feat: electra slashing, proposer_index & compute_sync_committees changes (#1417)

Co-authored-by: Rodrigo Oliveri <[email protected]>

Author: LeanSerra

lib/lambda_ethereum_consensus/state_transition/accessors.ex

@@ -17,7 +17,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
   alias Types.SyncCommittee
   alias Types.Validator
 
-  @max_random_byte 2 ** 8 - 1
+  @max_random_byte 2 ** 16 - 1
 
   @doc """
   Compute the correct sync committee for a given `epoch`.
@@ -118,13 +118,16 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
            |> Misc.compute_shuffled_index(active_validator_count, seed) do
       candidate_index = Aja.Vector.at!(active_validator_indices, shuffled_index)
 
-      <<_::binary-size(rem(index, 32)), random_byte, _::binary>> =
-        SszEx.hash(seed <> Misc.uint64_to_bytes(div(index, 32)))
+      random_bytes = SszEx.hash(seed <> Misc.uint_to_bytes(div(index, 16), 64))
+      offset = rem(index, 16) * 2
 
-      max_effective_balance = ChainSpec.get("MAX_EFFECTIVE_BALANCE")
+      bytes = binary_part(random_bytes, offset, 2) <> <<0::48>>
+      random_value = Misc.bytes_to_uint64(bytes)
+
+      max_effective_balance = ChainSpec.get("MAX_EFFECTIVE_BALANCE_ELECTRA")
       effective_balance = Aja.Vector.at!(validators, candidate_index).effective_balance
 
-      if effective_balance * @max_random_byte >= max_effective_balance * random_byte do
+      if effective_balance * @max_random_byte >= max_effective_balance * random_value do
         {:ok, sync_committee_indices |> List.insert_at(0, candidate_index)}
       else
         {:ok, sync_committee_indices}

lib/lambda_ethereum_consensus/state_transition/epoch_processing.ex

@@ -117,17 +117,17 @@ defmodule LambdaEthereumConsensus.StateTransition.EpochProcessing do
     adjusted_total_slashing_balance =
       min(slashed_sum * proportional_slashing_multiplier, total_balance)
 
+    penalty_per_effective_balance_increment =
+      div(adjusted_total_slashing_balance, div(total_balance, increment))
+
     new_state =
       validators
       |> Stream.with_index()
       |> Enum.reduce(state, fn {validator, index}, acc ->
         if validator.slashed and
              epoch + div(epochs_per_slashings_vector, 2) == validator.withdrawable_epoch do
-          # increment factored out from penalty numerator to avoid uint64 overflow
-          penalty_numerator =
-            div(validator.effective_balance, increment) * adjusted_total_slashing_balance
-
-          penalty = div(penalty_numerator, total_balance) * increment
+          effective_balance_increments = div(validator.effective_balance, increment)
+          penalty = penalty_per_effective_balance_increment * effective_balance_increments
 
           BeaconState.decrease_balance(acc, index, penalty)
         else

lib/lambda_ethereum_consensus/state_transition/misc.ex

@@ -12,7 +12,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
   alias LambdaEthereumConsensus.Utils
   alias Types.BeaconState
 
-  @max_random_byte 2 ** 8 - 1
+  @max_random_byte 2 ** 16 - 1
 
   @doc """
   Returns the Unix timestamp at the start of the given slot
@@ -130,23 +130,26 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
         ) ::
           {:ok, Types.validator_index()}
   def compute_proposer_index(state, indices, seed) do
-    max_effective_balance = ChainSpec.get("MAX_EFFECTIVE_BALANCE")
+    max_effective_balance = ChainSpec.get("MAX_EFFECTIVE_BALANCE_ELECTRA")
     total = Aja.Vector.size(indices)
 
     Stream.iterate(0, &(&1 + 1))
     |> Stream.map(fn i ->
       {:ok, index} = compute_shuffled_index(rem(i, total), total, seed)
       candidate_index = Aja.Vector.at!(indices, index)
 
-      <<_::binary-size(rem(i, 32)), random_byte, _::binary>> =
-        SszEx.hash(seed <> uint_to_bytes(div(i, 32), 64))
+      random_bytes = SszEx.hash(seed <> uint_to_bytes(div(i, 16), 64))
+      offset = rem(i, 16) * 2
+
+      bytes = binary_part(random_bytes, offset, 2) <> <<0::48>>
+      random_value = bytes_to_uint64(bytes)
 
       effective_balance = Aja.Vector.at(state.validators, candidate_index).effective_balance
 
-      {effective_balance, random_byte, candidate_index}
+      {effective_balance, random_value, candidate_index}
     end)
-    |> Stream.filter(fn {effective_balance, random_byte, _} ->
-      effective_balance * @max_random_byte >= max_effective_balance * random_byte
+    |> Stream.filter(fn {effective_balance, random_value, _} ->
+      effective_balance * @max_random_byte >= max_effective_balance * random_value
     end)
     |> Enum.take(1)
     |> then(fn [{_, _, candidate_index}] -> {:ok, candidate_index} end)

test/spec/runners/sync.ex

@@ -32,6 +32,14 @@ defmodule SyncTestRunner do
   def run_test_case(%SpecTestCase{} = testcase) do
     original_engine_api_config = Application.fetch_env!(:lambda_ethereum_consensus, EngineApi)
 
+    on_exit(fn ->
+      Application.put_env(
+        :lambda_ethereum_consensus,
+        EngineApi,
+        original_engine_api_config
+      )
+    end)
+
     Application.put_env(
       :lambda_ethereum_consensus,
       EngineApi,
@@ -41,13 +49,6 @@ defmodule SyncTestRunner do
     {:ok, _pid} = SyncTestRunner.EngineApiMock.start_link([])
 
     ForkChoiceTestRunner.run_test_case(testcase)
-
-    # TODO: we should do this cleanup even if the test crashes/fails
-    Application.put_env(
-      :lambda_ethereum_consensus,
-      EngineApi,
-      original_engine_api_config
-    )
   end
 end