WinSCP re-authenticates on file save with OTP, but works correctly via SSH port forwarding

Hi,

I am experiencing an issue when using WinSCP with a server that requires a password and a verification code for authentication.

Steps to reproduce:

• Connect to the server using WinSCP.
  
• Enter the password and verification code.
  
• Login succeeds.
  
• Open a remote file and edit it (tested with both the internal editor and an external editor).
  
• Save the file.
  

At this point, WinSCP prompts for the verification code again. If I continue editing and saving files within a short period of time, eventually the connection fails with:

No supported authentication methods available

Thanks you get an OTP prompt for the first save is expected, as edited files are uploaded using a separate connection. For the "No supported authentication methods available" problem, please post session log file.

Sorry for the late reply. Here is the log file.

You wrote that saving works for some time. But I do not see that in the log. It is failing from the very first save. So how is it? It looks like you are actually not able to use your one-time-password second time for the background session.

Maybe you can take a look at this attachment.

The screencast confirms that, doesn't it? The one-time password seems to really work just one time. What if you use new one-time password for the second prompt?

Yup. For the second prompt, I copied the new verification code again.

I'm not sure if the validity period is too short, so the verification code happened to remain the same. However, would that still be an issue?

I do not know, it's the server that validates the code. So did you try waiting for a new code? Does it change anything?

martin wrote:

I do not know, it's the server that validates the code. So did you try waiting for a new code? Does it change anything?

In theory, as long as the verification code is still valid, the server should allow a new connection even if the same code is used within its validity period.

For example, I can open multiple PuTTY connections within a very short period using the same verification code without any issues.

Yes, I did try waiting for a new verification code. In that case, it usually works. However, it feels like an unnecessary workaround since the original code is still valid.