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SFTP, Remote side unexpectedly closed network connection

JohnWis Guest

SFTP, Remote side unexpectedly closed network connection

2020-09-07 12:44

WinSCP version 5.17.6
Worked with version 5.9.3
Windows server 2016 (in Citrix)
SFTP
Using the GUI
Error:

Remote side unexpectedly closed network connection

or:

Network error: Software caused connection abort

When setting up a connection to a Linux server, an error occur, connection can't be establised.
With the old version of WinSCP there is no issue to connect to these Linux servers, It is not 1 server but a pool of servers not working.
The WinSCP client (old en new) are running on a XenApp environment.

winscp.log (14.45 KB)

Description: 3 sessions, all failed but with 2 different messages

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martin◆ Site Admin
Joined:: 2002-12-10
Posts:: 40,567
Location:: Prague, Czechia

Re: SFTP, Remote side unexpectedly closed network connection

2020-09-08

Can you post a log file of a successful session from the old version of WinSCP?

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JohnWis Guest

SFTP, Remote side unexpectedly closed network connection

2020-09-09 18:48

Old log file added

winscp.log_old.txt (7.78 KB)

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2020-09-11

Thanks for the log. It didn't reveal anything useful though. Did you have an access to server-side logs? Don't you need to whitelist the new version somehow in your "XenApp environment"?

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JohnWis Guest

SFTP, Remote side unexpectedly closed network connection

2020-09-23 10:09

The log file from the linux server gives this message:

2020-09-23T10:47:35.129652+02:00 TController-Databus01-P-ACC sshd[348917]: fatal: No supported key exchange algorithms found [preauth]

Sshd_config server

Ciphers aes128-ctr,aes192-ctr,aes256-ctr
KexAlgorithms diffie-hellman-group-exchange-sha256
MACs hmac-sha2-256,hmac-sha2-512

And WinSCP should support this, but is this still in the current release
https://winscp.net/eng/docs/tls_ciphersuites

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2020-09-25

Can you try to find out, what version did introduce the problem?
https://sourceforge.net/projects/winscp/files/WinSCP/

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JohnWis Guest

SFTP, Remote side unexpectedly closed network connection

2020-09-25 16:53

We already did

Version 5.9.3 ok
Version 5.10 Nok
Version 5.17.6 Nok

Do you want us to try the versions between 5.9.3 and 5.10?

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2020-09-29

JohnWis wrote:

Do you want us to try the versions between 5.9.3 and 5.10?

Yes please.

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JohnWis Guest

SFTP, Remote side unexpectedly closed network connection

2020-09-30 14:40

Tested again
Version 5.9.6 is OK
Version 5.10.4.RC NOK
Version 5.11 is NOK

So there is a difference after version 5.9.6

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martin◆ Site Admin
Joined:: 2002-12-10
Posts:: 40,567
Location:: Prague, Czechia

Re: SFTP, Remote side unexpectedly closed network connection

2020-10-02

I believe there was no change in those versions that might have caused this.
But you might be suffering from this glitch in OpenSSH:
https://bugzilla.mindrot.org/show_bug.cgi?id=2748
I have added this issue to the documentation:
https://winscp.net/eng/docs/incompatible_changes#older_general

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JohnWis Guest

Re: SFTP, Remote side unexpectedly closed network connection

2020-10-02 10:08

What should we do to analyse or solve if this is the problem we have.

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2020-10-02

Upgrade your OpenSSH installation.
Or, if you register, I can send you a copy of WinSCP that does not trigger the wrong rule.

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JohnWis
Joined:: 2020-10-05
Posts:: 2

Re: SFTP, Remote side unexpectedly closed network connection

2020-10-05 10:57

I just registered, can you send me a copy of WinSCP that does not trigger the wrong rule.

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2020-10-06

Sent.

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JohnWis

Re: SFTP, Remote side unexpectedly closed network connection

2021-09-03 13:54

Hello, in the past I get from you a changed version of WinSCP without the issue, can you give us a new updated mobile version without the issue?

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martin◆ Site Admin

Re: SFTP, Remote side unexpectedly closed network connection

2021-09-07

I have sent you the modified version only for your "analysis", if you indeed suffer from the referenced problem. It was not meant to be a solution. The solution is to upgrade your OpenSSH installation.

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Emma 1989 Guest

Re: SFTP, Remote side unexpectedly closed network connection

2021-09-10 20:56

martin wrote:

Upgrade your OpenSSH installation.
Or, if you register, I can send you a copy of WinSCP that does not trigger the wrong rule.

Can you please send this to me also I cannot get it to work for me at all- emma181111@hotmail.com

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martin◆ Site Admin
Joined:: 2002-12-10
Posts:: 40,567
Location:: Prague, Czechia

Re: SFTP, Remote side unexpectedly closed network connection

2021-09-13

@Emma1989: See my answer to @JohnWis above:

I have sent you the modified version only for your "analysis", if you indeed suffer from the referenced problem. It was not meant to be a solution. The solution is to upgrade your OpenSSH installation.

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