On Tue, Oct 9, 2018 at 7:13 PM Benjamin Peterson <benjamin@python.org> wrote:
> On Tue, Oct 9, 2018, at 17:14, Barry Warsaw wrote:
> > On Oct 9, 2018, at 16:21, Steven D'Aprano <steve@pearwood.info> wrote:
> > >
> > > On Tue, Oct 09, 2018 at 10:26:50AM -0700, Guido van Rossum wrote:
> > >> My feeling is that limiting it to strings is fine, but checking those
> > >> strings for resembling identifiers is pointless and wasteful.
> > >
> > > Sure. The question is, do we have to support uses where people
> > > intentionally smuggle non-identifier strings as keys via **kwargs?
> >
> > I would not be in favor of that. I think it doesn’t make sense to be
> > able to smuggle those in via **kwargs when it’s not supported by
> > Python’s grammar/syntax.
>
> Can anyone think of a situation where it would be advantageous for an implementation to reject non-identifier string kwargs? I can't.
One possibility is that it could foreclose certain security bugs from
happening. For example, if someone has an API that accepts **kwargs,
they might have the mistaken assumption that the keys are identifiers
without special characters like ";" etc, and so they could make the
mistake of thinking they don't need to escape / sanitize them.
Hm, that's not an entirely unreasonable concern. How would an attacker get such keys *into* the dict? One possible scenario would be something that parses a traditional web query string into a dict, passes it down through **kwds, and then turns it back into another query string without proper quoting. But the most common (and easiest) way to turn a dict into a query string is calling urlencode(), which quotes unsafe characters.
I think we needn't rush this (and when in doubt, status quo wins, esp. when there's no BDFL :-).