358 lines
14 KiB
Nim
358 lines
14 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2020 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 https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://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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# State transition - block processing, as described in
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# https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beacon-chain-state-transition-function
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#
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# The purpose of this code right is primarily educational, to help piece
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# together the mechanics of the beacon state and to discover potential problem
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# areas.
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#
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# The entry point is `process_block` which is at the bottom of this file.
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#
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# General notes about the code (TODO):
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# * Weird styling - the sections taken from the spec use python styling while
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# the others use NEP-1 - helps grepping identifiers in spec
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# * We mix procedural and functional styles for no good reason, except that the
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# spec does so also.
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# * For indices, we get a mix of uint64, ValidatorIndex and int - this is currently
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# swept under the rug with casts
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# When updating the code, add TODO sections to mark where there are clear
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# improvements to be made - other than that, keep things similar to spec for
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# now.
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{.push raises: [Defect].}
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import
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algorithm, collections/sets, chronicles, options, sequtils, sets,
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../extras, ../ssz/merkleization, metrics,
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./beaconstate, ./crypto, ./datatypes, ./digest, ./helpers, ./validator,
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./signatures, ./presets,
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../../nbench/bench_lab
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# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#additional-metrics
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declareGauge beacon_current_live_validators, "Number of active validators that successfully included attestation on chain for current epoch" # On block
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declareGauge beacon_previous_live_validators, "Number of active validators that successfully included attestation on chain for previous epoch" # On block
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#block-header
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func process_block_header*(
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state: var BeaconState, blck: SomeBeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): Result[void, cstring] {.nbench.} =
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# Verify that the slots match
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if not (blck.slot == state.slot):
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return err("process_block_header: slot mismatch")
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# Verify that the block is newer than latest block header
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if not (blck.slot > state.latest_block_header.slot):
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return err("process_block_header: block not newer than latest block header")
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# Verify that proposer index is the correct index
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let proposer_index = get_beacon_proposer_index(state, stateCache)
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if proposer_index.isNone:
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return err("process_block_header: proposer missing")
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if not (blck.proposer_index.ValidatorIndex == proposer_index.get):
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return err("process_block_header: proposer index incorrect")
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# Verify that the parent matches
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if not (blck.parent_root == hash_tree_root(state.latest_block_header)):
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return err("process_block_header: previous block root mismatch")
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# Verify proposer is not slashed
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if state.validators[proposer_index.get].slashed:
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return err("process_block_header: proposer slashed")
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# Cache current block as the new latest block
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state.latest_block_header = BeaconBlockHeader(
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slot: blck.slot,
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proposer_index: blck.proposer_index,
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parent_root: blck.parent_root,
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# state_root: zeroed, overwritten in the next `process_slot` call
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body_root: hash_tree_root(blck.body),
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)
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ok()
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func `xor`[T: array](a, b: T): T =
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for i in 0..<result.len:
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result[i] = a[i] xor b[i]
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#randao
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proc process_randao(
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state: var BeaconState, body: SomeBeaconBlockBody, flags: UpdateFlags,
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stateCache: var StateCache): bool {.nbench.} =
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let
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proposer_index = get_beacon_proposer_index(state, stateCache)
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if proposer_index.isNone:
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debug "Proposer index missing, probably along with any active validators"
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return false
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# Verify RANDAO reveal
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let
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epoch = state.get_current_epoch()
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if skipBLSValidation notin flags:
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let proposer_pubkey = state.validators[proposer_index.get].pubkey
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if not verify_epoch_signature(
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state.fork, state.genesis_validators_root, epoch, proposer_pubkey,
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body.randao_reveal):
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notice "Randao mismatch", proposer_pubkey = shortLog(proposer_pubkey),
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epoch,
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signature = shortLog(body.randao_reveal),
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slot = state.slot
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return false
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# Mix it in
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let
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mix = get_randao_mix(state, epoch)
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rr = eth2digest(body.randao_reveal.toRaw()).data
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state.randao_mixes[epoch mod EPOCHS_PER_HISTORICAL_VECTOR].data =
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mix.data xor rr
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#eth1-data
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func process_eth1_data(state: var BeaconState, body: SomeBeaconBlockBody) {.nbench.}=
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state.eth1_data_votes.add body.eth1_data
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if state.eth1_data_votes.asSeq.count(body.eth1_data).uint64 * 2 >
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SLOTS_PER_ETH1_VOTING_PERIOD:
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state.eth1_data = body.eth1_data
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#is_slashable_validator
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func is_slashable_validator(validator: Validator, epoch: Epoch): bool =
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# Check if ``validator`` is slashable.
