Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
1–10 of 47 posts
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#2That's very interesting. I guess VRAM doesn't get powered off during reboot and (today) it is huge, so the chance of interesting information remaining is big.
Mitigation strategy: Ctrl-Alt-F1 and work in text mode. (or just fill up video ram doing stuff in your machine after doing the sensitive work)
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#3That's very interesting. I guess VRAM doesn't get powered off during reboot and (today) it is huge, so the chance of interesting information remaining is big. Mitigation strategy: Ctrl-Alt-F1 and work in text mode. (or just fill up video ram doing stuff in your machine after doing the sensitive work)
Best mitigation strategy is not to share VRAM by disabling 3d acceleration with Guests you absolutely don't want to snoop on your host pixels.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#4I recently wrote a library that rasterizes a PDF page to an image and was observing a very similar behavior. It was also highly system dependent and erratic as well. I would randomly see a distorted image of my own screen when I run my program on any PDF. Then figured out I was not initializing the buffer I was using to render the PDF page to image. After I memset'ed it to zero, the problem went away. I still couldn't quite comprehend what was exactly happening in the background.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#5Amusingly, BIOS features to test/clear memory are usually disabled due to boot performance impact.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#6That's very interesting. I guess VRAM doesn't get powered off during reboot and (today) it is huge, so the chance of interesting information remaining is big. Mitigation strategy: Ctrl-Alt-F1 and work in text mode. (or just fill up video ram doing stuff in your machine after doing the sensitive work)
Best mitigation strategy is not to share VRAM by disabling 3d acceleration with Guests you absolutely don't want to snoop on your host pixels.
That takes care of the "Guest snooping on the Host" case, but not the case of physical attack on the machine.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#7On 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 'fastboot' or similar features are enabled.)
Another observation from this would be that GPUs do not do any memory tests on their VRAM, which also agrees with the fact that most of the time failed VRAM just causes artifacts to show up and no message/etc. upon boot. Models designed for GPGPU use may behave differently.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#8Does this have any bearing on WebGL?
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#9Does this have any bearing on WebGL?
The webgl standard has rather strong memory safety considerations:
WebGL resources such as textures and vertex buffer objects (VBOs) must always contain initialized data, even if they were created without initial user data values.[0]
As long as browser vendors implement this (and chrome and firefox seem to), this should not be an issue.
Re: Is Your VirtualBox Reading Your E-Mail? Reconstruction of FrameBuffers from VRAM
#10This is an issue for any software that is able to access the GPU: http://blog.lxgr.net/tag/opengl.html