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