feat: implements process bls to execution change

ethereum-consensus/src/capella/block_processing.rs

@@ -1,17 +1,20 @@
 use crate::{
     capella::{
-        compute_timestamp_at_slot, decrease_balance, get_current_epoch, get_randao_mix,
-        is_fully_withdrawable_validator, is_partially_withdrawable_validator, process_attestation,
-        process_attester_slashing, process_block_header, process_deposit, process_eth1_data,
-        process_proposer_slashing, process_randao, process_sync_aggregate, process_voluntary_exit,
-        BeaconBlock, BeaconBlockBody, BeaconState, ExecutionAddress, ExecutionEngine,
+        compute_domain, compute_signing_root, compute_timestamp_at_slot, decrease_balance,
+        get_current_epoch, get_randao_mix, is_fully_withdrawable_validator,
+        is_partially_withdrawable_validator, process_attestation, process_attester_slashing,
+        process_block_header, process_deposit, process_eth1_data, process_proposer_slashing,
+        process_randao, process_sync_aggregate, process_voluntary_exit, BeaconBlock,
+        BeaconBlockBody, BeaconState, DomainType, ExecutionAddress, ExecutionEngine,
         ExecutionPayload, ExecutionPayloadHeader, NewPayloadRequest, SignedBlsToExecutionChange,
         Withdrawal,
     },
+    crypto::{hash, verify_signature},
+    primitives::{BLS_WITHDRAWAL_PREFIX, ETH1_ADDRESS_WITHDRAWAL_PREFIX},
     ssz::prelude::*,
     state_transition::{
-        invalid_operation_error, Context, InvalidDeposit, InvalidExecutionPayload,
-        InvalidOperation, InvalidWithdrawals, Result,
+        invalid_operation_error, Context, InvalidBlsToExecutionChange, InvalidDeposit,
+        InvalidExecutionPayload, InvalidOperation, InvalidWithdrawals, Result,
     },
 };
 
@@ -27,7 +30,7 @@ pub fn process_bls_to_execution_change<
     const BYTES_PER_LOGS_BLOOM: usize,
     const MAX_EXTRA_DATA_BYTES: usize,
 >(
-    _state: &mut BeaconState<
+    state: &mut BeaconState<
         SLOTS_PER_HISTORICAL_ROOT,
         HISTORICAL_ROOTS_LIMIT,
         ETH1_DATA_VOTES_BOUND,
@@ -39,10 +42,49 @@ pub fn process_bls_to_execution_change<
         BYTES_PER_LOGS_BLOOM,
         MAX_EXTRA_DATA_BYTES,
     >,
-    _signed_address_change: &mut SignedBlsToExecutionChange,
-    _context: &Context,
+    signed_address_change: &mut SignedBlsToExecutionChange,
+    context: &Context,
 ) -> Result<()> {
-    unimplemented!()
+    let address_change = &mut signed_address_change.message;
+    let signature = &signed_address_change.signature;
+
+    if address_change.validator_index >= state.validators.len() {
+        return Err(invalid_operation_error(InvalidOperation::BlsToExecutionChange(
+            InvalidBlsToExecutionChange::ValidatorIndexOutOfBounds(address_change.validator_index),
+        )))
+    }
+
+    let validator = &mut state.validators[address_change.validator_index];
+    let withdrawal_credentials = &mut validator.withdrawal_credentials;
+    if withdrawal_credentials[0] != BLS_WITHDRAWAL_PREFIX {
+        return Err(invalid_operation_error(InvalidOperation::BlsToExecutionChange(
+            InvalidBlsToExecutionChange::WithdrawalCredentialsPrefix(withdrawal_credentials[0]),
+        )))
+    }
+
+    // NOTE: compute `signing_root` ahead of the public key check to satisfy borrow check
+    let domain = compute_domain(
+        DomainType::BlsToExecutionChange,
+        None,
+        Some(state.genesis_validators_root),
+        context,
+    )?;
+
+    let signing_root = compute_signing_root(address_change, domain)?;
+    let public_key = &address_change.from_bls_public_key;
+    if withdrawal_credentials[1..] != hash(public_key.as_ref())[1..] {
+        return Err(invalid_operation_error(InvalidOperation::BlsToExecutionChange(
+            InvalidBlsToExecutionChange::PublicKeyMismatch(public_key.clone()),
+        )))
+    }
+
+    verify_signature(public_key, signing_root.as_ref(), signature)?;
+
+    withdrawal_credentials[0] = ETH1_ADDRESS_WITHDRAWAL_PREFIX;
+    withdrawal_credentials[1..12].fill(0);
+    withdrawal_credentials[12..].copy_from_slice(address_change.to_execution_address.as_ref());
+
+    Ok(())
 }
 
 pub fn process_operations<

ethereum-consensus/src/capella/bls_to_execution_change.rs

@@ -16,6 +16,6 @@ pub struct BlsToExecutionChange {
 #[derive(Default, Debug, Clone, SimpleSerialize, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct SignedBlsToExecutionChange {
-    message: BlsToExecutionChange,
-    signature: BlsSignature,
+    pub message: BlsToExecutionChange,
+    pub signature: BlsSignature,
 }

ethereum-consensus/src/state_transition/error.rs

@@ -2,7 +2,7 @@ use crate::{
     capella::Withdrawal,
     crypto::Error as CryptoError,
     phase0::{AttestationData, BeaconBlockHeader, Checkpoint},
-    primitives::{BlsSignature, Bytes32, Epoch, Hash32, Root, Slot, ValidatorIndex},
+    primitives::{BlsPublicKey, BlsSignature, Bytes32, Epoch, Hash32, Root, Slot, ValidatorIndex},
     ssz::prelude::*,
     state_transition::Forks,
 };
@@ -87,6 +87,8 @@ pub enum InvalidOperation {
     ExecutionPayload(#[from] InvalidExecutionPayload),
     #[error("invalid withdrawals: {0}")]
     Withdrawal(#[from] InvalidWithdrawals),
+    #[error("invalid bls signature to execution change: {0}")]
+    BlsToExecutionChange(#[from] InvalidBlsToExecutionChange),
 }
 
 #[derive(Debug, Error)]
@@ -189,6 +191,16 @@ pub enum InvalidWithdrawals {
     IncorrectWithdrawals { provided: Vec<Withdrawal>, expected: Vec<Withdrawal> },
 }
 
+#[derive(Debug, Error)]
+pub enum InvalidBlsToExecutionChange {
+    #[error("validator index {0} is out of bounds")]
+    ValidatorIndexOutOfBounds(usize),
+    #[error("invalid withdrawal credentials prefix: {0}")]
+    WithdrawalCredentialsPrefix(u8),
+    #[error("operation's public key did not match the registered key: {0:?}")]
+    PublicKeyMismatch(BlsPublicKey),
+}
+
 #[derive(Debug, Error)]
 pub enum InvalidSyncAggregate {
     #[error("invalid sync committee aggregate signature {signature} signing over previous slot block root {root}")]