[JSch-users] diffie-hellman-group-exchange-sha1 hangs forever

[Tamir G. <tam...@gm...>]

Hi,

I was trying to use diffie-hellman-group-exchange-sha1 to connect to
some servers, but every time the connection hanged forever before
establishing.

After doing some digging, found that the DHGEX class in the init()
function is calling session.write(packet) with the command
SSH_MSG_KEX_DH_GEX_REQUEST.
However, in Session.write(), if in_kex it checks if the command is
part of some subset of commands and otherwise sleeps and loop forever.
To solve this issue I added the 4 GEX related commands to the subset
of commands which are expected during key exchange, and it seem to fix
the issue and connect successfully.

Here is the diff of my changes, hopefully this is the correct solution
for the issue:

$ diff -Naur Session.java Session_new.java
--- Session.java        2007-03-05 13:51:10.000000000 +0200
+++ Session_new.java    2007-03-17 12:41:18.656250000 +0200
@@ -46,6 +46,10 @@
   static final int SSH_MSG_NEWKEYS=                        21;
   static final int SSH_MSG_KEXDH_INIT=                     30;
   static final int SSH_MSG_KEXDH_REPLY=                    31;
+  static final int SSH_MSG_KEX_DH_GEX_GROUP=               31;
+  static final int SSH_MSG_KEX_DH_GEX_INIT=                32;
+  static final int SSH_MSG_KEX_DH_GEX_REPLY=               33;
+  static final int SSH_MSG_KEX_DH_GEX_REQUEST=             34;
   static final int SSH_MSG_GLOBAL_REQUEST=                 80;
   static final int SSH_MSG_REQUEST_SUCCESS=                81;
   static final int SSH_MSG_REQUEST_FAILURE=                82;
@@ -1132,7 +1136,11 @@
          command==SSH_MSG_NEWKEYS ||
          command==SSH_MSG_KEXDH_INIT ||
          command==SSH_MSG_KEXDH_REPLY ||
-         command==SSH_MSG_DISCONNECT){
+         command==SSH_MSG_DISCONNECT ||
+         command==SSH_MSG_KEX_DH_GEX_GROUP ||
+         command==SSH_MSG_KEX_DH_GEX_INIT ||
+         command==SSH_MSG_KEX_DH_GEX_REPLY ||
+         command==SSH_MSG_KEX_DH_GEX_REQUEST){
         break;
       }
       try{Thread.sleep(10);}


Thanks,
Tamir
http://www.tamirgal.com/home/dev.aspx