Re: [PATCH] diffie-hellman-group-exchange-sha256

[Aris Adamantiadis <aris@xxxxxxxxxxxx>]

Hi Yanis,

Thank you for your patches, I'll review them asap. The kex bug with
dropbear is interesting. I don't have any dropbear installed nearby,
could you drop me some logs from openssh trying to negociate a
curve25519 kex with dropbear? It's probably a bug in dropbear (I don't
think we implemented our specs wrong :p) but the protocol is so simple I
don't see why OpenSSH wouldn't exhibit the same problem.

Thanks,

Aris
Le 28/01/15 20:35, Yanis Kurganov a écrit :
> It was a long nice evening, but I found a problem =)))
> It's only with dropbear & curve25519-sha256@xxxxxxxxxx
> <mailto:curve25519-sha256@xxxxxxxxxx> kex algo.
>
> See logs from original libssh from master with dropbear
> (samplesshd-cb_server_from_dropbear_client_original.log):
> [2015/01/28 21:15:37.870161, 3] ssh_packet_process:  Dispatching
> handler for packet type 30
> [2015/01/28 21:15:37.870200, 3] ssh_packet_kexdh_init:  Received
> SSH_MSG_KEXDH_INIT
> [2015/01/28 21:15:37.913360, 2] ssh_server_curve25519_init:
>  SSH_MSG_KEX_ECDH_REPLY sent
> [2015/01/28 21:15:37.913389, 2] ssh_server_curve25519_init:
>  SSH_MSG_NEWKEYS sent
> [2015/01/28 21:15:37.916199, 3] ssh_packet_process:  Dispatching
> handler for packet type 30
> [2015/01/28 21:15:37.916205, 3] ssh_packet_kexdh_init:  Received
> SSH_MSG_KEXDH_INIT
> [2015/01/28 21:15:37.916211, 1] ssh_packet_kexdh_init:  Invalid state
> for SSH_MSG_KEXDH_INIT (!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!)
> [2015/01/28 21:15:37.916228, 3] ssh_packet_process:  Dispatching
> handler for packet type 21
> [2015/01/28 21:15:37.916234, 2] ssh_packet_newkeys:  Received
> SSH_MSG_NEWKEYS
>
> So, libssh received SSH_MSG_KEXDH_INIT packet twice!
> It seems a bug in dropbear!
>
> Let's see logs from original libssh from master with
> openssh (samplesshd-cb_server_from_openssh_client_original.log):
> [2015/01/28 21:14:34.509147, 3] ssh_packet_process:  Dispatching
> handler for packet type 30
> [2015/01/28 21:14:34.509154, 3] ssh_packet_kexdh_init:  Received
> SSH_MSG_KEXDH_INIT
> [2015/01/28 21:14:34.544184, 2] ssh_server_curve25519_init:
>  SSH_MSG_KEX_ECDH_REPLY sent
> [2015/01/28 21:14:34.544235, 2] ssh_server_curve25519_init:
>  SSH_MSG_NEWKEYS sent
> [2015/01/28 21:14:34.559318, 3] ssh_packet_process:  Dispatching
> handler for packet type 21
> [2015/01/28 21:14:34.559346, 2] ssh_packet_newkeys:  Received
> SSH_MSG_NEWKEYS
>
> I fixed this in my code. I just don't set session->session_state =
> SSH_SESSION_STATE_ERROR; as in original code.
> Logs and new patch (on fresh master) are attached!
>
> P.S. pkd_hello works fine. All tests have been passed successfully.
>