path: root/src/scriptutils.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2013 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "scriptutils.h"

#include "core.h"
#include "key.h"
#include "keystore.h"
#include "uint256.h"
#include "util.h"

#include <boost/foreach.hpp>

using namespace std;

typedef vector<unsigned char> valtype;

const char* GetTxnOutputType(txnouttype t)
{
    switch (t)
    {
    case TX_NONSTANDARD: return "nonstandard";
    case TX_PUBKEY: return "pubkey";
    case TX_PUBKEYHASH: return "pubkeyhash";
    case TX_SCRIPTHASH: return "scripthash";
    case TX_MULTISIG: return "multisig";
    case TX_NULL_DATA: return "nulldata";
    }
    return NULL;
}

//
// Return public keys or hashes from scriptPubKey, for 'standard' transaction types.
//
bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsigned char> >& vSolutionsRet)
{
    // Templates
    static multimap<txnouttype, CScript> mTemplates;
    if (mTemplates.empty())
    {
        // Standard tx, sender provides pubkey, receiver adds signature
        mTemplates.insert(make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));

        // Bitcoin address tx, sender provides hash of pubkey, receiver provides signature and pubkey
        mTemplates.insert(make_pair(TX_PUBKEYHASH, CScript() << OP_DUP << OP_HASH160 << OP_PUBKEYHASH << OP_EQUALVERIFY << OP_CHECKSIG));

        // Sender provides N pubkeys, receivers provides M signatures
        mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));

        // Empty, provably prunable, data-carrying output
        if (GetBoolArg("-datacarrier", true))
            mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN << OP_SMALLDATA));
        mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN));
    }

    // Shortcut for pay-to-script-hash, which are more constrained than the other types:
    // it is always OP_HASH160 20 [20 byte hash] OP_EQUAL
    if (scriptPubKey.IsPayToScriptHash())
    {
        typeRet = TX_SCRIPTHASH;
        vector<unsigned char> hashBytes(scriptPubKey.begin()+2, scriptPubKey.begin()+22);
        vSolutionsRet.push_back(hashBytes);
        return true;
    }

    // Scan templates
    const CScript& script1 = scriptPubKey;
    BOOST_FOREACH(const PAIRTYPE(txnouttype, CScript)& tplate, mTemplates)
    {
        const CScript& script2 = tplate.second;
        vSolutionsRet.clear();

        opcodetype opcode1, opcode2;
        vector<unsigned char> vch1, vch2;

        // Compare
        CScript::const_iterator pc1 = script1.begin();
        CScript::const_iterator pc2 = script2.begin();
        while (true)
        {
            if (pc1 == script1.end() && pc2 == script2.end())
            {
                // Found a match
                typeRet = tplate.first;
                if (typeRet == TX_MULTISIG)
                {
                    // Additional checks for TX_MULTISIG:
                    unsigned char m = vSolutionsRet.front()[0];
                    unsigned char n = vSolutionsRet.back()[0];
                    if (m < 1 || n < 1 || m > n || vSolutionsRet.size()-2 != n)
                        return false;
                }
                return true;
            }
            if (!script1.GetOp(pc1, opcode1, vch1))
                break;
            if (!script2.GetOp(pc2, opcode2, vch2))
                break;

            // Template matching opcodes:
            if (opcode2 == OP_PUBKEYS)
            {
                while (vch1.size() >= 33 && vch1.size() <= 65)
                {
                    vSolutionsRet.push_back(vch1);
                    if (!script1.GetOp(pc1, opcode1, vch1))
                        break;
                }
                if (!script2.GetOp(pc2, opcode2, vch2))
                    break;
                // Normal situation is to fall through
                // to other if/else statements
            }

            if (opcode2 == OP_PUBKEY)
            {
                if (vch1.size() < 33 || vch1.size() > 65)
                    break;
                vSolutionsRet.push_back(vch1);
            }
            else if (opcode2 == OP_PUBKEYHASH)
            {
                if (vch1.size() != sizeof(uint160))
                    break;
                vSolutionsRet.push_back(vch1);
            }
            else if (opcode2 == OP_SMALLINTEGER)
            {   // Single-byte small integer pushed onto vSolutions
                if (opcode1 == OP_0 ||
                    (opcode1 >= OP_1 && opcode1 <= OP_16))
                {
                    char n = (char)CScript::DecodeOP_N(opcode1);
                    vSolutionsRet.push_back(valtype(1, n));
                }
                else
                    break;
            }
            else if (opcode2 == OP_SMALLDATA)
            {
                // small pushdata, <= MAX_OP_RETURN_RELAY bytes
                if (vch1.size() > MAX_OP_RETURN_RELAY)
                    break;
            }
            else if (opcode1 != opcode2 || vch1 != vch2)
            {
                // Others must match exactly
                break;
            }
        }
    }

