# beacon_chain # Copyright (c) 2018-2022 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. # State transition - block processing, as described in # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#block-processing # # The entry point is `process_block` which is at the bottom of this file. # # General notes about the code: # * Weird styling - the sections taken from the spec use python styling while # the others use NEP-1 - helps grepping identifiers in spec # * When updating the code, add TODO sections to mark where there are clear # improvements to be made - other than that, keep things similar to spec unless # motivated by security or performance considerations {.push raises: [Defect].} import std/[algorithm, options, sequtils, sets, tables], chronicles, metrics, ../extras, ./datatypes/[phase0, altair, bellatrix], "."/[beaconstate, eth2_merkleization, helpers, validator, signatures] export extras, phase0, altair # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#block-header func process_block_header*( state: var ForkyBeaconState, blck: SomeForkyBeaconBlock, flags: UpdateFlags, cache: var StateCache): Result[void, cstring] = # Verify that the slots match if not (blck.slot == state.slot): return err("process_block_header: slot mismatch") # Verify that the block is newer than latest block header if not (blck.slot > state.latest_block_header.slot): return err("process_block_header: block not newer than latest block header") # Verify that proposer index is the correct index let proposer_index = get_beacon_proposer_index(state, cache) if proposer_index.isNone: return err("process_block_header: proposer missing") if not (blck.proposer_index.ValidatorIndex == proposer_index.get): return err("process_block_header: proposer index incorrect") # Verify that the parent matches if not (blck.parent_root == hash_tree_root(state.latest_block_header)): return err("process_block_header: previous block root mismatch") # Verify proposer is not slashed if state.validators.asSeq()[blck.proposer_index].slashed: return err("process_block_header: proposer slashed") # Cache current block as the new latest block state.latest_block_header = BeaconBlockHeader( slot: blck.slot, proposer_index: blck.proposer_index, parent_root: blck.parent_root, # state_root: zeroed, overwritten in the next `process_slot` call body_root: hash_tree_root(blck.body), ) ok() func `xor`[T: array](a, b: T): T = for i in 0.. SLOTS_PER_ETH1_VOTING_PERIOD: state.eth1_data = body.eth1_data ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#is_slashable_validator func is_slashable_validator(validator: Validator, epoch: Epoch): bool = # Check if ``validator`` is slashable. (not validator.slashed) and (validator.activation_epoch <= epoch) and (epoch < validator.withdrawable_epoch) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#proposer-slashings proc check_proposer_slashing*( state: ForkyBeaconState, proposer_slashing: SomeProposerSlashing, flags: UpdateFlags): Result[void, cstring] = let header_1 = proposer_slashing.signed_header_1.message header_2 = proposer_slashing.signed_header_2.message # Not from spec if header_1.proposer_index >= state.validators.lenu64: return err("check_proposer_slashing: invalid proposer index") # Verify header slots match if not (header_1.slot == header_2.slot): return err("check_proposer_slashing: slot mismatch") # Verify header proposer indices match if not (header_1.proposer_index == header_2.proposer_index): return err("check_proposer_slashing: proposer indices mismatch") # Verify the headers are different if not (header_1 != header_2): return err("check_proposer_slashing: headers not different") # Verify the proposer is slashable let proposer = unsafeAddr state.validators.asSeq()[header_1.proposer_index] if not is_slashable_validator(proposer[], get_current_epoch(state)): return err("check_proposer_slashing: slashed proposer") # Verify signatures if skipBlsValidation notin flags: for signed_header in [proposer_slashing.signed_header_1, proposer_slashing.signed_header_2]: if not verify_block_signature( state.fork, state.genesis_validators_root, signed_header.message.slot, signed_header.message, proposer[].pubkey, signed_header.signature): return