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elements/src/script/sign.cpp
Andrew Poelstra 5b9f316537 Merge dcf2ccbfde into merged_master (Bitcoin PR #18115) 
I really like this PR, but it wound up being pretty nontrivial to merge.
The crux is that it pulls PSBT signing logic into scriptpubkey manager,
which is where it belongs, but for us this means reasoning about pegins
inside script/sign.cpp.

However, sign.cpp is part of libbitcoin_common, which does not include
anything for reasoning about PoW or RPC (lol) or anything heavy about
that. This means that some pegin validation had to remain split between
the wallet/rpc layer and sign.cpp. I added a new file script/pegins.cpp
which has the (one) method we actually need in sign.cpp.

Aside from that, this diff is very large but is mostly just moving our
code changes to wallet/psbtwallet.* into wallet/wallet.* where those
functions now live. As far as review, it's probably not worthwhile to
spend too much too much time on this since it's going to be change
again in #16528 and others. The test coverage is pretty extensive.
2020-11-26 01:07:51 +00:00

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <script/sign.h>
#include <key.h>
#include <pegins.h>
#include <policy/policy.h>
#include <primitives/transaction.h>
#include <script/pegins.h> // for GetPeginOutputFromWitness()
#include <script/signingprovider.h>
#include <script/standard.h>
#include <uint256.h>
#include <chainparams.h>
typedef std::vector<unsigned char> valtype;
MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CConfidentialValue& amountIn, int nHashTypeIn) : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn) {}
bool MutableTransactionSignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode, SigVersion sigversion) const
{
CKey key;
if (!provider.GetKey(address, key))
return false;
// Signing with uncompressed keys is disabled in witness scripts
if (sigversion == SigVersion::WITNESS_V0 && !key.IsCompressed())
return false;
uint256 hash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion);
if (!key.Sign(hash, vchSig))
return false;
vchSig.push_back((unsigned char)nHashType);
return true;
}
static bool GetCScript(const SigningProvider& provider, const SignatureData& sigdata, const CScriptID& scriptid, CScript& script)
{
if (provider.GetCScript(scriptid, script)) {
return true;
}
// Look for scripts in SignatureData
if (CScriptID(sigdata.redeem_script) == scriptid) {
script = sigdata.redeem_script;
return true;
} else if (CScriptID(sigdata.witness_script) == scriptid) {
script = sigdata.witness_script;
return true;
}
return false;
}
static bool GetPubKey(const SigningProvider& provider, const SignatureData& sigdata, const CKeyID& address, CPubKey& pubkey)
{
// Look for pubkey in all partial sigs
const auto it = sigdata.signatures.find(address);
if (it != sigdata.signatures.end()) {
pubkey = it->second.first;
return true;
}
// Look for pubkey in pubkey list
const auto& pk_it = sigdata.misc_pubkeys.find(address);
if (pk_it != sigdata.misc_pubkeys.end()) {
pubkey = pk_it->second.first;
return true;
}
// Query the underlying provider
return provider.GetPubKey(address, pubkey);
}
static bool CreateSig(const BaseSignatureCreator& creator, SignatureData& sigdata, const SigningProvider& provider, std::vector<unsigned char>& sig_out, const CPubKey& pubkey, const CScript& scriptcode, SigVersion sigversion)
{
CKeyID keyid = pubkey.GetID();
const auto it = sigdata.signatures.find(keyid);
if (it != sigdata.signatures.end()) {
sig_out = it->second.second;
return true;
}
KeyOriginInfo info;
if (provider.GetKeyOrigin(keyid, info)) {
sigdata.misc_pubkeys.emplace(keyid, std::make_pair(pubkey, std::move(info)));
}
if (creator.CreateSig(provider, sig_out, keyid, scriptcode, sigversion)) {
auto i = sigdata.signatures.emplace(keyid, SigPair(pubkey, sig_out));
assert(i.second);
return true;
}
// Could not make signature or signature not found, add keyid to missing
sigdata.missing_sigs.push_back(keyid);
return false;
}
/**
* Sign scriptPubKey using signature made with creator.
* Signatures are returned in scriptSigRet (or returns false if scriptPubKey can't be signed),
* unless whichTypeRet is TX_SCRIPTHASH, in which case scriptSigRet is the redemption script.
