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sign.go
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sign.go
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// Copyright (c) 2013-2015 The btcsuite developers
// Copyright (c) 2015-2016 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package txscript
import (
"errors"
"fmt"
"github.com/hybridnetwork/hxd/chaincfg"
"github.com/hybridnetwork/hxd/chaincfg/chainec"
"github.com/hybridnetwork/hxd/wire"
dcrutil "github.com/hybridnetwork/hxutil"
bs "github.com/hybridnetwork/hxd/crypto/bliss"
)
// RawTxInSignature returns the serialized ECDSA signature for the input idx of
// the given transaction, with hashType appended to it.
func RawTxInSignature(tx *wire.MsgTx, idx int, subScript []byte,
hashType SigHashType, key chainec.PrivateKey) ([]byte, error) {
parsedScript, err := parseScript(subScript)
if err != nil {
return nil, fmt.Errorf("cannot parse output script: %v", err)
}
hash, err := calcSignatureHash(parsedScript, hashType, tx, idx, nil)
if err != nil {
return nil, err
}
r, s, err := chainec.Secp256k1.Sign(key, hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
sig := chainec.Secp256k1.NewSignature(r, s)
return append(sig.Serialize(), byte(hashType)), nil
}
// RawTxInSignatureAlt returns the serialized ECDSA signature for the input idx of
// the given transaction, with hashType appended to it.
func RawTxInSignatureAlt(tx *wire.MsgTx, idx int, subScript []byte,
hashType SigHashType, key chainec.PrivateKey, sigType sigTypes) ([]byte,
error) {
parsedScript, err := parseScript(subScript)
if err != nil {
return nil, fmt.Errorf("cannot parse output script: %v", err)
}
hash, err := calcSignatureHash(parsedScript, hashType, tx, idx, nil)
if err != nil {
return nil, err
}
var sig chainec.Signature
switch sigType {
case edwards:
r, s, err := chainec.Edwards.Sign(key, hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
sig = chainec.Edwards.NewSignature(r, s)
case secSchnorr:
r, s, err := chainec.SecSchnorr.Sign(key, hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
sig = chainec.SecSchnorr.NewSignature(r, s)
case bliss:
sig, err = bs.Bliss.Sign(key.(bs.PrivateKey), hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
default:
return nil, fmt.Errorf("unknown alt sig type %v", sigType)
}
return append(sig.Serialize(), byte(hashType)), nil
}
// SignatureScript creates an input signature script for tx to spend coins sent
// from a previous output to the owner of privKey. tx must include all
// transaction inputs and outputs, however txin scripts are allowed to be filled
// or empty. The returned script is calculated to be used as the idx'th txin
// sigscript for tx. subscript is the PkScript of the previous output being used
// as the idx'th input. privKey is serialized in either a compressed or
// uncompressed format based on compress. This format must match the same format
// used to generate the payment address, or the script validation will fail.
func SignatureScript(tx *wire.MsgTx, idx int, subscript []byte,
hashType SigHashType, privKey chainec.PrivateKey, compress bool) ([]byte,
error) {
sig, err := RawTxInSignature(tx, idx, subscript, hashType, privKey)
if err != nil {
return nil, err
}
pubx, puby := privKey.Public()
pub := chainec.Secp256k1.NewPublicKey(pubx, puby)
var pkData []byte
if compress {
pkData = pub.SerializeCompressed()
} else {
pkData = pub.SerializeUncompressed()
}
return NewScriptBuilder().AddData(sig).AddData(pkData).Script()
}
// SignatureScriptAlt creates an input signature script for tx to spend coins sent
// from a previous output to the owner of privKey. tx must include all
// transaction inputs and outputs, however txin scripts are allowed to be filled
// or empty. The returned script is calculated to be used as the idx'th txin
// sigscript for tx. subscript is the PkScript of the previous output being used
// as the idx'th input. privKey is serialized in the respective format for the
// ECDSA type. This format must match the same format used to generate the payment
// address, or the script validation will fail.
func SignatureScriptAlt(tx *wire.MsgTx, idx int, subscript []byte,
hashType SigHashType, privKey chainec.PrivateKey, compress bool,
sigType int) ([]byte,
error) {
sig, err := RawTxInSignatureAlt(tx, idx, subscript, hashType, privKey,
sigTypes(sigType))
if err != nil {
return nil, err
}
pubx, puby := privKey.Public()
var pub chainec.PublicKey
switch sigTypes(sigType) {
case edwards:
pub = chainec.Edwards.NewPublicKey(pubx, puby)
case secSchnorr:
pub = chainec.SecSchnorr.NewPublicKey(pubx, puby)
case bliss:
pub = privKey.(bs.PrivateKey).PublicKey()
}
pkData := pub.Serialize()
return NewScriptBuilder().AddData(sig).AddData(pkData).Script()
}
// p2pkSignatureScript constructs a pay-to-pubkey signature script.
