Re: [xml] libxml security

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From: Daniel Veillard (Daniel.Veillard@w3.org)
Date: Sat Jul 08 2000 - 06:11:06 EDT


On Fri, Jul 07, 2000 at 01:40:52PM -0700, Joe McAlerney wrote:
>
> Hello Daniel,
>
> I was wondering about the precautions taken to avoid such caterstrophic
> things as buffer overflows and the like in libxml. Since libxml is
> widely portable, I'm assuming that efforts have been made to avoid using
> secure OS specific functions. I noticed in some places that you use
> snprintf if it is available, and sprintf if it is not. Obviously you
> have put thought into this issue as well, and have coded accordingly.

  First I'm not a security expert. I know how buffers overflows can be
used to execute arbitrary code, and I have tried to write libxml in
the most robust fashion. Basically rather that targetting at security
I targetted at "no input given to libxml should ever allow it to segfault".
  This is a different bias, but I assume it should lead to a secure
library.
  Now as far as I know I received only once a security related message,
it was about places where I didn't used snprintf when available. I don't
think there was really a strong security audit of libxml itself, and I'm
afraid I don't really have the expertise. Feddback on this issue are
really welcome.

> We want to use libxml in a project, and just wanted to get a sense of
> how it may hold up against something like a rogue xml document being fed
> into the parser. Unfortunately, I don't have enought experience to do a
> full audit of the code. If you can provide any insite on this subject,
> it would be most appreciated.

  Well I think crashing libxml with random input should not be easy,
It's a good first point. But I can't provide guarantees except to
close any hole pointed at me !

Daniel

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