# beacon_chain # Copyright (c) 2018-2020 Status Research & Development GmbH # Licensed and distributed under either of # * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT). # * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0). # at your option. This file may not be copied, modified, or distributed except according to those terms. {.push raises: [Defect].} import tables, algorithm, math, sequtils, options, json_serialization/std/sets, chronicles, ../extras, ../ssz/merkleization, ./crypto, ./datatypes, ./digest, ./helpers, ./signatures, ./validator, ../../nbench/bench_lab # https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/beacon-chain.md#is_valid_merkle_branch func is_valid_merkle_branch*(leaf: Eth2Digest, branch: openarray[Eth2Digest], depth: uint64, index: uint64, root: Eth2Digest): bool {.nbench.}= ## Check if ``leaf`` at ``index`` verifies against the Merkle ``root`` and ## ``branch``. var value = leaf buf: array[64, byte] for i in 0 ..< depth.int: if (index div (1'u64 shl i)) mod 2 != 0: buf[0..31] = branch[i.int].data buf[32..63] = value.data else: buf[0..31] = value.data buf[32..63] = branch[i.int].data value = eth2digest(buf) value == root # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#increase_balance func increase_balance*( state: var BeaconState, index: ValidatorIndex, delta: Gwei) = # Increase the validator balance at index ``index`` by ``delta``. state.balances[index] += delta # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#decrease_balance func decrease_balance*( state: var BeaconState, index: ValidatorIndex, delta: Gwei) = ## Decrease the validator balance at index ``index`` by ``delta``, with ## underflow protection. state.balances[index] = if delta > state.balances[index]: 0'u64 else: state.balances[index] - delta # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#deposits proc process_deposit*( state: var BeaconState, deposit: Deposit, flags: UpdateFlags = {}): bool {.nbench.}= # Process an Eth1 deposit, registering a validator or increasing its balance. # Verify the Merkle branch if not is_valid_merkle_branch( hash_tree_root(deposit.data), deposit.proof, DEPOSIT_CONTRACT_TREE_DEPTH + 1, # Add 1 for the `List` length mix-in state.eth1_deposit_index, state.eth1_data.deposit_root, ): notice "Deposit Merkle validation failed", proof = deposit.proof, deposit_root = state.eth1_data.deposit_root, deposit_index = state.eth1_deposit_index return false # Deposits must be processed in order state.eth1_deposit_index += 1 let pubkey = deposit.data.pubkey amount = deposit.data.amount validator_pubkeys = mapIt(state.validators, it.pubkey) index = validator_pubkeys.find(pubkey) if index == -1: # Verify the deposit signature (proof of possession) which is not checked # by the deposit contract if skipBLSValidation notin flags: if not verify_deposit_signature(deposit.data): # It's ok that deposits fail - they get included in blocks regardless # TODO spec test? debug "Skipping deposit with invalid signature", deposit = shortLog(deposit.data) return true # Add validator and balance entries state.validators.add(Validator( pubkey: pubkey, withdrawal_credentials: deposit.data.withdrawal_credentials, activation_eligibility_epoch: FAR_FUTURE_EPOCH, activation_epoch: FAR_FUTURE_EPOCH, exit_epoch: FAR_FUTURE_EPOCH, withdrawable_epoch: FAR_FUTURE_EPOCH, effective_balance: min(amount - amount mod EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE) )) state.balances.add(amount) else: # Increase balance by deposit amount increase_balance(state, index.ValidatorIndex, amount) true # https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/beacon-chain.md#compute_activation_exit_epoch func compute_activation_exit_epoch(epoch: Epoch): Epoch = ## Return the epoch during which validator activations and exits initiated in ## ``epoch`` take effect. epoch + 1 + MAX_SEED_LOOKAHEAD # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#get_validator_churn_limit func get_validator_churn_limit(state: BeaconState, cache: var StateCache): uint64 = # Return the validator churn limit for the current epoch. max(MIN_PER_EPOCH_CHURN_LIMIT, len(cache.shuffled_active_validator_indices) div CHURN_LIMIT_QUOTIENT).uint64 # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#initiate_validator_exit func initiate_validator_exit*(state: var BeaconState, index: