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Every PCI device in your computer could be hosting a backdoor: "The PCI specification defines an 'expansion ROM' mechanism whereby a PCI card can include a bit

by cs702 13y ago

Every PCI device in your computer could be hosting a backdoor: "The PCI specification defines an 'expansion ROM' mechanism whereby a PCI card can include a bit of code for the BIOS to execute during the boot procedure. This is intended to give the hardware a chance to initialize itself, but we can also use it for our own purposes." The idea is to hook the interrupt handler that normally invokes BIOS code for handling hard drive I/O at boot time so it invokes instead code in the PCI device that applies a backdoor patch to the Linux kernel when it is read off the disk. The author explains how to patch the Linux kernel by overwriting an obscure, seldom-used error message string, and provides sample code for a simple kernel patch that will listen for IP packets with an unused protocol number and run any payload delivered via them on a Linux shell with root privileges. It's scary how straightforward this looks. Whenever I read things like this, I'm reminded that every day we're trusting our data and privacy to the people who design, build, and distribute all the hardware (and software) we use but didn't create ourselves from scratch. To paraphrase Ken Thompson, we have little choice but to trust trust.[1] -- [1] http://cm.bell-labs.com/who/ken/trust.html http://cm.bell-labs.com/who/ken/trust.html

frank_boyd 13y ago
In other words, there's a serious "open hardware" market opportunity waiting to be captured.
- geofft 13y ago
  Mostly waiting to be researched instead of captured. We're only just starting to figure out how to compile software such that the binary can be audited and proved to match the source. How do you fab hardware so that the IC can be proved to match the blueprint?
  - dobbsbob 13y ago
    3D printed Lisp machines :p
- daeken 13y ago
  There's really no way for open hardware to be better. Unless you have your own fab, the only way to ensure that back doors haven't been added at the hardware level is to decap and manually validate every chip. That's pretty clearly not viable.
  - Dwolb 13y ago
    Couldn't get the performance out of current technology at a reasonable price point, but perhaps in the future we'll have open-source processors running open source peripherals and controllers on FPGAs (blank configuration until boot-up).
  - autodidakto 13y ago
    Don't mix up "better" with "perfect". That's the mistake made by people who post a link to the trusting-trust: Trust isn't binary. "Perfect or give up" is a false dichotomy. I sometimes say "trust no one", which seems to support that false dichotomy, but I mean to say "Reduce and distribute trust". Open source code and hardware doesn't remove trust. It reduces the amount of trust required and distributes it among more parties. It makes betrayal harder, more expensive, more temporary, and less destructive. That's not perfect, but that's much, much better. There's a world of difference between closed source software from MegaCorporatism Inc and open source -- even if an evil genius is still technically capable of sneaking something into a compiler or chip.
    - jacquesm 13y ago
      Well, in this case it is a binary thing. When you talk about this in an applied sense you're right, then it isn't a binary thing but when you talk about feasibility then it is black-or-white. You're either sure or it might as well be compromised.
      - Karunamon 13y ago
        Not necessarily. As the author of the article said, it's easier to rely on software bugs than to ship a crocked piece of hardware like this. If you manage to backdoor a mass-production piece of hardware (let's say this is a wifi card or something else similar), you're just one odd error away from someone curious finding out what's happening, raising the alarm, and the whole operation comes crashing down. From a logistics standpoint, it's easier to break software.
- gnarbarian 13y ago
  Another interesting way to look at it is to assume all or some large percentage of the computers in your network are compromised in some unknowable way with hardware or software backdoors/keyloggers. What measures could you employ in the design of your network (both physical/topological and logical) to minimize the effectiveness of these backdoors? I think it would look similar to how tor diffuses things around the network such that you would need to control a significant number of nodes before being able to discover the identity of a user or the contents of the data bound for that user. The most obvious answer would be air gaps for absolutely critical systems. For systems where this is not a viable option, how could you best detect/prevent unauthorized attempts from compromised nodes on your network to 'phone home'? My first thought would be to establish multiple redundant gateways on the network with completely different software/hardware stacks which would all perform the exact same job of vetting packets coming across the network. Along with another set of computers which also have unique stacks which verify that the gateways are all performing identically and no extra sneaky packets are being sent out thorough one gateway and not others.
ChuckMcM 13y ago
This is a known issue. And it has been exploited for kinda sorta these reasons. One was an Intel product where the boot roms hosted their own system management product. Basically you could do anything though that code including reflashing the BIOS on the mother board, all by plugging in a simple Intel NIC. Later it became this : http://www.intel.com/content/www/us/en/server-management/intel-remote-management-module.html http://www.intel.com/content/www/us/en/server-management/int... It gets worse if you can load custom firmware on a disk drive. (which anyone can do). Then you load your firmware which says its the firmware that the drive had on it when it was shipped, except it has some features for diddling bits in the read cache if certain conditions are met. Not sure where it ends.

