lighthouse/beacon_node/beacon_chain/tests/block_verification.rs

#![cfg(not(debug_assertions))]

use beacon_chain::test_utils::{
    AttestationStrategy, BeaconChainHarness, BlockStrategy, EphemeralTestingSlotClockHarnessType,
};
use beacon_chain::{BeaconSnapshot, BlockError, ChainSegmentResult, NotifyExecutionLayer};
use fork_choice::CountUnrealized;
use lazy_static::lazy_static;
use logging::test_logger;
use slasher::{Config as SlasherConfig, Slasher};
use state_processing::{
    common::get_indexed_attestation,
    per_block_processing::{per_block_processing, BlockSignatureStrategy},
    per_slot_processing, BlockProcessingError, ConsensusContext, VerifyBlockRoot,
};
use std::marker::PhantomData;
use std::sync::Arc;
use tempfile::tempdir;
use types::signed_block_and_blobs::BlockWrapper;
use types::{test_utils::generate_deterministic_keypair, *};

type E = MainnetEthSpec;

// Should ideally be divisible by 3.
const VALIDATOR_COUNT: usize = 24;
const CHAIN_SEGMENT_LENGTH: usize = 64 * 5;
const BLOCK_INDICES: &[usize] = &[0, 1, 32, 64, 68 + 1, 129, CHAIN_SEGMENT_LENGTH - 1];

lazy_static! {
    /// A cached set of keys.
    static ref KEYPAIRS: Vec<Keypair> = types::test_utils::generate_deterministic_keypairs(VALIDATOR_COUNT);
}

async fn get_chain_segment() -> Vec<BeaconSnapshot<E>> {
    let harness = get_harness(VALIDATOR_COUNT);

    harness
        .extend_chain(
            CHAIN_SEGMENT_LENGTH,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::AllValidators,
        )
        .await;

    let mut segment = Vec::with_capacity(CHAIN_SEGMENT_LENGTH);
    for snapshot in harness
        .chain
        .chain_dump()
        .expect("should dump chain")
        .into_iter()
        .skip(1)
    {
        let full_block = harness
            .chain
            .get_block(&snapshot.beacon_block_root)
            .await
            .unwrap()
            .unwrap();
        segment.push(BeaconSnapshot {
            beacon_block_root: snapshot.beacon_block_root,
            beacon_block: Arc::new(full_block),
            beacon_state: snapshot.beacon_state,
        });
    }
    segment
}

fn get_harness(
    validator_count: usize,
) -> BeaconChainHarness<EphemeralTestingSlotClockHarnessType<E>> {
    let harness = BeaconChainHarness::builder(MainnetEthSpec)
        .default_spec()
        .keypairs(KEYPAIRS[0..validator_count].to_vec())
        .fresh_ephemeral_store()
        .mock_execution_layer()
        .build();

    harness.advance_slot();

    harness
}

fn chain_segment_blocks(chain_segment: &[BeaconSnapshot<E>]) -> Vec<Arc<SignedBeaconBlock<E>>> {
    chain_segment
        .iter()
        .map(|snapshot| snapshot.beacon_block.clone().into())
        .collect()
}

fn junk_signature() -> Signature {
    let kp = generate_deterministic_keypair(VALIDATOR_COUNT);
    let message = Hash256::from_slice(&[42; 32]);
    kp.sk.sign(message)
}

fn junk_aggregate_signature() -> AggregateSignature {
    let mut agg_sig = AggregateSignature::empty();
    agg_sig.add_assign(&junk_signature());
    agg_sig
}

fn update_proposal_signatures(
    snapshots: &mut [BeaconSnapshot<E>],
    harness: &BeaconChainHarness<EphemeralTestingSlotClockHarnessType<E>>,
) {
    for snapshot in snapshots {
        let spec = &harness.chain.spec;
        let slot = snapshot.beacon_block.slot();
        let state = &snapshot.beacon_state;
        let proposer_index = state
            .get_beacon_proposer_index(slot, spec)
            .expect("should find proposer index");
        let keypair = harness
            .validator_keypairs
            .get(proposer_index)
            .expect("proposer keypair should be available");

        let (block, _) = snapshot.beacon_block.as_ref().clone().deconstruct();
        snapshot.beacon_block = Arc::new(block.sign(
            &keypair.sk,
            &state.fork(),
            state.genesis_validators_root(),
            spec,
        ));
    }
}

fn update_parent_roots(snapshots: &mut [BeaconSnapshot<E>]) {
    for i in 0..snapshots.len() {
        let root = snapshots[i].beacon_block.canonical_root();
        if let Some(child) = snapshots.get_mut(i + 1) {
            let (mut block, signature) = child.beacon_block.as_ref().clone().deconstruct();
            *block.parent_root_mut() = root;
            child.beacon_block = Arc::new(SignedBeaconBlock::from_block(block, signature))
        }
    }
}

