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SFTP protocol violation: Invalid message number

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bkskidmore@chattanooga.gov
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SFTP protocol violation: Invalid message number

I just upgraded to WinSCP 6.1 and now I'm getting the following error for a couple of my SFTP sites.
SFTP protocol violation: Invalid message number
Is there something I can do to fix this problem. As information, I've connected to the problematic sites with another program successfully.

Thank you

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ssstevens@aurorak12.org
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Also getting 'SFTP protocol violation: Invalid message number' error after upgrading to 6.1

I am also getting the same error message when connecting to one server. This started right after upgrading to 6.1
I tried changing the Preferred SFTP protocol version to 5, as suggested, but still got the error.
Log file is attached.

If I use FileZilla, I am able to connect successfully – but I would rather use WinSCP.
Are there other workarounds available?
Thanks
  • OIC-SFTP-Server.log (20.18 KB, Private file)

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martin◆
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Re: Also getting 'SFTP protocol violation: Invalid message number' error after upgrading to 6.1

Thanks both. Can you please post session log file on Debug 2 level? A log file from a working session from an older version of WinSCP might be useful too.

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martin◆
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Re: Also getting 'SFTP protocol violation: Invalid message number' error after upgrading to 6.1

Thanks. Imo, it's clearly a bug on the server side. The server "supports" vendor-id SFTP extension. It first sends its own nonsense vendor information:
. Server software: ${pom.artifactId} ${pom.version} (0) by ${pom.groupId}
And when WinSCP sends its own vendor information (that's new in WinSCP 6.1), the server just fails totally.

For a start, can you try decreasing SFTP version to 3 (or even lower)? It might prevent the server from sending its vendor information, what would in turn prevent WinSCP from sending its.
https://winscp.net/eng/docs/ui_login_sftp

If you have means for contacting the server vendor, please report the problem to them.

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martin◆
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Re: Also getting 'SFTP protocol violation: Invalid message number' error after upgrading to 6.1

Let us know what their response was.

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EDISean
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I have the same issue, but your solutions didn't work :-(

Hi,

I also get the message:
SFTP protocol violation: Invalid message number 8 (expected 200).
The numbers change, but the message stays the same.
I can't change anything on the server side because "Everything is fine with our server. It must be a problem with your client"...
FileZilla works fine, but we need a way to have the transfer scripted because of reasons ;-)

I've attached the log of a failed attempt.
Maybe someone can see what the issue is?
I've tried reducing the SFTP-version but the error stays the same (if I go down to 2, I get the messsage that I should use 3,4,5 or 6).
  • Unified-Post-Prod.log (19.87 KB, Private file)

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martin◆
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Re: I have the same issue, but your solutions didn't work :-(

Thanks for the log.
The server supports vendor-id SFTP extension. So WinSCP uses the extension to provide the server with its information using SSH_FXP_EXTENDED request (with "sequence number" 200). To this, the server should respond with SSH_FXP_EXTENDED_REPLY response with the same sequence number. (Or with an error using SSH_FXP_STATUS response, though that is not expected in this case). Instead, the server "responds" with SSH_FXP_EXTENDED message with sequence number 8. This is totally wrong:
  • SSH_FXP_EXTENDED is not a valid response to SSH_FXP_EXTENDED request.
  • SSH_FXP_EXTENDED is a request message. It can only ever be sent by the client, never by the server.
  • The "response" uses wrong sequence number. In that session, WinSCP didn't sent any request with sequence number 8.
It's irrelevant that FileZilla "works", as FileZilla does not support the vendor-id extension. So it does not trigger the bug in the server.

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EDISean
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Erm...

Hi, thanks for the quick analysis.

Is there anything I can do on my side to get it to work?
Or does the Server-side need to change something?

Thanks again for the quick reply.

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EDISean
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It worked

Hi,

I've already answered via email, but just to let every other person with the same problem know: IT WORKED!!!

Is there a timeline when (or if) it will be implemented in the release-version of WinSCP?

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JSzabo@...
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Hello Martin,

We are also experiencing this exact same issue with WinSCP 6.1 and the Oracle OIC SFTP server. Do you have a release date for the fix included with 6.2? In the meantime, would it be possible to get the prerelease version (beta) as well?

Thank you in advance,
Julie

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EDISean
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6.2 Beta

Ahh, ok.

Then I read the last post regarding a release wrong.
To me it sounded like 6.2 (non-beta) release was just around the corner.

Thanks for the info

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rookie1977
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Re: It worked

Thanks Martin, that worked for me as well in the GUI. How do I have to implement this in a WinSCP-script under the new version 6.3?

At the moment I am getting the following error in the log: 
. 2024-02-23 16:17:53.050 We will use UTF-8 strings as it is mandatory with SFTP version 4 and newer
> 2024-02-23 16:17:53.050 Type: SSH_FXP_EXTENDED, Size: 61, Number: 200
. 2024-02-23 16:17:53.050 Getting current directory name.
. 2024-02-23 16:17:53.050 Getting real path for '.'
> 2024-02-23 16:17:53.050 Type: SSH_FXP_REALPATH, Size: 11, Number: 272
< 2024-02-23 16:17:53.081 Type: Unknown message (77), Size: 14, Number: 1634890857
. 2024-02-23 16:17:53.081 Attempt to close connection due to fatal exception:
* 2024-02-23 16:17:53.081 SFTP-Protokollverletzung: Ungültiger Type der Antwortnachricht (77).
. 2024-02-23 16:17:53.081 Closing connection.
. 2024-02-23 16:17:53.081 Sending special code: 1
. 2024-02-23 16:17:53.113 Session sent command exit status 0
. 2024-02-23 16:17:53.113 Main session channel closed
. 2024-02-23 16:17:53.113 All channels closed
< 2024-02-23 16:17:53.113 Script: SFTP-Protokollverletzung: Ungültiger Type der Antwortnachricht (77).
< 2024-02-23 16:17:53.113 Fehler beim Empfang des Verzeichnisnamens von der Gegenstelle.
Thanks for your help.
Yves

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rookie1977
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Hi Martin

Just found the solution for my problem and would like to share it here. I just used the following switch in the WinSCP-script: 
-rawsettings ProtocolFeatures=-vendor-id
Thanks!
Yves

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