Compatibile with OpenSSH

2 files changed, 7 insertions, 4 deletions

diff --git a/lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb b/lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb
index da47ec2..8fb69e8 100644
--- a/lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb
+++ b/lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb
@@ -19,7 +19,10 @@ module Net::SSH::Transport::Kex
 
       # Compute the number of bits needed for the given number of bytes.
       def compute_need_bits
-        need_bits = data[:need_bytes] * 8
+
+        # for Compatibility: OpenSSH requires (need_bits * 2 + 1) length of parameter
+        need_bits = data[:need_bytes] * 8 * 2 + 1
+
         if need_bits < MINIMUM_BITS
           need_bits = MINIMUM_BITS
         elsif need_bits > MAXIMUM_BITS
@@ -74,4 +77,4 @@ module Net::SSH::Transport::Kex
       end
   end
 
-end
\ No newline at end of file
+end
diff --git a/test/transport/kex/test_diffie_hellman_group_exchange_sha1.rb b/test/transport/kex/test_diffie_hellman_group_exchange_sha1.rb
index dc5a2bc..b19afae 100644
--- a/test/transport/kex/test_diffie_hellman_group_exchange_sha1.rb
+++ b/test/transport/kex/test_diffie_hellman_group_exchange_sha1.rb
@@ -18,7 +18,7 @@ module Transport; module Kex
 
     def test_exchange_with_fewer_than_maximum_bits_uses_need_bits
       dh_options :need_bytes => 500
-      need_bits(4000)
+      need_bits(8001)
       assert_nothing_raised { exchange! }
     end
 
@@ -89,4 +89,4 @@ module Transport; module Kex
       end
   end
 
-end; end
\ No newline at end of file
+end; end