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add strict mode to light client processor (#3894) 

The light client sync protocol employs heuristics to ensure it does not
become stuck during non-finality or low sync committee participation.
These can enable use cases that prefer availability of recent data
over security. For our syncing use case, though, security is preferred.
An option is added to light client processor to configure this tradeoff.
This commit is contained in:
Etan Kissling 2022-07-21 11:16:10 +02:00 committed by GitHub
parent 24d8401054
commit 735c1df62f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 271 additions and 175 deletions
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22
AllTests-mainnet.md
View File

@ -287,14 +287,20 @@ OK: 9/9 Fail: 0/9 Skip: 0/9
OK: 3/3 Fail: 0/3 Skip: 0/3
## Light client processor [Preset: mainnet]
```diff
+ Duplicate bootstrap [Preset: mainnet] OK
+ Invalid bootstrap [Preset: mainnet] OK
+ Missing bootstrap (finality update) [Preset: mainnet] OK
+ Missing bootstrap (optimistic update) [Preset: mainnet] OK
+ Missing bootstrap (update) [Preset: mainnet] OK
+ Sync [Preset: mainnet] OK
+ Duplicate bootstrap (Optimistic) [Preset: mainnet] OK
+ Duplicate bootstrap (Strict) [Preset: mainnet] OK
+ Invalid bootstrap (Optimistic) [Preset: mainnet] OK
+ Invalid bootstrap (Strict) [Preset: mainnet] OK
+ Missing bootstrap (finality update) (Optimistic) [Preset: mainnet] OK
+ Missing bootstrap (finality update) (Strict) [Preset: mainnet] OK
+ Missing bootstrap (optimistic update) (Optimistic) [Preset: mainnet] OK
+ Missing bootstrap (optimistic update) (Strict) [Preset: mainnet] OK
+ Missing bootstrap (update) (Optimistic) [Preset: mainnet] OK
+ Missing bootstrap (update) (Strict) [Preset: mainnet] OK
+ Sync (Optimistic) [Preset: mainnet] OK
+ Sync (Strict) [Preset: mainnet] OK
```
OK: 6/6 Fail: 0/6 Skip: 0/6
OK: 12/12 Fail: 0/12 Skip: 0/12
## ListKeys requests [Preset: mainnet]
```diff
+ Correct token provided [Preset: mainnet] OK
@ -580,4 +586,4 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
OK: 9/9 Fail: 0/9 Skip: 0/9
---TOTAL---
OK: 321/326 Fail: 0/326 Skip: 5/326
OK: 327/332 Fail: 0/332 Skip: 5/332

4
beacon_chain/beacon_node_light_client.nim
View File

@ -42,8 +42,8 @@ proc initLightClient*(
config.safeSlotsToImportOptimistically)
lightClient = createLightClient(
node.network, rng, config, cfg,
forkDigests, getBeaconTime, genesis_validators_root)
node.network, rng, config, cfg, forkDigests, getBeaconTime,
genesis_validators_root, LightClientFinalizationMode.Strict)
if config.lightClientEnable.get:
proc shouldSyncOptimistically(slot: Slot): bool =

68
beacon_chain/gossip_processing/light_client_processor.nim
View File