#[tokio::test]
async fn chain_segment_full_segment() {
    let harness = get_harness(VALIDATOR_COUNT);
    let chain_segment = get_chain_segment().await;
    let blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
        .into_iter()
        .map(|block| block.into())
        .collect();

    harness
        .chain
        .slot_clock
        .set_slot(blocks.last().unwrap().slot().as_u64());

    // Sneak in a little check to ensure we can process empty chain segments.
    harness
        .chain
        .process_chain_segment(vec![], CountUnrealized::True, NotifyExecutionLayer::Yes)
        .await
        .into_block_error()
        .expect("should import empty chain segment");

    harness
        .chain
        .process_chain_segment(
            blocks.clone(),
            CountUnrealized::True,
            NotifyExecutionLayer::Yes,
        )
        .await
        .into_block_error()
        .expect("should import chain segment");

    harness.chain.recompute_head_at_current_slot().await;

    assert_eq!(
        harness.head_block_root(),
        blocks.last().unwrap().block().canonical_root(),
        "harness should have last block as head"
    );
}

#[tokio::test]
async fn chain_segment_varying_chunk_size() {
    for chunk_size in &[1, 2, 3, 5, 31, 32, 33, 42] {
        let harness = get_harness(VALIDATOR_COUNT);
        let chain_segment = get_chain_segment().await;
        let blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
            .into_iter()
            .map(|block| block.into())
            .collect();

        harness
            .chain
            .slot_clock
            .set_slot(blocks.last().unwrap().slot().as_u64());

        for chunk in blocks.chunks(*chunk_size) {
            harness
                .chain
                .process_chain_segment(
                    chunk.to_vec(),
                    CountUnrealized::True,
                    NotifyExecutionLayer::Yes,
                )
                .await
                .into_block_error()
                .unwrap_or_else(|_| panic!("should import chain segment of len {}", chunk_size));
        }

        harness.chain.recompute_head_at_current_slot().await;

        assert_eq!(
            harness.head_block_root(),
            blocks.last().unwrap().block().canonical_root(),
            "harness should have last block as head"
        );
    }
}

#[tokio::test]
async fn chain_segment_non_linear_parent_roots() {
    let harness = get_harness(VALIDATOR_COUNT);
    let chain_segment = get_chain_segment().await;

    harness
        .chain
        .slot_clock
        .set_slot(chain_segment.last().unwrap().beacon_block.slot().as_u64());

    /*
     * Test with a block removed.
     */
    let mut blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
        .into_iter()
        .map(|block| block.into())
        .collect();
    blocks.remove(2);

    assert!(
        matches!(
            harness
                .chain
                .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                .await
                .into_block_error(),
            Err(BlockError::NonLinearParentRoots)
        ),
        "should not import chain with missing parent"
    );

    /*
     * Test with a modified parent root.
     */
    let mut blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
        .into_iter()
        .map(|block| block.into())
        .collect();
    let (mut block, signature) = blocks[3].block().clone().deconstruct();
    *block.parent_root_mut() = Hash256::zero();
    blocks[3] = Arc::new(SignedBeaconBlock::from_block(block, signature)).into();

    assert!(
        matches!(
            harness
                .chain
                .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                .await
                .into_block_error(),
            Err(BlockError::NonLinearParentRoots)
        ),
        "should not import chain with a broken parent root link"
    );
}

#[tokio::test]
async fn chain_segment_non_linear_slots() {
    let harness = get_harness(VALIDATOR_COUNT);
    let chain_segment = get_chain_segment().await;
    harness
        .chain
        .slot_clock
        .set_slot(chain_segment.last().unwrap().beacon_block.slot().as_u64());

    /*
     * Test where a child is lower than the parent.
     */

    let mut blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
        .into_iter()
        .map(|block| block.into())
        .collect();
    let (mut block, signature) = blocks[3].block().clone().deconstruct();
    *block.slot_mut() = Slot::new(0);
    blocks[3] = Arc::new(SignedBeaconBlock::from_block(block, signature)).into();

    assert!(
        matches!(
            harness
                .chain
                .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                .await
                .into_block_error(),
            Err(BlockError::NonLinearSlots)
        ),
        "should not import chain with a parent that has a lower slot than its child"
    );

    /*
     * Test where a child is equal to the parent.
     */

    let mut blocks: Vec<BlockWrapper<E>> = chain_segment_blocks(&chain_segment)
        .into_iter()
        .map(|block| block.into())
        .collect();
    let (mut block, signature) = blocks[3].block().clone().deconstruct();
    *block.slot_mut() = blocks[2].slot();
    blocks[3] = Arc::new(SignedBeaconBlock::from_block(block, signature)).into();

    assert!(
        matches!(
            harness
                .chain
                .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                .await
                .into_block_error(),
            Err(BlockError::NonLinearSlots)
        ),
        "should not import chain with a parent that has an equal slot to its child"
    );
}

async fn assert_invalid_signature(
    chain_segment: &[BeaconSnapshot<E>],
    harness: &BeaconChainHarness<EphemeralTestingSlotClockHarnessType<E>>,
    block_index: usize,
    snapshots: &[BeaconSnapshot<E>],
    item: &str,
) {
    let blocks: Vec<BlockWrapper<E>> = snapshots
        .iter()
        .map(|snapshot| snapshot.beacon_block.clone().into())
        .collect();

