bug#26835: 26.0.50; url-retrieve no longer raises certificate errors

[Lars Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> It repros in `emacs -Q', just set:
>> 
>> (setq gnutls-verify-error t)
>> (url-retrieve-synchronously "https://wrong.host.badssl.com/")
>> 
>> In Emacs 25.2, this causes an error to be thrown when you use
>> url-retrieve, in 26, it silently proceeds.
>
> That's because we now perform GnuTLS negotiation asynchronously,
> without blocking.

(As an aside, perhaps url-retrieve-synchronously should be opening the
socket with :nowait nil?)

>   status = p->status;
>   if (CONSP (status))
>     status = XCAR (status);
>
> which loses the error message, leaving just 'failed'.  So
> url-retrieve-synchronously silently exits, and doesn't even have the
> info that could cause it to signal an error.
>
> IOW, the problem is not that the connection proceeds -- it does not.
> The problem is that it fails silently without telling the caller what
> caused the failure.
>
> I'll CC Lars, who introduced the non-blocking connections.

Good analysis.  I'll try to have a look at this soonish (and make it
report the error properly) unless somebody else beats me to it.

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