From 990992ce94b473dfbf2091d136468f232aa28513 Mon Sep 17 00:00:00 2001 From: "Johan T. Halseth" Date: Fri, 6 Mar 2020 16:11:45 +0100 Subject: [PATCH] input/script_utils: add delayed to_remote script + tests --- input/script_utils.go | 75 +++++++++++++++++++++----- input/script_utils_test.go | 107 +++++++++++++++++++++++++++++++++++++ 2 files changed, 170 insertions(+), 12 deletions(-) diff --git a/input/script_utils.go b/input/script_utils.go index 7342e2e6..8c650c94 100644 --- a/input/script_utils.go +++ b/input/script_utils.go @@ -853,18 +853,6 @@ func CommitScriptToSelf(csvTimeout uint32, selfKey, revokeKey *btcec.PublicKey) return builder.Script() } -// CommitScriptUnencumbered constructs the public key script on the commitment -// transaction paying to the "other" party. The constructed output is a normal -// p2wkh output spendable immediately, requiring no contestation period. -func CommitScriptUnencumbered(key *btcec.PublicKey) ([]byte, error) { - // This script goes to the "other" party, and is spendable immediately. - builder := txscript.NewScriptBuilder() - builder.AddOp(txscript.OP_0) - builder.AddData(btcutil.Hash160(key.SerializeCompressed())) - - return builder.Script() -} - // CommitSpendTimeout constructs a valid witness allowing the owner of a // particular commitment transaction to spend the output returning settled // funds back to themselves after a relative block timeout. In order to @@ -973,6 +961,69 @@ func CommitSpendNoDelay(signer Signer, signDesc *SignDescriptor, return witness, nil } +// CommitScriptUnencumbered constructs the public key script on the commitment +// transaction paying to the "other" party. The constructed output is a normal +// p2wkh output spendable immediately, requiring no contestation period. +func CommitScriptUnencumbered(key *btcec.PublicKey) ([]byte, error) { + // This script goes to the "other" party, and is spendable immediately. + builder := txscript.NewScriptBuilder() + builder.AddOp(txscript.OP_0) + builder.AddData(btcutil.Hash160(key.SerializeCompressed())) + + return builder.Script() +} + +// CommitScriptToRemoteConfirmed constructs the script for the output on the +// commitment transaction paying to the remote party of said commitment +// transaction. The money can only be spend after one confirmation. +// +// Possible Input Scripts: +// SWEEP: +// +// Output Script: +// OP_CHECKSIGVERIFY +// 1 OP_CHECKSEQUENCEVERIFY +func CommitScriptToRemoteConfirmed(key *btcec.PublicKey) ([]byte, error) { + builder := txscript.NewScriptBuilder() + + // Only the given key can spend the output. + builder.AddData(key.SerializeCompressed()) + builder.AddOp(txscript.OP_CHECKSIGVERIFY) + + // Check that the it has one confirmation. + builder.AddOp(txscript.OP_1) + builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY) + + return builder.Script() +} + +// CommitSpendToRemoteConfirmed constructs a valid witness allowing a node to +// spend their settled output on the counterparty's commitment transaction when +// it has one confirmetion. This is used for the anchor channel type. The +// spending key will always be non-tweaked for this output type. +func CommitSpendToRemoteConfirmed(signer Signer, signDesc *SignDescriptor, + sweepTx *wire.MsgTx) (wire.TxWitness, error) { + + if signDesc.KeyDesc.PubKey == nil { + return nil, fmt.Errorf("cannot generate witness with nil " + + "KeyDesc pubkey") + } + + // Similar to non delayed output, only a signature is needed. + sweepSig, err := signer.SignOutputRaw(sweepTx, signDesc) + if err != nil { + return nil, err + } + + // Finally, we'll