279 lines
12 KiB
Nim
279 lines
12 KiB
Nim
# 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.
|
|
|
|
# State transition, as described in
|
|
# https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beacon-chain-state-transition-function
|
|
#
|
|
# The entry point is `state_transition` which is at the bottom of the file!
|
|
#
|
|
# General notes about the code:
|
|
# * Weird styling - the sections taken from the spec use python styling while
|
|
# the others use NEP-1 - helps grepping identifiers in spec
|
|
# * When updating the code, add TODO sections to mark where there are clear
|
|
# improvements to be made - other than that, keep things similar to spec unless
|
|
# motivated by security or performance considerations
|
|
|
|
{.push raises: [Defect].}
|
|
|
|
import
|
|
tables,
|
|
chronicles,
|
|
stew/results,
|
|
../extras, ../ssz/merkleization, metrics,
|
|
datatypes, crypto, digest, helpers, signatures, validator,
|
|
state_transition_block, state_transition_epoch,
|
|
../../nbench/bench_lab
|
|
|
|
# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#additional-metrics
|
|
declareGauge beacon_current_validators, """Number of status="pending|active|exited|withdrawable" validators in current epoch""" # On epoch transition
|
|
declareGauge beacon_previous_validators, """Number of status="pending|active|exited|withdrawable" validators in previous epoch""" # On epoch transition
|
|
|
|
func get_epoch_validator_count(state: BeaconState): int64 {.nbench.} =
|
|
# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#additional-metrics
|
|
#
|
|
# This O(n) loop doesn't add to the algorithmic complexity of the epoch
|
|
# transition -- registry update already does this. It is not great, but
|
|
# isn't new, either. If profiling shows issues some of this can be loop
|
|
# fusion'ed.
|
|
for index, validator in state.validators:
|
|
# These work primarily for the `beacon_current_validators` metric defined
|
|
# as 'Number of status="pending|active|exited|withdrawable" validators in
|
|
# current epoch'. This is, in principle, equivalent to checking whether a
|
|
# validator's either at less than MAX_EFFECTIVE_BALANCE, or has withdrawn
|
|
# already because withdrawable_epoch has passed, which more precisely has
|
|
# intuitive meaning of all-the-current-relevant-validators. So, check for
|
|
# not-(either (not-even-pending) or withdrawn). That is validators change
|
|
# from not-even-pending to pending to active to exited to withdrawable to
|
|
# withdrawn, and this avoids bugs on potential edge cases and off-by-1's.
|
|
if (validator.activation_epoch != FAR_FUTURE_EPOCH or
|
|
validator.effective_balance > MAX_EFFECTIVE_BALANCE) and
|
|
validator.withdrawable_epoch > get_current_epoch(state):
|
|
result += 1
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function
|
|
proc verify_block_signature*(
|
|
state: BeaconState, signed_block: SomeSignedBeaconBlock): bool {.nbench.} =
|
|
let
|
|
proposer_index = signed_block.message.proposer_index
|
|
if proposer_index >= state.validators.lenu64:
|
|
notice "Invalid proposer index in block",
|
|
blck = shortLog(signed_block.message)
|
|
return false
|
|
|
|
if not verify_block_signature(
|
|
state.fork, state.genesis_validators_root, signed_block.message.slot,
|
|
signed_block.message, state.validators[proposer_index].pubkey,
|
|
signed_block.signature):
|
|
notice "Block: signature verification failed",
|
|
blck = shortLog(signedBlock)
|
|
return false
|
|
|
|
true
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function
|
|
proc verifyStateRoot(state: BeaconState, blck: BeaconBlock): bool =
|
|
# This is inlined in state_transition(...) in spec.
|
|
let state_root = hash_tree_root(state)
|
|
if state_root != blck.state_root:
|
|
notice "Block: root verification failed",
|
|
block_state_root = shortLog(blck.state_root), state_root = shortLog(state_root)
|
|
false
|
|
else:
