multi: add testnet4 support

Adds support of the Bitcoin testnet version 4 chain.
Reference: https://bips.dev/94/

Author: bullet-tooth

.gitignore

@@ -46,6 +46,8 @@ btcutil/psbt/coverage.txt
 *.swo
 /.vim
 
+.idea
+
 # Binaries produced by "make build"
 /addblock
 /btcctl

blockchain/difficulty.go

@@ -191,12 +191,22 @@ func calcNextRequiredDifficulty(lastNode HeaderCtx, newBlockTime time.Time,
 		adjustedTimespan = c.MaxRetargetTimespan()
 	}
 
+	var oldTarget *big.Int
+	// Special difficulty rule for Testnet4
+	if c.ChainParams().EnforceBIP94 {
+		// Here we use the first block of the difficulty period. This way
+		// the real difficulty is always preserved in the first block as
+		// it is not allowed to use the min-difficulty exception.
+		oldTarget = CompactToBig(firstNode.Bits())
+	} else {
+		oldTarget = CompactToBig(lastNode.Bits())
+	}
+
 	// Calculate new target difficulty as:
 	//  currentDifficulty * (adjustedTimespan / targetTimespan)
 	// The result uses integer division which means it will be slightly
 	// rounded down.  Bitcoind also uses integer division to calculate this
 	// result.
-	oldTarget := CompactToBig(lastNode.Bits())
 	newTarget := new(big.Int).Mul(oldTarget, big.NewInt(adjustedTimespan))
 	targetTimeSpan := int64(c.ChainParams().TargetTimespan / time.Second)
 	newTarget.Div(newTarget, big.NewInt(targetTimeSpan))

blockchain/error.go

@@ -220,6 +220,8 @@ const (
 	// current chain tip. This is not a block validation rule, but is required
 	// for block proposals submitted via getblocktemplate RPC.
 	ErrPrevBlockNotBest
+
+	ErrTimewarpAttack
 )
 
 // Map of ErrorCode values back to their constant names for pretty printing.

blockchain/validate.go

@@ -46,6 +46,11 @@ const (
 	// coinbaseHeightAllocSize is the amount of bytes that the
 	// ScriptBuilder will allocate when validating the coinbase height.
 	coinbaseHeightAllocSize = 5
+
+	// maxTimeWarp is a 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).
+	maxTimeWarp = 600 * time.Second
 )
 
 var (
@@ -85,7 +90,7 @@ func ShouldHaveSerializedBlockHeight(header *wire.BlockHeader) bool {
 
 // IsCoinBaseTx determines whether or not a transaction is a coinbase.  A coinbase
 // is a special transaction created by miners that has no inputs.  This is
-// represented in the block chain by a transaction with a single input that has
+// represented in the blockchain by a transaction with a single input that has
 // a previous output transaction index set to the maximum value along with a
 // zero hash.
 //
@@ -109,7 +114,7 @@ func IsCoinBaseTx(msgTx *wire.MsgTx) bool {
 
 // IsCoinBase determines whether or not a transaction is a coinbase.  A coinbase
 // is a special transaction created by miners that has no inputs.  This is
-// represented in the block chain by a transaction with a single input that has
+// represented in the blockchain by a transaction with a single input that has
 // a previous output transaction index set to the maximum value along with a
 // zero hash.
 //
@@ -446,7 +451,7 @@ func CheckBlockHeaderSanity(header *wire.BlockHeader, powLimit *big.Int,
 	// A block timestamp must not have a greater precision than one second.
 	// This check is necessary because Go time.Time values support
 	// nanosecond precision whereas the consensus rules only apply to
-	// seconds and it's much nicer to deal with standard Go time values
+	// seconds, and it's much nicer to deal with standard Go time values
 	// instead of converting to seconds everywhere.
 	if !header.Timestamp.Equal(time.Unix(header.Timestamp.Unix(), 0)) {
 		str := fmt.Sprintf("block timestamp of %v has a higher "+
@@ -669,7 +674,7 @@ func compareScript(height int32, script []byte) error {
 }
 
