re-implement attestation checking in 0.8.0 form and rename relevant function from checkAttestation(...) to spec's process_attestation(...), though there's a slight difference in how they're factored; remove a couple of pointless type conversion warnings; rename validate_indexed_attestation(...) to is_valid_indexed_attestation(...); remove verify_bitfield(...) not in 0.8.0; update AttestationData to 0.8.0 by using Checkpoint data structure; rename MAX_CROSSLINK_EPOCHS to MAX_EPOCHS_PER_CROSSLINK

beacon_chain/attestation_pool.nim

@@ -297,7 +297,7 @@ proc getAttestationsForBlock*(
     #      attestations into the pool in general is an open question that needs
     #      revisiting - for example, when attestations are added, against which
     #      state should they be validated, if at all?
-    if not checkAttestation(
+    if not process_attestation(
         state, attestation, {skipValidation, nextSlot}, cache):
       continue
 

beacon_chain/spec/beaconstate.nim

@@ -146,7 +146,7 @@ func initiate_validator_exit*(state: var BeaconState,
   # Set validator exit epoch and withdrawable epoch
   validator.exit_epoch = exit_queue_epoch
   validator.withdrawable_epoch =
-    (validator.exit_epoch + MIN_VALIDATOR_WITHDRAWABILITY_DELAY).Epoch
+    validator.exit_epoch + MIN_VALIDATOR_WITHDRAWABILITY_DELAY
 
 # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#slash_validator
 func slash_validator*(state: var BeaconState, slashed_index: ValidatorIndex,
@@ -259,16 +259,16 @@ func get_attestation_data_slot*(state: BeaconState,
   # Return the slot corresponding to the attestation ``data``.
   let
     offset = (data.crosslink.shard + SHARD_COUNT -
-      get_start_shard(state, data.target_epoch)) mod SHARD_COUNT
+      get_start_shard(state, data.target.epoch)) mod SHARD_COUNT
 
-  (compute_start_slot_of_epoch(data.target_epoch) + offset div
+  compute_start_slot_of_epoch(data.target.epoch) + offset div
-    (committee_count div SLOTS_PER_EPOCH)).Slot
+    (committee_count div SLOTS_PER_EPOCH)
 
 # This is the slower (O(n)), spec-compatible signature.
 func get_attestation_data_slot*(state: BeaconState,
     data: AttestationData): Slot =
   get_attestation_data_slot(
-    state, data, get_committee_count(state, data.target_epoch))
+    state, data, get_committee_count(state, data.target.epoch))
 
 # https://github.com/ethereum/eth2.0-specs/blob/v0.8.0/specs/core/0_beacon-chain.md#get_block_root_at_slot
 func get_block_root_at_slot*(state: BeaconState,
@@ -332,8 +332,8 @@ func process_registry_updates*(state: var BeaconState) =
       validator.activation_epoch =
         get_delayed_activation_exit_epoch(get_current_epoch(state))
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#validate_indexed_attestation
+# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#is_valid_indexed_attestation
-func validate_indexed_attestation*(
+func is_valid_indexed_attestation*(
     state: BeaconState, indexed_attestation: IndexedAttestation): bool =
   # Verify validity of ``indexed_attestation`` fields.
 
@@ -379,7 +379,7 @@ func validate_indexed_attestation*(
     get_domain(
       state,
       DOMAIN_ATTESTATION,
-      indexed_attestation.data.target_epoch
+      indexed_attestation.data.target.epoch
     ),
   )
 
@@ -398,9 +398,8 @@ func get_attesting_indices*(state: BeaconState,
   result = initSet[ValidatorIndex]()
   let committee =
     get_crosslink_committee(
-      state, attestation_data.target_epoch, attestation_data.crosslink.shard,
+      state, attestation_data.target.epoch, attestation_data.crosslink.shard,
       stateCache)
-  doAssert verify_bitfield(bitfield, len(committee))
   for i, index in committee:
     if get_bitfield_bit(bitfield, i):
       result.incl index
@@ -462,11 +461,10 @@ func get_indexed_attestation(state: BeaconState, attestation: Attestation,
     signature: attestation.signature,
   )
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.6.3/specs/core/0_beacon-chain.md#attestations
+# https://github.com/ethereum/eth2.0-specs/blob/v0.8.0/specs/core/0_beacon-chain.md#attestations
-proc checkAttestation*(
+proc process_attestation*(
     state: BeaconState, attestation: Attestation, flags: UpdateFlags,
     stateCache: var StateCache): bool =
-  ## Process ``Attestation`` operation.
   ## Check that an attestation follows the rules of being included in the state
   ## at the current slot. When acting as a proposer, the same rules need to
   ## be followed!
@@ -475,9 +473,19 @@ proc checkAttestation*(
     if nextSlot in flags: state.slot + 1
     else: state.slot
 
