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bitcoin/src/script/sign.cpp
Andrew Chow 0422beb9bd Make SignatureData able to store signatures and scripts 
In addition to having the scriptSig and scriptWitness, have SignatureData
also be able to store just the signatures (pubkeys mapped to sigs) and
scripts (script ids mapped to scripts).

Also have DataFromTransaction be able to extract signatures and scripts
from the scriptSig and scriptWitness of an input to put them in SignatureData.

Adds a new SignatureChecker which takes a SignatureData and puts pubkeys
and signatures into it when it successfully verifies a signature.

Adds a new field in SignatureData which stores whether the SignatureData
was complete. This allows us to also update the scriptSig and
scriptWitness to the final one when updating a SignatureData with another
one.
2018-07-03 17:18:52 -07:00

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2017 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 <policy/policy.h>
#include <primitives/transaction.h>
#include <script/standard.h>
#include <uint256.h>
typedef std::vector<unsigned char> valtype;
MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& 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;
}
/**
* 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)
{
CScript scriptRet;
uint160 h160;
ret.clear();
std::vector<unsigned char> sig;
std::vector<valtype> vSolutions;
if (!Solver(scriptPubKey, whichTypeRet, vSolutions))
return false;
switch (whichTypeRet)
{
case TX_NONSTANDARD:
case TX_NULL_DATA:
case TX_WITNESS_UNKNOWN:
return false;
case TX_PUBKEY:
if (!creator.CreateSig(provider, sig, CPubKey(vSolutions[0]).GetID(), scriptPubKey, sigversion)) return false;
ret.push_back(std::move(sig));
return true;
case TX_PUBKEYHASH: {
CKeyID keyID = CKeyID(uint160(vSolutions[0]));
if (!creator.CreateSig(provider, sig, keyID, scriptPubKey, sigversion)) return false;
ret.push_back(std::move(sig));
CPubKey pubkey;
provider.GetPubKey(keyID, pubkey);
ret.push_back(ToByteVector(pubkey));
return true;
}
case TX_SCRIPTHASH:
if (provider.GetCScript(uint160(vSolutions[0]), scriptRet)) {
ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
return true;
}
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]);
if (ret.size() < required + 1 && creator.CreateSig(provider, sig, pubkey.GetID(), scriptPubKey, sigversion)) {
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 (provider.GetCScript(h160, scriptRet)) {
ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
return true;
}
return false;
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)
{
if (sigdata.complete) return true;
std::vector<valtype> result;
txnouttype whichType;
bool solved = SignStep(provider, creator, fromPubKey, result, whichType, SigVersion::BASE);
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());
solved = solved && SignStep(provider, creator, subscript, result, whichType, SigVersion::BASE) && 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.scriptWitness.stack = result;
result.clear();
}
else if (solved && whichType == TX_WITNESS_V0_SCRIPTHASH)
{
CScript witnessscript(result[0].begin(), result[0].end());
txnouttype subType;
solved = solved && SignStep(provider, creator, witnessscript, result, subType, SigVersion::WITNESS_V0) && 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;
result.clear();
}
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, creator.Checker());
return sigdata.complete;
}
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;
};
bool SignatureExtractorChecker::CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
{
if (checker.CheckSig(scriptSig, vchPubKey, scriptCode, sigversion)) {
CPubKey pubkey(vchPubKey);
sigdata.signatures.emplace(pubkey.GetID(), SigPair(pubkey, scriptSig));
return true;
}
return false;
}
namespace
{
struct Stacks
{
std::vector<valtype> script;
std::vector<valtype> witness;
Stacks() {}
explicit Stacks(const std::vector<valtype>& scriptSigStack_) : script(scriptSigStack_), witness() {}
explicit Stacks(const SignatureData& data) : witness(data.scriptWitness.stack) {
EvalScript(script, data.scriptSig, SCRIPT_VERIFY_STRICTENC, BaseSignatureChecker(), SigVersion::BASE);
}
SignatureData Output() const {
SignatureData result;
result.scriptSig = PushAll(script);
result.scriptWitness.stack = witness;
return result;
}
};
}
// 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.vin[nIn].scriptWitness;
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
txnouttype script_type;
std::vector<std::vector<unsigned char>> solutions;
Solver(txout.scriptPubKey, script_type, 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
Solver(next_script, script_type, 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
Solver(next_script, script_type, 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 UpdateInput(CTxIn& input, const SignatureData& data)
{
input.scriptSig = data.scriptSig;
input.scriptWitness = data.scriptWitness;
}
bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CAmount& amount, int nHashType)
{
assert(nIn < txTo.vin.size());
