426 lines
16 KiB
Nim
426 lines
16 KiB
Nim
# beacon_chain
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# Copyright (c) 2018 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import
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chronicles, math, options, sequtils,
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../extras, ../ssz,
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./crypto, ./datatypes, ./digest, ./helpers, ./validator
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func get_effective_balance*(state: BeaconState, index: Uint24): uint64 =
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# Validators collect rewards which increases their balance but not their
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# influence. Validators may also lose balance if they fail to do their duty
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# in which case their influence decreases. Once they drop below a certain
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# balance, they're removed from the validator registry.
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min(state.validator_balances[index], MAX_DEPOSIT * GWEI_PER_ETH)
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func sum_effective_balances*(
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state: BeaconState, validator_indices: openArray[Uint24]): uint64 =
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# TODO spec - add as helper? Used pretty often
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for index in validator_indices:
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result += get_effective_balance(state, index)
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func validate_proof_of_possession(state: BeaconState,
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pubkey: ValidatorPubKey,
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proof_of_possession: ValidatorSig,
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withdrawal_credentials: Eth2Digest,
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randao_commitment: Eth2Digest): bool =
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let proof_of_possession_data = DepositInput(
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pubkey: pubkey,
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withdrawal_credentials: withdrawal_credentials,
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randao_commitment: randao_commitment
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)
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bls_verify(
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pubkey,
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hash_tree_root_final(proof_of_possession_data).data,
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proof_of_possession,
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get_domain(
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state.fork_data,
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state.slot,
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DOMAIN_DEPOSIT,
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)
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)
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func process_deposit(state: var BeaconState,
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pubkey: ValidatorPubKey,
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deposit: uint64,
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proof_of_possession: ValidatorSig,
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withdrawal_credentials: Eth2Digest,
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randao_commitment: Eth2Digest,
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flags: UpdateFlags): Uint24 =
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## Process a deposit from Ethereum 1.0.
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if skipValidation notin flags:
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# TODO return error
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doAssert validate_proof_of_possession(
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state, pubkey, proof_of_possession, withdrawal_credentials,
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randao_commitment)
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let validator_pubkeys = state.validator_registry.mapIt(it.pubkey)
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if pubkey notin validator_pubkeys:
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# Add new validator
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let validator = ValidatorRecord(
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pubkey: pubkey,
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withdrawal_credentials: withdrawal_credentials,
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randao_commitment: randao_commitment,
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randao_layers: 0,
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status: PENDING_ACTIVATION,
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latest_status_change_slot: state.slot,
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exit_count: 0
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)
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let index = min_empty_validator_index(
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state.validator_registry, state.validator_balances, state.slot)
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if index.isNone():
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state.validator_registry.add(validator)
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state.validator_balances.add(deposit)
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(len(state.validator_registry) - 1).Uint24
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else:
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state.validator_registry[index.get()] = validator
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state.validator_balances[index.get()] = deposit
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index.get().Uint24
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else:
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# Increase balance by deposit
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let index = validator_pubkeys.find(pubkey)
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let validator = addr state.validator_registry[index]
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assert state.validator_registry[index].withdrawal_credentials ==
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withdrawal_credentials
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state.validator_balances[index] += deposit
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index.Uint24
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func activate_validator(state: var BeaconState,
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index: Uint24) =
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## Activate the validator with the given ``index``.
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let validator = addr state.validator_registry[index]
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if validator.status != PENDING_ACTIVATION:
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return
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validator.status = ACTIVE
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validator.latest_status_change_slot = state.slot
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state.validator_registry_delta_chain_tip =
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get_new_validator_registry_delta_chain_tip(
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state.validator_registry_delta_chain_tip,
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index,
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validator.pubkey,
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ACTIVATION,
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)
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func initiate_validator_exit(state: var BeaconState,
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index: Uint24) =
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## Initiate exit for the validator with the given ``index``.
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let validator = addr state.validator_registry[index]
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if validator.status != ACTIVE:
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return
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validator.status = ACTIVE_PENDING_EXIT
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validator.latest_status_change_slot = state.slot
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func exit_validator(state: var BeaconState,
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index: Uint24,
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new_status: ValidatorStatusCodes) =
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## Exit the validator with the given ``index``.
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let
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validator = addr state.validator_registry[index]
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prev_status = validator.status
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if prev_status == EXITED_WITH_PENALTY:
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return
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validator.status = new_status
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validator.latest_status_change_slot = state.slot
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if new_status == EXITED_WITH_PENALTY:
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state.latest_penalized_exit_balances[
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(state.slot div COLLECTIVE_PENALTY_CALCULATION_PERIOD).int] +=
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get_effective_balance(state, index)
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let
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whistleblower_index =
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get_beacon_proposer_index(state, state.slot)
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whistleblower_reward =
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get_effective_balance(state, index) div WHISTLEBLOWER_REWARD_QUOTIENT
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state.validator_balances[whistleblower_index] += whistleblower_reward
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state.validator_balances[index] -= whistleblower_reward
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if prev_status == EXITED_WITHOUT_PENALTY:
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return
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# The following updates only occur if not previous exited
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state.validator_registry_exit_count += 1
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validator.exit_count = state.validator_registry_exit_count
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state.validator_registry_delta_chain_tip =
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get_new_validator_registry_delta_chain_tip(
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state.validator_registry_delta_chain_tip,
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index,
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validator.pubkey,
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ValidatorSetDeltaFlags.EXIT
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)
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# Remove validator from persistent committees
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for committee in state.persistent_committees.mitems():
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for i, validator_index in committee:
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if validator_index == index:
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committee.delete(i)
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break
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func update_validator_status*(state: var BeaconState,
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index: Uint24,
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new_status: ValidatorStatusCodes) =
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## Update the validator status with the given ``index`` to ``new_status``.
