utilize bls_domain directly for deposits

specs/core/0_beacon-chain.md

@@ -174,6 +174,7 @@ These configurations are updated for releases, but may be out of sync during `de
 | Name | Value |
 | - | - |
 | `DEPOSIT_CONTRACT_TREE_DEPTH` | `2**5` (= 32) |
+| `DEPOSIT_FORK_VERSION` | `b'\x00' * 4` |
 
 ### Gwei values
 
@@ -629,6 +630,16 @@ The `hash` function is SHA256.
 
 `def signing_root(object: SSZContainer) -> Bytes32` is a function defined in the [SimpleSerialize spec](../simple-serialize.md#self-signed-containers) to compute signing messages.
 
+### `bls_domain`
+
+```python
+def bls_domain(domain_type: int, fork_version: bytes) -> int:
+    """
+    Return the bls domain given by the ``domain_type`` and 4 byte ``fork_version``..
+    """
+    return bytes_to_int(int_to_bytes(domain_type, length=4) + fork_version)
+```
+
 ### `slot_to_epoch`
 
 ```python
@@ -968,8 +979,7 @@ def get_domain(state: BeaconState,
     """
     epoch = get_current_epoch(state) if message_epoch is None else message_epoch
     fork_version = state.fork.previous_version if epoch < state.fork.epoch else state.fork.current_version
-    # fork version is on the big-endian side: when signing using only the type (e.g. deposits), the type can be passed directly.
-    return bytes_to_int(int_to_bytes(domain_type, length=4) + fork_version)
+    return bls_domain(domain_type, fork_version)
 ```
 
 ### `get_bitfield_bit`
@@ -1766,8 +1776,10 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
     validator_pubkeys = [v.pubkey for v in state.validator_registry]
     if pubkey not in validator_pubkeys:
         # Verify the deposit signature (proof of possession)
-        # Note: deposits are valid regardless of fork version, hence the type is passed directly as domain.
-        if not bls_verify(pubkey, signing_root(deposit.data), deposit.data.signature, DOMAIN_DEPOSIT):
+        # Note: deposits are valid across forks, hence the deposit domain is retrieved directly from `bls_domain`
+        if not bls_verify(
+            pubkey, signing_root(deposit.data), deposit.data.signature, bls_domain(DOMAIN_DEPOSIT, DEPOSIT_FORK_VERSION)
+        ):
             return
 
         # Add validator and balance entries

specs/validator/0_beacon-chain-validator.md

@@ -98,7 +98,7 @@ To submit a deposit:
 * Pack the validator's [initialization parameters](#initialization) into `deposit_data`, a [`DepositData`](../core/0_beacon-chain.md#depositdata) SSZ object.
 * Let `amount` be the amount in Gwei to be deposited by the validator where `MIN_DEPOSIT_AMOUNT <= amount <= MAX_EFFECTIVE_BALANCE`.
 * Set `deposit_data.amount = amount`.
-* Let `signature` be the result of `bls_sign` of the `signing_root(deposit_data)` with `domain=DOMAIN_DEPOSIT`. (Deposits are valid regardless of fork version, hence the type is passed directly as domain.)
+* Let `signature` be the result of `bls_sign` of the `signing_root(deposit_data)` with `domain=bls_domain(DOMAIN_DEPOSIT, DEPOSIT_FORK_VERSION)`. (Deposits are valid regardless of fork version, hence the static fork version being directly passed into `bls_domain`).
 * Send a transaction on the Ethereum 1.0 chain to `DEPOSIT_CONTRACT_ADDRESS` executing `def deposit(pubkey: bytes[48], withdrawal_credentials: bytes[32], signature: bytes[96])` along with a deposit of `amount` Gwei.
 
 *Note*: Deposits made for the same `pubkey` are treated as for the same validator. A singular `Validator` will be added to `state.validator_registry` with each additional deposit amount added to the validator's balance. A validator can only be activated when total deposits for the validator pubkey meet or exceed `MAX_EFFECTIVE_BALANCE`.

test_libs/pyspec/tests/helpers.py

@@ -24,6 +24,7 @@ from eth2spec.phase0.spec import (
     VoluntaryExit,
     # functions
     convert_to_indexed,
+    bls_domain,
     get_active_validator_indices,
     get_attesting_indices,
     get_block_root,
@@ -144,9 +145,9 @@ def build_deposit_data(state, pubkey, privkey, amount):
     signature = bls.sign(
         message_hash=signing_root(deposit_data),
         privkey=privkey,
-        domain=get_domain(
-            state,
+        domain=bls_domain(
             spec.DOMAIN_DEPOSIT,
+            spec.DEPOSIT_FORK_VERSION,
         )
     )
     deposit_data.signature = signature