dcrd/txscript/sign.go
Dave Collins bcea78f4d7
secp256k1: Make private key independent type.
This modifies the PrivateKey type to be defined as its own struct as
opposed of in terms of an ecdsa.PrivateKey and updates the code and
tests accordingly.  It also removes the PrivKeyFromScalar and
GenerateKey funcs while here since they are effectively duplicates of
existing funcs that were added to satisfy the chainec interface which no
longer exists.

For now, it essentially keeps the same format with the exception of
embedding the ecdsa.PublicKey, but being its own type will alllow for it
to eventually be made opaque and thus provide greater optimizations.

This is continued work towards making the internals of the package
entirely independent of the crypto/elliptic and crypto/ecdsa stdlib
interfaces.
2020-02-10 22:40:34 -06:00

592 lines
19 KiB
Go

// Copyright (c) 2013-2015 The btcsuite developers
// Copyright (c) 2015-2020 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/decred/dcrd/dcrec"
"github.com/decred/dcrd/dcrec/edwards/v2"
"github.com/decred/dcrd/dcrec/secp256k1/v3"
"github.com/decred/dcrd/dcrec/secp256k1/v3/schnorr"
"github.com/decred/dcrd/dcrutil/v3"
"github.com/decred/dcrd/wire"
)
// RawTxInSignature returns the serialized ECDSA signature for the input idx of
// the given transaction, with hashType appended to it.
//
// NOTE: This function is only valid for version 0 scripts. Since the function
// does not accept a script version, the results are undefined for other script
// versions.
func RawTxInSignature(tx *wire.MsgTx, idx int, subScript []byte,
hashType SigHashType, key []byte, sigType dcrec.SignatureType) ([]byte, error) {
hash, err := CalcSignatureHash(subScript, hashType, tx, idx, nil)
if err != nil {
return nil, err
}
var sigBytes []byte
switch sigType {
case dcrec.STEcdsaSecp256k1:
priv := secp256k1.PrivKeyFromBytes(key)
sig := priv.Sign(hash)
sigBytes = sig.Serialize()
case dcrec.STEd25519:
priv, _ := edwards.PrivKeyFromBytes(key)
if priv == nil {
return nil, fmt.Errorf("invalid privkey")
}
sig, err := priv.Sign(hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
sigBytes = sig.Serialize()
case dcrec.STSchnorrSecp256k1:
priv := secp256k1.PrivKeyFromBytes(key)
r, s, err := schnorr.Sign(priv, hash)
if err != nil {
return nil, fmt.Errorf("cannot sign tx input: %s", err)
}
sigBytes = schnorr.NewSignature(r, s).Serialize()
default:
return nil, fmt.Errorf("unknown signature type '%v'", sigType)
}
return append(sigBytes, 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 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 SignatureScript(tx *wire.MsgTx, idx int, subscript []byte, hashType SigHashType,
privKey []byte, sigType dcrec.SignatureType, compress bool) ([]byte, error) {
sig, err := RawTxInSignature(tx, idx, subscript, hashType, privKey, sigType)
if err != nil {
return nil, err
}
var pkData []byte
switch sigType {
case dcrec.STEcdsaSecp256k1:
priv := secp256k1.PrivKeyFromBytes(privKey)
if compress {
pkData = priv.PubKey().SerializeCompressed()
} else {
pkData = priv.PubKey().SerializeUncompressed()
}
case dcrec.STEd25519:
_, pub := edwards.PrivKeyFromBytes(privKey)
pkData = pub.Serialize()
case dcrec.STSchnorrSecp256k1:
priv := secp256k1.PrivKeyFromBytes(privKey)
pkData = priv.PubKey().SerializeCompressed()
default:
return nil, fmt.Errorf("unsupported signature type '%v'", sigType)
}
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 []byte, sigType dcrec.SignatureType) ([]byte, error) {
sig, err := RawTxInSignature(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
// fulfills 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, sigType, _, err := kdb.GetKey(addr)
if err != nil {
continue
}
sig, err := RawTxInSignature(tx, idx, subScript, hashType, key, sigType)
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(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, sigType, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
txscript, err := SignatureScript(tx, idx, subScript, hashType,
key, sigType, 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 dcrutil.AddressParams, tx *wire.MsgTx, idx int,
subScript []byte, hashType SigHashType, kdb KeyDB,
sdb ScriptDB) ([]byte, ScriptClass, []dcrutil.Address, int, error) {
const scriptVersion = 0
class, addresses, nrequired, err := ExtractPkScriptAddrs(scriptVersion,
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, sigType, _, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := p2pkSignatureScript(tx, idx, subScript, hashType,
key, sigType)
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case PubkeyAltTy:
// look up key for address
key, sigType, _, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := p2pkSignatureScript(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, sigType, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := SignatureScript(tx, idx, subScript, hashType,
key, sigType, compressed)
if err != nil {
return nil, class, nil, 0, err
}