    // Ensure the block will be rejected if imported in a chain segment.
    assert!(
        matches!(
            harness
                .chain
                .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                .await
                .into_block_error(),
            Err(BlockError::InvalidSignature)
        ),
        "should not import chain segment with an invalid {} signature",
        item
    );

    // Call fork choice to update cached head (including finalization).
    harness.chain.recompute_head_at_current_slot().await;

    // Ensure the block will be rejected if imported on its own (without gossip checking).
    let ancestor_blocks = chain_segment
        .iter()
        .take(block_index)
        .map(|snapshot| snapshot.beacon_block.clone().into())
        .collect();
    // We don't care if this fails, we just call this to ensure that all prior blocks have been
    // imported prior to this test.
    let _ = harness
        .chain
        .process_chain_segment(
            ancestor_blocks,
            CountUnrealized::True,
            NotifyExecutionLayer::Yes,
        )
        .await;
    harness.chain.recompute_head_at_current_slot().await;

    let process_res = harness
        .chain
        .process_block(
            snapshots[block_index].beacon_block.canonical_root(),
            snapshots[block_index].beacon_block.clone(),
            CountUnrealized::True,
            NotifyExecutionLayer::Yes,
        )
        .await;
    assert!(
        matches!(process_res, Err(BlockError::InvalidSignature)),
        "should not import individual block with an invalid {} signature, got: {:?}",
        item,
        process_res
    );

    // NOTE: we choose not to check gossip verification here. It only checks one signature
    // (proposal) and that is already tested elsewhere in this file.
    //
    // It's not trivial to just check gossip verification since it will start refusing
    // blocks as soon as it has seen one valid proposal signature for a given (validator,
    // slot) tuple.
}

async fn get_invalid_sigs_harness(
    chain_segment: &[BeaconSnapshot<E>],
) -> BeaconChainHarness<EphemeralTestingSlotClockHarnessType<E>> {
    let harness = get_harness(VALIDATOR_COUNT);
    harness
        .chain
        .slot_clock
        .set_slot(chain_segment.last().unwrap().beacon_block.slot().as_u64());
    harness
}
#[tokio::test]
async fn invalid_signature_gossip_block() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        // Ensure the block will be rejected if imported on its own (without gossip checking).
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let (block, _) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        snapshots[block_index].beacon_block = Arc::new(SignedBeaconBlock::from_block(
            block.clone(),
            junk_signature(),
        ));
        // Import all the ancestors before the `block_index` block.
        let ancestor_blocks = chain_segment
            .iter()
            .take(block_index)
            .map(|snapshot| snapshot.beacon_block.clone().into())
            .collect();
        harness
            .chain
            .process_chain_segment(
                ancestor_blocks,
                CountUnrealized::True,
                NotifyExecutionLayer::Yes,
            )
            .await
            .into_block_error()
            .expect("should import all blocks prior to the one being tested");
        let signed_block = SignedBeaconBlock::from_block(block, junk_signature());
        assert!(
            matches!(
                harness
                    .chain
                    .process_block(
                        signed_block.canonical_root(),
                        Arc::new(signed_block),
                        CountUnrealized::True,
                        NotifyExecutionLayer::Yes,
                    )
                    .await,
                Err(BlockError::InvalidSignature)
            ),
            "should not import individual block with an invalid gossip signature",
        );
    }
}

#[tokio::test]
async fn invalid_signature_block_proposal() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let (block, _) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        snapshots[block_index].beacon_block = Arc::new(SignedBeaconBlock::from_block(
            block.clone(),
            junk_signature(),
        ));
        let blocks: Vec<BlockWrapper<E>> = snapshots
            .iter()
            .map(|snapshot| snapshot.beacon_block.clone().into())
            .collect::<Vec<_>>();
        // Ensure the block will be rejected if imported in a chain segment.
        assert!(
            matches!(
                harness
                    .chain
                    .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                    .await
                    .into_block_error(),
                Err(BlockError::InvalidSignature)
            ),
            "should not import chain segment with an invalid block signature",
        );
    }
}

#[tokio::test]
async fn invalid_signature_randao_reveal() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        *block.body_mut().randao_reveal_mut() = junk_signature();
        snapshots[block_index].beacon_block =
            Arc::new(SignedBeaconBlock::from_block(block, signature));
        update_parent_roots(&mut snapshots);
        update_proposal_signatures(&mut snapshots, &harness);
        assert_invalid_signature(&chain_segment, &harness, block_index, &snapshots, "randao").await;
    }
}