err("check_proposer_slashing: invalid signature") ok() proc check_proposer_slashing*( state: var ForkedHashedBeaconState; proposer_slashing: SomeProposerSlashing; flags: UpdateFlags): Result[void, cstring] = withState(state): check_proposer_slashing(state.data, proposer_slashing, flags) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#proposer-slashings proc process_proposer_slashing*( cfg: RuntimeConfig, state: var ForkyBeaconState, proposer_slashing: SomeProposerSlashing, flags: UpdateFlags, cache: var StateCache): Result[void, cstring] = ? check_proposer_slashing(state, proposer_slashing, flags) slash_validator( cfg, state, proposer_slashing.signed_header_1.message.proposer_index.ValidatorIndex, cache) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#is_slashable_attestation_data func is_slashable_attestation_data( data_1: AttestationData, data_2: AttestationData): bool = ## Check if ``data_1`` and ``data_2`` are slashable according to Casper FFG ## rules. # Double vote (data_1 != data_2 and data_1.target.epoch == data_2.target.epoch) or # Surround vote (data_1.source.epoch < data_2.source.epoch and data_2.target.epoch < data_1.target.epoch) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#attester-slashings proc check_attester_slashing*( state: ForkyBeaconState, attester_slashing: SomeAttesterSlashing, flags: UpdateFlags ): Result[seq[ValidatorIndex], cstring] = let attestation_1 = attester_slashing.attestation_1 attestation_2 = attester_slashing.attestation_2 if not is_slashable_attestation_data( attestation_1.data, attestation_2.data): return err("Attester slashing: surround or double vote check failed") if not is_valid_indexed_attestation(state, attestation_1, flags).isOk(): return err("Attester slashing: invalid attestation 1") if not is_valid_indexed_attestation(state, attestation_2, flags).isOk(): return err("Attester slashing: invalid attestation 2") var slashed_indices: seq[ValidatorIndex] let attesting_indices_2 = toHashSet(attestation_2.attesting_indices.asSeq) for index in sorted(filterIt( attestation_1.attesting_indices.asSeq, it in attesting_indices_2), system.cmp): if is_slashable_validator( state.validators.asSeq()[index], get_current_epoch(state)): slashed_indices.add index.ValidatorIndex if slashed_indices.len == 0: return err("Attester slashing: Trying to slash participant(s) twice") ok slashed_indices proc check_attester_slashing*( state: var ForkedHashedBeaconState; attester_slashing: SomeAttesterSlashing; flags: UpdateFlags): Result[seq[ValidatorIndex], cstring] = withState(state): check_attester_slashing(state.data, attester_slashing, flags) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#attester-slashings proc process_attester_slashing*( cfg: RuntimeConfig, state: var ForkyBeaconState, attester_slashing: SomeAttesterSlashing, flags: UpdateFlags, cache: var StateCache ): Result[void, cstring] = let attester_slashing_validity = check_attester_slashing(state, attester_slashing, flags) if attester_slashing_validity.isErr: return err(attester_slashing_validity.error) for index in attester_slashing_validity.value: slash_validator(cfg, state, index, cache) ok() func findValidatorIndex*(state: ForkyBeaconState, pubkey: ValidatorPubKey): int = # This linear scan is unfortunate, but should be fairly fast as we do a simple # byte comparison of the key. The alternative would be to build a Table, but # given that each block can hold no more than 16 deposits, it's slower to # build the table and use it for lookups than to scan it like this. # Once we have a reusable, long-lived cache, this should be revisited for i in 0 ..