341 lines
14 KiB
Nim
341 lines
14 KiB
Nim
# beacon_chain
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# Copyright (c) 2019-2020 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 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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{.push raises: [Defect].}
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import
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options, chronicles,
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./spec/[
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beaconstate, datatypes, crypto, digest, helpers, network, validator,
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signatures],
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./block_pools/[spec_cache, chain_dag, quarantine, spec_cache],
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./attestation_pool, ./beacon_node_types, ./ssz, ./time
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logScope:
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topics = "att_aggr"
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const
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MAXIMUM_GOSSIP_CLOCK_DISPARITY = 500.millis
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#aggregation-selection
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func is_aggregator(state: BeaconState, slot: Slot, index: CommitteeIndex,
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slot_signature: ValidatorSig, cache: var StateCache): bool =
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let
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committee_len = get_beacon_committee_len(state, slot, index, cache)
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modulo = max(1'u64, committee_len div TARGET_AGGREGATORS_PER_COMMITTEE)
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bytes_to_uint64(eth2digest(
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slot_signature.toRaw()).data.toOpenArray(0, 7)) mod modulo == 0
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proc aggregate_attestations*(
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pool: AttestationPool, state: BeaconState, index: CommitteeIndex,
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validatorIndex: ValidatorIndex, privkey: ValidatorPrivKey,
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cache: var StateCache):
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Option[AggregateAndProof] =
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let
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slot = state.slot
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slot_signature = get_slot_signature(
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state.fork, state.genesis_validators_root, slot, privkey)
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doAssert validatorIndex in get_beacon_committee(state, slot, index, cache)
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doAssert index.uint64 < get_committee_count_per_slot(state, slot.epoch, cache)
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# TODO for testing purposes, refactor this into the condition check
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# and just calculation
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#aggregation-selection
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if not is_aggregator(state, slot, index, slot_signature, cache):
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return none(AggregateAndProof)
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let maybe_slot_attestation = getAggregatedAttestation(pool, slot, index)
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if maybe_slot_attestation.isNone:
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return none(AggregateAndProof)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#construct-aggregate
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#aggregateandproof
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some(AggregateAndProof(
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aggregator_index: validatorIndex.uint64,
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aggregate: maybe_slot_attestation.get,
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selection_proof: slot_signature))
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func check_attestation_block_slot(
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pool: AttestationPool, attestationSlot: Slot, attestationBlck: BlockRef): Result[void, cstring] =
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# If we allow voting for very old blocks, the state transaction below will go
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# nuts and keep processing empty slots
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if not (attestationBlck.slot > pool.chainDag.finalizedHead.slot):
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return err("Voting for already-finalized block")
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# we'll also cap it at 4 epochs which is somewhat arbitrary, but puts an
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# upper bound on the processing done to validate the attestation
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# TODO revisit with less arbitrary approach
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if not (attestationSlot >= attestationBlck.slot):
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return err("Voting for block that didn't exist at the time")
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if not ((attestationSlot - attestationBlck.slot) <= uint64(4 * SLOTS_PER_EPOCH)):
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return err("Voting for very old block")
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ok()
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func check_propagation_slot_range(
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data: AttestationData, wallTime: BeaconTime): Result[void, cstring] =
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let
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futureSlot = (wallTime + MAXIMUM_GOSSIP_CLOCK_DISPARITY).toSlot()
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if not futureSlot.afterGenesis or data.slot > futureSlot.slot:
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return err("Attestation slot in the future")
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let
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pastSlot = (wallTime - MAXIMUM_GOSSIP_CLOCK_DISPARITY).toSlot()
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if pastSlot.afterGenesis and
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data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE < pastSlot.slot:
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return err("Attestation slot in the past")
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ok()
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func check_attestation_beacon_block(
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pool: var AttestationPool, attestation: Attestation): Result[void, cstring] =
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# The block being voted for (attestation.data.beacon_block_root) passes
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# validation.
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# We rely on the chain DAG to have been validated, so check for the existence
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# of the block in the pool.
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let attestationBlck = pool.chainDag.getRef(attestation.data.beacon_block_root)
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if attestationBlck.isNil:
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pool.quarantine.addMissing(attestation.data.beacon_block_root)
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return err("Attestation block unknown")
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# Not in spec - check that rewinding to the state is sane
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? check_attestation_block_slot(pool, attestation.data.slot, attestationBlck)
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ok()
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func check_aggregation_count(
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attestation: Attestation, singular: bool): Result[void, cstring] =
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var onesCount = 0
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# TODO a cleverer algorithm, along the lines of countOnes() in nim-stew
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# But that belongs in nim-stew, since it'd break abstraction layers, to
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# use details of its representation from nim-beacon-chain.