#[tokio::test]
async fn invalid_signature_proposer_slashing() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        let proposer_slashing = ProposerSlashing {
            signed_header_1: SignedBeaconBlockHeader {
                message: block.block_header(),
                signature: junk_signature(),
            },
            signed_header_2: SignedBeaconBlockHeader {
                message: block.block_header(),
                signature: junk_signature(),
            },
        };
        block
            .body_mut()
            .proposer_slashings_mut()
            .push(proposer_slashing)
            .expect("should update proposer slashing");
        snapshots[block_index].beacon_block =
            Arc::new(SignedBeaconBlock::from_block(block, signature));
        update_parent_roots(&mut snapshots);
        update_proposal_signatures(&mut snapshots, &harness);
        assert_invalid_signature(
            &chain_segment,
            &harness,
            block_index,
            &snapshots,
            "proposer slashing",
        )
        .await;
    }
}

#[tokio::test]
async fn invalid_signature_attester_slashing() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let indexed_attestation = IndexedAttestation {
            attesting_indices: vec![0].into(),
            data: AttestationData {
                slot: Slot::new(0),
                index: 0,
                beacon_block_root: Hash256::zero(),
                source: Checkpoint {
                    epoch: Epoch::new(0),
                    root: Hash256::zero(),
                },
                target: Checkpoint {
                    epoch: Epoch::new(0),
                    root: Hash256::zero(),
                },
            },
            signature: junk_aggregate_signature(),
        };
        let attester_slashing = AttesterSlashing {
            attestation_1: indexed_attestation.clone(),
            attestation_2: indexed_attestation,
        };
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        block
            .body_mut()
            .attester_slashings_mut()
            .push(attester_slashing)
            .expect("should update attester slashing");
        snapshots[block_index].beacon_block =
            Arc::new(SignedBeaconBlock::from_block(block, signature));
        update_parent_roots(&mut snapshots);
        update_proposal_signatures(&mut snapshots, &harness);
        assert_invalid_signature(
            &chain_segment,
            &harness,
            block_index,
            &snapshots,
            "attester slashing",
        )
        .await;
    }
}

#[tokio::test]
async fn invalid_signature_attestation() {
    let chain_segment = get_chain_segment().await;
    let mut checked_attestation = false;

    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        if let Some(attestation) = block.body_mut().attestations_mut().get_mut(0) {
            attestation.signature = junk_aggregate_signature();
            snapshots[block_index].beacon_block =
                Arc::new(SignedBeaconBlock::from_block(block, signature));
            update_parent_roots(&mut snapshots);
            update_proposal_signatures(&mut snapshots, &harness);
            assert_invalid_signature(
                &chain_segment,
                &harness,
                block_index,
                &snapshots,
                "attestation",
            )
            .await;
            checked_attestation = true;
        }
    }

    assert!(
        checked_attestation,
        "the test should check an attestation signature"
    )
}

#[tokio::test]
async fn invalid_signature_deposit() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        // Note: an invalid deposit signature is permitted!
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let deposit = Deposit {
            proof: vec![Hash256::zero(); DEPOSIT_TREE_DEPTH + 1].into(),
            data: DepositData {
                pubkey: Keypair::random().pk.into(),
                withdrawal_credentials: Hash256::zero(),
                amount: 0,
                signature: junk_signature().into(),
            },
        };
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        block
            .body_mut()
            .deposits_mut()
            .push(deposit)
            .expect("should update deposit");
        snapshots[block_index].beacon_block =
            Arc::new(SignedBeaconBlock::from_block(block, signature));
        update_parent_roots(&mut snapshots);
        update_proposal_signatures(&mut snapshots, &harness);
        let blocks: Vec<BlockWrapper<E>> = snapshots
            .iter()
            .map(|snapshot| snapshot.beacon_block.clone().into())
            .collect();
        assert!(
            !matches!(
                harness
                    .chain
                    .process_chain_segment(blocks, CountUnrealized::True, NotifyExecutionLayer::Yes)
                    .await
                    .into_block_error(),
                Err(BlockError::InvalidSignature)
            ),
            "should not throw an invalid signature error for a bad deposit signature"
        );
    }
}

