native: add test for multisignature Koblitz witness verification

Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>

pkg/core/native/native_test/cryptolib_verification_test.go

@@ -2,6 +2,7 @@ package native_test
 
 import (
 	"math/big"
+	"sort"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames"
@@ -84,7 +85,7 @@ func TestCryptoLib_KoblitzVerificationScript(t *testing.T) {
 		require.True(t, pk.PublicKey().Verify(signature, native.Keccak256(msg).BytesBE()))
 
 		// Build invocation witness script for the user's account.
-		invBytes := buildKoblitzInvocationScript(t, signature)
+		invBytes := buildKoblitzInvocationScript(t, [][]byte{signature})
 
 		// Construct witness for signer #0 (the user itself).
 		tx.Scripts = []transaction.Witness{
@@ -512,22 +513,34 @@ func buildKoblitzVerificationScriptCompat(t *testing.T, pub *keys.PublicKey) []b
 	// 181      SYSCALL      System.Contract.Call (627d5b52)
 }
 
-// buildKoblitzInvocationScript builds witness invocation script for the transaction signature. The signature
+// buildKoblitzInvocationScript builds witness invocation script for the transaction signatures. The signature
 // itself may be produced by public key over any curve (not required Koblitz, the algorithm is the same).
-func buildKoblitzInvocationScript(t *testing.T, signature []byte) []byte {
+// The signatures expected to be sorted by public key (if multiple signatures are provided).
+func buildKoblitzInvocationScript(t *testing.T, signatures [][]byte) []byte {
 	//Exactly like during standard
 	// signature verification, the resulting script pushes Koblitz signature bytes onto stack.
 	inv := io.NewBufBinWriter()
-	emit.Bytes(inv.BinWriter, signature) // message signatre bytes.
+	for _, sig := range signatures {
+		emit.Bytes(inv.BinWriter, sig) // message signature bytes.
+	}
 	require.NoError(t, inv.Err)
 
 	return inv.Bytes()
-	// Here's an example of the resulting witness invocation script (66 bytes length, always constant length):
+	// Here's an example of the resulting single witness invocation script (66 bytes length, always constant length):
 	// NEO-GO-VM > loadbase64 DEBMGKU/MdSizlzaVNDUUbd1zMZQJ43eTaZ4vBCpmkJ/wVh1TYrAWEbFyHhkqq+aYxPCUS43NKJdJTXavcjB8sTP
 	// READY: loaded 66 instructions
 	// NEO-GO-VM 0 > ops
 	// INDEX    OPCODE       PARAMETER
 	// 0        PUSHDATA1    4c18a53f31d4a2ce5cda54d0d451b775ccc650278dde4da678bc10a99a427fc158754d8ac05846c5c87864aaaf9a6313c2512e3734a25d2535dabdc8c1f2c4cf    <<
+	//
+	// Here's an example of the 3 out of 4 multisignature invocation script (66 * m bytes length, always constant length):
+	// NEO-GO-VM > loadbase64 DEBsPMY3+7sWyZf0gCVcqPzwZ79p+KpeylgtbYIrXp4Tdi6E/8q3DIrEgK7DdVe3YdbfE+VPrpwym/ufBb8MRTB6DED5B9OZDGWdJApRfuy9LeUTa2mLsXP7mBRa181g0Jo7beylWzVgDqHHF2PilECMcLmRbFRknmQm4KgiGkDE+O6ZDEAYt61O2dMfasJHiQD95M5b4mR6NBnDsMTo2e59H3y4YguroVLiUxnQSc4qu9LWvEIKr4/ytjCCuANXOkJmSw8C
+	// READY: loaded 198 instructions
+	// NEO-GO-VM 0 > ops
+	// INDEX    OPCODE       PARAMETER
+	// 0        PUSHDATA1    6c3cc637fbbb16c997f480255ca8fcf067bf69f8aa5eca582d6d822b5e9e13762e84ffcab70c8ac480aec37557b761d6df13e54fae9c329bfb9f05bf0c45307a    <<
+	// 66       PUSHDATA1    f907d3990c659d240a517eecbd2de5136b698bb173fb98145ad7cd60d09a3b6deca55b35600ea1c71763e294408c70b9916c54649e6426e0a8221a40c4f8ee99
+	// 132      PUSHDATA1    18b7ad4ed9d31f6ac2478900fde4ce5be2647a3419c3b0c4e8d9ee7d1f7cb8620baba152e25319d049ce2abbd2d6bc420aaf8ff2b63082b803573a42664b0f02
 }
 
