package txscript import ( "crypto/sha256" "errors" "fmt" "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/chaincfg" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "golang.org/x/crypto/ripemd160" ) const ( // minPubKeyHashSigScriptLen is the minimum length of a signature script // that spends a P2PKH output. The length is composed of the following: // Signature length (1 byte) // Signature (min 8 bytes) // Signature hash type (1 byte) // Public key length (1 byte) // Public key (33 byte) minPubKeyHashSigScriptLen = 1 + btcec.MinSigLen + 1 + 1 + 33 // maxPubKeyHashSigScriptLen is the maximum length of a signature script // that spends a P2PKH output. The length is composed of the following: // Signature length (1 byte) // Signature (max 72 bytes) // Signature hash type (1 byte) // Public key length (1 byte) // Public key (33 byte) maxPubKeyHashSigScriptLen = 1 + 72 + 1 + 1 + 33 // compressedPubKeyLen is the length in bytes of a compressed public // key. compressedPubKeyLen = 33 // pubKeyHashLen is the length of a P2PKH script. pubKeyHashLen = 25 // witnessV0PubKeyHashLen is the length of a P2WPKH script. witnessV0PubKeyHashLen = 22 // scriptHashLen is the length of a P2SH script. scriptHashLen = 23 // witnessV0ScriptHashLen is the length of a P2WSH script. witnessV0ScriptHashLen = 34 // maxLen is the maximum script length supported by ParsePkScript. maxLen = witnessV0ScriptHashLen ) var ( // ErrUnsupportedScriptType is an error returned when we attempt to // parse/re-compute an output script into a PkScript struct. ErrUnsupportedScriptType = errors.New("unsupported script type") ) // PkScript is a wrapper struct around a byte array, allowing it to be used // as a map index. type PkScript struct { // class is the type of the script encoded within the byte array. This // is used to determine the correct length of the script within the byte // array. class ScriptClass // script is the script contained within a byte array. If the script is // smaller than the length of the byte array, it will be padded with 0s // at the end. script [maxLen]byte } // ParsePkScript parses an output script into the PkScript struct. // ErrUnsupportedScriptType is returned when attempting to parse an unsupported // script type. func ParsePkScript(pkScript []byte) (PkScript, error) { var outputScript PkScript scriptClass, _, _, err := ExtractPkScriptAddrs( pkScript, &chaincfg.MainNetParams, ) if err != nil { return outputScript, fmt.Errorf("unable to parse script type: "+ "%v", err) } if !isSupportedScriptType(scriptClass) { return outputScript, ErrUnsupportedScriptType } outputScript.class = scriptClass copy(outputScript.script[:], pkScript) return outputScript, nil } // isSupportedScriptType determines whether the script type is supported by the // PkScript struct. func isSupportedScriptType(class ScriptClass) bool { switch class { case PubKeyHashTy, WitnessV0PubKeyHashTy, ScriptHashTy, WitnessV0ScriptHashTy: return true default: return false } } // Class returns the script type. func (s PkScript) Class() ScriptClass { return s.class } // Script returns the script as a byte slice without any padding. func (s PkScript) Script() []byte { var script []byte switch s.class { case PubKeyHashTy: script = make([]byte, pubKeyHashLen) copy(script, s.script[:pubKeyHashLen]) case WitnessV0PubKeyHashTy: script = make([]byte, witnessV0PubKeyHashLen) copy(script, s.script[:witnessV0PubKeyHashLen]) case ScriptHashTy: script = make([]byte, scriptHashLen) copy(script, s.script[:scriptHashLen]) case WitnessV0ScriptHashTy: script = make([]byte, witnessV0ScriptHashLen) copy(script, s.script[:witnessV0ScriptHashLen]) default: // Unsupported script type. return nil } return script } // Address encodes the script into an address for the given chain. func (s PkScript) Address(chainParams *chaincfg.Params) (btcutil.Address, error) { _, addrs, _, err := ExtractPkScriptAddrs(s.Script(), chainParams) if err != nil { return