Merge 338b9d82dc into merged_master (Bitcoin PR bitcoin/bitcoin#30681)

doc/release-notes-30647.md

@@ -0,0 +1,4 @@
+Tests
+-----
+
+- The BIP94 timewarp attack mitigation is now active on the `regtest` network

src/consensus/consensus.h

@@ -27,4 +27,11 @@ static const size_t MIN_SERIALIZABLE_TRANSACTION_WEIGHT = WITNESS_SCALE_FACTOR *
 /** Interpret sequence numbers as relative lock-time constraints. */
 static constexpr unsigned int LOCKTIME_VERIFY_SEQUENCE = (1 << 0);
 
+/**
+ * Maximum number of seconds that the timestamp of the first
+ * block of a difficulty adjustment period is allowed to
+ * be earlier than the last block of the previous period (BIP94).
+ */
+static constexpr int64_t MAX_TIMEWARP = 600;
+
 #endif // BITCOIN_CONSENSUS_CONSENSUS_H

src/consensus/params.h

@@ -122,6 +122,10 @@ struct Params {
     /** Proof of work parameters */
     uint256 powLimit;
     bool fPowAllowMinDifficultyBlocks;
+    /**
+      * Enfore BIP94 timewarp attack mitigation. On testnet4 this also enforces
+      * the block storm mitigation.
+      */
     bool enforce_BIP94;
     bool fPowNoRetargeting;
     int64_t nPowTargetSpacing;

src/kernel/chainparams.cpp

@@ -762,10 +762,10 @@ public:
         consensus.SegwitHeight = 0; // Always active unless overridden
         consensus.MinBIP9WarningHeight = 0;
         consensus.powLimit = uint256{"7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};
-        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
+        consensus.nPowTargetTimespan = 24 * 60 * 60; // one day
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = true;
-        consensus.enforce_BIP94 = false;
+        consensus.enforce_BIP94 = true;
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)

src/node/miner.cpp

@@ -45,6 +45,14 @@ int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParam
     int64_t nOldTime = pblock->nTime;
     int64_t nNewTime{std::max<int64_t>(pindexPrev->GetMedianTimePast() + 1, TicksSinceEpoch<std::chrono::seconds>(NodeClock::now()))};
 
+    if (consensusParams.enforce_BIP94) {
+        // Height of block to be mined.
+        const int height{pindexPrev->nHeight + 1};
+        if (height % consensusParams.DifficultyAdjustmentInterval() == 0) {
+            nNewTime = std::max<int64_t>(nNewTime, pindexPrev->GetBlockTime() - MAX_TIMEWARP);
+        }
+    }
+
     if (nOldTime < nNewTime) {
         pblock->nTime = nNewTime;
     }

src/validation.cpp

@@ -114,13 +114,6 @@ const std::vector<std::string> CHECKLEVEL_DOC {
  * */
 static constexpr int PRUNE_LOCK_BUFFER{10};
 
-/**
- * Maximum number of seconds that the timestamp of the first
- * block of a difficulty adjustment period is allowed to
- * be earlier than the last block of the previous period (BIP94).
- */
-static constexpr int64_t MAX_TIMEWARP = 600;
-
 GlobalMutex g_best_block_mutex;
 std::condition_variable g_best_block_cv;
 uint256 g_best_block;
@@ -4775,7 +4768,7 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, BlockValidatio
         return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER, "bad-header-height");
     }
     
-    // Testnet4 only: Check timestamp against prev for difficulty-adjustment
+    // Testnet4 and regtest only: Check timestamp against prev for difficulty-adjustment
     // blocks to prevent timewarp attacks (see https://github.com/bitcoin/bitcoin/pull/15482).
     if (consensusParams.enforce_BIP94) {
         // Check timestamp for the first block of each difficulty adjustment

test/functional/mining_basic.py

@@ -28,12 +28,16 @@ from test_framework.p2p import P2PDataStore
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
+    assert_greater_than_or_equal,
     assert_raises_rpc_error,
     get_fee,
 )
 from test_framework.wallet import MiniWallet
 