 // constructMessage constructs message for signing that consists of the
@@ -562,3 +575,305 @@ func constructMessageSimple(t *testing.T, magic uint32, tx hash.Hashable) []byte
 func constructMessageCompat(t *testing.T, magic uint32, tx hash.Hashable) []byte {
 	return hash.NetSha256(magic, tx).BytesBE()
 }
+
+// TestCryptoLib_KoblitzMultisigVerificationScript builds transaction with custom witness that contains
+// the Koblitz tx multisignature bytes and Koblitz multisignature verification script.
+// This test ensures that transaction signed by m out of n Koblitz keys passes verification and can
+// be successfully accepted to the chain.
+func TestCryptoLib_KoblitzMultisigVerificationScript(t *testing.T) {
+	check := func(
+		t *testing.T,
+		buildVerificationScript func(t *testing.T, m int, pub keys.PublicKeys) []byte,
+		constructMsg func(t *testing.T, magic uint32, tx hash.Hashable) []byte,
+	) {
+		c := newGasClient(t)
+		gasInvoker := c.WithSigners(c.Committee)
+		e := c.Executor
+
+		// Consider 4 users willing to sign 3/4 multisignature transaction Secp256k1 private keys.
+		const (
+			n = 4
+			m = 3
+		)
+		pks := make([]*keys.PrivateKey, n)
+		for i := range pks {
+			var err error
+			pks[i], err = keys.NewSecp256k1PrivateKey()
+			require.NoError(t, err)
+		}
+		// Sort private keys by their public keys.
+		sort.Slice(pks, func(i, j int) bool {
+			return pks[i].PublicKey().Cmp(pks[j].PublicKey()) < 0
+		})
+
+		// Firstly, we need to build the N3 multisig account address based on the users' public keys.
+		// Pubs must be sorted, exactly like for the standard CheckMultisig.
+		pubs := make(keys.PublicKeys, n)
+		for i := range pks {
+			pubs[i] = pks[i].PublicKey()
+		}
+		vrfBytes := buildVerificationScript(t, m, pubs)
+
+		// Construct the user's account script hash. It's effectively a verification script hash.
+		from := hash.Hash160(vrfBytes)
+
+		// Supply this account with some initial balance so that the user is able to pay for his transactions.
+		gasInvoker.Invoke(t, true, "transfer", c.Committee.ScriptHash(), from, 10000_0000_0000, nil)
+
+		// Construct transaction that transfers 5 GAS from the user's account to some other account.
+		to := util.Uint160{1, 2, 3}
+		amount := 5
+		tx := gasInvoker.PrepareInvokeNoSign(t, "transfer", from, to, amount, nil)
+		tx.Signers = []transaction.Signer{
+			{
+				Account: from,
+				Scopes:  transaction.CalledByEntry,
+			},
+		}
+		neotest.AddNetworkFee(t, e.Chain, tx)
+		neotest.AddSystemFee(e.Chain, tx, -1)
+
+		// Add some more network fee to pay for the witness verification. This value may be calculated precisely,
+		// but let's keep some inaccurate value for the test.
+		tx.NetworkFee += 900_0000
+
+		// This transaction (along with the network magic) should be signed by the user's Koblitz private key.
+		msg := constructMsg(t, uint32(e.Chain.GetConfig().Magic), tx)
+
+		// The users have to sign the hash of the message by their Koblitz key. Collect m signatures from first m keys.
+		// Signatures must be sorted by public key.
+		sigs := make([][]byte, m)
+		for i := range sigs {
+			j := i
+			if i > 0 {
+				j++ // Add some shift to ensure that verification script works correctly.
+			}
+			if i > 3 {
+				j++ // Add more shift for large number of public keys for the same purpose.
+			}
+			sigs[i] = pks[j].SignHash(native.Keccak256(msg))
+		}
+
+		// Build invocation witness script for the signatures.