ValidatorIndex, cache: var StateCache) = # Initiate the exit of the validator with index ``index``. # Return if validator already initiated exit let validator = addr state.validators[index] if validator.exit_epoch != FAR_FUTURE_EPOCH: return # Compute exit queue epoch var exit_epochs = mapIt( filterIt(state.validators, it.exit_epoch != FAR_FUTURE_EPOCH), it.exit_epoch) exit_epochs.add compute_activation_exit_epoch(get_current_epoch(state)) var exit_queue_epoch = max(exit_epochs) let exit_queue_churn = foldl( state.validators, a + (if b.exit_epoch == exit_queue_epoch: 1'u64 else: 0'u64), 0'u64) if exit_queue_churn >= get_validator_churn_limit(state, cache): exit_queue_epoch += 1 # Set validator exit epoch and withdrawable epoch validator.exit_epoch = exit_queue_epoch validator.withdrawable_epoch = validator.exit_epoch + MIN_VALIDATOR_WITHDRAWABILITY_DELAY # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#slash_validator proc slash_validator*(state: var BeaconState, slashed_index: ValidatorIndex, cache: var StateCache) = # Slash the validator with index ``index``. let epoch = get_current_epoch(state) initiate_validator_exit(state, slashed_index, cache) let validator = addr state.validators[slashed_index] debug "slash_validator: ejecting validator via slashing (validator_leaving)", index = slashed_index, num_validators = state.validators.len, current_epoch = get_current_epoch(state), validator_slashed = validator.slashed, validator_withdrawable_epoch = validator.withdrawable_epoch, validator_exit_epoch = validator.exit_epoch, validator_effective_balance = validator.effective_balance validator.slashed = true validator.withdrawable_epoch = max(validator.withdrawable_epoch, epoch + EPOCHS_PER_SLASHINGS_VECTOR) state.slashings[int(epoch mod EPOCHS_PER_SLASHINGS_VECTOR)] += validator.effective_balance decrease_balance(state, slashed_index, validator.effective_balance div MIN_SLASHING_PENALTY_QUOTIENT) # The rest doesn't make sense without there being any proposer index, so skip # Apply proposer and whistleblower rewards let proposer_index = get_beacon_proposer_index(state, cache) if proposer_index.isNone: debug "No beacon proposer index and probably no active validators" return let # Spec has whistleblower_index as optional param, but it's never used. whistleblower_index = proposer_index.get whistleblowing_reward = (validator.effective_balance div WHISTLEBLOWER_REWARD_QUOTIENT).Gwei proposer_reward = whistleblowing_reward div PROPOSER_REWARD_QUOTIENT increase_balance(state, proposer_index.get, proposer_reward) # TODO: evaluate if spec bug / underflow can be triggered doAssert(whistleblowing_reward >= proposer_reward, "Spec bug: underflow in slash_validator") increase_balance( state, whistleblower_index, whistleblowing_reward - proposer_reward) # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#genesis proc initialize_beacon_state_from_eth1*( eth1_block_hash: Eth2Digest, eth1_timestamp: uint64, deposits: openArray[Deposit], flags: UpdateFlags = {}): BeaconStateRef {.nbench.}= ## Get the genesis ``BeaconState``. ## ## Before the beacon chain starts, validators will register in the Eth1 chain ## and deposit ETH. When enough many validators have registered, a ## `ChainStart` log will be emitted and the beacon chain can start beaconing. ## ## Because the state root hash is part of the genesis block, the beacon state ## must be calculated before creating the genesis block. # Induct validators # Not in spec: the system doesn't work unless there are at least SLOTS_PER_EPOCH # validators - there needs to be at least one member in each committee - # good to know for testing, though arguably the system is not that useful at # at that point :) doAssert deposits.len >= SLOTS_PER_EPOCH const SECONDS_PER_DAY = uint64(60*60*24) var state = BeaconStateRef( fork: Fork( previous_version: Version(GENESIS_FORK_VERSION), current_version: Version(GENESIS_FORK_VERSION), epoch: GENESIS_EPOCH), genesis_time: eth1_timestamp + 2'u64 * SECONDS_PER_DAY - (eth1_timestamp mod SECONDS_PER_DAY), eth1_data: Eth1Data(block_hash: eth1_block_hash, deposit_count: uint64(len(deposits))), latest_block_header: BeaconBlockHeader( body_root: hash_tree_root(BeaconBlockBody( randao_reveal: ValidatorSig(kind: OpaqueBlob) )) ) ) # Seed RANDAO with Eth1 entropy state.randao_mixes.fill(eth1_block_hash) # Process deposits let leaves = deposits.mapIt(it.data) var i = 0 for prefix_root in hash_tree_roots_prefix( leaves, 2'i64^DEPOSIT_CONTRACT_TREE_DEPTH): state.eth1_data.deposit_root = prefix_root discard process_deposit(state[], deposits[i], flags) i += 1 # Process activations for validator_index in 0 ..