openssh unix dev - Nov 2008 - Axway XFB sftp server & no-more-sessions@openssh.com

Hello all,

First of all, thank you for such great software.

I have a bug (and a fix) to report for 5.1p:

The "Axway XFB.Gateway" SFTP server will drop sftp sessions initiated
from the OpenSSH 5.1p (HP-UX) sftp if it receives the "no-more-sessions at
openssh.com" flag.
It can be reproduced also with the sftp sessions initiated from a OpenSSH 5.1p
sftp on a Linux machine.

As a workaround we are using now "-oControlMaster=yes" for each sftp
connection in order to disable the sending of "no-more-sessions at
openssh.com" flag.

Can you please add for future versions in "compat.c" that for
connections to servers who identify themselves as "XFB.Gateway Unix" a
flag should be set that "no-more-sessions at openssh.com" is not sent
to that server ?

Thanks a lot !

excerpts from sftp -vvv (without "-oControlMaster=yes")
========...
debug1: Remote protocol version 2.0, remote software version XFB.Gateway Unix
debug1: no match: XFB.Gateway Unix
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.1p1+sftpfilecontrol-v1.2-hpn13v5
...
debug1: Authentication succeeded (publickey).
debug2: fd 5 setting O_NONBLOCK
debug2: fd 6 setting O_NONBLOCK
debug1: Final hpn_buffer_size = 2097152
debug1: HPN Disabled: 1, HPN Buffer Size: 2097152
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Requesting no-more-sessions at openssh.com
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug1: Sending subsystem: sftp
debug2: channel 0: request subsystem confirm 1
debug2: fd 4 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 32768 rmax 16384
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r660 i0/9 o0/0 fd 5/6 cfd -1)
 
debug3: channel 0: close_fds r 5 w 6 e 7 c -1
debug1: fd 0 clearing O_NONBLOCK
debug1: fd 1 clearing O_NONBLOCK
Connection to XX.XX.XX.XX closed by remote host.
Transferred: sent 2152, received 1088 bytes, in 0.1 seconds
Bytes per second: sent 16388.3, received 8285.6
debug1: Exit status -1
Connection closed
===========

On Tue, 18 Nov 2008, Partenie, Sergiu wrote:
> Hello all,
>
> First of all, thank you for such great software.
>
> I have a bug (and a fix) to report for 5.1p:
>
> The "Axway XFB.Gateway" SFTP server will drop sftp sessions
> initiated from the OpenSSH 5.1p (HP-UX) sftp if it receives the
> "no-more-sessions at openssh.com" flag It can be reproduced also
with the
> sftp sessions initiated from a OpenSSH 5.1p sftp on a Linux machine
>
> As a workaround we are using now "-oControlMaster=yes" for
> each sftp connection in order to disable the sending of
> "no-more-sessions at openssh.com" flag.
>
> Can you please add for future versions in "compat.c" that for
> connections to servers who identify themselves as "XFB.Gateway
Unix" a
> flag should be set that "no-more-sessions at openssh.com" is not
sent to
> that server ?
Due to bugs in other servers, OpenSSH 5.2 will not send this extension
message (nor the eow at openssh.com channel half-closed notification) to
any server that doesn't identify itself as OpenSSH. Vendors are required
to gracefully refuse messages that they do not understand, so the "Axway
XFB.Gateway" is actually what is at fault here.

If any other ssh vendors what to receive these messages, then they should
let us know so they can be whitelisted in compat.c

-d