@ -33,6 +33,33 @@ type
VoidCallback* =
proc() {.gcsafe, raises: [Defect].}
LightClientFinalizationMode* {.pure.} = enum
Strict
## Only finalize light client data that:
## - has been signed by a supermajority (2/3) of the sync committee
## - has a valid finality proof
##
## Optimizes for security, but may become stuck if there is any of:
## - non-finality for an entire sync committee period
## - low sync committee participation for an entire sync committee period
## Such periods need to be covered by an out-of-band syncing mechanism.
##
## Note that a compromised supermajority of the sync committee is able to
## sign arbitrary light client data, even after being slashed. The light
## client cannot validate the slashing status of sync committee members.
## Likewise, voluntarily exited validators may sign bad light client data
## for the sync committee periods in which they used to be selected.
Optimistic
## Attempt to finalize light client data not satisfying strict conditions
## if there is no progress for an extended period of time and if there are
## repeated messages indicating that it is the best available data on the
## network for the affected time period.
##
## Optimizes for availability of recent data, but may end up on incorrect
## forks if run in a hostile network environment (no honest peers), or if
## the low sync committee participation is being exploited by bad actors.
LightClientProcessor* = object
## This manages the processing of received light client objects
##
@ -48,13 +75,6 @@ type
##
## are then verified and added to:
## - `LightClientStore`
##
## The processor will also attempt to force-update the light client state
## if no update seems to be available on the network, that is both signed by
## a supermajority of sync committee members and also improves finality.
## This logic is triggered if there is no progress for an extended period
## of time, and there are repeated messages indicating that this is the best
## available data on the network during that time period.
# Config
# ----------------------------------------------------------------
@ -72,9 +92,13 @@ type
cfg: RuntimeConfig
genesis_validators_root: Eth2Digest
lastProgressTick: BeaconTime # Moment when last update made progress
lastDuplicateTick: BeaconTime # Moment when last duplicate update received
numDuplicatesSinceProgress: int # Number of duplicates since last progress
case finalizationMode: LightClientFinalizationMode
of LightClientFinalizationMode.Strict:
discard
of LightClientFinalizationMode.Optimistic:
lastProgressTick: BeaconTime # Moment when last update made progress
lastDuplicateTick: BeaconTime # Moment when last duplicate update received
numDuplicatesSinceProgress: int # Number of duplicates since last progress
latestFinalityUpdate: altair.LightClientOptimisticUpdate
@ -94,6 +118,7 @@ proc new*(
dumpDirInvalid, dumpDirIncoming: string,
cfg: RuntimeConfig,
genesis_validators_root: Eth2Digest,
finalizationMode: LightClientFinalizationMode,
store: ref Option[LightClientStore],
getBeaconTime: GetBeaconTimeFn,
getTrustedBlockRoot: GetTrustedBlockRootCallback,
@ -112,8 +137,8 @@ proc new*(
onFinalizedHeader: onFinalizedHeader,
onOptimisticHeader: onOptimisticHeader,
cfg: cfg,
genesis_validators_root: genesis_validators_root
)
genesis_validators_root: genesis_validators_root,
finalizationMode: finalizationMode)
# Storage
# ------------------------------------------------------------------------------
@ -146,6 +171,7 @@ proc tryForceUpdate(
store = self.store
if store[].isSome:
doAssert self.finalizationMode == LightClientFinalizationMode.Optimistic
case store[].get.try_light_client_store_force_update(wallSlot)
of NoUpdate:
discard
@ -192,11 +218,12 @@ proc processObject(
if res.isErr:
when obj is altair.LightClientUpdate:
if store[].isSome and store[].get.best_valid_update.isSome:
# `best_valid_update` gets set when no supermajority / improved finality
# is available. In that case, we will wait for a better update that once
# again fulfills those conditions. If none is received within reasonable
# time, the light client store is force-updated to `best_valid_update`.
if self.finalizationMode == LightClientFinalizationMode.Optimistic and
store[].isSome and store[].get.best_valid_update.isSome:
