openssh bugs - Nov 2009 - [Bug 1673] New: pseudoterminal option (-t) breaks standard out/error separation

https://bugzilla.mindrot.org/show_bug.cgi?id=1673

           Summary: pseudoterminal option (-t) breaks standard out/error
                    separation
           Product: Portable OpenSSH
           Version: 5.1p1
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ssh
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: raker1000 at yahoo.com


When connecting to run commands, standard error ends up mixed with
standard output when using the (-t) pseudoterminal option.
===================Here's an example without pseudoterminal option where it
is working
correctly, and the error messages from the server are captured by fd2
on the client:
---
$ ssh user at server 'uptime ; ls -l /blah' > out 2> err
user at server's password:

$ cat err
ls: cannot access /blah: No such file or directory

$ cat out
 05:07:09 up 14 days,  1:40,  4 users,  load average: 0.01, 0.02, 0.00
===================And here's an example with pseudoterminal option where
standard error
is mixed in with standard output, and the error messages from the
server are captured by fd1 on the client. The only error message that
went to fd2 was the error from the ssh client executable:
---
$ ssh -t user at server 'uptime ; ls -l /blah' > out 2> err
user at server's password:

$ cat err
Connection to elena closed.

$ cat out
 05:07:20 up 14 days,  1:40,  5 users,  load average: 0.01, 0.02, 0.00
ls: cannot access /blah: No such file or directory

===================I tested this from solaris8 to solaris8, from solaris8 to
redhat linux,
and from ubuntu linux to ubuntu linux, several versions of
client/server.

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https://bugzilla.mindrot.org/show_bug.cgi?id=1673

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX

--- Comment #1 from Damien Miller <djm at mindrot.org> 2009-11-21 14:52:44
EST ---
This is expected. When a pty is allocated, all of stdin, stdout and
stderr point to the pty (see "ls -l /proc/$$/fd" on Linux). Being on
the other side of the pty, sshd has no way to determine which fd the
child process issued the write() to. Changing the fd allocation so that
stderr was a pipe instead of a pty would be a significant departure
from standard practice and would probably break quite a few things.

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https://bugzilla.mindrot.org/show_bug.cgi?id=1673

--- Comment #2 from raker1000 at yahoo.com 2009-11-23 01:34:55 EST ---
(In reply to comment #1)
> This is expected. When a pty is allocated, all of stdin, stdout and
> stderr point to the pty (see "ls -l /proc/$$/fd" on Linux). Being
on
> the other side of the pty, sshd has no way to determine which fd the
> child process issued the write() to. Changing the fd allocation so that
> stderr was a pipe instead of a pty would be a significant departure
> from standard practice and would probably break quite a few things.

I see. I wasn't sure whether this was intended behavior. Thank you for
the prompt attention.

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https://bugzilla.mindrot.org/show_bug.cgi?id=1673

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #3 from Damien Miller <djm at mindrot.org> 2010-04-16 15:51:20
EST ---
Mass move of bugs RESOLVED->CLOSED following the release of
openssh-5.5p1

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