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Please see EDIT #2 for latest findings

I've looked at other similar questions but, unfortunately, none of them seemed to help. This one is the closest and my symptoms are similar.

Here's the issue:

  1. I am trying to setup the equivalent of ProxyJump via PuTTY, from Windows workstation A to Linux box (MFA protected, password first) B to Linux target C
  2. My proxy command is plink.exe -agent -l <user> %proxyhost -nc %host:%port\n
  3. Upon initiating a connection to C, I just see a window that says

Starting local proxy command: plink.exe -agent -l B -nc C:22

and simply hangs there.

In PuTTY log I see

Using keyboard-interactive authentication .Password:

but that password prompt never shows up on screen and the open window won't take any input.

Any suggestions on what I might have missed?

Thanks in advance for all help.

Cheers!

EDIT #1: Upon further experimentation, it turns out this issue has to do with any keyboard-interactive second factor. Even I changed from Azure MFA to Duo, I still see the same behavior.

The output from the remote server is never tied back to the PuTTY terminal - I wonder if plink has anything to do with this, since it's intended behavior is similar to ProxyCommand otherwise. Perhaps something to do with how pipes to and from remote sessions are handled?

EDIT #2: This is almost certainly now an issue with plink and keyboard-interactive authentication. I tried PubKeyAuthentication only as well as GSSAPIAuthentication only and both of them work fine. I then tried PasswordAuthentication only and it failed.

I've updated the post title accordingly.

PerennialN00b
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  • Do you have putty agent running with a valid key loaded? – Zoredache Dec 01 '18 at 01:08
  • The first factor is a password, not key, so I don't have any keys loaded – PerennialN00b Dec 01 '18 at 15:11
  • Oh, I didn't notice the multi-factor part of the question. That might be pretty tricky to handle on Windows. Is using the [Microsoft openssh port](https://github.com/PowerShell/openssh-portable) an option, or running WSL and using SSH in WSL an option? Both those should basically offer identical functionality to the linux systems. – Zoredache Dec 01 '18 at 21:05

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