decode XferInner only when appropriate

That is, make sure that the signature is valid before decoding

lib/floof/distributor.ex

@@ -59,12 +59,12 @@ defmodule Floof.Distributor do
   end
 
   @impl true
-  def handle_cast({:xfer, {origin, dcdhash, dcd, attrs}}, state) do
+  def handle_cast({:xfer, {origin, dcdhash, dcd}}, state) do
     # we split the state such that only the parts necessary get
     # copied into the spawned-off process
     fconf = dstate(state, :fconf)
 
-    if check_incoming(fconf, dcdhash, dcd, attrs) do
+    if check_incoming(fconf, dcdhash, dcd) do
       trgs = MapSet.delete(dstate(state, :trgs), origin)
       Floof.DistributorSeen.mark_seen(dcdhash)
 
@@ -92,7 +92,7 @@ defmodule Floof.Distributor do
     {:noreply, dstate(state, trgs: MapSet.delete(dstate(state, :trgs), pid))}
   end
 
-  defp check_incoming(fconf, dcdhash, dcd, attrs) do
+  defp check_incoming(fconf, dcdhash, dcd) do
     {:XferBlob, source, ttl, _, {:Signature, sigalgo, sigval}, xfinner} = dcd
 
     case sigalgo do
@@ -113,7 +113,7 @@ defmodule Floof.Distributor do
                 Logger.warn("packet in processing expired (out of hops): #{inspect(xfinner)}")
                 false
 
-              not check_filters(fconf, dcd, attrs) ->
+              not check_filters(fconf, dcd) ->
                 Logger.debug("packet discarded according to filters: #{inspect(xfinner)}")
                 false
 
@@ -138,8 +138,9 @@ defmodule Floof.Distributor do
     end
   end
 
-  defp check_filters(fconf, {:XferBlob, _, _, markers, _, _}, attrs) do
+  defp check_filters(fconf, {:XferBlob, _, _, markers, _, xfinner}) do
     try do
+      {:ok, {:XferInner, _, attrs, _, _}} = :FloofProtocol.decode(:XferInner, xfinner)
       cond do
         not check_filters_markers2(fconfig(fconf, :markers), markers) -> false
         not check_filters_markers2(fconfig(fconf, :attrs), attrs) -> false

lib/floof/message.ex

@@ -5,9 +5,8 @@ defmodule Floof.Message do
 
   def emit(xf) do
     {:XferBlob, _, _, _, _, xfinner} = xf
-    {:ok, {:XferInner, _, attrs, _, _}} = :FloofProtocol.decode(:XferInner, xfinner)
     mhash = :crypto.hash(:blake2b, xfinner)
-    GenServer.cast(Floof.Distributor, {:xfer, {self(), mhash, xf, attrs}})
+    GenServer.cast(Floof.Distributor, {:xfer, {self(), mhash, xf}})
     mhash
   end