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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
# Standard library
std/[os, osproc, random, sequtils, streams, tables],
# Nimble packages
stew/[objects], stew/shims/macros,
chronos, metrics, json_rpc/[rpcserver, jsonmarshal],
chronicles,
json_serialization/std/[options, sets, net], serialization/errors,
eth/db/kvstore,
eth/[keys, async_utils], eth/p2p/discoveryv5/[protocol, enr],
# Local modules
spec/[datatypes, digest, crypto, helpers, network, signatures],
spec/state_transition,
conf, time, validator_pool,
attestation_pool, exit_pool, block_pools/[spec_cache, chain_dag, clearance],
eth2_network, keystore_management, beacon_node_common, beacon_node_types,
eth1_monitor, version, ssz/merkleization,
attestation_aggregation, sync_manager, sszdump,
validator_slashing_protection
# Metrics for tracking attestation and beacon block loss
const delayBuckets = [-Inf, -4.0, -2.0, -1.0, -0.5, -0.1, -0.05,
0.05, 0.1, 0.5, 1.0, 2.0, 4.0, 8.0, Inf]
declareCounter beacon_attestations_sent,
"Number of beacon chain attestations sent by this peer"
declareHistogram beacon_attestation_sent_delay,
"Time(s) between slot start and attestation sent moment",
buckets = delayBuckets
declareCounter beacon_blocks_proposed,
"Number of beacon chain blocks sent by this peer"
logScope: topics = "beacval"
proc checkValidatorInRegistry(state: BeaconState,
pubKey: ValidatorPubKey) =
let idx = state.validators.asSeq.findIt(it.pubKey == pubKey)
if idx == -1:
# We allow adding a validator even if its key is not in the state registry:
# it might be that the deposit for this validator has not yet been processed
warn "Validator not in registry (yet?)", pubKey
proc addLocalValidator*(node: BeaconNode,
state: BeaconState,
privKey: ValidatorPrivKey) =
let pubKey = privKey.toPubKey()
state.checkValidatorInRegistry(pubKey)
node.attachedValidators.addLocalValidator(pubKey, privKey)
proc addLocalValidators*(node: BeaconNode) =
for validatorKey in node.config.validatorKeys:
node.addLocalValidator node.chainDag.headState.data.data, validatorKey
proc addRemoteValidators*(node: BeaconNode) =
# load all the validators from the child process - loop until `end`
var line = newStringOfCap(120).TaintedString
while line != "end" and running(node.vcProcess):
if node.vcProcess.outputStream.readLine(line) and line != "end":
let key = ValidatorPubKey.fromHex(line).get().initPubKey()
node.chainDag.headState.data.data.checkValidatorInRegistry(key)
let v = AttachedValidator(pubKey: key,
kind: ValidatorKind.remote,
connection: ValidatorConnection(
inStream: node.vcProcess.inputStream,
outStream: node.vcProcess.outputStream,
pubKeyStr: $key))
node.attachedValidators.addRemoteValidator(key, v)
proc getAttachedValidator*(node: BeaconNode,
pubkey: ValidatorPubKey): AttachedValidator =
node.attachedValidators.getValidator(pubkey)
proc getAttachedValidator*(node: BeaconNode,
state: BeaconState,
idx: ValidatorIndex): AttachedValidator =
if idx < state.validators.len.ValidatorIndex:
node.getAttachedValidator(state.validators[idx].pubkey)
else:
warn "Validator index out of bounds",
idx, stateSlot = state.slot, validators = state.validators.len
nil
proc getAttachedValidator*(node: BeaconNode,
epochRef: EpochRef,
idx: ValidatorIndex): AttachedValidator =
if idx < epochRef.validator_keys.len.ValidatorIndex:
node.getAttachedValidator(epochRef.validator_keys[idx])
else:
warn "Validator index out of bounds",
idx, epoch = epochRef.epoch, validators = epochRef.validator_keys.len
nil
proc isSynced*(node: BeaconNode, head: BlockRef): bool =
## TODO This function is here as a placeholder for some better heurestics to
## determine if we're in sync and should be producing blocks and
## attestations. Generally, the problem is that slot time keeps advancing
## even when there are no blocks being produced, so there's no way to
## distinguish validators geniunely going missing from the node not being
## well connected (during a network split or an internet outage for
## example). It would generally be correct to simply keep running as if
## we were the only legit node left alive, but then we run into issues:
## with enough many empty slots, the validator pool is emptied leading
## to empty committees and lots of empty slot processing that will be
## thrown away as soon as we're synced again.
let
# The slot we should be at, according to the clock
beaconTime = node.beaconClock.now()
wallSlot = beaconTime.toSlot()
# TODO: MaxEmptySlotCount should likely involve the weak subjectivity period.
# TODO if everyone follows this logic, the network will not recover from a
# halt: nobody will be producing blocks because everone expects someone
# else to do it
if wallSlot.afterGenesis and head.slot + MaxEmptySlotCount < wallSlot.slot:
false
else:
true
proc sendAttestation*(
node: BeaconNode, attestation: Attestation, num_active_validators: uint64) =
node.network.broadcast(
getAttestationTopic(node.forkDigest, attestation, num_active_validators),
attestation)
beacon_attestations_sent.inc()
proc sendAttestation*(node: BeaconNode, attestation: Attestation) =
# For the validator API, which doesn't supply num_active_validators.
let attestationBlck =
node.chainDag.getRef(attestation.data.beacon_block_root)
if attestationBlck.isNil:
debug "Attempt to send attestation without corresponding block"
return
node.sendAttestation(
attestation,
count_active_validators(
node.chainDag.getEpochRef(attestationBlck, attestation.data.target.epoch)))
proc createAndSendAttestation(node: BeaconNode,
fork: Fork,
genesis_validators_root: Eth2Digest,
validator: AttachedValidator,
attestationData: AttestationData,
committeeLen: int,
indexInCommittee: int,
num_active_validators: uint64) {.async.} =
var attestation = await validator.produceAndSignAttestation(
attestationData, committeeLen, indexInCommittee, fork,
genesis_validators_root)
node.sendAttestation(attestation, num_active_validators)
if node.config.dumpEnabled:
dump(node.config.dumpDirOutgoing, attestation.data, validator.pubKey)
let wallTime = node.beaconClock.now()
let deadline = attestationData.slot.toBeaconTime() +
seconds(int(SECONDS_PER_SLOT div 3))
let (delayStr, delayMillis) =
if wallTime < deadline:
("-" & $(deadline - wallTime), -toFloatSeconds(deadline - wallTime))
else:
($(wallTime - deadline), toFloatSeconds(wallTime - deadline))
notice "Attestation sent", attestation = shortLog(attestation),
validator = shortLog(validator), delay = delayStr,
indexInCommittee = indexInCommittee
beacon_attestation_sent_delay.observe(delayMillis)
proc makeBeaconBlockForHeadAndSlot*(node: BeaconNode,
randao_reveal: ValidatorSig,
validator_index: ValidatorIndex,
graffiti: GraffitiBytes,
head: BlockRef,
slot: Slot): Option[BeaconBlock] =
# Advance state to the slot that we're proposing for
node.chainDag.withState(node.chainDag.tmpState, head.atSlot(slot)):
let (eth1data, deposits) =
if node.eth1Monitor.isNil:
(state.eth1_data, newSeq[Deposit]())
else:
let finalizedEth1Data = node.chainDag.getFinalizedEpochRef().eth1_data