nil, fmt.Errorf("unable to parse address: %v", err) } return addrs[0], nil } // String returns a hex-encoded string representation of the script. func (s PkScript) String() string { str, _ := DisasmString(s.Script()) return str } // ComputePkScript computes the script of an output by looking at the spending // input's signature script or witness. // // NOTE: Only P2PKH, P2SH, P2WSH, and P2WPKH redeem scripts are supported. func ComputePkScript(sigScript []byte, witness wire.TxWitness) (PkScript, error) { switch { case len(sigScript) > 0: return computeNonWitnessPkScript(sigScript) case len(witness) > 0: return computeWitnessPkScript(witness) default: return PkScript{}, ErrUnsupportedScriptType } } // computeNonWitnessPkScript computes the script of an output by looking at the // spending input's signature script. func computeNonWitnessPkScript(sigScript []byte) (PkScript, error) { switch { // Since we only support P2PKH and P2SH scripts as the only non-witness // script types, we should expect to see a push only script. case !IsPushOnlyScript(sigScript): return PkScript{}, ErrUnsupportedScriptType // If a signature script is provided with a length long enough to // represent a P2PKH script, then we'll attempt to parse the compressed // public key from it. case len(sigScript) >= minPubKeyHashSigScriptLen && len(sigScript) <= maxPubKeyHashSigScriptLen: // The public key should be found as the last part of the // signature script. We'll attempt to parse it to ensure this is // a P2PKH redeem script. pubKey := sigScript[len(sigScript)-compressedPubKeyLen:] if btcec.IsCompressedPubKey(pubKey) { pubKeyHash := hash160(pubKey) script, err := payToPubKeyHashScript(pubKeyHash) if err != nil { return PkScript{}, err } pkScript := PkScript{class: PubKeyHashTy} copy(pkScript.script[:], script) return pkScript, nil } fallthrough // If we failed to parse a compressed public key from the script in the // case above, or if the script length is not that of a P2PKH one, we // can assume it's a P2SH signature script. default: // The redeem script will always be the last data push of the // signature script, so we'll parse the script into opcodes to // obtain it. const scriptVersion = 0 err := checkScriptParses(scriptVersion, sigScript) if err != nil { return PkScript{}, err } redeemScript := finalOpcodeData(scriptVersion, sigScript) scriptHash := hash160(redeemScript) script, err := payToScriptHashScript(scriptHash) if err != nil { return PkScript{}, err } pkScript := PkScript{class: ScriptHashTy} copy(pkScript.script[:], script) return pkScript, nil } } // computeWitnessPkScript computes the script of an output by looking at the // spending input's witness. func computeWitnessPkScript(witness wire.TxWitness) (PkScript, error) { // We'll use the last item of the witness stack to determine the proper // witness type. lastWitnessItem := witness[len(witness)-1] var pkScript PkScript switch { // If the witness stack has a size of 2 and its last item is a // compressed public key, then this is a P2WPKH witness. case len(witness) == 2 && len(lastWitnessItem) == compressedPubKeyLen: pubKeyHash := hash160(lastWitnessItem) script, err := payToWitnessPubKeyHashScript(pubKeyHash) if err != nil { return pkScript, err } pkScript.class = WitnessV0PubKeyHashTy copy(pkScript.script[:], script) // For any other witnesses, we'll assume it's a P2WSH witness. default: scriptHash := sha256.Sum256(lastWitnessItem) script, err := payToWitnessScriptHashScript(scriptHash[:]) if err != nil { return pkScript, err } pkScript.class = WitnessV0ScriptHashTy copy(pkScript.script[:], script) } return pkScript, nil } // hash160 returns the RIPEMD160 hash of the SHA-256 HASH of the given data. func hash160(data []byte) []byte { h := sha256.Sum256(data) return ripemd160h(h[:]) } // ripemd160h returns the RIPEMD160 hash of the given data. func ripemd160h(data []byte) []byte { h := ripemd160.New() h.Write(data) return h.Sum(nil) }