tramp (2.2.6-24.3); connecting through socks and ssh hangs without prompt

[Dennis van Dok]

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Content-Type: text/plain


I'm trying to connect to a host (bosui.nikhef.nl) that can only be
reached through a bastion host (login.nikhef.nl). To that end, I've
started an ssh command with a dynamic port forward like this:

  ssh -D 2020 -vvv login.nikhef.nl

I can now use this to make a hop:

  ssh -o "ProxyCommand /bin/nc -x localhost:2020 %h %p" bosui.nikhef.nl

which allows me to log in (using my public key and ssh-agent
interaction).

I've got my agent set up to prompt for key use:

  ssh-add -c

Now I'm trying to connect with tramp from within emacs:

  C-x C-f /socks:localhost#2020|ssh:bosui.nikhef.nl:/

I can see this opens a connection through the socks proxy. When running
the ssh server in debug mode, the last line of output reads:

  Connection from 192.16.185.143 port 34502

Normal interactions would follow with something like

  debug1: Client protocol version 2.0; client software version
  OpenSSH_6.0p1 Debian-4+deb7u2

But I don't see this in the tramp case.

The traces from the tramp debug buffer suggest that tramp is expecting
to see prompts, but clearly the session is not at that stage yet (there
has been no key exchange for instance, let alone an agreement on the
authentication protocol). It seems to hang at the transparent ssh
connection it tries to set up through localhost, where emacs plays the
role of netcat in the example above.

Emacs  : GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.8.6)
 of 2013-12-22 on brahms, modified by Debian
Package: tramp (2.2.6-24.3)

current state:
==============

(The only buffer with any content was *debug tramp/ssh bosui.nikhef.nl*,
which you will find attached. The others were empty.)


State could not be dumped due to the following error:

(invalid-read-syntax #)

You should still send this bug report.
(setq
 buffer-name "*tramp/socks address@hidden"
 )

(setq
 buffer-name "*tramp/ssh bosui.nikhef.nl*"
 )

(setq
 buffer-name "*tramp/aux address@hidden <127.0.0.1:54154>"
 )

load-path shadows:
==================

This is a special notion of the `gnus/message' package.  If you
use another mail agent (by copying the contents of this buffer)
please ensure that the buffers are attached to your email.


--=-=-=
Content-Type: text/plain
Content-Disposition: attachment
Content-Description: *tramp/socks address@hidden


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Content-Type: text/plain
Content-Disposition: attachment
Content-Description: *tramp/ssh bosui.nikhef.nl*


--=-=-=
Content-Type: text/plain
Content-Disposition: attachment
Content-Description: *tramp/aux address@hidden <127.0.0.1:54154>


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Content-Type: text/plain
Content-Disposition: attachment
Content-Transfer-Encoding: 8bit
Content-Description: *debug tramp/ssh bosui.nikhef.nl*

;; GNU Emacs: 24.3.1 Tramp: 2.2.6-24.3 -*- mode: outline; -*-
16:35:56.428875 tramp-maybe-open-connection (3) # Opening connection for 
bosui.nikhef.nl using ssh...
16:35:56.429229 tramp-compute-multi-hops (5) # Add proxy ("bosui\.nikhef\.nl" 
"nil" "/socks:localhost#2020:")
16:35:56.431764 tramp-gw-open-connection (4) # Opening auxiliary process 
`*tramp/aux address@hidden
-- 
D.H. van Dok :: System administrator :: www.nikhef.nl/grid ::
Phone +31 20 592 22 28 :: http://www.nikhef.nl/~dennisvd/

debug-tramp
Description: Binary data