wip 00 to 01 cred change

specs/capella/beacon-chain.md

@@ -20,14 +20,20 @@ to validator withdrawals. Including:
 
 ## Custom types
 
-## Constants
-
 We define the following Python custom types for type hinting and readability:
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
 | `WithdrawalIndex` | `uint64` | an index of a `Withdrawal`|
 
+## Constants
+
+### Domain types
+
+| Name | Value |
+| - | - |
+| `DOMAIN_BLS_TO_EXECUTION_CHANGE` | `DomainType('0x0A000000')` |
+
 ## Preset
 
 ### State list lengths
@@ -36,6 +42,12 @@ We define the following Python custom types for type hinting and readability:
 | - | - | :-: | :-: |
 | `WITHDRAWALS_QUEUE_LIMIT` | `uint64(2**40)` (= 1,099,511,627,776) | withdrawals enqueued in state|
 
+### Max operations per block
+
+| Name | Value |
+| - | - |
+| `MAX_BLS_TO_EXECUTION_CHANGES` | `2**4` (= 16) |
+
 ### Execution
 
 | Name | Value | Description |
@@ -64,6 +76,25 @@ class Validator(Container):
     withdrawn_epoch: Epoch  # [New in Capella]
 ```
 
+#### `BeaconBlockBody`
+
+```python
+class BeaconBlockBody(Container):
+    randao_reveal: BLSSignature
+    eth1_data: Eth1Data  # Eth1 data vote
+    graffiti: Bytes32  # Arbitrary data
+    # Operations
+    proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
+    attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
+    attestations: List[Attestation, MAX_ATTESTATIONS]
+    deposits: List[Deposit, MAX_DEPOSITS]
+    voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
+    bls_to_execution_changes: List[SignedBLSToExecutionChange, MAX_BLS_TO_EXECUTION_CHANGES]
+    sync_aggregate: SyncAggregate
+    # Execution
+    execution_payload: ExecutionPayload
+```
+
 #### `BeaconState`
 
 ```python
@@ -166,6 +197,23 @@ class Withdrawal(Container):
     amount: Gwei
 ```
 
+#### `BLSToExecutionChange`
+
+```python
+class BLSToExecutionChange(Container):
+    validator_index: ValidatorIndex
+    from_bls_pubkey: BLSPubkey
+    to_execution_address: ExecutionAddress
+```
+
+#### `SignedBLSToExecutionChange`
+
+```python
+class SignedBLSToExecutionChange(Container):
+    message: BLSToExecutionChange
+    signature: BLSSignature
+```
+
 ## Helpers
 
 ### Beacon state mutators
@@ -297,3 +345,49 @@ def process_execution_payload(state: BeaconState, payload: ExecutionPayload, exe
         withdrawals_root=hash_tree_root(payload.withdrawals),
     )
 ```
+
+#### Modified `process_operations`
+
+*Note*: The function `process_operations` is modified to process `BLSToExecutionChange` operations included in the block.
+
+```python
+def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
+    # Verify that outstanding deposits are processed up to the maximum number of deposits
+    assert len(body.deposits) == min(MAX_DEPOSITS, state.eth1_data.deposit_count - state.eth1_deposit_index)
+
+    def for_ops(operations: Sequence[Any], fn: Callable[[BeaconState, Any], None]) -> None:
+        for operation in operations:
+            fn(state, operation)
+
+    for_ops(body.proposer_slashings, process_proposer_slashing)
+    for_ops(body.attester_slashings, process_attester_slashing)
+    for_ops(body.attestations, process_attestation)
+    for_ops(body.deposits, process_deposit)
+    for_ops(body.voluntary_exits, process_voluntary_exit)
+    for_ops(body.bls_to_execution_changes, process_bls_to_execution_change)
+```
+
+#### New `process_bls_to_execution_change`
+
+```python
+def process_bls_to_execution_change(state: BeaconState,
+                                    signed_address_change: SignedBLSToExecutionChange) -> None:
+    address_change = signed_address_change.message
+
+    assert address_change.validator_index < len(state.validators)
+
+    validator = state.validators[address_change.validator_index]
+
+    assert validator.withdrawal_credentials[:1] == BLS_WITHDRAWAL_PREFIX
+    assert validator.withdrawal_credentials[1:] == hash(address_change.from_bls_pubkey)[1:]
+
+    domain = get_domain(state, DOMAIN_BLS_TO_EXECUTION_CHANGE)
+    signing_root = compute_signing_root(address_change, domain)
+    assert bls.Verify(address_change.from_bls_pubkey, signing_root, signed_address_change.signature)
+
+    validator.withdrawal_credentials = (
+        ETH1_ADDRESS_WITHDRAWAL_PREFIX
+        + 0x00 * 11
+        + address_change.to_execution_address
+    )
+```

tests/core/pyspec/eth2spec/test/capella/block_processing/test_process_bls_to_execution_change.py

@@ -0,0 +1,47 @@
+from eth2spec.test.helpers.execution_payload import (
+    build_empty_execution_payload,
+)
+
+from eth2spec.test.context import spec_state_test, expect_assertion_error, with_capella_and_later
+
+def run_bls_to_execution_change_processing(spec, state, address_change, valid=True):
+    """
+    Run ``process_bls_to_execution_change``, yielding:
+      - pre-state ('pre')
+      - address-change ('address_change')
+      - post-state ('post').
+    If ``valid == False``, run expecting ``AssertionError``
+    """
+    # yield pre-state
+    yield 'pre', state
+
+    yield 'address_change', address_change
+
+    # If the address_change is invalid, processing is aborted, and there is no post-state.
+    if not valid:
+        expect_assertion_error(lambda: spec.process_bls_to_execution_change(state, attestation))
+        yield 'post', None
+        return
+
+    # process address change
+    spec.process_bls_to_execution_change(state, attestation)
+
+    # Make sure the address change has been processed
+    assert state.withdrawal_credentials[:1] == ETH1_ADDRESS_WITHDRAWAL_PREFIX
+    assert state.withdrawal_credentials[1:12] == b'\x00' * 11
+    assert state.withdrawal_credentials[12:] == address_change.to_execution_address
+
+    # yield post-state
+    yield 'post', state
+
+
+@with_capella_and_later
+@spec_state_test
+def test_success(spec, state):
+    address_change = spec.BLSToExecutionChange(
+        validator_index=0,
+        from_bls_pubkey=TEST,
+        to_execution_address=b'\x42' * 20,
+    )
+
+    yield from run_bls_to_execution_change_processing(spec, state, address_change)