    vSolutionsRet.clear();
    typeRet = TX_NONSTANDARD;
    return false;
}


bool Sign1(const CKeyID& address, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
{
    CKey key;
    if (!keystore.GetKey(address, key))
        return false;

    vector<unsigned char> vchSig;
    if (!key.Sign(hash, vchSig))
        return false;
    vchSig.push_back((unsigned char)nHashType);
    scriptSigRet << vchSig;

    return true;
}

bool SignN(const vector<valtype>& multisigdata, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
{
    int nSigned = 0;
    int nRequired = multisigdata.front()[0];
    for (unsigned int i = 1; i < multisigdata.size()-1 && nSigned < nRequired; i++)
    {
        const valtype& pubkey = multisigdata[i];
        CKeyID keyID = CPubKey(pubkey).GetID();
        if (Sign1(keyID, keystore, hash, nHashType, scriptSigRet))
            ++nSigned;
    }
    return nSigned==nRequired;
}

//
// Sign scriptPubKey with private keys stored in keystore, given transaction hash and hash type.
// 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.
//
bool Solver(const CKeyStore& keystore, const CScript& scriptPubKey, uint256 hash, int nHashType,
                  CScript& scriptSigRet, txnouttype& whichTypeRet)
{
    scriptSigRet.clear();

    vector<valtype> vSolutions;
    if (!Solver(scriptPubKey, whichTypeRet, vSolutions))
        return false;

    CKeyID keyID;
    switch (whichTypeRet)
    {
    case TX_NONSTANDARD:
    case TX_NULL_DATA:
        return false;
    case TX_PUBKEY:
        keyID = CPubKey(vSolutions[0]).GetID();
        return Sign1(keyID, keystore, hash, nHashType, scriptSigRet);
    case TX_PUBKEYHASH:
        keyID = CKeyID(uint160(vSolutions[0]));
        if (!Sign1(keyID, keystore, hash, nHashType, scriptSigRet))
            return false;
        else
        {
            CPubKey vch;
            keystore.GetPubKey(keyID, vch);
            scriptSigRet << vch;
        }
        return true;
    case TX_SCRIPTHASH:
        return keystore.GetCScript(uint160(vSolutions[0]), scriptSigRet);

    case TX_MULTISIG:
        scriptSigRet << OP_0; // workaround CHECKMULTISIG bug
        return (SignN(vSolutions, keystore, hash, nHashType, scriptSigRet));
    }
    return false;
}

int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned char> >& vSolutions)
{
    switch (t)
    {
    case TX_NONSTANDARD:
    case TX_NULL_DATA:
        return -1;
    case TX_PUBKEY:
        return 1;
    case TX_PUBKEYHASH:
        return 2;
    case TX_MULTISIG:
        if (vSolutions.size() < 1 || vSolutions[0].size() < 1)
            return -1;
        return vSolutions[0][0] + 1;
    case TX_SCRIPTHASH:
        return 1; // doesn't include args needed by the script
    }
    return -1;
}

bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType)
{
    vector<valtype> vSolutions;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    if (whichType == TX_MULTISIG)
    {
        unsigned char m = vSolutions.front()[0];
        unsigned char n = vSolutions.back()[0];
        // Support up to x-of-3 multisig txns as standard
        if (n < 1 || n > 3)
            return false;
        if (m < 1 || m > n)
            return false;
    }

    return whichType != TX_NONSTANDARD;
}


unsigned int HaveKeys(const vector<valtype>& pubkeys, const CKeyStore& keystore)
{
    unsigned int nResult = 0;
    BOOST_FOREACH(const valtype& pubkey, pubkeys)
    {
        CKeyID keyID = CPubKey(pubkey).GetID();
        if (keystore.HaveKey(keyID))
            ++nResult;
    }
    return nResult;
}

isminetype IsMine(const CKeyStore &keystore, const CTxDestination& dest)
{
    CScript script;
    script.SetDestination(dest);
    return IsMine(keystore, script);
}

isminetype IsMine(const CKeyStore &keystore, const CScript& scriptPubKey)
{
    vector<valtype> vSolutions;
    txnouttype whichType;
    if (!Solver(scriptPubKey, whichType, vSolutions)) {
        if (keystore.HaveWatchOnly(scriptPubKey))
            return ISMINE_WATCH_ONLY;
        return ISMINE_NO;
    }

