[bug#46182] [PATCH] lint: Add 'check-git-protocol' checker.

[Simon Tournier <zimon.toutoune@gmail.com>]

Hi Maxim,

On Thu, 19 Oct 2023 at 22:22, Maxim Cournoyer <maxim.cournoyer@gmail.com> wrote:

> Thinking about this change though; why is it bad to fetch from git
> places?  There may be repos out there where it's the only offered way,
> and as long as we're talking fixed output derivations, it seems moot
> whether you use HTTPS, HTTP or X to retrieve the files (unless you are
> worried about your traffic being monitored, but that's not in scope, I'd
> say).

Why would not it be in scope?

Being able to strongly verify (sha256) that the content you fetch is the
data you expect does not imply that the protocol for communicating
cannot be exploited for other means.

Well, git:// protocol is not supported by well-known forges.  Quoting
Pro Git book:

        The Cons

        Due to the lack of TLS or other cryptography, cloning over
        git:// might lead to an arbitrary code execution vulnerability,
        and should therefore be avoided unless you know what you are
        doing.

        https://git-scm.com/book/en/v2/Git-on-the-Server-The-Protocols

And I do not have enough imagination to find a way to exploit the git://
protocol.  However, it appears to me a good practise to warn when this
protocol is used.  Somehow, a lint message is a recommendation – a good
practise – and not an absolute truth. :-)

In short, from my point of view, the general rule reads: avoid git://
protocol if you can.  Obviously, if you cannot because it is the only
offered way by some repositories, then let make an exception; but it
does mean that’s a good practise.

Cheers,
simon