# `best_valid_update` gets set when no supermajority / finality proof
# is available. In that case, we will wait for a better update.
# If none is made available within reasonable time, the light client
# is force-updated using the best known data to ensure sync progress.
case res.error
of BlockError.Duplicate:
if wallTime >= self.lastDuplicateTick + duplicateRateLimit:
@ -215,9 +242,10 @@ proc processObject(
return res
when obj is altair.LightClientBootstrap | altair.LightClientUpdate:
self.lastProgressTick = wallTime
self.lastDuplicateTick = wallTime + duplicateCountDelay
self.numDuplicatesSinceProgress = 0
if self.finalizationMode == LightClientFinalizationMode.Optimistic:
self.lastProgressTick = wallTime
self.lastDuplicateTick = wallTime + duplicateCountDelay
self.numDuplicatesSinceProgress = 0
res

17
beacon_chain/light_client.nim
View File

@ -20,7 +20,7 @@ import
./sync/light_client_manager,
"."/[beacon_clock, conf_light_client]
export eth2_network, conf_light_client
export LightClientFinalizationMode, eth2_network, conf_light_client
logScope: topics = "lightcl"
@ -60,7 +60,8 @@ proc createLightClient(
cfg: RuntimeConfig,
forkDigests: ref ForkDigests,
getBeaconTime: GetBeaconTimeFn,
genesis_validators_root: Eth2Digest
genesis_validators_root: Eth2Digest,
finalizationMode: LightClientFinalizationMode
): LightClient =
let lightClient = LightClient(
network: network,
@ -85,7 +86,7 @@ proc createLightClient(
lightClient.processor = LightClientProcessor.new(
dumpEnabled, dumpDirInvalid, dumpDirIncoming,
cfg, genesis_validators_root,
cfg, genesis_validators_root, finalizationMode,
lightClient.store, getBeaconTime, getTrustedBlockRoot,
onStoreInitialized, onFinalizedHeader, onOptimisticHeader)
@ -141,12 +142,13 @@ proc createLightClient*(
cfg: RuntimeConfig,
forkDigests: ref ForkDigests,
getBeaconTime: GetBeaconTimeFn,
genesis_validators_root: Eth2Digest
genesis_validators_root: Eth2Digest,
finalizationMode: LightClientFinalizationMode
): LightClient =
createLightClient(
network, rng,
config.dumpEnabled, config.dumpDirInvalid, config.dumpDirIncoming,
cfg, forkDigests, getBeaconTime, genesis_validators_root)
cfg, forkDigests, getBeaconTime, genesis_validators_root, finalizationMode)
proc createLightClient*(
network: Eth2Node,
@ -155,12 +157,13 @@ proc createLightClient*(
cfg: RuntimeConfig,
forkDigests: ref ForkDigests,
getBeaconTime: GetBeaconTimeFn,
genesis_validators_root: Eth2Digest
genesis_validators_root: Eth2Digest,
finalizationMode: LightClientFinalizationMode
): LightClient =
createLightClient(
network, rng,
dumpEnabled = false, dumpDirInvalid = ".", dumpDirIncoming = ".",
cfg, forkDigests, getBeaconTime, genesis_validators_root)
cfg, forkDigests, getBeaconTime, genesis_validators_root, finalizationMode)
proc start*(lightClient: LightClient) =
notice "Starting light client",

4
beacon_chain/nimbus_light_client.nim
View File

@ -95,8 +95,8 @@ programMain:
config.safeSlotsToImportOptimistically)
lightClient = createLightClient(
network, rng, config, cfg,
forkDigests, getBeaconTime, genesis_validators_root)
network, rng, config, cfg, forkDigests, getBeaconTime,
genesis_validators_root, LightClientFinalizationMode.Optimistic)
info "Listening to incoming network requests"
network.initBeaconSync(cfg, forkDigests, genesisBlockRoot, getBeaconTime)

331
tests/test_light_client_processor.nim
View File

@ -79,166 +79,225 @@ suite "Light client processor" & preset():
0.82
addBlocks(numFilledEpochsPerPeriod * SLOTS_PER_EPOCH, syncCommitteeRatio)
setup:
var time = chronos.seconds(0)
proc getBeaconTime(): BeaconTime =
BeaconTime(ns_since_genesis: time.nanoseconds)
func setTimeToSlot(slot: Slot) =
time = chronos.seconds((slot * SECONDS_PER_SLOT).int64)
for finalizationMode in LightClientFinalizationMode:
let testNameSuffix = " (" & $finalizationMode & ")" & preset()
var numOnStoreInitializedCalls = 0
proc onStoreInitialized() = inc numOnStoreInitializedCalls
setup:
var time = chronos.seconds(0)
proc getBeaconTime(): BeaconTime =
BeaconTime(ns_since_genesis: time.nanoseconds)
func setTimeToSlot(slot: Slot) =
time = chronos.seconds((slot * SECONDS_PER_SLOT).int64)
let store = (ref Option[LightClientStore])()
var
processor = LightClientProcessor.new(
false, "", "", cfg, genesis_validators_root,
store, getBeaconTime, getTrustedBlockRoot, onStoreInitialized)
res: Result[bool, BlockError]
var numOnStoreInitializedCalls = 0
func onStoreInitialized() = inc numOnStoreInitializedCalls
