[xubuntu-users] Failure to Connect SFTP Error

[fred roller]

you could also try to fire Filezilla from cli with verbos turned up and
piped to a log file locally.  May uncover a clue.  Since you are connecting
via ssh you might try cli sftp connection as well to help isolate program
issue or system issue.

-- Fred

On Thu, Jun 1, 2017 at 6:13 PM, Peter Flynn <peter at silmaril.ie> wrote:

> On 06/01/2017 09:27 PM, Rog wrote:
> > I rely on Filezilla to transfer files to my hosting service but it no
> > longer works. It fails at the very beginning, failing to connect. Much
> > searching w/ Google turns up no answers. Nor does a tech support
> > consultation with the hosting service. The failure is NOT due to wrong
> > username or password as I can establish ssh connections from the CLI.
>
> It's worrying when this happens, but hosting services are notorious for
> changing things which don't affect Mac or Windows users, but which may
> affect Linux users.
>
> From what you quote below it looks like it's having trouble identifying
> which key exchange (kex) algorithm to use: the server wants you to use
> diffie-hellman-group-exchange-sha256 but Konqueror can only use one of
> curve25519-sha256 at libssh.org
> ecdh-sha2-nistp256
> diffie-hellman-group14-sha1
> diffie-hellman-group1-sha1
> This post https://ubuntuforums.org/showthread.php?t=2297006 (different
> circumstances and different software) explains how to find out what
> algorithms are supported, but it's a couple of years old.
>
> At a wild random guess the hosting company has changed things so that
> they only support diffie-hellman-group-exchange-sha256, so you'll need
> an sftp client that supports that method of key exchange. Obviously
> FileZilla doesn't.
>
> Can you try again and note the EXACT date and time, then call tech
> support and ask them to check the access logs (eg /var/log/secure) to
> find out if they can see a request coming in from your IP address, and
> being rejected.
>
> If you search Mr Google for
>    filezilla diffie-hellman-group-exchange-sha256
> you will gets lots of pages about this problem, so it seems to be well
> known. Several posts make the suggestion along the lines of:
>
> > FileZilla's SFTP support is based on PuTTY's psftp. If you change the
> > default key exchange cipher priorities in PuTTY, it should also
> > affect FileZilla.
>
> but this may only apply to Windows clients. I'm afraid I don't have a
> solution (and I just hope my own hosting provider doesn't make the same
> move, although I only use FZ very rarely, as sftp from the command line
> is fine for my own use).
>
> ///Peter
>
>
> > Konqueror also fails to connect and gives the following, more detailed
> > error:
> >
> >     The requested operation could not be completed
> >
> >     Details of the Request:
> >     URL: sftp:// [redacted]
> >     Protocol: sftp
> >     Date and Time: Thursday, June 01, 2017 04:18 PM
> >     Additional Information: kex error : no match for method kex algos:
> >     server [diffie-hellman-group-exchange-sha256], client
> >     [curve25519-sha256 at libssh.org,ecdh-sha2-nistp256,diffie-
> hellman-group14-sha1,diffie-hellman-group1-sha1]
> >     Description:
> >     kex error : no match for method kex algos: server
> >     [diffie-hellman-group-exchange-sha256], client
> >     [curve25519-sha256 at libssh.org,ecdh-sha2-nistp256,diffie-
> hellman-group14-sha1,diffie-hellman-group1-sha1]
> >
> > I note that I've gone so far as deleting all Filezilla-related files and
> > re-installing it as well as deleting my known hosts file, to no avail.
> > So I turn to this list in desperation. I would really like to continue
> > to use Filezilla because it's fast and easy.
> >
> > --
> > Roger
> > linux.rog at gmail.com
> >
> >
> >
>
> --
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