diff options
| -rw-r--r-- | src/net_processing.cpp | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/src/net_processing.cpp b/src/net_processing.cpp index bdbf077ab5..985b41b160 100644 --- a/src/net_processing.cpp +++ b/src/net_processing.cpp @@ -2295,7 +2295,20 @@ bool PeerManagerImpl::AlreadyHaveTx(const GenTxid& gtxid, bool include_reconside const uint256& hash = gtxid.GetHash(); - if (m_orphanage.HaveTx(gtxid)) return true; + if (gtxid.IsWtxid()) { + // Normal query by wtxid. + if (m_orphanage.HaveTx(gtxid)) return true; + } else { + // Never query by txid: it is possible that the transaction in the orphanage has the same + // txid but a different witness, which would give us a false positive result. If we decided + // not to request the transaction based on this result, an attacker could prevent us from + // downloading a transaction by intentionally creating a malleated version of it. + // + // While we won't query by txid, we can try to "guess" what the wtxid is based on the txid. + // A non-segwit transaction's txid == wtxid. Query this txid "casted" to a wtxid. This will + // help us find non-segwit transactions, saving bandwidth, and should have no false positives. + if (m_orphanage.HaveTx(GenTxid::Wtxid(hash))) return true; + } if (include_reconsiderable && m_recent_rejects_reconsiderable.contains(hash)) return true; |