From 01c28073ba2cae5a53124c7dc7123240b98513ce Mon Sep 17 00:00:00 2001 From: Peter Todd Date: Sat, 20 Sep 2014 12:32:42 -0400 Subject: [PATCH] Add warning about the merkle-tree algorithm duplicate txid flaw Lots of people read the Bitcoin Core codebase to learn more about crypto; better to warn about flaws explicitly so they don't blindly copy the code for other uses and create broken systems. --- src/core.cpp | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/core.cpp b/src/core.cpp index 491e4fa68b..e52327ba8e 100644 --- a/src/core.cpp +++ b/src/core.cpp @@ -226,6 +226,13 @@ uint256 CBlockHeader::GetHash() const uint256 CBlock::BuildMerkleTree() const { + // WARNING! If you're reading this because you're learning about crypto + // and/or designing a new system that will use merkle trees, keep in mind + // that the following merkle tree algorithm has a serious flaw related to + // duplicate txids, resulting in a vulnerability. (CVE-2012-2459) Bitcoin + // has since worked around the flaw, but for new applications you should + // use something different; don't just copy-and-paste this code without + // understanding the problem first. vMerkleTree.clear(); BOOST_FOREACH(const CTransaction& tx, vtx) vMerkleTree.push_back(tx.GetHash());