From f4679dba212870242e0ff1ba7eaaeaf5fff44912 Mon Sep 17 00:00:00 2001
From: Jernej Kos <jernej@kos.mx>
Date: Fri, 21 Aug 2020 10:17:11 +0200
Subject: [PATCH] go/roothash: Make the parent block check earlier

---
 .changelog/3206.bugfix.md          |  1 +
 go/roothash/api/commitment/pool.go | 22 ++++++++++------------
 2 files changed, 11 insertions(+), 12 deletions(-)
 create mode 100644 .changelog/3206.bugfix.md

diff --git a/.changelog/3206.bugfix.md b/.changelog/3206.bugfix.md
new file mode 100644
index 00000000000..106ae9827b2
--- /dev/null
+++ b/.changelog/3206.bugfix.md
@@ -0,0 +1 @@
+go/roothash: Make the parent block check earlier
diff --git a/go/roothash/api/commitment/pool.go b/go/roothash/api/commitment/pool.go
index d5fc3e1a204..e12d42edcfd 100644
--- a/go/roothash/api/commitment/pool.go
+++ b/go/roothash/api/commitment/pool.go
@@ -149,8 +149,6 @@ func (p *Pool) addOpenExecutorCommitment(
 		return ErrNotInCommittee
 	}
 
-	// TODO: Check for signs of double signing (#1804).
-
 	// Ensure the node did not already submit a commitment.
 	if _, ok := p.ExecuteCommitments[id]; ok {
 		return ErrAlreadyCommitted
@@ -169,6 +167,16 @@ func (p *Pool) addOpenExecutorCommitment(
 		return ErrInvalidMessages
 	}
 
+	// Check if the block is based on the previous block.
+	if !header.IsParentOf(&blk.Header) {
+		logger.Debug("executor commitment is not based on correct block",
+			"node_id", id,
+			"expected_previous_hash", blk.Header.EncodedHash(),
+			"previous_hash", header.PreviousHash,
+		)
+		return ErrNotBasedOnCorrectBlock
+	}
+
 	// Verify RAK-attestation.
 	if p.Runtime.TEEHardware != node.TEEHardwareInvalid {
 		n, err := nl.Node(ctx, id)
@@ -198,16 +206,6 @@ func (p *Pool) addOpenExecutorCommitment(
 		}
 	}
 
-	// Check if the block is based on the previous block.
-	if !header.IsParentOf(&blk.Header) {
-		logger.Debug("executor commitment is not based on correct block",
-			"node_id", id,
-			"expected_previous_hash", blk.Header.EncodedHash(),
-			"previous_hash", header.PreviousHash,
-		)
-		return ErrNotBasedOnCorrectBlock
-	}
-
 	if err := sv.VerifyTxnSchedulerSignature(body.TxnSchedSig, blk.Header.Round); err != nil {
 		logger.Debug("executor commitment has bad transaction scheduler signer",
 			"node_id", id,