretends to be a keyboard. As for booting, well, don't have it in there at boot time. As for malware in the files itself -- I don't think that's the point of this project. It says "if you don't trust the transport medium (i.e. USB)", it's not about the contents.
jaclaz 10y ago
But it's the assumption that is in itself inaccurate. Case #1 is about a modified firmware of the USB controller in the USB stick, case #2 assumes that a boot is initiated from the USB stick. What the Circlean thingy does is more similar to an antivirus, it examines the contents (files) on the USB stick filesystem and only copies to the second stick those files of known type, according to the given rules. Whether this is effective against everything is another thing, of course. Only "plain" files are directly copied, other supported ones are analyzed and converted, some more detiled info is here: https://github.com/CIRCL/Circlean/blob/master/README.md https://github.com/CIRCL/Circlean/blob/master/README.md The thing is not really "new": https://news.ycombinator.com/item?id=8216853 https://news.ycombinator.com/item?id=8216853
- leni536 10y ago
  No, I think the assumption is entirely correct. If you can't trust a USB stick's contents then you probably can't trust its controller itself. But your OS doesn't have to say "Oh, you are a keyboard? Here, open a terminal and type arbitrary commands." It can say "Sorry, I only talk to USB mass storage class devices."
  - ckastner 10y ago
    What about the pre-boot phase, before the OS is loaded?
    - leni536 10y ago
      1. You can avoid inserting anything before the OS boots up. 2. You can disable booting from USB in the BIOS. However I think you can't disable keyboards there, so a badUSB device can potentially enter the bios, enable USB booting then infect the machine by booting into the virus. Disabling USB booting and setting a strong BIOS password can be safe, I would still prefer the first option though.
      - ckastner 10y ago
        Agreed, but in this specific case, CIRCLean depends on the keys being inserted before boot (see steps 2 - 4).
JohnStrange 10y ago
Not necessarily, it should be possible to do this correctly, although I doubt this specific device does so. The device itself needs to be hardened against USB attacks, otherwise it would be pointless, of course. Then it copies the contents of the malicious USB stick into a buffer storage, analyses the buffer and cleans up the documents on it, and then it unmounts the first device, mounts the second device and copies the contents of the buffer to it. If it also allows for write-protection, then it might be interesting for forensic work. (AFAIK, USB write protectors cost a few hundred bucks, and maybe this device is the cost range.) The crucial question is, of course, how well the device is hardened against targeted attacks. Just using some seemingly secure Linux won't suffice.

leni536 10y ago

They can mitigate against badUSB by only whitelisting the generic USB mass storage class driver. No keyboard, no mouse, etc... I am not confident they do this though.

A1kmm 10y ago
Looks like they don't, but they turn off usbhid on that particular port: https://github.com/CIRCL/Circlean/blob/master/circlean_fs/root_partition/etc/udev/rules.d/50-blockhid.rules https://github.com/CIRCL/Circlean/blob/master/circlean_fs/ro... However, that could be bypassed if the USB key acted like a USB hub with a keyboard attached. If you do get a keyboard working, it looks like you can just log in with raspberry / raspberry and then full privileged access since sudo from the raspberry user, and /dev/kmem from root is enabled. That would allow arbitrary content to be copied on to the user supplied USB, and depending on the device, possibly firmware reprogramming.
- leni536 10y ago
  Huh, at least it seems that they care about this attach vector. Blacklisting seems to be the wrong approach.
lucb1e 10y ago
> They can mitigate against badUSB by only whitelisting I'd say just don't run a graphical environment or, if you do, lock it. With a normal password, good luck to the USB thumb drive that pretends to be a keyboard. As for booting, well, don't have it in there at boot time. As for malware in the files itself -- I don't think that's the point of this project. It says "if you don't trust the transport medium (i.e. USB)", it's not about the contents.

jaclaz 10y ago

But it's the assumption that is in itself inaccurate. Case #1 is about a modified firmware of the USB controller in the USB stick, case #2 assumes that a boot is initiated from the USB stick. What the Circlean thingy does is more similar to an antivirus, it examines the contents (files) on the USB stick filesystem and only copies to the second stick those files of known type, according to the given rules. Whether this is effective against everything is another thing, of course. Only "plain" files are directly copied, other supported ones are analyzed and converted, some more detiled info is here: https://github.com/CIRCL/Circlean/blob/master/README.md https://github.com/CIRCL/Circlean/blob/master/README.md The thing is not really "new": https://news.ycombinator.com/item?id=8216853 https://news.ycombinator.com/item?id=8216853

leni536 10y ago
No, I think the assumption is entirely correct. If you can't trust a USB stick's contents then you probably can't trust its controller itself. But your OS doesn't have to say "Oh, you are a keyboard? Here, open a terminal and type arbitrary commands." It can say "Sorry, I only talk to USB mass storage class devices."
- ckastner 10y ago
  What about the pre-boot phase, before the OS is loaded?
  - leni536 10y ago
    1. You can avoid inserting anything before the OS boots up. 2. You can disable booting from USB in the BIOS. However I think you can't disable keyboards there, so a badUSB device can potentially enter the bios, enable USB booting then infect the machine by booting into the virus. Disabling USB booting and setting a strong BIOS password can be safe, I would still prefer the first option though.
    - ckastner 10y ago
      Agreed, but in this specific case, CIRCLean depends on the keys being inserted before boot (see steps 2 - 4).

JohnStrange 10y ago

Not necessarily, it should be possible to do this correctly, although I doubt this specific device does so. The device itself needs to be hardened against USB attacks, otherwise it would be pointless, of course. Then it copies the contents of the malicious USB stick into a buffer storage, analyses the buffer and cleans up the documents on it, and then it unmounts the first device, mounts the second device and copies the contents of the buffer to it. If it also allows for write-protection, then it might be interesting for forensic work. (AFAIK, USB write protectors cost a few hundred bucks, and maybe this device is the cost range.) The crucial question is, of course, how well the device is hardened against targeted attacks. Just using some seemingly secure Linux won't suffice.