Subject: bug#49714: closed (Re: bug#49714: 28.0.50; TRAMP burns CPU and has insufficient user reporting when using xxxx-sk SSH keys)

From: [email-masked] (GNU bug Tracking System)
Date: Thu, 09 Sep 2021 18:01:01 +0000

Your bug report

#49714: 28.0.50; TRAMP burns CPU and has insufficient user reporting when using xxxx-sk SSH keys

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
49714: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=49714
GNU Bug Tracking System
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Subject: Re: bug#49714: 28.0.50; TRAMP burns CPU and has insufficient user reporting when using xxxx-sk SSH keys
From: Dima Kogan <[email-masked]>
To: Michael Albinus <[email-masked]>
Cc: [email-masked]
Date: Thu, 09 Sep 2021 11:00:11 -0700
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi Michael. Sorry I haven't replied to this. I think the current code is
good, and I'm closing the bug. If anything else pops up in this area, we
can use a new ticket. Thank you very much!

Subject: 28.0.50; TRAMP burns CPU and has insufficient user reporting when using xxxx-sk SSH keys
From: Dima Kogan <[email-masked]>
To: [email-masked]
Date: Fri, 23 Jul 2021 15:05:59 -0700
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi.

I have a yubikey, a hardware encryption device. For the purposes of SSH,
the SSH private key is split betweek a file on disk (.ssh/id_ed25519_sk)
and some data on the yubikey. When logging into an SSH server, the
interaction generally looks like this:

  client$ ssh ADDRESS

  Enter passphrase for key '/home/dima/.ssh/id_ed25519_sk':
  [the user enters the passphrase; not echoed to the console]

  Confirm user presence for key ED25519-SK XXXXXXXXXXXXXXX
  [the user physically touches the yubikey with their finger]

  server$
  [we are logged-in]

In TRAMP it looks like this:

   C-x C-f
   /ssh:ADDRESS:

   [Emacs asks for the passphrase. This is good]

   [Now we have a problem]

Emacs now spins the CPU, saying nothing. Internally, ssh is asking for
the user to touch the yubikey, but TRAMP is not communicating this
information. I know I should touch the yubikey, and if I do that, TRAMP
succeeds. There are two bugs here:

1. Emacs should not be spinning the CPU. This is actually an old bug. I
   usually see this with normal SSH connections, but it only happens
   during the login sequence, which isn't very long. In THIS case the
   login sequence could be longer. In any case, we shouldn't be
   spinning.

2. Emacs should relay whatever ssh is saying (i.e. "Confirm user
   presence...") to the user

Thanks!

I'm using emacs built from source on 2021-07-16. I'm pretty sure the