    CKeyID keyID;
    switch (whichType)
    {
    case TX_NONSTANDARD:
    case TX_NULL_DATA:
        break;
    case TX_PUBKEY:
        keyID = CPubKey(vSolutions[0]).GetID();
        if (keystore.HaveKey(keyID))
            return ISMINE_SPENDABLE;
        break;
    case TX_PUBKEYHASH:
        keyID = CKeyID(uint160(vSolutions[0]));
        if (keystore.HaveKey(keyID))
            return ISMINE_SPENDABLE;
        break;
    case TX_SCRIPTHASH:
    {
        CScriptID scriptID = CScriptID(uint160(vSolutions[0]));
        CScript subscript;
        if (keystore.GetCScript(scriptID, subscript)) {
            isminetype ret = IsMine(keystore, subscript);
            if (ret == ISMINE_SPENDABLE)
                return ret;
        }
        break;
    }
    case TX_MULTISIG:
    {
        // Only consider transactions "mine" if we own ALL the
        // keys involved. multi-signature transactions that are
        // partially owned (somebody else has a key that can spend
        // them) enable spend-out-from-under-you attacks, especially
        // in shared-wallet situations.
        vector<valtype> keys(vSolutions.begin()+1, vSolutions.begin()+vSolutions.size()-1);
        if (HaveKeys(keys, keystore) == keys.size())
            return ISMINE_SPENDABLE;
        break;
    }
    }

    if (keystore.HaveWatchOnly(scriptPubKey))
        return ISMINE_WATCH_ONLY;
    return ISMINE_NO;
}

bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
{
    vector<valtype> vSolutions;
    txnouttype whichType;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    if (whichType == TX_PUBKEY)
    {
        addressRet = CPubKey(vSolutions[0]).GetID();
        return true;
    }
    else if (whichType == TX_PUBKEYHASH)
    {
        addressRet = CKeyID(uint160(vSolutions[0]));
        return true;
    }
    else if (whichType == TX_SCRIPTHASH)
    {
        addressRet = CScriptID(uint160(vSolutions[0]));
        return true;
    }
    // Multisig txns have more than one address...
    return false;
}

bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, vector<CTxDestination>& addressRet, int& nRequiredRet)
{
    addressRet.clear();
    typeRet = TX_NONSTANDARD;
    vector<valtype> vSolutions;
    if (!Solver(scriptPubKey, typeRet, vSolutions))
        return false;
    if (typeRet == TX_NULL_DATA){
        // This is data, not addresses
        return false;
    }

    if (typeRet == TX_MULTISIG)
    {
        nRequiredRet = vSolutions.front()[0];
        for (unsigned int i = 1; i < vSolutions.size()-1; i++)
        {
            CTxDestination address = CPubKey(vSolutions[i]).GetID();
            addressRet.push_back(address);
        }
    }
    else
    {
        nRequiredRet = 1;
        CTxDestination address;
        if (!ExtractDestination(scriptPubKey, address))
           return false;
        addressRet.push_back(address);
    }

    return true;
}

class CAffectedKeysVisitor : public boost::static_visitor<void> {
private:
    const CKeyStore &keystore;
    std::vector<CKeyID> &vKeys;

public:
    CAffectedKeysVisitor(const CKeyStore &keystoreIn, std::vector<CKeyID> &vKeysIn) : keystore(keystoreIn), vKeys(vKeysIn) {}

    void Process(const CScript &script) {
        txnouttype type;
        std::vector<CTxDestination> vDest;
        int nRequired;
        if (ExtractDestinations(script, type, vDest, nRequired)) {
            BOOST_FOREACH(const CTxDestination &dest, vDest)
                boost::apply_visitor(*this, dest);
        }
    }

    void operator()(const CKeyID &keyId) {
        if (keystore.HaveKey(keyId))
            vKeys.push_back(keyId);
    }

    void operator()(const CScriptID &scriptId) {
        CScript script;
        if (keystore.GetCScript(scriptId, script))
            Process(script);
    }

    void operator()(const CNoDestination &none) {}
};

void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys) {
    CAffectedKeysVisitor(keystore, vKeys).Process(scriptPubKey);
}

bool SignSignature(const CKeyStore &keystore, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, int nHashType)
{
    assert(nIn < txTo.vin.size());
    CTxIn& txin = txTo.vin[nIn];

