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btcstaking: generalise witness generation for covenant committee (#134)
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Co-authored-by: KonradStaniec <konrad.staniec@gmail.com>
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@SebastianElvis @KonradStaniec
SebastianElvis and KonradStaniec authored Dec 4, 2023
1 parent 8ad0481 commit eb50730
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Showing 24 changed files with 874 additions and 751 deletions.
159 changes: 77 additions & 82 deletions btcstaking/btcstaking_test.go
View file
Original file line number Diff line number Diff line change
@@ -1,13 +1,16 @@
package btcstaking_test

import (
"bytes"
"math/rand"
"sort"
"testing"
"time"

"github.com/babylonchain/babylon/btcstaking"
btctest "github.com/babylonchain/babylon/testutil/bitcoin"
"github.com/btcsuite/btcd/btcec/v2"
"github.com/btcsuite/btcd/btcec/v2/schnorr"
"github.com/btcsuite/btcd/btcutil"
"github.com/btcsuite/btcd/chaincfg"
"github.com/btcsuite/btcd/txscript"
Expand Down Expand Up @@ -132,8 +135,7 @@ func TestSpendingTimeLockPath(t *testing.T) {

require.NoError(t, err)

witness, err := si.CreateWitness([][]byte{sig.Serialize()})

witness, err := si.CreateTimeLockPathWitness(sig)
require.NoError(t, err)

spendStakeTx.TxIn[0].Witness = witness
Expand All @@ -151,16 +153,45 @@ func TestSpendingTimeLockPath(t *testing.T) {
btctest.AssertEngineExecution(t, 0, true, newEngine)
}

type SignatureInfo struct {
SignerPubKey *btcec.PublicKey
Signature *schnorr.Signature
}

func NewSignatureInfo(
signerPubKey *btcec.PublicKey,
signature *schnorr.Signature,
) *SignatureInfo {
return &SignatureInfo{
SignerPubKey: signerPubKey,
Signature: signature,
}
}

// Helper function to sort all signatures in reverse lexicographical order of signing public keys
// this way signatures are ready to be used in multisig witness with corresponding public keys
func sortSignatureInfo(infos []*SignatureInfo) []*SignatureInfo {
sortedInfos := make([]*SignatureInfo, len(infos))
copy(sortedInfos, infos)
sort.SliceStable(sortedInfos, func(i, j int) bool {
keyIBytes := schnorr.SerializePubKey(sortedInfos[i].SignerPubKey)
keyJBytes := schnorr.SerializePubKey(sortedInfos[j].SignerPubKey)
return bytes.Compare(keyIBytes, keyJBytes) == 1
})

return sortedInfos
}

// generate list of signatures in valid order
func GenerateSignatures(
t *testing.T,
keys []*btcec.PrivateKey,
tx *wire.MsgTx,
stakingOutput *wire.TxOut,
leaf txscript.TapLeaf,
) [][]byte {
) []*schnorr.Signature {

var si []*btcstaking.SignatureInfo
var si []*SignatureInfo

for _, key := range keys {
pubKey := key.PubKey()
Expand All @@ -171,17 +202,17 @@ func GenerateSignatures(
leaf,
)
require.NoError(t, err)
info := btcstaking.NewSignatureInfo(
info := NewSignatureInfo(
pubKey,
sig.Serialize(),
sig,
)
si = append(si, info)
}

// sort signatures by public key
sortedSigInfo := btcstaking.SortSignatureInfo(si)
sortedSigInfo := sortSignatureInfo(si)

var sigs [][]byte = make([][]byte, len(sortedSigInfo))
var sigs []*schnorr.Signature = make([]*schnorr.Signature, len(sortedSigInfo))

for i, sigInfo := range sortedSigInfo {
sig := sigInfo
Expand Down Expand Up @@ -247,10 +278,7 @@ func TestSpendingUnbondingPathCovenant35MultiSig(t *testing.T) {
stakingInfo.StakingOutput,
si.RevealedLeaf,
)
var witnessSignatures [][]byte
witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err := si.CreateWitness(witnessSignatures)
witness, err := si.CreateUnbondingPathWitness(covenantSigantures, stakerSig)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

