Question

Cannot connect to sFTP server with subsystem internal-sftp

Asked by: gaffie

We have a linux server with sshd configured and also use sFTP. The connection used to work, but after a server reset, the sFTP cannot connect anymore.

Nothing in config files has changed before the reset, so it is very strange.

For sFTP we have in our sshd_config file:
Subsystem sftp internal-sftp

when connecting with filezilla for example, the debug messages say:
Fatal: Unable to initialise SFTP on server: could not connect.

the secure log file on the linux server says:

subsystem request for sftp
error: subsystem: cannot stat internal-sftp: No such file or directory
subsystem request for sftp failed, subsystem not found

sshd is started. ssh with putty works correctly.

I do not know what file or directory is not found in the error message. also setting a higher debug level in sshd_config did not reveal this.

iptables is disabled, selinux is disabled.

I have run out of options. I hope somebody has any good advice in this.

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Asked On
2009-09-02 at 08:46:01ID24701729
Tags

internal-sftp

,

ssh

,

sshd

,

sftp

,

sshd_config

Topics

SSH / Telnet Software

,

FTP Servers

,

Linux

Participating Experts
2
Points
250
Comments
12

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Answers

 

by: mrcustardPosted on 2009-09-02 at 09:08:55ID: 25242520

I think that your config file should have this at the bottom - at least if your using Red Hat.

Subsystem       sftp    /usr/libexec/openssh/sftp-server

 

by: mrcustardPosted on 2009-09-02 at 09:10:10ID: 25242539

Can you post your linux version and config file?

 

by: arulkumarabiPosted on 2009-09-02 at 09:26:40ID: 25242690

have u used some other sftp client like winscp?

 

by: arulkumarabiPosted on 2009-09-02 at 09:27:09ID: 25242695

test it with some other sftp client

 

by: gaffiePosted on 2009-09-02 at 09:47:15ID: 25242904

I tried WinSCP, which can connect, but still the logfiles give the error message.
Also locally on server with commandline: sftp -v user@localhost cannot connect, same message as filezilla.

Config included. Linux version include.

using winscp is not an option, as our client is using it in a script to schedule uploads.

***************sshd_config********
**********************************
#       $OpenBSD: sshd_config,v 1.73 2005/12/06 22:38:28 reyk Exp $
 
# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.
 
# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin
 
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.
 
 
Protocol 2
ListenAddress 0.0.0.0
 
SyslogFacility AUTHPRIV
 
ChallengeResponseAuthentication no
 
GSSAPIAuthentication yes
GSSAPICleanupCredentials yes
 
UsePAM yes
 
# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL
X11Forwarding yes
 
#Subsystem   sftp    /usr/libexec/openssh/sftp-server
Subsystem sftp  internal-sftp
 
***************linux version********
**********************************
Linux version 2.6.18-128.el5 (mockbuild@builder10.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)) #1 SMP Wed Jan 21 10:41:14 EST 2009
 
***************Win SCP connection log on server ********
**********************************
winscp
Sep  2 18:37:20 sshd[26720]: pam_unix(sshd:session): session opened for user username by (uid=0)
Sep  2 18:37:20 sshd[26724]: subsystem request for sftp
Sep  2 18:37:20 sshd[26724]: error: subsystem: cannot stat internal-sftp: No such file or directory
Sep  2 18:37:20 sshd[26724]: subsystem request for sftp failed, subsystem not found
                                              
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by: mrcustardPosted on 2009-09-02 at 10:48:25ID: 25243600

Are you trying to do a CHROOT JAIL?

 

by: gaffiePosted on 2009-09-02 at 11:07:36ID: 25243804

yes we're locking users in their home folder.

 

by: gaffiePosted on 2009-09-02 at 11:41:04ID: 25244164

seems I forgot to uncheck the " fallback to SCP?" in WinSCP. after unchecking, winscp also fails:

Cannot initialize SFTP protocol. Is the host running a SFTP server?

 

by: mrcustardPosted on 2009-09-02 at 11:52:03ID: 25244295

Do you not need the following lines after "Subsystem sftp  internal-sftp" in your config file?


Match Group sftponly
        ChrootDirectory %h
        ForceCommand internal-sftp
        AllowTcpForwarding no

 

by: gaffiePosted on 2009-09-02 at 12:23:04ID: 25244616

After doing this:

Match Group sftponly
        ChrootDirectory %h
        ForceCommand internal-sftp
        AllowTcpForwarding no

I got errormessages. So it seems openssh v4.3 is installed.

Switched to :
Subsystem       sftp    /usr/libexec/openssh/sftp-server

Now I can connect with sftp correctly.

So this is ok!

The weird thing now is: how is it possible it worked before the server restart. Because I did not change any configuration options?





 

by: mrcustardPosted on 2009-09-02 at 13:01:50ID: 25244967

Well, if it got changed either by someone else - or by a tool that you were using perhaps? If it's working now ... that's great!

 

by: gaffiePosted on 2009-09-05 at 00:18:23ID: 31623957

Thank you.

20120131-EE-VQP-002

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