Re: Key exchange fail

[Yusuf Saka <yusufsaka5481@xxxxxxxxx>]

Also here is what valgrind says


==52658== Conditional jump or move depends on uninitialised value(s)
==52658==    at 0x48A8B7C: ssh_execute_server_request (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48A8F17: ssh_execute_server_callbacks (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48A9057: ssh_message_queue (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48A99DC: ssh_packet_service_request (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48B5EA8: ssh_packet_process (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48B5825: ssh_packet_socket_callback (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48C5C07: ssh_socket_pollcallback (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48C0598: ssh_poll_ctx_dopoll (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x48C0A57: ssh_event_dopoll (in
/usr/lib/x86_64-linux-gnu/libssh.so.4.10.1)
==52658==    by 0x10BB63: SSHServer::handle_session(ssh_event_struct*,
ssh_session_struct*) (ssh_server.cpp:220)
==52658==    by 0x10B571: SSHServer::start() (ssh_server.cpp:110)
==52658==    by 0x10A7A4: main (main.cpp:21)
==52658==  Uninitialised value was created by a stack allocation
==52658==    at 0x10B7C5: SSHServer::handle_session(ssh_event_struct*,
ssh_session_struct*) (ssh_server.cpp:147)



On Fri, Mar 28, 2025 at 10:02 AM Yusuf Saka <yusufsaka5481@xxxxxxxxx> wrote:

> 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
>> >
>> >
>>
>>
>>