From 628891df1d29920173284f89200b661d4aa2987b Mon Sep 17 00:00:00 2001
From: realbigsean <seananderson33@gmail.com>
Date: Wed, 21 Oct 2020 23:15:30 +0000
Subject: [PATCH] fix genesis state root provided to HTTP server (#1783)

## Issue Addressed

Resolves #1776

## Proposed Changes

The beacon chain builder was using the canonical head's state root for the `genesis_state_root` field.

## Additional Info
---
 beacon_node/beacon_chain/src/builder.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/beacon_node/beacon_chain/src/builder.rs b/beacon_node/beacon_chain/src/builder.rs
index 0c99c35f8..8d1fec9e7 100644
--- a/beacon_node/beacon_chain/src/builder.rs
+++ b/beacon_node/beacon_chain/src/builder.rs
@@ -80,6 +80,7 @@ pub struct BeaconChainBuilder<T: BeaconChainTypes> {
     store_migrator_config: Option<MigratorConfig>,
     pub genesis_time: Option<u64>,
     genesis_block_root: Option<Hash256>,
+    genesis_state_root: Option<Hash256>,
     #[allow(clippy::type_complexity)]
     fork_choice: Option<
         ForkChoice<BeaconForkChoiceStore<T::EthSpec, T::HotStore, T::ColdStore>, T::EthSpec>,
@@ -122,6 +123,7 @@ where
             store_migrator_config: None,
             genesis_time: None,
             genesis_block_root: None,
+            genesis_state_root: None,
             fork_choice: None,
             op_pool: None,
             eth1_chain: None,
@@ -291,6 +293,7 @@ where
             .map_err(|e| format!("Unable to open persisted pubkey cache: {:?}", e))?;
 
         self.genesis_block_root = Some(chain.genesis_block_root);
+        self.genesis_state_root = Some(genesis_block.state_root());
         self.head_tracker = Some(
             HeadTracker::from_ssz_container(&chain.ssz_head_tracker)
                 .map_err(|e| format!("Failed to decode head tracker for database: {:?}", e))?,
@@ -320,6 +323,7 @@ where
         let beacon_state_root = beacon_block.message.state_root;
         let beacon_block_root = beacon_block.canonical_root();
 
+        self.genesis_state_root = Some(beacon_state_root);
         self.genesis_block_root = Some(beacon_block_root);
 
         store
@@ -439,6 +443,9 @@ where
         let genesis_block_root = self
             .genesis_block_root
             .ok_or_else(|| "Cannot build without a genesis block root".to_string())?;
+        let genesis_state_root = self
+            .genesis_state_root
+            .ok_or_else(|| "Cannot build without a genesis state root".to_string())?;
 
         let current_slot = if slot_clock
             .is_prior_to_genesis()
@@ -544,9 +551,9 @@ where
             observed_attester_slashings: <_>::default(),
             eth1_chain: self.eth1_chain,
             genesis_validators_root: canonical_head.beacon_state.genesis_validators_root,
-            genesis_state_root: canonical_head.beacon_state_root,
             canonical_head: TimeoutRwLock::new(canonical_head.clone()),
             genesis_block_root,
+            genesis_state_root,
             fork_choice: RwLock::new(fork_choice),
             event_handler: self
                 .event_handler