node.eth1Monitor.getBlockProposalData(state, finalizedEth1Data)
let
poolPtr = unsafeAddr node.chainDag # safe because restore is short-lived
func restore(v: var HashedBeaconState) =
# TODO address this ugly workaround - there should probably be a
# `state_transition` that takes a `StateData` instead and updates
# the block as well
doAssert v.addr == addr poolPtr.tmpState.data
assign(poolPtr.tmpState, poolPtr.headState)
makeBeaconBlock(
node.config.runtimePreset,
hashedState,
validator_index,
head.root,
randao_reveal,
eth1data,
graffiti,
node.attestationPool[].getAttestationsForBlock(state, cache),
deposits,
node.exitPool[].getProposerSlashingsForBlock(),
node.exitPool[].getAttesterSlashingsForBlock(),
node.exitPool[].getVoluntaryExitsForBlock(),
restore,
cache)
proc proposeSignedBlock*(node: BeaconNode,
head: BlockRef,
validator: AttachedValidator,
newBlock: SignedBeaconBlock): Future[BlockRef] {.async.} =
let newBlockRef = node.chainDag.addRawBlock(node.quarantine,
newBlock) do (
blckRef: BlockRef, signedBlock: SignedBeaconBlock,
epochRef: EpochRef, state: HashedBeaconState):
# Callback add to fork choice if valid
node.attestationPool[].addForkChoice(
epochRef, blckRef, signedBlock.message,
node.beaconClock.now().slotOrZero())
if newBlockRef.isErr:
warn "Unable to add proposed block to block pool",
newBlock = shortLog(newBlock.message),
blockRoot = shortLog(newBlock.root)
return head
notice "Block proposed",
blck = shortLog(newBlock.message),
blockRoot = shortLog(newBlockRef[].root),
validator = shortLog(validator)
if node.config.dumpEnabled:
dump(node.config.dumpDirOutgoing, newBlock)
node.network.broadcast(node.topicBeaconBlocks, newBlock)
beacon_blocks_proposed.inc()
return newBlockRef[]
proc proposeBlock(node: BeaconNode,
validator: AttachedValidator,
validator_index: ValidatorIndex,
head: BlockRef,
slot: Slot): Future[BlockRef] {.async.} =
if head.slot >= slot:
# We should normally not have a head newer than the slot we're proposing for
# but this can happen if block proposal is delayed
warn "Skipping proposal, have newer head already",
headSlot = shortLog(head.slot),
headBlockRoot = shortLog(head.root),
slot = shortLog(slot)
return head
let notSlashable = node.attachedValidators
.slashingProtection
.checkSlashableBlockProposal(validator.pubkey, slot)
if notSlashable.isErr:
warn "Slashing protection activated",
validator = validator.pubkey,
slot = slot,
existingProposal = notSlashable.error
return head
let
fork = node.chainDag.headState.data.data.fork
genesis_validators_root =
node.chainDag.headState.data.data.genesis_validators_root
let
randao = await validator.genRandaoReveal(
fork, genesis_validators_root, slot)
message = makeBeaconBlockForHeadAndSlot(
node, randao, validator_index, node.graffitiBytes, head, slot)
if not message.isSome():
return head # already logged elsewhere!
var
newBlock = SignedBeaconBlock(
message: message.get()
)
newBlock.root = hash_tree_root(newBlock.message)
# TODO: recomputed in block proposal
let signing_root = compute_block_root(
fork, genesis_validators_root, slot, newBlock.root)
node.attachedValidators
.slashingProtection
.registerBlock(validator.pubkey, slot, signing_root)
newBlock.signature = await validator.signBlockProposal(
fork, genesis_validators_root, slot, newBlock.root)
return await node.proposeSignedBlock(head, validator, newBlock)
proc handleAttestations(node: BeaconNode, head: BlockRef, slot: Slot) =
## Perform all attestations that the validators attached to this node should
## perform during the given slot
if slot + SLOTS_PER_EPOCH < head.slot:
