From ee1cb0cba075530a6364f80bfe5d534aa2409c21 Mon Sep 17 00:00:00 2001
From: Zsolt Felfoldi <zsfelfoldi@gmail.com>
Date: Wed, 8 May 2019 16:11:21 +0200
Subject: [PATCH] light: add canonical header verification to GetTransaction

---
 light/odr_util.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/light/odr_util.go b/light/odr_util.go
index 197fd032da..100bd58428 100644
--- a/light/odr_util.go
+++ b/light/odr_util.go
@@ -236,6 +236,11 @@ func GetTransaction(ctx context.Context, odr OdrBackend, txHash common.Hash) (*t
 		return nil, common.Hash{}, 0, 0, err
 	} else {
 		pos := r.Status[0].Lookup
+		// first ensure that we have the header, otherwise block body retrieval will fail
+		// also verify if this is a canonical block by getting the header by number and checking its hash
+		if header, err := GetHeaderByNumber(ctx, odr, pos.BlockIndex); err != nil || header.Hash() != pos.BlockHash {
+			return nil, common.Hash{}, 0, 0, err
+		}
 		if body, err := GetBody(ctx, odr, pos.BlockHash, pos.BlockIndex); err != nil || uint64(len(body.Transactions)) <= pos.Index || body.Transactions[pos.Index].Hash() != txHash {
 			return nil, common.Hash{}, 0, 0, err
 		} else {