* Returns false if scriptPubKey could not be completely satisfied.
*/
static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& scriptPubKey,
std::vector<valtype>& ret, txnouttype& whichTypeRet, SigVersion sigversion, SignatureData& sigdata)
{
CScript scriptRet;
uint160 h160;
ret.clear();
std::vector<unsigned char> sig;
std::vector<valtype> vSolutions;
whichTypeRet = Solver(scriptPubKey, vSolutions);
switch (whichTypeRet)
{
case TX_NONSTANDARD:
case TX_NULL_DATA:
case TX_WITNESS_UNKNOWN:
return false;
case TX_PUBKEY:
if (!CreateSig(creator, sigdata, provider, sig, CPubKey(vSolutions[0]), scriptPubKey, sigversion)) return false;
ret.push_back(std::move(sig));
return true;
case TX_PUBKEYHASH: {
CKeyID keyID = CKeyID(uint160(vSolutions[0]));
CPubKey pubkey;
if (!GetPubKey(provider, sigdata, keyID, pubkey)) {
// Pubkey could not be found, add to missing
sigdata.missing_pubkeys.push_back(keyID);
return false;
}
if (!CreateSig(creator, sigdata, provider, sig, pubkey, scriptPubKey, sigversion)) return false;
ret.push_back(std::move(sig));
ret.push_back(ToByteVector(pubkey));
return true;
}
case TX_SCRIPTHASH:
h160 = uint160(vSolutions[0]);
if (GetCScript(provider, sigdata, h160, scriptRet)) {
ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
return true;
}
// Could not find redeemScript, add to missing
sigdata.missing_redeem_script = h160;
return false;
case TX_MULTISIG: {
size_t required = vSolutions.front()[0];
ret.push_back(valtype()); // workaround CHECKMULTISIG bug
for (size_t i = 1; i < vSolutions.size() - 1; ++i) {
CPubKey pubkey = CPubKey(vSolutions[i]);
// We need to always call CreateSig in order to fill sigdata with all
// possible signatures that we can create. This will allow further PSBT
// processing to work as it needs all possible signature and pubkey pairs
if (CreateSig(creator, sigdata, provider, sig, pubkey, scriptPubKey, sigversion)) {
if (ret.size() < required + 1) {
ret.push_back(std::move(sig));
}
}
}
bool ok = ret.size() == required + 1;
for (size_t i = 0; i + ret.size() < required + 1; ++i) {
ret.push_back(valtype());
}
return ok;
}
case TX_WITNESS_V0_KEYHASH:
ret.push_back(vSolutions[0]);
return true;
case TX_WITNESS_V0_SCRIPTHASH:
CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(h160.begin());
if (GetCScript(provider, sigdata, h160, scriptRet)) {
ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
return true;
}
// Could not find witnessScript, add to missing
sigdata.missing_witness_script = uint256(vSolutions[0]);
return false;
case TX_TRUE:
return Params().anyonecanspend_aremine;
default:
return false;
}
}
static CScript PushAll(const std::vector<valtype>& values)
{
CScript result;
for (const valtype& v : values) {
if (v.size() == 0) {
result << OP_0;
} else if (v.size() == 1 && v[0] >= 1 && v[0] <= 16) {
result << CScript::EncodeOP_N(v[0]);
} else {
result << v;
}
}
return result;
}
bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata, unsigned int additional_flags)
{
if (sigdata.complete) return true;
std::vector<valtype> result;
txnouttype whichType;
bool solved = SignStep(provider, creator, fromPubKey, result, whichType, SigVersion::BASE, sigdata);
bool P2SH = false;
CScript subscript;
sigdata.scriptWitness.stack.clear();
if (solved && whichType == TX_SCRIPTHASH)
{
// Solver returns the subscript that needs to be evaluated;
// the final scriptSig is the signatures from that
// and then the serialized subscript:
subscript = CScript(result[0].begin(), result[0].end());
sigdata.redeem_script = subscript;
solved = solved && SignStep(provider, creator, subscript, result, whichType, SigVersion::BASE, sigdata) && whichType != TX_SCRIPTHASH;
P2SH = true;
}
if (solved && whichType == TX_WITNESS_V0_KEYHASH)
{
CScript witnessscript;
witnessscript << OP_DUP << OP_HASH160 << ToByteVector(result[0]) << OP_EQUALVERIFY << OP_CHECKSIG;
txnouttype subType;
