RE: libssh 0.8.4 with Cisco router

[Meng Hourk Tan <mtan@xxxxxxxxxx>]

Hi Andreas,


Here's the patch compliant to your coding style.


And I'm glad it helped you Jijo.

Regards,

Meng

________________________________
De : Andreas Schneider <asn@xxxxxxxxxxxxxx>
Envoyé : mercredi 24 octobre 2018 08:51
À : libssh@xxxxxxxxxx
Cc : Meng Hourk Tan; jijo7thomas@xxxxxxxxx
Objet : Re: libssh 0.8.4 with Cisco router

On Tuesday, 23 October 2018 18:09:25 CEST Meng Hourk Tan wrote:
> Hello,

Hello Meng,

> I had the same issue with some Cisco router:
>
> Some Cisco IOS do not send kex if they send the banner last (libssh as a
> client sent it first).
>
> In this situation, both libssh client and Cisco IOS server hang.
>
> Libssh client should send kex init as soon as banners are exchanged.

Thanks you very much for your patch.

Could you please change the patch to follow our coding style:

+            if (ssh_set_client_kex(session) < 0) {
+                goto error;
+            }

should for example use a helper variable for easier debugging:

rc = ssh_set_client_kex(session);
if (rc != SSH_OK) {
    goto error;
}



Thanks,



        Andreas

--
Andreas Schneider                 asn@xxxxxxxxxxxxxx
GPG-ID:     8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D


From c12bb4c2c1d3e2a7ac03ab7400c6be023f21df12 Mon Sep 17 00:00:00 2001
From: Meng Tan <mtan@xxxxxxxxxx>
Date: Wed, 24 Oct 2018 10:43:17 +0200
Subject: [PATCH] client: Send KEX as soon as banners are exchanged

Signed-off-by: Meng Tan <mtan@xxxxxxxxxx>
---
 src/client.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/client.c b/src/client.c
index 859a86c6..d4b7ee57 100644
--- a/src/client.c
+++ b/src/client.c
@@ -411,6 +411,14 @@ static void ssh_client_connection_callback(ssh_session session)

             ssh_packet_set_default_callbacks(session);
             session->session_state = SSH_SESSION_STATE_INITIAL_KEX;
+            rc = ssh_set_client_kex(session);
+            if (rc != SSH_OK) {
+                goto error;
+            }
+            rc = ssh_send_kex(session, 0);
+            if (rc < 0) {
+                goto error;
+            }
             set_status(session, 0.5f);

             break;
@@ -420,14 +428,19 @@ static void ssh_client_connection_callback(ssh_session session)
         case SSH_SESSION_STATE_KEXINIT_RECEIVED:
             set_status(session,0.6f);
             ssh_list_kex(&session->next_crypto->server_kex);
-            if (ssh_set_client_kex(session) < 0) {
-                goto error;
+            if (session->next_crypto->client_kex.methods[0] == NULL) {
+                /* in rekeying state if next_crypto client_kex is empty */
+                rc = ssh_set_client_kex(session);
+                if (rc != SSH_OK) {
+                    goto error;
+                }
+                rc = ssh_send_kex(session, 0);
+                if (rc < 0) {
+                    goto error;
+                }
             }
             if (ssh_kex_select_methods(session) == SSH_ERROR)
                 goto error;
-            if (ssh_send_kex(session, 0) < 0) {
-                goto error;
-            }
             set_status(session,0.8f);
             session->session_state=SSH_SESSION_STATE_DH;
             if (dh_handshake(session) == SSH_ERROR) {
--
2.11.0