< state.validators.len: if state.validators.asSeq[i].pubkey == pubkey: return i -1 proc process_deposit*(cfg: RuntimeConfig, state: var ForkyBeaconState, deposit: Deposit, flags: UpdateFlags): Result[void, cstring] = ## 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, ): return err("process_deposit: deposit Merkle validation failed") # Deposits must be processed in order state.eth1_deposit_index += 1 let pubkey = deposit.data.pubkey amount = deposit.data.amount index = findValidatorIndex(state, pubkey) if index != -1: # Increase balance by deposit amount increase_balance(state, index.ValidatorIndex, amount) else: # Verify the deposit signature (proof of possession) which is not checked # by the deposit contract if verify_deposit_signature(cfg, deposit.data): # New validator! Add validator and balance entries if not state.validators.add(get_validator_from_deposit(deposit.data)): return err("process_deposit: too many validators") if not state.balances.add(amount): static: doAssert state.balances.maxLen == state.validators.maxLen raiseAssert "adding validator succeeded, so should balances" when state is altair.BeaconState or state is bellatrix.BeaconState: if not state.previous_epoch_participation.add(ParticipationFlags(0)): return err("process_deposit: too many validators (previous_epoch_participation)") if not state.current_epoch_participation.add(ParticipationFlags(0)): return err("process_deposit: too many validators (current_epoch_participation)") if not state.inactivity_scores.add(0'u64): return err("process_deposit: too many validators (inactivity_scores)") doAssert state.validators.len == state.balances.len else: # Deposits may come with invalid signatures - in that case, they are not # turned into a validator but still get processed to keep the deposit # index correct trace "Skipping deposit with invalid signature", deposit = shortLog(deposit.data) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#voluntary-exits proc check_voluntary_exit*( cfg: RuntimeConfig, state: ForkyBeaconState, signed_voluntary_exit: SomeSignedVoluntaryExit, flags: UpdateFlags): Result[void, cstring] = let voluntary_exit = signed_voluntary_exit.message # Not in spec. Check that validator_index is in range if voluntary_exit.validator_index >= state.validators.lenu64: return err("Exit: invalid validator index") let validator = unsafeAddr state.validators.asSeq()[voluntary_exit.validator_index] # Verify the validator is active if not is_active_validator(validator[], get_current_epoch(state)): return err("Exit: validator not active") # Verify exit has not been initiated if validator[].exit_epoch != FAR_FUTURE_EPOCH: return err("Exit: validator has exited") # Exits must specify an epoch when they become valid; they are not valid # before then if not (get_current_epoch(state) >= voluntary_exit.epoch): return err("Exit: exit epoch not passed") # Verify the validator has been active long enough if not (get_current_epoch(state) >= validator[].activation_epoch + cfg.SHARD_COMMITTEE_PERIOD): return err("Exit: not in validator set long enough") # Verify signature if skipBlsValidation notin flags: if not verify_voluntary_exit_signature( state.fork, state.genesis_validators_root, voluntary_exit, validator[].pubkey, signed_voluntary_exit.signature): return err("Exit: invalid signature") # Initiate exit debug "Exit: checking voluntary exit (validator_leaving)", index = voluntary_exit.validator_index, num_validators = state.validators.len, epoch = voluntary_exit.epoch, 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 ok() proc check_voluntary_exit*( cfg: RuntimeConfig, state: ForkedHashedBeaconState; signed_voluntary_exit: SomeSignedVoluntaryExit; flags: UpdateFlags): Result[void, cstring] = withState(state): check_voluntary_exit(cfg, state.data, signed_voluntary_exit, flags) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#voluntary-exits proc process_voluntary_exit*( cfg: RuntimeConfig, state: var ForkyBeaconState, signed_voluntary_exit: SomeSignedVoluntaryExit, flags: UpdateFlags, cache: var StateCache): Result[void, cstring] = ? check_voluntary_exit(cfg, state, signed_voluntary_exit, flags) initiate_validator_exit( cfg, state, signed_voluntary_exit.message.validator_index.ValidatorIndex, cache) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#operations proc process_operations(cfg: RuntimeConfig, state: var ForkyBeaconState, body: SomeForkyBeaconBlockBody, base_reward_per_increment: Gwei, flags: UpdateFlags, cache: var StateCache): Result[void, cstring] = # Verify that outstanding deposits are processed up to the maximum number of # deposits let req_deposits = min(MAX_DEPOSITS, state.eth1_data.deposit_count - state.eth1_deposit_index) if