Replace NOP2 with CHECKLOCKTIMEVERIFY

petertodd · petertodd · commit ab0f54f38e08 · 2014-09-29T03:44:25.000-04:00
&lt;nLockTime&gt; CHECKLOCKTIMEVERIFY -&gt; &lt;nLockTime&gt;

Fails if tx.nLockTime &lt; nLockTime, allowing the funds in a txout to be
locked until some block height or block time in the future is reached.

Only the logic and unittests are implemented; this commit does not have
any actual soft-fork logic in it.

Credit goes to Gregory Maxwell for the suggestion of comparing the
argument against the transaction nLockTime rather than the current
time/blockheight directly.
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
@@ -217,7 +217,77 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
                 // Control
                 //
                 case OP_NOP:
-                case OP_NOP1: case OP_NOP2: case OP_NOP3: case OP_NOP4: case OP_NOP5:
+                case OP_NOP1:
+                    break;
+                case OP_NOP2:
+                {
+                    // CHECKLOCKTIMEVERIFY
+                    //
+                    // (nLockTime -- nLockTime )
+
+                    if (!(flags & SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY))
+                        break; // not enabled; treat as a NOP
+
+                    if (stack.size() < 1)
+                        return false;
+
+                    // Note that elsewhere numeric opcodes are limited to
+                    // operands in the range -2**31+1 to 2**31-1, however it is
+                    // legal for opcodes to produce results exceeding that
+                    // range. This limitation is implemented by CScriptNum's
+                    // default 4-byte limit.
+                    //
+                    // If we kept to that limit we'd have a year 2038 problem,
+                    // even though the nLockTime field in transactions
+                    // themselves is uint32 which only becomes meaningless
+                    // after the year 2106.
+                    //
+                    // Thus as a special case we tell CScriptNum to accept up
+                    // to 5-byte bignums, which are good until 2**32-1, the
+                    // same limit as the nLockTime field itself.
+                    const CScriptNum nLockTime(stacktop(-1), 5);
+
+                    // In the rare event that the argument may be < 0 due to
+                    // some arithmetic being done first, you can always use
+                    // 0 MAX CHECKLOCKTIMEVERIFY.
+                    if (nLockTime < 0)
+                        return false;
+
+                    // There are two times of nLockTime: lock-by-blockheight
+                    // and lock-by-blocktime, distinguished by whether
+                    // nLockTime < LOCKTIME_THRESHOLD.
+                    //
+                    // 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)
+                         ))
+                        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)
+                        return false;
+
+                    // Finally 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
+                    // the opcode ineffective.
+                    //
+                    // Testing if this vin is not final is sufficient to
+                    // prevent this condition. Alternatively we could test all
+                    // inputs, but testing just this input minimizes the data
+                    // required to prove correct CHECKLOCKTIMEVERIFY execution.
+                    if (txTo.vin[nIn].IsFinal())
+                        return false;
+
+                    break;
+
+                }
+                case OP_NOP3: case OP_NOP4: case OP_NOP5:
                 case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
                 break;
 
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
@@ -32,6 +32,7 @@ enum
     SCRIPT_VERIFY_LOW_S     = (1U << 2), // enforce low S values (<n/2) in signatures (depends on STRICTENC)
     SCRIPT_VERIFY_NOCACHE   = (1U << 3), // do not store results in signature cache (but do query it)
     SCRIPT_VERIFY_NULLDUMMY = (1U << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
+    SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY = (1U << 5), // support CHECKLOCKTIMEVERIFY opcode
 };
 
 bool IsCanonicalPubKey(const std::vector<unsigned char> &vchPubKey, unsigned int flags);
diff --git a/src/test/data/tx_invalid.json b/src/test/data/tx_invalid.json
@@ -103,5 +103,71 @@
 [[["ad503f72c18df5801ee64d76090afe4c607fb2b822e9b7b63c5826c50e22fc3b", 0, "0x21 0x027c3a97665bf283a102a587a62a30a0c102d4d3b141015e2cae6f64e2543113e5 CHECKSIG NOT"]],
 "01000000013bfc220ec526583cb6b7e922b8b27f604cfe0a09764de61e80f58dc1723f50ad0000000000ffffffff0101000000000000002321027c3a97665bf283a102a587a62a30a0c102d4d3b141015e2cae6f64e2543113e5ac00000000", "P2SH"],
 
