On Tue, Aug 14, 2018 at 11:04:06AM -0700, Brandon Williams wrote: > > I think this backwards-compatibility is necessary to avoid pain. But > > until it goes away, I don't think this is helping the vulnerability from > > 0383bbb901. Because there the issue was that the submodule name pointed > > back into the working tree, so this access() would find the untrusted > > working tree code and say "ah, an old-fashioned name!". > [...] > > Oh I know that this doesn't help with that vulnerability. As you've > said we fix it and now disallow ".." at the submodule-config level so > really this path is simply about using what we get out of > submodule-config in a more sane manor. OK, I'm alright with that as long as we are all on the same page. I think I mistook "this addresses the vulnerability" from your commit message the wrong way. I took it as "this patch", but reading it again, you simply mean "the '..' handling we already did". I do think eventually dropping this back-compatibility could save us from another directory-escape problem, but it's hard to justify the real-world pain for a hypothetical benefit. Maybe in a few years we could get rid of it in a major version bump. > > One interesting thing about url-encoding is that it's not one-to-one. > > This case could also be %2F, which is a different file (on a > > case-sensitive filesystem). I think "%20" and "+" are similarly > > interchangeable. > > > > If we were decoding the filenames, that's fine. The round-trip is > > lossless. > > > > But that's not quite how the new code behaves. We encode the input and > > then check to see if it matches an encoding we previously performed. So > > if our urlencode routines ever change, this will subtly break. > > > > I don't know how much it's worth caring about. We're not that likely to > > change the routines ourself (though certainly a third-party > > implementation would need to know our exact url-encoding decisions). > > This is exactly the reason why I wanted to get some opinions on what the > best thing to do here would be. I _think_ the best thing would probably > be to write a specific routine to do the conversion, and it wouldn't > even have to be all that complex. Basically I'm just interested in > converting '/' characters so that things no longer behave like > nested directories. I think we benefit from catching names that would trigger filesystem case-folding, too. If I have submodules with names "foo" and "FOO", we would not want to confuse them (or at least we should confuse them equally on all platforms). I doubt you can do anything malicious, but it might simply be annoying. That implies to me using a custom function (even if its encoded form ends up being understandable as url-encoding). -Peff
