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Merge bitcoin#15846: [POLICY] Make sending to future native witness o…

…utputs standard

c634b1e [POLICY] Make sending to future native witness outputs standard (Pieter Wuille)

Pull request description:

  As discussed in the April 18 2019 IRC meeting.

  This makes sending to future Segwit versions via native outputs (bech32) standard for relay, mempool acceptance, and mining. The reasons are:
  * This may interfere with smooth adoption of future segwit versions, if they're defined (by the sender wallet/node).
  * It violates BIP173 ("Version 0 witness addresses are always 42 or 62 characters, but implementations MUST allow the use of any version."), though admittedly this code was written before BIP173.
  * It doesn't protect much, as P2SH-embedded segwit cannot be filtered in this way.
  * As a general policy, the sender shouldn't care what the receiver likes his outputs to be.

  Note that _spending_ such outputs (including P2SH-embedded ones) remains nonstandard, as that is actually required for softfork safety.

ACKs for commit c634b1:
    utACK c634b1e
    Tested ACK c634b1e
    utACK bitcoin@c634b1e

Tree-SHA512: e37168a1be9f445a04d4280593f0a92bdae33eee00ecd803d5eb16acb5c9cfc0f1f0a1dfbd5a0cc73da2c9928ec11cbdac7911513a78f85b789ae0d00e1b5962
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meshcollider authored and sidhujag committed Apr 27, 2019
1 parent f9c3d44 commit 71bb171d6be1a5a1b1803181298223fc7cf42704
Showing with 6 additions and 6 deletions.
  1. +1 −1 src/policy/policy.cpp
  2. +5 −5 test/functional/
@@ -60,7 +60,7 @@ bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType)
std::vector<std::vector<unsigned char> > vSolutions;
whichType = Solver(scriptPubKey, vSolutions);

if (whichType == TX_NONSTANDARD || whichType == TX_WITNESS_UNKNOWN) {
if (whichType == TX_NONSTANDARD) {
return false;
} else if (whichType == TX_MULTISIG) {
unsigned char m = vSolutions.front()[0];
@@ -1125,7 +1125,8 @@ def test_tx_relay_after_segwit_activation(self):
def test_segwit_versions(self):
"""Test validity of future segwit version transactions.
Future segwit version transactions are non-standard, but valid in blocks.
Future segwit versions are non-standard to spend, but valid in blocks.
Sending to future segwit versions is always allowed.
Can run this before and after segwit activation."""

NUM_SEGWIT_VERSIONS = 17 # will test OP_0, OP1, ..., OP_16
@@ -1165,18 +1166,17 @@ def test_segwit_versions(self):
assert len(self.nodes[0].getrawmempool()) == 0

# Finally, verify that version 0 -> version 1 transactions
# are non-standard
# are standard
script_pubkey = CScript([CScriptOp(OP_1), witness_hash])
tx2 = CTransaction() = [CTxIn(COutPoint(tx.sha256, 0), b"")]
tx2.vout = [CTxOut(tx.vout[0].nValue - 1000, script_pubkey)]
tx2.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
# Gets accepted to test_node, because standardness of outputs isn't
# checked with fRequireStandard
# Gets accepted to both policy-enforcing nodes and others.
test_transaction_acceptance(self.nodes[0], self.test_node, tx2, with_witness=True, accepted=True)
test_transaction_acceptance(self.nodes[1], self.std_node, tx2, with_witness=True, accepted=False)
test_transaction_acceptance(self.nodes[1], self.std_node, tx2, with_witness=True, accepted=True)
temp_utxo.pop() # last entry in temp_utxo was the output we just spent
temp_utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

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