openssh-SNAP-20001207 scp "Bad file descriptor" sort-of work-around

[James]

Damien wrote:

> Do you have something in your profile or shell rc which causes text to
> be displayed on non-interactive logins?

No, but there's part of where the problem is.  scp seems to read /etc/passwd
on the _target_ server machine (as well as on the client machine) to
determine the user's default shell on that target machine, and then invokes
a non-login _interactive_ shell, NOT a non-interactive shell.

I know this from changing the various scripts and the /etc/passwd login
shell for the user (root). Where man bash has

INVOCATION
       A login shell is one whose  first  character  of  argument
       zero is a -, or one started with the -login flag.

       An  interactive shell is one whose standard input and out
       put are both connected  to  terminals  (as  determined  by
       isatty(3)), or one started with the -i option.  PS1 is set
       and $- includes i if bash is interactive, allowing a shell
       script or a startup file to test this state.

       Login shells:
         On login (subject to the -noprofile option):
               if /etc/profile exists, source it.

               if ~/.bash_profile exists, source it,
                 else if ~/.bash_login exists, source it,
                   else if ~/.profile exists, source it.

         On exit:
               if ~/.bash_logout exists, source it.

       Non-login interactive shells:
         On startup (subject to the -norc and -rcfile options):
               if ~/.bashrc exists, source it.

My ~/.bashrc normally starts with "source /etc/profile", which was what
actually generated the text, and the "sshd[3381]: error: select: Bad file
descriptor" message in the log file.  (I noticed that if I simply put echo
"a bunch of random characters asdlfkjsd" into ~/.bashrc, that will also kill
scp, but - and only in this particular case - without the "Bad file
descriptor" error message.)

I suppose I can try to modify ~/.bashrc to check how it's being called, but...

Could this be a problem with bash? or a problem with how sshd calls the
login shell?

 # echo $BASH_VERSION
 1.14.7(1)


> What does "ssh localhost true" say?

On the client machine:

# ssh localhost true
ssh_exchange_identification: Connection closed by remote host

with "sshd[25040]: refused connect from 127.0.0.1" in the log file.

On the server machine, the same.  Also the same if 127.0.0.1 is added to
/etc/hosts.allow for sshd.  Also the same for a non root user.


> You mustn't have junk being printed for non-interactive sessions.

What's the easiest way to invoke a for-sure non-interactive session for
testing?

Again, please Cc me on any response, as I'm not subscribed to the list.
Thanks.


James Feeney