openssh bugs - Oct 2017 - [Bug 2797] New: ssh swallows end-of-file on output

https://bugzilla.mindrot.org/show_bug.cgi?id=2797

            Bug ID: 2797
           Summary: ssh swallows end-of-file on output
           Product: Portable OpenSSH
           Version: 7.6p1
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: openssh at davidnewall.com

Ssh duplicates FILENO_STDOUT and FILENO_STDERR, thus there are two
descriptors for each of those files.  When the remote program closes
its stdout or stderr, the remote sshd sends the appropriate message to
the local ssh which responds by closing the duplicate descriptor, but
the original descriptor remains open.  A program reading from ssh's
stdout (or stderr) cannot tell that the remote program has closed the
file.

This is what should happen:

$ sh -c 'exec cat >&- 2>&-; sleep 5' | { read s || echo
eof; }
eof
[then 5 second pause]

This is what happens using ssh:

$ ssh localhost 'exec >&- 2>&-; sleep 5' | { read s ||
echo eof; }
[5 second pause]
eof

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org

--- Comment #1 from Damien Miller <djm at mindrot.org> ---
Created attachment 3073
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3073&action=edit
transfer stdout to channel

This transfers ownership of stdout to the session channel, clobbering
the original STDOUT_FILENO with /dev/null to ensure that nothing writes
to it after any subsequent fds are opened, since they could be
allocated fd=1.

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #3073|0                           |1
        is obsolete|                            |

--- Comment #2 from Damien Miller <djm at mindrot.org> ---
Created attachment 3074
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3074&action=edit
attempt 2 - delay clobbering of stdout until after LocalCommand

Previous patch was incorrect - LocalCommand may write to stdout, so
delay clobbering STDOUT_FILENO until it has completed.

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David Newall <openssh at davidnewall.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #3 from Damien Miller <djm at mindrot.org> ---
Hang on - the patch isn't committed yet!

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |2782


Referenced Bugs:

https://bugzilla.mindrot.org/show_bug.cgi?id=2782
[Bug 2782] Tracking bug for OpenSSH 7.7 release
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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Damien Miller <djm at mindrot.org> ---
Patch has been committed and will be in openssh-7.7

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Damien Miller <djm at mindrot.org> changed:

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

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
Close all resolved bugs after release of OpenSSH 7.7.

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dearvoid at gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dearvoid at gmail.com

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