test "Sync" & preset():
let bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isOk
numOnStoreInitializedCalls == 1
let store = (ref Option[LightClientStore])()
var
processor = LightClientProcessor.new(
false, "", "", cfg, genesis_validators_root, finalizationMode,
store, getBeaconTime, getTrustedBlockRoot, onStoreInitialized)
res: Result[bool, BlockError]
for period in lowPeriod .. lastPeriodWithSupermajority:
let update = dag.getLightClientUpdateForPeriod(period)
check update.isSome
setTimeToSlot(update.get.signature_slot)
test "Sync" & testNameSuffix:
let bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isOk
store[].isSome
if update.get.finalized_header.slot > bootstrap.get.header.slot:
store[].get.finalized_header == update.get.finalized_header
else:
store[].get.finalized_header == bootstrap.get.header
store[].get.optimistic_header == update.get.attested_header
numOnStoreInitializedCalls == 1
for period in lastPeriodWithSupermajority + 1 .. highPeriod:
let update = dag.getLightClientUpdateForPeriod(period)
check update.isSome
setTimeToSlot(update.get.signature_slot)
for i in 0 ..< 2:
# Reduce stack size by making this a `proc`
proc applyPeriodWithSupermajority(period: SyncCommitteePeriod) =
let update = dag.getLightClientUpdateForPeriod(period)
check update.isSome
setTimeToSlot(update.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
check:
res.isOk
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
if update.get.finalized_header.slot > bootstrap.get.header.slot:
store[].get.finalized_header == update.get.finalized_header
else:
store[].get.finalized_header == bootstrap.get.header
store[].get.optimistic_header == update.get.attested_header
proc applyDuplicate() = # Reduce stack size by making this a `proc`
for period in lowPeriod .. lastPeriodWithSupermajority:
applyPeriodWithSupermajority(period)
# Reduce stack size by making this a `proc`
proc applyPeriodWithoutSupermajority(period: SyncCommitteePeriod) =
let update = dag.getLightClientUpdateForPeriod(period)
check update.isSome
setTimeToSlot(update.get.signature_slot)
for i in 0 ..< 2:
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
check:
res.isErr
res.error == BlockError.Duplicate
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
if finalizationMode == LightClientFinalizationMode.Optimistic or
period == lastPeriodWithSupermajority + 1:
if finalizationMode == LightClientFinalizationMode.Optimistic or
i == 0:
check:
res.isOk
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
else:
check:
res.isErr
res.error == BlockError.Duplicate
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
else:
check:
res.isErr
res.error == BlockError.MissingParent
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get != update.get
proc applyDuplicate() = # Reduce stack size by making this a `proc`
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
if finalizationMode == LightClientFinalizationMode.Optimistic or
period == lastPeriodWithSupermajority + 1:
check:
res.isErr
res.error == BlockError.Duplicate
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
else:
check:
res.isErr
res.error == BlockError.MissingParent
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get != update.get
applyDuplicate()
time += chronos.minutes(15)
for _ in 0 ..< 150:
applyDuplicate()
time += chronos.seconds(5)
time += chronos.minutes(15)
time += chronos.minutes(15)
for _ in 0 ..< 150:
applyDuplicate()
time += chronos.seconds(5)
time += chronos.minutes(15)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
if finalizationMode == LightClientFinalizationMode.Optimistic:
check:
res.isErr
res.error == BlockError.Duplicate
store[].isSome
store[].get.best_valid_update.isNone
if store[].get.finalized_header == update.get.attested_header:
break
check store[].get.finalized_header == update.get.finalized_header
elif period == lastPeriodWithSupermajority + 1:
check:
res.isErr
res.error == BlockError.Duplicate
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get == update.get
else:
check:
res.isErr
res.error == BlockError.MissingParent
store[].isSome
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get != update.get
if finalizationMode == LightClientFinalizationMode.Optimistic:
check store[].get.finalized_header == update.get.attested_header
else:
check store[].get.finalized_header != update.get.attested_header
for period in lastPeriodWithSupermajority + 1 .. highPeriod:
applyPeriodWithoutSupermajority(period)
let