func p2pkSignatureScript(tx *wire.MsgTx, idx int, subScript []byte,
hashType SigHashType, privKey chainec.PrivateKey) ([]byte, error) {
sig, err := RawTxInSignature(tx, idx, subScript, hashType, privKey)
if err != nil {
return nil, err
}
return NewScriptBuilder().AddData(sig).Script()
}
// p2pkSignatureScript constructs a pay-to-pubkey signature script for alternative
// ECDSA types.
func p2pkSignatureScriptAlt(tx *wire.MsgTx, idx int, subScript []byte,
hashType SigHashType, privKey chainec.PrivateKey, sigType sigTypes) ([]byte,
error) {
sig, err := RawTxInSignatureAlt(tx, idx, subScript, hashType, privKey,
sigType)
if err != nil {
return nil, err
}
return NewScriptBuilder().AddData(sig).Script()
}
// signMultiSig signs as many of the outputs in the provided multisig script as
// possible. It returns the generated script and a boolean if the script fulfils
// the contract (i.e. nrequired signatures are provided). Since it is arguably
// legal to not be able to sign any of the outputs, no error is returned.
func signMultiSig(tx *wire.MsgTx, idx int, subScript []byte, hashType SigHashType,
addresses []dcrutil.Address, nRequired int, kdb KeyDB) ([]byte, bool) {
// No need to add dummy in Decred.
builder := NewScriptBuilder()
signed := 0
for _, addr := range addresses {
key, _, err := kdb.GetKey(addr)
if err != nil {
continue
}
sig, err := RawTxInSignature(tx, idx, subScript, hashType, key)
if err != nil {
continue
}
builder.AddData(sig)
signed++
if signed == nRequired {
break
}
}
script, _ := builder.Script()
return script, signed == nRequired
}
// handleStakeOutSign is a convenience function for reducing code clutter in
// sign. It handles the signing of stake outputs.
func handleStakeOutSign(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
subScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
addresses []dcrutil.Address, class ScriptClass, subClass ScriptClass,
nrequired int) ([]byte, ScriptClass, []dcrutil.Address, int, error) {
// look up key for address
switch subClass {
case PubKeyHashTy:
key, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
txscript, err := SignatureScript(tx, idx, subScript, hashType,
key, compressed)
if err != nil {
return nil, class, nil, 0, err
}
return txscript, class, addresses, nrequired, nil
case ScriptHashTy:
script, err := sdb.GetScript(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
}
return nil, class, nil, 0, fmt.Errorf("unknown subclass for stake output " +
"to sign")
}
// sign is the main signing workhorse. It takes a script, its input transaction,
// its input index, a database of keys, a database of scripts, and information
// about the type of signature and returns a signature, script class, the
// addresses involved, and the number of signatures required.
func sign(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
subScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
sigType sigTypes) ([]byte,
ScriptClass, []dcrutil.Address, int, error) {
class, addresses, nrequired, err := ExtractPkScriptAddrs(DefaultScriptVersion,
subScript, chainParams)
if err != nil {
return nil, NonStandardTy, nil, 0, err
}
subClass := class
isStakeType := class == StakeSubmissionTy ||
class == StakeSubChangeTy ||
class == StakeGenTy ||
class == StakeRevocationTy
if isStakeType {
subClass, err = GetStakeOutSubclass(subScript)
if err != nil {
return nil, 0, nil, 0,
fmt.Errorf("unknown stake output subclass encountered")
}
}
switch class {
case PubKeyTy:
// look up key for address
key, _, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := p2pkSignatureScript(tx, idx, subScript, hashType,
key)
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case PubkeyAltTy:
// look up key for address
key, _, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := p2pkSignatureScriptAlt(tx, idx, subScript, hashType,
key, sigType)
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case PubKeyHashTy:
// look up key for address
key, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := SignatureScript(tx, idx, subScript, hashType,
key, compressed)
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case PubkeyHashAltTy:
// look up key for address
key, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := SignatureScriptAlt(tx, idx, subScript, hashType,
key, compressed, int(sigType))
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case ScriptHashTy:
script, err := sdb.GetScript(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case MultiSigTy:
script, _ := signMultiSig(tx, idx, subScript, hashType,
addresses, nrequired, kdb)
return script, class, addresses, nrequired, nil
case StakeSubmissionTy:
return handleStakeOutSign(chainParams, tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeGenTy:
return handleStakeOutSign(chainParams, tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeRevocationTy:
return handleStakeOutSign(chainParams, tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeSubChangeTy:
return handleStakeOutSign(chainParams, tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case NullDataTy:
return nil, class, nil, 0,
errors.New("can't sign NULLDATA transactions")
default:
return nil, class, nil, 0,
errors.New("can't sign unknown transactions")
}
}
// mergeScripts merges sigScript and prevScript assuming they are both
// partial solutions for pkScript spending output idx of tx. class, addresses
// and nrequired are the result of extracting the addresses from pkscript.
