I wonder why the drivers don't do this on startup. Judging by the specs, most GPUs have enough memory bandwidth to clear all of their memory in less than one second.
Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
31–40 of 47 posts
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#32A few thoughts ... First, tails scrubs memory (or something like that) when you shut down - should they be scrubbing vram as well ? Second, wouldn't it be quick and simple to "scrub" vram by filling it up with intensive usage after working on sensitive information ? What happens if I watch 2 minutes of 1080p video - wouldn't we expect all previous framebuffer data to be flushed at that point ? Finally, I would be ver…
> should they be scrubbing vram as well
Yes, but VRAM is a tricky beast. Modern GPUs actually have MMUs and the VRAM address layout the CPU sees may not cover the whole of the memory of the graphics card.
> What happens if I watch 2 minutes of 1080p video - wouldn't we expect all previous framebuffer data to be flushed at that point ?
No, because the video frames will be queued in a circular buffer and anything outside of that doesn't get touched.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#33Will shutting down erase the vram completely? Also why does rebooting not erase the memory completely?
http://en.wikipedia.org/wiki/Cold_boot_attack
I don't specifically know the answer to your first question if the VRAM is not DRAM (shared memory), but certainly rebooting will not simply automatically clear out DRAM.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#34Will shutting down erase the vram completely? Also why does rebooting not erase the memory completely?
http://en.wikipedia.org/wiki/Cold_boot_attack I don't specifically know the answer to your first question if the VRAM is not DRAM (shared memory), but certainly rebooting will not simply automatically clear out DRAM.
shutdown clears, reboot doesnt.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#35This is actually one thing that bugs me about OpenGL, DirectX? and Vulkan. Basically all the insentive so far is best speed. That means there's almost zero insentive for security in GPU drivers. You can try to implement security on top of the GPU. WebGL does this. Chrome also does this for most (all?) of its GPU access meaning even its page rendering is going through Chrome's secured GPU system that clears buffers an…
In these tests we were able to recover screenshot-like views of entire websites after viewing them in the newest version of chromium, then running the poc on the local system.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#36Something similar happened to me, but with a different scenario. I hibernated my Arch Linux system and then booted into Windows (I unmount all of my NTFS partitions beforehand), did some work, and then rebooted into Linux again. The GNOME lock screen doesn't play nice with my NVIDIA drivers (closed-source), so it doesn't reinitialize the lock screen texture when it wakes up from suspend-to-RAM or suspend-to-disk. The…
I've seen worse.
An old Dell laptop, which originally came with Windows, repurposed as a Linux laptop. It had been used exclusively as a Linux laptop (the Windows partitions had been overwritten by the Linux install) for several months if not years, when one day, its lock screen displayed a Windows desktop (I don't recall if the laptop had just returned from suspend or not). Moving the mouse dispelled the "ghost" screen and showed the normal lock screen.
The only explanation I could come up with for that was that, somehow, that particular screen had survived intact in a corner of the video RAM, for months, until a bug in the Linux video driver made it appear.
Makes one wonder how long can information survive in a laptop's video RAM. The laptop had never completely lost power (it has a battery, after all), but it had been powered off daily; it wasn't left on suspend all the time.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#37A few thoughts ... First, tails scrubs memory (or something like that) when you shut down - should they be scrubbing vram as well ? Second, wouldn't it be quick and simple to "scrub" vram by filling it up with intensive usage after working on sensitive information ? What happens if I watch 2 minutes of 1080p video - wouldn't we expect all previous framebuffer data to be flushed at that point ? Finally, I would be ver…
> should they be scrubbing vram as well Yes, but VRAM is a tricky beast. Modern GPUs actually have MMUs and the VRAM address layout the CPU sees may not cover the whole of the memory of the graphics card. > What happens if I watch 2 minutes of 1080p video - wouldn't we expect all previous framebuffer data to be flushed at that point ? No, because the video frames will be queued in a circular buffer and anything outsi…
The only way I can see to reliably scrub VRAM would be to use the GPU as a "dumb framebuffer" (without video acceleration), like in the good old days. Then to scrub what was used in the session it should be enough to draw a black screen, do a page flip, and draw a black screen again.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#38On a laptop with an Intel HD4000 and a dedicated nVidia card where the OS can switch between cards, one has to force the usage of the dedicated card to read from VRAM. The internal graphics card seems to be unaffected at the moment. Makes sense; integrated GPUs (UMA) share the same RAM as the rest of the system, which will get cleared as the BIOS does its RAM test at POST (this might not always be the case if 'fastbo…
> (this might not always be the case if 'fastboot' or similar features are enabled.)
I haven't seen a computer or laptop with fastboot disabled in over a decade...
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#39Earlier quoted context omitted.
http://en.wikipedia.org/wiki/Cold_boot_attack I don't specifically know the answer to your first question if the VRAM is not DRAM (shared memory), but certainly rebooting will not simply automatically clear out DRAM.
shutdown clears, reboot doesnt.
Shutdown actually doesn't clear RAM, hence the "cold boot attack" terminology. Eventually the data will degrade, but eventually can be a long time.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#40This is actually one thing that bugs me about OpenGL, DirectX? and Vulkan. Basically all the insentive so far is best speed. That means there's almost zero insentive for security in GPU drivers. You can try to implement security on top of the GPU. WebGL does this. Chrome also does this for most (all?) of its GPU access meaning even its page rendering is going through Chrome's secured GPU system that clears buffers an…
In these tests we were able to recover screenshot-like views of entire websites after viewing them in the newest version of chromium, then running the poc on the local system.
Chrome isn't trying to not let other (non-chrome) processes read info. It's trying not to let other chrome processes (other webpages, native client, etc) not read info. In other words, stuff running inside Chrome can't read stuff it's not supposed to be able to since nearly all that code is untrusted.