standard.h

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_SCRIPT_STANDARD_H
#define BITCOIN_SCRIPT_STANDARD_H

#include <script/interpreter.h>
#include <uint256.h>

#include <string>
#include <variant>

static const bool DEFAULT_ACCEPT_DATACARRIER = true;

class CKeyID;
class CScript;
struct ScriptHash;

template<typename HashType>
class BaseHash
{
protected:
    HashType m_hash;

public:
    BaseHash() : m_hash() {}
    explicit BaseHash(const HashType& in) : m_hash(in) {}

    unsigned char* begin()
    {
        return m_hash.begin();
    }

    const unsigned char* begin() const
    {
        return m_hash.begin();
    }

    unsigned char* end()
    {
        return m_hash.end();
    }

    const unsigned char* end() const
    {
        return m_hash.end();
    }

    operator std::vector<unsigned char>() const
    {
        return std::vector<unsigned char>{m_hash.begin(), m_hash.end()};
    }

    std::string ToString() const
    {
        return m_hash.ToString();
    }

    bool operator==(const BaseHash<HashType>& other) const noexcept
    {
        return m_hash == other.m_hash;
    }

    bool operator!=(const BaseHash<HashType>& other) const noexcept
    {
        return !(m_hash == other.m_hash);
    }

    bool operator<(const BaseHash<HashType>& other) const noexcept
    {
        return m_hash < other.m_hash;
    }

    size_t size() const
    {
        return m_hash.size();
    }

    unsigned char* data() { return m_hash.data(); }
    const unsigned char* data() const { return m_hash.data(); }
};

/** A reference to a CScript: the Hash160 of its serialization (see script.h) */
class CScriptID : public BaseHash<uint160>
{
public:
    CScriptID() : BaseHash() {}
    explicit CScriptID(const CScript& in);
    explicit CScriptID(const uint160& in) : BaseHash(in) {}
    explicit CScriptID(const ScriptHash& in);
};

/**
 * Default setting for nMaxDatacarrierBytes. 80 bytes of data, +1 for OP_RETURN,
 * +2 for the pushdata opcodes.
 */
static const unsigned int MAX_OP_RETURN_RELAY = 83;

/**
 * A data carrying output is an unspendable output containing data. The script
 * type is designated as TxoutType::NULL_DATA.
 */
extern bool fAcceptDatacarrier;

/** Maximum size of TxoutType::NULL_DATA scripts that this node considers standard. */
extern unsigned nMaxDatacarrierBytes;

/**
 * Mandatory script verification flags that all new blocks must comply with for
 * them to be valid. (but old blocks may not comply with) Currently just P2SH,
 * but in the future other flags may be added.
 *
 * Failing one of these tests may trigger a DoS ban - see CheckInputScripts() for
 * details.
 */
static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;

enum class TxoutType {
    NONSTANDARD,
    // 'standard' transaction types:
    PUBKEY,
    PUBKEYHASH,
    SCRIPTHASH,
    MULTISIG,
    NULL_DATA, //!< unspendable OP_RETURN script that carries data
    WITNESS_V0_SCRIPTHASH,
    WITNESS_V0_KEYHASH,
    WITNESS_V1_TAPROOT,
    WITNESS_UNKNOWN, //!< Only for Witness versions not already defined above
};

class CNoDestination {
public:
    friend bool operator==(const CNoDestination &a, const CNoDestination &b) { return true; }
    friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
};

struct PKHash : public BaseHash<uint160>
{
    PKHash() : BaseHash() {}
    explicit PKHash(const uint160& hash) : BaseHash(hash) {}
    explicit PKHash(const CPubKey& pubkey);
    explicit PKHash(const CKeyID& pubkey_id);
};
CKeyID ToKeyID(const PKHash& key_hash);

struct WitnessV0KeyHash;
struct ScriptHash : public BaseHash<uint160>
{
    ScriptHash() : BaseHash() {}
    // These don't do what you'd expect.
    // Use ScriptHash(GetScriptForDestination(...)) instead.
    explicit ScriptHash(const WitnessV0KeyHash& hash) = delete;
    explicit ScriptHash(const PKHash& hash) = delete;