// The return value is the best effort merging of the two scripts. Calling this
// function with addresses, class and nrequired that do not match pkScript is
// an error and results in undefined behaviour.
func mergeScripts(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
pkScript []byte, class ScriptClass, addresses []dcrutil.Address,
nRequired int, sigScript, prevScript []byte) []byte {
// TODO(oga) the scripthash and multisig paths here are overly
// inefficient in that they will recompute already known data.
// some internal refactoring could probably make this avoid needless
// extra calculations.
switch class {
case ScriptHashTy:
// Remove the last push in the script and then recurse.
// this could be a lot less inefficient.
sigPops, err := parseScript(sigScript)
if err != nil || len(sigPops) == 0 {
return prevScript
}
prevPops, err := parseScript(prevScript)
if err != nil || len(prevPops) == 0 {
return sigScript
}
// assume that script in sigPops is the correct one, we just
// made it.
script := sigPops[len(sigPops)-1].data
// We already know this information somewhere up the stack.
class, addresses, nrequired, err :=
ExtractPkScriptAddrs(DefaultScriptVersion, script, chainParams)
// regenerate scripts.
sigScript, _ := unparseScript(sigPops)
prevScript, _ := unparseScript(prevPops)
// Merge
mergedScript := mergeScripts(chainParams, tx, idx, script,
class, addresses, nrequired, sigScript, prevScript)
// Reappend the script and return the result.
builder := NewScriptBuilder()
builder.AddOps(mergedScript)
builder.AddData(script)
finalScript, _ := builder.Script()
return finalScript
case MultiSigTy:
return mergeMultiSig(tx, idx, addresses, nRequired, pkScript,
sigScript, prevScript)
// It doesn't actually make sense to merge anything other than multiig
// and scripthash (because it could contain multisig). Everything else
// has either zero signature, can't be spent, or has a single signature
// which is either present or not. The other two cases are handled
// above. In the conflict case here we just assume the longest is
// correct (this matches behaviour of the reference implementation).
default:
if len(sigScript) > len(prevScript) {
return sigScript
}
return prevScript
}
}
// mergeMultiSig combines the two signature scripts sigScript and prevScript
// that both provide signatures for pkScript in output idx of tx. addresses
// and nRequired should be the results from extracting the addresses from
// pkScript. Since this function is internal only we assume that the arguments
// have come from other functions internally and thus are all consistent with
// each other, behaviour is undefined if this contract is broken.
func mergeMultiSig(tx *wire.MsgTx, idx int, addresses []dcrutil.Address,
nRequired int, pkScript, sigScript, prevScript []byte) []byte {
// This is an internal only function and we already parsed this script
// as ok for multisig (this is how we got here), so if this fails then
// all assumptions are broken and who knows which way is up?
pkPops, _ := parseScript(pkScript)
sigPops, err := parseScript(sigScript)
if err != nil || len(sigPops) == 0 {
return prevScript
}
prevPops, err := parseScript(prevScript)
if err != nil || len(prevPops) == 0 {
return sigScript
}
// Convenience function to avoid duplication.
extractSigs := func(pops []parsedOpcode, sigs [][]byte) [][]byte {
for _, pop := range pops {
if len(pop.data) != 0 {
sigs = append(sigs, pop.data)
}
}
return sigs
}
possibleSigs := make([][]byte, 0, len(sigPops)+len(prevPops))
possibleSigs = extractSigs(sigPops, possibleSigs)
possibleSigs = extractSigs(prevPops, possibleSigs)
// Now we need to match the signatures to pubkeys, the only real way to
// do that is to try to verify them all and match it to the pubkey
// that verifies it. we then can go through the addresses in order
// to build our script. Anything that doesn't parse or doesn't verify we
// throw away.
addrToSig := make(map[string][]byte)
sigLoop:
for _, sig := range possibleSigs {
// can't have a valid signature that doesn't at least have a
// hashtype, in practise it is even longer than this. but
// that'll be checked next.
if len(sig) < 1 {
continue
}
tSig := sig[:len(sig)-1]
hashType := SigHashType(sig[len(sig)-1])
pSig, err := chainec.Secp256k1.ParseDERSignature(tSig)
if err != nil {
continue
}
// We have to do this each round since hash types may vary
// between signatures and so the hash will vary. We can,
// however, assume no sigs etc are in the script since that
// would make the transaction nonstandard and thus not
// MultiSigTy, so we just need to hash the full thing.
hash, err := calcSignatureHash(pkPops, hashType, tx, idx, nil)
if err != nil {
// Decred -- is this the right handling for SIGHASH_SINGLE error ?
