fix(replication): gate audits by mature repair proofs

src/replication/audit.rs

@@ -2,7 +2,7 @@
 //!
 //! Challenge-response for claimed holders. Anti-outsourcing protection.
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 
 use crate::logging::{debug, info, warn};
@@ -15,10 +15,13 @@ use crate::replication::protocol::{
     compute_audit_digest, AuditChallenge, AuditResponse, ReplicationMessage,
     ReplicationMessageBody, ABSENT_KEY_DIGEST,
 };
-use crate::replication::types::{AuditFailureReason, FailureEvidence, PeerSyncRecord};
+use crate::replication::types::{
+    AuditFailureReason, FailureEvidence, PeerSyncRecord, RepairProofs,
+};
 use crate::storage::LmdbStorage;
 use saorsa_core::identity::PeerId;
 use saorsa_core::P2PNode;
+use tokio::sync::RwLock;
 
 // ---------------------------------------------------------------------------
 // Audit tick result
@@ -61,13 +64,42 @@ pub enum AuditTickResult {
 /// **Invariant 19**: Returns [`AuditTickResult::Idle`] immediately if
 /// `is_bootstrapping` is `true` — a node must not audit others while it
 /// is still bootstrapping.
-#[allow(clippy::implicit_hasher, clippy::too_many_lines)]
+#[allow(clippy::implicit_hasher)]
 pub async fn audit_tick(
     p2p_node: &Arc<P2PNode>,
     storage: &Arc<LmdbStorage>,
     config: &ReplicationConfig,
     sync_history: &HashMap<PeerId, PeerSyncRecord>,
     is_bootstrapping: bool,
+) -> AuditTickResult {
+    let repair_proofs = Arc::new(RwLock::new(RepairProofs::new()));
+    audit_tick_with_repair_proofs(
+        p2p_node,
+        storage,
+        config,
+        sync_history,
+        &repair_proofs,
+        0,
+        is_bootstrapping,
+    )
+    .await
+}
+
+/// Execute one repair-proof-gated audit tick.
+///
+/// This is the production path used by the replication engine. The
+/// compatibility [`audit_tick`] wrapper passes an empty proof table, so direct
+/// callers that have not adopted repair proofs remain conservative and do not
+/// audit peers for unproven keys.
+#[allow(clippy::implicit_hasher, clippy::too_many_lines)]
+pub async fn audit_tick_with_repair_proofs(
+    p2p_node: &Arc<P2PNode>,
+    storage: &Arc<LmdbStorage>,
+    config: &ReplicationConfig,
+    sync_history: &HashMap<PeerId, PeerSyncRecord>,
+    repair_proofs: &Arc<RwLock<RepairProofs>>,
+    current_sync_epoch: u64,
+    is_bootstrapping: bool,
 ) -> AuditTickResult {
     // Invariant 19: never audit while still bootstrapping.
     if is_bootstrapping {
@@ -119,17 +151,30 @@ pub async fn audit_tick(
             .collect()
     };
 
-    // Step 4: Filter to keys where the chosen peer is in the close group.
-    let mut peer_keys = Vec::new();
+    // Step 4: Filter to keys where the chosen peer is in the close group and
+    // this node has proof that it already sent the peer a repair hint for the
+    // specific key.
+    let mut sampled_key_groups = Vec::new();
     for key in &sampled_keys {
         let closest = dht
             .find_closest_nodes_local_with_self(key, config.close_group_size)
             .await;
-        if closest.iter().any(|n| n.peer_id == challenged_peer) {
-            peer_keys.push(*key);
+        let close_peers: HashSet<PeerId> = closest.iter().map(|node| node.peer_id).collect();
+        if close_peers.contains(&challenged_peer) {
+            sampled_key_groups.push((*key, close_peers));
         }
     }
 
+    let peer_keys = {
+        let mut proofs = repair_proofs.write().await;
+        mature_audit_keys_for_peer(
+            &challenged_peer,
+            sampled_key_groups,
+            &mut proofs,
+            current_sync_epoch,
+        )
+    };
+
     if peer_keys.is_empty() {
         return AuditTickResult::Idle;
     }
@@ -299,6 +344,22 @@ fn eligible_audit_peers(sync_history: &HashMap<PeerId, PeerSyncRecord>) -> Vec<P
         .collect()
 }
 