|
|
true
|
|
|
|
proc verifyStateRoot(state: BeaconState, blck: TrustedBeaconBlock): bool =
|
|
# This is inlined in state_transition(...) in spec.
|
|
true
|
|
|
|
type
|
|
RollbackProc* = proc(v: var BeaconState) {.gcsafe, raises: [Defect].}
|
|
|
|
proc noRollback*(state: var BeaconState) =
|
|
trace "Skipping rollback of broken state"
|
|
|
|
type
|
|
RollbackHashedProc* = proc(state: var HashedBeaconState) {.gcsafe.}
|
|
|
|
# Hashed-state transition functions
|
|
# ---------------------------------------------------------------
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function
|
|
func process_slot*(state: var HashedBeaconState) {.nbench.} =
|
|
# Cache state root
|
|
let previous_slot_state_root = state.root
|
|
state.data.state_roots[state.data.slot mod SLOTS_PER_HISTORICAL_ROOT] =
|
|
previous_slot_state_root
|
|
|
|
# Cache latest block header state root
|
|
if state.data.latest_block_header.state_root == ZERO_HASH:
|
|
state.data.latest_block_header.state_root = previous_slot_state_root
|
|
|
|
# Cache block root
|
|
state.data.block_roots[state.data.slot mod SLOTS_PER_HISTORICAL_ROOT] =
|
|
hash_tree_root(state.data.latest_block_header)
|
|
|
|
func clear_epoch_from_cache(cache: var StateCache, epoch: Epoch) =
|
|
cache.shuffled_active_validator_indices.del epoch
|
|
let
|
|
start_slot = epoch.compute_start_slot_at_epoch
|
|
end_slot = (epoch + 1).compute_start_slot_at_epoch
|
|
|
|
for i in start_slot ..< end_slot:
|
|
cache.beacon_proposer_indices.del i
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function
|
|
proc advance_slot(
|
|
state: var HashedBeaconState, updateFlags: UpdateFlags,
|
|
epochCache: var StateCache) {.nbench.} =
|
|
process_slot(state)
|
|
|
|
let is_epoch_transition = (state.data.slot + 1).isEpoch
|
|
if is_epoch_transition:
|
|
# Note: Genesis epoch = 0, no need to test if before Genesis
|
|
beacon_previous_validators.set(get_epoch_validator_count(state.data))
|
|
process_epoch(state.data, updateFlags, epochCache)
|
|
clear_epoch_from_cache(
|
|
epochCache, (state.data.slot + 1).compute_epoch_at_slot)
|
|
|
|
state.data.slot += 1
|
|
if is_epoch_transition:
|
|
beacon_current_validators.set(get_epoch_validator_count(state.data))
|
|
|
|
# The root must be updated on every slot update, or the next `process_slot`
|
|
# will be incorrect
|
|
state.root = hash_tree_root(state.data)
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function
|
|
proc process_slots*(state: var HashedBeaconState, slot: Slot,
|
|
cache: var StateCache, updateFlags: UpdateFlags = {}): bool {.nbench.} =
|
|
if not (state.data.slot < slot):
|
|
if slotProcessed notin updateFlags or state.data.slot != slot:
|
|
notice(
|
|
"Unusual request for a slot in the past",
|
|
state_root = shortLog(state.root),
|
|
current_slot = state.data.slot,
|
|
target_slot = slot
|
|
)
|
|
return false
|
|
|
|
# Catch up to the target slot
|
|
while state.data.slot < slot:
|
|
advance_slot(state, updateFlags, cache)
|
|
|
|
true
|
|
|
|
proc noRollback*(state: var HashedBeaconState) =
|
|
trace "Skipping rollback of broken state"
