nimbus-eth2/beacon_chain/block_pools/spec_cache.nim

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# 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.
import
std/[algorithm, sequtils, sets],
../spec/[
beaconstate, crypto, datatypes, digest, helpers, presets, signatures,
validator],
../extras,
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./block_pools_types, ./chain_dag
# Spec functions implemented based on cached values instead of the full state
func count_active_validators*(epochInfo: EpochRef): uint64 =
epochInfo.shuffled_active_validator_indices.lenu64
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_committee_count_per_slot
func get_committee_count_per_slot*(epochInfo: EpochRef): uint64 =
get_committee_count_per_slot(count_active_validators(epochInfo))
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_beacon_committee
func get_beacon_committee*(
epochRef: EpochRef, slot: Slot, index: CommitteeIndex): seq[ValidatorIndex] =
# Return the beacon committee at ``slot`` for ``index``.
let
committees_per_slot = get_committee_count_per_slot(epochRef)
compute_committee(
epochRef.shuffled_active_validator_indices,
(slot mod SLOTS_PER_EPOCH) * committees_per_slot +
index.uint64,
committees_per_slot * SLOTS_PER_EPOCH
)
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_attesting_indices
func get_attesting_indices*(epochRef: EpochRef,
data: AttestationData,
bits: CommitteeValidatorsBits):
HashSet[ValidatorIndex] =
get_attesting_indices(
bits,
get_beacon_committee(epochRef, data.slot, data.index.CommitteeIndex))
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_indexed_attestation
func get_indexed_attestation*(epochRef: EpochRef, attestation: Attestation): IndexedAttestation =
# Return the indexed attestation corresponding to ``attestation``.
let
attesting_indices =
get_attesting_indices(
epochRef, attestation.data, attestation.aggregation_bits)
IndexedAttestation(
attesting_indices:
List[uint64, Limit MAX_VALIDATORS_PER_COMMITTEE].init(
sorted(mapIt(attesting_indices, it.uint64), system.cmp)),
data: attestation.data,
signature: attestation.signature
)
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_beacon_committee
func get_beacon_committee_len*(
epochRef: EpochRef, slot: Slot, index: CommitteeIndex): uint64 =
# Return the number of members in the beacon committee at ``slot`` for ``index``.
let
committees_per_slot = get_committee_count_per_slot(epochRef)
compute_committee_len(
count_active_validators(epochRef),
(slot mod SLOTS_PER_EPOCH) * committees_per_slot +
index.uint64,
committees_per_slot * SLOTS_PER_EPOCH
)
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#aggregation-selection
func is_aggregator*(epochRef: EpochRef, slot: Slot, index: CommitteeIndex,
slot_signature: ValidatorSig): bool =
let
committee_len = get_beacon_committee_len(epochRef, slot, index)
modulo = max(1'u64, committee_len div TARGET_AGGREGATORS_PER_COMMITTEE)
bytes_to_uint64(eth2digest(slot_signature.toRaw()).data[0..7]) mod modulo == 0
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#is_valid_indexed_attestation
proc is_valid_indexed_attestation*(
fork: Fork, genesis_validators_root: Eth2Digest,
epochRef: EpochRef, indexed_attestation: SomeIndexedAttestation,
flags: UpdateFlags): Result[void, cstring] =
# Check if ``indexed_attestation`` is not empty, has sorted and unique
# indices and has a valid aggregate signature.
template is_sorted_and_unique(s: untyped): bool =
var res = true
for i in 1 ..< s.len:
if s[i - 1].uint64 >= s[i].uint64:
res = false
break
res
if len(indexed_attestation.attesting_indices) == 0:
return err("indexed_attestation: no attesting indices")
# Not from spec, but this function gets used in front-line roles, not just
# behind firewall.
let num_validators = epochRef.validator_keys.lenu64
if anyIt(indexed_attestation.attesting_indices, it >= num_validators):
return err("indexed attestation: not all indices valid validators")
if not is_sorted_and_unique(indexed_attestation.attesting_indices):
return err("indexed attestation: indices not sorted and unique")
# Verify aggregate signature
if skipBLSValidation notin flags:
# TODO: fuse loops with blsFastAggregateVerify
let pubkeys = mapIt(
indexed_attestation.attesting_indices, epochRef.validator_keys[it])
if not verify_attestation_signature(
fork, genesis_validators_root, indexed_attestation.data,
pubkeys, indexed_attestation.signature):
return err("indexed attestation: signature verification failure")
ok()
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func makeAttestationData*(
epochRef: EpochRef, bs: BlockSlot,
committee_index: uint64): AttestationData =
## Create an attestation / vote for the block `bs` using the
## data in `epochRef` to fill in the rest of the fields.
## `epochRef` is the epoch information corresponding to the `bs` advanced to
## the slot we're attesting to.
let
slot = bs.slot
current_epoch = slot.compute_epoch_at_slot()
epoch_boundary_slot = compute_start_slot_at_epoch(current_epoch)
epoch_boundary_block = bs.blck.atSlot(epoch_boundary_slot)
doAssert current_epoch == epochRef.epoch
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#attestation-data
AttestationData(
slot: slot,
index: committee_index,
beacon_block_root: bs.blck.root,
source: epochRef.current_justified_checkpoint,
target: Checkpoint(
epoch: current_epoch,
root: epoch_boundary_block.blck.root
)
)