mempool: check input index when comparing replacement to conflict

lib/mempool/mempool.js

@@ -1074,7 +1074,7 @@ class Mempool extends EventEmitter {
  // must also be spent by the conflict.
  for (const {prevout: conflictPrevout} of conflict.tx.inputs) {
  if (conflictPrevout.hash.equals(prevout.hash)
- && conflictPrevout.input === prevout.input) {
+ && conflictPrevout.index === prevout.index) {
  // Once we find a match we don't need to check any more
  // of the conflict's inputs. Continue by testing the
  // next input in the potential replacement tx.

test/mempool-test.js

@@ -1638,5 +1638,63 @@ describe('Mempool', function() {
  assert(mempool.has(tx1.hash()));
  assert(!mempool.has(tx2.hash()));
  });
+
+ it('should not accept replacement that does not evict its own inputs', async () => {
+ // ...because it is still adding a new unconfirmed input.
+ // {confirmed coin 1}
+ // |
+ // tx 0 {output 0} {output 1}
+ // | | |
+ // tx 1 +-------+ |
+ // | |
+ // tx 2
+
+ mempool.options.replaceByFee = true;
+
+ const addr1 = chaincoins.createReceive().getAddress();
+ const coin0 = chaincoins.getCoins()[0];
+
+ // Generate tx 0 which spends a confirmed coin and creates two outputs
+ const mtx0 = new MTX();
+ mtx0.addCoin(coin0);
+ mtx0.addOutput(addr1, parseInt(coin0.value / 2) - 200);
+ mtx0.addOutput(addr1, parseInt(coin0.value / 2) - 200);
+ chaincoins.sign(mtx0);
+ assert(mtx0.verify());
+ const tx0 = mtx0.toTX();
+ await mempool.addTX(tx0);
+
+ // Generate tx 1 which spends output 0 of tx 0
+ const mtx1 = new MTX();
+ const coin1 = Coin.fromTX(tx0, 0, -1);
+ mtx1.addCoin(coin1);
+ mtx1.inputs[0].sequence = 0xfffffffd;
+ mtx1.addOutput(addr1, coin1.value - 200);
+ chaincoins.sign(mtx1);
+ assert(mtx1.verify());
+ const tx1 = mtx1.toTX();
+ await mempool.addTX(tx1);
+
+ // Send tx 2 which spends outputs 0 & 1 of tx 0, replacing tx 1
+ const mtx2 = new MTX();
+ mtx2.addCoin(coin1);
+ const coin2 = Coin.fromTX(tx0, 1, -1);
+ mtx2.addCoin(coin2);
+ mtx2.addOutput(addr1, coin2.value + coin1.value - 1000);
+ chaincoins.sign(mtx2);
+ assert(mtx2.verify());
+ const tx2 = mtx2.toTX();
+
+ await assert.rejects(async () => {
+ await mempool.addTX(tx2);
+ }, {
+ type: 'VerifyError',
+ reason: 'replacement-adds-unconfirmed'
+ });
+
+ assert(mempool.has(tx0.hash()));
+ assert(mempool.has(tx1.hash()));
+ assert(!mempool.has(tx2.hash()));
+ });
  });
 });