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Thunderbolt in current and future laptops

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Re: Thunderbolt in current and future laptops

#21

Post by wtallis »

Groxx wrote: post #17
gst wrote: post #14

From a security perspective Thunderbolt is one of the worst things that can happen. Imagine being a speaker at a conference where you use your own laptop for a presentation and where (at some point in the future) the projector only has a Thunderbolt interface. Are you going to connect your laptop? If you do the projector has basically full access to your laptops memory - and therefore full control over your laptop. E…

Don't USB and Firewire both have DMA as well? This sort of attack has been possible for a long time: http://replay.web.archive.org/20090402130220/http://storm.ne...

DMA has historically been Firewire's one big advantage over USB, which even in the 3.0 revision doesn't do DMA.

Re: Thunderbolt in current and future laptops

#22

Post by gst »

Groxx wrote: post #17
gst wrote: post #14

From a security perspective Thunderbolt is one of the worst things that can happen. Imagine being a speaker at a conference where you use your own laptop for a presentation and where (at some point in the future) the projector only has a Thunderbolt interface. Are you going to connect your laptop? If you do the projector has basically full access to your laptops memory - and therefore full control over your laptop. E…

Don't USB and Firewire both have DMA as well? This sort of attack has been possible for a long time: http://replay.web.archive.org/20090402130220/http://storm.ne...

Yes, Firewire also uses DMA, but hardly anyone uses Firewire anymore :) And even the people who still use Firewire typically don't use it to connect to third-party devices (such as projectors).

With USB I must to admit that I'm not 100% sure. I've always assumed that USB does not use DMA, but after googling it it seems that there's some DMA support in USB. Would be interesting to know if there's some kind of fallback mode - e.g., in order to use a less efficient (but more secure) protocol if the computer does not support (or enable) DMA.

Re: Thunderbolt in current and future laptops

#23

Post by wtallis »

gst wrote: post #14

From a security perspective Thunderbolt is one of the worst things that can happen. Imagine being a speaker at a conference where you use your own laptop for a presentation and where (at some point in the future) the projector only has a Thunderbolt interface. Are you going to connect your laptop? If you do the projector has basically full access to your laptops memory - and therefore full control over your laptop. E…

IOMMU support is going to be universal long before DisplayPort support (let alone Thunderbolt support) is even common for projectors.

Re: Thunderbolt in current and future laptops

#24

Post by masklinn »

masklinn wrote: post #7
cloudwalking wrote: post #5

I hope somebody is planning an external graphics card.

Would be very slow, considering a thunderbolt channel is roughly similar to 1x PCI-E v3. I would also expect greater latencies than on internal PCI-E. While it would probably be nice for GPGPU cases where not (if mot all) the working set stays on-board, that's far from the general usage case for GPUs right now. Even for multiple-screen it would not be that useful: DisplayPort 1.2 handles chaining, and where you have…

Oh god, how did I manager to submit a comment containing "where not (if mot all)"?

I, of course, meant "where most (if not all)". Sorry about that.

Re: Thunderbolt in current and future laptops

#25

Post by Groxx »

bengl3rt wrote: post #11
kylec wrote: post #2

In addition to being able to reduce the size of laptops, I hope Thunderbolt will enable the next generation Cinema display to feature gigabit ethernet and firewire connectors, making it possible to connect a single cable (two, if you count the MagSafe) to seamlessly transform a laptop into an iMac.

I was actually hoping that they would build a small, low-power GPU into the Cinema Display so that I can daisy chain five off them off a Macbook Air and have each provide its own "graphics card" over Thunderbolt.

There's an interesting idea... though I have no idea how well it would work. The bandwidth is still massively below what graphics cards typically need. With some OS changes and essentially half-remote-desktopping to a dumb terminal display, it could work, though...

You have given me thoughts. Thanks :D

Re: Thunderbolt in current and future laptops

#26

Post by haberman »

gst wrote: post #14

From a security perspective Thunderbolt is one of the worst things that can happen. Imagine being a speaker at a conference where you use your own laptop for a presentation and where (at some point in the future) the projector only has a Thunderbolt interface. Are you going to connect your laptop? If you do the projector has basically full access to your laptops memory - and therefore full control over your laptop. E…

The article mentions this issue explicitly. According to http://en.wikipedia.org/wiki/Thunderbolt_(interface)#Securit..., Nehalem (and later) CPUs have an IOMMU that let the OS choose which parts of memory to map into the device's address space.

In other words, this issue has been dealt with: you don't expose all of your laptop's memory to Thunderbolt devices.

Re: Thunderbolt in current and future laptops

#27

Post by zdw »

gst wrote: post #22
Groxx wrote: post #17

Earlier quoted context omitted.

Don't USB and Firewire both have DMA as well? This sort of attack has been possible for a long time: http://replay.web.archive.org/20090402130220/http://storm.ne...

Yes, Firewire also uses DMA, but hardly anyone uses Firewire anymore :) And even the people who still use Firewire typically don't use it to connect to third-party devices (such as projectors). With USB I must to admit that I'm not 100% sure. I've always assumed that USB does not use DMA, but after googling it it seems that there's some DMA support in USB. Would be interesting to know if there's some kind of fallback…

Turning on the firmware password on a Mac blocks Firewire DMA access to main memory, if you're concerned about that.
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