[Bug 1179344] [NEW] ssh doesn't get pty; says "inappropriate ioctl for device"

[Todd A. Jacobs]

Public bug reported:

## Versions

    $ lsb_release -rd
    Description:    Ubuntu Saucy Salamander (development branch)
    Release:        13.10

    $ uname -a
    Linux emu 3.9.0-1-generic #5-Ubuntu SMP Wed May 8 20:52:16 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

    $ apt-show-versions -a openssh-server
    openssh-server 1:6.2p1-2 install ok installed
    openssh-server 1:6.2p1-2 saucy us.archive.ubuntu.com

## Problem

After a recent (accidental) upgrade to 13.10, recent updates to the
kernel seem to make inbound SSH connections problematic. Specifically,
the remote client is unable to connect to a login shell. This was
extremely difficult to diagnose, because all the client says is:

    $ ssh emu 
    Last login: Sun May 12 21:35:35 2013 from goldendelicious
    Shared connection to 192.168.1.127 closed.
    Connection to 192.168.1.127 closed by remote host.

Even with the verbose flag turned on (e.g. `-v` and `-vvv`) all you see
is that you connect, then get "debug1: Exit status -1" for no
discernable reason. The rest of the verbose output is completely
uninteresting However, there are other ways to debug this, as shown
below.

### SSH connection results in dumb terminal

    $ echo $TERM
    xterm-256color

    $ ssh emu /bin/echo \$TERM
    dumb

As you can see, openssh does not use the correct TERM environment
variable. However, manually setting TERM (e.g. `export TERM=vt100`)
doesn't solve the problem, because you don't actually have a pty. See
next section.

### Non-login shells work...sort of

    $ ssh emu /bin/bash -i
    bash: cannot set terminal process group (-1): Inappropriate ioctl for device
    bash: no job control in this shell
    emu:~$  echo $TERM
    echodumb
     $TERM
    emu:~$ tty
    tty
    not a tty

As you can see here, openssh is unable to open a tty or pty. If you try
to force it with `-t` or `-tt`, then it returns to the previous behavior
of simply closing the connection without explanation.

## Temporary Work-Around

One way to work around this problem is to use X-Forwarding to launch an
xterm as a login shell. For example:

    $ ssh emu xterm -e 'bash -l'

This works, assigns a pty, and otherwise results in a usable remote
connection, but is certainly not a substitute for having a working
non-X11 shell.

## Expected Behavior

1. OpenSSH should receive a pty on the remote host.
2. The TERM variable should be properly propogated.
3. There should be a more obvious way to debug this; openssh reports NOTHING of use in this situation, even with maximum verbosity.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: openssh-server 1:6.2p1-2
ProcVersionSignature: Ubuntu 3.9.0-1.5-generic 3.9.1
Uname: Linux 3.9.0-1-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.10-0ubuntu3
Architecture: amd64
Date: Sun May 12 21:40:41 2013
EcryptfsInUse: Yes
InstallationDate: Installed on 2011-10-15 (575 days ago)
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MarkForUpload: True
SourcePackage: openssh
UpgradeStatus: Upgraded to saucy on 2013-05-06 (6 days ago)

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug saucy uec-images

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https://bugs.launchpad.net/bugs/1179344

Title:
  ssh doesn't get pty; says "inappropriate ioctl for device"

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