#[tokio::test]
async fn invalid_signature_exit() {
    let chain_segment = get_chain_segment().await;
    for &block_index in BLOCK_INDICES {
        let harness = get_invalid_sigs_harness(&chain_segment).await;
        let mut snapshots = chain_segment.clone();
        let epoch = snapshots[block_index].beacon_state.current_epoch();
        let (mut block, signature) = snapshots[block_index]
            .beacon_block
            .as_ref()
            .clone()
            .deconstruct();
        block
            .body_mut()
            .voluntary_exits_mut()
            .push(SignedVoluntaryExit {
                message: VoluntaryExit {
                    epoch,
                    validator_index: 0,
                },
                signature: junk_signature(),
            })
            .expect("should update deposit");
        snapshots[block_index].beacon_block =
            Arc::new(SignedBeaconBlock::from_block(block, signature));
        update_parent_roots(&mut snapshots);
        update_proposal_signatures(&mut snapshots, &harness);
        assert_invalid_signature(
            &chain_segment,
            &harness,
            block_index,
            &snapshots,
            "voluntary exit",
        )
        .await;
    }
}

fn unwrap_err<T, E>(result: Result<T, E>) -> E {
    match result {
        Ok(_) => panic!("called unwrap_err on Ok"),
        Err(e) => e,
    }
}

#[tokio::test]
async fn block_gossip_verification() {
    let harness = get_harness(VALIDATOR_COUNT);
    let chain_segment = get_chain_segment().await;

    let block_index = CHAIN_SEGMENT_LENGTH - 2;

    harness
        .chain
        .slot_clock
        .set_slot(chain_segment[block_index].beacon_block.slot().as_u64());

    // Import the ancestors prior to the block we're testing.
    for snapshot in &chain_segment[0..block_index] {
        let gossip_verified = harness
            .chain
            .verify_block_for_gossip(snapshot.beacon_block.clone().into())
            .await
            .expect("should obtain gossip verified block");

        harness
            .chain
            .process_block(
                gossip_verified.block_root,
                gossip_verified,
                CountUnrealized::True,
                NotifyExecutionLayer::Yes,
            )
            .await
            .expect("should import valid gossip verified block");
    }

    // Recompute the head to ensure we cache the latest view of fork choice.
    harness.chain.recompute_head_at_current_slot().await;

    /*
     * This test ensures that:
     *
     * Spec v0.12.1
     *
     * The block is not from a future slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance) --
     * i.e. validate that signed_beacon_block.message.slot <= current_slot (a client MAY queue
     * future blocks for processing at the appropriate slot).
     */

    let (mut block, signature) = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct();
    let expected_block_slot = block.slot() + 1;
    *block.slot_mut() = expected_block_slot;
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(SignedBeaconBlock::from_block(block, signature)).into()).await),
            BlockError::FutureSlot {
                present_slot,
                block_slot,
            }
            if present_slot == expected_block_slot - 1 && block_slot == expected_block_slot
        ),
        "should not import a block with a future slot"
    );

    /*
     * This test ensure that:
     *
     * Spec v0.12.1
     *
     * The block is from a slot greater than the latest finalized slot -- i.e. validate that
     * signed_beacon_block.message.slot >
     * compute_start_slot_at_epoch(state.finalized_checkpoint.epoch) (a client MAY choose to
     * validate and store such blocks for additional purposes -- e.g. slashing detection, archive
     * nodes, etc).
     */

    let (mut block, signature) = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct();
    let expected_finalized_slot = harness
        .finalized_checkpoint()
        .epoch
        .start_slot(E::slots_per_epoch());
    *block.slot_mut() = expected_finalized_slot;
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(SignedBeaconBlock::from_block(block, signature)).into()).await),
            BlockError::WouldRevertFinalizedSlot {
                block_slot,
                finalized_slot,
            }
            if block_slot == expected_finalized_slot && finalized_slot == expected_finalized_slot
        ),
        "should not import a block with a finalized slot"
    );

    /*
     * This test ensures that:
     *
     * Spec v0.12.1
     *
     * The proposer signature, signed_beacon_block.signature, is valid with respect to the
     * proposer_index pubkey.
     */

    let block = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct()
        .0;
    assert!(
        matches!(
            unwrap_err(
                harness
                    .chain
                    .verify_block_for_gossip(
                        Arc::new(SignedBeaconBlock::from_block(block, junk_signature())).into()
                    )
                    .await
            ),
            BlockError::ProposalSignatureInvalid
        ),
        "should not import a block with an invalid proposal signature"
    );

    /*
     * This test ensures that:
     *
     * Spec v0.12.2
     *
     * The block's parent (defined by block.parent_root) passes validation.
     */

    let (mut block, signature) = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct();
    let parent_root = Hash256::from_low_u64_be(42);
    *block.parent_root_mut() = parent_root;
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(SignedBeaconBlock::from_block(block, signature)).into()).await),
            BlockError::ParentUnknown(block)
            if block.parent_root() == parent_root
        ),
        "should not import a block for an unknown parent"
    );

    /*
     * This test ensures that:
     *
     * Spec v0.12.2
     *
     * The current finalized_checkpoint is an ancestor of block -- i.e. get_ancestor(store,
     * block.parent_root, compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)) ==
     * store.finalized_checkpoint.root
     */

    let (mut block, signature) = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct();
    let parent_root = chain_segment[0].beacon_block_root;
    *block.parent_root_mut() = parent_root;
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(SignedBeaconBlock::from_block(block, signature)).into()).await),
            BlockError::NotFinalizedDescendant { block_parent_root }
            if block_parent_root == parent_root
        ),
        "should not import a block that conflicts with finality"
    );