manually craft the witness. The witness here is the + // signature and the redeem script. + witnessStack := make([][]byte, 2) + witnessStack[0] = append(sweepSig, byte(signDesc.HashType)) + witnessStack[1] = signDesc.WitnessScript + + return witnessStack, nil +} + // SingleTweakBytes computes set of bytes we call the single tweak. The purpose // of the single tweak is to randomize all regular delay and payment base // points. To do this, we generate a hash that binds the commitment point to diff --git a/input/script_utils_test.go b/input/script_utils_test.go index 6f871979..dcec43a1 100644 --- a/input/script_utils_test.go +++ b/input/script_utils_test.go @@ -1144,6 +1144,113 @@ func TestSecondLevelHtlcSpends(t *testing.T) { } } +// TestCommitSpendToRemoteConfirmed checks that the delayed version of the +// to_remote version can only be spent by the owner, and after one +// confirmation. +func TestCommitSpendToRemoteConfirmed(t *testing.T) { + t.Parallel() + + const outputVal = btcutil.Amount(2 * 10e8) + + aliceKeyPriv, aliceKeyPub := btcec.PrivKeyFromBytes(btcec.S256(), + testWalletPrivKey) + + txid, err := chainhash.NewHash(testHdSeed.CloneBytes()) + if err != nil { + t.Fatalf("unable to create txid: %v", err) + } + commitOut := &wire.OutPoint{ + Hash: *txid, + Index: 0, + } + commitScript, err := CommitScriptToRemoteConfirmed(aliceKeyPub) + if err != nil { + t.Fatalf("unable to create htlc script: %v", err) + } + commitPkScript, err := WitnessScriptHash(commitScript) + if err != nil { + t.Fatalf("unable to create htlc output: %v", err) + } + + commitOutput := &wire.TxOut{ + PkScript: commitPkScript, + Value: int64(outputVal), + } + + sweepTx := wire.NewMsgTx(2) + sweepTx.AddTxIn(wire.NewTxIn(commitOut, nil, nil)) + sweepTx.AddTxOut( + &wire.TxOut{ + PkScript: []byte("doesn't matter"), + Value: 1 * 10e8, + }, + ) + + aliceSigner := &MockSigner{Privkeys: []*btcec.PrivateKey{aliceKeyPriv}} + + testCases := []struct { + witness func() wire.TxWitness + valid bool + }{ + { + // Alice can spend after the a CSV delay has passed. + makeWitnessTestCase(t, func() (wire.TxWitness, error) { + sweepTx.TxIn[0].Sequence = LockTimeToSequence(false, 1) + sweepTxSigHashes := txscript.NewTxSigHashes(sweepTx) + + signDesc := &SignDescriptor{ + KeyDesc: keychain.KeyDescriptor{ + PubKey: aliceKeyPub, + }, + WitnessScript: commitScript, + Output: commitOutput, + HashType: txscript.SigHashAll, + SigHashes: sweepTxSigHashes, + InputIndex: 0, + } + + return CommitSpendToRemoteConfirmed(aliceSigner, signDesc, + sweepTx) + }), + true, + }, + { + // Alice cannot spend output without sequence set. + makeWitnessTestCase(t, func() (wire.TxWitness, error) { + sweepTx.TxIn[0].Sequence = wire.MaxTxInSequenceNum + sweepTxSigHashes := txscript.NewTxSigHashes(sweepTx) + + signDesc := &SignDescriptor{ + KeyDesc: keychain.KeyDescriptor{ + PubKey: aliceKeyPub, + }, + WitnessScript: commitScript, + Output: commitOutput, + HashType: txscript.SigHashAll, + SigHashes: sweepTxSigHashes, + InputIndex: 0, + } + + return CommitSpendToRemoteConfirmed(aliceSigner, signDesc, + sweepTx) + }), + false, + }, + } + + for i, testCase := range testCases { + sweepTx.TxIn[0].Witness = testCase.witness() + + newEngine := func() (*txscript.Engine, error) { + return txscript.NewEngine(commitPkScript, + sweepTx, 0, txscript.StandardVerifyFlags, nil, + nil, int64(outputVal)) + } + + assertEngineExecution(t, i, testCase.valid, newEngine) + } +} + // TestSpecificationKeyDerivation implements the test vectors provided in // BOLT-03, Appendix E. func TestSpecificationKeyDerivation(t *testing.T) {