SSH Hostkey Usage – Linux Server with Plink.exe on Windows Host

plinkputtyssh

I have Linux server running sshd.

How to provide hostkey from the Linux server to plink.exe on Windows?

e.g.: for running plink.exe -ssh -batch -m plink.tmp -hostkey ...

Best Answer

You can use plink itself to get the host key:

c:\> plink -v -batch host
Connecting to 1.2.3.4 port 22
We claim version: SSH-2.0-PuTTY_Release_0.68
Server version: SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.1
Using SSH protocol version 2
Doing ECDH key exchange with curve Curve25519 and hash SHA-256
Server also has ssh-ed25519/ecdsa-sha2-nistp256 host keys, but we don't know any of them
Host key fingerprint is:
ssh-rsa 2048 c6:e7:49:ec:07:5b:30:02:d9:57:dd:7f:39:e3:f3:35
Initialised AES-256 SDCTR client->server encryption
Initialised HMAC-SHA-256 client->server MAC algorithm
Initialised AES-256 SDCTR server->client encryption
Initialised HMAC-SHA-256 server->client MAC algorithm
Disconnected: Unable to authenticate

The parameter -v (verbose) is needed for the additional information, -batch makes sure plink exits directly without a login (as long as username and password are not provided as well).

In the output you find Host key fingerprint is:, followed by the fingerprint in a hexadecimal format, in this case:

c6:e7:49:ec:07:5b:30:02:d9:57:dd:7f:39:e3:f3:35

This is the string you have to provide to plink -hostkey to confirm that the target host is actually the host it claims to be.

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