From 04791dfc5826db5672ea9f6173c8ff96fc1c04bd Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Wed, 22 May 2019 11:41:15 +1000
Subject: [PATCH] Update `verify_exit` to spec v0.6.1

---
 .../src/per_block_processing.rs               |  4 +--
 .../src/per_block_processing/errors.rs        |  2 ++
 .../src/per_block_processing/verify_exit.rs   | 26 +++++++++++--------
 3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/eth2/state_processing/src/per_block_processing.rs b/eth2/state_processing/src/per_block_processing.rs
index c66b8baea..1d729578e 100644
--- a/eth2/state_processing/src/per_block_processing.rs
+++ b/eth2/state_processing/src/per_block_processing.rs
@@ -1,4 +1,4 @@
-use crate::common::slash_validator;
+use crate::common::{initiate_validator_exit, slash_validator};
 use errors::{BlockInvalid as Invalid, BlockProcessingError as Error, IntoWithIndex};
 use rayon::prelude::*;
 use tree_hash::{SignedRoot, TreeHash};
@@ -448,7 +448,7 @@ pub fn process_exits<T: EthSpec>(
 
     // Update the state in series.
     for exit in voluntary_exits {
-        state.initiate_validator_exit(exit.validator_index as usize);
+        initiate_validator_exit(state, exit.validator_index as usize, spec)?;
     }
 
     Ok(())
diff --git a/eth2/state_processing/src/per_block_processing/errors.rs b/eth2/state_processing/src/per_block_processing/errors.rs
index 747664b94..b6a1fd629 100644
--- a/eth2/state_processing/src/per_block_processing/errors.rs
+++ b/eth2/state_processing/src/per_block_processing/errors.rs
@@ -348,6 +348,8 @@ pub enum ExitValidationError {
 /// Describes why an object is invalid.
 #[derive(Debug, PartialEq)]
 pub enum ExitInvalid {
+    /// The specified validator is not active.
+    NotActive(u64),
     /// The specified validator is not in the state's validator registry.
     ValidatorUnknown(u64),
     /// The specified validator has a non-maximum exit epoch.
diff --git a/eth2/state_processing/src/per_block_processing/verify_exit.rs b/eth2/state_processing/src/per_block_processing/verify_exit.rs
index 865942ef4..2a3a29b3f 100644
--- a/eth2/state_processing/src/per_block_processing/verify_exit.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_exit.rs
@@ -7,7 +7,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `Exit` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn verify_exit<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
@@ -17,6 +17,8 @@ pub fn verify_exit<T: EthSpec>(
 }
 
 /// Like `verify_exit` but doesn't run checks which may become true in future states.
+///
+/// Spec v0.6.1
 pub fn verify_exit_time_independent_only<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
@@ -26,6 +28,8 @@ pub fn verify_exit_time_independent_only<T: EthSpec>(
 }
 
 /// Parametric version of `verify_exit` that skips some checks if `time_independent_only` is true.
+///
+/// Spec v0.6.1
 fn verify_exit_parametric<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
@@ -37,18 +41,18 @@ fn verify_exit_parametric<T: EthSpec>(
         .get(exit.validator_index as usize)
         .ok_or_else(|| Error::Invalid(Invalid::ValidatorUnknown(exit.validator_index)))?;
 
+    // Verify the validator is active.
+    verify!(
+        validator.is_active_at(state.current_epoch()),
+        Invalid::NotActive(exit.validator_index)
+    );
+
     // Verify that the validator has not yet exited.
     verify!(
         validator.exit_epoch == spec.far_future_epoch,
         Invalid::AlreadyExited(exit.validator_index)
     );
 
-    // Verify that the validator has not yet initiated.
-    verify!(
-        !validator.initiated_exit,
-        Invalid::AlreadyInitiatedExited(exit.validator_index)
-    );
-
     // Exits must specify an epoch when they become valid; they are not valid before then.
     verify!(
         time_independent_only || state.current_epoch() >= exit.epoch,
@@ -58,8 +62,8 @@ fn verify_exit_parametric<T: EthSpec>(
         }
     );
 
-    // Must have been in the validator set long enough.
-    let lifespan = state.slot.epoch(spec.slots_per_epoch) - validator.activation_epoch;
+    // Verify the validator has been active long enough.
+    let lifespan = state.current_epoch() - validator.activation_epoch;
     verify!(
         lifespan >= spec.persistent_committee_period,
         Invalid::TooYoungToLeave {
@@ -68,9 +72,9 @@ fn verify_exit_parametric<T: EthSpec>(
         }
     );
 
+    // Verify signature.
     let message = exit.signed_root();
-    let domain = spec.get_domain(exit.epoch, Domain::Exit, &state.fork);
-
+    let domain = spec.get_domain(exit.epoch, Domain::VoluntaryExit, &state.fork);
     verify!(
         exit.signature
             .verify(&message[..], domain, &validator.pubkey),