tightening sshd, removing server identification banner

[Christian Weisgerber]

On 2020-02-17, David Mehler <dave.mehler at gmail.com> wrote:

> I'm running FreeBSD 12.0. I'm atempting to tighten up my sshd
> configuration. I've got things where I want them, except for the
> connecting banner. I'm using sshaudit.com to test things and this is
> what it's saying for the banner setting:
>
> Banner:SSH-2.0-OpenSSH_7.8 FreeBSD-20180909
> 
> I would rather this be set to nothing or at most very minimal.

RFC4253 says the identification string MUST be

  SSH-protoversion-softwareversion SP comments CR LF

where only "comments" is optional.

I also recommend a look at src/crypto/openssh/compat.c to gain some
appreciation that "softwareversion" is important.

-- 
Christian "naddy" Weisgerber                          naddy at mips.inka.de