// TODO make sure this doesn't break anything.
continue
}
for _, addr := range addresses {
// All multisig addresses should be pubkey addreses
// it is an error to call this internal function with
// bad input.
pkaddr := addr.(*dcrutil.AddressSecpPubKey)
pubKey := pkaddr.PubKey()
// If it matches we put it in the map. We only
// can take one signature per public key so if we
// already have one, we can throw this away.
r := pSig.GetR()
s := pSig.GetS()
if chainec.Secp256k1.Verify(pubKey, hash, r, s) {
aStr := addr.EncodeAddress()
if _, ok := addrToSig[aStr]; !ok {
addrToSig[aStr] = sig
}
continue sigLoop
}
}
}
// Extra opcode to handle the extra arg consumed (due to previous bugs
// in the reference implementation).
builder := NewScriptBuilder() //.AddOp(OP_FALSE)
doneSigs := 0
// This assumes that addresses are in the same order as in the script.
for _, addr := range addresses {
sig, ok := addrToSig[addr.EncodeAddress()]
if !ok {
continue
}
builder.AddData(sig)
doneSigs++
if doneSigs == nRequired {
break
}
}
// padding for missing ones.
for i := doneSigs; i < nRequired; i++ {
builder.AddOp(OP_0)
}
script, _ := builder.Script()
return script
}
// KeyDB is an interface type provided to SignTxOutput, it encapsulates
// any user state required to get the private keys for an address.
type KeyDB interface {
GetKey(dcrutil.Address) (chainec.PrivateKey, bool, error)
}
// KeyClosure implements KeyDB with a closure.
type KeyClosure func(dcrutil.Address) (chainec.PrivateKey, bool, error)
// GetKey implements KeyDB by returning the result of calling the closure.
func (kc KeyClosure) GetKey(address dcrutil.Address) (chainec.PrivateKey,
bool, error) {
return kc(address)
}
// ScriptDB is an interface type provided to SignTxOutput, it encapsulates any
// user state required to get the scripts for an pay-to-script-hash address.
type ScriptDB interface {
GetScript(dcrutil.Address) ([]byte, error)
}
// ScriptClosure implements ScriptDB with a closure.
type ScriptClosure func(dcrutil.Address) ([]byte, error)
// GetScript implements ScriptDB by returning the result of calling the closure.
func (sc ScriptClosure) GetScript(address dcrutil.Address) ([]byte, error) {
return sc(address)
}
// SignTxOutput signs output idx of the given tx to resolve the script given in
// pkScript with a signature type of hashType. Any keys required will be
// looked up by calling getKey() with the string of the given address.
// Any pay-to-script-hash signatures will be similarly looked up by calling
// getScript. If previousScript is provided then the results in previousScript
// will be merged in a type-dependent manner with the newly generated.
// signature script.
func SignTxOutput(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
pkScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
previousScript []byte, sigType int) ([]byte, error) {
sigScript, class, addresses, nrequired, err := sign(chainParams, tx,
idx, pkScript, hashType, kdb, sdb, sigTypes(sigType))
if err != nil {
return nil, err
}
isStakeType := class == StakeSubmissionTy ||
class == StakeSubChangeTy ||
class == StakeGenTy ||
class == StakeRevocationTy
if isStakeType {
class, err = GetStakeOutSubclass(pkScript)
if err != nil {
return nil, fmt.Errorf("unknown stake output subclass encountered")
}
}
if class == ScriptHashTy {
// TODO keep the sub addressed and pass down to merge.
realSigScript, _, _, _, err := sign(chainParams, tx, idx,
sigScript, hashType, kdb, sdb, sigTypes(sigType))
if err != nil {
return nil, err
}
// Append the p2sh script as the last push in the script.
builder := NewScriptBuilder()
builder.AddOps(realSigScript)
builder.AddData(sigScript)
sigScript, _ = builder.Script()
// TODO keep a copy of the script for merging.
}
// Merge scripts. with any previous data, if any.
mergedScript := mergeScripts(chainParams, tx, idx, pkScript, class,
addresses, nrequired, sigScript, previousScript)
return mergedScript, nil
}