+		invBytes := buildKoblitzInvocationScript(t, sigs)
+
+		// Construct witness for signer #0 (the multisig account itself).
+		tx.Scripts = []transaction.Witness{
+			{
+				InvocationScript:   invBytes,
+				VerificationScript: vrfBytes,
+			},
+		}
+
+		// Add transaction to the chain. No error is expected on new block addition. Note, that this line performs
+		// all those checks that are executed during transaction acceptance in the real network.
+		e.AddNewBlock(t, tx)
+
+		// Double-check: ensure funds have been transferred.
+		e.CheckGASBalance(t, to, big.NewInt(int64(amount)))
+	}
+
+	// The proposed multisig verification script.
+	// (261 bytes, 8389470 GAS including Invocation script execution for 3/4 multisig).
+	// The user has to sign the keccak256([4-bytes-network-magic-LE, txHash-bytes-BE]).
+	check(t, buildKoblitzMultisigVerificationScript, constructMessage)
+}
+
+// buildKoblitzMultisigVerificationScript builds witness verification script for m signatures out of n Koblitz public keys.
+// Public keys must be sorted. Signatures (pushed by witness Invocation script) must be sorted by public keys.
+// It checks m out of n multisignature of the following message:
+//
+//	keccak256([4-bytes-network-magic-LE, txHash-bytes-BE])
+func buildKoblitzMultisigVerificationScript(t *testing.T, m int, pubs keys.PublicKeys) []byte {
+	if len(pubs) == 0 {
+		t.Fatalf("empty pubs list")
+	}
+	if m > len(pubs) {
+		t.Fatalf("m must be not greater than the number of public keys")
+	}
+
+	n := len(pubs) // public keys must be sorted.
+	cryptoLibH := state.CreateNativeContractHash(nativenames.CryptoLib)
+
+	// In fact, the following algorithm is implemented via NeoVM instructions:
+	//
+	// func Check(sigs []interop.Signature) bool {
+	// 	if m != len(sigs) {
+	// 		return false
+	// 	}
+	// 	var pubs []interop.PublicKey = []interop.PublicKey{...}
+	// 	msg := append(convert.ToBytes(runtime.GetNetwork()), runtime.GetScriptContainer().Hash...)
+	// 	var sigCnt = 0
+	// 	var pubCnt = 0
+	// 	for ; sigCnt < m && pubCnt < n; { // sigs must be sorted by pub
+	// 		sigCnt += crypto.VerifyWithECDsa(msg, pubs[pubCnt], sigs[sigCnt], crypto.Secp256k1Keccak256)
+	// 		pubCnt++
+	// 	}
+	// 	return sigCnt == m
+	// }
+	vrf := io.NewBufBinWriter()
+
+	// Initialize slots for local variables. Locals slot scheme:
+	// LOC0 -> sigs
+	// LOC1 -> pubs
+	// LOC2 -> msg (ByteString)
+	// LOC3 -> sigCnt (Integer)
+	// LOC4 -> pubCnt (Integer)
+	emit.InitSlot(vrf.BinWriter, 5, 0)
+
+	// Check the number of signatures is m. Return false if not.
+	emit.Opcodes(vrf.BinWriter, opcode.DEPTH) // Push the number of signatures onto stack.
+	emit.Int(vrf.BinWriter, int64(m))
+	emit.Instruction(vrf.BinWriter, opcode.JMPEQ, []byte{0})            // here and below short jumps are sufficient.
+	sigsLenCheckEndOffset := vrf.Len()                                  // offset of the signatures count check.
+	emit.Opcodes(vrf.BinWriter, opcode.CLEAR, opcode.PUSHF, opcode.RET) // return if length of the signatures not equal to m.
+
+	// Start the check.
+	checkStartOffset := vrf.Len()
+
+	// Pack signatures and store at LOC0.
+	emit.Int(vrf.BinWriter, int64(m))
+	emit.Opcodes(vrf.BinWriter, opcode.PACK, opcode.STLOC0)
+
+	// Pack public keys and store at LOC1.
+	for _, pub := range pubs {
+		emit.Bytes(vrf.BinWriter, pub.Bytes())
+	}
+	emit.Int(vrf.BinWriter, int64(n))
+	emit.Opcodes(vrf.BinWriter, opcode.PACK, opcode.STLOC1)
+