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for aggregation_bit in attestation.aggregation_bits:
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if not aggregation_bit:
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continue
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onesCount += 1
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if singular: # More than one ok
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if onesCount > 1:
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return err("Attestation has too many aggregation bits")
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else:
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break # Found the one we needed
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if onesCount < 1:
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return err("Attestation has too few aggregation bits")
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ok()
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func check_attestation_subnet(
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epochRef: EpochRef, attestation: Attestation,
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topicCommitteeIndex: uint64): Result[void, cstring] =
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let
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expectedSubnet =
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compute_subnet_for_attestation(
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get_committee_count_per_slot(epochRef),
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attestation.data.slot, attestation.data.index.CommitteeIndex)
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if expectedSubnet != topicCommitteeIndex:
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return err("Attestation's committee index not for the correct subnet")
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/p2p-interface.md#beacon_attestation_subnet_id
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proc validateAttestation*(
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pool: var AttestationPool,
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attestation: Attestation, wallTime: BeaconTime,
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topicCommitteeIndex: uint64): Result[HashSet[ValidatorIndex], cstring] =
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? check_attestation_slot_target(attestation.data) # Not in spec - ignore
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# attestation.data.slot is within the last ATTESTATION_PROPAGATION_SLOT_RANGE
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# slots (within a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance) -- i.e.
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# attestation.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot
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# >= attestation.data.slot (a client MAY queue future attestations for\
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# processing at the appropriate slot).
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? check_propagation_slot_range(attestation.data, wallTime) # [IGNORE]
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# The attestation is unaggregated -- that is, it has exactly one
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# participating validator (len([bit for bit in attestation.aggregation_bits
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# if bit == 0b1]) == 1).
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? check_aggregation_count(attestation, singular = true) # [REJECT]
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# The block being voted for (attestation.data.beacon_block_root) has been seen
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# (via both gossip and non-gossip sources) (a client MAY queue aggregates for
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# processing once block is retrieved).
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# The block being voted for (attestation.data.beacon_block_root) passes
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# validation.
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? check_attestation_beacon_block(pool, attestation) # [IGNORE/REJECT]
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# The attestation is the first valid attestation received for the
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# participating validator for the slot, attestation.data.slot.
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let maybeAttestationsSeen = getAttestationsForSlot(pool, attestation.data.slot)
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if maybeAttestationsSeen.isSome:
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for attestationEntry in maybeAttestationsSeen.get.attestations:
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if attestation.data != attestationEntry.data:
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continue
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# Attestations might be aggregated eagerly or lazily; allow for both.
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for validation in attestationEntry.validations:
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if attestation.aggregation_bits.isSubsetOf(validation.aggregation_bits):
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return err("Attestation already exists at slot") # [IGNORE]
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let tgtBlck = pool.chainDag.getRef(attestation.data.target.root)
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if tgtBlck.isNil:
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pool.quarantine.addMissing(attestation.data.target.root)
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return err("Attestation target block unknown")
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# The following rule follows implicitly from that we clear out any
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# unviable blocks from the chain dag:
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#
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# The current finalized_checkpoint is an ancestor of the block defined by
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# attestation.data.beacon_block_root -- i.e. get_ancestor(store,
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# attestation.data.beacon_block_root,
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# compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)) ==
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# store.finalized_checkpoint.root
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let epochRef = pool.chainDag.getEpochRef(
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tgtBlck, attestation.data.target.epoch)
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# [REJECT] The attestation is for the correct subnet -- i.e.
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# compute_subnet_for_attestation(committees_per_slot,
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# attestation.data.slot, attestation.data.index) == subnet_id, where
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# committees_per_slot = get_committee_count_per_slot(state,
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# attestation.data.target.epoch), which may be pre-computed along with the
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# committee information for the signature check.
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? check_attestation_subnet(epochRef, attestation, topicCommitteeIndex)
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let
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fork = pool.chainDag.headState.data.data.fork
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genesis_validators_root =
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pool.chainDag.headState.data.data.genesis_validators_root
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attesting_indices = get_attesting_indices(
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epochRef, attestation.data, attestation.aggregation_bits)
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# The signature of attestation is valid.
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? is_valid_indexed_attestation(
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fork, genesis_validators_root, epochRef, attesting_indices, attestation, {})
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ok(attesting_indices)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/p2p-interface.md#beacon_aggregate_and_proof
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proc validateAggregate*(
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pool: var AttestationPool,
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signedAggregateAndProof: SignedAggregateAndProof,
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wallTime: BeaconTime): Result[HashSet[ValidatorIndex], cstring] =
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let
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aggregate_and_proof = signedAggregateAndProof.message
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aggregate = aggregate_and_proof.aggregate
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? check_attestation_slot_target(aggregate.data) # Not in spec - ignore
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# [IGNORE] aggregate.data.slot is within the last
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# ATTESTATION_PROPAGATION_SLOT_RANGE slots (with a
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# MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance) -- i.e. aggregate.data.slot +
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# ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate.data.slot
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? check_propagation_slot_range(aggregate.data, wallTime) # [IGNORE]
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# [IGNORE] The valid aggregate attestation defined by
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# hash_tree_root(aggregate) has not already been seen (via aggregate gossip,
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# within a verified block, or through the creation of an equivalent aggregate
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# locally).