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## Handle other general accounting related to this status update.
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if new_status == ACTIVE:
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activate_validator(state, index)
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if new_status == ACTIVE_PENDING_EXIT:
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initiate_validator_exit(state, index)
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if new_status in [EXITED_WITH_PENALTY, EXITED_WITHOUT_PENALTY]:
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exit_validator(state, index, new_status)
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func get_initial_beacon_state*(
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initial_validator_deposits: openArray[Deposit],
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genesis_time: uint64,
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processed_pow_receipt_root: Eth2Digest,
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flags: UpdateFlags = {}): BeaconState =
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## BeaconState constructor
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##
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## Before the beacon chain starts, validators will register in the Eth1 chain
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## and deposit ETH. When enough many validators have registered, a
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## `ChainStart` log will be emitted and the beacon chain can start beaconing.
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##
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## Because the state root hash is part of the genesis block, the beacon state
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## must be calculated before creating the genesis block.
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# Induct validators
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# Not in spec: the system doesn't work unless there are at least EPOCH_LENGTH
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# validators - there needs to be at least one member in each committee -
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# good to know for testing, though arguably the system is not that useful at
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# at that point :)
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assert initial_validator_deposits.len >= EPOCH_LENGTH
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var state = BeaconState(
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# Misc
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slot: INITIAL_SLOT_NUMBER,
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genesis_time: genesis_time,
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fork_data: ForkData(
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pre_fork_version: INITIAL_FORK_VERSION,
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post_fork_version: INITIAL_FORK_VERSION,
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fork_slot: INITIAL_SLOT_NUMBER,
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),
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validator_registry_latest_change_slot: INITIAL_SLOT_NUMBER,
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validator_registry_exit_count: 0,
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validator_registry_delta_chain_tip: ZERO_HASH,
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# Finality
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previous_justified_slot: INITIAL_SLOT_NUMBER,
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justified_slot: INITIAL_SLOT_NUMBER,
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finalized_slot: INITIAL_SLOT_NUMBER,
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# PoW receipt root
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processed_pow_receipt_root: processed_pow_receipt_root,
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)
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# handle initial deposits and activations
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for deposit in initial_validator_deposits:
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let validator_index = process_deposit(
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state,
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deposit.deposit_data.deposit_input.pubkey,
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deposit.deposit_data.value,
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deposit.deposit_data.deposit_input.proof_of_possession,
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deposit.deposit_data.deposit_input.withdrawal_credentials,
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deposit.deposit_data.deposit_input.randao_commitment,
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flags
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)
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if state.validator_balances[validator_index] >= MAX_DEPOSIT:
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update_validator_status(state, validator_index, ACTIVE)
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# set initial committee shuffling
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let
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initial_shuffling =
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get_new_shuffling(Eth2Digest(), state.validator_registry, 0)
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# initial_shuffling + initial_shuffling in spec, but more ugly
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for i, n in initial_shuffling:
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state.shard_committees_at_slots[i] = n
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state.shard_committees_at_slots[EPOCH_LENGTH + i] = n
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# set initial persistent shuffling
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let active_validator_indices =
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get_active_validator_indices(state.validator_registry)
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state.persistent_committees = split(shuffle(
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active_validator_indices, ZERO_HASH), SHARD_COUNT)
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state
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func get_block_root*(state: BeaconState,
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slot: uint64): Eth2Digest =
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doAssert state.slot <= slot + LATEST_BLOCK_ROOTS_LENGTH
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doAssert slot < state.slot
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state.latest_block_roots[slot mod LATEST_BLOCK_ROOTS_LENGTH]
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func get_attestation_participants*(state: BeaconState,
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attestation_data: AttestationData,
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participation_bitfield: seq[byte]): seq[Uint24] =
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## Attestation participants in the attestation data are called out in a
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## bit field that corresponds to the committee of the shard at the time - this
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## function converts it to list of indices in to BeaconState.validators
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## Returns empty list if the shard is not found
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# TODO Linear search through shard list? borderline ok, it's a small list
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# TODO bitfield type needed, once bit order settles down
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# TODO iterator candidate
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let
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sncs_for_slot = get_shard_committees_at_slot(
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state, attestation_data.slot)
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for snc in sncs_for_slot:
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if snc.shard != attestation_data.shard:
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continue
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# TODO investigate functional library / approach to help avoid loop bugs
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assert len(participation_bitfield) == ceil_div8(len(snc.committee))
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for i, vindex in snc.committee:
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if bitIsSet(participation_bitfield, i):
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result.add(vindex)
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return # found the shard, we're done
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func process_ejections*(state: var BeaconState) =
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## Iterate through the validator registry
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## and eject active validators with balance below ``EJECTION_BALANCE``.