+	// Get message and store it at LOC2.
+	// msg = [4-network-magic-bytes-LE, tx-hash-BE]
+	emit.Syscall(vrf.BinWriter, interopnames.SystemRuntimeGetNetwork) // push network magic (Integer stackitem), can have 0-5 bytes length serialized.
+	// Convert network magic to 4-bytes-length LE byte array representation.
+	emit.Int(vrf.BinWriter, 0x100000000)
+	emit.Opcodes(vrf.BinWriter, opcode.ADD, // some new number that is 5 bytes at least when serialized, but first 4 bytes are intact network value (LE).
+		opcode.PUSH4, opcode.LEFT) // cut the first 4 bytes out of a number that is at least 5 bytes long, the result is 4-bytes-length LE network representation.
+	// Retrieve executing transaction hash.
+	emit.Syscall(vrf.BinWriter, interopnames.SystemRuntimeGetScriptContainer) // push the script container (executing transaction, actually).
+	emit.Opcodes(vrf.BinWriter, opcode.PUSH0, opcode.PICKITEM)                // pick 0-th transaction item (the transaction hash).
+	// Concatenate network magic and transaction hash.
+	emit.Opcodes(vrf.BinWriter, opcode.CAT)    // this instruction will convert network magic to bytes using BigInteger rules of conversion.
+	emit.Opcodes(vrf.BinWriter, opcode.STLOC2) // store msg as a local variable #2.
+
+	// Initialize local variables: sigCnt, pubCnt.
+	emit.Opcodes(vrf.BinWriter, opcode.PUSH0, opcode.STLOC3, // initialize sigCnt.
+		opcode.PUSH0, opcode.STLOC4) // initialize pubCnt.
+
+	// Loop condition check.
+	loopStartOffset := vrf.Len()
+	emit.Opcodes(vrf.BinWriter, opcode.LDLOC3) // load sigCnt.
+	emit.Int(vrf.BinWriter, int64(m))          // push m.
+	emit.Opcodes(vrf.BinWriter, opcode.GE,     // sigCnt >= m
+		opcode.LDLOC4) // load pubCnt
+	emit.Int(vrf.BinWriter, int64(n))      // push n.
+	emit.Opcodes(vrf.BinWriter, opcode.GE, // pubCnt >= n
+		opcode.OR) // sigCnt >= m || pubCnt >= n
+	emit.Instruction(vrf.BinWriter, opcode.JMPIF, []byte{0}) // jump to the end of the script if (sigCnt >= m || pubCnt >= n).
+	loopConditionOffset := vrf.Len()
+
+	// Loop start. Prepare arguments and call CryptoLib's verifyWithECDsa.
+	emit.Int(vrf.BinWriter, int64(native.Secp256k1Keccak256)) // push Koblitz curve identifier.
+	emit.Opcodes(vrf.BinWriter, opcode.LDLOC0,                // load signatures.
+		opcode.LDLOC3,             // load sigCnt.
+		opcode.PICKITEM,           // pick signature at index sigCnt.
+		opcode.LDLOC1,             // load pubs.
+		opcode.LDLOC4,             // load pubCnt.
+		opcode.PICKITEM,           // pick pub at index pubCnt.
+		opcode.LDLOC2,             // load msg.
+		opcode.PUSH4, opcode.PACK) // pack 4 arguments for 'verifyWithECDsa' call.
+	emit.AppCallNoArgs(vrf.BinWriter, cryptoLibH, "verifyWithECDsa", callflag.All) // emit the call to 'verifyWithECDsa' itself.
+
+	// Update loop variables.
+	emit.Opcodes(vrf.BinWriter, opcode.LDLOC3, opcode.ADD, opcode.STLOC3, // increment sigCnt if signature is valid.
+		opcode.LDLOC4, opcode.INC, opcode.STLOC4) // increment pubCnt.
+
+	// End of the loop.
+	emit.Instruction(vrf.BinWriter, opcode.JMP, []byte{0}) // jump to the start of cycle.
+	loopEndOffset := vrf.Len()
+
+	// Return condition: the number of valid signatures should be equal to m.
+	progRetOffset := vrf.Len()
+	emit.Opcodes(vrf.BinWriter, opcode.LDLOC3)   // load sigCnt.
+	emit.Int(vrf.BinWriter, int64(m))            // push m.
+	emit.Opcodes(vrf.BinWriter, opcode.NUMEQUAL) // push m == sigCnt.
+
+	require.NoError(t, vrf.Err)