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(not validator.slashed) and
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(validator.activation_epoch <= epoch) and
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(epoch < validator.withdrawable_epoch)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#proposer-slashings
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proc process_proposer_slashing*(
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state: var BeaconState, proposer_slashing: ProposerSlashing,
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flags: UpdateFlags, stateCache: var StateCache):
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Result[void, cstring] {.nbench.} =
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let
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header_1 = proposer_slashing.signed_header_1.message
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header_2 = proposer_slashing.signed_header_2.message
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# Not from spec
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if header_1.proposer_index >= state.validators.lenu64:
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return err("process_proposer_slashing: invalid proposer index")
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# Verify header slots match
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if not (header_1.slot == header_2.slot):
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return err("process_proposer_slashing: slot mismatch")
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# Verify header proposer indices match
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if not (header_1.proposer_index == header_2.proposer_index):
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return err("process_proposer_slashing: proposer indices mismatch")
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# Verify the headers are different
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if not (header_1 != header_2):
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return err("process_proposer_slashing: headers not different")
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# Verify the proposer is slashable
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let proposer = state.validators[header_1.proposer_index]
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if not is_slashable_validator(proposer, get_current_epoch(state)):
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return err("process_proposer_slashing: slashed proposer")
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# Verify signatures
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if skipBlsValidation notin flags:
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for i, signed_header in [proposer_slashing.signed_header_1,
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proposer_slashing.signed_header_2]:
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if not verify_block_signature(
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state.fork, state.genesis_validators_root, signed_header.message.slot,
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signed_header.message, proposer.pubkey, signed_header.signature):
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return err("process_proposer_slashing: invalid signature")
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slash_validator(state, header_1.proposer_index.ValidatorIndex, stateCache)
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#is_slashable_attestation_data
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func is_slashable_attestation_data*(
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data_1: AttestationData, data_2: AttestationData): bool =
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## Check if ``data_1`` and ``data_2`` are slashable according to Casper FFG
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## rules.
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# Double vote
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(data_1 != data_2 and data_1.target.epoch == data_2.target.epoch) or
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# Surround vote
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(data_1.source.epoch < data_2.source.epoch and
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data_2.target.epoch < data_1.target.epoch)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#attester-slashings
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proc process_attester_slashing*(
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state: var BeaconState,
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attester_slashing: AttesterSlashing,
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flags: UpdateFlags,
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stateCache: var StateCache
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): Result[void, cstring] {.nbench.}=
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let
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attestation_1 = attester_slashing.attestation_1
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attestation_2 = attester_slashing.attestation_2
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if not is_slashable_attestation_data(
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attestation_1.data, attestation_2.data):
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return err("Attester slashing: surround or double vote check failed")
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if not is_valid_indexed_attestation(state, attestation_1, flags).isOk():
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return err("Attester slashing: invalid attestation 1")
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if not is_valid_indexed_attestation(state, attestation_2, flags).isOk():
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return err("Attester slashing: invalid attestation 2")
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var slashed_any = false
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for index in sorted(toSeq(intersection(
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toHashSet(attestation_1.attesting_indices.asSeq),
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toHashSet(attestation_2.attesting_indices.asSeq)).items), system.cmp):
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if is_slashable_validator(
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state.validators[index], get_current_epoch(state)):
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slash_validator(state, index.ValidatorIndex, stateCache)
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slashed_any = true
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if not slashed_any:
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return err("Attester slashing: Trying to slash participant(s) twice")
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#voluntary-exits
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proc process_voluntary_exit*(
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state: var BeaconState,
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signed_voluntary_exit: SignedVoluntaryExit,
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flags: UpdateFlags,
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cache: var StateCache): Result[void, cstring] {.nbench.} =
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let voluntary_exit = signed_voluntary_exit.message
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# Not in spec. Check that validator_index is in range
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if voluntary_exit.validator_index >= state.validators.lenu64:
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return err("Exit: invalid validator index")
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let validator = state.validators[voluntary_exit.validator_index]
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# Verify the validator is active
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if not is_active_validator(validator, get_current_epoch(state)):
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return err("Exit: validator not active")
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# Verify exit has not been initiated
