bug#24490: 25.1; restclient no longer sends auth header upon redirect

[Lars Ingebrigtsen <larsi@gnus.org>]

Alain Picard <alain@gocatch.com> writes:

> Dear Maintainers,
>
> In emacs 25.1,
> the code in url-http.el, line 638, states:
>
>   ;; Do not automatically include an authorization header in the
>   ;; redirect.  If needed it will be regenerated by the relevant
>   ;; auth scheme when the new request happens.
>   (setq url-http-extra-headers
> (cl-remove "Authorization"
>    url-http-extra-headers :key 'car :test 'equal))
>
> I suspect this automatic regenration does not occur.

I think this code is basically correct -- if the auth scheme has added
something to url-http-extra-headers, then that has to be removed when
doing the redirect, because otherwise we might be sending the auth to a
completely wrong server, with the security implications of that.

> Problem: I am using restclient.el, and hitting a server which
> issues a redirect, and I receive a 400 Forbidden response because
> the redirected call does not receive the authentication header
> (I can see this from the log of my server).

I think this must be a bug in restclient.el -- it should instead use an
auth scheme that re-adds the Authorization header.

I think.  The URL interface is pretty vague here, as it is with many
other things...

Hm...

Reading

(defun url-http-create-request ()
[...]
	 (auth (if (cdr-safe (assoc "Authorization" url-http-extra-headers))
		   nil
		 (url-get-authentication (or
					  (and (boundp 'proxy-info)
					       proxy-info)
					  url-http-target-url) nil 'any nil)))

the auth is never added to `url-http-extra-headers', so perhaps that's
not correct anyway -- it should be possible for the user to put
Authorization in `url-http-extra-headers', and then have that be heeded
even over the redirect.

I've added Thomas to the CCs; perhaps he has some insights here.  (Also
see Bug#21350.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no