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#
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# This is [IGNORE] and already checked by attestation pool when aggregate is
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# added.
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# [IGNORE] The aggregate is the first valid aggregate received for the
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# aggregator with index aggregate_and_proof.aggregator_index for the epoch
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# aggregate.data.target.epoch.
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#
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# This is [IGNORE] and already effectively checked by attestation pool upon
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# attempting to resolve attestations.
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# [REJECT] The attestation has participants -- that is,
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# len(get_attesting_indices(state, aggregate.data, aggregate.aggregation_bits)) >= 1.
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#
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# get_attesting_indices() is:
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# committee = get_beacon_committee(state, data.slot, data.index)
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# return set(index for i, index in enumerate(committee) if bits[i])
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#
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# the attestation doesn't have participants is iff either:
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# (1) the aggregation bits are all 0; or
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# (2) the non-zero aggregation bits don't overlap with extant committee
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# members, i.e. they counts don't match.
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# But (2) would reflect an invalid aggregation in other ways, so reject it
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# either way.
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? check_aggregation_count(aggregate, singular = false)
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# [REJECT] The block being voted for (aggregate.data.beacon_block_root)
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# passes validation.
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? check_attestation_beacon_block(pool, aggregate)
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# [REJECT] aggregate_and_proof.selection_proof selects the validator as an
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# aggregator for the slot -- i.e. is_aggregator(state, aggregate.data.slot,
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# aggregate.data.index, aggregate_and_proof.selection_proof) returns True.
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let tgtBlck = pool.chainDag.getRef(aggregate.data.target.root)
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if tgtBlck.isNil:
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pool.quarantine.addMissing(aggregate.data.target.root)
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return err("Aggregate target block unknown")
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let epochRef = pool.chainDag.getEpochRef(tgtBlck, aggregate.data.target.epoch)
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if not is_aggregator(
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epochRef, aggregate.data.slot, aggregate.data.index.CommitteeIndex,
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aggregate_and_proof.selection_proof):
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return err("Incorrect aggregator")
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# [REJECT] The aggregator's validator index is within the committee -- i.e.
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# aggregate_and_proof.aggregator_index in get_beacon_committee(state,
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# aggregate.data.slot, aggregate.data.index).
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if aggregate_and_proof.aggregator_index.ValidatorIndex notin
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get_beacon_committee(
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epochRef, aggregate.data.slot, aggregate.data.index.CommitteeIndex):
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return err("Aggregator's validator index not in committee")
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# [REJECT] The aggregate_and_proof.selection_proof is a valid signature of the
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# aggregate.data.slot by the validator with index
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# aggregate_and_proof.aggregator_index.
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# get_slot_signature(state, aggregate.data.slot, privkey)
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if aggregate_and_proof.aggregator_index >= epochRef.validator_keys.lenu64:
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return err("Invalid aggregator_index")
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let
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fork = pool.chainDag.headState.data.data.fork
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genesis_validators_root =
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pool.chainDag.headState.data.data.genesis_validators_root
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if not verify_slot_signature(
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fork, genesis_validators_root, aggregate.data.slot,
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epochRef.validator_keys[aggregate_and_proof.aggregator_index],
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aggregate_and_proof.selection_proof):
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return err("Selection_proof signature verification failed")
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# [REJECT] The aggregator signature, signed_aggregate_and_proof.signature, is valid.
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if not verify_aggregate_and_proof_signature(
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fork, genesis_validators_root, aggregate_and_proof,
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epochRef.validator_keys[aggregate_and_proof.aggregator_index],
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signed_aggregate_and_proof.signature):
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return err("signed_aggregate_and_proof signature verification failed")
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let attesting_indices = get_attesting_indices(
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epochRef, aggregate.data, aggregate.aggregation_bits)
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# [REJECT] The signature of aggregate is valid.
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? is_valid_indexed_attestation(
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fork, genesis_validators_root, epochRef, attesting_indices, aggregate, {})
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# The following rule follows implicitly from that we clear out any
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# unviable blocks from the chain dag:
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#
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# The current finalized_checkpoint is an ancestor of the block defined by
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# aggregate.data.beacon_block_root -- i.e. get_ancestor(store,
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# aggregate.data.beacon_block_root,
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# compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)) ==
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# store.finalized_checkpoint.root
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ok(attesting_indices)
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