|
|
|
|
proc state_transition*(
|
|
preset: RuntimePreset,
|
|
state: var HashedBeaconState, signedBlock: SomeSignedBeaconBlock,
|
|
stateCache: var StateCache,
|
|
flags: UpdateFlags, rollback: RollbackHashedProc): bool {.nbench.} =
|
|
## Time in the beacon chain moves by slots. Every time (haha.) that happens,
|
|
## we will update the beacon state. Normally, the state updates will be driven
|
|
## by the contents of a new block, but it may happen that the block goes
|
|
## missing - the state updates happen regardless.
|
|
##
|
|
## The flags are used to specify that certain validations should be skipped
|
|
## for the new block. This is done during block proposal, to create a state
|
|
## whose hash can be included in the new block.
|
|
##
|
|
## `rollback` is called if the transition fails and the given state has been
|
|
## partially changed. If a temporary state was given to `state_transition`,
|
|
## it is safe to use `noRollback` and leave it broken, else the state
|
|
## object should be rolled back to a consistent state. If the transition fails
|
|
## before the state has been updated, `rollback` will not be called.
|
|
doAssert not rollback.isNil, "use noRollback if it's ok to mess up state"
|
|
|
|
# This only fails if it hasn't changed stateCache, so it can't create a false
|
|
# not-followed future history in stateCache.
|
|
if not process_slots(state, signedBlock.message.slot, stateCache, flags):
|
|
rollback(state)
|
|
return false
|
|
|
|
# Block updates - these happen when there's a new block being suggested
|
|
# by the block proposer. Every actor in the network will update its state
|
|
# according to the contents of this block - but first they will validate
|
|
# that the block is sane.
|
|
if skipBLSValidation in flags or
|
|
verify_block_signature(state.data, signedBlock):
|
|
|
|
trace "state_transition: processing block, signature passed",
|
|
signature = shortLog(signedBlock.signature),
|
|
blockRoot = shortLog(signedBlock.root)
|
|
if process_block(preset, state.data, signedBlock.message, flags, stateCache):
|
|
if skipStateRootValidation in flags or verifyStateRoot(state.data, signedBlock.message):
|
|
# State root is what it should be - we're done!
|
|
|
|
# TODO when creating a new block, state_root is not yet set.. comparing
|
|
# with zero hash here is a bit fragile however, but this whole thing
|
|
# should go away with proper hash caching
|
|
# TODO shouldn't ever have to recalculate; verifyStateRoot() does it
|
|
state.root =
|
|
if signedBlock.message.state_root == Eth2Digest(): hash_tree_root(state.data)
|
|
else: signedBlock.message.state_root
|
|
|
|
return true
|
|
|
|
# Block processing failed, roll back changes
|
|
rollback(state)
|
|
|
|
false
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/validator.md#preparing-for-a-beaconblock
|
|
proc makeBeaconBlock*(
|
|
preset: RuntimePreset,
|
|
state: var HashedBeaconState,
|
|
proposer_index: ValidatorIndex,
|
|
parent_root: Eth2Digest,
|
|
randao_reveal: ValidatorSig,
|
|
eth1_data: Eth1Data,
|
|
graffiti: GraffitiBytes,
|
|
attestations: seq[Attestation],
|
|
deposits: seq[Deposit],
|
|
proposerSlashings: seq[ProposerSlashing],
|
|
attesterSlashings: seq[AttesterSlashing],
|
|
voluntaryExits: seq[SignedVoluntaryExit],
|
|
rollback: RollbackHashedProc,
|
|
cache: var StateCache): Option[BeaconBlock] =
|
|
## Create a block for the given state. The last block applied to it must be
|
|
## the one identified by parent_root and process_slots must be called up to
|
|
## the slot for which a block is to be created.
|
|
|
|
# To create a block, we'll first apply a partial block to the state, skipping
|
|
# some validations.
|
|
|
|
var blck = BeaconBlock(
|
|
slot: state.data.slot,
|
|
proposer_index: proposer_index.uint64,
|
|
parent_root: parent_root,
|
|
body: BeaconBlockBody(
|
|
randao_reveal: randao_reveal,
|
|
eth1_data: eth1data,
|
|
graffiti: graffiti,
|
|
proposer_slashings: List[ProposerSlashing, Limit MAX_PROPOSER_SLASHINGS](
|
|
proposerSlashings),
|
|
attester_slashings: List[AttesterSlashing, Limit MAX_ATTESTER_SLASHINGS](
|
|
attesterSlashings),
|
|
attestations: List[Attestation, Limit MAX_ATTESTATIONS](attestations),
|
|
deposits: List[Deposit, Limit MAX_DEPOSITS](deposits),
|
|
voluntary_exits:
|
|
List[SignedVoluntaryExit, Limit MAX_VOLUNTARY_EXITS](voluntaryExits)))
|
|
|
|
let ok = process_block(preset, state.data, blck, {skipBlsValidation}, cache)
|
|
|
|
if not ok:
|
|
warn "Unable to apply new block to state", blck = shortLog(blck)
|
|
rollback(state)
|
|
return
|
|
|
|
state.root = hash_tree_root(state.data)
|
|
blck.state_root = state.root
|
|
|
|
some(blck)
|