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From Ruediger Pluem <rpl...@apache.org>
Subject Re: CVE-2013-5704 fix breaks mod_wsgi
Date Fri, 09 Jan 2015 20:55:20 GMT


On 01/09/2015 09:48 PM, Jeff Trawick wrote:
> On Fri, Jan 9, 2015 at 3:23 PM, Joe Orton <jorton@redhat.com <mailto:jorton@redhat.com>>
wrote:
> 
>     Since Jim is talking 2.4.11, I should report this now.  We discovered
>     this week in Fedora: mod_wsgi does some interesting things in daemon
>     mode, notably that it allocates a request_rec internally which ends up
>     getting used by httpd.
> 
>     Reason is, the fix for CVE-2013-5704 extends the request_rec:
> 
>     http://svn.apache.org/r1619884
> 
>     A mod_wsgi built against <= 2.4.10 will allocate a request_rec using the
>     old, smaller "wrong" size, and hence, if such a build is used with >=
>     2.4.11, it passes in the wrong-sized request_rec and that breaks later
>     when httpd tries to access r->trailers_*.
> 
>     It's one of those fuzzy boundaries in the API, you can argue mod_wsgi is
>     wrong, but, I could argue it back; the struct *is* public, not got a
>     strong opinion on this personally.
> 
>     Either way, the fix for CVE-2013-5704 ends up breaking backwards
>     compatibility with existing 2.4.x builds of mod_wsgi, which is kind of
>     Bad.  I don't have a good proposal for how to fix or avoid this.  Worst
>     case, we make clear the mod_wsgi case is API/ABI abuse and warn binary
>     distributors they have to handle this by rebuilding.
> 
>     Regards, Joe
> 
> 
> * One-time only: Make clear in announcement that mod_wsgi has to be rebuilt.
> * Add helper functions to allocate a request_rec, conn_rec, server_rec.  It doesn't solve
all possible problems of
> course but can drastically reduce the frequency of needing to recompile a module that
needs to do such things.
> * Module authors who allocate structures generally created by httpd own the monitoring
and announcement, or should just
> document "You must recompile this module every time you update httpd."
> 

+1

Regards

RĂ¼diger


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