Is it possible to modify the string that the OpenSSH server displays when a raw connection is established?
It is not about the text banner displayed after the connection is established and which can be configured by the
Banner parameter in
sshd_config, but about the raw output the SSH server sends on a connection attempt before the handshake.
For example, given a raw telnet connection
$ telnet localhost 22 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. SSH-2.0-OpenSSH_7.2p2
is there a way to reduce identifying information to the bare minimum?
My understanding is that
SSH-2.0- must be present because it is required by the SSH protocol, but the string that follows -
OpenSSH_7.2p2 - is probably not required by the protocol but I can't see a way to change or remove it without recompiling.
The intent is to avoid providing more info than strictly necessary for the protocol to work.