 
+DIFFICULTY_ADJUSTMENT_INTERVAL = 144
+MAX_FUTURE_BLOCK_TIME = 2 * 3600
+MAX_TIMEWARP = 600
 VERSIONBITS_TOP_BITS = 0x20000000
 VERSIONBITS_DEPLOYMENT_TESTDUMMY_BIT = 28
 DEFAULT_BLOCK_MIN_TX_FEE = 100  # default `-blockmintxfee` setting [sat/kvB] # ELEMENTS
@@ -115,6 +119,47 @@ class MiningTest(BitcoinTestFramework):
             assert tx_below_min_feerate['txid'] not in block_template_txids
             assert tx_below_min_feerate['txid'] not in block_txids
 
+    def test_timewarp(self):
+        self.log.info("Test timewarp attack mitigation (BIP94)")
+        node = self.nodes[0]
+
+        self.log.info("Mine until the last block of the retarget period")
+        blockchain_info = self.nodes[0].getblockchaininfo()
+        n = DIFFICULTY_ADJUSTMENT_INTERVAL - blockchain_info['blocks'] % DIFFICULTY_ADJUSTMENT_INTERVAL - 2
+        t = blockchain_info['time']
+
+        for _ in range(n):
+            t += 600
+            self.nodes[0].setmocktime(t)
+            self.generate(self.wallet, 1, sync_fun=self.no_op)
+
+        self.log.info("Create block two hours in the future")
+        self.nodes[0].setmocktime(t + MAX_FUTURE_BLOCK_TIME)
+        self.generate(self.wallet, 1, sync_fun=self.no_op)
+        assert_equal(node.getblock(node.getbestblockhash())['time'], t + MAX_FUTURE_BLOCK_TIME)
+
+        self.log.info("First block template of retarget period can't use wall clock time")
+        self.nodes[0].setmocktime(t)
+        # The template will have an adjusted timestamp, which we then modify
+        tmpl = node.getblocktemplate(NORMAL_GBT_REQUEST_PARAMS)
+        assert_greater_than_or_equal(tmpl['curtime'], t + MAX_FUTURE_BLOCK_TIME - MAX_TIMEWARP)
+
+        block = CBlock()
+        block.nVersion = tmpl["version"]
+        block.hashPrevBlock = int(tmpl["previousblockhash"], 16)
+        block.nTime = tmpl["curtime"]
+        block.nBits = int(tmpl["bits"], 16)
+        block.block_height = node.getblockcount()+1
+        block.nNonce = 0
+        block.vtx = [create_coinbase(height=int(tmpl["height"]))]
+        block.solve()
+        assert_template(node, block, None)
+
+        bad_block = copy.deepcopy(block)
+        bad_block.nTime = t
+        bad_block.solve()
+        assert_raises_rpc_error(-25, 'time-timewarp-attack', lambda: node.submitheader(hexdata=CBlockHeader(bad_block).serialize().hex()))
+
     def run_test(self):
         node = self.nodes[0]
         self.wallet = MiniWallet(node)
@@ -330,6 +375,7 @@ class MiningTest(BitcoinTestFramework):
         assert_equal(node.submitblock(hexdata=block.serialize().hex()), 'duplicate')  # valid
 
         self.test_blockmintxfee_parameter()
+        self.test_timewarp()
 
 
 if __name__ == '__main__':

test/functional/rpc_blockchain.py

@@ -59,7 +59,7 @@ TIME_RANGE_STEP = 600  # ten-minute steps
 TIME_RANGE_MTP = TIME_GENESIS_BLOCK + (HEIGHT - 6) * TIME_RANGE_STEP
 TIME_RANGE_TIP = TIME_GENESIS_BLOCK + (HEIGHT - 1) * TIME_RANGE_STEP
 TIME_RANGE_END = TIME_GENESIS_BLOCK + HEIGHT * TIME_RANGE_STEP
-DIFFICULTY_ADJUSTMENT_INTERVAL = 2016
+DIFFICULTY_ADJUSTMENT_INTERVAL = 144
 
 
 class BlockchainTest(BitcoinTestFramework):