    /*
     * This test ensures that:
     *
     * Spec v0.12.1
     *
     * The block is proposed by the expected proposer_index for the block's slot in the context of
     * the current shuffling (defined by parent_root/slot). If the proposer_index cannot
     * immediately be verified against the expected shuffling, the block MAY be queued for later
     * processing while proposers for the block's branch are calculated.
     */

    let mut block = chain_segment[block_index]
        .beacon_block
        .as_ref()
        .clone()
        .deconstruct()
        .0;
    let expected_proposer = block.proposer_index();
    let other_proposer = (0..VALIDATOR_COUNT as u64)
        .into_iter()
        .find(|i| *i != block.proposer_index())
        .expect("there must be more than one validator in this test");
    *block.proposer_index_mut() = other_proposer;
    let block = block.sign(
        &generate_deterministic_keypair(other_proposer as usize).sk,
        &harness.chain.canonical_head.cached_head().head_fork(),
        harness.chain.genesis_validators_root,
        &harness.chain.spec,
    );
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(block.clone()).into()).await),
            BlockError::IncorrectBlockProposer {
                block,
                local_shuffling,
            }
            if block == other_proposer && local_shuffling == expected_proposer
        ),
        "should not import a block with the wrong proposer index"
    );
    // Check to ensure that we registered this is a valid block from this proposer.
    assert!(
        matches!(
            unwrap_err(harness.chain.verify_block_for_gossip(Arc::new(block.clone()).into()).await),
            BlockError::RepeatProposal {
                proposer,
                slot,
            }
            if proposer == other_proposer && slot == block.message().slot()
        ),
        "should register any valid signature against the proposer, even if the block failed later verification"
    );

    let block = chain_segment[block_index].beacon_block.clone();
    assert!(
        harness
            .chain
            .verify_block_for_gossip(block.into())
            .await
            .is_ok(),
        "the valid block should be processed"
    );

    /*
     * This test ensures that:
     *
     * Spec v0.12.1
     *
     * The block is the first block with valid signature received for the proposer for the slot,
     * signed_beacon_block.message.slot.
     */

    let block = chain_segment[block_index].beacon_block.clone();
    assert!(
        matches!(
            harness
                .chain
                .verify_block_for_gossip(block.clone().into())
                .await
                .err()
                .expect("should error when processing known block"),
            BlockError::RepeatProposal {
                proposer,
                slot,
            }
            if proposer == block.message().proposer_index() && slot == block.message().slot()
        ),
        "the second proposal by this validator should be rejected"
    );
}

#[tokio::test]
async fn verify_block_for_gossip_slashing_detection() {
    let slasher_dir = tempdir().unwrap();
    let slasher = Arc::new(
        Slasher::open(SlasherConfig::new(slasher_dir.path().into()), test_logger()).unwrap(),
    );

    let inner_slasher = slasher.clone();
    let harness = BeaconChainHarness::builder(MainnetEthSpec)
        .default_spec()
        .keypairs(KEYPAIRS.to_vec())
        .fresh_ephemeral_store()
        .initial_mutator(Box::new(move |builder| builder.slasher(inner_slasher)))
        .mock_execution_layer()
        .build();
    harness.advance_slot();

    let state = harness.get_current_state();
    let (block1, _) = harness.make_block(state.clone(), Slot::new(1)).await;
    let (block2, _) = harness.make_block(state, Slot::new(1)).await;

    let verified_block = harness
        .chain
        .verify_block_for_gossip(Arc::new(block1).into())
        .await
        .unwrap();
    harness
        .chain
        .process_block(
            verified_block.block_root,
            verified_block,
            CountUnrealized::True,
            NotifyExecutionLayer::Yes,
        )
        .await
        .unwrap();
    unwrap_err(
        harness
            .chain
            .verify_block_for_gossip(Arc::new(block2).into())
            .await,
    );

    // Slasher should have been handed the two conflicting blocks and crafted a slashing.
    slasher.process_queued(Epoch::new(0)).unwrap();
    let proposer_slashings = slasher.get_proposer_slashings();
    assert_eq!(proposer_slashings.len(), 1);
    // windows won't delete the temporary directory if you don't do this..
    drop(harness);
    drop(slasher);
    slasher_dir.close().unwrap();
}

