Land rapid7#5518, TFTP::Client retransmit lost data blocks on upload

Author: Brent Cook

lib/rex/proto/tftp/client.rb

@@ -295,38 +295,59 @@ def send_data(host,port)
     end
     sent_data = 0
     sent_blocks = 0
+    send_retries = 0
     expected_blocks = data_blocks.size
     expected_size = data_blocks.join.size
     if block_given?
       yield "Source file: #{self.local_file =~ /^DATA:/ ? "(Data)" : self.remote_file}, destination file: #{self.remote_file}"
       yield "Sending #{expected_size} bytes (#{expected_blocks} blocks)"
     end
     data_blocks.each_with_index do |data_block,idx|
-      req = [OpData, (idx + 1), data_block].pack("nnA*")
-      if self.server_sock.sendto(req, host, port) > 0
-        sent_data += data_block.size
-      end
-      res = self.server_sock.recvfrom(65535)
-      if res
-        code, type, msg = parse_tftp_response(res[0])
-        if code == 4
-          sent_blocks += 1
-          yield "Sent #{data_block.size} bytes in block #{sent_blocks}" if block_given?
-        else
-          if block_given?
-            yield "Got an unexpected response: Code:%d, Type:%d, Message:'%s'. Aborting." % [code, type, msg]
+      loop do
+        req = [OpData, (idx + 1), data_block].pack("nnA*")
+        if self.server_sock.sendto(req, host, port) <= 0
+          send_retries += 1
+          if send_retries > 100
+            break
+          else
+            next
+          end
+        end
+        send_retries = 0
+        res = self.server_sock.recvfrom(65535)
+        if res
+          code, type, msg = parse_tftp_response(res[0])
+          if code == 4
+            if type == idx + 1
+              sent_blocks += 1
+              sent_data += data_block.size
+              yield "Sent #{data_block.size} bytes in block #{idx+1}" if block_given?
+              break
+            else
+              next
+            end
+          else
+            if block_given?
+              yield "Got an unexpected response: Code:%d, Type:%d, Message:'%s'. Aborting." % [code, type, msg]
+            end
+            break
           end
-          break
         end
       end
     end
+
+    if send_retries > 100
+      yield "Too many send retries, aborted"
+    end
+
     if block_given?
       if(sent_data == expected_size)
         yield("Transferred #{sent_data} bytes in #{sent_blocks} blocks, upload complete!")
       else
         yield "Upload complete, but with errors."
       end
     end
+
     if sent_data == expected_size
     self.status = {:success => [
         self.local_file,