-  let
+  let data = attestation.data
-    data = attestation.data
+
-    attestation_slot = get_attestation_data_slot(state, attestation.data)
+  if not (data.crosslink.shard < SHARD_COUNT):
+    warn("Attestation shard too high",
+      attestation_shard = data.crosslink.shard)
+    return
+
+  if not (data.target.epoch == get_previous_epoch(state) or
+      data.target.epoch == get_current_epoch(state)):
+    warn("Target epoch not current or previous epoch")
+    return
+
+  let attestation_slot = get_attestation_data_slot(state, attestation.data)
 
   if not (attestation_slot + MIN_ATTESTATION_INCLUSION_DELAY <= stateSlot):
     warn("Attestation too new",
@@ -498,25 +506,19 @@ proc checkAttestation*(
     proposer_index: get_beacon_proposer_index(state, stateCache),
   )
 
-  # Check target epoch, source epoch, source root, and source crosslink
-  if not (data.target_epoch == get_previous_epoch(state) or
-      data.target_epoch == get_current_epoch(state)):
-    warn("Target epoch not current or previous epoch")
-    return
-
   # Check FFG data, crosslink data, and signature
-  let ffg_check_data = (data.source_epoch, data.source_root, data.target_epoch)
+  let ffg_check_data = (data.source.epoch, data.source.root, data.target.epoch)
 
-  if data.target_epoch == get_current_epoch(state):
+  if data.target.epoch == get_current_epoch(state):
     if not (ffg_check_data == (state.current_justified_epoch,
         state.current_justified_root, get_current_epoch(state))):
       warn("FFG data not matching current justified epoch")
       return
 
-    #if not (data.crosslink.parent_root ==
+    if not (data.crosslink.parent_root ==
-    #    hash_tree_root(state.current_crosslinks[data.crosslink.shard])):
+        hash_tree_root(state.current_crosslinks[data.crosslink.shard])):
-    #  warn("Crosslink shard's current crosslinks not matching crosslink parent root")
+      warn("Crosslink shard's current crosslinks not matching crosslink parent root")
-    #  return
+      return
 
     #state.current_epoch_attestations.add(pending_attestation)
   else:
@@ -525,39 +527,49 @@ proc checkAttestation*(
       warn("FFG data not matching current justified epoch")
       return
 
-    #if not (data.crosslink.parent_root ==
+    if not (data.crosslink.parent_root ==
-    #    hash_tree_root(state.previous_crosslinks[data.crosslink.shard])):
+        hash_tree_root(state.previous_crosslinks[data.crosslink.shard])):
-    #  warn("Crosslink shard's previous crosslinks not matching crosslink parent root")
+      warn("Crosslink shard's previous crosslinks not matching crosslink parent root")
-    #  return
+      return
 
     #state.previous_epoch_attestations.add(pending_attestation)
 
-  # TODO un-comment when changed Crosslink to 0.7 structure
+  let parent_crosslink = if data.target.epoch == get_current_epoch(state):
-  #if not (data.crosslink.start_epoch == parent_crosslink.end_epoch):
+    state.current_crosslinks[data.crosslink.shard]
-  #  warn("Crosslink start and end epochs not the same")
+  else:
-  #  return
+    state.previous_crosslinks[data.crosslink.shard]
 
-  #if not (data.crosslink.end_epoch == min(data.target_epoch, parent_crosslink.end_epoch + MAX_EPOCHS_PER_CROSSLINK)):
+  if not (data.crosslink.parent_root == hash_tree_root(parent_crosslink)):
-  #  warn("Crosslink end epoch incorrect")
+    warn("Crosslink parent root doesn't match parent crosslink's root")
-  #  return
+    return
 
-  # Simlarly, these depend on 0.7 data structures
+  if not (data.crosslink.start_epoch == parent_crosslink.end_epoch):
-  #assert data.crosslink.parent_root == hash_tree_root(parent_crosslink)
+    warn("Crosslink start and end epochs not the same")
+    return
 
