2017v14, Couldn't agree a key exchange algorithm (available: curve25519-sha)

[cdmoore1972]

Hello,

My client has 2017v14 licensed through a third party. They're upgrading to a new RedHat 9.x server.

The WindX PxPlus 2017 client works with the (much) older RedHat server, but is getting the following error on the new server just after entering the username into the terminal login prompt:

Couldn't agree a key exchange algorithm (available: curve25519-sha)

I'm assuming that the new server did not enable the KEx or SSH ciphers that come with 2017. Is there a list of those somewhere? I didn't see them in the support docs.

Or if it's something else and you know the fix, I'll take that, instead.

Thanks,

Chris
 

[Devon Austen]

WindX SSH is handled via a included version of plink (putty command line).

It looks like putty got support for that cipher if the AI summary is to be believed in version 0.76. This is newer then your version of PxPlus so it explains the issue.

If you upgrade to the latest version of PxPlus it include plink 0.83 which would support the cipher.

TO find out what ciphers it does support you will have to look up putty documentation for the version of plink in your PxPlus install. It may or may not be possible to enable them on the server.

[cdmoore1972]

The software vendor has a license for the WindX 2017 client. I don't know that they have or are willing to license the newer client, which I'm sure will work.

I'm stuck with dumbing down the cryptography settings on the server until it will work with 2017.