From 76a0ba2d6c452bc9472f5eb3cbb0063bf9e2f7cf Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sun, 3 Mar 2019 11:18:12 +1100
Subject: [PATCH] Add attester slashing support to block processing

At spec v0.2.0
---
 .../state_processing/src/block_processable.rs | 18 +++++-
 .../verify_slashable_attestation.rs           | 63 +++++++++++++++++++
 2 files changed, 80 insertions(+), 1 deletion(-)
 create mode 100644 eth2/state_processing/src/block_processable/verify_slashable_attestation.rs

diff --git a/eth2/state_processing/src/block_processable.rs b/eth2/state_processing/src/block_processable.rs
index e434b0c83..32327aad3 100644
--- a/eth2/state_processing/src/block_processable.rs
+++ b/eth2/state_processing/src/block_processable.rs
@@ -1,3 +1,4 @@
+use self::verify_slashable_attestation::verify_slashable_attestation;
 use crate::SlotProcessingError;
 use hashing::hash;
 use int_to_bytes::int_to_bytes32;
@@ -5,6 +6,8 @@ use log::{debug, trace};
 use ssz::{ssz_encode, TreeHash};
 use types::*;
 
+mod verify_slashable_attestation;
+
 const PHASE_0_CUSTODY_BIT: bool = false;
 
 #[derive(Debug, PartialEq)]
@@ -23,7 +26,9 @@ pub enum Error {
     BadRandaoSignature,
     MaxProposerSlashingsExceeded,
     BadProposerSlashing,
+    MaxAttesterSlashingsExceed,
     MaxAttestationsExceeded,
+    BadAttesterSlashing,
     InvalidAttestation(AttestationValidationError),
     NoBlockRoot,
     MaxDepositsExceeded,
@@ -82,7 +87,7 @@ impl BlockProcessable for BeaconState {
 }
 
 fn per_block_processing_signature_optional(
-    state: &mut BeaconState,
+    mut state: &mut BeaconState,
     block: &BeaconBlock,
     verify_block_signature: bool,
     spec: &ChainSpec,
@@ -205,6 +210,17 @@ fn per_block_processing_signature_optional(
         state.penalize_validator(proposer_slashing.proposer_index as usize, spec)?;
     }
 
+    /*
+     * Attester slashings
+     */
+    ensure!(
+        block.body.attester_slashings.len() as u64 <= spec.max_attester_slashings,
+        Error::MaxAttesterSlashingsExceed
+    );
+    for attester_slashing in &block.body.attester_slashings {
+        verify_slashable_attestation(&mut state, &attester_slashing, spec)?;
+    }
+
     /*
      * Attestations
      */
diff --git a/eth2/state_processing/src/block_processable/verify_slashable_attestation.rs b/eth2/state_processing/src/block_processable/verify_slashable_attestation.rs
new file mode 100644
index 000000000..dddc2eb1f
--- /dev/null
+++ b/eth2/state_processing/src/block_processable/verify_slashable_attestation.rs
@@ -0,0 +1,63 @@
+use super::Error;
+use log::error;
+use types::*;
+
+macro_rules! ensure {
+    ($condition: expr, $result: expr) => {
+        if !$condition {
+            return Err($result);
+        }
+    };
+}
+
+pub fn verify_slashable_attestation(
+    state: &mut BeaconState,
+    attester_slashing: &AttesterSlashing,
+    spec: &ChainSpec,
+) -> Result<(), Error> {
+    let slashable_attestation_1 = &attester_slashing.slashable_attestation_1;
+    let slashable_attestation_2 = &attester_slashing.slashable_attestation_2;
+
+    ensure!(
+        slashable_attestation_1.data != slashable_attestation_2.data,
+        Error::BadAttesterSlashing
+    );
+    ensure!(
+        slashable_attestation_1.is_double_vote(slashable_attestation_2, spec)
+            | slashable_attestation_1.is_surround_vote(slashable_attestation_2, spec),
+        Error::BadAttesterSlashing
+    );
+    error!("this a");
+    ensure!(
+        state.verify_slashable_attestation(&slashable_attestation_1, spec),
+        Error::BadAttesterSlashing
+    );
+    error!("this b");
+    ensure!(
+        state.verify_slashable_attestation(&slashable_attestation_2, spec),
+        Error::BadAttesterSlashing
+    );
+    error!("this c");
+
+    let mut slashable_indices = vec![];
+    for i in &slashable_attestation_1.validator_indices {
+        let validator = state
+            .validator_registry
+            .get(*i as usize)
+            .ok_or_else(|| Error::BadAttesterSlashing)?;
+
+        if slashable_attestation_1.validator_indices.contains(&i)
+            & !validator.is_penalized_at(state.current_epoch(spec))
+        {
+            slashable_indices.push(i);
+        }
+    }
+
+    ensure!(slashable_indices.len() >= 1, Error::BadAttesterSlashing);
+
+    for i in slashable_indices {
+        state.penalize_validator(*i as usize, spec)?;
+    }
+
+    Ok(())
+}