-  #if not (data.crosslink.data_root == ZERO_HASH):  # [to be removed in phase 1]
+  if not (data.crosslink.end_epoch == min(
-  #  warn("Crosslink data root not zero")
+      data.target.epoch,
-  #  return
+      parent_crosslink.end_epoch + MAX_EPOCHS_PER_CROSSLINK)):
+    warn("Crosslink end epoch incorrect",
+      crosslink_end_epoch = data.crosslink.end_epoch,
+      parent_crosslink_end_epoch = parent_crosslink.end_epoch,
+      target_epoch = data.target.epoch)
+    return
+
+  if not (data.crosslink.data_root == ZERO_HASH):  # [to be removed in phase 1]
+    warn("Crosslink data root not zero")
+    return
 
   # Check signature and bitfields
-  if not validate_indexed_attestation(
+  if not is_valid_indexed_attestation(
       state, get_indexed_attestation(state, attestation, stateCache)):
-    warn("checkAttestation: signature or bitfields incorrect")
+    warn("process_attestation: signature or bitfields incorrect")
     return
 
   true
 
 proc makeAttestationData*(
-    state: BeaconState, shard: uint64,
+    state: BeaconState, shard_offset: uint64,
     beacon_block_root: Eth2Digest): AttestationData =
   ## Fine points:
   ## Head must be the head state during the slot that validator is
@@ -568,17 +580,23 @@ proc makeAttestationData*(
     target_root =
       if epoch_start_slot == state.slot: beacon_block_root
       else: get_block_root_at_slot(state, epoch_start_slot)
+    shard = (shard_offset + get_start_shard(state,
+      compute_epoch_of_slot(state.slot))) mod SHARD_COUNT
+    target_epoch = compute_epoch_of_slot(state.slot)
 
   AttestationData(
     beacon_block_root: beacon_block_root,
-    target_root: target_root,
+    source: Checkpoint(
-    source_epoch: state.current_justified_epoch,
+      epoch: state.current_justified_epoch,
-    source_root: state.current_justified_root,
+      root: state.current_justified_root
-    target_epoch: compute_epoch_of_slot(state.slot),
+    ),
+    target: Checkpoint(
+      root: target_root,
+      epoch: target_epoch
+    ),
     crosslink: Crosslink(
-      # Alternative is to put this offset into all callers
+      shard: shard,
-      shard: shard + get_start_shard(state, compute_epoch_of_slot(state.slot)),
       parent_root: hash_tree_root(state.current_crosslinks[shard]),
-      data_root: Eth2Digest(), # Stub in phase0
+      end_epoch: target_epoch,
     )
   )

beacon_chain/spec/bitfield.nim

@@ -24,19 +24,6 @@ func get_bitfield_bit*(bitfield: BitField, i: int): bool =
   doAssert i div 8 < bitfield.bits.len, "i: " & $i & " i div 8: " & $(i div 8)
   ((bitfield.bits[i div 8] shr (i mod 8)) mod 2) > 0'u8
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#verify_bitfield
-func verify_bitfield*(bitfield: BitField, committee_size: int): bool =
-  # Verify ``bitfield`` against the ``committee_size``.
-  if len(bitfield.bits) != (committee_size + 7) div 8:
-    return false
-
-  # Check `bitfield` is padded with zero bits only
-  for i in committee_size ..< (len(bitfield.bits) * 8):
-    if get_bitfield_bit(bitfield, i):
-      return false
-
-  true
-
 # TODO spec candidatidates below, though they're used only indirectly there..
 func set_bitfield_bit*(bitfield: var BitField, i: int) =
   bitfield.bits[i div 8] = bitfield.bits[i div 8] or 1'u8 shl (i mod 8)

beacon_chain/spec/datatypes.nim

@@ -123,16 +123,14 @@ type
     epoch*: Epoch
     root*: Eth2Digest
 
-  # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#attestationdata
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.8.0/specs/core/0_beacon-chain.md#AttestationData
   AttestationData* = object
     # LMD GHOST vote
     beacon_block_root*: Eth2Digest
 
     # FFG vote
-    source_epoch*: Epoch
+    source*: Checkpoint
-    source_root*: Eth2Digest
+    target*: Checkpoint
-    target_epoch*: Epoch
-    target_root*: Eth2Digest
 