#[tokio::test]
async fn verify_block_for_gossip_doppelganger_detection() {
    let harness = get_harness(VALIDATOR_COUNT);

    let state = harness.get_current_state();
    let (block, _) = harness.make_block(state.clone(), Slot::new(1)).await;

    let verified_block = harness
        .chain
        .verify_block_for_gossip(Arc::new(block).into())
        .await
        .unwrap();
    let attestations = verified_block.block.message().body().attestations().clone();
    harness
        .chain
        .process_block(
            verified_block.block_root,
            verified_block,
            CountUnrealized::True,
            NotifyExecutionLayer::Yes,
        )
        .await
        .unwrap();

    for att in attestations.iter() {
        let epoch = att.data.target.epoch;
        let committee = state
            .get_beacon_committee(att.data.slot, att.data.index)
            .unwrap();
        let indexed_attestation = get_indexed_attestation(committee.committee, att).unwrap();

        for &index in &indexed_attestation.attesting_indices {
            let index = index as usize;

            assert!(harness.chain.validator_seen_at_epoch(index, epoch));

            // Check the correct beacon cache is populated
            assert!(harness
                .chain
                .observed_block_attesters
                .read()
                .validator_has_been_observed(epoch, index)
                .expect("should check if block attester was observed"));
            assert!(!harness
                .chain
                .observed_gossip_attesters
                .read()
                .validator_has_been_observed(epoch, index)
                .expect("should check if gossip attester was observed"));
            assert!(!harness
                .chain
                .observed_aggregators
                .read()
                .validator_has_been_observed(epoch, index)
                .expect("should check if gossip aggregator was observed"));
        }
    }
}

#[tokio::test]
async fn add_base_block_to_altair_chain() {
    let mut spec = MainnetEthSpec::default_spec();
    let slots_per_epoch = MainnetEthSpec::slots_per_epoch();

    // The Altair fork happens at epoch 1.
    spec.altair_fork_epoch = Some(Epoch::new(1));

    let harness = BeaconChainHarness::builder(MainnetEthSpec)
        .spec(spec)
        .keypairs(KEYPAIRS[..].to_vec())
        .fresh_ephemeral_store()
        .mock_execution_layer()
        .build();

    // Move out of the genesis slot.
    harness.advance_slot();

    // Build out all the blocks in epoch 0.
    harness
        .extend_chain(
            slots_per_epoch as usize,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::AllValidators,
        )
        .await;

    // Move into the next empty slot.
    harness.advance_slot();

    // Produce an Altair block.
    let state = harness.get_current_state();
    let slot = harness.get_current_slot();
    let (altair_signed_block, _) = harness.make_block(state.clone(), slot).await;
    let altair_block = &altair_signed_block
        .as_altair()
        .expect("test expects an altair block")
        .message;
    let altair_body = &altair_block.body;

    // Create a Base-equivalent of `altair_block`.
    let base_block = SignedBeaconBlock::Base(SignedBeaconBlockBase {
        message: BeaconBlockBase {
            slot: altair_block.slot,
            proposer_index: altair_block.proposer_index,
            parent_root: altair_block.parent_root,
            state_root: altair_block.state_root,
            body: BeaconBlockBodyBase {
                randao_reveal: altair_body.randao_reveal.clone(),
                eth1_data: altair_body.eth1_data.clone(),
                graffiti: altair_body.graffiti,
                proposer_slashings: altair_body.proposer_slashings.clone(),
                attester_slashings: altair_body.attester_slashings.clone(),
                attestations: altair_body.attestations.clone(),
                deposits: altair_body.deposits.clone(),
                voluntary_exits: altair_body.voluntary_exits.clone(),
                _phantom: PhantomData,
            },
        },
        signature: Signature::empty(),
    });

    // Ensure that it would be impossible to apply this block to `per_block_processing`.
    {
        let mut state = state;
        let mut ctxt = ConsensusContext::new(base_block.slot());
        per_slot_processing(&mut state, None, &harness.chain.spec).unwrap();
        assert!(matches!(
            per_block_processing(
                &mut state,
                &base_block,
                BlockSignatureStrategy::NoVerification,
                VerifyBlockRoot::True,
                &mut ctxt,
                &harness.chain.spec,
            ),
            Err(BlockProcessingError::InconsistentBlockFork(
                InconsistentFork {
                    fork_at_slot: ForkName::Altair,
                    object_fork: ForkName::Base,
                }
            ))
        ));
    }

    // Ensure that it would be impossible to verify this block for gossip.
    assert!(matches!(
        harness
            .chain
            .verify_block_for_gossip(Arc::new(base_block.clone()).into())
            .await
            .err()
            .expect("should error when processing base block"),
        BlockError::InconsistentFork(InconsistentFork {
            fork_at_slot: ForkName::Altair,
            object_fork: ForkName::Base,
        })
    ));

    // Ensure that it would be impossible to import via `BeaconChain::process_block`.
    assert!(matches!(
        harness
            .chain
            .process_block(
                base_block.canonical_root(),
                Arc::new(base_block.clone()),
                CountUnrealized::True,
                NotifyExecutionLayer::Yes,
            )
            .await
            .err()
            .expect("should error when processing base block"),
        BlockError::InconsistentFork(InconsistentFork {
            fork_at_slot: ForkName::Altair,
            object_fork: ForkName::Base,
        })
    ));