 // CheckBlockHeaderContext performs several validation checks on the block header
-// which depend on its position within the block chain.
+// which depend on its position within the blockchain.
 //
 // The flags modify the behavior of this function as follows:
 //   - BFFastAdd: All checks except those involving comparing the header against
@@ -684,6 +689,10 @@ func compareScript(height int32, script []byte) error {
 func CheckBlockHeaderContext(header *wire.BlockHeader, prevNode HeaderCtx,
 	flags BehaviorFlags, c ChainCtx, skipCheckpoint bool) error {
 
+	// The height of this block is one more than the referenced previous
+	// block.
+	blockHeight := prevNode.Height() + 1
+
 	fastAdd := flags&BFFastAdd == BFFastAdd
 	if !fastAdd {
 		// Ensure the difficulty specified in the block header matches
@@ -710,11 +719,22 @@ func CheckBlockHeaderContext(header *wire.BlockHeader, prevNode HeaderCtx,
 			str = fmt.Sprintf(str, header.Timestamp, medianTime)
 			return ruleError(ErrTimeTooOld, str)
 		}
-	}
 
-	// The height of this block is one more than the referenced previous
-	// block.
-	blockHeight := prevNode.Height() + 1
+		// Testnet4 only: Check timestamp against prev for difficulty-adjustment
+		// blocks to prevent timewarp attacks.
+		if c.ChainParams().EnforceBIP94 {
+			// Check timestamp for the first block of each difficulty adjustment
+			// interval, except the genesis block.
+			if blockHeight%c.BlocksPerRetarget() == 0 {
+				prevBlockTimestamp := time.Unix(prevNode.Timestamp(), 0)
+				if header.Timestamp.Before(prevBlockTimestamp.Add(-maxTimeWarp)) {
+					str := "block's timestamp %v is too early on diff adjustment block %v"
+					str = fmt.Sprintf(str, header.Timestamp, prevBlockTimestamp)
+					return ruleError(ErrTimewarpAttack, str)
+				}
+			}
+		}
+	}
 
 	// Reject outdated block versions once a majority of the network
 	// has upgraded.  These were originally voted on by BIP0034,
@@ -762,7 +782,7 @@ func CheckBlockHeaderContext(header *wire.BlockHeader, prevNode HeaderCtx,
 }
 
 // checkBlockContext performs several validation checks on the block which depend
-// on its position within the block chain.
+// on its position within the blockchain.
 //
 // The flags modify the behavior of this function as follows:
 //   - BFFastAdd: The transaction are not checked to see if they are finalized
@@ -1067,7 +1087,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block, vi
 	//
 	// In addition, as of BIP0034, duplicate coinbases are no longer
 	// possible due to its requirement for including the block height in the
-	// coinbase and thus it is no longer possible to create transactions
+	// coinbase, and thus it is no longer possible to create transactions
 	// that 'overwrite' older ones.  Therefore, only enforce the rule if
 	// BIP0034 is not yet active.  This is a useful optimization because the
 	// BIP0030 check is expensive since it involves a ton of cache misses in
@@ -1230,7 +1250,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block, vi
 	if csvState == ThresholdActive {
 		// If the CSV soft-fork is now active, then modify the
 		// scriptFlags to ensure that the CSV op code is properly
-		// validated during the script checks bleow.
+		// validated during the script checks below.
 		scriptFlags |= txscript.ScriptVerifyCheckSequenceVerify
 
 		// We obtain the MTP of the *previous* block in order to

btcd.go

@@ -64,6 +64,11 @@ func btcdMain(serverChan chan<- *server) error {
 	// Show version at startup.
 	btcdLog.Infof("Version %s", version())
 
+	if cfg.TestNet3 {
+		btcdLog.Warn("Support for testnet3 is deprecated and will be removed in an upcoming release. " +
+			"Consider switching to testnet4.")
+	}
+
 	// Enable http profiling server if requested.
 	if cfg.Profile != "" {
 		go func() {

chaincfg/genesis.go

@@ -143,6 +143,77 @@ var testNet3GenesisBlock = wire.MsgBlock{
 	Transactions: []*wire.MsgTx{&genesisCoinbaseTx},
 }
 
