weak subjecitivity checks (#3391)

* rectifying wssync check and state initialization

* lint

* checking db state for also wss period check

* Update packages/cli/src/cmds/beacon/initBeaconState.ts

* lint - prettier

Co-authored-by: Cayman <caymannava@gmail.com>

packages/beacon-state-transition/src/allForks/util/weakSubjectivity.ts

@@ -10,7 +10,14 @@ import {ssz} from "@chainsafe/lodestar-types";
 import {Checkpoint} from "@chainsafe/lodestar-types/phase0";
 import {toHexString} from "@chainsafe/ssz";
 import {CachedBeaconState} from ".";
-import {getActiveValidatorIndices, getCurrentEpoch, computeEpochAtSlot, ZERO_HASH, getChurnLimit} from "../..";
+import {
+  getActiveValidatorIndices,
+  getCurrentEpoch,
+  computeEpochAtSlot,
+  ZERO_HASH,
+  getChurnLimit,
+  getCurrentSlot,
+} from "../..";
 
 export const ETH_TO_GWEI = 10 ** 9;
 const SAFETY_DECAY = BigInt(10);
@@ -109,7 +116,6 @@ export function getLatestBlockRoot(config: IChainForkConfig, state: allForks.Bea
 
 export function isWithinWeakSubjectivityPeriod(
   config: IBeaconConfig,
-  store: allForks.BeaconState,
   wsState: allForks.BeaconState,
   wsCheckpoint: Checkpoint
 ): boolean {
@@ -124,6 +130,6 @@ export function isWithinWeakSubjectivityPeriod(
     throw new Error(`Epochs do not match.  expected=${wsCheckpoint.epoch}, actual=${wsStateEpoch}`);
   }
   const wsPeriod = computeWeakSubjectivityPeriod(config, wsState);
-  const currentEpoch = getCurrentEpoch(store);
-  return currentEpoch <= wsStateEpoch + wsPeriod;
+  const clockEpoch = computeEpochAtSlot(getCurrentSlot(config, wsState.genesisTime));
+  return clockEpoch <= wsStateEpoch + wsPeriod;
 }

packages/cli/src/cmds/beacon/initBeaconState.ts

@@ -1,5 +1,5 @@
 import {AbortSignal} from "@chainsafe/abort-controller";
-
+import {ssz} from "@chainsafe/lodestar-types";
 import {TreeBacked} from "@chainsafe/ssz";
 import {createIBeaconConfig, IBeaconConfig, IChainForkConfig} from "@chainsafe/lodestar-config";
 import {fromHex, ILogger} from "@chainsafe/lodestar-utils";
@@ -39,10 +39,32 @@ async function initAndVerifyWeakSubjectivityState(
   wsState: TreeBacked<allForks.BeaconState>,
   wsCheckpoint: Checkpoint
 ): Promise<TreeBacked<allForks.BeaconState>> {
-  if (!allForks.isWithinWeakSubjectivityPeriod(config, store, wsState, wsCheckpoint)) {
+  // Check if the store's state and wsState are compatible
+  if (
+    store.genesisTime !== wsState.genesisTime ||
+    !ssz.Root.equals(store.genesisValidatorsRoot, wsState.genesisValidatorsRoot)
+  ) {
+    throw new Error(
+      "Db state and checkpoint state are not compatible, either clear the db or verify your checkpoint source"
+    );
+  }
+
+  // Pick the state which is ahead as an anchor to initialize the beacon chain
+  let anchorState = wsState;
+  let anchorCheckpoint = wsCheckpoint;
+  if (store.slot > wsState.slot) {
+    anchorState = store;
+    anchorCheckpoint = getCheckpointFromState(config, store);
+    logger.verbose(
+      "Db state is ahead of the provided checkpoint state, using the db state to initialize the beacon chain"
+    );
+  }
+
+  if (!allForks.isWithinWeakSubjectivityPeriod(config, anchorState, anchorCheckpoint)) {
     throw new Error("Fetched weak subjectivity checkpoint not within weak subjectivity period.");
   }
-  return await initStateFromAnchorState(config, db, logger, wsState);
+
+  return await initStateFromAnchorState(config, db, logger, anchorState);
 }
 
 /**