    // Ensure that it would be impossible to import via `BeaconChain::process_chain_segment`.
    assert!(matches!(
        harness
            .chain
            .process_chain_segment(
                vec![Arc::new(base_block).into()],
                CountUnrealized::True,
                NotifyExecutionLayer::Yes,
            )
            .await,
        ChainSegmentResult::Failed {
            imported_blocks: 0,
            error: BlockError::InconsistentFork(InconsistentFork {
                fork_at_slot: ForkName::Altair,
                object_fork: ForkName::Base,
            })
        }
    ));
}

#[tokio::test]
async fn add_altair_block_to_base_chain() {
    let mut spec = MainnetEthSpec::default_spec();

    // Altair never happens.
    spec.altair_fork_epoch = None;

    let harness = BeaconChainHarness::builder(MainnetEthSpec)
        .spec(spec)
        .keypairs(KEYPAIRS[..].to_vec())
        .fresh_ephemeral_store()
        .mock_execution_layer()
        .build();

    // Move out of the genesis slot.
    harness.advance_slot();

    // Build one block.
    harness
        .extend_chain(
            1,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::AllValidators,
        )
        .await;

    // Move into the next empty slot.
    harness.advance_slot();

    // Produce an altair block.
    let state = harness.get_current_state();
    let slot = harness.get_current_slot();
    let (base_signed_block, _) = harness.make_block(state.clone(), slot).await;
    let base_block = &base_signed_block
        .as_base()
        .expect("test expects a base block")
        .message;
    let base_body = &base_block.body;

    // Create an Altair-equivalent of `altair_block`.
    let altair_block = SignedBeaconBlock::Altair(SignedBeaconBlockAltair {
        message: BeaconBlockAltair {
            slot: base_block.slot,
            proposer_index: base_block.proposer_index,
            parent_root: base_block.parent_root,
            state_root: base_block.state_root,
            body: BeaconBlockBodyAltair {
                randao_reveal: base_body.randao_reveal.clone(),
                eth1_data: base_body.eth1_data.clone(),
                graffiti: base_body.graffiti,
                proposer_slashings: base_body.proposer_slashings.clone(),
                attester_slashings: base_body.attester_slashings.clone(),
                attestations: base_body.attestations.clone(),
                deposits: base_body.deposits.clone(),
                voluntary_exits: base_body.voluntary_exits.clone(),
                sync_aggregate: SyncAggregate::empty(),
                _phantom: PhantomData,
            },
        },
        signature: Signature::empty(),
    });

    // Ensure that it would be impossible to apply this block to `per_block_processing`.
    {
        let mut state = state;
        let mut ctxt = ConsensusContext::new(altair_block.slot());
        per_slot_processing(&mut state, None, &harness.chain.spec).unwrap();
        assert!(matches!(
            per_block_processing(
                &mut state,
                &altair_block,
                BlockSignatureStrategy::NoVerification,
                VerifyBlockRoot::True,
                &mut ctxt,
                &harness.chain.spec,
            ),
            Err(BlockProcessingError::InconsistentBlockFork(
                InconsistentFork {
                    fork_at_slot: ForkName::Base,
                    object_fork: ForkName::Altair,
                }
            ))
        ));
    }

    // Ensure that it would be impossible to verify this block for gossip.
    assert!(matches!(
        harness
            .chain
            .verify_block_for_gossip(Arc::new(altair_block.clone()).into())
            .await
            .err()
            .expect("should error when processing altair block"),
        BlockError::InconsistentFork(InconsistentFork {
            fork_at_slot: ForkName::Base,
            object_fork: ForkName::Altair,
        })
    ));

    // Ensure that it would be impossible to import via `BeaconChain::process_block`.
    assert!(matches!(
        harness
            .chain
            .process_block(
                altair_block.canonical_root(),
                Arc::new(altair_block.clone()),
                CountUnrealized::True,
                NotifyExecutionLayer::Yes,
            )
            .await
            .err()
            .expect("should error when processing altair block"),
        BlockError::InconsistentFork(InconsistentFork {
            fork_at_slot: ForkName::Base,
            object_fork: ForkName::Altair,
        })
    ));

    // Ensure that it would be impossible to import via `BeaconChain::process_chain_segment`.
    assert!(matches!(
        harness
            .chain
            .process_chain_segment(
                vec![Arc::new(altair_block).into()],
                CountUnrealized::True,
                NotifyExecutionLayer::Yes
            )
            .await,
        ChainSegmentResult::Failed {
            imported_blocks: 0,
            error: BlockError::InconsistentFork(InconsistentFork {
                fork_at_slot: ForkName::Base,
                object_fork: ForkName::Altair,
            })
        }
    ));
}