Re: Key exchange fail

[Yusuf Saka <yusufsaka5481@xxxxxxxxx>]

Hey,
Thank you for replying back so soon
I believe key exchange fail is somehow related to race conditions in my
class which which can be solved but I am unable to figure out the other
problem and why it persists

I get the following output after key exchange which indicates that client
requested authentication. I already set the appropriate callback functions
to handle these requests. I also checked in my debugger that session is
indeed connected, session is not NULL event is not NULL and
ssh_event_add_session is also succesful.

[2025/03/28 09:50:02.784775, 4] ssh_socket_pollcallback:  Poll callback on
socket 4 (POLLIN POLLOUT ), out buffer 0
[2025/03/28 09:50:02.784863, 4] ssh_socket_unbuffered_read:  read 44
[2025/03/28 09:50:02.784899, 3] ssh_packet_socket_callback:  packet: read
type 5 [len=24,padding=6,comp=17,payload=17]
[2025/03/28 09:50:02.784905, 3] ssh_packet_process:  Dispatching handler
for packet type 5
[2025/03/28 09:50:02.784911, 3] ssh_packet_service_request:  Received a
SERVICE_REQUEST for service ssh-userauth

But ssh_event_dopoll causes segmentation fault. What would be the following
debugging processes

```
// Authenticate and open a channel
while (sdata.authenticated == 0 || sdata.channel == NULL) {
/* To Do! Simulate a successful brute force attempt at random X attempts to
make the attacker get inside*/
if (sdata.auth_attempts >= 3) {
std::cout << YELLOW << "[SSHServer::handle_session]: Auth attempts exceeded"
<< RESET << std::endl;
goto cleanup;
}
if (ssh_event_dopoll(event, 100) == SSH_ERROR) {
std::cerr << RED << "[SSHServer::handle_session]: " << ssh_get_error(session)
<< RESET << std::endl;
goto cleanup;
}
}
std::cout << GREEN << "[SSHServer::handle_session]: Authenticated user" <<
RESET << std::endl;




On Fri, Mar 28, 2025 at 7:54 AM Jakub Jelen <jjelen@xxxxxxxxxx> wrote:

> Hi,
> do you have some error?
>
> Please, try to set the libssh log level to SSH_LOG_TRACE. It will then
> print more information about what is going on under the hood and might
> show up some path to the failure.
>
> Jakub
>
> On Fri, Mar 28, 2025 at 12:20 PM Yusuf Saka <yusufsaka5481@xxxxxxxxx>
> wrote:
> >
> > Hey there,
> >
> > I recently read your docs on implementing a ssh connection and read one
> of your example codes called ssh_server.c which works quite fine in my own
> device. I've been trying to implement the C++ version of this code with
> classes in play for days but the code just won't work. I am trying to
> create a ssh server with threads (pthread) mainly and it fails in
> > ssh_server.cpp
> > in handle_session function at line 187.
> > KEY_FILE macro is defined in my cmake file. I've been able to get
> connection but key exchange fails somehow.
> > I've been trying to solve the problem for few days now and being a
> beginner in programming it is starting to get quite frustrating so I've
> decided to reach out for help.
> >
> > Best regards
> >
> >
>
>
>