252 lines
8.6 KiB
Rust
252 lines
8.6 KiB
Rust
use std::collections::HashSet;
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use std::sync::Arc;
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use super::types::{
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AttestationRecord,
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AttesterMap,
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};
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use super::attestation_parent_hashes::{
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attestation_parent_hashes,
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ParentHashesError,
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};
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use super::db::{
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ClientDB,
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DBError
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};
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use super::db::stores::{
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BlockStore,
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BlockAtSlotError,
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ValidatorStore,
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};
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use super::types::{
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Hash256,
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};
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use super::message_generation::generate_signed_message;
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use super::signature_verification::{
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verify_aggregate_signature_for_indices,
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SignatureVerificationError,
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};
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#[derive(Debug,PartialEq)]
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pub enum AttestationValidationError {
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SlotTooHigh,
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SlotTooLow,
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JustifiedSlotIncorrect,
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InvalidJustifiedBlockHash,
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TooManyObliqueHashes,
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BadCurrentHashes,
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BadObliqueHashes,
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BadAttesterMap,
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IntWrapping,
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PublicKeyCorrupt,
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NoPublicKeyForValidator,
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BadBitfieldLength,
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InvalidBitfield,
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InvalidBitfieldEndBits,
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NoSignatures,
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NonZeroTrailingBits,
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BadAggregateSignature,
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DBError(String),
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}
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/// The context against which some attestation should be validated.
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pub struct AttestationValidationContext<T>
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where T: ClientDB + Sized
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{
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/// The slot as determined by the system time.
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pub block_slot: u64,
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/// The cycle_length as determined by the chain configuration.
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pub cycle_length: u8,
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/// The last justified slot as per the client's view of the canonical chain.
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pub last_justified_slot: u64,
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/// A vec of the hashes of the blocks preceeding the present slot.
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pub parent_hashes: Arc<Vec<Hash256>>,
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/// The store containing block information.
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pub block_store: Arc<BlockStore<T>>,
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/// The store containing validator information.
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pub validator_store: Arc<ValidatorStore<T>>,
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/// A map of (slot, shard_id) to the attestation set of validation indices.
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pub attester_map: Arc<AttesterMap>,
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}
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impl<T> AttestationValidationContext<T>
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where T: ClientDB
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{
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/// Validate a (fully deserialized) AttestationRecord against this context.
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///
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/// The function will return a HashSet of validator indices (canonical validator indices not
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/// attestation indices) if the validation passed successfully, or an error otherwise.
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///
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/// The attestation's aggregate signature will be verified, therefore the function must able to
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/// access all required validation public keys via the `validator_store`.
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pub fn validate_attestation(&self, a: &AttestationRecord)
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-> Result<HashSet<usize>, AttestationValidationError>
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{
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/*
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* The attesation slot must not be higher than the block that contained it.
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*/
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if a.slot > self.block_slot {
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return Err(AttestationValidationError::SlotTooHigh);
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}
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/*
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* The slot of this attestation must not be more than cycle_length + 1 distance
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* from the block that contained it.
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*/
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if a.slot < self.block_slot
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.saturating_sub(u64::from(self.cycle_length).saturating_add(1)) {
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return Err(AttestationValidationError::SlotTooLow);
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}
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/*
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* The attestation must indicate that its last justified slot is the same as the last justified
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* slot known to us.
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*/
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if a.justified_slot > self.last_justified_slot {
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return Err(AttestationValidationError::JustifiedSlotIncorrect);
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}
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/*
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* There is no need to include more oblique parents hashes than there are blocks
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* in a cycle.
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*/
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if a.oblique_parent_hashes.len() > usize::from(self.cycle_length) {
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return Err(AttestationValidationError::TooManyObliqueHashes);
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}
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/*
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* Retrieve the set of attestation indices for this slot and shard id.
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*
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* This is an array mapping the order that validators will appear in the bitfield to the
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* canonincal index of a validator.
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*/
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let attestation_indices = self.attester_map.get(&(a.slot, a.shard_id))
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.ok_or(AttestationValidationError::BadAttesterMap)?;
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/*
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* The bitfield must be no longer than the minimum required to represent each validator in the
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* attestation indicies for this slot and shard id.
