Re: An additional-auth mechanism for SSH to protect against scanning/probing attacks

Peter Gutmann <[email protected]> Thu, 1 Dec 2022 13:38:05 +0000
Newsgroups gmane.ietf.secsh
Message-ID <SY4PR01MB625156A06FFB2C8017BB3206EE149@SY4PR01MB6251.ausprd01.prod.outlook.com>
Mouse <[email protected]> writes:

>> [...] now I'm tempted to see what happens if I respond to connect
>> attempts on port 22 with:
>
>> 220 $servername ESMTP Chuckmail bent over and ready
>> +OK POP3 server ready <abcd@$servername>
>> OK IMAP/POP3 ready $servername
>> 220 FTP Server $servername ready
>> SSH-2.0-$server-$version
>
>Should be amusing, if nothing else!

So PuTTY handles it just fine while MobaXterm reports a decryption error,
probably because it's hashing the entire mess of initial text rather than just
the last line with the SSH ID and getting incorrect encryption keys.

Having said that, I don't think anything should be accepting that abomination
as an SSH ID even if the spec says they should, it's an abuse of a weird
corner case in the spec to send that and expect it to work.

Peter.