< state.validators.len: let balance = state.balances[validator_index] validator = addr state.validators[validator_index] validator.effective_balance = min( balance - balance mod EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE) if validator.effective_balance == MAX_EFFECTIVE_BALANCE: validator.activation_eligibility_epoch = GENESIS_EPOCH validator.activation_epoch = GENESIS_EPOCH # Set genesis validators root for domain separation and chain versioning state.genesis_validators_root = hash_tree_root(state.validators) state proc initialize_hashed_beacon_state_from_eth1*( eth1_block_hash: Eth2Digest, eth1_timestamp: uint64, deposits: openArray[Deposit], flags: UpdateFlags = {}): HashedBeaconState = let genesisState = initialize_beacon_state_from_eth1( eth1_block_hash, eth1_timestamp, deposits, flags) HashedBeaconState(data: genesisState[], root: hash_tree_root(genesisState[])) func is_valid_genesis_state*(state: BeaconState): bool = if state.genesis_time < MIN_GENESIS_TIME: return false # This is an okay get_active_validator_indices(...) for the time being. if len(get_active_validator_indices(state, GENESIS_EPOCH)) < MIN_GENESIS_ACTIVE_VALIDATOR_COUNT: return false return true # TODO this is now a non-spec helper function, and it's not really accurate # so only usable/used in research/ and tests/ func get_initial_beacon_block*(state: BeaconState): SignedBeaconBlock = SignedBeaconBlock( message: BeaconBlock( slot: GENESIS_SLOT, state_root: hash_tree_root(state), body: BeaconBlockBody( # TODO: This shouldn't be necessary if OpaqueBlob is the default randao_reveal: ValidatorSig(kind: OpaqueBlob)))) # parent_root, randao_reveal, eth1_data, signature, and body automatically # initialized to default values. # https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/beacon-chain.md#get_block_root_at_slot func get_block_root_at_slot*(state: BeaconState, slot: Slot): Eth2Digest = # Return the block root at a recent ``slot``. doAssert state.slot <= slot + SLOTS_PER_HISTORICAL_ROOT doAssert slot < state.slot state.block_roots[slot mod SLOTS_PER_HISTORICAL_ROOT] # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#get_block_root func get_block_root*(state: BeaconState, epoch: Epoch): Eth2Digest = # Return the block root at the start of a recent ``epoch``. get_block_root_at_slot(state, compute_start_slot_at_epoch(epoch)) # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#get_total_balance func get_total_balance*(state: BeaconState, validators: auto): Gwei = ## Return the combined effective balance of the ``indices``. ## ``EFFECTIVE_BALANCE_INCREMENT`` Gwei minimum to avoid divisions by zero. ## Math safe up to ~10B ETH, afterwhich this overflows uint64. max(EFFECTIVE_BALANCE_INCREMENT, foldl(validators, a + state.validators[b].effective_balance, 0'u64) ) # XXX: Move to state_transition_epoch.nim? # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#is_eligible_for_activation_queue func is_eligible_for_activation_queue(validator: Validator): bool = # Check if ``validator`` is eligible to be placed into the activation queue. validator.activation_eligibility_epoch == FAR_FUTURE_EPOCH and validator.effective_balance == MAX_EFFECTIVE_BALANCE # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#is_eligible_for_activation func is_eligible_for_activation(state: BeaconState, validator: Validator): bool = # Check if ``validator`` is eligible for activation. # Placement in queue is finalized validator.activation_eligibility_epoch <= state.finalized_checkpoint.epoch and # Has not yet been activated validator.activation_epoch == FAR_FUTURE_EPOCH # https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/beacon-chain.md#registry-updates proc process_registry_updates*(state: var BeaconState, cache: var StateCache) {.nbench.}= ## Process activation eligibility and ejections ## Try to avoid caching here, since this could easily become undefined # Make visible, e.g., # https://github.com/status-im/nim-beacon-chain/pull/608 # https://github.com/sigp/lighthouse/pull/657 let epoch {.used.