lbcd/txscript/pkscript.go

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package txscript
import (
"crypto/sha256"
"errors"
"fmt"
"github.com/lbryio/lbcd/btcec"
"github.com/lbryio/lbcd/chaincfg"
"github.com/lbryio/lbcd/wire"
btcutil "github.com/lbryio/lbcutil"
"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
}
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// 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) {
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switch {
case len(sigScript) > 0:
return computeNonWitnessPkScript(sigScript)
case len(witness) > 0:
return computeWitnessPkScript(witness)
default:
return PkScript{}, ErrUnsupportedScriptType
}
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}
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// 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):
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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 {
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return PkScript{}, err
}
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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 {
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return PkScript{}, err
}
redeemScript := finalOpcodeData(scriptVersion, sigScript)
scriptHash := hash160(redeemScript)
script, err := payToScriptHashScript(scriptHash)
if err != nil {
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return PkScript{}, err
}
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pkScript := PkScript{class: ScriptHashTy}
copy(pkScript.script[:], script)
return pkScript, nil
}
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}
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// 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]
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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)
}
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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)
}