Re: LD_PRELOAD used with setuid programs (was Re: Fakeroot security problem)
Nobody should be able to run LD_PRELOAD with suid binaries. The issue with
nfslock can be solved differently as Joost has said. And being able to set
LD_PRELOAD on one machine and then rsh to exec a command on another
(and the other machine obeys the LD_PRELOAD!) seems to be another reason
to disable LD_PRELOAD. That raises a lot of security issues. If
nobody else will do it then I will upload a version that fixes the hole.
On 9 Feb 1998, James Troup wrote:
> Juan Cespedes <cespedes@debian.org> writes:
>
> > Yes, both ld-linux.so.2 and ld-linux.so.1 should be fixed; nobody
> > should be able to run a setuid program in a LD_PRELOAD environment.
> > At least, I can't find any reason to allow it, and many people could
> > use it to try to find exploits.
>
> But there _are_ reasons to do allow it (see below, and also add
> libnfslock to the list). If there weren't any someone would have
> presented these patches much earlier.
>
> ------- Start of forwarded message -------
> Message-ID: <Pine.SUN.3.94.980208153330.7034A-100000@dfw.dfw.net>
> Date: Sun, 8 Feb 1998 15:39:10 -0600
> Reply-To: Aleph One <aleph1@DFW.DFW.NET>
> From: Aleph One <aleph1@DFW.DFW.NET>
> Subject: Re: Another ld-linux.so problem
> To: BUGTRAQ@NETSPACE.ORG
>
> On Sat, 7 Feb 1998 carson@TLA.ORG wrote:
>
> > Yes. SOCKSifying stupid protocols that require binding ports <1024, for
> > example. Assuming you install libsocks5_sh.so in /usr/lib, you can do:
> >
> > $ (export LD_PRELOAD=/usr/lib/libsocks5_sh.so; rsh machine.outside.firewall
> > pwd)
> >
> > and have it work. This is basically what the runsocks script does.
>
> Another example: installing a library that overides mktemp, tempnam and
> other dangerous library functions with more secure ones. So the feature
> is indeed useful. The correct behavior should be for the dynamic linker
> to give up at the first error. Alternatively you should be able to
> configure such libraries via the configuration file instead of an
> environment variable. You cant do so now as far as I can tell.
>
> > --
> > Carson Gaspar -- carson@cs.columbia.edu carson@tla.org carson@cugc.org
> > http://www.cs.columbia.edu/~carson/home.html
> > Queen Trapped in a Butch Body
> >
>
> Aleph One / aleph1@dfw.net
> http://underground.org/
> KeyID 1024/948FD6B5
> Fingerprint EE C9 E8 AA CB AF 09 61 8C 39 EA 47 A8 6A B8 01
>
> ------- End of forwarded message -------
>
> --
> James
>
>
> --
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