4 ms·

Would putting the bluetooth stack on a dedicated IC be an adequate securiry measure?

woodruffw 4y ago
I think the presence of any connection and data transfer is more important than the physical layout of the hardware. Compare, for example, baseband exploits.
- lxgr 4y ago
  Baseband exploits are as devastating as they are because at least until a few years ago, they've had full SoC memory access and as a result more privileges than even the operating system running on the SoC. Treating the baseband more like a peripheral device and less as a coprocessor can prevent against much of this attack surface. That said, just adding Bluetooth (even given a perfectly isolated stack) opens several unnecessary attack vectors, including a MITM between the wallet and the device driving it. This could be used to e.g. subtly modify destination addresses or transfer amounts.
  - woodruffw 4y ago
    Right. I'm not saying it isn't a reasonable hardening choice, only that it isn't a proof of security. It's table stakes for something claiming to be secure hardware in 2022.
  - leni536 4y ago
    The whole reason of the display on the device is to show both the amount and destination before signing the transaction.
    - lxgr 4y ago
      Yes, a display is essential for the wallet use case. But why make it such a large/complex one, that definitely requires more trusted hardware and software in the validation and confirmation path? Their previous wallets did this much better, in my opinion. The Stax just seems flashy at the expense of security.
pclmulqdq 4y ago
It might be, and it might not be. It's hard to say. If your device can receive OTA updates via Bluetooth, no. If your device has a "developer" API, almost certainly no. If the two chips share a power rail, possibly not. Without serious thought to security of requests and responses (such that MITMs are impossible), no. There are a lot of ways this can go wrong even with separate chips.
- popol12 4y ago
  As OTA updates would be signed just like regular updates, can you detail how they would make Bluetooth less secure than USB ?
  - pclmulqdq 4y ago
    Yes, a compromised Bluetooth chip may be able to replay an old update or simply block a new one and leave you with a vulnerable version of your software.
    - popol12 4y ago
      First case you describe is not possible, there’s no downgrading possible on ledger ‘s OS, it’s up only Second case would be obvious to user, he would see the failing attempts at updating.
thesh4d0w 4y ago
This is worth a read if you haven't seen it: pt 1: https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_4.html https://googleprojectzero.blogspot.com/2017/04/over-air-expl... pt 2: https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_11.html https://googleprojectzero.blogspot.com/2017/04/over-air-expl... TLDR: Google research exploits wifi firmware of broadcom chip in iphone, then uses that to exploit a driver bug, and manages to root the iphone. All without even connecting it to a specific AP, just from broadcast packets.

I think the presence of any connection and data transfer is more important than the physical layout of the hardware. Compare, for example, baseband exploits.

lxgr 4y ago
Baseband exploits are as devastating as they are because at least until a few years ago, they've had full SoC memory access and as a result more privileges than even the operating system running on the SoC. Treating the baseband more like a peripheral device and less as a coprocessor can prevent against much of this attack surface. That said, just adding Bluetooth (even given a perfectly isolated stack) opens several unnecessary attack vectors, including a MITM between the wallet and the device driving it. This could be used to e.g. subtly modify destination addresses or transfer amounts.
- woodruffw 4y ago
  Right. I'm not saying it isn't a reasonable hardening choice, only that it isn't a proof of security. It's table stakes for something claiming to be secure hardware in 2022.
- leni536 4y ago
  The whole reason of the display on the device is to show both the amount and destination before signing the transaction.
  - lxgr 4y ago
    Yes, a display is essential for the wallet use case. But why make it such a large/complex one, that definitely requires more trusted hardware and software in the validation and confirmation path? Their previous wallets did this much better, in my opinion. The Stax just seems flashy at the expense of security.

pclmulqdq 4y ago

It might be, and it might not be. It's hard to say. If your device can receive OTA updates via Bluetooth, no. If your device has a "developer" API, almost certainly no. If the two chips share a power rail, possibly not. Without serious thought to security of requests and responses (such that MITMs are impossible), no. There are a lot of ways this can go wrong even with separate chips.

popol12 4y ago
As OTA updates would be signed just like regular updates, can you detail how they would make Bluetooth less secure than USB ?
- pclmulqdq 4y ago
  Yes, a compromised Bluetooth chip may be able to replay an old update or simply block a new one and leave you with a vulnerable version of your software.
  - popol12 4y ago
    First case you describe is not possible, there’s no downgrading possible on ledger ‘s OS, it’s up only Second case would be obvious to user, he would see the failing attempts at updating.

thesh4d0w 4y ago

This is worth a read if you haven't seen it: pt 1: https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_4.html https://googleprojectzero.blogspot.com/2017/04/over-air-expl... pt 2: https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_11.html https://googleprojectzero.blogspot.com/2017/04/over-air-expl... TLDR: Google research exploits wifi firmware of broadcom chip in iphone, then uses that to exploit a driver bug, and manages to root the iphone. All without even connecting it to a specific AP, just from broadcast packets.