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Batch BLS verification for attestations (#2399)

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## Issue Addressed

NA

## Proposed Changes

Adds the ability to verify batches of aggregated/unaggregated attestations from the network.

When the `BeaconProcessor` finds there are messages in the aggregated or unaggregated attestation queues, it will first check the length of the queue:

- `== 1` verify the attestation individually.
- `>= 2` take up to 64 of those attestations and verify them in a batch.

Notably, we only perform batch verification if the queue has a backlog. We don't apply any artificial delays to attestations to try and force them into batches. 

### Batching Details

To assist with implementing batches we modify `beacon_chain::attestation_verification` to have two distinct categories for attestations:

- *Indexed* attestations: those which have passed initial validation and were valid enough for us to derive an `IndexedAttestation`.
- *Verified* attestations: those attestations which were indexed *and also* passed signature verification. These are well-formed, interesting messages which were signed by validators.

The batching functions accept `n` attestations and then return `n` attestation verification `Result`s, where those `Result`s can be any combination of `Ok` or `Err`. In other words, we attempt to verify as many attestations as possible and return specific per-attestation results so peer scores can be updated, if required.

When we batch verify attestations, we first try to map all those attestations to *indexed* attestations. If any of those attestations were able to be indexed, we then perform batch BLS verification on those indexed attestations. If the batch verification succeeds, we convert them into *verified* attestations, disabling individual signature checking. If the batch fails, we convert to verified attestations with individual signature checking enabled.

Ultimately, we optimistically try to do a batch verification of attestation signatures and fall-back to individual verification if it fails. This opens an attach vector for "poisoning" the attestations and causing us to waste a batch verification. I argue that peer scoring should do a good-enough job of defending against this and the typical-case gains massively outweigh the worst-case losses.

## Additional Info

Before this PR, attestation verification took the attestations by value (instead of by reference). It turns out that this was unnecessary and, in my opinion, resulted in some undesirable ergonomics (e.g., we had to pass the attestation back in the `Err` variant to avoid clones). In this PR I've modified attestation verification so that it now takes a reference.

I refactored the `beacon_chain/tests/attestation_verification.rs` tests so they use a builder-esque "tester" struct instead of a weird macro. It made it easier for me to test individual/batch with the same set of tests and I think it was a nice tidy-up. Notably, I did this last to try and make sure my new refactors to *actual* production code would pass under the existing test suite.
This commit is contained in:
Paul Hauner
2021-09-22 08:49:41 +00:00
parent 9667dc2f03
commit be11437c27
13 changed files with 1962 additions and 1037 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
beacon_node/beacon_chain/src/beacon_chain.rs
View File

