track state period in light client state

parachain/modules/consensus/sync-committee/primitives/src/types.rs

@@ -94,6 +94,8 @@ pub struct VerifierState {
     pub current_sync_committee: SyncCommittee<SYNC_COMMITTEE_SIZE>,
     /// Committee for the next sync period
     pub next_sync_committee: SyncCommittee<SYNC_COMMITTEE_SIZE>,
+    /// state_period
+    pub state_period: u64,
 }
 
 /// Finalized header proof

parachain/modules/consensus/sync-committee/primitives/src/util.rs

@@ -13,7 +13,7 @@ use ssz_rs::prelude::*;
 
 /// Returns true if sync committee update is required
 pub fn should_have_sync_committee_update(state_period: u64, signature_period: u64) -> bool {
-    state_period != signature_period
+    signature_period == state_period + 1
 }
 
 /// Return the sync committee period at the given ``epoch``

parachain/modules/consensus/sync-committee/prover/src/lib.rs

@@ -229,7 +229,7 @@ impl SyncCommitteeProver {
     /// we use `head`
     pub async fn fetch_light_client_update(
         &self,
-        client_state: VerifierState,
+        mut client_state: VerifierState,
         finality_checkpoint: Checkpoint,
         latest_block_id: Option<&str>,
         debug_target: &str,
@@ -251,8 +251,7 @@ impl SyncCommitteeProver {
         };
         let mut block = self.fetch_block(&get_block_id(latest_root)).await?;
         let min_signatures = (2 * SYNC_COMMITTEE_SIZE) / 3;
-        let state_period =
-            compute_sync_committee_period_at_slot(client_state.finalized_header.slot);
+        let state_period = client_state.state_period;
         loop {
             // Some checks on the epoch finalized by the signature block
             let parent_root = block.parent_root;
@@ -298,8 +297,13 @@ impl SyncCommitteeProver {
         let execution_payload_proof = prove_execution_payload(&mut finalized_state)?;
 
         let signature_period = compute_sync_committee_period_at_slot(block.slot);
+        let client_state_next_sync_committee_root =
+            client_state.next_sync_committee.hash_tree_root()?;
+        let attested_state_current_sync_committee_root =
+            attested_state.current_sync_committee.hash_tree_root()?;
         let sync_committee_update =
-            if should_have_sync_committee_update(state_period, signature_period) {
+            // We must make sure we switch the sync comittee only when the finalized header has changed sync committees
+            if should_have_sync_committee_update(state_period, signature_period) && client_state_next_sync_committee_root == attested_state_current_sync_committee_root {
                 let sync_committee_proof = prove_sync_committee_update(&mut attested_state)?;
                 Some(SyncCommitteeUpdate {
                     next_sync_committee: attested_state.next_sync_committee,

parachain/modules/consensus/sync-committee/prover/src/test.rs

@@ -261,6 +261,7 @@ async fn test_client_sync() {
         latest_finalized_epoch: compute_epoch_at_slot(block_header.slot),
         current_sync_committee: state.current_sync_committee,
         next_sync_committee: state.next_sync_committee,
+        state_period: 810,
     };
 
     let mut next_period = start_period + 1;
@@ -280,7 +281,6 @@ async fn test_client_sync() {
 #[cfg(test)]
 #[allow(non_snake_case)]
 #[tokio::test]
-#[ignore]
 async fn test_sync_committee_hand_offs() {
     let sync_committee_prover = setup_prover();
     let state_period = 805;
@@ -299,6 +299,7 @@ async fn test_sync_committee_hand_offs() {
         latest_finalized_epoch: compute_epoch_at_slot(block_header.slot),
         current_sync_committee: state.current_sync_committee,
         next_sync_committee: state.next_sync_committee,
+        state_period: 805,
     };
 
     // Verify an update from state_period + 1
@@ -326,7 +327,7 @@ async fn test_sync_committee_hand_offs() {
         .unwrap();
     assert!(update.sync_committee_update.is_some());
     client_state = verify_sync_committee_attestation(client_state, update).unwrap();
-
+    assert_eq!(client_state.state_period, state_period + 1);
     // Verify block in the current state_period
     let latest_block_id = {
         let slot = ((signature_period * EPOCHS_PER_SYNC_COMMITTEE_PERIOD) * SLOTS_PER_EPOCH) +
@@ -384,6 +385,7 @@ async fn test_prover() {
         latest_finalized_epoch: compute_epoch_at_slot(block_header.slot),
         current_sync_committee: state.current_sync_committee,
         next_sync_committee: state.next_sync_committee,
+        state_period: compute_sync_committee_period_at_slot(block_header.slot),
     };
 
     let mut count = 0;
@@ -504,7 +506,6 @@ pub struct EventResponse {
 
 fn setup_prover() -> SyncCommitteeProver {
     dotenv::dotenv().ok();
-    let consensus_url =
-        std::env::var("CONSENSUS_NODE_URL").unwrap_or("http://localhost:3500".to_string());
+    let consensus_url = std::env::var("BEACON_URL").unwrap_or("http://localhost:3500".to_string());
     SyncCommitteeProver::new(consensus_url)
 }

parachain/modules/consensus/sync-committee/verifier/src/lib.rs

@@ -59,7 +59,7 @@ pub fn verify_sync_committee_attestation(
         ))?
     }
 
-    let state_period = compute_sync_committee_period_at_slot(trusted_state.finalized_header.slot);
+    let state_period = trusted_state.state_period;
     let update_signature_period = compute_sync_committee_period_at_slot(update.signature_slot);
     if !(state_period..=state_period + 1).contains(&update_signature_period) {
         Err(Error::InvalidUpdate("State period does not contain signature period".into()))?
@@ -192,6 +192,7 @@ pub fn verify_sync_committee_attestation(
                 latest_finalized_epoch: update.finality_proof.epoch,
                 current_sync_committee: trusted_state.next_sync_committee,
                 next_sync_committee: sync_committee_update.next_sync_committee,
+                state_period: state_period + 1,
             }
         } else {
             Err(Error::InvalidUpdate("Expected sync committee update to be present".into()))?