Re: Gentoo glibc security advisory

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Aug 18, 2004 at 10:41:35AM +0200, Thorsten Kukuk wrote:
> 
> Hi,
> 
> Gentoo has issued an advisory: 
> http://www.gentoo.org/security/en/glsa/glsa-200408-16.xml 
>  
> "An attacker can gain the list of symbols a SUID application uses and their 

That's true.

> locations

LD_DEBUG=all doesn't give you exact addresses of symbols
(but LD_TRACE_PRELINKING=1 does, maybe we should turn that off for
__libc_enable_secure and missing /etc/suid-debug).
It only tells you which libraries' symbols are used.

> and can then use a trojaned library taking precendence over those 
> symbols to gain information

This is wrong.  You can't LD_PRELOAD a trojaned library to a suid binary
(unless it is in the standard paths and sgid I think) nor you can
use LD_LIBRARY_PATH to trick it in any way.

> or perform further exploitation." 
> 
> with the following patch:
> 
> http://www.gentoo.org/cgi-bin/viewcvs.cgi/sys-libs/glibc/files/glibc-sec-hotfix-20040804.patch?rev=1.1&content-type=text/vnd.viewcvs-markup 

BTW,
* Fixes a glibc bug where certain envvars are interpreted
  even if UNSECURE_ENVVARS says to drop them
is wrong, they are interpreted on purpose, but with caution if
__libc_enable_secure.

	Jakub