state.eth1_data.deposit_count < state.eth1_deposit_index or body.deposits.lenu64 != req_deposits: return err("incorrect number of deposits") for op in body.proposer_slashings: ? process_proposer_slashing(cfg, state, op, flags, cache) for op in body.attester_slashings: ? process_attester_slashing(cfg, state, op, flags, cache) for op in body.attestations: ? process_attestation(state, op, flags, base_reward_per_increment, cache) for op in body.deposits: ? process_deposit(cfg, state, op, flags) for op in body.voluntary_exits: ? process_voluntary_exit(cfg, state, op, flags, cache) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/altair/beacon-chain.md#sync-committee-processing func get_participant_reward*(total_active_balance: Gwei): Gwei = let total_active_increments = total_active_balance div EFFECTIVE_BALANCE_INCREMENT total_base_rewards = get_base_reward_per_increment(total_active_balance) * total_active_increments max_participant_rewards = total_base_rewards * SYNC_REWARD_WEIGHT div WEIGHT_DENOMINATOR div SLOTS_PER_EPOCH max_participant_rewards div SYNC_COMMITTEE_SIZE # https://github.com/ethereum/consensus-specs/blob/v1.1.0-alpha.6/specs/altair/beacon-chain.md#sync-committee-processing func get_proposer_reward*(participant_reward: Gwei): Gwei = participant_reward * PROPOSER_WEIGHT div (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/altair/beacon-chain.md#sync-committee-processing proc process_sync_aggregate*( state: var (altair.BeaconState | bellatrix.BeaconState), sync_aggregate: SomeSyncAggregate, total_active_balance: Gwei, cache: var StateCache): Result[void, cstring] = # Verify sync committee aggregate signature signing over the previous slot # block root when sync_aggregate.sync_committee_signature isnot TrustedSig: var participant_pubkeys: seq[ValidatorPubKey] for i in 0 ..< state.current_sync_committee.pubkeys.len: if sync_aggregate.sync_committee_bits[i]: participant_pubkeys.add state.current_sync_committee.pubkeys[i] # p2p-interface message validators check for empty sync committees, so it # shouldn't run except as part of test suite. if participant_pubkeys.len == 0: if sync_aggregate.sync_committee_signature != ValidatorSig.infinity(): return err("process_sync_aggregate: empty sync aggregates need signature of point at infinity") else: # Empty participants allowed let previous_slot = max(state.slot, Slot(1)) - 1 beacon_block_root = get_block_root_at_slot(state, previous_slot) if not verify_sync_committee_signature( state.fork, state.genesis_validators_root, previous_slot, beacon_block_root, participant_pubkeys, sync_aggregate.sync_committee_signature): return err("process_sync_aggregate: invalid signature") # Compute participant and proposer rewards let participant_reward = get_participant_reward(total_active_balance) proposer_reward = state_transition_block.get_proposer_reward(participant_reward) proposer_index = get_beacon_proposer_index(state, cache) if proposer_index.isNone: # We're processing a block, so this can't happen, in theory (!) return err("process_sync_aggregate: no proposer") # Apply participant and proposer rewards let indices = get_sync_committee_cache(state, cache).current_sync_committee # TODO could use a sequtils2 zipIt for i in 0 ..< min( state.current_sync_committee.pubkeys.len, sync_aggregate.sync_committee_bits.len): let participant_index = indices[i] if sync_aggregate.sync_committee_bits[i]: increase_balance(state, participant_index, participant_reward) increase_balance(state, proposer_index.get, proposer_reward) else: decrease_balance(state, participant_index, participant_reward) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/bellatrix/beacon-chain.md#process_execution_payload proc process_execution_payload*( state: var bellatrix.BeaconState, payload: ExecutionPayload, notify_new_payload: ExecutePayload): Result[void, cstring] = ## Verify consistency of the parent hash with respect to the previous ## execution payload header if is_merge_transition_complete(state): if not (payload.parent_hash == state.latest_execution_payload_header.block_hash): return err("process_execution_payload: payload and state parent hash mismatch") # Verify prev_randao if not (payload.prev_randao == get_randao_mix(state, get_current_epoch(state))): return err("process_execution_payload: payload and state randomness mismatch") # Verify timestamp if not (payload.timestamp == compute_timestamp_at_slot(state, state.slot)): return err("process_execution_payload: invalid timestamp") # Verify the execution payload is valid if not notify_new_payload(payload): return err("process_execution_payload: execution payload invalid") # Cache execution payload header state.latest_execution_payload_header = ExecutionPayloadHeader( parent_hash: payload.parent_hash, fee_recipient: payload.fee_recipient, state_root: payload.state_root, receipts_root: payload.receipts_root, logs_bloom: payload.logs_bloom, prev_randao: payload.prev_randao, block_number: payload.block_number, gas_limit: payload.gas_limit, gas_used: payload.gas_used, timestamp: payload.timestamp, base_fee_per_gas: payload.base_fee_per_gas, block_hash: payload.block_hash, extra_data: payload.extra_data, transactions_root: hash_tree_root(payload.transactions)) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/beacon-chain.md#block-processing # TODO workaround for https://github.com/nim-lang/Nim/issues/18095 # copy of datatypes/phase0.nim type SomePhase0Block = phase0.BeaconBlock | phase0.SigVerifiedBeaconBlock | phase0.TrustedBeaconBlock proc process_block*( cfg: RuntimeConfig, state: var phase0.BeaconState, blck: SomePhase0Block, flags: UpdateFlags, cache: var StateCache): Result[void, cstring]= ## When there's a new block, we need to verify that the block is sane and ## update the state accordingly - the state is left in an unknown state when ## block application fails (!) ? process_block_header(state, blck, flags, cache) ? process_randao(state, blck.body, flags, cache) ? process_eth1_data(state, blck.body) ? process_operations(cfg, state, blck.body, 0.Gwei, flags, cache) ok() # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/altair/beacon-chain.md#block-processing # TODO workaround for https://github.com/nim-lang/Nim/issues/18095 # copy of datatypes/altair.nim type SomeAltairBlock = altair.BeaconBlock | altair.SigVerifiedBeaconBlock | altair.TrustedBeaconBlock proc process_block*( cfg: RuntimeConfig, state: var altair.BeaconState, blck: SomeAltairBlock, flags: UpdateFlags, cache: var StateCache): Result[void, cstring]= ## When there's a new block, we need to verify that the block is sane and ## update the state accordingly - the state is left in an unknown state when ## block application fails (!) ? process_block_header(state, blck, flags, cache) ? process_randao(state, blck.body, flags, cache) ? process_eth1_data(state, blck.body) let total_active_balance = get_total_active_balance(state, cache) base_reward_per_increment = get_base_reward_per_increment(total_active_balance) ? process_operations( cfg, state, blck.body, base_reward_per_increment, flags, cache) ? process_sync_aggregate( state, blck.body.sync_aggregate, total_active_balance, cache) # [New in Altair] ok() # TODO workaround for https://github.com/nim-lang/Nim/issues/18095 type SomeBellatrixBlock = bellatrix.BeaconBlock | bellatrix.SigVerifiedBeaconBlock | bellatrix.TrustedBeaconBlock proc process_block*( cfg: RuntimeConfig, state: var bellatrix.BeaconState, blck: SomeBellatrixBlock, flags: UpdateFlags, cache: var StateCache): Result[void, cstring]= ## When there's a new block, we need to verify that the block is sane and ## update the state accordingly - the state is left in an unknown state when ## block application fails (!) ? process_block_header(state, blck, flags, cache) if is_execution_enabled(state, blck.body): ? process_execution_payload( state, blck.body.execution_payload, # TODO this is enough to pass consensus spec tests func(_: ExecutionPayload): bool = true) ? process_randao(state, blck.body, flags, cache) ? process_eth1_data(state, blck.body) let total_active_balance = get_total_active_balance(state, cache) base_reward_per_increment = get_base_reward_per_increment(total_active_balance) ? process_operations( cfg, state, blck.body, base_reward_per_increment, flags, cache) ? process_sync_aggregate( state, blck.body.sync_aggregate, total_active_balance, cache) ok()