package sweep import ( "github.com/btcsuite/btcd/txscript" "github.com/btcsuite/btcd/wire" "github.com/lightningnetwork/lnd/lnwallet" ) // Input contains all data needed to construct a sweep tx input. type Input interface { // Outpoint returns the reference to the output being spent, used to // construct the corresponding transaction input. OutPoint() *wire.OutPoint // WitnessType returns an enum specifying the type of witness that must // be generated in order to spend this output. WitnessType() lnwallet.WitnessType // SignDesc returns a reference to a spendable output's sign // descriptor, which is used during signing to compute a valid witness // that spends this output. SignDesc() *lnwallet.SignDescriptor // BuildWitness returns a valid witness allowing this output to be // spent, the witness should be attached to the transaction at the // location determined by the given `txinIdx`. BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) // BlocksToMaturity returns the relative timelock, as a number of // blocks, that must be built on top of the confirmation height before // the output can be spent. For non-CSV locked inputs this is always // zero. BlocksToMaturity() uint32 } type inputKit struct { outpoint wire.OutPoint witnessType lnwallet.WitnessType signDesc lnwallet.SignDescriptor } // OutPoint returns the breached output's identifier that is to be included as // a transaction input. func (i *inputKit) OutPoint() *wire.OutPoint { return &i.outpoint } // WitnessType returns the type of witness that must be generated to spend the // breached output. func (i *inputKit) WitnessType() lnwallet.WitnessType { return i.witnessType } // SignDesc returns the breached output's SignDescriptor, which is used during // signing to compute the witness. func (i *inputKit) SignDesc() *lnwallet.SignDescriptor { return &i.signDesc } // BaseInput contains all the information needed to sweep a basic output // (CSV/CLTV/no time lock) type BaseInput struct { inputKit } // MakeBaseInput assembles a new BaseInput that can be used to construct a // sweep transaction. func MakeBaseInput(outpoint *wire.OutPoint, witnessType lnwallet.WitnessType, signDescriptor *lnwallet.SignDescriptor) BaseInput { return BaseInput{ inputKit{ outpoint: *outpoint, witnessType: witnessType, signDesc: *signDescriptor, }, } } // BuildWitness computes a valid witness that allows us to spend from the // breached output. It does so by generating the witness generation function, // which is parameterized primarily by the witness type and sign descriptor. // The method then returns the witness computed by invoking this function. func (bi *BaseInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) { witnessFunc := bi.witnessType.GenWitnessFunc( signer, bi.SignDesc(), ) return witnessFunc(txn, hashCache, txinIdx) } // BlocksToMaturity returns the relative timelock, as a number of blocks, that // must be built on top of the confirmation height before the output can be // spent. For non-CSV locked inputs this is always zero. func (bi *BaseInput) BlocksToMaturity() uint32 { return 0 } // HtlcSucceedInput constitutes a sweep input that needs a pre-image. The input // is expected to reside on the commitment tx of the remote party and should // not be a second level tx output. type HtlcSucceedInput struct { inputKit preimage []byte } // MakeHtlcSucceedInput assembles a new redeem input that can be used to // construct a sweep transaction. func MakeHtlcSucceedInput(outpoint *wire.OutPoint, signDescriptor *lnwallet.SignDescriptor, preimage []byte) HtlcSucceedInput { return HtlcSucceedInput{ inputKit: inputKit{ outpoint: *outpoint, witnessType: lnwallet.HtlcAcceptedRemoteSuccess, signDesc: *signDescriptor, }, preimage: preimage, } } // BuildWitness computes a valid witness that allows us to spend from the // breached output. For HtlcSpendInput it will need to make the preimage part // of the witness. func (h *HtlcSucceedInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) { desc := h.signDesc desc.SigHashes = hashCache desc.InputIndex = txinIdx return lnwallet.SenderHtlcSpendRedeem( signer, &desc, txn, h.preimage, ) } // BlocksToMaturity returns the relative timelock, as a number of blocks, that // must be built on top of the confirmation height before the output can be // spent. func (h *HtlcSucceedInput) BlocksToMaturity() uint32 { return 0 } // Compile-time constraints to ensure each input struct implement the Input // interface. var _ Input = (*BaseInput)(nil) var _ Input = (*HtlcSucceedInput)(nil)