add pubkey_verifier class to framework

this class provides a new way to do
public key only verification tests
for SSH

7321

lib/net/ssh/pubkey_verifier.rb

@@ -0,0 +1,59 @@
+require 'net/ssh'
+
+module Net
+  module SSH
+
+    class PubkeyVerifier
+      include Net::SSH::Transport::Constants
+      include Net::SSH::Authentication::Constants
+
+      attr_accessor :host, :key, :options, :user
+
+      def initialize(host,user, opts)
+        @host = host
+        # Parse Keyfile out into a PKey object
+        pubkey_file = opts.fetch(:pubkey_file)
+        @key = Net::SSH::KeyFactory.load_public_key(pubkey_file)
+        @user = user
+
+        # Always set auth methods to ONLY publickey regardless
+        # of what the user sends
+        opts[:auth_methods] = ['publickey']
+        @options = Net::SSH.configuration_for(host, opts.fetch(:config, true)).merge(opts)
+      end
+
+      def auth_session(transport)
+        Net::SSH::Authentication::Session.new(transport,options)
+      end
+
+      def ssh_transport
+        Net::SSH::Transport::Session.new(host,options)
+      end
+
+      def verify
+        transport = ssh_transport
+        auth      = auth_session(transport)
+
+        transport.send_message(transport.service_request("ssh-userauth"))
+        auth.expect_message(SERVICE_ACCEPT)
+
+        # The initial public key exchange
+        pubkey_method = Net::SSH::Authentication::Methods::Publickey.new(auth)
+        pubkey_method.send(:send_request, key,user, "ssh-connection")
+
+        # Check the response to see if the public key is good
+        response_message = auth.next_message
+        case response_message.type
+          when USERAUTH_PK_OK
+            true
+          when USERAUTH_FAILURE
+            false
+          else
+            raise Net::SSH::Exception, "unexpected reply to USERAUTH_REQUEST: #{response_message.type} (#{response_message.inspect})"
+        end
+      end
+
+
+    end
+  end
+end