# The latest block we know about is a lot newer than the slot we're being
# asked to attest to - this makes it unlikely that it will be included
# at all.
# TODO the oldest attestations allowed are those that are older than the
# finalized epoch.. also, it seems that posting very old attestations
# is risky from a slashing perspective. More work is needed here.
warn "Skipping attestation, head is too recent",
headSlot = shortLog(head.slot),
slot = shortLog(slot)
return
let attestationHead = head.atSlot(slot)
if head != attestationHead.blck:
# In rare cases, such as when we're busy syncing or just slow, we'll be
# attesting to a past state - we must then recreate the world as it looked
# like back then
notice "Attesting to a state in the past, falling behind?",
headSlot = shortLog(head.slot),
attestationHeadSlot = shortLog(attestationHead.slot),
attestationSlot = shortLog(slot)
trace "Checking attestations",
attestationHeadRoot = shortLog(attestationHead.blck.root),
attestationSlot = shortLog(slot)
# Collect data to send before node.stateCache grows stale
var attestations: seq[tuple[
data: AttestationData, committeeLen, indexInCommittee: int,
validator: AttachedValidator]]
# We need to run attestations exactly for the slot that we're attesting to.
# In case blocks went missing, this means advancing past the latest block
# using empty slots as fillers.
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/validator.md#validator-assignments
let
epochRef = node.chainDag.getEpochRef(
attestationHead.blck, slot.compute_epoch_at_slot())
committees_per_slot =
get_committee_count_per_slot(epochRef)
num_active_validators = count_active_validators(epochRef)
fork = node.chainDag.headState.data.data.fork
genesis_validators_root =
node.chainDag.headState.data.data.genesis_validators_root
for committee_index in 0'u64..<committees_per_slot:
let committee = get_beacon_committee(
epochRef, slot, committee_index.CommitteeIndex)
for index_in_committee, validatorIdx in committee:
let validator = node.getAttachedValidator(epochRef, validatorIdx)
if validator != nil:
let ad = makeAttestationData(
epochRef, attestationHead, committee_index.CommitteeIndex)
attestations.add((ad, committee.len, index_in_committee, validator))
for a in attestations:
let notSlashable = node.attachedValidators
.slashingProtection
.checkSlashableAttestation(
a.validator.pubkey,
a.data.source.epoch,
a.data.target.epoch)
if notSlashable.isOk():
# TODO signing_root is recomputed in produceAndSignAttestation/signAttestation just after
let signing_root = compute_attestation_root(
fork, genesis_validators_root, a.data)
node.attachedValidators
.slashingProtection
.registerAttestation(
a.validator.pubkey,
a.data.source.epoch,
a.data.target.epoch,
signing_root
)
traceAsyncErrors createAndSendAttestation(
node, fork, genesis_validators_root, a.validator, a.data,
a.committeeLen, a.indexInCommittee, num_active_validators)
else:
warn "Slashing protection activated for attestation",
validator = a.validator.pubkey,
badVoteDetails = $notSlashable.error
proc handleProposal(node: BeaconNode, head: BlockRef, slot: Slot):
Future[BlockRef] {.async.} =
## Perform the proposal for the given slot, iff we have a validator attached
## that is supposed to do so, given the shuffling in head
# TODO here we advance the state to the new slot, but later we'll be
# proposing for it - basically, we're selecting proposer based on an
# empty slot
let proposer = node.chainDag.getProposer(head, slot)
if proposer.isNone():
return head
let validator =
node.attachedValidators.getValidator(proposer.get()[1])
if validator != nil:
return await proposeBlock(node, validator, proposer.get()[0], head, slot)
debug "Expecting block proposal",
headRoot = shortLog(head.root),
slot = shortLog(slot),
proposer_index = proposer.get()[0],
proposer = shortLog(proposer.get()[1].initPubKey())