@@ -1,5 +1,6 @@
use crate::attestation_verification::{
Error as AttestationError, SignatureVerifiedAttestation, VerifiedAggregatedAttestation,
batch_verify_aggregated_attestations, batch_verify_unaggregated_attestations,
Error as AttestationError, VerifiedAggregatedAttestation, VerifiedAttestation,
VerifiedUnaggregatedAttestation,
};
use crate::attester_cache::{AttesterCache, AttesterCacheKey};
@@ -1510,17 +1511,32 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
})
}
/// Performs the same validation as `Self::verify_unaggregated_attestation_for_gossip`, but for
/// multiple attestations using batch BLS verification. Batch verification can provide
/// significant CPU-time savings compared to individual verification.
pub fn batch_verify_unaggregated_attestations_for_gossip<'a, I>(
&self,
attestations: I,
) -> Result<
Vec<Result<VerifiedUnaggregatedAttestation<'a, T>, AttestationError>>,
AttestationError,
>
where
I: Iterator<Item = (&'a Attestation<T::EthSpec>, Option<SubnetId>)> + ExactSizeIterator,
{
batch_verify_unaggregated_attestations(attestations, self)
}
/// Accepts some `Attestation` from the network and attempts to verify it, returning `Ok(_)` if
/// it is valid to be (re)broadcast on the gossip network.
///
/// The attestation must be "unaggregated", that is it must have exactly one
/// aggregation bit set.
pub fn verify_unaggregated_attestation_for_gossip(
pub fn verify_unaggregated_attestation_for_gossip<'a>(
&self,
unaggregated_attestation: Attestation<T::EthSpec>,
unaggregated_attestation: &'a Attestation<T::EthSpec>,
subnet_id: Option<SubnetId>,
) -> Result<VerifiedUnaggregatedAttestation<T>, (AttestationError, Attestation<T::EthSpec>)>
{
) -> Result<VerifiedUnaggregatedAttestation<'a, T>, AttestationError> {
metrics::inc_counter(&metrics::UNAGGREGATED_ATTESTATION_PROCESSING_REQUESTS);
let _timer =
metrics::start_timer(&metrics::UNAGGREGATED_ATTESTATION_GOSSIP_VERIFICATION_TIMES);
@@ -1539,15 +1555,25 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
)
}
/// Performs the same validation as `Self::verify_aggregated_attestation_for_gossip`, but for
/// multiple attestations using batch BLS verification. Batch verification can provide
/// significant CPU-time savings compared to individual verification.
pub fn batch_verify_aggregated_attestations_for_gossip<'a, I>(
&self,
aggregates: I,
) -> Result<Vec<Result<VerifiedAggregatedAttestation<'a, T>, AttestationError>>, AttestationError>
where
I: Iterator<Item = &'a SignedAggregateAndProof<T::EthSpec>> + ExactSizeIterator,
{
batch_verify_aggregated_attestations(aggregates, self)
}
/// Accepts some `SignedAggregateAndProof` from the network and attempts to verify it,
/// returning `Ok(_)` if it is valid to be (re)broadcast on the gossip network.
pub fn verify_aggregated_attestation_for_gossip(
pub fn verify_aggregated_attestation_for_gossip<'a>(
&self,
signed_aggregate: SignedAggregateAndProof<T::EthSpec>,
) -> Result<
VerifiedAggregatedAttestation<T>,
(AttestationError, SignedAggregateAndProof<T::EthSpec>),
> {
signed_aggregate: &'a SignedAggregateAndProof<T::EthSpec>,
) -> Result<VerifiedAggregatedAttestation<'a, T>, AttestationError> {
metrics::inc_counter(&metrics::AGGREGATED_ATTESTATION_PROCESSING_REQUESTS);
let _timer =
metrics::start_timer(&metrics::AGGREGATED_ATTESTATION_GOSSIP_VERIFICATION_TIMES);
@@ -1597,13 +1623,13 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
/// Accepts some attestation-type object and attempts to verify it in the context of fork
/// choice. If it is valid it is applied to `self.fork_choice`.
///
/// Common items that implement `SignatureVerifiedAttestation`:
/// Common items that implement `VerifiedAttestation`:
///
/// - `VerifiedUnaggregatedAttestation`
/// - `VerifiedAggregatedAttestation`
pub fn apply_attestation_to_fork_choice(
&self,
verified: &impl SignatureVerifiedAttestation<T>,
verified: &impl VerifiedAttestation<T>,
) -> Result<(), Error> {
let _timer = metrics::start_timer(&metrics::FORK_CHOICE_PROCESS_ATTESTATION_TIMES);
@@ -1623,8 +1649,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
/// and no error is returned.
pub fn add_to_naive_aggregation_pool(
&self,
unaggregated_attestation: VerifiedUnaggregatedAttestation<T>,
) -> Result<VerifiedUnaggregatedAttestation<T>, AttestationError> {
unaggregated_attestation: &impl VerifiedAttestation<T>,
) -> Result<(), AttestationError> {
let _timer = metrics::start_timer(&metrics::ATTESTATION_PROCESSING_APPLY_TO_AGG_POOL);
let attestation = unaggregated_attestation.attestation();
@@ -1660,7 +1686,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
}
};
Ok(unaggregated_attestation)
Ok(())
}
/// Accepts a `VerifiedSyncCommitteeMessage` and attempts to apply it to the "naive
@@ -1727,13 +1753,13 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
Ok(verified_sync_committee_message)
}
/// Accepts a `VerifiedAggregatedAttestation` and attempts to apply it to `self.op_pool`.
/// Accepts a `VerifiedAttestation` and attempts to apply it to `self.op_pool`.
///
/// The op pool is used by local block producers to pack blocks with operations.
pub fn add_to_block_inclusion_pool(
&self,
signed_aggregate: VerifiedAggregatedAttestation<T>,
) -> Result<VerifiedAggregatedAttestation<T>, AttestationError> {
verified_attestation: &impl VerifiedAttestation<T>,
) -> Result<(), AttestationError> {
let _timer = metrics::start_timer(&metrics::ATTESTATION_PROCESSING_APPLY_TO_OP_POOL);
// If there's no eth1 chain then it's impossible to produce blocks and therefore
@@ -1745,7 +1771,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
self.op_pool
.insert_attestation(
// TODO: address this clone.
signed_aggregate.attestation().clone(),
verified_attestation.attestation().clone(),
&fork,
self.genesis_validators_root,
&self.spec,
@@ -1753,7 +1779,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
.map_err(Error::from)?;
}
Ok(signed_aggregate)
Ok(())
}
/// Accepts a `VerifiedSyncContribution` and attempts to apply it to `self.op_pool`.