Add Support SHA256 fingerprints for host key validation

[MVKozlov]

I think we need it because it's default for original ssh

sshnet/SSH.NET#1098

[darkoperator]

Makes sense

[MVKozlov]

I plan to do this in the near future, I think it’s worth making it by default, leaving the old format only for compatibility

[MVKozlov]

Is it necessary to force the host to be updated to the new format in hosts.json ?

[MVKozlov]

@darkoperator, What do you think about whether it is necessary to update the keys to the new format?
I prepared commits for PR

[darkoperator]

You mean the current key fingerprints that are stored ? If it is those it would simplify the code by removing the backward complexity, but adds the risk of a bug causing issues. I think it would be a risk we can mitigate by testing before pushing and it should not be a problem.

[MVKozlov]

yes, at the moment I’m just testing first for a match with sha256, then md5. and then the result can be saved (now commented out).

For new hosts, a new format sha256 is always written.

It seems to me that this could be done after upgrade the version to 4.0 (you also have serious changes there with authorization)