return head
proc broadcastAggregatedAttestations(
node: BeaconNode, aggregationHead: BlockRef, aggregationSlot: Slot) {.async.} =
# The index is via a
# locally attested validator. Unlike in handleAttestations(...) there's a
# single one at most per slot (because that's how aggregation attestation
# works), so the machinery that has to handle looping across, basically a
# set of locally attached validators is in principle not necessary, but a
# way to organize this. Then the private key for that validator should be
# the corresponding one -- whatver they are, they match.
let
epochRef = node.chainDag.getEpochRef(aggregationHead, aggregationSlot.epoch)
fork = node.chainDag.headState.data.data.fork
genesis_validators_root =
node.chainDag.headState.data.data.genesis_validators_root
committees_per_slot = get_committee_count_per_slot(epochRef)
var
slotSigs: seq[Future[ValidatorSig]] = @[]
slotSigsData: seq[tuple[committee_index: uint64,
validator_idx: ValidatorIndex,
v: AttachedValidator]] = @[]
for committee_index in 0'u64..<committees_per_slot:
let committee = get_beacon_committee(
epochRef, aggregationSlot, committee_index.CommitteeIndex)
for index_in_committee, validatorIdx in committee:
let validator = node.getAttachedValidator(epochRef, validatorIdx)
if validator != nil:
# the validator index and private key pair.
slotSigs.add getSlotSig(validator, fork,
genesis_validators_root, aggregationSlot)
slotSigsData.add (committee_index, validatorIdx, validator)
await allFutures(slotSigs)
for curr in zip(slotSigsData, slotSigs):
let aggregateAndProof =
aggregate_attestations(node.attestationPool[], epochRef, aggregationSlot,
curr[0].committee_index.CommitteeIndex,
curr[0].validator_idx,
curr[1].read)
# Don't broadcast when, e.g., this node isn't aggregator
# TODO verify there is only one isSome() with test.
if aggregateAndProof.isSome:
let sig = await signAggregateAndProof(curr[0].v,
aggregateAndProof.get, fork, genesis_validators_root)
var signedAP = SignedAggregateAndProof(
message: aggregateAndProof.get,
signature: sig)
node.network.broadcast(node.topicAggregateAndProofs, signedAP)
notice "Aggregated attestation sent",
attestation = shortLog(signedAP.message.aggregate),
validator = shortLog(curr[0].v)
proc getSlotTimingEntropy(): int64 =
# Ensure SECONDS_PER_SLOT / ATTESTATION_PRODUCTION_DIVISOR >
# SECONDS_PER_SLOT / ATTESTATION_ENTROPY_DIVISOR, which will
# enure that the second condition can't go negative.
static: doAssert ATTESTATION_ENTROPY_DIVISOR > ATTESTATION_PRODUCTION_DIVISOR
# For each `slot`, a validator must generate a uniform random variable
# `slot_timing_entropy` between `(-SECONDS_PER_SLOT /
# ATTESTATION_ENTROPY_DIVISOR, SECONDS_PER_SLOT /
# ATTESTATION_ENTROPY_DIVISOR)` with millisecond resolution and using local
# entropy.
#
# Per issue discussion "validators served by the same beacon node can have
# the same attestation production time, i.e., they can share the source of
# the entropy and the actual slot_timing_entropy value."
const
slot_timing_entropy_upper_bound =
SECONDS_PER_SLOT.int64 * 1000 div ATTESTATION_ENTROPY_DIVISOR
slot_timing_entropy_lower_bound = 0-slot_timing_entropy_upper_bound
rand(range[(slot_timing_entropy_lower_bound + 1) ..
