Fix TCP Requester #recv_reply

Author: jsaubry

lib/resolv.rb

@@ -929,8 +929,11 @@ def initialize(host, port=Port)
         end
 
         def recv_reply(readable_socks)
-          len = readable_socks[0].read(2).unpack('n')[0]
+          len_data = readable_socks[0].read(2)
+          raise Errno::ECONNRESET if len_data.nil?
+          len = len_data.unpack('n')[0]
           reply = @socks[0].read(len)
+          raise Errno::ECONNRESET if reply.nil?
           return reply, nil
         end
 

test/resolv/test_dns.rb

@@ -822,4 +822,63 @@ def test_multiple_servers_with_timeout_and_truncated_tcp_fallback
       end
     end
   end
+
+  def test_tcp_connection_closed_before_length
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
+
+  def test_tcp_connection_closed_after_length
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.send([100].pack('n'), 0)
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
 end