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*/
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if a.attester_bitfield.num_bytes() !=
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bytes_for_bits(attestation_indices.len())
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{
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return Err(AttestationValidationError::BadBitfieldLength);
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}
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/*
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* If there are excess bits in the bitfield because the number of a validators in not a
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* multiple of 8, reject this attestation record.
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*
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* Allow extra set bits would permit mutliple different byte layouts (and therefore hashes) to
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* refer to the same AttesationRecord.
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*/
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if a.attester_bitfield.len() > attestation_indices.len() {
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return Err(AttestationValidationError::InvalidBitfieldEndBits)
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}
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/*
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* Generate the parent hashes for this attestation
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*/
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let parent_hashes = attestation_parent_hashes(
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self.cycle_length,
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self.block_slot,
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a.slot,
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&self.parent_hashes,
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&a.oblique_parent_hashes)?;
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/*
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* The specified justified block hash supplied in the attestation must be in the chain at
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* the given slot number.
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*
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* First, we find the latest parent hash from the parent_hashes array. Then, using the
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* block store (database) we iterate back through the blocks until we find (or fail to
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* find) the justified block hash referenced in the attestation record.
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*/
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let latest_parent_hash = parent_hashes.last()
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.ok_or(AttestationValidationError::BadCurrentHashes)?;
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match self.block_store.block_at_slot(&latest_parent_hash, a.justified_slot)? {
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Some((ref hash, _)) if *hash == a.justified_block_hash.to_vec() => (),
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_ => return Err(AttestationValidationError::InvalidJustifiedBlockHash)
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};
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/*
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* Generate the message that this attestation aggregate signature must sign across.
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*/
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let signed_message = {
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generate_signed_message(
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a.slot,
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&parent_hashes,
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a.shard_id,
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&a.shard_block_hash,
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a.justified_slot)
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};
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let voted_hashset =
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verify_aggregate_signature_for_indices(
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&signed_message,
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&a.aggregate_sig,
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&attestation_indices,
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&a.attester_bitfield,
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&self.validator_store)?;
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/*
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* If the hashset of voters is None, the signature verification failed.
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*/
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match voted_hashset {
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None => Err(AttestationValidationError::BadAggregateSignature),
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Some(hashset) => Ok(hashset),
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}
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}
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}
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fn bytes_for_bits(bits: usize) -> usize {
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(bits.saturating_sub(1) / 8) + 1
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}
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impl From<ParentHashesError> for AttestationValidationError {
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fn from(e: ParentHashesError) -> Self {
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match e {
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ParentHashesError::BadCurrentHashes
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=> AttestationValidationError::BadCurrentHashes,
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ParentHashesError::BadObliqueHashes
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=> AttestationValidationError::BadObliqueHashes,
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ParentHashesError::SlotTooLow
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=> AttestationValidationError::SlotTooLow,
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ParentHashesError::SlotTooHigh
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=> AttestationValidationError::SlotTooHigh,
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ParentHashesError::IntWrapping
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=> AttestationValidationError::IntWrapping
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}
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}
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}
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impl From<BlockAtSlotError> for AttestationValidationError {
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fn from(e: BlockAtSlotError) -> Self {
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match e {
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BlockAtSlotError::DBError(s) => AttestationValidationError::DBError(s),
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_ => AttestationValidationError::InvalidJustifiedBlockHash
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}
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}
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}
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impl From<DBError> for AttestationValidationError {
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fn from(e: DBError) -> Self {
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AttestationValidationError::DBError(e.message)
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}
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}
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impl From<SignatureVerificationError> for AttestationValidationError {
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fn from(e: SignatureVerificationError) -> Self {
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match e {
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SignatureVerificationError::BadValidatorIndex
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=> AttestationValidationError::BadAttesterMap,
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SignatureVerificationError::PublicKeyCorrupt
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=> AttestationValidationError::PublicKeyCorrupt,
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SignatureVerificationError::NoPublicKeyForValidator
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=> AttestationValidationError::NoPublicKeyForValidator,
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SignatureVerificationError::DBError(s)
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=> AttestationValidationError::DBError(s),
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}
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}
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}
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