Part 2 of block chain service refactor - move process attestation (#4672

)

beacon-chain/blockchain/BUILD.bazel

@@ -7,6 +7,8 @@ go_library(
         "info.go",
         "log.go",
         "metrics.go",
+        "process_attestation.go",
+        "process_attestation_helpers.go",
         "process_block.go",
         "process_block_helpers.go",
         "receive_attestation.go",
@@ -17,6 +19,7 @@ go_library(
     visibility = ["//beacon-chain:__subpackages__"],
     deps = [
         "//beacon-chain/blockchain/forkchoice:go_default_library",
+        "//beacon-chain/cache:go_default_library",
         "//beacon-chain/cache/depositcache:go_default_library",
         "//beacon-chain/core/blocks:go_default_library",
         "//beacon-chain/core/epoch/precompute:go_default_library",
@@ -64,6 +67,7 @@ go_test(
     size = "medium",
     srcs = [
         "chain_info_test.go",
+        "process_attestation_test.go",
         "process_block_test.go",
         "receive_attestation_test.go",
         "receive_block_test.go",

beacon-chain/blockchain/process_attestation.go

@@ -0,0 +1,128 @@
+package blockchain
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/gogo/protobuf/proto"
+	"github.com/pkg/errors"
+	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/shared/bytesutil"
+	"go.opencensus.io/trace"
+)
+
+// ErrTargetRootNotInDB returns when the target block root of an attestation cannot be found in the
+// beacon database.
+var ErrTargetRootNotInDB = errors.New("target root does not exist in db")
+
+// onAttestation is called whenever an attestation is received, verifies the attestation is valid and saves
+/// it to the DB.
+//
+// Spec pseudocode definition:
+//   def on_attestation(store: Service, attestation: Attestation) -> None:
+//    """
+//    Run ``on_attestation`` upon receiving a new ``attestation`` from either within a block or directly on the wire.
+//
+//    An ``attestation`` that is asserted as invalid may be valid at a later time,
+//    consider scheduling it for later processing in such case.
+//    """
+//    target = attestation.data.target
+//
+//    # Attestations must be from the current or previous epoch
+//    current_epoch = compute_epoch_at_slot(get_current_slot(store))
+//    # Use GENESIS_EPOCH for previous when genesis to avoid underflow
+//    previous_epoch = current_epoch - 1 if current_epoch > GENESIS_EPOCH else GENESIS_EPOCH
+//    assert target.epoch in [current_epoch, previous_epoch]
+//    assert target.epoch == compute_epoch_at_slot(attestation.data.slot)
+//
+//    # Attestations target be for a known block. If target block is unknown, delay consideration until the block is found
+//    assert target.root in store.blocks
+//    # Attestations cannot be from future epochs. If they are, delay consideration until the epoch arrives
+//    base_state = store.block_states[target.root].copy()
+//    assert store.time >= base_state.genesis_time + compute_start_slot_at_epoch(target.epoch) * SECONDS_PER_SLOT
+//
+//    # Attestations must be for a known block. If block is unknown, delay consideration until the block is found
+//    assert attestation.data.beacon_block_root in store.blocks
+//    # Attestations must not be for blocks in the future. If not, the attestation should not be considered