+fn mature_audit_keys_for_peer(
+    challenged_peer: &PeerId,
+    sampled_key_groups: Vec<(XorName, HashSet<PeerId>)>,
+    repair_proofs: &mut RepairProofs,
+    current_sync_epoch: u64,
+) -> Vec<XorName> {
+    sampled_key_groups
+        .into_iter()
+        .filter_map(|(key, close_peers)| {
+            repair_proofs
+                .has_mature_replica_hint(challenged_peer, &key, &close_peers, current_sync_epoch)
+                .then_some(key)
+        })
+        .collect()
+}
+
 // ---------------------------------------------------------------------------
 // Digest verification
 // ---------------------------------------------------------------------------
@@ -1133,6 +1194,69 @@ mod tests {
         );
     }
 
+    #[test]
+    fn audit_key_filter_accepts_only_mature_current_snapshot_repair_proofs() {
+        const HINT_EPOCH: u64 = 7;
+        const CURRENT_EPOCH: u64 = HINT_EPOCH + 1;
+        const CHALLENGED_PEER_BYTE: u8 = 0xA1;
+        const OTHER_PEER_BYTE: u8 = 0xA2;
+        const NEW_PEER_BYTE: u8 = 0xA3;
+        const MATURE_KEY_BYTE: u8 = 0xB1;
+        const SAME_EPOCH_KEY_BYTE: u8 = 0xB2;
+        const MISSING_PROOF_KEY_BYTE: u8 = 0xB3;
+        const STALE_SNAPSHOT_KEY_BYTE: u8 = 0xB4;
+        const XOR_NAME_LEN: usize = 32;
+
+        let challenged_peer = peer_id_from_bytes([CHALLENGED_PEER_BYTE; XOR_NAME_LEN]);
+        let other_peer = peer_id_from_bytes([OTHER_PEER_BYTE; XOR_NAME_LEN]);
+        let new_peer = peer_id_from_bytes([NEW_PEER_BYTE; XOR_NAME_LEN]);
+        let mature_key = [MATURE_KEY_BYTE; XOR_NAME_LEN];
+        let same_epoch_key = [SAME_EPOCH_KEY_BYTE; XOR_NAME_LEN];
+        let missing_proof_key = [MISSING_PROOF_KEY_BYTE; XOR_NAME_LEN];
+        let stale_snapshot_key = [STALE_SNAPSHOT_KEY_BYTE; XOR_NAME_LEN];
+        let close_group = HashSet::from([challenged_peer, other_peer]);
+        let changed_close_group = HashSet::from([challenged_peer, new_peer]);
+        let mut repair_proofs = RepairProofs::new();
+
+        assert!(repair_proofs.record_replica_hint_sent(
+            challenged_peer,
+            mature_key,
+            &close_group,
+            HINT_EPOCH,
+        ));
+        assert!(repair_proofs.record_replica_hint_sent(
+            challenged_peer,
+            same_epoch_key,
+            &close_group,
+            CURRENT_EPOCH,
+        ));
+        assert!(repair_proofs.record_replica_hint_sent(
+            challenged_peer,
+            stale_snapshot_key,
+            &close_group,
+            HINT_EPOCH,
+        ));
+
+        let sampled_key_groups = vec![
+            (mature_key, close_group.clone()),
+            (same_epoch_key, close_group.clone()),
+            (missing_proof_key, close_group),
+            (stale_snapshot_key, changed_close_group),
+        ];
+        let peer_keys = mature_audit_keys_for_peer(
+            &challenged_peer,
+            sampled_key_groups,
+            &mut repair_proofs,
+            CURRENT_EPOCH,
+        );
+
+        assert_eq!(
+            peer_keys,
+            vec![mature_key],
+            "only mature proofs for the current close-group snapshot should become audit keys"
+        );
+    }
+
     // -- Audit response must match key count --------------------------------------
 
     #[tokio::test]