way to set shell used for remote commands?

Jason Vas Dias jason.vas.dias at gmail.com
Thu Jan 22 02:36:05 AEDT 2015


Good day -

Please can OpenSSH provide some way of specifying which shell to use to
execute commands on a host.

For the account I need to use,  the user's password shell is not acceptable,
(a ten year old version of bash 3.0)
and cannot be changed without weeks or months of burocracy , if at all.

I built & installed the latest bash under that account, in the ~/bin directory,
but SSH will not use it.

Using the client OpenSSH version : 1:6.6p1-2ubuntu2 on a linux x86_64
Ubuntu 14.04.1 host,
if I try to specify which bash to use for an  SSH command like :
 $ ssh $account /home/${user}/bin/bash -c 'echo $BASH_VERSION; echo
$BASH_VERSION';
something very weird happens - only the second statement produces any
output .
If this is changed, we see only the first statement is run by the new shell,
and the second is run by the old shell:
  $ ssh $account  /home/${user}/bin/bash -c \
    'set | grep BASH_VERSION; echo $BASH_VERSION'
Produces the output:
    BASH_VERSION='4.3.30(1)-release'
    3.0.0(1)-release
So the first statement is run by the new shell, and the second by the old
shell.

This appears to be a major bug in OpenSSH - should I report it ?

Since OpenSSH provides no way to run commands with anything other
than the user's password shell,  it really needs to do so.

A simple patch would be to session.c, @ line 1746 :

/*
 * Get the shell from the password data.  An empty shell field is
 * legal, and means /bin/sh.
 */
shell = (pw->pw_shell[0] == 0) ? _PATH_BSHELL : pw->pw_shell;


One could do something like:

    char *sh;
    if ( (sh=getenv("SSH_SHELL") )!= NULL )
         shell = sh;
    else
         shell = (pw->pw_shell[0] == 0) ? _PATH_BSHELL : pw->pw_shell;


Or provide some configuration option  - this would probably have to
be per-server .

Is there any hope of getting the ability to specify which shell to run
remote commands with in a forthcoming OpenSSH release, or do
I need to apply my patch and maintain my own OpenSSH branch ?

Thanks & Regards,
Jason


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