     # Crosslink vote
     crosslink*: Crosslink
@@ -456,8 +454,8 @@ func shortLog*(v: BeaconBlock): tuple[
 func shortLog*(v: AttestationData): auto =
    (
       shortLog(v.beacon_block_root),
-      humaneEpochNum(v.source_epoch), shortLog(v.target_root),
+      humaneEpochNum(v.source.epoch), shortLog(v.target.root),
-      shortLog(v.source_root),
+      shortLog(v.source.root),
       v.crosslink
     )
 

beacon_chain/spec/presets/mainnet.nim

@@ -128,7 +128,7 @@ const
   PERSISTENT_COMMITTEE_PERIOD* = 2'u64^11 ##\
   ## epochs (9 days)
 
-  MAX_CROSSLINK_EPOCHS* = 2'u64^6 ##\
+  MAX_EPOCHS_PER_CROSSLINK* = 2'u64^6 ##\
   ## epochs (~7 hours)
 
   MIN_EPOCHS_TO_INACTIVITY_PENALTY* = 2'u64^2 ##\

beacon_chain/spec/presets/minimal.nim

@@ -93,7 +93,7 @@ const
   # Unchanged
   MIN_VALIDATOR_WITHDRAWABILITY_DELAY* = 2'u64^8
   PERSISTENT_COMMITTEE_PERIOD* = 2'u64^11
-  MAX_CROSSLINK_EPOCHS* = 2'u64^6
+  MAX_EPOCHS_PER_CROSSLINK* = 2'u64^6
   MIN_EPOCHS_TO_INACTIVITY_PENALTY* = 2'u64^2
 
   # State list lengths

beacon_chain/spec/state_transition_block.nim

@@ -184,10 +184,10 @@ func is_slashable_attestation_data(
   ## rules.
 
   # Double vote
-  (data_1 != data_2 and data_1.target_epoch == data_2.target_epoch) or
+  (data_1 != data_2 and data_1.target.epoch == data_2.target.epoch) or
   # Surround vote
-    (data_1.source_epoch < data_2.source_epoch and
+    (data_1.source.epoch < data_2.source.epoch and
-     data_2.target_epoch < data_1.target_epoch)
+     data_2.target.epoch < data_1.target.epoch)
 
 # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#attester-slashings
 proc processAttesterSlashings(state: var BeaconState, blck: BeaconBlock,
@@ -208,11 +208,11 @@ proc processAttesterSlashings(state: var BeaconState, blck: BeaconBlock,
       notice "CaspSlash: surround or double vote check failed"
       return false
 
-    if not validate_indexed_attestation(state, attestation_1):
+    if not is_valid_indexed_attestation(state, attestation_1):
       notice "CaspSlash: invalid votes 1"
       return false
 
-    if not validate_indexed_attestation(state, attestation_2):
+    if not is_valid_indexed_attestation(state, attestation_2):
       notice "CaspSlash: invalid votes 2"
       return false
 
@@ -247,7 +247,7 @@ proc processAttestations(
     notice "Attestation: too many!", attestations = blck.body.attestations.len
     return false
 
-  if not blck.body.attestations.allIt(checkAttestation(state, it, flags, stateCache)):
+  if not blck.body.attestations.allIt(process_attestation(state, it, flags, stateCache)):
     return false
 
   # All checks passed - update state
@@ -257,7 +257,7 @@ proc processAttestations(
   for attestation in blck.body.attestations:
     # Caching
     let
-      epoch = attestation.data.target_epoch
+      epoch = attestation.data.target.epoch
       committee_count = if epoch in committee_count_cache:
           committee_count_cache[epoch]
         else:
@@ -274,7 +274,7 @@ proc processAttestations(
       proposer_index: get_beacon_proposer_index(state, stateCache),
     )
 
-    if attestation.data.target_epoch == get_current_epoch(state):
+    if attestation.data.target.epoch == get_current_epoch(state):
       state.current_epoch_attestations.add(pending_attestation)
     else:
       state.previous_epoch_attestations.add(pending_attestation)

beacon_chain/spec/state_transition_epoch.nim

@@ -55,7 +55,7 @@ func get_matching_target_attestations(state: BeaconState, epoch: Epoch):
     seq[PendingAttestation] =
   filterIt(
     get_matching_source_attestations(state, epoch),
-    it.data.target_root == get_block_root(state, epoch)
+    it.data.target.root == get_block_root(state, epoch)
   )
 
 func get_matching_head_attestations(state: BeaconState, epoch: Epoch):