Re: [PATCH 0/3] --end-of-options marker

["brian m. carlson" <sandals@crustytoothpaste.net>]

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On 2019-08-06 at 23:43:20, Jeff King wrote:
> On Tue, Aug 06, 2019 at 10:58:53PM +0000, brian m. carlson wrote:
> > Sorry, I hadn't had a chance to look at this series in depth, but I was
> > wondering: could we not just accept two separate "--" arguments, and if
> > there are two of them, interpret the first with the traditional meaning
> > and the second with the Git-specific meaning? That would be much more
> > intuitive for folks, although I suspect it would take a little more work
> > in the options parser.
> 
> That also crossed my mind, but I think it opens up some complicated
> corner cases.  For instance, if I'm parsing left-to-right and see "--",
> how do I know which separator it is meant to be? I think the only rule
> that makes sense is that you must have two "--", like:
> 
>   git rev-list [options] -- [revs] -- [paths]

I was assuming that we wouldn't have a huge number of command-line
arguments and we'd check ahead, although that could of course cause some
pain when used with xargs, I suppose, especially on Linux with its huge
ARG_MAX.

> but that means parsing the whole thing before we can interpret any of
> it. What kinds of tricks can an attacker play by putting "--" in the
> revs or paths areas? E.g., what does this mean:
> 
>   # expanded from "git rev-list -- $revs -- $paths"
>   git rev-list -- --foo -- -- --bar --
> 
> I think if we at least choose the left-most "--" as the official
> end-of-options then they can't inject an option (they can only inject a
> rev as a path). I guess that's the same as with --end-of-options. But it
> somehow feels less clear to me than a separate marker.

I suppose if there's more than two, then interpret the first one as the
end-of-options marker, the second one in the traditional way, and any
subsequent ones as pathspecs matching the file "--". Writing such a
command line would be silly, but we'd fail secure.

> It also doesn't allow this:
> 
>   # allow paths and revs, with optional separator, but no more options
>   git rev-list --end-of-options "$@"
> 
> though I'm not sure whether anybody cares.

That's a good point. I don't have a strong view either way, but I
thought I'd ask about alternatives.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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