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authorPieter Wuille <pieter.wuille@gmail.com>2012-02-17 17:58:02 +0100
committerPieter Wuille <pieter.wuille@gmail.com>2012-03-03 18:26:36 +0100
commita206b0ea12eb4606b93323268fc81a4f1f952531 (patch)
tree9691c6cfc013c7efb7692502a5f43b283ba6e42a /src/main.cpp
parent50abb5516da51fc518fe363bd445afbab70c71ec (diff)
Do not allow overwriting unspent transactions (BIP 30)
Introduce the following network rule: * a block is not valid if it contains a transaction whose hash already exists in the block chain, unless all that transaction's outputs were already spent before said block. Warning: this is effectively a network rule change, with potential risk for forking the block chain. Leaving this unfixed carries the same risk however, for attackers that can cause a reorganisation in part of the network. Thanks to Russell O'Connor and Ben Reeves.
Diffstat (limited to 'src/main.cpp')
-rw-r--r--src/main.cpp26
1 files changed, 24 insertions, 2 deletions
diff --git a/src/main.cpp b/src/main.cpp
index 995195289f..20aa069a79 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -976,8 +976,10 @@ bool CTransaction::DisconnectInputs(CTxDB& txdb)
}
// Remove transaction from index
- if (!txdb.EraseTxIndex(*this))
- return error("DisconnectInputs() : EraseTxPos failed");
+ // This can fail if a duplicate of this transaction was in a chain that got
+ // reorganized away. This is only possible if this transaction was completely
+ // spent, so erasing it would be a no-op anway.
+ txdb.EraseTxIndex(*this);
return true;
}
@@ -1256,6 +1258,26 @@ bool CBlock::ConnectBlock(CTxDB& txdb, CBlockIndex* pindex)
if (!CheckBlock())
return false;
+ // Do not allow blocks that contain transactions which 'overwrite' older transactions,
+ // unless those are already completely spent.
+ // If such overwrites are allowed, coinbases and transactions depending upon those
+ // can be duplicated to remove the ability to spend the first instance -- even after
+ // being sent to another address.
+ // See BIP30 and http://r6.ca/blog/20120206T005236Z.html for more information.
+ // This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
+ // already refuses previously-known transaction id's entirely.
+ // This rule applies to all blocks whose timestamp is after March 15, 2012, 0:00 UTC.
+ // On testnet it is enabled as of februari 20, 2012, 0:00 UTC.
+ if (pindex->nTime > 1331769600 || (fTestNet && pindex->nTime > 1329696000))
+ BOOST_FOREACH(CTransaction& tx, vtx)
+ {
+ CTxIndex txindexOld;
+ if (txdb.ReadTxIndex(tx.GetHash(), txindexOld))
+ BOOST_FOREACH(CDiskTxPos &pos, txindexOld.vSpent)
+ if (pos.IsNull())
+ return false;
+ }
+
// To avoid being on the short end of a block-chain split,
// don't do secondary validation of pay-to-script-hash transactions
// until blocks with timestamps after paytoscripthashtime (see init.cpp for default).