solved = solved && SignStep(provider, creator, witnessscript, result, subType, SigVersion::WITNESS_V0, sigdata);
sigdata.scriptWitness.stack = result;
sigdata.witness = true;
result.clear();
}
else if (solved && whichType == TX_WITNESS_V0_SCRIPTHASH)
{
CScript witnessscript(result[0].begin(), result[0].end());
sigdata.witness_script = witnessscript;
txnouttype subType;
solved = solved && SignStep(provider, creator, witnessscript, result, subType, SigVersion::WITNESS_V0, sigdata) && subType != TX_SCRIPTHASH && subType != TX_WITNESS_V0_SCRIPTHASH && subType != TX_WITNESS_V0_KEYHASH;
result.push_back(std::vector<unsigned char>(witnessscript.begin(), witnessscript.end()));
sigdata.scriptWitness.stack = result;
sigdata.witness = true;
result.clear();
} else if (solved && whichType == TX_WITNESS_UNKNOWN) {
sigdata.witness = true;
}
if (P2SH) {
result.push_back(std::vector<unsigned char>(subscript.begin(), subscript.end()));
}
sigdata.scriptSig = PushAll(result);
// Test solution
sigdata.complete = solved && VerifyScript(sigdata.scriptSig, fromPubKey, &sigdata.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS|additional_flags, creator.Checker());
return sigdata.complete;
}
namespace {
class SignatureExtractorChecker final : public BaseSignatureChecker
{
private:
SignatureData& sigdata;
BaseSignatureChecker& checker;
public:
SignatureExtractorChecker(SignatureData& sigdata, BaseSignatureChecker& checker) : sigdata(sigdata), checker(checker) {}
bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override
{
if (checker.CheckSig(scriptSig, vchPubKey, scriptCode, sigversion)) {
CPubKey pubkey(vchPubKey);
sigdata.signatures.emplace(pubkey.GetID(), SigPair(pubkey, scriptSig));
return true;
}
return false;
}
};
struct Stacks
{
std::vector<valtype> script;
std::vector<valtype> witness;
Stacks() = delete;
Stacks(const Stacks&) = delete;
explicit Stacks(const SignatureData& data) : witness(data.scriptWitness.stack) {
EvalScript(script, data.scriptSig, SCRIPT_VERIFY_STRICTENC, BaseSignatureChecker(), SigVersion::BASE);
}
};
}
// Extracts signatures and scripts from incomplete scriptSigs. Please do not extend this, use PSBT instead
SignatureData DataFromTransaction(const CMutableTransaction& tx, unsigned int nIn, const CTxOut& txout)
{
SignatureData data;
assert(tx.vin.size() > nIn);
data.scriptSig = tx.vin[nIn].scriptSig;
data.scriptWitness = tx.witness.vtxinwit.size() > nIn ? tx.witness.vtxinwit[nIn].scriptWitness : CScriptWitness();
Stacks stack(data);
// Get signatures
MutableTransactionSignatureChecker tx_checker(&tx, nIn, txout.nValue);
SignatureExtractorChecker extractor_checker(data, tx_checker);
if (VerifyScript(data.scriptSig, txout.scriptPubKey, &data.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, extractor_checker)) {
data.complete = true;
return data;
}
// Get scripts
std::vector<std::vector<unsigned char>> solutions;
txnouttype script_type = Solver(txout.scriptPubKey, solutions);
SigVersion sigversion = SigVersion::BASE;
CScript next_script = txout.scriptPubKey;
if (script_type == TX_SCRIPTHASH && !stack.script.empty() && !stack.script.back().empty()) {
// Get the redeemScript
CScript redeem_script(stack.script.back().begin(), stack.script.back().end());
data.redeem_script = redeem_script;
next_script = std::move(redeem_script);
// Get redeemScript type
script_type = Solver(next_script, solutions);
stack.script.pop_back();
}
if (script_type == TX_WITNESS_V0_SCRIPTHASH && !stack.witness.empty() && !stack.witness.back().empty()) {
// Get the witnessScript
CScript witness_script(stack.witness.back().begin(), stack.witness.back().end());
data.witness_script = witness_script;
next_script = std::move(witness_script);
// Get witnessScript type
script_type = Solver(next_script, solutions);
stack.witness.pop_back();
stack.script = std::move(stack.witness);
stack.witness.clear();
sigversion = SigVersion::WITNESS_V0;
}
if (script_type == TX_MULTISIG && !stack.script.empty()) {
