278 lines
12 KiB
Nim
278 lines
12 KiB
Nim
# beacon_chain
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# Copyright (c) 2021-2023 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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{.push raises: [].}
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import
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stew/[bitops2, objects],
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datatypes/altair,
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helpers
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from ../consensus_object_pools/block_pools_types import VerifierError
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export block_pools_types.VerifierError
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/altair/light-client/sync-protocol.md#initialize_light_client_store
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func initialize_light_client_store*(
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trusted_block_root: Eth2Digest,
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bootstrap: ForkyLightClientBootstrap,
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cfg: RuntimeConfig
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): auto =
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type ResultType =
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Result[typeof(bootstrap).kind.LightClientStore, VerifierError]
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if not is_valid_light_client_header(bootstrap.header, cfg):
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return ResultType.err(VerifierError.Invalid)
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if hash_tree_root(bootstrap.header.beacon) != trusted_block_root:
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return ResultType.err(VerifierError.Invalid)
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if not is_valid_merkle_branch(
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hash_tree_root(bootstrap.current_sync_committee),
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bootstrap.current_sync_committee_branch,
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log2trunc(altair.CURRENT_SYNC_COMMITTEE_INDEX),
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get_subtree_index(altair.CURRENT_SYNC_COMMITTEE_INDEX),
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bootstrap.header.beacon.state_root):
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return ResultType.err(VerifierError.Invalid)
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return ResultType.ok(typeof(bootstrap).kind.LightClientStore(
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finalized_header: bootstrap.header,
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current_sync_committee: bootstrap.current_sync_committee,
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optimistic_header: bootstrap.header))
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/altair/light-client/sync-protocol.md#validate_light_client_update
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proc validate_light_client_update*(
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store: ForkyLightClientStore,
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update: SomeForkyLightClientUpdate,
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current_slot: Slot,
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cfg: RuntimeConfig,
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genesis_validators_root: Eth2Digest): Result[void, VerifierError] =
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# Verify sync committee has sufficient participants
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template sync_aggregate(): auto = update.sync_aggregate
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template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
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let num_active_participants = countOnes(sync_committee_bits).uint64
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if num_active_participants < MIN_SYNC_COMMITTEE_PARTICIPANTS:
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return err(VerifierError.Invalid)
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# Verify update does not skip a sync committee period
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if not is_valid_light_client_header(update.attested_header, cfg):
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return err(VerifierError.Invalid)
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when update is SomeForkyLightClientUpdateWithFinality:
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if update.attested_header.beacon.slot < update.finalized_header.beacon.slot:
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return err(VerifierError.Invalid)
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if update.signature_slot <= update.attested_header.beacon.slot:
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return err(VerifierError.Invalid)
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if current_slot < update.signature_slot:
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return err(VerifierError.UnviableFork)
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let
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store_period = store.finalized_header.beacon.slot.sync_committee_period
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signature_period = update.signature_slot.sync_committee_period
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is_next_sync_committee_known = store.is_next_sync_committee_known
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if is_next_sync_committee_known:
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if signature_period notin [store_period, store_period + 1]:
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return err(VerifierError.MissingParent)
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else:
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if signature_period != store_period:
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return err(VerifierError.MissingParent)
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# Verify update is relevant
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let attested_period = update.attested_header.beacon.slot.sync_committee_period
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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let is_sync_committee_update = update.is_sync_committee_update
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if update.attested_header.beacon.slot <= store.finalized_header.beacon.slot:
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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if is_next_sync_committee_known:
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return err(VerifierError.Duplicate)
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if attested_period != store_period or not is_sync_committee_update:
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return err(VerifierError.Duplicate)
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else:
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return err(VerifierError.Duplicate)
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# Verify that the `finality_branch`, if present, confirms `finalized_header`
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# to match the finalized checkpoint root saved in the state of
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# `attested_header`. Note that the genesis finalized checkpoint root is
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# represented as a zero hash.
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when update is SomeForkyLightClientUpdateWithFinality:
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if not update.is_finality_update:
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if update.finalized_header != default(typeof(update.finalized_header)):
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return err(VerifierError.Invalid)
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else:
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var finalized_root {.noinit.}: Eth2Digest
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if update.finalized_header.beacon.slot != GENESIS_SLOT:
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if not is_valid_light_client_header(update.finalized_header, cfg):
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return err(VerifierError.Invalid)
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finalized_root = hash_tree_root(update.finalized_header.beacon)
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elif update.finalized_header == default(typeof(update.finalized_header)):
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finalized_root.reset()
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else:
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return err(VerifierError.Invalid)
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if not is_valid_merkle_branch(
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finalized_root,
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update.finality_branch,
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log2trunc(altair.FINALIZED_ROOT_INDEX),
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get_subtree_index(altair.FINALIZED_ROOT_INDEX),
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update.attested_header.beacon.state_root):
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return err(VerifierError.Invalid)
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# Verify that the `next_sync_committee`, if present, actually is the
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# next sync committee saved in the state of the `attested_header`
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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if not is_sync_committee_update:
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if update.next_sync_committee !=
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default(typeof(update.next_sync_committee)):
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return err(VerifierError.Invalid)
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else:
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if attested_period == store_period and is_next_sync_committee_known:
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if update.next_sync_committee != store.next_sync_committee:
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return err(VerifierError.UnviableFork)
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if not is_valid_merkle_branch(
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hash_tree_root(update.next_sync_committee),
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update.next_sync_committee_branch,
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log2trunc(altair.NEXT_SYNC_COMMITTEE_INDEX),
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get_subtree_index(altair.NEXT_SYNC_COMMITTEE_INDEX),
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update.attested_header.beacon.state_root):
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return err(VerifierError.Invalid)
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# Verify sync committee aggregate signature
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let sync_committee =
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if signature_period == store_period:
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unsafeAddr store.current_sync_committee
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else:
