Fix a stack trace when no SMB response is received

Author: hdm

modules/exploits/windows/smb/ms17_010_eternalblue.rb

@@ -187,6 +187,10 @@ def smb_eternalblue(process_name, grooms)
       print_status("Receiving response from exploit packet")
       code, raw = smb1_get_response(sock)
 
+      if code.nil?
+        print_error("Did not receive a response from exploit packet")
+      end
+
       if code == 0xc000000d #STATUS_INVALID_PARAMETER (0xC000000D)
         print_good("ETERNALBLUE overwrite completed successfully (0xC000000D)!")
       end
@@ -226,6 +230,10 @@ def smb1_anonymous_connect_ipc()
 
     code, raw, response = smb1_get_response(sock)
 
+    if code.nil?
+      raise RubySMB::Error::UnexpectedStatusCode, "No response to login request"
+    end
+
     unless code == 0 # WindowsError::NTStatus::STATUS_SUCCESS
       raise RubySMB::Error::UnexpectedStatusCode, "Error with anonymous login"
     end
@@ -290,6 +298,7 @@ def smb1_free_hole(start)
 
   def smb1_get_response(sock)
     raw = sock.get_once
+    return nil unless raw
     response = RubySMB::SMB1::SMBHeader.read(raw[4..-1])
     code = response.nt_status
     return code, raw, response