Re: PCRE v2 compile error, was Re: What's cooking in git.git (May 2017, #01; Mon, 1)

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

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Hi,

On Tue, 9 May 2017, brian m. carlson wrote:

> On Tue, May 09, 2017 at 02:00:18AM +0200, Ævar Arnfjörð Bjarmason wrote:
> > On Tue, May 9, 2017 at 1:32 AM, brian m. carlson
> > <sandals@crustytoothpaste.net> wrote:
> > > PCRE and PCRE2 also tend to have a lot of security updates, so I
> > > would prefer if we didn't import them into the tree.  It is far
> > > better for users to use their distro's packages for PCRE, as it
> > > means they get automatic security updates even if they're using an
> > > old Git.
> > >
> > > We shouldn't consider shipping anything with a remotely frequent
> > > history of security updates in our tree, since people very
> > > frequently run old or ancient versions of Git.
> > 
> > I'm aware of its security record[1], but I wonder what threat model
> > you have in mind here. I'm not aware of any parts of git (except maybe
> > gitweb?) where we take regexes from untrusted sources.
> > 
> > I.e. yes there have been DoS's & even some overflow bugs leading code
> > execution in PCRE, but in the context of powering git-grep & git-log
> > with PCRE this falls into the "stop hitting yourself" category.
> 
> Just because you don't drive Git with untrusted regexes doesn't mean
> other people don't.

Or other applications.

> It's not a good idea to require a stronger security model than we
> absolutely have to, since people can and will violate it.  Think how
> devastating Shellshock was even though technically nobody should provide
> insecure environment variables to the shell.
> 
> And, yes, gitweb does in fact call git grep. That means that git grep
> must in fact be secure against untrusted regexes, or you have a remote
> code execution vulnerability.

And not only grep is affected. Think HEAD^{/<regex>}. There are plenty of
sites where you are allowed to specify revs in a freer form than SHA-1s.

Having said that, I do like the prospect of a faster git grep.

Hopefully there will be a way to make use of PCRE that can be switched
off? Like, a compile-time replacement of the regex API backed by PCRE v2
*iff* PCRE v2 is used for building?

Ciao,
Dscho