Re: [PATCH 0/4] credential: documentation updates for maint

[Jeff King <peff@peff.net>]

On Thu, May 07, 2020 at 02:23:48PM -0700, Carlo Marcelo Arenas Belón wrote:

> On Thu, May 07, 2020 at 04:59:09PM -0400, Jeff King wrote:
> > On Wed, May 06, 2020 at 04:28:48PM -0700, Carlo Marcelo Arenas Belón wrote:
> > 
> > > Subject: [RFC PATCH 5/4] credential: document encoding assumptions for values
> > > 
> > > Because of the similarity on the names of the keys with what is defined
> > > in RFC3986 is easy to assume the same rules would apply here.
> > > 
> > > Make sure that the format and encoding is well defined to avoid helper
> > > developers assuming incorrectly.
> > 
> > I'm not sure this really clarifies anything, because it just says "no
> > assumptions can be made". Which I guess is a statement, but I'm not sure
> > what I'd do with it as a helper developer.
> 
> not sure what part of the added lines you are referring to but I am happy
> to provide some examples of what I would expect to clarify below from
> what I'd seen from some helpers that I'd read the code from recently.
> 
> as an example, I would expect the helper developer to start checking for
> the locale and calling iconv in cases where it is not using utf-8, before
> sending it to a storage that requires that (ex: osxkeychain), or utf-16
> (maybe in windows).
> 
> osxkeychain will probably also check for protocol in a case insensitive
> way to make sure it is not ignoring credentials that are not all lowercase
> as it does now.

Those things all seem reasonable. I just meant that reading:

  No assumptions of case insensitivity can be made on their contents and
  if a specific encoding is required (e.g. "UTF-8") then the byte
  contents should be re-encoded before use.

didn't point me in a useful direction there. Reading it again, I'm still
not sure if you're trying to say that helpers should match protocols
case-insensitively or not. And TBH, I don't think it matters that much.
It's a quality-of-implementation issue for helpers, and if nobody is
complaining about their behavior, does it really matter? I'd be more
concerned if doing the wrong thing involved a security vulnerability,
but the worst case with case-insensitivity is probably that they _fail_
to match a credential when they should.

Likewise for weird encodings, unless an attacker can somehow come up
with a hostname byte sequence that a helper mistakes for another
legitimate hostname, _and_ that can be used sensibly by git or curl.

-Peff