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Only allow sync committee period calculation at period boundaries

This commit is contained in:
Alex Stokes 2021-05-11 11:18:03 -07:00
parent 5074fcad17
commit 859a7d743e
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GPG Key ID: 99B3D88FD6C55A69
6 changed files with 18 additions and 56 deletions
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12
specs/altair/beacon-chain.md
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@ -276,16 +276,14 @@ def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
"""
Return the sequence of sync committee indices (which may include duplicate indices)
for a given ``state`` and ``epoch``.
Note: This function is not stable during a sync committee period as
a validator's effective balance may change enough to affect the sampling.
for a given ``state`` and ``epoch`` at a sync committee period boundary.
"""
assert epoch % EPOCHS_PER_SYNC_COMMITTEE_PERIOD == 0
MAX_RANDOM_BYTE = 2**8 - 1
base_epoch = Epoch((max(epoch // EPOCHS_PER_SYNC_COMMITTEE_PERIOD, 1) - 1) * EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
active_validator_indices = get_active_validator_indices(state, base_epoch)
active_validator_indices = get_active_validator_indices(state, epoch)
active_validator_count = uint64(len(active_validator_indices))
seed = get_seed(state, base_epoch, DOMAIN_SYNC_COMMITTEE)
seed = get_seed(state, epoch, DOMAIN_SYNC_COMMITTEE)
i = 0
sync_committee_indices: List[ValidatorIndex] = []
while len(sync_committee_indices) < SYNC_COMMITTEE_SIZE:

6
specs/altair/fork.md
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@ -81,7 +81,9 @@ def upgrade_to_altair(pre: phase0.BeaconState) -> BeaconState:
inactivity_scores=[uint64(0) for _ in range(len(pre.validators))],
)
# Fill in sync committees
post.current_sync_committee = get_sync_committee(post, get_current_epoch(post))
post.next_sync_committee = get_sync_committee(post, get_current_epoch(post) + EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
current_period = epoch // EPOCHS_PER_SYNC_COMMITTEE_PERIOD
base_epoch = current_period * EPOCHS_PER_SYNC_COMMITTEE_PERIOD
post.current_sync_committee = get_sync_committee(post, base_epoch)
post.next_sync_committee = get_sync_committee(post, base_epoch + EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
return post
```

41
tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_committee.py
View File

@ -7,7 +7,6 @@ from eth2spec.test.helpers.block_processing import run_block_processing_to
from eth2spec.test.helpers.state import (
state_transition_and_sign_block,
transition_to,
next_epoch,
)
from eth2spec.test.helpers.constants import (
MAINNET, MINIMAL,
@ -367,43 +366,3 @@ def test_valid_signature_future_committee(spec, state):
)
yield from run_sync_committee_processing(spec, state, block)
@with_altair_and_later
@spec_state_test
def test_sync_committee_is_only_computed_at_epoch_boundary(spec, state):
"""
Sync committees can only be computed at sync committee period boundaries.
Ensure a client respects the committee in the state (assumed to be derived
in the correct way).
"""
current_epoch = spec.get_current_epoch(state)
# use a "synthetic" committee to simulate the situation
# where ``spec.get_sync_committee`` at the sync committee
# period epoch boundary would have diverged some epochs into the
# period; ``aggregate_pubkey`` is not relevant to this test
pubkeys = []
committee_indices = []
i = 0
active_validator_count = len(spec.get_active_validator_indices(state, current_epoch))
while len(pubkeys) < spec.SYNC_COMMITTEE_SIZE:
v = state.validators[i % active_validator_count]
if spec.is_active_validator(v, current_epoch):
pubkeys.append(v.pubkey)
committee_indices.append(i)
i += 1
synthetic_committee = spec.SyncCommittee(pubkeys=pubkeys, aggregate_pubkey=spec.BLSPubkey())
state.current_sync_committee = synthetic_committee
assert spec.EPOCHS_PER_SYNC_COMMITTEE_PERIOD > 3
for _ in range(3):
next_epoch(spec, state)
committee = get_committee_indices(spec, state)
assert committee != committee_indices
committee_size = len(committee_indices)
committee_bits = [True] * committee_size
yield from run_successful_sync_committee_test(spec, state, committee_indices, committee_bits)

3
tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_sync_committee_updates.py
View File

@ -39,8 +39,7 @@ def run_sync_committees_progress_test(spec, state):
# Can compute the third committee having computed final balances in the last epoch
# of this `EPOCHS_PER_SYNC_COMMITTEE_PERIOD`
current_epoch = spec.get_current_epoch(state)
third_sync_committee = spec.get_sync_committee(state, current_epoch + 2 * spec.EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
third_sync_committee = spec.get_sync_committee(state, (next_period + 1) * spec.EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
assert state.current_sync_committee == second_sync_committee
assert state.next_sync_committee == third_sync_committee

3
tests/core/pyspec/eth2spec/test/altair/sanity/test_blocks.py
View File

@ -18,7 +18,8 @@ from eth2spec.test.context import (
def run_sync_committee_sanity_test(spec, state, fraction_full=1.0):
committee = spec.get_sync_committee_indices(state, spec.get_current_epoch(state))
all_pubkeys = [v.pubkey for v in state.validators]
committee = [all_pubkeys.index(pubkey) for pubkey in state.current_sync_committee.pubkeys]
participants = random.sample(committee, int(len(committee) * fraction_full))
yield 'pre', state

9
tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
View File

@ -46,7 +46,8 @@ def test_process_light_client_update_not_updated(spec, state):
body_root=signed_block.message.body.hash_tree_root(),
)
# Sync committee signing the header
committee = spec.get_sync_committee_indices(state, spec.get_current_epoch(state))
all_pubkeys = [v.pubkey for v in state.validators]
committee = [all_pubkeys.index(pubkey) for pubkey in state.current_sync_committee.pubkeys]
sync_committee_bits = [True] * len(committee)
sync_committee_signature = compute_aggregate_sync_committee_signature(
spec,
@ -111,7 +112,8 @@ def test_process_light_client_update_timeout(spec, state):
)
# Sync committee signing the finalized_block_header
committee = spec.get_sync_committee_indices(state, spec.get_current_epoch(state))
all_pubkeys = [v.pubkey for v in state.validators]
committee = [all_pubkeys.index(pubkey) for pubkey in state.current_sync_committee.pubkeys]
sync_committee_bits = [True] * len(committee)
sync_committee_signature = compute_aggregate_sync_committee_signature(
spec,
@ -190,7 +192,8 @@ def test_process_light_client_update_finality_updated(spec, state):
)
# Sync committee signing the finalized_block_header
committee = spec.get_sync_committee_indices(state, spec.get_current_epoch(state))
all_pubkeys = [v.pubkey for v in state.validators]
committee = [all_pubkeys.index(pubkey) for pubkey in state.current_sync_committee.pubkeys]
sync_committee_bits = [True] * len(committee)
sync_committee_signature = compute_aggregate_sync_committee_signature(
spec,