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BIP112: Implement CHECKSEQUENCEVERIFY

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- Replace NOP3 with CHECKSEQUENCEVERIFY (BIP112)
  <nSequence> CHECKSEQUENCEVERIFY -> <nSequence>
- Fails if txin.nSequence < nSequence, allowing funds of a txout to be locked for a number of blocks or a duration of time after its inclusion in a block.
- Pull most of CheckLockTime() out into VerifyLockTime(), a local function that will be reused for CheckSequence()
- Add bitwise AND operator to CScriptNum
- Enable CHECKSEQUENCEVERIFY as a standard script verify flag
- Transactions that fail CSV verification will be rejected from the mempool, making it easy to test the feature. However blocks containing "invalid" CSV-using transactions will still be accepted; this is *not* the soft-fork required to actually enable CSV for production use.
This commit is contained in:
Mark Friedenbach
2015-09-25 16:18:51 -07:00
committed by BtcDrak
parent 80d1f2e483
commit 53e53a33c9
8 changed files with 247 additions and 9 deletions
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89
src/script/interpreter.cpp
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@@ -373,7 +373,44 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
break;
}
case OP_NOP1: case OP_NOP3: case OP_NOP4: case OP_NOP5:
case OP_CHECKSEQUENCEVERIFY:
{
if (!(flags & SCRIPT_VERIFY_CHECKSEQUENCEVERIFY)) {
// not enabled; treat as a NOP3
if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
}
break;
}
if (stack.size() < 1)
return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
// nSequence, like nLockTime, is a 32-bit unsigned integer
// field. See the comment in CHECKLOCKTIMEVERIFY regarding
// 5-byte numeric operands.
const CScriptNum nSequence(stacktop(-1), fRequireMinimal, 5);
// In the rare event that the argument may be < 0 due to
// some arithmetic being done first, you can always use
// 0 MAX CHECKSEQUENCEVERIFY.
if (nSequence < 0)
return set_error(serror, SCRIPT_ERR_NEGATIVE_LOCKTIME);
// To provide for future soft-fork extensibility, if the
// operand has the disabled lock-time flag set,
// CHECKSEQUENCEVERIFY behaves as a NOP.
if ((nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) != 0)
break;
// Compare the specified sequence number with the input.
if (!checker.CheckSequence(nSequence))
return set_error(serror, SCRIPT_ERR_UNSATISFIED_LOCKTIME);
break;
}
case OP_NOP1: case OP_NOP4: case OP_NOP5:
case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
{
if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS)
@@ -1120,27 +1157,33 @@ bool TransactionSignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn
return true;
}
bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) const
static bool VerifyLockTime(int64_t txToLockTime, int64_t nThreshold, const CScriptNum& nLockTime)
{
// There are two kinds of nLockTime: lock-by-blockheight
// and lock-by-blocktime, distinguished by whether
// nLockTime < LOCKTIME_THRESHOLD.
// nLockTime < nThreshold (either LOCKTIME_THRESHOLD or
// CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG).
//
// We want to compare apples to apples, so fail the script
// unless the type of nLockTime being tested is the same as
// the nLockTime in the transaction.
if (!(
(txTo->nLockTime < LOCKTIME_THRESHOLD && nLockTime < LOCKTIME_THRESHOLD) ||
(txTo->nLockTime >= LOCKTIME_THRESHOLD && nLockTime >= LOCKTIME_THRESHOLD)
(txToLockTime < nThreshold && nLockTime < nThreshold) ||
(txToLockTime >= nThreshold && nLockTime >= nThreshold)
))
return false;
// Now that we know we're comparing apples-to-apples, the
// comparison is a simple numeric one.
if (nLockTime > (int64_t)txTo->nLockTime)
if (nLockTime > txToLockTime)
return false;
// Finally the nLockTime feature can be disabled and thus
return true;
}
bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) const
{
// The nLockTime feature can be disabled and thus
// CHECKLOCKTIMEVERIFY bypassed if every txin has been
// finalized by setting nSequence to maxint. The
// transaction would be allowed into the blockchain, making
@@ -1153,6 +1196,38 @@ bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) con
if (CTxIn::SEQUENCE_FINAL == txTo->vin[nIn].nSequence)
return false;
if (!::VerifyLockTime((int64_t)txTo->nLockTime, LOCKTIME_THRESHOLD, nLockTime))
return false;
return true;
}
bool TransactionSignatureChecker::CheckSequence(const CScriptNum& nSequence) const
{
// Relative lock times are supported by comparing the passed
// in operand to the sequence number of the input.
const int64_t txToSequence = (int64_t)txTo->vin[nIn].nSequence;
// Fail if the transaction's version number is not set high
// enough to trigger BIP 68 rules.
if (static_cast<uint32_t>(txTo->nVersion) < 2)
return false;
// Sequence numbers with their most significant bit set are not
// consensus constrained. Testing that the transaction's sequence
// number do not have this bit set prevents using this property
// to get around a CHECKSEQUENCEVERIFY check.
if (txToSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG)
return false;
// Mask off any bits that do not have consensus-enforced meaning
// before doing the integer comparisons of ::VerifyLockTime.
const uint32_t nLockTimeMask = CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG
| CTxIn::SEQUENCE_LOCKTIME_MASK;
if (!::VerifyLockTime(txToSequence & nLockTimeMask, CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG, nSequence & nLockTimeMask))
return false;
return true;
}