address issue #1580 (#1600)

* address issue #1580

* Update beacon_chain/spec/beaconstate.nim

Co-authored-by: Jacek Sieka <jacek@status.im>

beacon_chain/eth2_processor.nim

@@ -299,6 +299,7 @@ proc attestationValidator*(
 
   logScope: wallSlot
 
+  # Potential under/overflows are fine; would just create odd metrics and logs
   let delay = wallTime - attestation.data.slot.toBeaconTime
   debug "Attestation received", delay
   let v = self.attestationPool[].validateAttestation(
@@ -339,6 +340,7 @@ proc aggregateValidator*(
 
   logScope: wallSlot
 
+  # Potential under/overflows are fine; would just create odd logs
   let delay =
     wallTime - signedAggregateAndProof.message.aggregate.data.slot.toBeaconTime
   debug "Aggregate received", delay

beacon_chain/spec/beaconstate.nim

@@ -322,6 +322,10 @@ func get_block_root_at_slot*(state: BeaconState,
                              slot: Slot): Eth2Digest =
   # Return the block root at a recent ``slot``.
 
+  # Potential overflow/wrap shouldn't occur, as get_block_root_at_slot() called
+  # from internally controlled sources, but flag this explicitly, in case.
+  doAssert slot + SLOTS_PER_HISTORICAL_ROOT > slot
+
   doAssert state.slot <= slot + SLOTS_PER_HISTORICAL_ROOT
   doAssert slot < state.slot
   state.block_roots[slot mod SLOTS_PER_HISTORICAL_ROOT]
@@ -538,6 +542,12 @@ func check_attestation_target_epoch*(
 
 func check_attestation_inclusion*(data: AttestationData,
                                   current_slot: Slot): Result[void, cstring] =
+  # Check for overflow
+  static:
+    doAssert SLOTS_PER_EPOCH >= MIN_ATTESTATION_INCLUSION_DELAY
+  if data.slot + SLOTS_PER_EPOCH <= data.slot:
+    return err("attestation data.slot overflow, malicious?")
+
   if not (data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= current_slot):
     return err("Attestation too new")