return script, class, addresses, nrequired, nil
case PubkeyHashAltTy:
// look up key for address
key, sigType, compressed, err := kdb.GetKey(addresses[0])
if err != nil {
return nil, class, nil, 0, err
}
script, err := SignatureScript(tx, idx, subScript, hashType,
key, sigType, compressed)
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(tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeGenTy:
return handleStakeOutSign(tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeRevocationTy:
return handleStakeOutSign(tx, idx, subScript, hashType, kdb,
sdb, addresses, class, subClass, nrequired)
case StakeSubChangeTy:
return handleStakeOutSign(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")
}
}
// 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.
//
// NOTE: This function is only valid for version 0 scripts. Since the function
// does not accept a script version, the results are undefined for other script
// versions.
func mergeMultiSig(tx *wire.MsgTx, idx int, addresses []dcrutil.Address,
nRequired int, pkScript, sigScript, prevScript []byte) []byte {
// Nothing to merge if either the new or previous signature scripts are
// empty.
if len(sigScript) == 0 {
return prevScript
}
if len(prevScript) == 0 {
return sigScript
}
// Convenience function to avoid duplication.
var possibleSigs [][]byte
extractSigs := func(script []byte) error {
const scriptVersion = 0
tokenizer := MakeScriptTokenizer(scriptVersion, script)
for tokenizer.Next() {
if data := tokenizer.Data(); len(data) != 0 {
possibleSigs = append(possibleSigs, data)
}
}
return tokenizer.Err()
}
// Attempt to extract signatures from the two scripts. Return the other
// script that is intended to be merged in the case signature extraction
// fails for some reason.
if err := extractSigs(sigScript); err != nil {
return prevScript
}
if err := extractSigs(prevScript); err != nil {
return sigScript
}
// 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 := 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(pkScript, 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 addresses
// 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.R
s := pSig.S
if secp256k1.NewSignature(r, s).Verify(hash, pubKey) {
aStr := addr.Address()
if _, ok := addrToSig[aStr]; !ok {
addrToSig[aStr] = sig
}
continue sigLoop
}
}
}
builder := NewScriptBuilder()
doneSigs := 0
// This assumes that addresses are in the same order as in the script.
for _, addr := range addresses {
sig, ok := addrToSig[addr.Address()]
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
}
// 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.
//
// NOTE: This function is only valid for version 0 scripts. Since the function
// does not accept a script version, the results are undefined for other script
// versions.
func mergeScripts(chainParams dcrutil.AddressParams, 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.
const scriptVersion = 0
switch class {
case ScriptHashTy:
// Nothing to merge if either the new or previous signature
// scripts are empty or fail to parse.
if len(sigScript) == 0 ||
checkScriptParses(scriptVersion, sigScript) != nil {
return prevScript
}
if len(prevScript) == 0 ||
checkScriptParses(scriptVersion, prevScript) != nil {
return sigScript
}
// Remove the last push in the script and then recurse.
// this could be a lot less inefficient.
//
// Assume that final script is the correct one since it was just
// made and it is a pay-to-script-hash.
script := finalOpcodeData(scriptVersion, sigScript)
// We already know this information somewhere up the stack,
// therefore the error is ignored.
class, addresses, nrequired, _ := ExtractPkScriptAddrs(scriptVersion,
script, chainParams)
// 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 multisig
// 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
}
}
// 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) ([]byte, dcrec.SignatureType, bool, error)
}
// KeyClosure implements KeyDB with a closure.
type KeyClosure func(dcrutil.Address) ([]byte, dcrec.SignatureType, bool, error)
// GetKey implements KeyDB by returning the result of calling the closure.
func (kc KeyClosure) GetKey(address dcrutil.Address) ([]byte, dcrec.SignatureType, bool, error) {
return kc(address)
}
// ScriptDB is an interface type provided to SignTxOutput, it encapsulates any
// user state required to get the scripts for a 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.
//
// NOTE: This function is only valid for version 0 scripts. Since the function
// does not accept a script version, the results are undefined for other script
// versions.
func SignTxOutput(chainParams dcrutil.AddressParams, tx *wire.MsgTx, idx int,
pkScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
previousScript []byte) ([]byte, error) {
sigScript, class, addresses, nrequired, err := sign(chainParams, tx,
idx, pkScript, hashType, kdb, sdb)
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)
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
}