+// testNet4GenesisTx is the transaction for the genesis blocks for test network (version 4).
+var testNet4GenesisTx = wire.MsgTx{
+	Version: 1,
+	TxIn: []*wire.TxIn{
+		{
+			PreviousOutPoint: wire.OutPoint{
+				Hash:  chainhash.Hash{},
+				Index: 0xffffffff,
+			},
+			SignatureScript: []byte{
+				// Message: `03/May/2024 000000000000000000001ebd58c244970b3aa9d783bb001011fbe8ea8e98e00e`
+				0x4, 0xff, 0xff, 0x0, 0x1d, 0x1, 0x4, 0x4c,
+				0x4c, 0x30, 0x33, 0x2f, 0x4d, 0x61, 0x79, 0x2f,
+				0x32, 0x30, 0x32, 0x34, 0x20, 0x30, 0x30, 0x30,
+				0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+				0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+				0x30, 0x31, 0x65, 0x62, 0x64, 0x35, 0x38, 0x63,
+				0x32, 0x34, 0x34, 0x39, 0x37, 0x30, 0x62, 0x33,
+				0x61, 0x61, 0x39, 0x64, 0x37, 0x38, 0x33, 0x62,
+				0x62, 0x30, 0x30, 0x31, 0x30, 0x31, 0x31, 0x66,
+				0x62, 0x65, 0x38, 0x65, 0x61, 0x38, 0x65, 0x39,
+				0x38, 0x65, 0x30, 0x30, 0x65},
+			Sequence: 0xffffffff,
+		},
+	},
+	TxOut: []*wire.TxOut{
+		{
+			Value: 0x12a05f200,
+			PkScript: []byte{
+				0x21, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+				0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+				0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+				0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+				0x0, 0x0, 0xac},
+		},
+	},
+	LockTime: 0,
+}
+
+// testNet4GenesisHash is the hash of the first block in the block chain for the
+// test network (version 4).
+var testNet4GenesisHash = chainhash.Hash([chainhash.HashSize]byte{
+	0x43, 0xf0, 0x8b, 0xda, 0xb0, 0x50, 0xe3, 0x5b,
+	0x56, 0x7c, 0x86, 0x4b, 0x91, 0xf4, 0x7f, 0x50,
+	0xae, 0x72, 0x5a, 0xe2, 0xde, 0x53, 0xbc, 0xfb,
+	0xba, 0xf2, 0x84, 0xda, 0x00, 0x00, 0x00, 0x00})
+
+// testNet4GenesisMerkleRoot is the hash of the first transaction in the genesis
+// block for the test network (version 4).  It is the same as the merkle root
+// for the main network.
+var testNet4GenesisMerkleRoot = chainhash.Hash([chainhash.HashSize]byte{ // Make go vet happy.
+	0x4e, 0x7b, 0x2b, 0x91, 0x28, 0xfe, 0x02, 0x91,
+	0xdb, 0x06, 0x93, 0xaf, 0x2a, 0xe4, 0x18, 0xb7,
+	0x67, 0xe6, 0x57, 0xcd, 0x40, 0x7e, 0x80, 0xcb,
+	0x14, 0x34, 0x22, 0x1e, 0xae, 0xa7, 0xa0, 0x7a,
+})
+
+// testNet4GenesisBlock defines the genesis block of the block chain which
+// serves as the public transaction ledger for the test network (version 3).
+var testNet4GenesisBlock = wire.MsgBlock{
+	Header: wire.BlockHeader{
+		Version:    1,
+		PrevBlock:  chainhash.Hash{},          // 0000000000000000000000000000000000000000000000000000000000000000
+		MerkleRoot: testNet4GenesisMerkleRoot, // 4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b
+		Timestamp:  time.Unix(1714777860, 0),  // 2024-05-03 23:11:00 +0000 UTC
+		Bits:       0x1d00ffff,                // 486604799 [00000000ffff0000000000000000000000000000000000000000000000000000]
+		Nonce:      0x17780cbb,                // 393743547
+	},
+	Transactions: []*wire.MsgTx{&testNet4GenesisTx},
+}
+
 // simNetGenesisHash is the hash of the first block in the block chain for the
 // simulation test network.
 var simNetGenesisHash = chainhash.Hash([chainhash.HashSize]byte{ // Make go vet happy.

chaincfg/genesis_test.go

@@ -6,6 +6,7 @@ package chaincfg
 
 import (
 	"bytes"
+	"github.com/stretchr/testify/require"
 	"testing"
 