Expand All @@ -269,9 +297,6 @@ func TestSpendingUnbondingPathCovenant35MultiSig(t *testing.T) {
numOfCovenantMembers := len(scenario.CovenantKeys)
// with each loop iteration we remove one key from the list of signatures
for i := 0; i < numOfCovenantMembers; i++ {
// reset signatures
witnessSignatures = [][]byte{}

numOfRemovedSignatures := i + 1

covenantSigantures := GenerateSignatures(
Expand All @@ -285,12 +310,10 @@ func TestSpendingUnbondingPathCovenant35MultiSig(t *testing.T) {
for j := 0; j <= i; j++ {
// NOTE: Number provides signatures must match number of public keys in the script,
// if we are missing some signatures those must be set to empty signature in witness
covenantSigantures[j] = []byte{}
covenantSigantures[j] = nil
}

witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err := si.CreateWitness(witnessSignatures)
witness, err := si.CreateUnbondingPathWitness(covenantSigantures, stakerSig)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

Expand Down Expand Up @@ -359,10 +382,7 @@ func TestSpendingUnbondingPathSingleKeyCovenant(t *testing.T) {
stakingInfo.StakingOutput,
si.RevealedLeaf,
)
var witnessSignatures [][]byte
witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err := si.CreateWitness(witnessSignatures)
witness, err := si.CreateUnbondingPathWitness(covenantSigantures, stakerSig)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

Expand Down Expand Up @@ -418,43 +438,21 @@ func TestSpendingSlashingPathCovenant35MultiSig(t *testing.T) {
si, err := stakingInfo.SlashingPathSpendInfo()
require.NoError(t, err)

// generate staker signature, covenant signatures, and validator signature
stakerSig, err := btcstaking.SignTxWithOneScriptSpendInputFromTapLeaf(
spendStakeTx,
stakingInfo.StakingOutput,
scenario.StakerKey,
si.RevealedLeaf,
)
require.NoError(t, err)

// Case without validator signature
covenantSigantures := GenerateSignatures(
t,
scenario.CovenantKeys,
spendStakeTx,
stakingInfo.StakingOutput,
si.RevealedLeaf,
)
var witnessSignatures [][]byte
witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err := si.CreateWitness(witnessSignatures)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

prevOutputFetcher := stakingInfo.GetOutputFetcher()
newEngine := func() (*txscript.Engine, error) {
return txscript.NewEngine(
stakingInfo.GetPkScript(),
spendStakeTx, 0, txscript.StandardVerifyFlags, nil,
txscript.NewTxSigHashes(spendStakeTx, prevOutputFetcher), stakingInfo.StakingOutput.Value,
prevOutputFetcher,
)
}
// we expect it will fail because we are missing validator signature
btctest.AssertEngineExecution(t, 0, false, newEngine)

// Retry with the same values but now with validator signature present
witnessSignatures = [][]byte{}
validatorSig, err := btcstaking.SignTxWithOneScriptSpendInputFromTapLeaf(
spendStakeTx,
stakingInfo.StakingOutput,
Expand All @@ -463,21 +461,31 @@ func TestSpendingSlashingPathCovenant35MultiSig(t *testing.T) {
)
require.NoError(t, err)

witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, validatorSig.Serialize())
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err = si.CreateWitness(witnessSignatures)
witness, err := si.CreateSlashingPathWitness(
covenantSigantures,
[]*schnorr.Signature{validatorSig},
stakerSig,
)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

// now as we have validator signature execution should succeed
prevOutputFetcher := stakingInfo.GetOutputFetcher()
newEngine := func() (*txscript.Engine, error) {
return txscript.NewEngine(
stakingInfo.GetPkScript(),
spendStakeTx, 0, txscript.StandardVerifyFlags, nil,
txscript.NewTxSigHashes(spendStakeTx, prevOutputFetcher), stakingInfo.StakingOutput.Value,
prevOutputFetcher,
)
}
btctest.AssertEngineExecution(t, 0, true, newEngine)
}

func TestSpendingSlashingPathCovenant35MultiSigValidatorRestaking(t *testing.T) {
r := rand.New(rand.NewSource(time.Now().Unix()))

// we are having here 3/5 covenant threshold sig, and we are restaking to 2 validators
// we have 3 out of 5 covenant committee, and we are restaking to 2 validators
scenario := GenerateTestScenario(
r,
t,
Expand Down Expand Up @@ -513,6 +521,7 @@ func TestSpendingSlashingPathCovenant35MultiSigValidatorRestaking(t *testing.T)
si, err := stakingInfo.SlashingPathSpendInfo()
require.NoError(t, err)

