Limiting number of parts allowed in network packets as a safeguard for weaker computers, as discussed in #876. Configurable, of course.

src/main/resources/application.conf

@@ -925,6 +925,14 @@ opencomputers {
       # not apply to HTTP traffic.
       maxNetworkPacketSize: 8192
 
+      # The maximum number of "data parts" a network packet is allowed to have.
+      # When sending a network message, from Lua this may look like so:
+      #  component.modem.broadcast(port, "first", true, "third", 123)
+      # This limits how many arguments can be passed and are wrapped into a
+      # packet. This limit mostly serves as a protection for lower-tier
+      # computers, to avoid them getting nuked by more powerful computers.
+      maxNetworkPacketParts: 8
+
       # The maximum number of ports a single network card can have opened at
       # any given time.
       maxOpenPorts: 16

src/main/scala/li/cil/oc/Settings.scala

@@ -271,6 +271,7 @@ class Settings(val config: Config) {
   val inputUsername = config.getBoolean("misc.inputUsername")
   val maxClipboard = config.getInt("misc.maxClipboard") max 0
   val maxNetworkPacketSize = config.getInt("misc.maxNetworkPacketSize") max 0
+  val maxNetworkPacketParts = config.getInt("misc.maxNetworkPacketParts") max 0
   val maxOpenPorts = config.getInt("misc.maxOpenPorts") max 0
   val maxWirelessRange = config.getDouble("misc.maxWirelessRange") max 0
   val rTreeMaxEntries = 10

src/main/scala/li/cil/oc/server/network/Network.scala

@@ -662,17 +662,22 @@ object Network extends api.detail.NetworkAPI {
   // ----------------------------------------------------------------------- //
 
   class Packet(var source: String, var destination: String, var port: Int, var data: Array[AnyRef], var ttl: Int = 5) extends api.network.Packet {
-    val size = Option(data).fold(0)(_.foldLeft(0)((acc, arg) => {
+    val size = Option(data).fold(0)(values => {
-      acc + (arg match {
+      if (values.length > Settings.get.maxNetworkPacketParts) {
-        case null | Unit | None => 4
+        throw new IllegalArgumentException("packet has too many parts")
-        case _: java.lang.Boolean => 4
+      }
-        case _: java.lang.Integer => 4
+      values.length * 2 + values.foldLeft(0)((acc, arg) => {
-        case _: java.lang.Double => 8
+        acc + (arg match {
-        case value: java.lang.String => value.length max 1
+          case null | Unit | None => 4
-        case value: Array[Byte] => value.length max 1
+          case _: java.lang.Boolean => 4
-        case _ => throw new IllegalArgumentException("unsupported data type")
+          case _: java.lang.Integer => 4
+          case _: java.lang.Double => 8
+          case value: java.lang.String => value.length max 1
+          case value: Array[Byte] => value.length max 1
+          case _ => throw new IllegalArgumentException("unsupported data type")
+        })
       })
-    }))
+    })
 
     override def hop() = new Packet(source, destination, port, data, ttl - 1)