Proposing to host system-auth-agent in fdo
carlosg at gnome.org
Fri Oct 29 18:54:27 EEST 2004
On Mon, 2004-10-25 at 09:12 +0200, Alexander Larsson wrote:
> On Sun, 2004-10-24 at 17:33 +0200, Carlos Garnacho wrote:
> > On Mon, 2004-10-18 at 09:06 +0200, Alexander Larsson wrote:
> > > On Sat, 2004-10-16 at 20:48 +0200, Carlos Garnacho wrote:
> > >
> > > > Ok, the program that uses the API could still be affected by LD_PRELOAD,
> > > > but let's suppose the next scenario:
> > > >
> > > > Joe tries to do weird stuff, writes a .so file that replaces getuid()
> > > > calls to impersonate Frank and tries to run "rm -rf /", runs
> > > > control-center with LD_PRELOAD
> > > >
> > > > 1) system-auth-manager will still know which is the calling user, as it
> > > > isn't affected by LD_PRELOAD
> > > >
> > > > 2) system-auth-manager will check that user Joe is allowed to run the
> > > > "rm" command, if he isn't, the root password will be requested, and the
> > > > whole LD_PRELOAD won't be effective at all.
> > >
> > > So, you're agreeing that the binary-name check doesn't help much? (Since
> > > you brought up the uid check instead.)
> > I've just uploaded the 0.0.2 version  which fixes this problem by
> > linking statically the library by default (adding ~50KB to the binary
> > size), one can still LD_PRELOAD to override read() and write() calls,
> > but that problem is intrinsic to any graphical auth application.
> I'm not sure how this helps anything? Its very easy to write a shared
> library, that when LD_PRELOADed into an app runs before main() of the
> app is even called (using constructors) and takes total control.
> Basically you can write whatever application you want, doing whatever
> you want. But instead of running it as "hostile-binary" you run it so
> that it looks like whatever other binary you choose (e.g. /usr/bin/ls).
> So, any system that depends on what executable a process was started as
> is inefficient (at least if thats the only measure).
Well, consolehelper can be LD_PRELOADed too, currently it takes argv
and calls userhelper with that. Userhelper checks that the requested app
has an entry in /etc/security/console.apps/ and runs it if so.
I can LD_PRELOAD or code a bogus consolehelper in my path to run any
other allowed command.
BTW, thanks for your input :), I think I have a better auth
infrastructure idea, I'll propose it again when it's implemented.
> Alexander Larsson Red Hat, Inc
> alexl at redhat.com alla at lysator.liu.se
> He's a one-legged crooked shaman gone bad. She's a cosmopolitan goth socialite
> trying to make a difference in a man's world. They fight crime!
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