} = get_current_epoch(state) trace "process_registry_updates validator balances", balances=state.balances, active_validator_indices=get_active_validator_indices(state, epoch), epoch=epoch # is_active_validator(...) is activation_epoch <= epoch < exit_epoch, # and changes here to either activation_epoch or exit_epoch only take # effect with a compute_activation_exit_epoch(...) delay of, based on # the current epoch, 1 + MAX_SEED_LOOKAHEAD epochs ahead. Thus caches # remain valid for this epoch through though this function along with # the rest of the epoch transition. for index, validator in state.validators: if is_eligible_for_activation_queue(validator): state.validators[index].activation_eligibility_epoch = get_current_epoch(state) + 1 if is_active_validator(validator, get_current_epoch(state)) and validator.effective_balance <= EJECTION_BALANCE: debug "Registry updating: ejecting validator due to low balance (validator_leaving)", index = index, num_validators = state.validators.len, current_epoch = get_current_epoch(state), validator_slashed = validator.slashed, validator_withdrawable_epoch = validator.withdrawable_epoch, validator_exit_epoch = validator.exit_epoch, validator_effective_balance = validator.effective_balance initiate_validator_exit(state, index.ValidatorIndex, cache) ## Queue validators eligible for activation and not dequeued for activation var activation_queue : seq[tuple[a: Epoch, b: int]] = @[] for index, validator in state.validators: if is_eligible_for_activation(state, validator): activation_queue.add ( state.validators[index].activation_eligibility_epoch, index) activation_queue.sort(system.cmp) ## Dequeued validators for activation up to churn limit (without resetting ## activation epoch) let churn_limit = get_validator_churn_limit(state, cache) for i, epoch_and_index in activation_queue: if i.uint64 >= churn_limit: break let (_, index) = epoch_and_index validator = addr state.validators[index] validator.activation_epoch = compute_activation_exit_epoch(get_current_epoch(state)) # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#is_valid_indexed_attestation proc is_valid_indexed_attestation*( state: BeaconState, indexed_attestation: IndexedAttestation, flags: UpdateFlags): bool = # Check if ``indexed_attestation`` has sorted and unique indices and a valid # aggregate signature. # TODO: this is noSideEffect besides logging # https://github.com/status-im/nim-chronicles/issues/62 # Verify indices are sorted and unique # TODO: A simple loop can verify that the indicates are monotonically # increasing and non-repeating here! let indices = indexed_attestation.attesting_indices if indices.asSeq != sorted(toHashSet(indices.asSeq).toSeq, system.cmp): notice "indexed attestation: indices not sorted" return false # Verify aggregate signature if skipBLSValidation notin flags: # TODO: fuse loops with blsFastAggregateVerify let pubkeys = mapIt(indices, state.validators[it.int].pubkey) if not verify_attestation_signature( state.fork, state.genesis_validators_root, indexed_attestation.data, pubkeys, indexed_attestation.signature): notice "indexed attestation: signature verification failure" return false true # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#get_attesting_indices func get_attesting_indices*(state: BeaconState, data: AttestationData, bits: CommitteeValidatorsBits, stateCache: var StateCache): HashSet[ValidatorIndex] = # Return the set of attesting indices corresponding to ``data`` and ``bits``. result = initHashSet[ValidatorIndex]() let committee = get_beacon_committee( state, data.slot, data.index.CommitteeIndex, stateCache) # This shouldn't happen if one begins with a valid BeaconState and applies # valid updates, but one can construct a BeaconState where it does. Do not # do anything here since the PendingAttestation wouldn't have made it past # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#attestations # which checks len(attestation.aggregation_bits) == len(committee) that in # nim-beacon-chain lives in check_attestation(...). # Addresses https://github.com/status-im/nim-beacon-chain/issues/922 if bits.len != committee.len: trace "get_attesting_indices: inconsistent aggregation and committee length" return for i, index in committee: if bits[i]: result.incl index # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#get_indexed_attestation func