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for index in get_active_validator_indices(state.validator_registry):
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if state.validator_balances[index] < EJECTION_BALANCE:
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exit_validator(state, index, EXITED_WITHOUT_PENALTY)
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func update_validator_registry*(state: var BeaconState) =
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let
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active_validator_indices =
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get_active_validator_indices(state.validator_registry)
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# The total effective balance of active validators
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total_balance = sum_effective_balances(state, active_validator_indices)
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# The maximum balance churn in Gwei (for deposits and exits separately)
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max_balance_churn = max(
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MAX_DEPOSIT * GWEI_PER_ETH,
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total_balance div (2 * MAX_BALANCE_CHURN_QUOTIENT)
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)
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# Activate validators within the allowable balance churn
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var balance_churn = 0'u64
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for index, validator in state.validator_registry:
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if validator.status == PENDING_ACTIVATION and
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state.validator_balances[index] >= MAX_DEPOSIT * GWEI_PER_ETH:
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# Check the balance churn would be within the allowance
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balance_churn += get_effective_balance(state, index.Uint24)
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if balance_churn > max_balance_churn:
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break
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# Activate validator
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update_validator_status(state, index.Uint24, ACTIVE)
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# Exit validators within the allowable balance churn
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balance_churn = 0
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for index, validator in state.validator_registry:
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if validator.status == ACTIVE_PENDING_EXIT:
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# Check the balance churn would be within the allowance
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balance_churn += get_effective_balance(state, index.Uint24)
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if balance_churn > max_balance_churn:
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break
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# Exit validator
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update_validator_status(state, index.Uint24, EXITED_WITHOUT_PENALTY)
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# Calculate the total ETH that has been penalized in the last ~2-3 withdrawal periods
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let
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period_index = (state.slot div COLLECTIVE_PENALTY_CALCULATION_PERIOD).int
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total_penalties = (
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(state.latest_penalized_exit_balances[period_index]) +
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(if period_index >= 1:
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state.latest_penalized_exit_balances[period_index - 1] else: 0) +
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(if period_index >= 2:
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state.latest_penalized_exit_balances[period_index - 2] else: 0)
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)
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# Calculate penalties for slashed validators
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for index, validator in state.validator_registry:
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if validator.status == EXITED_WITH_PENALTY:
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state.validator_balances[index] -=
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get_effective_balance(state, index.Uint24) *
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min(total_penalties * 3, total_balance) div total_balance
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proc checkAttestation*(
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state: BeaconState, attestation: Attestation, flags: UpdateFlags): bool =
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## Check that an attestation follows the rules of being included in the state
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## at the current slot. When acting as a proposer, the same rules need to
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## be followed!
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##
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## https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestations-1
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if not (attestation.data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot):
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warn("Attestation too new",
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attestation_slot = attestation.data.slot, state_slot = state.slot)
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return
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if not (attestation.data.slot + EPOCH_LENGTH >= state.slot):
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warn("Attestation too old",
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attestation_slot = attestation.data.slot, state_slot = state.slot)
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return
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let expected_justified_slot =
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if attestation.data.slot >= state.slot - (state.slot mod EPOCH_LENGTH):
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state.justified_slot
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else:
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state.previous_justified_slot
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if not (attestation.data.justified_slot == expected_justified_slot):
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warn("Unexpected justified slot",
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attestation_justified_slot = attestation.data.justified_slot,
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expected_justified_slot)
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return
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let expected_justified_block_root =
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get_block_root(state, attestation.data.justified_slot)
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if not (attestation.data.justified_block_root == expected_justified_block_root):
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warn("Unexpected justified block root",
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attestation_justified_block_root = attestation.data.justified_block_root,
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expected_justified_block_root)
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return
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if not (state.latest_crosslinks[attestation.data.shard].shard_block_root in [
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attestation.data.latest_crosslink_root,
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attestation.data.shard_block_root]):
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warn("Unexpected crosslink shard_block_root")
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return
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let
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participants = get_attestation_participants(
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state, attestation.data, attestation.participation_bitfield)
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group_public_key = bls_aggregate_pubkeys(
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participants.mapIt(state.validator_registry[it].pubkey))
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if skipValidation notin flags:
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# Verify that aggregate_signature verifies using the group pubkey.
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let msg = hash_tree_root_final(attestation.data)
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if not bls_verify(
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group_public_key, @(msg.data) & @[0'u8], attestation.aggregate_signature,
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get_domain(state.fork_data, attestation.data.slot, DOMAIN_ATTESTATION)
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):
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warn("Invalid attestation group signature")
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return
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# To be removed in Phase1:
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if attestation.data.shard_block_root != ZERO_HASH:
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warn("Invalid shard block root")
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return
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true
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