+
+["CHECKLOCKTIMEVERIFY tests"],
+
+["By-height locks, with argument just beyond tx nLockTime"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "1 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "499999999 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000fe64cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["By-time locks, with argument just beyond tx nLockTime (but within numerical boundries)"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "500000001 NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "4294967295 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000feffffff", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Argument missing"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Argument negative with by-blockheight nLockTime=0"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "-1 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Argument negative with by-blocktime nLockTime=500,000,000"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "-1 NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Input locked"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000ffffffff0100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Another input being unlocked isn't sufficient; the CHECKLOCKTIMEVERIFY-using input must be unlocked"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"] ,
+  ["0000000000000000000000000000000000000000000000000000000000000200", 1, "1"]],
+"010000000200010000000000000000000000000000000000000000000000000000000000000000000000ffffffff00020000000000000000000000000000000000000000000000000000000000000100000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Argument/tx height/time mismatch, both versions"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "499999999 NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "500000000 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "500000000 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ff64cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Argument 2^32 with nLockTime=2^32-1"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "4294967296 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ffffffff", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Same, but with nLockTime=2^31-1"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "2147483648 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ffffff7f", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["6 byte non-minimally-encoded arguments are invalid even in their contents are valid"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0x06 0x000000000000 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Failure due to failing CHECKLOCKTIMEVERIFY in scriptSig"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000251b1000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Failure due to failing CHECKLOCKTIMEVERIFY in redeemScript"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "HASH160 0x14 0xc5b93064159b3b2d6ab506a41b1f50463771b988 EQUAL"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000030251b1000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
 ["Make diffs cleaner by leaving a comment here without comma at the end"]
 ]
diff --git a/src/test/data/tx_valid.json b/src/test/data/tx_valid.json
@@ -178,5 +178,47 @@
 "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", "P2SH"],
 
 
+["CHECKLOCKTIMEVERIFY tests"],
+
+["By-height locks, with argument == 0 and == tx nLockTime"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "499999999 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ff64cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ff64cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["By-time locks, with argument just beyond tx nLockTime (but within numerical boundries)"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "500000000 NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "4294967295 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ffffffff", "P2SH,CHECKLOCKTIMEVERIFY"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "500000000 NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000ffffffff", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Any non-maxint nSequence is fine"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000feffffff0100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["The argument can be calculated rather than created directly by a PUSHDATA"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "499999999 1ADD NOP2 1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000065cd1d", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Perhaps even by an ADD producing a 5-byte result that is out of bounds for other opcodes"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "2147483647 2147483647 ADD NOP2 1"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000feffffff", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["5 byte non-minimally-encoded arguments are valid"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "0x05 0x0000000000 NOP2 1"]],
+"010000000100010000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Valid CHECKLOCKTIMEVERIFY in scriptSig"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "1"]],
+"01000000010001000000000000000000000000000000000000000000000000000000000000000000000251b1000000000100000000000000000001000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
+["Valid CHECKLOCKTIMEVERIFY in redeemScript"],
+[[["0000000000000000000000000000000000000000000000000000000000000100", 0, "HASH160 0x14 0xc5b93064159b3b2d6ab506a41b1f50463771b988 EQUAL"]],
+"0100000001000100000000000000000000000000000000000000000000000000000000000000000000030251b1000000000100000000000000000001000000", "P2SH,CHECKLOCKTIMEVERIFY"],
+
 ["Make diffs cleaner by leaving a comment here without comma at the end"]
 ]
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
@@ -40,6 +40,7 @@ unsigned int ParseScriptFlags(string strFlags){
         mapFlagNames["STRICTENC"] = SCRIPT_VERIFY_STRICTENC;
         mapFlagNames["LOW_S"] = SCRIPT_VERIFY_LOW_S;
         mapFlagNames["NULLDUMMY"] = SCRIPT_VERIFY_NULLDUMMY;
+        mapFlagNames["CHECKLOCKTIMEVERIFY"] = SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
     }
 
     BOOST_FOREACH(string word, words)

Original file line number	Diff line number	Diff line change
`@@ -40,6 +40,7 @@ unsigned int ParseScriptFlags(string strFlags){`
`40`	`40`	`mapFlagNames["STRICTENC"] = SCRIPT_VERIFY_STRICTENC;`
`41`	`41`	`mapFlagNames["LOW_S"] = SCRIPT_VERIFY_LOW_S;`
`42`	`42`	`mapFlagNames["NULLDUMMY"] = SCRIPT_VERIFY_NULLDUMMY;`
	`43`	`+ mapFlagNames["CHECKLOCKTIMEVERIFY"] = SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;`
`43`	`44`	`}`
`44`	`45`
`45`	`46`	`BOOST_FOREACH(string word, words)`