+//    assert store.blocks[attestation.data.beacon_block_root].slot <= attestation.data.slot
+//
+//    # Service target checkpoint state if not yet seen
+//    if target not in store.checkpoint_states:
+//        process_slots(base_state, compute_start_slot_at_epoch(target.epoch))
+//        store.checkpoint_states[target] = base_state
+//    target_state = store.checkpoint_states[target]
+//
+//    # Attestations can only affect the fork choice of subsequent slots.
+//    # Delay consideration in the fork choice until their slot is in the past.
+//    assert store.time >= (attestation.data.slot + 1) * SECONDS_PER_SLOT
+//
+//    # Get state at the `target` to validate attestation and calculate the committees
+//    indexed_attestation = get_indexed_attestation(target_state, attestation)
+//    assert is_valid_indexed_attestation(target_state, indexed_attestation)
+//
+//    # Update latest messages
+//    for i in indexed_attestation.attesting_indices:
+//        if i not in store.latest_messages or target.epoch > store.latest_messages[i].epoch:
+//            store.latest_messages[i] = LatestMessage(epoch=target.epoch, root=attestation.data.beacon_block_root)
+func (s *Service) onAttestation(ctx context.Context, a *ethpb.Attestation) ([]uint64, error) {
+	ctx, span := trace.StartSpan(ctx, "blockchain.onAttestation")
+	defer span.End()
+
+	tgt := proto.Clone(a.Data.Target).(*ethpb.Checkpoint)
+	tgtSlot := helpers.StartSlot(tgt.Epoch)
+
+	if helpers.SlotToEpoch(a.Data.Slot) != a.Data.Target.Epoch {
+		return nil, fmt.Errorf("data slot is not in the same epoch as target %d != %d", helpers.SlotToEpoch(a.Data.Slot), a.Data.Target.Epoch)
+	}
+
+	// Verify beacon node has seen the target block before.
+	if !s.beaconDB.HasBlock(ctx, bytesutil.ToBytes32(tgt.Root)) {
+		return nil, ErrTargetRootNotInDB
+	}
+
+	// Verify attestation target has had a valid pre state produced by the target block.
+	baseState, err := s.verifyAttPreState(ctx, tgt)
+	if err != nil {
+		return nil, err
+	}
+
+	// Verify attestation target is from current epoch or previous epoch.
+	if err := s.verifyAttTargetEpoch(ctx, baseState.GenesisTime, uint64(time.Now().Unix()), tgt); err != nil {
+		return nil, err
+	}
+
+	// Verify Attestations cannot be from future epochs.
+	if err := helpers.VerifySlotTime(baseState.GenesisTime, tgtSlot); err != nil {
+		return nil, errors.Wrap(err, "could not verify attestation target slot")
+	}
+
+	// Verify attestation beacon block is known and not from the future.
+	if err := s.verifyBeaconBlock(ctx, a.Data); err != nil {
+		return nil, errors.Wrap(err, "could not verify attestation beacon block")
+	}
+
+	// Service target checkpoint state if not yet seen.
+	baseState, err = s.saveCheckpointState(ctx, baseState, tgt)
+	if err != nil {
+		return nil, err
+	}
+
+	// Verify attestations can only affect the fork choice of subsequent slots.
+	if err := helpers.VerifySlotTime(baseState.GenesisTime, a.Data.Slot+1); err != nil {
+		return nil, err
+	}
+
+	// Use the target state to to validate attestation and calculate the committees.
+	indexedAtt, err := s.verifyAttestation(ctx, baseState, a)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := s.beaconDB.SaveAttestation(ctx, a); err != nil {
+		return nil, err
+	}
+
+	return indexedAtt.AttestingIndices, nil
+}

