Re: [PATCH] gpg-interface: reflect stderr to stderr

From: Jeff King <peff@peff.net>
Date: Sep 7, 2016, 08:39 UTC
Message-ID: <20160907083947.b7q7ebe62xsr6447@sigill.intra.peff.net>
In-Reply-To: <655b42d8-baa9-e649-2b3c-5b7bfc914bc5@drmicha.warpmail.net>

On Wed, Sep 07, 2016 at 10:27:34AM +0200, Michael J Gruber wrote:

> Now, I can't reproduce C on Linux[*], so there is more involved. It
> could be that my patch just exposes a problem in our start_command()
> etc.: run-command.c contains a lot of ifdefing, so possibly quite
> different code is run on different platforms.

Maybe, though my blind guess is that it is simply that on Linux we can open /dev/tty directly, and console-IO on Windows is a bit more complicated.

You might also check your GPG versions; between gpg1.x and gpg2, the passphrase input handling has been completely revamped.

> It would be great if someone with a Windows environment could help our
> efforts in resolving issue C, by checking what is actually behind[**]: I
> can't believe that capturing stderr keeps gpg from reading stdin, but
> who knows. Maybe Jeff of pipe_command() fame? I'll put him on cc.

I know nothing about Windows, but I'd be surprised if gpg is reading from stdin, as opposed to /dev/tty. It's probably more to do with how gpg finds the "tty" on Windows (presumably it looks at stderr for that).

Anyway, I wrote pipe_command() in such a way as to be prepared for exactly this kind of thing, so it would be trivial to extend it to an extra descriptor. The trouble is that run_command() doesn't understand anything except stdin/stdout/stderr. We can open an extra pipe() before calling run_command(), and make sure it is not marked CLOEXEC. I don't know if there are other portability concerns, though.

-Peff