(slot_timing_entropy_upper_bound - 1)])
proc handleValidatorDuties*(node: BeaconNode, lastSlot, slot: Slot) {.async.} =
## Perform validator duties - create blocks, vote and aggregate existing votes
if node.attachedValidators.count == 0:
# Nothing to do because we have no validator attached
return
# The chainDag head might be updated by sync while we're working due to the
# await calls, thus we use a local variable to keep the logic straight here
var head = node.chainDag.head
if not node.isSynced(head):
notice "Syncing in progress; skipping validator duties for now",
slot, headSlot = head.slot
return
var curSlot = lastSlot + 1
# Start by checking if there's work we should have done in the past that we
# can still meaningfully do
while curSlot < slot:
notice "Catching up on validator duties",
curSlot = shortLog(curSlot),
lastSlot = shortLog(lastSlot),
slot = shortLog(slot)
# For every slot we're catching up, we'll propose then send
# attestations - head should normally be advancing along the same branch
# in this case
head = await handleProposal(node, head, curSlot)
# For each slot we missed, we need to send out attestations - if we were
# proposing during this time, we'll use the newly proposed head, else just
# keep reusing the same - the attestation that goes out will actually
# rewind the state to what it looked like at the time of that slot
handleAttestations(node, head, curSlot)
curSlot += 1
head = await handleProposal(node, head, slot)
# Fix timing attack: https://github.com/ethereum/eth2.0-specs/pull/2101
# A validator must create and broadcast the `attestation` to the associated
# attestation subnet when the earlier one of the following two events occurs:
#
# - The validator has received a valid block from the expected block
# proposer for the assigned `slot`. In this case, the validator must set a
# timer for `abs(slot_timing_entropy)`. The end of this timer will be the
# trigger for attestation production.
#
# - `SECONDS_PER_SLOT / ATTESTATION_PRODUCTION_DIVISOR +
# slot_timing_entropy` seconds have elapsed since the start of the `slot`
# (using the `slot_timing_entropy` generated for this slot)
# We've been doing lots of work up until now which took time. Normally, we
# send out attestations at the slot thirds-point, so we go back to the clock
# to see how much time we need to wait.
# TODO the beacon clock might jump here also. It's probably easier to complete
# the work for the whole slot using a monotonic clock instead, then deal
# with any clock discrepancies once only, at the start of slot timer
# processing..
let slotTimingEntropy = getSlotTimingEntropy()
template sleepToSlotOffsetWithHeadUpdate(extra: chronos.Duration, msg: static string) =
let waitTime = node.beaconClock.fromNow(slot.toBeaconTime(extra))
if waitTime.inFuture:
discard await withTimeout(
node.processor[].blockReceivedDuringSlot, waitTime.offset)
# Might have gotten a valid beacon block this slot, which triggers the
# first case, in which we wait for another abs(slotTimingEntropy).
if node.processor[].blockReceivedDuringSlot.finished:
await sleepAsync(
milliseconds(max(slotTimingEntropy, 0 - slotTimingEntropy)))
# Time passed - we might need to select a new head in that case
node.processor[].updateHead(slot)
head = node.chainDag.head
sleepToSlotOffsetWithHeadUpdate(
milliseconds(SECONDS_PER_SLOT.int64 * 1000 div ATTESTATION_PRODUCTION_DIVISOR +
slotTimingEntropy),
"Waiting to send attestations")
handleAttestations(node, head, slot)
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/validator.md#broadcast-aggregate
# If the validator is selected to aggregate (is_aggregator), then they
# broadcast their best aggregate as a SignedAggregateAndProof to the global
# aggregate channel (beacon_aggregate_and_proof) two-thirds of the way
# through the slot-that is, SECONDS_PER_SLOT * 2 / 3 seconds after the start
# of slot.
if slot > 2:
sleepToSlotOffsetWithHeadUpdate(
seconds(int64(SECONDS_PER_SLOT * 2) div 3),
"Waiting to aggregate attestations")
const TRAILING_DISTANCE = 1
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/p2p-interface.md#configuration
static:
doAssert TRAILING_DISTANCE <= ATTESTATION_PROPAGATION_SLOT_RANGE
let
aggregationSlot = slot - TRAILING_DISTANCE
aggregationHead = get_ancestor(head, aggregationSlot)
await broadcastAggregatedAttestations(node, aggregationHead, aggregationSlot)
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