+	script := vrf.Bytes()
+
+	// Set JMP* instructions offsets. "-1" is for short JMP parameter offset. JMP parameters
+	// are relative offsets.
+	script[sigsLenCheckEndOffset-1] = byte(checkStartOffset - sigsLenCheckEndOffset + 2)
+	script[loopEndOffset-1] = byte(loopStartOffset - loopEndOffset + 2)
+	script[loopConditionOffset-1] = byte(progRetOffset - loopConditionOffset + 2)
+
+	return script
+	// Here's an example of the resulting single witness invocation script (261 bytes length, the length may vary depending on m/n):
+	// NEO-GO-VM > loadbase64 VwUAQxMoBUkJQBPAcAwhAnDdr99Ja4K3I81KURO2xs8b+dYYVIaMhbDFTYO4FCnKDCECuBwcms5bdqbWeBZ1cnMAJ8z/uUMcxnIK0CxTyxNdYqAMIQLQHl4aPx8PZOgu4EQUh0qCPaCfaZZPLNNS9ZVPcmuXpwwhA+YKTuJo6wB/u/CQdzJczfQQaMk6LHfMlSZMdBD2qCV1FMBxQcX7oOADAAAAAAEAAACeFI1BLVEIMBDOi3IQcxB0axO4bBS4kiRCABhoa85pbM5qFMAfDA92ZXJpZnlXaXRoRUNEc2EMFBv1dasRiWiEE2EKNaEohs3gtmxyQWJ9W1JrnnNsnHQiuWsTsw==
+	// READY: loaded 262 instructions
+	// NEO-GO-VM 0 > ops
+	// INDEX    OPCODE       PARAMETER
+	// 0        INITSLOT     5 local, 0 arg    <<
+	// 3        DEPTH
+	// 4        PUSH3
+	// 5        JMPEQ        10 (5/05)
+	// 7        CLEAR
+	// 8        PUSHF
+	// 9        RET
+	// 10       PUSH3
+	// 11       PACK
+	// 12       STLOC0
+	// 13       PUSHDATA1    0270ddafdf496b82b723cd4a5113b6c6cf1bf9d61854868c85b0c54d83b81429ca
+	// 48       PUSHDATA1    02b81c1c9ace5b76a6d678167572730027ccffb9431cc6720ad02c53cb135d62a0
+	// 83       PUSHDATA1    02d01e5e1a3f1f0f64e82ee04414874a823da09f69964f2cd352f5954f726b97a7
+	// 118      PUSHDATA1    03e60a4ee268eb007fbbf09077325ccdf41068c93a2c77cc95264c7410f6a82575
+	// 153      PUSH4
+	// 154      PACK
+	// 155      STLOC1
+	// 156      SYSCALL      System.Runtime.GetNetwork (c5fba0e0)
+	// 161      PUSHINT64    4294967296 (0000000001000000)
+	// 170      ADD
+	// 171      PUSH4
+	// 172      LEFT
+	// 173      SYSCALL      System.Runtime.GetScriptContainer (2d510830)
+	// 178      PUSH0
+	// 179      PICKITEM
+	// 180      CAT
+	// 181      STLOC2
+	// 182      PUSH0
+	// 183      STLOC3
+	// 184      PUSH0
+	// 185      STLOC4
+	// 186      LDLOC3
+	// 187      PUSH3
+	// 188      GE
+	// 189      LDLOC4
+	// 190      PUSH4
+	// 191      GE
+	// 192      OR
+	// 193      JMPIF        259 (66/42)
+	// 195      PUSHINT8     24 (18)
+	// 197      LDLOC0
+	// 198      LDLOC3
+	// 199      PICKITEM
+	// 200      LDLOC1
+	// 201      LDLOC4
+	// 202      PICKITEM
+	// 203      LDLOC2
+	// 204      PUSH4
+	// 205      PACK
+	// 206      PUSH15
+	// 207      PUSHDATA1    766572696679576974684543447361 ("verifyWithECDsa")
+	// 224      PUSHDATA1    1bf575ab1189688413610a35a12886cde0b66c72 ("NNToUmdQBe5n8o53BTzjTFAnSEcpouyy3B", "0x726cb6e0cd8628a1350a611384688911ab75f51b")
+	// 246      SYSCALL      System.Contract.Call (627d5b52)
+	// 251      LDLOC3
+	// 252      ADD
+	// 253      STLOC3
+	// 254      LDLOC4
+	// 255      INC
+	// 256      STLOC4
+	// 257      JMP          186 (-71/b9)
+	// 259      LDLOC3
+	// 260      PUSH3
+	// 261      NUMEQUAL
+}

pkg/vm/emit/emit.go

@@ -29,6 +29,11 @@ func Opcodes(w *io.BinWriter, ops ...opcode.Opcode) {
 	}
 }
 
+// InitSlot emits INITSLOT instruction with the specified size of locals/args slots.
+func InitSlot(w *io.BinWriter, locals, args uint8) {
+	Instruction(w, opcode.INITSLOT, []byte{locals, args})
+}
+
 // Bool emits a bool type to the given buffer.
 func Bool(w *io.BinWriter, ok bool) {
 	var opVal = opcode.PUSHT