    // Leave out the signature from the hash, since a signature can't sign itself.
    // The checksig op will also drop the signatures from its hash.
    uint256 hash = SignatureHash(fromPubKey, txTo, nIn, nHashType);

    txnouttype whichType;
    if (!Solver(keystore, fromPubKey, hash, nHashType, txin.scriptSig, whichType))
        return false;

    if (whichType == TX_SCRIPTHASH)
    {
        // Solver returns the subscript that need to be evaluated;
        // the final scriptSig is the signatures from that
        // and then the serialized subscript:
        CScript subscript = txin.scriptSig;

        // Recompute txn hash using subscript in place of scriptPubKey:
        uint256 hash2 = SignatureHash(subscript, txTo, nIn, nHashType);

        txnouttype subType;
        bool fSolved =
            Solver(keystore, subscript, hash2, nHashType, txin.scriptSig, subType) && subType != TX_SCRIPTHASH;
        // Append serialized subscript whether or not it is completely signed:
        txin.scriptSig << static_cast<valtype>(subscript);
        if (!fSolved) return false;
    }

    // Test solution
    return VerifyScript(txin.scriptSig, fromPubKey, txTo, nIn, STANDARD_SCRIPT_VERIFY_FLAGS, 0);
}

bool SignSignature(const CKeyStore &keystore, 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(keystore, txout.scriptPubKey, txTo, nIn, nHashType);
}

static CScript PushAll(const vector<valtype>& values)
{
    CScript result;
    BOOST_FOREACH(const valtype& v, values)
        result << v;
    return result;
}

static CScript CombineMultisig(CScript scriptPubKey, const CMutableTransaction& txTo, unsigned int nIn,
                               const vector<valtype>& vSolutions,
                               vector<valtype>& sigs1, vector<valtype>& sigs2)
{
    // Combine all the signatures we've got:
    set<valtype> allsigs;
    BOOST_FOREACH(const valtype& v, sigs1)
    {
        if (!v.empty())
            allsigs.insert(v);
    }
    BOOST_FOREACH(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;
    map<valtype, valtype> sigs;
    BOOST_FOREACH(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 (CheckSig(sig, pubkey, scriptPubKey, txTo, nIn, 0, 0))
            {
                sigs[pubkey] = sig;
                break;
            }
        }
    }
    // Now build a merged CScript:
    unsigned int nSigsHave = 0;
    CScript result; result << OP_0; // pop-one-too-many workaround
    for (unsigned int i = 0; i < nPubKeys && nSigsHave < nSigsRequired; i++)
    {
        if (sigs.count(vSolutions[i+1]))
        {
            result << sigs[vSolutions[i+1]];
            ++nSigsHave;
        }
    }
    // Fill any missing with OP_0:
    for (unsigned int i = nSigsHave; i < nSigsRequired; i++)
        result << OP_0;

    return result;
}

static CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                                 const txnouttype txType, const vector<valtype>& vSolutions,
                                 vector<valtype>& sigs1, vector<valtype>& sigs2)
{
    switch (txType)
    {
    case TX_NONSTANDARD:
    case TX_NULL_DATA:
        // Don't know anything about this, assume bigger one is correct:
        if (sigs1.size() >= sigs2.size())
            return PushAll(sigs1);
        return PushAll(sigs2);
    case TX_PUBKEY:
    case TX_PUBKEYHASH:
        // Signatures are bigger than placeholders or empty scripts:
        if (sigs1.empty() || sigs1[0].empty())
            return PushAll(sigs2);
        return PushAll(sigs1);
    case TX_SCRIPTHASH:
        if (sigs1.empty() || sigs1.back().empty())
            return PushAll(sigs2);
        else if (sigs2.empty() || sigs2.back().empty())
            return PushAll(sigs1);
        else
        {
            // Recur to combine:
            valtype spk = sigs1.back();
            CScript pubKey2(spk.begin(), spk.end());