previousFinalized = store[].get.finalized_header
finalityUpdate = dag.getLightClientFinalityUpdate()
check finalityUpdate.isSome
setTimeToSlot(finalityUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), finalityUpdate.get)
if res.isOk:
check:
res.isErr
res.error == BlockError.Duplicate
finalizationMode == LightClientFinalizationMode.Optimistic
store[].isSome
store[].get.best_valid_update.isNone
if store[].get.finalized_header == update.get.attested_header:
break
check store[].get.finalized_header == update.get.finalized_header
check store[].get.finalized_header == update.get.attested_header
store[].get.finalized_header == previousFinalized
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get.matches(finalityUpdate.get)
store[].get.optimistic_header == finalityUpdate.get.attested_header
elif finalizationMode == LightClientFinalizationMode.Optimistic:
check res.error == BlockError.Duplicate
else:
check res.error == BlockError.MissingParent
check numOnStoreInitializedCalls == 1
let
previousFinalized = store[].get.finalized_header
finalityUpdate = dag.getLightClientFinalityUpdate()
check finalityUpdate.isSome
setTimeToSlot(finalityUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), finalityUpdate.get)
if res.isOk:
test "Invalid bootstrap" & testNameSuffix:
var bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
bootstrap.get.header.slot.inc()
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
store[].isSome
store[].get.finalized_header == previousFinalized
store[].get.best_valid_update.isSome
store[].get.best_valid_update.get.matches(finalityUpdate.get)
store[].get.optimistic_header == finalityUpdate.get.attested_header
else:
check res.error == BlockError.Duplicate
check numOnStoreInitializedCalls == 1
res.isErr
res.error == BlockError.Invalid
numOnStoreInitializedCalls == 0
test "Invalid bootstrap" & preset():
var bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
bootstrap.get.header.slot.inc()
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isErr
res.error == BlockError.Invalid
numOnStoreInitializedCalls == 0
test "Duplicate bootstrap" & testNameSuffix:
let bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isOk
numOnStoreInitializedCalls == 1
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isErr
res.error == BlockError.Duplicate
numOnStoreInitializedCalls == 1
test "Duplicate bootstrap" & preset():
let bootstrap = dag.getLightClientBootstrap(trustedBlockRoot)
check bootstrap.isOk
setTimeToSlot(bootstrap.get.header.slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isOk
numOnStoreInitializedCalls == 1
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), bootstrap.get)
check:
res.isErr
res.error == BlockError.Duplicate
numOnStoreInitializedCalls == 1
test "Missing bootstrap (update)" & testNameSuffix:
let update = dag.getLightClientUpdateForPeriod(lowPeriod)
check update.isSome
setTimeToSlot(update.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0
test "Missing bootstrap (update)" & preset():
let update = dag.getLightClientUpdateForPeriod(lowPeriod)
check update.isSome
setTimeToSlot(update.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), update.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0
test "Missing bootstrap (finality update)" & testNameSuffix:
let finalityUpdate = dag.getLightClientFinalityUpdate()
check finalityUpdate.isSome
setTimeToSlot(finalityUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), finalityUpdate.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0
test "Missing bootstrap (finality update)" & preset():
let finalityUpdate = dag.getLightClientFinalityUpdate()
check finalityUpdate.isSome
setTimeToSlot(finalityUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), finalityUpdate.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0
test "Missing bootstrap (optimistic update)" & preset():
let optimisticUpdate = dag.getLightClientOptimisticUpdate()
check optimisticUpdate.isSome
setTimeToSlot(optimisticUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), optimisticUpdate.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0
test "Missing bootstrap (optimistic update)" & testNameSuffix:
let optimisticUpdate = dag.getLightClientOptimisticUpdate()
check optimisticUpdate.isSome
setTimeToSlot(optimisticUpdate.get.signature_slot)
res = processor[].storeObject(
MsgSource.gossip, getBeaconTime(), optimisticUpdate.get)
check:
res.isErr
res.error == BlockError.MissingParent
numOnStoreInitializedCalls == 0