Fix issue with last_justified_block_hash

Previously we were just checking it exists in the DB. This is incorrect
because the last_justified_block_hash _must_ be in the chain referenced
by the block.

I.e., it's not OK for a block to reference a justified block in another
chain.

beacon_chain/validation/src/attestation_validation.rs

@@ -12,10 +12,7 @@ use super::db::{
     ClientDB,
     DBError
 };
-use super::db::stores::{
+use super::db::stores::ValidatorStore;
-    BlockStore,
-    ValidatorStore,
-};
 use super::types::{
     Hash256,
 };
@@ -57,10 +54,10 @@ pub struct AttestationValidationContext<T>
     pub cycle_length: u8,
     /// The last justified slot as per the client's view of the canonical chain.
     pub last_justified_slot: u64,
+    /// The last justified block hash as per the client's view of the canonical chain.
+    pub last_justified_block_hash: Hash256,
     /// A vec of the hashes of the blocks preceeding the present slot.
     pub parent_hashes: Arc<Vec<Hash256>>,
-    /// The store containing block information.
-    pub block_store: Arc<BlockStore<T>>,
     /// The store containing validator information.
     pub validator_store: Arc<ValidatorStore<T>>,
     /// A map of (slot, shard_id) to the attestation set of validation indices.
@@ -104,6 +101,14 @@ impl<T> AttestationValidationContext<T>
             return Err(AttestationValidationError::JustifiedSlotIncorrect);
         }
 
+        /*
+         * The specified justified block hash supplied in the attestation must match our knowledge
+         * of the last justified block this chain.
+         */
+        if a.justified_block_hash != self.last_justified_block_hash {
+            return Err(AttestationValidationError::UnknownJustifiedBlock)
+        }
+
         /*
          * There is no need to include more oblique parents hashes than there are blocks
          * in a cycle.
@@ -142,13 +147,6 @@ impl<T> AttestationValidationContext<T>
             return Err(AttestationValidationError::InvalidBitfieldEndBits)
         }
 
-        /*
-         * The specified justified block hash must be known to us
-         */
-        if !self.block_store.block_exists(&a.justified_block_hash)? {
-            return Err(AttestationValidationError::UnknownJustifiedBlock)
-        }
-
         let signed_message = {
             let parent_hashes = attestation_parent_hashes(
                 self.cycle_length,

beacon_chain/validation/src/block_validation.rs

@@ -72,6 +72,8 @@ pub struct BlockValidationContext<T>
     pub cycle_length: u8,
     /// The last justified slot as per the client's view of the canonical chain.
     pub last_justified_slot: u64,
+    /// The last justified block hash as per the client's view of the canonical chain.
+    pub last_justified_block_hash: Hash256,
     /// The last finalized slot as per the client's view of the canonical chain.
     pub last_finalized_slot: u64,
     /// A vec of the hashes of the blocks preceeding the present slot.
@@ -205,8 +207,8 @@ impl<T> BlockValidationContext<T>
             block_slot,
             cycle_length: self.cycle_length,
             last_justified_slot: self.last_justified_slot,
+            last_justified_block_hash: self.last_justified_block_hash,
             parent_hashes: self.parent_hashes.clone(),
-            block_store: self.block_store.clone(),
             validator_store: self.validator_store.clone(),
             attester_map: self.attester_map.clone(),
         });

beacon_chain/validation/tests/attestation_validation/helpers.rs

@@ -3,10 +3,7 @@ use std::sync::Arc;
 use super::db::{
     MemoryDB,
 };
-use super::db::stores::{
+use super::db::stores::ValidatorStore;
-    BlockStore,
-    ValidatorStore,
-};
 use super::types::{
     AttestationRecord,
     AttesterMap,
@@ -30,18 +27,15 @@ use super::hashing::{
 
 pub struct TestStore {
     pub db: Arc<MemoryDB>,
-    pub block: Arc<BlockStore<MemoryDB>>,
     pub validator: Arc<ValidatorStore<MemoryDB>>,
 }
 
 impl TestStore {
     pub fn new() -> Self {
         let db = Arc::new(MemoryDB::open());
-        let block = Arc::new(BlockStore::new(db.clone()));
         let validator = Arc::new(ValidatorStore::new(db.clone()));
         Self {
             db,
-            block,
             validator,
         }
     }
@@ -141,8 +135,6 @@ pub fn setup_attestation_validation_test(shard_id: u16, attester_count: usize)
     let justified_block_hash = Hash256::from("justified_block".as_bytes());
     let shard_block_hash = Hash256::from("shard_block".as_bytes());
 
-    stores.block.put_serialized_block(&justified_block_hash.as_ref(), &[42]).unwrap();
-
     let attestation_slot = block_slot - 1;
 
     let mut keypairs = vec![];
@@ -167,8 +159,8 @@ pub fn setup_attestation_validation_test(shard_id: u16, attester_count: usize)
         block_slot,
         cycle_length,
         last_justified_slot,
+        last_justified_block_hash: justified_block_hash,
         parent_hashes: parent_hashes.clone(),
-        block_store: stores.block.clone(),
         validator_store: stores.validator.clone(),
         attester_map: Arc::new(attester_map),
     };

beacon_chain/validation/tests/block_validation/helpers.rs

@@ -41,6 +41,7 @@ pub struct BlockTestParams {
     pub parent_proposer_index: usize,
     pub validation_context_slot: u64,
     pub validation_context_justified_slot: u64,
+    pub validation_context_justified_block_hash: Hash256,
     pub validation_context_finalized_slot: u64,
 }
 
@@ -93,7 +94,6 @@ pub fn setup_block_validation_scenario(params: &BlockTestParams)
     let shard_block_hash = Hash256::from("shard_block_hash".as_bytes());
 
     stores.pow_chain.put_block_hash(pow_chain_ref.as_ref()).unwrap();
-    stores.block.put_serialized_block(justified_block_hash.as_ref(), &vec![42]).unwrap();
 
     /*
      * Generate a minimum viable parent block and store it in the database.
@@ -205,6 +205,7 @@ pub fn run_block_validation_scenario<F>(
         present_slot: params.validation_context_slot,
         cycle_length: params.cycle_length,
         last_justified_slot: params.validation_context_justified_slot,
+        last_justified_block_hash: params.validation_context_justified_block_hash,
         last_finalized_slot: params.validation_context_finalized_slot,
         parent_hashes: Arc::new(parent_hashes),
         proposer_map: Arc::new(proposer_map),

beacon_chain/validation/tests/block_validation/tests.rs

@@ -34,6 +34,7 @@ fn get_simple_params() -> BlockTestParams {
 
     let validation_context_slot = block_slot;
     let validation_context_justified_slot = attestations_justified_slot;
+    let validation_context_justified_block_hash = Hash256::from("justified_hash".as_bytes());
     let validation_context_finalized_slot = 0;
 
     BlockTestParams {
@@ -47,6 +48,7 @@ fn get_simple_params() -> BlockTestParams {
         attestations_justified_slot,
         validation_context_slot,
         validation_context_justified_slot,
+        validation_context_justified_block_hash,
         validation_context_finalized_slot,
     }
 }