prysm-pulse/beacon-chain/blockchain/process_attestation.go
2021-07-21 21:34:07 +00:00

104 lines
4.2 KiB
Go

package blockchain
import (
"context"
"github.com/pkg/errors"
"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
"github.com/prysmaticlabs/prysm/shared/attestationutil"
"github.com/prysmaticlabs/prysm/shared/bytesutil"
"github.com/prysmaticlabs/prysm/shared/copyutil"
"github.com/prysmaticlabs/prysm/shared/params"
"github.com/prysmaticlabs/prysm/shared/timeutils"
"go.opencensus.io/trace"
)
// onAttestation is called whenever an attestation is received, verifies the attestation is valid and saves
// it to the DB. As a stateless function, this does not hold nor delay attestation based on the spec descriptions.
// The delay is handled by the caller in `processAttestations`.
//
// Spec pseudocode definition:
// def on_attestation(store: Store, 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.
// """
// validate_on_attestation(store, attestation)
// store_target_checkpoint_state(store, attestation.data.target)
//
// # Get state at the `target` to fully validate attestation
// target_state = store.checkpoint_states[attestation.data.target]
// indexed_attestation = get_indexed_attestation(target_state, attestation)
// assert is_valid_indexed_attestation(target_state, indexed_attestation)
//
// # Update latest messages for attesting indices
// update_latest_messages(store, indexed_attestation.attesting_indices, attestation)
func (s *Service) onAttestation(ctx context.Context, a *ethpb.Attestation) error {
ctx, span := trace.StartSpan(ctx, "blockChain.onAttestation")
defer span.End()
if err := helpers.ValidateNilAttestation(a); err != nil {
return err
}
if err := helpers.ValidateSlotTargetEpoch(a.Data); err != nil {
return err
}
tgt := copyutil.CopyCheckpoint(a.Data.Target)
// Note that target root check is ignored here because it was performed in sync's validation pipeline:
// validate_aggregate_proof.go and validate_beacon_attestation.go
// If missing target root were to fail in this method, it would have just failed in `getAttPreState`.
// Retrieve attestation's data beacon block pre state. Advance pre state to latest epoch if necessary and
// save it to the cache.
baseState, err := s.getAttPreState(ctx, tgt)
if err != nil {
return err
}
genesisTime := baseState.GenesisTime()
// Verify attestation target is from current epoch or previous epoch.
if err := s.verifyAttTargetEpoch(ctx, genesisTime, uint64(timeutils.Now().Unix()), tgt); err != nil {
return err
}
// Verify attestation beacon block is known and not from the future.
if err := s.verifyBeaconBlock(ctx, a.Data); err != nil {
return errors.Wrap(err, "could not verify attestation beacon block")
}
// Note that LMG GHOST and FFG consistency check is ignored because it was performed in sync's validation pipeline:
// validate_aggregate_proof.go and validate_beacon_attestation.go
// Verify attestations can only affect the fork choice of subsequent slots.
if err := helpers.VerifySlotTime(genesisTime, a.Data.Slot+1, params.BeaconNetworkConfig().MaximumGossipClockDisparity); err != nil {
return err
}
// Use the target state to verify attesting indices are valid.
committee, err := helpers.BeaconCommitteeFromState(baseState, a.Data.Slot, a.Data.CommitteeIndex)
if err != nil {
return err
}
indexedAtt, err := attestationutil.ConvertToIndexed(ctx, a, committee)
if err != nil {
return err
}
if err := attestationutil.IsValidAttestationIndices(ctx, indexedAtt); err != nil {
return err
}
// Note that signature verification is ignored here because it was performed in sync's validation pipeline:
// validate_aggregate_proof.go and validate_beacon_attestation.go
// We assume trusted attestation in this function has verified signature.
// Update forkchoice store with the new attestation for updating weight.
s.cfg.ForkChoiceStore.ProcessAttestation(ctx, indexedAtt.AttestingIndices, bytesutil.ToBytes32(a.Data.BeaconBlockRoot), a.Data.Target.Epoch)
return nil
}