From 756213c5f509425e9a253d707873cbe8504b7a28 Mon Sep 17 00:00:00 2001
From: Ethan Buchman <ethan@coinculture.info>
Date: Mon, 20 Feb 2017 17:08:38 -0500
Subject: [PATCH] check appHash

---
 consensus/state.go |  2 +-
 state/execution.go | 21 +++++++++++----------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/consensus/state.go b/consensus/state.go
index c077c412c..8e721ed3e 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -253,7 +253,7 @@ type ConsensusState struct {
 	done chan struct{}
 }
 
-// Replay the last block through the consensus and return the AppHash after commit.
+// Replay the last block through the consensus and return the AppHash from after Commit.
 func ReplayLastBlock(config cfg.Config, state *sm.State, proxyApp proxy.AppConnConsensus, blockStore sm.BlockStore) ([]byte, error) {
 	mempool := sm.MockMempool{}
 	cs := NewConsensusState(config, state, proxyApp, blockStore, mempool)
diff --git a/state/execution.go b/state/execution.go
index 7677a672a..c1471bf86 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -364,19 +364,17 @@ func (h *Handshaker) Handshake(proxyApp proxy.AppConns) error {
 	// TODO: check version
 
 	// replay blocks up to the latest in the blockstore
-	appHash, err = h.ReplayBlocks(appHash, blockHeight, proxyApp)
+	_, err = h.ReplayBlocks(appHash, blockHeight, proxyApp)
 	if err != nil {
 		return errors.New(Fmt("Error on replay: %v", err))
 	}
 
-	// NOTE: the h.state may now be behind the cs state
-
 	// TODO: (on restart) replay mempool
 
 	return nil
 }
 
-// Replay all blocks after blockHeight and ensure the result matches the current state.
+// Replay all blocks since appBlockHeight and ensure the result matches the current state.
 // Returns the final AppHash or an error
 func (h *Handshaker) ReplayBlocks(appHash []byte, appBlockHeight int, proxyApp proxy.AppConns) ([]byte, error) {
 
@@ -386,11 +384,11 @@ func (h *Handshaker) ReplayBlocks(appHash []byte, appBlockHeight int, proxyApp p
 
 	// First handle edge cases and constraints on the storeBlockHeight
 	if storeBlockHeight == 0 {
-		return nil, nil
+		return appHash, h.checkAppHash(appHash)
 
 	} else if storeBlockHeight < appBlockHeight {
 		// the app should never be ahead of the store (but this is under app's control)
-		return nil, ErrAppBlockHeightTooHigh{storeBlockHeight, appBlockHeight}
+		return appHash, ErrAppBlockHeightTooHigh{storeBlockHeight, appBlockHeight}
 
 	} else if storeBlockHeight < stateBlockHeight {
 		// the state should never be ahead of the store (this is under tendermint's control)
@@ -412,7 +410,7 @@ func (h *Handshaker) ReplayBlocks(appHash []byte, appBlockHeight int, proxyApp p
 
 		} else if appBlockHeight == storeBlockHeight {
 			// we're good!
-			return appHash, nil
+			return appHash, h.checkAppHash(appHash)
 		}
 
 	} else if storeBlockHeight == stateBlockHeight+1 {
@@ -473,11 +471,14 @@ func (h *Handshaker) replayBlocks(proxyApp proxy.AppConns, appBlockHeight, store
 		}
 	}
 
+	return appHash, h.checkAppHash(appHash)
+}
+
+func (h *Handshaker) checkAppHash(appHash []byte) error {
 	if !bytes.Equal(h.state.AppHash, appHash) {
-		return nil, errors.New(Fmt("Tendermint state.AppHash does not match AppHash after replay. Got %X, expected %X", appHash, h.state.AppHash))
+		return errors.New(Fmt("Tendermint state.AppHash does not match AppHash after replay. Got %X, expected %X", appHash, h.state.AppHash))
 	}
-
-	return appHash, nil
+	return nil
 }
 
 //--------------------------------------------------------------------------------