Re: [PATCH v3 1/3] t: document regression git safe.directory when using sudo

[Carlo Arenas <carenas@gmail.com>]

On Mon, May 9, 2022 at 1:21 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
> On 05/05/2022 19:33, Junio C Hamano wrote:
> > Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> >
> >> Hmm. I would like to suggest that we can side-step all of these issues
> >> (and the ones I outline below) by considering a similar approach to the
> >> one Stolee took in t0033: use one or more `GIT_TEST_*` environment
> >> variables to pretend the exact scenario we want to test for.
> >
> > Perhaps this may be a way to pretend we are running a command under
> > 'sudo'?
> >
> >       test_pretend_sudo () {
> >              GIT_TEST_PRETEND_GETEUID_RETURNING_ROOT=1 \
> >           GIT_TEST_PRETEND_LSTAT_RETURNING_ROOT=root/p \
> >                  SUDO_UID=0 "$@"
> >       }
> >
> >       test_expect_success 'access root-owned repository as root' '
> >               mkdir root/p &&
> >               git init root/p &&
> >               test_pretend_sudo git status
> >       '
> >
> > That way we can avoid having to run "chown" while preparing for the
> > test fixture, and running "git status" under root, but I am not sure
> > if we want our shipped production binaries to have these "pretend"
> > knobs.
>
> Lets ask ourselves "How could an attacker use these knobs to facilitate
> an attack?".

That is not the question raised by having those "pretend" knobs in the
production binary, but instead how can an attacker abuse them to get
themself and UID he doesn't have and therefore additional access.

The fact that the current code requires you to be root to even enable
the logic makes it more difficult to use SUDO_UID that way, because if
you already got root, you don't really need them, but take into
consideration that this discussion starts with (how can we run these
things as a the test user and avoid sudo, hence root).

Carlo