Progress further on attestation validation

lighthouse/state/validation/attestation_validation.rs

@@ -1,3 +1,4 @@
+use std::collections::HashSet;
 use super::AttestationRecord;
 use super::attestation_parent_hashes::{
     attestation_parent_hashes,
@@ -12,33 +13,35 @@ use super::db::stores::{
     ValidatorStore,
 };
 use super::ssz::SszStream;
-use super::bls::{
-    AggregateSignature,
-    AggregatePublicKey,
-    PublicKey,
-};
 use super::utils::hash::canonical_hash;
 use super::utils::types::{
     Hash256,
-    Bitfield,
 };
 use std::collections::HashMap;
 use std::sync::Arc;
+use super::signatures::{
+    verify_aggregate_signature_for_indices,
+    SignatureVerificationError,
+};
 
 #[derive(Debug,PartialEq)]
 pub enum AttestationValidationError {
     SlotTooHigh,
     SlotTooLow,
     JustifiedSlotTooHigh,
+    UnknownJustifiedBlock,
     TooManyObliqueHashes,
     BadCurrentHashes,
     BadObliqueHashes,
     BadAttesterMap,
     IntWrapping,
+    PublicKeyCorrupt,
+    NoPublicKeyForValidator,
     IncorrectBitField,
     NoSignatures,
     NonZeroTrailingBits,
-    AggregateSignatureFail
+    AggregateSignatureFail,
+    DBError(String),
 }
 
 type Slot = u64;
@@ -55,8 +58,9 @@ pub fn validate_attestation<T>(a: &AttestationRecord,
                                known_last_justified_slot: u64,
                                known_parent_hashes: Arc<Vec<Hash256>>,
                                block_store: BlockStore<T>,
+                               validator_store: ValidatorStore<T>,
                                attester_map: Arc<AttesterMap>)
-    -> Result<bool, AttestationValidationError>
+    -> Result<(bool, Option<HashSet<usize>>), AttestationValidationError>
     where T: ClientDB + Sized
 {
     /*
@@ -92,15 +96,46 @@ pub fn validate_attestation<T>(a: &AttestationRecord,
         return Err(AttestationValidationError::TooManyObliqueHashes);
     }
 
+    /*
+     * Retrieve the set of attestation indices for this slot and shard id.
+     *
+     * This is an array mapping the order that validators will appear in the bitfield to the
+     * canonincal index of a validator.
+     */
     let attestation_indices = attester_map.get(&(a.slot, a.shard_id.into()))
         .ok_or(AttestationValidationError::BadAttesterMap)?;
 
+    /*
+     * The bitfield must be no longer than the minimum required to represent each validator in the
+     * attestation indicies for this slot and shard id.
+     */
     if a.attester_bitfield.num_bytes() !=
         bytes_for_bits(attestation_indices.len())
     {
         return Err(AttestationValidationError::IncorrectBitField);
     }
 
+    /*
+     * If there are excess bits in the bitfield because the number of a validators in not a
+     * multiple of 8, reject this attestation record.
+     *
+     * Allow extra set bits would permit mutliple different byte layouts (and therefore hashes) to
+     * refer to the same AttesationRecord.
+     */
+    let last_byte =
+        a.attester_bitfield.get_byte(a.attester_bitfield.num_bytes())
+        .ok_or(AttestationValidationError::IncorrectBitField)?;
+    if any_of_last_n_bits_are_set(last_byte, a.attester_bitfield.len() % 8) {
+        return Err(AttestationValidationError::IncorrectBitField)
+    }
+
+    /*
+     * The specified justified block hash must be known to us
+     */
+    if !block_store.block_exists(&a.justified_block_hash)? {
+        return Err(AttestationValidationError::UnknownJustifiedBlock)
+    }
+
     let signed_message = {
         let parent_hashes = attestation_parent_hashes(
             cycle_length,
@@ -116,15 +151,20 @@ pub fn validate_attestation<T>(a: &AttestationRecord,
             a.justified_slot)
     };
 
-    Ok(false)
+    let (signature_valid, voted_hashmap) =
+        verify_aggregate_signature_for_indices(
+            &signed_message,
+            &a.aggregate_sig,
+            &attestation_indices,
+            &a.attester_bitfield,
+            &validator_store)?;
+
+    Ok((signature_valid, voted_hashmap))
 }
 
-fn collect_pub_keys(attestation_indices: &Vec<usize>,
-                    bitfield: &Bitfield)
-    -> Option<Vec<PublicKey>>
-{
-    // cats
-    None
+fn any_of_last_n_bits_are_set(byte: &u8, n: usize) -> bool {
+    let shift = 8_u8.saturating_sub(n as u8);
+    ((!0 >> shift) & byte) > 0
 }
 
 /// Generates the message used to validate the signature provided with an AttestationRecord.
@@ -161,16 +201,37 @@ fn generate_signed_message(slot: u64,
 impl From<ParentHashesError> for AttestationValidationError {
     fn from(e: ParentHashesError) -> Self {
         match e {
-            ParentHashesError::BadCurrentHashes =>
-                AttestationValidationError::BadCurrentHashes,
-            ParentHashesError::BadObliqueHashes =>
-                AttestationValidationError::BadObliqueHashes,
-            ParentHashesError::SlotTooLow =>
-                AttestationValidationError::SlotTooLow,
-            ParentHashesError::SlotTooHigh =>
-                AttestationValidationError::SlotTooHigh,
-            ParentHashesError::IntWrapping =>
-                AttestationValidationError::IntWrapping
+            ParentHashesError::BadCurrentHashes
+                => AttestationValidationError::BadCurrentHashes,
+            ParentHashesError::BadObliqueHashes
+                => AttestationValidationError::BadObliqueHashes,
+            ParentHashesError::SlotTooLow
+                => AttestationValidationError::SlotTooLow,
+            ParentHashesError::SlotTooHigh
+                => AttestationValidationError::SlotTooHigh,
+            ParentHashesError::IntWrapping
+                => AttestationValidationError::IntWrapping
+        }
+    }
+}
+
+impl From<DBError> for AttestationValidationError {
+    fn from(e: DBError) -> Self {
+        AttestationValidationError::DBError(e.message)
+    }
+}
+
+impl From<SignatureVerificationError> for AttestationValidationError {
+    fn from(e: SignatureVerificationError) -> Self {
+        match e {
+            SignatureVerificationError::BadValidatorIndex
+                => AttestationValidationError::BadAttesterMap,
+            SignatureVerificationError::PublicKeyCorrupt
+                => AttestationValidationError::PublicKeyCorrupt,
+            SignatureVerificationError::NoPublicKeyForValidator
+                => AttestationValidationError::NoPublicKeyForValidator,
+            SignatureVerificationError::DBError(s)
+                => AttestationValidationError::DBError(s),
         }
     }
 }