sftp key issue in 3.55 but not in 3.54

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mbover
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sftp key issue in 3.55 but not in 3.54

#1 Post by mbover » 2021-07-30 09:21

Hi all,
very odd bug.
if a user is on the checkpoint vpn in to the office and try to connect to our sftp (internally) they get this error.
Trace: Remote side sent disconnect message type 9 (host key not verifiable): "Could not use server's key. Please contact server administrator to generate new key."

if you connect externally without vpn it works
or if you remove filezilla and install 3.54 it works fine.

Any ideas or is this a known bug in filezilla 3.55
ta

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botg
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Re: sftp key issue in 3.55 but not in 3.54

#2 Post by botg » 2021-07-30 09:52

What operating system are you using?

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Re: sftp key issue in 3.55 but not in 3.54

#3 Post by mbover » 2021-08-05 08:54

windows 10 pro 1909 on the client

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Re: sftp key issue in 3.55 but not in 3.54

#4 Post by mbover » 2021-10-04 10:34

this is still and issue.
any one know if this is a know bug?

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Re: sftp key issue in 3.55 but not in 3.54

#5 Post by botg » 2021-10-04 10:36

Please post a complete log with debug log level set to 3.

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Re: sftp key issue in 3.55 but not in 3.54

#6 Post by mbover » 2021-10-05 10:59

Trace: CControlSocket::SendNextCommand()
Trace: CSftpConnectOpData::Send() in state 0
Status: Connecting to sftp.inchcape.com...
Trace: Going to execute C:\Program Files\FileZilla FTP Client\fzsftp.exe
Response: fzSftp started, protocol_version=11
Trace: CSftpConnectOpData::ParseResponse() in state 0
Trace: CControlSocket::SendNextCommand()
Trace: CSftpConnectOpData::Send() in state 3
Command: open "G------@sftp.inchcape.com" 22
Trace: Looking up host "sftp.inchcape.com" for SSH connection
Trace: Connecting to 10.83.59.43 port 22
Trace: We claim version: SSH-2.0-FileZilla_3.55.1
Trace: Connected to 10.83.59.43
Trace: Remote version: SSH-2.0-CoreFTP-0.3.3
Trace: Using SSH protocol version 2
Trace: Doing Diffie-Hellman group exchange
Trace: Doing Diffie-Hellman key exchange using 4096-bit modulus and hash SHA-256 (unaccelerated) with a server-supplied group
Trace: Remote side sent disconnect message type 9 (host key not verifiable): "Could not use server's key. Please contact server administrator to generate new key."
Trace: CSftpControlSocket::OnTerminate without error
Trace: CControlSocket::ResetOperation(66)
Trace: CSftpConnectOpData::Reset(66) in state 3
Error: Could not connect to server
Status: Waiting to retry...

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Re: sftp key issue in 3.55 but not in 3.54 (issue in 3.56.2 as well)

#7 Post by mbover » 2021-11-01 12:09

Still have the same issues on 3.56.2

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Re: sftp key issue in 3.55 but not in 3.54

#8 Post by botg » 2021-11-02 08:42

Trace: Remote side sent disconnect message type 9 (host key not verifiable): "Could not use server's key. Please contact server administrator to generate new key."
Something is wrong with the server. You should do as the error message sent by the server says.

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Re: sftp key issue in 3.55 but not in 3.54

#9 Post by mbover » 2021-11-03 11:34

Sorry but why does this as this system works using an older filezilla version, if there is an issue on the server

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Re: sftp key issue in 3.55 but not in 3.54

#10 Post by botg » 2021-11-03 15:31

Could be any number of reasons. Different software behaves differently. Even a tiny change can expose a fault elsewhere. In this case the server itself tells you clearly that it's a server-side issue.

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Re: sftp key issue in 3.55 but not in 3.54

#11 Post by graham-inchcape » 2021-12-22 17:46

Hi both.

Graham here from the same company as Mat who raised the issue. I'm a software developer and very long-term user of FileZilla and love what you're doing with this product.

In this case, I suspect an incompatibility between client and server. That said, I note that FileZilla 3.54 worked fine and that WinSCP works fine against this server.
The difference between 3.54 and 3.57 is in the Diffie-Hellman exchange. The 3.57 client sends a different "Diffie-Hellman Group Exchange Init" to 3.54, which the server rejects.

16 3.370823 172.29.140.210 10.83.59.43 SSHv2 582 Client: Diffie-Hellman Group Exchange Init
17 3.442017 10.83.59.43 172.29.140.210 TCP 54 22 → 60701 [ACK] Seq=952 Ack=1923 Win=131584 Len=0
18 3.482528 10.83.59.43 172.29.140.210 SSHv2 166 Server: Disconnect

What changed in 3.55 in this area?

Graham

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Re: sftp key issue in 3.55 but not in 3.54

#12 Post by botg » 2021-12-23 08:52

Why does the server reject it?

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