// Build a map of pubkey -> signature by matching sigs to pubkeys:
assert(solutions.size() > 1);
unsigned int num_pubkeys = solutions.size()-2;
unsigned int last_success_key = 0;
for (const valtype& sig : stack.script) {
for (unsigned int i = last_success_key; i < num_pubkeys; ++i) {
const valtype& pubkey = solutions[i+1];
// We either have a signature for this pubkey, or we have found a signature and it is valid
if (data.signatures.count(CPubKey(pubkey).GetID()) || extractor_checker.CheckSig(sig, pubkey, next_script, sigversion)) {
last_success_key = i + 1;
break;
}
}
}
}
return data;
}
void UpdateTransaction(CMutableTransaction& tx, const size_t nIn, const SignatureData& data) {
assert(tx.vin.size() > nIn);
tx.witness.vtxinwit.resize(tx.vin.size());
tx.vin[nIn].scriptSig = data.scriptSig;
tx.witness.vtxinwit[nIn].scriptWitness = data.scriptWitness;
}
void SignatureData::MergeSignatureData(SignatureData sigdata)
{
if (complete) return;
if (sigdata.complete) {
*this = std::move(sigdata);
return;
}
if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
redeem_script = sigdata.redeem_script;
}
if (witness_script.empty() && !sigdata.witness_script.empty()) {
witness_script = sigdata.witness_script;
}
signatures.insert(std::make_move_iterator(sigdata.signatures.begin()), std::make_move_iterator(sigdata.signatures.end()));
}
bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CConfidentialValue& amount, int nHashType)
{
assert(nIn < txTo.vin.size());
txTo.witness.vtxinwit.resize(txTo.vin.size());
CTransaction txToConst(txTo);
//TransactionSignatureCreator creator(&keystore, &txToConst, nIn, amount, nHashType);
MutableTransactionSignatureCreator creator(&txTo, nIn, amount, nHashType);
SignatureData sigdata;
bool ret = ProduceSignature(provider, creator, fromPubKey, sigdata);
UpdateTransaction(txTo, nIn, sigdata);
return ret;
}
bool SignSignature(const SigningProvider &provider, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType)
{
assert(nIn < txTo.vin.size());
CTxIn& txin = txTo.vin[nIn];
assert(txin.prevout.n < txFrom.vout.size());
const CTxOut& txout = txFrom.vout[txin.prevout.n];
return SignSignature(provider, txout.scriptPubKey, txTo, nIn, txout.nValue, nHashType);
}
namespace {
/** Dummy signature checker which accepts all signatures. */
class DummySignatureChecker final : public BaseSignatureChecker
{
public:
DummySignatureChecker() {}
bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override { return true; }
};
const DummySignatureChecker DUMMY_CHECKER;
class DummySignatureCreator final : public BaseSignatureCreator {
private:
char m_r_len = 32;
char m_s_len = 32;
public:
DummySignatureCreator(char r_len, char s_len) : m_r_len(r_len), m_s_len(s_len) {}
const BaseSignatureChecker& Checker() const override { return DUMMY_CHECKER; }
bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override
{
// Create a dummy signature that is a valid DER-encoding
vchSig.assign(m_r_len + m_s_len + 7, '\000');
vchSig[0] = 0x30;
vchSig[1] = m_r_len + m_s_len + 4;
vchSig[2] = 0x02;
vchSig[3] = m_r_len;
vchSig[4] = 0x01;
vchSig[4 + m_r_len] = 0x02;
vchSig[5 + m_r_len] = m_s_len;
vchSig[6 + m_r_len] = 0x01;
vchSig[6 + m_r_len + m_s_len] = SIGHASH_ALL;
return true;
}
};
}
const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR = DummySignatureCreator(32, 32);
const BaseSignatureCreator& DUMMY_MAXIMUM_SIGNATURE_CREATOR = DummySignatureCreator(33, 32);
bool IsSolvable(const SigningProvider& provider, const CScript& script)
{
// This check is to make sure that the script we created can actually be solved for and signed by us
// if we were to have the private keys. This is just to make sure that the script is valid and that,
// if found in a transaction, we would still accept and relay that transaction. In particular,
// it will reject witness outputs that require signing with an uncompressed public key.
