fix: Reject oversized TMPing messages

src/xrpld/overlay/Message.h

@@ -19,6 +19,9 @@
 namespace xrpl {
 
 constexpr std::size_t kMaximumMessageSize = megabytes(64);
+// Ping messages should be much smaller than the maximum message size,
+// so we define a separate limit for them.
+constexpr std::size_t kMaximumPingMessageSize = kilobytes(1);
 
 // VFALCO NOTE If we forward declare Message and write out shared_ptr
 //             instead of using the in-class type alias, we can remove the

src/xrpld/overlay/detail/ProtocolMessage.h

@@ -359,6 +359,13 @@ invokeProtocolMessage(Buffers const& buffers, Handler& handler, std::size_t& hin
         return result;
     }
 
+    if (header->messageType == protocol::mtPING &&
+        header->uncompressedSize + header->headerSize > kMaximumPingMessageSize)
+    {
+        result.second = make_error_code(boost::system::errc::message_size);
+        return result;
+    }
+
     // We don't have the whole message yet. This isn't an error but we have
     // nothing to do.
     if (header->totalWireSize > size)