Re: [xml] Potential problem with 2.7.4

[Daniel Veillard <veillard redhat com>]

On Tue, Sep 15, 2009 at 07:57:17PM +0200, Mike Hommey wrote:
> On Tue, Sep 15, 2009 at 07:43:54PM +0200, Daniel Veillard wrote:
> >   Some application don't deliver sufficient data at start of parsing
> > conflicting with the fix I made for 
> >
> >   https://bugzilla.gnome.org/show_bug.cgi?id=566012 
> >
> > I commited a fix which solves the problem while preserving the EBCDIC
> > parsing fix:
> >
> > http://git.gnome.org/cgit/libxml2/commit/?id=9d3d141c412baa5c713ad3df48f1a4d179e07b05
>
> +     * than just the first line, unless the amount of data is really
> +     * too small to hold "<?xml version="1.0" encoding="foo"
>       */
> +    if ((ctxt->input->end - ctxt->input->cur) < 35) {
> +       GROW;
> +    }
>
> Can't there be another similar problem later in the code when that GROW
> still doesn't get enough to hold "<?xml version="1.0" encoding="foo" ?

  It's a trade-off, basically the first line is nasty because you have
to guess an encoding and only at the end of the first line you can
actually be sure you use the right decoder. If you push too agressively
the risk is to corrupt the first bytes of the content as 566012
demonstrated.

  basically if in 2 calls to GROW you didnt got enough for the first
line well yes you're at risk, but IMHO the client side is fairly broken
then.

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/