Re: [PATCH v20 43/48] refs.c: move the check for valid refname to lock_ref_sha1_basic

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On Wed, Aug 20, 2014 at 10:49 AM, Jonathan Nieder <jrnieder@xxxxxxxxx> wrote:
> Hi,
>
> Ronnie Sahlberg wrote:
>> On Wed, Aug 20, 2014 at 7:52 AM, Michael Haggerty <mhagger@xxxxxxxxxxxx> wrote:
>
>>> I'm a little worried that abandoning *all* refname checks could open us
>>> up to somehow trying to delete a "reference" with a name like
>>> "../../../../etc/passwd".  Either such names have to be prohibited
>>> somehow, or we have to be very sure that they can only come from trusted
>>> sources.
>>
>> I only set this flag from builtin/branch.c so it should only be used
>> when a user runs 'git branch -D' from the command line.
>> All other places where we delete branches we should still be checking
>> the rename for badness.
>
> Right, this should be safe for 'git branch -D' and 'git update-ref -d'.
>
> But if we wanted to open it up in the future for 'git push --delete',
> too, then it would be a way to break out of the repository on hosts where
> people use git-shell instead of relying on filesystem permissions.  And
> that wouldn't be good.
>
> I think elsewhere git has some checks for "does this pathname fall in
> this directory".  Could that be reused here, too, to make sure the
> resolved path is under the resolved $GIT_DIR/refs directory?
>
> Alternatively, when a ref being deleted doesn't meet the
> 'check-ref-format' checks, would it make sense to check that it is one
> of the refs you can get by iteration?

Good idea! I will add such a check using the iterator.
That means that "we can git branch -D anything that shows up in the
iterator regardless if the ref is badly named or unresolvable" which
sounds like fairly sane semantics.

Thanks!

Ronnie
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