// generate staker signature, covenant signatures, and validator signature
stakerSig, err := btcstaking.SignTxWithOneScriptSpendInputFromTapLeaf(
spendStakeTx,
stakingInfo.StakingOutput,
Expand All @@ -521,55 +530,41 @@ func TestSpendingSlashingPathCovenant35MultiSigValidatorRestaking(t *testing.T)
)
require.NoError(t, err)

// Case without validator signature
// only use 3 out of 5 covenant signatures
covenantSigantures := GenerateSignatures(
t,
scenario.CovenantKeys,
spendStakeTx,
stakingInfo.StakingOutput,
si.RevealedLeaf,
)
var witnessSignatures [][]byte
witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err := si.CreateWitness(witnessSignatures)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

prevOutputFetcher := stakingInfo.GetOutputFetcher()
newEngine := func() (*txscript.Engine, error) {
return txscript.NewEngine(
stakingInfo.GetPkScript(),
spendStakeTx, 0, txscript.StandardVerifyFlags, nil,
txscript.NewTxSigHashes(spendStakeTx, prevOutputFetcher), stakingInfo.StakingOutput.Value,
prevOutputFetcher,
)
}
// we expect it will fail because we are missing validators signature
btctest.AssertEngineExecution(t, 0, false, newEngine)

// Retry with the same values but now with validator signature present
witnessSignatures = [][]byte{}
covenantSigantures[0] = nil
covenantSigantures[1] = nil

// only use one of the validator signatures
// script should still be valid as we require only one validator signature
// to be present
validatorsSignatures := GenerateSignatures(
t,
scenario.ValidatorKeys,
spendStakeTx,
stakingInfo.StakingOutput,
si.RevealedLeaf,
)
validatorsSignatures[0] = nil

// make one signature empty, script still should be valid as we require only one validator signature
// to be present
validatorsSignatures[0] = []byte{}

witnessSignatures = append(witnessSignatures, covenantSigantures...)
witnessSignatures = append(witnessSignatures, validatorsSignatures...)
witnessSignatures = append(witnessSignatures, stakerSig.Serialize())
witness, err = si.CreateWitness(witnessSignatures)
witness, err := si.CreateSlashingPathWitness(covenantSigantures, validatorsSignatures, stakerSig)
require.NoError(t, err)
spendStakeTx.TxIn[0].Witness = witness

// now as we have validator signature execution should succeed
prevOutputFetcher := stakingInfo.GetOutputFetcher()
newEngine := func() (*txscript.Engine, error) {
return txscript.NewEngine(
stakingInfo.GetPkScript(),
spendStakeTx, 0, txscript.StandardVerifyFlags, nil,
txscript.NewTxSigHashes(spendStakeTx, prevOutputFetcher), stakingInfo.StakingOutput.Value,
prevOutputFetcher,
)
}
btctest.AssertEngineExecution(t, 0, true, newEngine)
}
40 changes: 0 additions & 40 deletions btcstaking/staking.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -693,43 +693,3 @@ func EncVerifyTransactionSigWithOutputData(

return signature.EncVerify(pubKey, encKey, sigHash)
}

// CreateWitness creates witness for spending the tx corresponding to
// the spend info with the given stack of signatures
// The returned witness stack follows the structure below:
// - first come signatures
// - then whole revealed script
// - then control block
func (si *SpendInfo) CreateWitness(signatures [][]byte) (wire.TxWitness, error) {
numSignatures := len(signatures)

if numSignatures == 0 {
return nil, fmt.Errorf("cannot build witness without signatures")
}

if si == nil {
return nil, fmt.Errorf("cannot build witness without spend info")
}

controlBlockBytes, err := si.ControlBlock.ToBytes()

if err != nil {
return nil, err
}

// witness stack has:
// all signatures
// whole revealed script
// control block
witnessStack := wire.TxWitness(make([][]byte, numSignatures+2))

for i, sig := range signatures {
sc := sig
witnessStack[i] = sc
}

witnessStack[numSignatures] = si.GetPkScriptPath()
witnessStack[numSignatures+1] = controlBlockBytes

return witnessStack, nil
}
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