openssh bugs - Jul 2024 - [Bug 3714] New: sftp fails in one direction

https://bugzilla.mindrot.org/show_bug.cgi?id=3714

            Bug ID: 3714
           Summary: sftp fails in one direction
           Product: Portable OpenSSH
           Version: 9.2p1
          Hardware: ARM64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: sftp
          Assignee: unassigned-bugs at mindrot.org
          Reporter: hp4everything at googlemail.com

Created attachment 3827
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3827&action=edit
terminal messages client and server with option -vvvv

I have 2 Raspberry Pi with Debian-Linux
host1 Raspberry Pi3 with Linux 6.1.0-17-arm64
host2 Raspberry Pi4 with Linux 6.6.31+rpt-rpi-v8

On both the official openssh 9.2p1 with identical binaries

ssh works fine between both machines in both directions

sftp works fine with host2=client and host1=server

But sftp immediately closes the connection in the other direction!

In the error case there appear additional messages related to
pseudoterminals and a SIGCHILD-event is reported on the server.

Sorry, I'm not very familiar with pseudo-terminals. I've only read that
TIOCSCTTY might require special access rights (CAP_SYS_ADMIN). So maybe
there a some Security-related modern Linux-configurations required for
sftp, which I've not been able to find.  


Attached please find terminal dbg-messages in the error-case
(host1=sftp-client,host2=server) 
and the ok-case 
(host2=sftp-client,host1=server)

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https://bugzilla.mindrot.org/show_bug.cgi?id=3714

Damien Miller <djm at mindrot.org> changed:

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

--- Comment #1 from Damien Miller <djm at mindrot.org> ---
Unfortunately the logs are not complete enough to see what's happening,
but these lines are suspect:
> debug2: channel_input_open_confirmation: channel 0: callback done
> debug2: channel 0: open confirm rwindow 0 rmax 32768
> debug3: receive packet: type 99
> debug2: channel_input_status_confirm: type 99 id 0
> debug2: PTY allocation request accepted on channel 0
> debug2: channel 0: rcvd adjust 2097152
> debug3: receive packet: type 99
> debug2: channel_input_status_confirm: type 99 id 0
> debug2: subsystem request accepted on channel 0
sftp should never request a PTY and doing so will almost certainly
break it. Do you have a ~/.ssh/config or /etc/ssh/ssh_config that has
RequestTTY set?

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https://bugzilla.mindrot.org/show_bug.cgi?id=3714

Hans-Peter <hp4everything at googlemail.com> changed:

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

--- Comment #2 from Hans-Peter <hp4everything at googlemail.com> ---
Sorry, my fault 
I didn't notice the "RequestTTY=force" in one of the config-Files.
Obviously this was responsible for closing the connection.

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