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Re: [Xen-devel] boot loaders for domain != 0

  • To: xen-devel@xxxxxxxxxxxxxxxxxxxxx
  • From: Jacob Gorm Hansen <jacobg@xxxxxxx>
  • Date: Thu, 03 Feb 2005 17:09:28 -0800
  • Delivery-date: Fri, 04 Feb 2005 01:13:28 +0000
  • List-id: List for Xen developers <xen-devel.lists.sourceforge.net>

Ian Pratt wrote:
For what it's worth, I think doing a quick mount, read, and then umount is the easiest approach since it extends well to doing things like peeking at an ISO's contents by mounting an ISO image. Using libraries would probably introduce some nasty dependencies without really gaining much...

From a security POV, using libext2 etc would be raher better. I just
don't trust Linux to be defensive enough mounting a potentially
malicious bag of bits. [I once came across an ext2 file systems that
deterministically crashed Linux whenever I mounted it. It's been a
couple of years, but I reckon such bugs are still lurking.]

Then libext2 would have to run as a non-root user, and feed its output to a root process doing the actual domain building, assuming that there is no way of making the domain builder or libz choke on the kernel image that is...

For real security, all this stuff has to be happen within the domU. In a perfect world, privileged code should never read user-supplied data, but given that this world is not perfect, you could relax that to not reading any variable-length user-supplied data.

Given that both the (perhaps compressed) ELF image and the Ext2 filesystem contain variable-length data, neither should be read by code in dom0.


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