Question about host key algorithms

Christian Hesse
2020-03-02T21:24:47Z

Luveh Keraph <1.41421 at gmail.com> on Mon, 2020/03/02
14:07:
> When I do ssh -Q key, where ssh is the OpenSSH 7.4p1 client, I get the
> following output:
>
> ssh-ed25519
> ssh-ed25519-cert-v01 at openssh.com
> ssh-rsa
> ssh-dss
> ecdsa-sha2-nistp256
> ecdsa-sha2-nistp384
> ecdsa-sha2-nistp521
> ssh-rsa-cert-v01 at openssh.com
> ssh-dss-cert-v01 at openssh.com
> ecdsa-sha2-nistp256-cert-v01 at openssh.com
> ecdsa-sha2-nistp384-cert-v01 at openssh.com
> ecdsa-sha2-nistp521-cert-v01 at openssh.com
>
> The thing is,  one can invoke both client and server with -o
> HostKeyAlgorithms=rsa-sha2-256, or -o HostKeyAlgorithms=rsa-sha2-512, and
> everything's OK.
>
> Why is it that rsa-sha2-* are not displayed in the output above? In fact,
> no option to -Q elicits them, and they are not mentioned in the OpenSSH
> client and server man pages.
>
> Is this intentional?

You should query for HostKeyAlgorithms

ssh -Q HostKeyAlgorithms

That list should contain rsa-sha2-256 and rsa-sha2-512.
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