How to change SSH banner? [SOLVED…the ugly way]

alphazo

Hello,

Moved from M0n0 to pfSense after 3 years.

How can I permanently change the SSH banner from "SSH-2.0-OpenSSH_4.5p1 FreeBSD-20061110" to "Welcome Home"

I added a ssh-banner file and added```
Banner /etc/ssh/sshd-banner


Can someone give me a hint ?

Thanks
Dany

jamesdean

The file that rewrites the /etc/ssh/sshd_config is located at /etc/sshd.

Backup /etc/sshd before starting
Edit /etc/sshd

Find the folowing lines, should be line 86
/* Include default configuration for pfSense */
$sshconf = "# This file is automatically generated at startup\n";

Then add your extra options just below the said lines.
$sshconf .= "Banner /etc/ssh/banner\n";
$sshconf .= "VersionAddendum this is a private network\n";

Banner is the message during login

VersionAddendum is the sshd helo reponse when connected. Ussally sshd says version of the OS as a helo.
I don't like that so I always change it.

alphazo

Thanks a lot. I'm actually traveling so I'll have to test it when I return home.

Dany

alphazo

Hi Jamesdean,

It worked as advertised.

Now that "FreeBSD…" has been replaced by custom text, is there any way to get rid of the leading "SSH-2.0-OpenSSH_4.5p1" when you do a telnet to the box?

Thanks again
Dany

alphazo

Ok I did it…. the (very) ugly way ! :-[

I opened my favorite Hex editor and patched the pfsense img file to replace all references to "OpenSSH_4.5p1" by "KEEP OUT ". String lengths were not modified. Now when I telnet to the box I get "SSH-2.0-KEEP OUT".

I feel bad about this...I just wanted to see if this would work. Anyway if someone knows a more elegant way to get the above result I'll be glad to forget about this episode.

Cheers
Dany

jamesdean

Danny

You should never remove the SSH-2.0-OpenSSH_4.5p1. Some SSH clients use this to figure out what options your SSHD server supports. In the past I have changed SSH-2.0-OpenSSH_4.5p1 too SSH-2.0 and never encountered a SSH client that brakes because of that change, but you never know. The clean way to change the SSH-2.0-OpenSSH_4.5p1 is to edit the SHHD source code.

laterz
JamesDean