MutableTransactionSignatureCreator creator(&txTo, nIn, amount, nHashType);
SignatureData sigdata;
bool ret = ProduceSignature(provider, creator, fromPubKey, sigdata);
UpdateInput(txTo.vin.at(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);
}
static std::vector<valtype> CombineMultisig(const CScript& scriptPubKey, const BaseSignatureChecker& checker,
const std::vector<valtype>& vSolutions,
const std::vector<valtype>& sigs1, const std::vector<valtype>& sigs2, SigVersion sigversion)
{
// Combine all the signatures we've got:
std::set<valtype> allsigs;
for (const valtype& v : sigs1)
{
if (!v.empty())
allsigs.insert(v);
}
for (const valtype& v : sigs2)
{
if (!v.empty())
allsigs.insert(v);
}
// Build a map of pubkey -> signature by matching sigs to pubkeys:
assert(vSolutions.size() > 1);
unsigned int nSigsRequired = vSolutions.front()[0];
unsigned int nPubKeys = vSolutions.size()-2;
std::map<valtype, valtype> sigs;
for (const valtype& sig : allsigs)
{
for (unsigned int i = 0; i < nPubKeys; i++)
{
const valtype& pubkey = vSolutions[i+1];
if (sigs.count(pubkey))
continue; // Already got a sig for this pubkey
if (checker.CheckSig(sig, pubkey, scriptPubKey, sigversion))
{
sigs[pubkey] = sig;
break;
}
}
}
// Now build a merged CScript:
unsigned int nSigsHave = 0;
std::vector<valtype> result; result.push_back(valtype()); // pop-one-too-many workaround
for (unsigned int i = 0; i < nPubKeys && nSigsHave < nSigsRequired; i++)
{
if (sigs.count(vSolutions[i+1]))
{
result.push_back(sigs[vSolutions[i+1]]);
++nSigsHave;
}
}
// Fill any missing with OP_0:
for (unsigned int i = nSigsHave; i < nSigsRequired; i++)
result.push_back(valtype());
return result;
}
static Stacks CombineSignatures(const CScript& scriptPubKey, const BaseSignatureChecker& checker,
const txnouttype txType, const std::vector<valtype>& vSolutions,
Stacks sigs1, Stacks sigs2, SigVersion sigversion)
{
switch (txType)
{
case TX_NONSTANDARD:
case TX_NULL_DATA:
case TX_WITNESS_UNKNOWN:
// Don't know anything about this, assume bigger one is correct:
if (sigs1.script.size() >= sigs2.script.size())
return sigs1;
return sigs2;
case TX_PUBKEY:
case TX_PUBKEYHASH:
// Signatures are bigger than placeholders or empty scripts:
if (sigs1.script.empty() || sigs1.script[0].empty())
return sigs2;
return sigs1;
case TX_WITNESS_V0_KEYHASH:
// Signatures are bigger than placeholders or empty scripts:
if (sigs1.witness.empty() || sigs1.witness[0].empty())
return sigs2;
return sigs1;
case TX_SCRIPTHASH:
if (sigs1.script.empty() || sigs1.script.back().empty())
return sigs2;
else if (sigs2.script.empty() || sigs2.script.back().empty())
return sigs1;
else
{
// Recur to combine:
valtype spk = sigs1.script.back();
CScript pubKey2(spk.begin(), spk.end());
txnouttype txType2;
std::vector<std::vector<unsigned char> > vSolutions2;
Solver(pubKey2, txType2, vSolutions2);
sigs1.script.pop_back();
sigs2.script.pop_back();
Stacks result = CombineSignatures(pubKey2, checker, txType2, vSolutions2, sigs1, sigs2, sigversion);
result.script.push_back(spk);
return result;
}
case TX_MULTISIG:
return Stacks(CombineMultisig(scriptPubKey, checker, vSolutions, sigs1.script, sigs2.script, sigversion));
case TX_WITNESS_V0_SCRIPTHASH:
if (sigs1.witness.empty() || sigs1.witness.back().empty())
return sigs2;
else if (sigs2.witness.empty() || sigs2.witness.back().empty())
return sigs1;
else
{
// Recur to combine:
CScript pubKey2(sigs1.witness.back().begin(), sigs1.witness.back().end());
txnouttype txType2;
std::vector<valtype> vSolutions2;
Solver(pubKey2, txType2, vSolutions2);
sigs1.witness.pop_back();
sigs1.script = sigs1.witness;
sigs1.witness.clear();
sigs2.witness.pop_back();
sigs2.script = sigs2.witness;
sigs2.witness.clear();
Stacks result = CombineSignatures(pubKey2, checker, txType2, vSolutions2, sigs1, sigs2, SigVersion::WITNESS_V0);
result.witness = result.script;
result.script.clear();
result.witness.push_back(valtype(pubKey2.begin(), pubKey2.end()));
return result;
}
default:
return Stacks();
}
}
SignatureData CombineSignatures(const CScript& scriptPubKey, const BaseSignatureChecker& checker,
const SignatureData& scriptSig1, const SignatureData& scriptSig2)
{
txnouttype txType;
std::vector<std::vector<unsigned char> > vSolutions;
Solver(scriptPubKey, txType, vSolutions);
return CombineSignatures(scriptPubKey, checker, txType, vSolutions, Stacks(scriptSig1), Stacks(scriptSig2), SigVersion::BASE).Output();
}
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 {
public:
DummySignatureCreator() {}
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(72, '\000');
vchSig[0] = 0x30;
vchSig[1] = 69;
vchSig[2] = 0x02;
vchSig[3] = 33;
vchSig[4] = 0x01;
vchSig[4 + 33] = 0x02;
vchSig[5 + 33] = 32;
vchSig[6 + 33] = 0x01;
vchSig[6 + 33 + 32] = SIGHASH_ALL;
return true;
}
};
}
const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR = DummySignatureCreator();
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.
assert(VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, DUMMY_CHECKER));
return true;
}
return false;
}
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