On Mon, Jun 24, 2013 at 09:24:29AM -0700, Junio C Hamano wrote:
> Fraser Tweedale <fr...@frase.id.au> writes:
> > The fact that the git transport has no end-to-end security is easily
> > overlooked.  Add a brief security notice to the "GIT URLS" section
> > of the documentation stating that the git transport should be used
> > with caution on unsecured networks.
> >
> > Signed-off-by: Fraser Tweedale <fr...@frase.id.au>
> > ---
> >  Documentation/urls.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/urls.txt b/Documentation/urls.txt
> > index 3ca122f..c218af5 100644
> > --- a/Documentation/urls.txt
> > +++ b/Documentation/urls.txt
> > @@ -11,6 +11,9 @@ and ftps can be used for fetching and rsync can be used 
> > for fetching
> >  and pushing, but these are inefficient and deprecated; do not use
> >  them).
> >  
> > +The git protocol provides no end-to-end security and should be used
> > +with caution on unsecured networks.
> Is this necessary?
> I thought we already say the git protocol does not even authenticate
> elsewhere in the document, and if not, I think it is a sensible
> thing to say here.  And once it is done, I doubt it is necessary to
> bring up a narrower concept such as "end-to-end security" which
> requires a lot more than authentication.
Certainly in this part of the documentation there is no mention of
(lack of) authentication or security concerns.  git-daemon(1) does
mention the lack of authentication in the SERVICES/receive-pack

Once you are aware that the git transport is insecure it seems
obvious in hindsight, but even as a security-minded person I simply
overlooked this until recently.  A brief note in the GIT URLS
section (which is included in the man pages for a number of
essential commands) would have brought this to my attention much

Junio, do you prefer the following more generic wording?  If so I
will re-roll the patch (also note s/protocol/transport/ which is
more appropriate, I think).

 The git transport is insecure and should be used with caution on
 unsecured networks.

> The only thing git protocol ensures is that the receiving end
> validates that what is fetched from an unknown server, and what is
> pushed by an unknown pusher, is internally consistent.
> If you allowed a push over the git protocol by enabling the
> receive-pack service in "git daemon" (not recommended), you may
> allow anonymous users to delete branches and to do other funky
> things unless you protect your repository with pre-receive hook, but
> that won't corrupt the repository (of course, deleting all the refs
> may make the repository an empty but not corrupt one, which is just
> as unusable as a corrupt one, so there may not be a huge practical
> difference).  If you fetched from an unauthenticated server,
> possibly with MITM, over the git protocol, you may end up getting
> something you did not ask for, but the resulting history in your
> repository would still be internally consistent (the commits may be
> malicious ones, of course, but that is what signed tags are there to
> protect you against).
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