get_indexed_attestation*(state: BeaconState, attestation: Attestation, stateCache: var StateCache): IndexedAttestation = # Return the indexed attestation corresponding to ``attestation``. let attesting_indices = get_attesting_indices( state, attestation.data, attestation.aggregation_bits, stateCache) IndexedAttestation( attesting_indices: List[uint64, MAX_VALIDATORS_PER_COMMITTEE].init( sorted(mapIt(attesting_indices.toSeq, it.uint64), system.cmp)), data: attestation.data, signature: attestation.signature ) # Attestation validation # ------------------------------------------------------------------------------------------ # https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#attestations # # TODO: Refactor, we need: # - cheap validations that do not involve the fork state (to avoid unnecessary and costly rewinding which are probably a DOS vector) # - check that must be done on the targeted state (for example beacon committee consistency) # - check that requires easily computed data from the targeted sate (slots, epoch, justified checkpoints) proc isValidAttestationSlot*(attestationSlot, stateSlot: Slot): bool = ## Attestation check that does not depend on the whole block state ## for cheaper prefiltering of attestations that come from the network ## to limit DOS via state rewinding if not (attestationSlot + MIN_ATTESTATION_INCLUSION_DELAY <= stateSlot): warn("Attestation too new", attestation_slot = shortLog(attestationSlot), state_slot = shortLog(stateSlot)) return false if not (stateSlot <= attestationSlot + SLOTS_PER_EPOCH): warn("Attestation too old", attestation_slot = shortLog(attestationSlot), state_slot = shortLog(stateSlot)) return false return true # TODO remove/merge with p2p-interface validation proc isValidAttestationTargetEpoch*( state: BeaconState, attestation: Attestation): bool = # TODO what constitutes a valid attestation when it's about to be added to # the pool? we're interested in attestations that will become viable # for inclusion in blocks in the future and on any fork, so we need to # consider that validations might happen using the state of a different # fork. # Some things are always invalid (like out-of-bounds issues etc), but # others are more subtle - how do we validate the signature for example? # It might be valid on one fork but not another. One thing that helps # is that committees are stable per epoch and that it should be OK to # include an attestation in a block even if the corresponding validator # was slashed in the same epoch - there's no penalty for doing this and # the vote counting logic will take care of any ill effects (TODO verify) let data = attestation.data # TODO re-enable check #if not (data.crosslink.shard < SHARD_COUNT): # notice "Attestation shard too high", # attestation_shard = data.crosslink.shard # return # Without this check, we can't get a slot number for the attestation as # certain helpers will assert # TODO this could probably be avoided by being smart about the specific state # used to validate the attestation: most likely if we pick the state of # the beacon block being voted for and a slot in the target epoch # of the attestation, we'll be safe! # TODO the above state selection logic should probably live here in the # attestation pool if not (data.target.epoch == get_previous_epoch(state) or data.target.epoch == get_current_epoch(state)): warn("Target epoch not current or previous epoch") return if not (data.target.epoch == compute_epoch_at_slot(data.slot)): warn("Target epoch inconsistent with epoch of data slot", target_epoch = data.target.epoch, data_slot_epoch = compute_epoch_at_slot(data.slot)) return true # https://github.com/ethereum/eth2.0-specs/blob/v0.11.2/specs/phase0/beacon-chain.md#attestations proc check_attestation*( state: BeaconState, attestation: Attestation, flags: UpdateFlags, stateCache: var StateCache): bool = ## Check that an attestation follows the rules of being included in the state ## at the current slot. When acting as a proposer, the same rules need to ## be followed! # TODO: When checking attestation from the network, currently rewinding/advancing # a temporary state is needed. # If this is too costly we can be DOS-ed. # We might want to split this into "state-dependent" checks and "state-independent" checks # The latter one should be made prior to state-rewinding. let stateSlot = state.slot data = attestation.data trace "process_attestation: beginning", attestation=attestation if not (data.index < get_committee_count_at_slot(state, data.slot)): warn("Data index exceeds committee count", data_index = data.index, committee_count = get_committee_count_at_slot(state, data.slot)) return if not isValidAttestationTargetEpoch(state, attestation): # Logging in isValidAttestationTargetEpoch return if not isValidAttestationSlot(data.slot, stateSlot): # Logging in isValidAttestationSlot return let committee = get_beacon_committee( state, data.slot, data.index.CommitteeIndex, stateCache) if attestation.aggregation_bits.len != committee.len: warn("Inconsistent aggregation and committee length", aggregation_bits_len = attestation.aggregation_bits.len, committee_len = committee.len ) return let ffg_check_data = (data.source.epoch, data.source.root, data.target.epoch) if data.target.epoch == get_current_epoch(state): if not (ffg_check_data == (state.current_justified_checkpoint.epoch, state.current_justified_checkpoint.root, get_current_epoch(state))): warn("FFG data not matching current justified epoch") return else: if not (ffg_check_data == (state.previous_justified_checkpoint.epoch, state.previous_justified_checkpoint.root, get_previous_epoch(state))): warn("FFG data not matching previous justified epoch") return if not is_valid_indexed_attestation( state, get_indexed_attestation(state, attestation, stateCache), flags): warn("process_attestation: signature or bitfields incorrect") return true proc process_attestation*( state: var BeaconState, attestation: Attestation, flags: UpdateFlags, stateCache: var StateCache): bool {.nbench.}= # In the spec, attestation validation is mixed with state mutation, so here # we've split it into two functions so that the validation logic can be # reused when looking for suitable blocks to include in attestations. # TODO don't log warnings when looking for attestations (return # Result[void, cstring] instead of logging in check_attestation?) let proposer_index = get_beacon_proposer_index(state, stateCache) if proposer_index.isNone: debug "No beacon proposer index and probably no active validators" return false if check_attestation(state, attestation, flags, stateCache): let attestation_slot = attestation.data.slot pending_attestation = PendingAttestation( data: attestation.data, aggregation_bits: attestation.aggregation_bits, inclusion_delay: state.slot - attestation_slot, proposer_index: proposer_index.get.uint64, ) if attestation.data.target.epoch == get_current_epoch(state): trace "process_attestation: current_epoch_attestations.add", attestation = shortLog(attestation), pending_attestation = pending_attestation, indices = get_attesting_indices( state, attestation.data, attestation.aggregation_bits, stateCache).len state.current_epoch_attestations.add(pending_attestation) else: trace "process_attestation: previous_epoch_attestations.add", attestation = shortLog(attestation), pending_attestation = pending_attestation, indices = get_attesting_indices( state, attestation.data, attestation.aggregation_bits, stateCache).len state.previous_epoch_attestations.add(pending_attestation) true else: trace "process_attestation: check_attestation failed", attestation = shortLog(attestation), indices = get_attesting_indices( state, attestation.data, attestation.aggregation_bits, stateCache).len false func makeAttestationData*( state: BeaconState, slot: Slot, committee_index: uint64, beacon_block_root: Eth2Digest): AttestationData = ## Create an attestation / vote for the block `beacon_block_root` using the ## data in `state` to fill in the rest of the fields. ## `state` is the state corresponding to the `beacon_block_root` advanced to ## the slot we're attesting to. let current_epoch = get_current_epoch(state) start_slot = compute_start_slot_at_epoch(current_epoch) epoch_boundary_block_root = if start_slot == state.slot: beacon_block_root else: get_block_root_at_slot(state, start_slot) doAssert slot.compute_epoch_at_slot == current_epoch # https://github.com/ethereum/eth2.0-specs/blob/v0.11.2/specs/phase0/validator.md#attestation-data AttestationData( slot: slot, index: committee_index, beacon_block_root: beacon_block_root, source: state.current_justified_checkpoint, target: Checkpoint( epoch: current_epoch, root: epoch_boundary_block_root ) )