Re: custom banner

[Jakub Jelen <jjelen@xxxxxxxxxx>]

On 2/17/21 5:13 PM, tangying212 wrote:
> Hello Andreas,
> Uhm,
>    Can you please share the solution/guide/instructions/setup to customize the banner before using the ssh_connect() function.I found the custombanner in the struct ssh_session->opt, but I don't know how to use it.please help me,thanks.

Hi,
it looks like libssh does not allow changing this in the client 
applications through API. That part of string is usually used by 
applications which can use it to detect various bugs or specification 
deviations (at least in case of OpenSSH, there is whole bunch of compat 
code). So unless you have really good reason to change it, I would try 
to avoid it.

The custombanner is used only in the server side of libssh and requires 
using private header file session.h to access the internal session 
variable session->opts.custombanner.

If there is a good reason to use different banner, I would suggest to 
update the function ssh_send_banner() in client.c to use the 
custombanner and update options.c to allow setting this through 
ssh_options_set(session, SSH_OPTIONS_CUSTOM_BANNER, "the banner").

Best regards,
--
Jakub Jelen
Senior Software Engineer
Crypto Team, Security Engineering
Red Hat, Inc.