SHA2 server SFTP fingerprints using Renci.SshNet

Question

I'm using Renci.SSHNet to establish a connection to SFTP servers. I've done so without any problems but I've recently ran into a server to which I can´t establish a connection through my code.
I keep getting the following error:

No suitable authentication method found to complete authentication (publickey,keyboard-interactive).

The thing is, I know the host, user and password are correct as I can establish a connection using FileZilla. I've noticed while connecting to other servers using FileZilla that the fingerprints for the ones I can also connect to with my code are generated through RSA as opposed to the one that is giving me trouble, which is SHA2.

TL/DR: What I'm wondering is: is the Renci.SshNet.SFTP library compatible with sha-2 generated fingerprints or will I have to use another library for this?

Answer 1

The SSH.NET library does not support ECDSA key exchange algorithms (ecdh-sha2-*) yet (as of 2014.4.6-beta2 release).

It supports these:

• diffie-hellman-group-exchange-sha256
• diffie-hellman-group-exchange-sha1
• diffie-hellman-group14-sha1
• diffie-hellman-group1-sha1

The ecdh-sha2-*'s are commented-out, probably because the implementation is not complete/tested.

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Though note that the server can support multiple algorithms and can agree on a different algorithm with different clients.

So the fact that you see an unsupported key type in the FileZilla, does not mean that the server necessarily insists on this key type.

It is clear that the server does not require ECDSA key exchange from the fact that the connection fail in the authentication phase. The authentication happens only after a successful key exchange. So your root problem is not the key exchange, but authentication.

If you need a help resolving your authentication problem, start a new question , include relevant source code, FileZilla log file and explain us what you did to setup the authentication on the server-side. A server-side log file might be helpful too.