by cs702 13y ago

frank_boyd 13y ago

In other words, there's a serious "open hardware" market opportunity waiting to be captured.

geofft 13y ago
Mostly waiting to be researched instead of captured. We're only just starting to figure out how to compile software such that the binary can be audited and proved to match the source. How do you fab hardware so that the IC can be proved to match the blueprint?
- dobbsbob 13y ago
  3D printed Lisp machines :p
daeken 13y ago
There's really no way for open hardware to be better. Unless you have your own fab, the only way to ensure that back doors haven't been added at the hardware level is to decap and manually validate every chip. That's pretty clearly not viable.
- Dwolb 13y ago
  Couldn't get the performance out of current technology at a reasonable price point, but perhaps in the future we'll have open-source processors running open source peripherals and controllers on FPGAs (blank configuration until boot-up).
- autodidakto 13y ago
  Don't mix up "better" with "perfect". That's the mistake made by people who post a link to the trusting-trust: Trust isn't binary. "Perfect or give up" is a false dichotomy. I sometimes say "trust no one", which seems to support that false dichotomy, but I mean to say "Reduce and distribute trust". Open source code and hardware doesn't remove trust. It reduces the amount of trust required and distributes it among more parties. It makes betrayal harder, more expensive, more temporary, and less destructive. That's not perfect, but that's much, much better. There's a world of difference between closed source software from MegaCorporatism Inc and open source -- even if an evil genius is still technically capable of sneaking something into a compiler or chip.
  - jacquesm 13y ago
    Well, in this case it is a binary thing. When you talk about this in an applied sense you're right, then it isn't a binary thing but when you talk about feasibility then it is black-or-white. You're either sure or it might as well be compromised.
    - Karunamon 13y ago
      Not necessarily. As the author of the article said, it's easier to rely on software bugs than to ship a crocked piece of hardware like this. If you manage to backdoor a mass-production piece of hardware (let's say this is a wifi card or something else similar), you're just one odd error away from someone curious finding out what's happening, raising the alarm, and the whole operation comes crashing down. From a logistics standpoint, it's easier to break software.
gnarbarian 13y ago
Another interesting way to look at it is to assume all or some large percentage of the computers in your network are compromised in some unknowable way with hardware or software backdoors/keyloggers. What measures could you employ in the design of your network (both physical/topological and logical) to minimize the effectiveness of these backdoors? I think it would look similar to how tor diffuses things around the network such that you would need to control a significant number of nodes before being able to discover the identity of a user or the contents of the data bound for that user. The most obvious answer would be air gaps for absolutely critical systems. For systems where this is not a viable option, how could you best detect/prevent unauthorized attempts from compromised nodes on your network to 'phone home'? My first thought would be to establish multiple redundant gateways on the network with completely different software/hardware stacks which would all perform the exact same job of vetting packets coming across the network. Along with another set of computers which also have unique stacks which verify that the gateways are all performing identically and no extra sneaky packets are being sent out thorough one gateway and not others.

ChuckMcM 13y ago

This is a known issue. And it has been exploited for kinda sorta these reasons. One was an Intel product where the boot roms hosted their own system management product. Basically you could do anything though that code including reflashing the BIOS on the mother board, all by plugging in a simple Intel NIC. Later it became this : http://www.intel.com/content/www/us/en/server-management/intel-remote-management-module.html http://www.intel.com/content/www/us/en/server-management/int... It gets worse if you can load custom firmware on a disk drive. (which anyone can do). Then you load your firmware which says its the firmware that the drive had on it when it was shipped, except it has some features for diddling bits in the read cache if certain conditions are met. Not sure where it ends.