WinSCP 5.5.6 error - Server refused our key (Connecting through a proxy server)

We are using c# winscp.net assembly.

We have set up the task scheduler job which runs every 10 minutes.

The task failed occassionally. The task failed because of this error

"Failed to login (1 time) <WinSCP.SessionRemoteException: Connection has been unexpectedly closed. Server sent command exit status 0. ---> WinSCP.SessionRemoteException: Authentication log (see session log for details): Using username "BTMUDEV". Server refused our key. Authentication failed. --- End of inner exception stack trace --- at WinSCP.SessionLogReader.Read(LogReadFlags flags) at WinSCP.ElementLogReader.Read(LogReadFlags flags) at WinSCP.CustomLogReader.TryWaitForNonEmptyElement(String localName, LogReadFlags flags) at WinSCP.CustomLogReader.WaitForNonEmptyElement(String localName, LogReadFlags flags) at WinSCP.Session.Open(SessionOptions sessionOptions) "

We are using the 5.5.6 version and this problem occurs in this version.

Any quick help will be highly appreciated.

Thank You,

viral.shah wrote:

Server refused our key

You have configured the key authentication incorrectly on the server.

Thank You for the response.

The task runs every 10 minutes, 24 hrs a day for a month now. But we got this error on just one particular day within 2 hours of interval. I belive, If the key was incorrectly configured, It would not have worked at all. Isn't it?

Could there be any other reasons that We can get this error?

Thank You,
Viral

Then it can be some variation of a padding bug, known in some servers.
See for example https://winscp.net/tracker/1091

Try to enable Requires padding on SSH-2 RSA signatures:
https://winscp.net/eng/docs/ui_login_bugs#sshbug_rsapad2

Thanks for the reply again.

The error which we got is not "Server refused public-key signature despite accepting key". For this error, we already put the workaround and it fixed the problem.

This error is "Server refused our key (Connecting through a proxy server)". This error also occurred occassionally.

Any quick help will be highly appricieted.

Thank You,
Viral

What is your server?

Server - Axway (Secure Transport Server 4.8.1).

Did you consider upgrading your server? Your version seems pretty old.