SignatureData sigs;
// Make sure that STANDARD_SCRIPT_VERIFY_FLAGS includes SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, the most
// important property this function is designed to test for.
static_assert(STANDARD_SCRIPT_VERIFY_FLAGS & SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, "IsSolvable requires standard script flags to include WITNESS_PUBKEYTYPE");
if (ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, script, sigs)) {
// VerifyScript check is just defensive, and should never fail.
bool verified = VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, DUMMY_CHECKER);
assert(verified);
return true;
}
return false;
}
bool IsSegWitOutput(const SigningProvider& provider, const CScript& script)
{
std::vector<valtype> solutions;
auto whichtype = Solver(script, solutions);
if (whichtype == TX_WITNESS_V0_SCRIPTHASH || whichtype == TX_WITNESS_V0_KEYHASH || whichtype == TX_WITNESS_UNKNOWN) return true;
if (whichtype == TX_SCRIPTHASH) {
auto h160 = uint160(solutions[0]);
CScript subscript;
if (provider.GetCScript(h160, subscript)) {
whichtype = Solver(subscript, solutions);
if (whichtype == TX_WITNESS_V0_SCRIPTHASH || whichtype == TX_WITNESS_V0_KEYHASH || whichtype == TX_WITNESS_UNKNOWN) return true;
}
}
return false;
}
bool SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore, const std::map<COutPoint, Coin>& coins, int nHashType, std::map<int, std::string>& input_errors)
{
bool fHashSingle = ((nHashType & ~SIGHASH_ANYONECANPAY) == SIGHASH_SINGLE);
// Use CTransaction for the constant parts of the
// transaction to avoid rehashing.
const CTransaction txConst(mtx);
// Sign what we can, including pegin inputs:
mtx.witness.vtxinwit.resize(mtx.vin.size());
for (unsigned int i = 0; i < mtx.vin.size(); i++) {
CTxIn& txin = mtx.vin[i];
const CTxInWitness& inWitness = mtx.witness.vtxinwit[i];
CTxOut prevTxOut;
if (txin.m_is_pegin) {
prevTxOut = GetPeginOutputFromWitness(mtx.witness.vtxinwit[i].m_pegin_witness);
} else {
auto coin = coins.find(txin.prevout);
prevTxOut = coin->second.out;
}
const CScript& prevPubKey = prevTxOut.scriptPubKey;
const CConfidentialValue& amount = prevTxOut.nValue;
SignatureData sigdata = DataFromTransaction(mtx, i, prevTxOut);
// Only sign SIGHASH_SINGLE if there's a corresponding output:
if (!fHashSingle || (i < mtx.vout.size())) {
ProduceSignature(*keystore, MutableTransactionSignatureCreator(&mtx, i, amount, nHashType), prevPubKey, sigdata);
}
UpdateTransaction(mtx, i, sigdata); // ELEMENTS: is UpdateInput in Core
// amount must be specified for valid segwit signature
if (amount.IsExplicit() && amount.GetAmount() == MAX_MONEY && !mtx.witness.vtxinwit[i].scriptWitness.IsNull()) {
input_errors[i] = "Missing amount";
continue;
}
ScriptError serror = SCRIPT_ERR_OK;
if (!VerifyScript(txin.scriptSig, prevPubKey, &inWitness.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, TransactionSignatureChecker(&txConst, i, amount), &serror)) {
if (serror == SCRIPT_ERR_INVALID_STACK_OPERATION) {
// Unable to sign input and verification failed (possible attempt to partially sign).
input_errors[i] = "Unable to sign input, invalid stack size (possibly missing key)";
} else if (serror == SCRIPT_ERR_SIG_NULLFAIL) {
// Verification failed (possibly due to insufficient signatures).
input_errors[i] = "CHECK(MULTI)SIG failing with non-zero signature (possibly need more signatures)";
} else {
input_errors[i] = ScriptErrorString(serror);
}
} else {
// If this input succeeds, make sure there is no error set for it
input_errors.erase(i);
}
}
return input_errors.empty();
}
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