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unsafeAddr store.next_sync_committee
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var participant_pubkeys =
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newSeqOfCap[ValidatorPubKey](num_active_participants)
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for idx, bit in sync_aggregate.sync_committee_bits:
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if bit:
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participant_pubkeys.add(sync_committee.pubkeys.data[idx])
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let
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fork_version_slot = max(update.signature_slot, 1.Slot) - 1
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fork_version = cfg.forkVersionAtEpoch(fork_version_slot.epoch)
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domain = compute_domain(
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DOMAIN_SYNC_COMMITTEE, fork_version, genesis_validators_root)
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signing_root = compute_signing_root(update.attested_header.beacon, domain)
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if not blsFastAggregateVerify(
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participant_pubkeys, signing_root.data,
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sync_aggregate.sync_committee_signature):
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return err(VerifierError.UnviableFork)
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ok()
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/altair/light-client/sync-protocol.md#apply_light_client_update
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func apply_light_client_update(
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store: var ForkyLightClientStore,
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update: SomeForkyLightClientUpdate): bool =
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var didProgress = false
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let
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store_period = store.finalized_header.beacon.slot.sync_committee_period
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finalized_period = update.finalized_header.beacon.slot.sync_committee_period
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if not store.is_next_sync_committee_known:
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assert finalized_period == store_period
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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store.next_sync_committee = update.next_sync_committee
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if store.is_next_sync_committee_known:
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didProgress = true
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elif finalized_period == store_period + 1:
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store.current_sync_committee = store.next_sync_committee
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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store.next_sync_committee = update.next_sync_committee
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else:
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store.next_sync_committee.reset()
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store.previous_max_active_participants =
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store.current_max_active_participants
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store.current_max_active_participants = 0
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didProgress = true
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if update.finalized_header.beacon.slot > store.finalized_header.beacon.slot:
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store.finalized_header = update.finalized_header
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if store.finalized_header.beacon.slot > store.optimistic_header.beacon.slot:
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store.optimistic_header = store.finalized_header
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didProgress = true
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didProgress
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/altair/light-client/sync-protocol.md#process_light_client_store_force_update
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type
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ForceUpdateResult* = enum
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NoUpdate,
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DidUpdateWithoutSupermajority,
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DidUpdateWithoutFinality
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func process_light_client_store_force_update*(
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store: var ForkyLightClientStore,
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current_slot: Slot): ForceUpdateResult {.discardable.} =
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var res = NoUpdate
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if store.best_valid_update.isSome and
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current_slot > store.finalized_header.beacon.slot + UPDATE_TIMEOUT:
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# Forced best update when the update timeout has elapsed.
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# Because the apply logic waits for `finalized_header.beacon.slot`
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# to indicate sync committee finality, the `attested_header` may be
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# treated as `finalized_header` in extended periods of non-finality
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# to guarantee progression into later sync committee periods according
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# to `is_better_update`.
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template best(): auto = store.best_valid_update.get
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if best.finalized_header.beacon.slot <= store.finalized_header.beacon.slot:
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best.finalized_header = best.attested_header
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if apply_light_client_update(store, best):
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template sync_aggregate(): auto = best.sync_aggregate
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template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
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let num_active_participants = countOnes(sync_committee_bits).uint64
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if num_active_participants * 3 < static(sync_committee_bits.len * 2):
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res = DidUpdateWithoutSupermajority
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else:
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res = DidUpdateWithoutFinality
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store.best_valid_update.reset()
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res
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/altair/light-client/sync-protocol.md#process_light_client_update
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proc process_light_client_update*(
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store: var ForkyLightClientStore,
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update: SomeForkyLightClientUpdate,
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current_slot: Slot,
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cfg: RuntimeConfig,
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genesis_validators_root: Eth2Digest): Result[void, VerifierError] =
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? validate_light_client_update(
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store, update, current_slot, cfg, genesis_validators_root)
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var didProgress = false
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# Update the best update in case we have to force-update to it
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# if the timeout elapses
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if store.best_valid_update.isNone or
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is_better_update(update, store.best_valid_update.get):
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store.best_valid_update = Opt.some(update.toFull)
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didProgress = true
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# Track the maximum number of active participants in the committee signatures
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template sync_aggregate(): auto = update.sync_aggregate
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template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
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let num_active_participants = countOnes(sync_committee_bits).uint64
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if num_active_participants > store.current_max_active_participants:
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store.current_max_active_participants = num_active_participants
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# Update the optimistic header
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if num_active_participants > get_safety_threshold(store) and
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update.attested_header.beacon.slot > store.optimistic_header.beacon.slot:
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store.optimistic_header = update.attested_header
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didProgress = true
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# Update finalized header
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when update is SomeForkyLightClientUpdateWithFinality:
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if num_active_participants * 3 >= static(sync_committee_bits.len * 2):
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var improvesFinality =
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update.finalized_header.beacon.slot > store.finalized_header.beacon.slot
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when update is SomeForkyLightClientUpdateWithSyncCommittee:
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if not improvesFinality and not store.is_next_sync_committee_known:
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improvesFinality =
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update.is_sync_committee_update and update.is_finality_update and
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update.finalized_header.beacon.slot.sync_committee_period ==
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update.attested_header.beacon.slot.sync_committee_period
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if improvesFinality:
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# Normal update through 2/3 threshold
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if apply_light_client_update(store, update):
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didProgress = true
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store.best_valid_update.reset()
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if not didProgress:
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return err(VerifierError.Duplicate)
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ok()
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