            txnouttype txType2;
            vector<vector<unsigned char> > vSolutions2;
            Solver(pubKey2, txType2, vSolutions2);
            sigs1.pop_back();
            sigs2.pop_back();
            CScript result = CombineSignatures(pubKey2, txTo, nIn, txType2, vSolutions2, sigs1, sigs2);
            result << spk;
            return result;
        }
    case TX_MULTISIG:
        return CombineMultisig(scriptPubKey, txTo, nIn, vSolutions, sigs1, sigs2);
    }

    return CScript();
}

CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                          const CScript& scriptSig1, const CScript& scriptSig2)
{
    txnouttype txType;
    vector<vector<unsigned char> > vSolutions;
    Solver(scriptPubKey, txType, vSolutions);

    vector<valtype> stack1;
    EvalScript(stack1, scriptSig1, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC, 0);
    vector<valtype> stack2;
    EvalScript(stack2, scriptSig2, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC, 0);

    return CombineSignatures(scriptPubKey, txTo, nIn, txType, vSolutions, stack1, stack2);
}

bool CScriptCompressor::IsToKeyID(CKeyID &hash) const
{
    if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160
                            && script[2] == 20 && script[23] == OP_EQUALVERIFY
                            && script[24] == OP_CHECKSIG) {
        memcpy(&hash, &script[3], 20);
        return true;
    }
    return false;
}

bool CScriptCompressor::IsToScriptID(CScriptID &hash) const
{
    if (script.size() == 23 && script[0] == OP_HASH160 && script[1] == 20
                            && script[22] == OP_EQUAL) {
        memcpy(&hash, &script[2], 20);
        return true;
    }
    return false;
}

bool CScriptCompressor::IsToPubKey(CPubKey &pubkey) const
{
    if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG
                            && (script[1] == 0x02 || script[1] == 0x03)) {
        pubkey.Set(&script[1], &script[34]);
        return true;
    }
    if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG
                            && script[1] == 0x04) {
        pubkey.Set(&script[1], &script[66]);
        return pubkey.IsFullyValid(); // if not fully valid, a case that would not be compressible
    }
    return false;
}

bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const
{
    CKeyID keyID;
    if (IsToKeyID(keyID)) {
        out.resize(21);
        out[0] = 0x00;
        memcpy(&out[1], &keyID, 20);
        return true;
    }
    CScriptID scriptID;
    if (IsToScriptID(scriptID)) {
        out.resize(21);
        out[0] = 0x01;
        memcpy(&out[1], &scriptID, 20);
        return true;
    }
    CPubKey pubkey;
    if (IsToPubKey(pubkey)) {
        out.resize(33);
        memcpy(&out[1], &pubkey[1], 32);
        if (pubkey[0] == 0x02 || pubkey[0] == 0x03) {
            out[0] = pubkey[0];
            return true;
        } else if (pubkey[0] == 0x04) {
            out[0] = 0x04 | (pubkey[64] & 0x01);
            return true;
        }
    }
    return false;
}

unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const
{
    if (nSize == 0 || nSize == 1)
        return 20;
    if (nSize == 2 || nSize == 3 || nSize == 4 || nSize == 5)
        return 32;
    return 0;
}

bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigned char> &in)
{
    switch(nSize) {
    case 0x00:
        script.resize(25);
        script[0] = OP_DUP;
        script[1] = OP_HASH160;
        script[2] = 20;
        memcpy(&script[3], &in[0], 20);
        script[23] = OP_EQUALVERIFY;
        script[24] = OP_CHECKSIG;
        return true;
    case 0x01:
        script.resize(23);
        script[0] = OP_HASH160;
        script[1] = 20;
        memcpy(&script[2], &in[0], 20);
        script[22] = OP_EQUAL;
        return true;
    case 0x02:
    case 0x03:
        script.resize(35);
        script[0] = 33;
        script[1] = nSize;
        memcpy(&script[2], &in[0], 32);
        script[34] = OP_CHECKSIG;
        return true;
    case 0x04:
    case 0x05:
        unsigned char vch[33] = {};
        vch[0] = nSize - 2;
        memcpy(&vch[1], &in[0], 32);
        CPubKey pubkey(&vch[0], &vch[33]);
        if (!pubkey.Decompress())
            return false;
        assert(pubkey.size() == 65);
        script.resize(67);
        script[0] = 65;
        memcpy(&script[1], pubkey.begin(), 65);
        script[66] = OP_CHECKSIG;
        return true;
    }
    return false;
}