beacon-chain/blockchain/process_attestation_helpers.go

@@ -0,0 +1,135 @@
+package blockchain
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/gogo/protobuf/proto"
+	"github.com/pkg/errors"
+	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/cache"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/state"
+	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
+	"github.com/prysmaticlabs/prysm/shared/bytesutil"
+	"github.com/prysmaticlabs/prysm/shared/params"
+	"go.opencensus.io/trace"
+)
+
+// verifyAttPreState validates input attested check point has a valid pre-state.
+func (s *Service) verifyAttPreState(ctx context.Context, c *ethpb.Checkpoint) (*pb.BeaconState, error) {
+	baseState, err := s.beaconDB.State(ctx, bytesutil.ToBytes32(c.Root))
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not get pre state for slot %d", helpers.StartSlot(c.Epoch))
+	}
+	if baseState == nil {
+		return nil, fmt.Errorf("pre state of target block %d does not exist", helpers.StartSlot(c.Epoch))
+	}
+	return baseState, nil
+}
+
+// verifyAttTargetEpoch validates attestation is from the current or previous epoch.
+func (s *Service) verifyAttTargetEpoch(ctx context.Context, genesisTime uint64, nowTime uint64, c *ethpb.Checkpoint) error {
+	currentSlot := (nowTime - genesisTime) / params.BeaconConfig().SecondsPerSlot
+	currentEpoch := helpers.SlotToEpoch(currentSlot)
+	var prevEpoch uint64
+	// Prevents previous epoch under flow
+	if currentEpoch > 1 {
+		prevEpoch = currentEpoch - 1
+	}
+	if c.Epoch != prevEpoch && c.Epoch != currentEpoch {
+		return fmt.Errorf("target epoch %d does not match current epoch %d or prev epoch %d", c.Epoch, currentEpoch, prevEpoch)
+	}
+	return nil
+}
+
+// verifyBeaconBlock verifies beacon head block is known and not from the future.
+func (s *Service) verifyBeaconBlock(ctx context.Context, data *ethpb.AttestationData) error {
+	b, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(data.BeaconBlockRoot))
+	if err != nil {
+		return err
+	}
+	if b == nil || b.Block == nil {
+		return fmt.Errorf("beacon block %#x does not exist", bytesutil.Trunc(data.BeaconBlockRoot))
+	}
+	if b.Block.Slot > data.Slot {
+		return fmt.Errorf("could not process attestation for future block, %d > %d", b.Block.Slot, data.Slot)
+	}
+	return nil
+}
+
+// saveCheckpointState saves and returns the processed state with the associated check point.
+func (s *Service) saveCheckpointState(ctx context.Context, baseState *pb.BeaconState, c *ethpb.Checkpoint) (*pb.BeaconState, error) {
+	ctx, span := trace.StartSpan(ctx, "blockchain.saveCheckpointState")
+	defer span.End()
+
+	s.checkpointStateLock.Lock()
+	defer s.checkpointStateLock.Unlock()
+	cachedState, err := s.checkpointState.StateByCheckpoint(c)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get cached checkpoint state")
+	}
+	if cachedState != nil {
+		return cachedState, nil
+	}
+
+	// Advance slots only when it's higher than current state slot.
+	if helpers.StartSlot(c.Epoch) > baseState.Slot {
+		stateCopy := proto.Clone(baseState).(*pb.BeaconState)
+		stateCopy, err = state.ProcessSlots(ctx, stateCopy, helpers.StartSlot(c.Epoch))
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not process slots up to %d", helpers.StartSlot(c.Epoch))
+		}
+
+		if err := s.checkpointState.AddCheckpointState(&cache.CheckpointState{
+			Checkpoint: c,
+			State:      stateCopy,
+		}); err != nil {
+			return nil, errors.Wrap(err, "could not saved checkpoint state to cache")
+		}
+
+		return stateCopy, nil
+	}
+
+	return baseState, nil
+}
+
+// verifyAttestation validates input attestation is valid.
+func (s *Service) verifyAttestation(ctx context.Context, baseState *pb.BeaconState, a *ethpb.Attestation) (*ethpb.IndexedAttestation, error) {
+	committee, err := helpers.BeaconCommitteeFromState(baseState, a.Data.Slot, a.Data.CommitteeIndex)
+	if err != nil {
+		return nil, err
+	}
+	indexedAtt, err := blocks.ConvertToIndexed(ctx, a, committee)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert attestation to indexed attestation")
+	}
+
+	if err := blocks.VerifyIndexedAttestation(ctx, baseState, indexedAtt); err != nil {
+
+		// TODO(3603): Delete the following signature verify fallback when issue 3603 closes.
+		// When signature fails to verify with committee cache enabled at run time,
+		// the following re-runs the same signature verify routine without cache in play.
+		// This provides extra assurance that committee cache can't break run time.
+		if err == blocks.ErrSigFailedToVerify {
+			committee, err = helpers.BeaconCommitteeWithoutCache(baseState, a.Data.Slot, a.Data.CommitteeIndex)
+			if err != nil {
+				return nil, errors.Wrap(err, "could not convert attestation to indexed attestation without cache")
+			}
+			indexedAtt, err = blocks.ConvertToIndexed(ctx, a, committee)
+			if err != nil {
+				return nil, errors.Wrap(err, "could not convert attestation to indexed attestation")
+			}
+			if err := blocks.VerifyIndexedAttestation(ctx, baseState, indexedAtt); err != nil {
+				return nil, errors.Wrap(err, "could not verify indexed attestation without cache")
+			}
+			sigFailsToVerify.Inc()
+			return indexedAtt, nil
+		}
+
+		return nil, errors.Wrap(err, "could not verify indexed attestation")
+	}
+
+	return indexedAtt, nil
+}