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if validator.exit_epoch != FAR_FUTURE_EPOCH:
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return err("Exit: validator has exited")
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# Exits must specify an epoch when they become valid; they are not valid
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# before then
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if not (get_current_epoch(state) >= voluntary_exit.epoch):
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return err("Exit: exit epoch not passed")
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# Verify the validator has been active long enough
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if not (get_current_epoch(state) >= validator.activation_epoch +
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SHARD_COMMITTEE_PERIOD):
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return err("Exit: not in validator set long enough")
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# Verify signature
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if skipBlsValidation notin flags:
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if not verify_voluntary_exit_signature(
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state.fork, state.genesis_validators_root, voluntary_exit,
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validator.pubkey, signed_voluntary_exit.signature):
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return err("Exit: invalid signature")
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# Initiate exit
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debug "Exit: processing voluntary exit (validator_leaving)",
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index = voluntary_exit.validator_index,
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num_validators = state.validators.len,
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epoch = voluntary_exit.epoch,
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current_epoch = get_current_epoch(state),
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validator_slashed = validator.slashed,
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validator_withdrawable_epoch = validator.withdrawable_epoch,
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validator_exit_epoch = validator.exit_epoch,
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validator_effective_balance = validator.effective_balance
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initiate_validator_exit(
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state, voluntary_exit.validator_index.ValidatorIndex, cache)
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#operations
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proc process_operations(preset: RuntimePreset,
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state: var BeaconState,
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body: SomeBeaconBlockBody,
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flags: UpdateFlags,
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cache: var StateCache): Result[void, cstring] {.nbench.} =
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# Verify that outstanding deposits are processed up to the maximum number of
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# deposits
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let
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req_deposits = min(MAX_DEPOSITS,
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state.eth1_data.deposit_count - state.eth1_deposit_index)
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if state.eth1_data.deposit_count < state.eth1_deposit_index or
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body.deposits.lenu64 != req_deposits:
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return err("incorrect number of deposits")
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template for_ops(operations: auto, fn: auto) =
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for operation in operations:
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let res = fn(state, operation, flags, cache)
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if res.isErr:
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return res
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for_ops(body.proposer_slashings, process_proposer_slashing)
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for_ops(body.attester_slashings, process_attester_slashing)
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for_ops(body.attestations, process_attestation)
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for deposit in body.deposits:
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let res = process_deposit(preset, state, deposit, flags)
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if res.isErr:
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return res
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for_ops(body.voluntary_exits, process_voluntary_exit)
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#block-processing
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proc process_block*(
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preset: RuntimePreset,
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state: var BeaconState, blck: SomeBeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): bool {.nbench.}=
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## When there's a new block, we need to verify that the block is sane and
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## update the state accordingly
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# TODO when there's a failure, we should reset the state!
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# TODO probably better to do all verification first, then apply state changes
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# Adds nontrivial additional computation, but only does so when metrics
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# enabled.
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beacon_current_live_validators.set(toHashSet(
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mapIt(state.current_epoch_attestations, it.proposerIndex)).len.int64)
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beacon_previous_live_validators.set(toHashSet(
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mapIt(state.previous_epoch_attestations, it.proposerIndex)).len.int64)
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logScope:
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blck = shortLog(blck)
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let res_block = process_block_header(state, blck, flags, stateCache)
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if res_block.isErr:
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debug "Block header not valid",
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block_header_error = $(res_block.error),
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slot = state.slot
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return false
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if not process_randao(state, blck.body, flags, stateCache):
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debug "Randao failure", slot = shortLog(state.slot)
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return false
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process_eth1_data(state, blck.body)
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let res_ops = process_operations(preset, state, blck.body, flags, stateCache)
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if res_ops.isErr:
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debug "process_operations encountered error",
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operation_error = $(res_ops.error),
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slot = state.slot,
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eth1_deposit_index = state.eth1_deposit_index,
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deposit_root = shortLog(state.eth1_data.deposit_root)
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return false
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true
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