 	"github.com/davecgh/go-spew/spew"
@@ -91,6 +92,34 @@ func TestTestNet3GenesisBlock(t *testing.T) {
 	}
 }
 
+// TestTestNet4GenesisBlock tests the genesis block of the test network (version
+// 4) for validity by checking the encoded bytes and hashes.
+func TestTestNet4GenesisBlock(t *testing.T) {
+	// Encode the genesis block to raw bytes.
+	var buf bytes.Buffer
+	err := TestNet4Params.GenesisBlock.Serialize(&buf)
+	if err != nil {
+		t.Fatalf("TestTestNet4GenesisBlock: %v", err)
+	}
+
+	// Ensure the encoded block matches the expected bytes.
+	if !bytes.Equal(buf.Bytes(), testNet4GenesisBlockBytes) {
+		t.Fatalf("TestTestNet4GenesisBlock: Genesis block does not "+
+			"appear valid - got %v, want %v",
+			spew.Sdump(buf.Bytes()),
+			spew.Sdump(testNet4GenesisBlockBytes))
+	}
+
+	// Check hash of the block against expected hash.
+	hash := TestNet4Params.GenesisBlock.BlockHash()
+	if !TestNet4Params.GenesisHash.IsEqual(&hash) {
+		t.Fatalf("TestTestNet4GenesisBlock: Genesis block hash does "+
+			"not appear valid - got %v, want %v", spew.Sdump(hash),
+			spew.Sdump(TestNet4Params.GenesisHash))
+	}
+	require.Equal(t, "00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043", hash.String())
+}
+
 // TestSimNetGenesisBlock tests the genesis block of the simulation test network
 // for validity by checking the encoded bytes and hashes.
 func TestSimNetGenesisBlock(t *testing.T) {
@@ -268,6 +297,44 @@ var testNet3GenesisBlockBytes = []byte{
 	0xac, 0x00, 0x00, 0x00, 0x00, /* |.....|    */
 }
 
+// testNet4GenesisBlockBytes are the wire encoded bytes for the genesis block of
+// the test network (version 4)
+var testNet4GenesisBlockBytes = []byte{
+	0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x4e, 0x7b, 0x2b, 0x91,
+	0x28, 0xfe, 0x02, 0x91, 0xdb, 0x06, 0x93, 0xaf,
+	0x2a, 0xe4, 0x18, 0xb7, 0x67, 0xe6, 0x57, 0xcd,
+	0x40, 0x7e, 0x80, 0xcb, 0x14, 0x34, 0x22, 0x1e,
+	0xae, 0xa7, 0xa0, 0x7a, 0x04, 0x6f, 0x35, 0x66,
+	0xff, 0xff, 0x00, 0x1d, 0xbb, 0x0c, 0x78, 0x17,
+	0x01, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
+	0xff, 0xff, 0x55, 0x04, 0xff, 0xff, 0x00, 0x1d,
+	0x01, 0x04, 0x4c, 0x4c, 0x30, 0x33, 0x2f, 0x4d,
+	0x61, 0x79, 0x2f, 0x32, 0x30, 0x32, 0x34, 0x20,
+	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+	0x30, 0x30, 0x30, 0x30, 0x31, 0x65, 0x62, 0x64,
+	0x35, 0x38, 0x63, 0x32, 0x34, 0x34, 0x39, 0x37,
+	0x30, 0x62, 0x33, 0x61, 0x61, 0x39, 0x64, 0x37,
+	0x38, 0x33, 0x62, 0x62, 0x30, 0x30, 0x31, 0x30,
+	0x31, 0x31, 0x66, 0x62, 0x65, 0x38, 0x65, 0x61,
+	0x38, 0x65, 0x39, 0x38, 0x65, 0x30, 0x30, 0x65,
+	0xff, 0xff, 0xff, 0xff, 0x01, 0x00, 0xf2, 0x05,
+	0x2a, 0x01, 0x00, 0x00, 0x00, 0x23, 0x21, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0xac, 0x00, 0x00, 0x00, 0x00,
+}
+
 // simNetGenesisBlockBytes are the wire encoded bytes for the genesis block of
 // the simulation test network as of protocol version 70002.
 var simNetGenesisBlockBytes = []byte{