    explicit ScriptHash(const uint160& hash) : BaseHash(hash) {}
    explicit ScriptHash(const CScript& script);
    explicit ScriptHash(const CScriptID& script);
};

struct WitnessV0ScriptHash : public BaseHash<uint256>
{
    WitnessV0ScriptHash() : BaseHash() {}
    explicit WitnessV0ScriptHash(const uint256& hash) : BaseHash(hash) {}
    explicit WitnessV0ScriptHash(const CScript& script);
};

struct WitnessV0KeyHash : public BaseHash<uint160>
{
    WitnessV0KeyHash() : BaseHash() {}
    explicit WitnessV0KeyHash(const uint160& hash) : BaseHash(hash) {}
    explicit WitnessV0KeyHash(const CPubKey& pubkey);
    explicit WitnessV0KeyHash(const PKHash& pubkey_hash);
};
CKeyID ToKeyID(const WitnessV0KeyHash& key_hash);

//! CTxDestination subtype to encode any future Witness version
struct WitnessUnknown
{
    unsigned int version;
    unsigned int length;
    unsigned char program[40];

    friend bool operator==(const WitnessUnknown& w1, const WitnessUnknown& w2) {
        if (w1.version != w2.version) return false;
        if (w1.length != w2.length) return false;
        return std::equal(w1.program, w1.program + w1.length, w2.program);
    }

    friend bool operator<(const WitnessUnknown& w1, const WitnessUnknown& w2) {
        if (w1.version < w2.version) return true;
        if (w1.version > w2.version) return false;
        if (w1.length < w2.length) return true;
        if (w1.length > w2.length) return false;
        return std::lexicographical_compare(w1.program, w1.program + w1.length, w2.program, w2.program + w2.length);
    }
};

/**
 * A txout script template with a specific destination. It is either:
 *  * CNoDestination: no destination set
 *  * PKHash: TxoutType::PUBKEYHASH destination (P2PKH)
 *  * ScriptHash: TxoutType::SCRIPTHASH destination (P2SH)
 *  * WitnessV0ScriptHash: TxoutType::WITNESS_V0_SCRIPTHASH destination (P2WSH)
 *  * WitnessV0KeyHash: TxoutType::WITNESS_V0_KEYHASH destination (P2WPKH)
 *  * WitnessUnknown: TxoutType::WITNESS_UNKNOWN/WITNESS_V1_TAPROOT destination (P2W???)
 *    (taproot outputs do not require their own type as long as no wallet support exists)
 *  A CTxDestination is the internal data type encoded in a bitcoin address
 */
using CTxDestination = std::variant<CNoDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessUnknown>;

/** Check whether a CTxDestination is a CNoDestination. */
bool IsValidDestination(const CTxDestination& dest);

/** Get the name of a TxoutType as a string */
std::string GetTxnOutputType(TxoutType t);

/**
 * Parse a scriptPubKey and identify script type for standard scripts. If
 * successful, returns script type and parsed pubkeys or hashes, depending on
 * the type. For example, for a P2SH script, vSolutionsRet will contain the
 * script hash, for P2PKH it will contain the key hash, etc.
 *
 * @param[in]   scriptPubKey   Script to parse
 * @param[out]  vSolutionsRet  Vector of parsed pubkeys and hashes
 * @return                     The script type. TxoutType::NONSTANDARD represents a failed solve.
 */
TxoutType Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned char>>& vSolutionsRet);

/**
 * Parse a standard scriptPubKey for the destination address. Assigns result to
 * the addressRet parameter and returns true if successful. For multisig
 * scripts, instead use ExtractDestinations. Currently only works for P2PK,
 * P2PKH, P2SH, P2WPKH, and P2WSH scripts.
 */
bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);

/**
 * Parse a standard scriptPubKey with one or more destination addresses. For
 * multisig scripts, this populates the addressRet vector with the pubkey IDs
 * and nRequiredRet with the n required to spend. For other destinations,
 * addressRet is populated with a single value and nRequiredRet is set to 1.
 * Returns true if successful.
 *
 * Note: this function confuses destinations (a subset of CScripts that are
 * encodable as an address) with key identifiers (of keys involved in a
 * CScript), and its use should be phased out.
 */
bool ExtractDestinations(const CScript& scriptPubKey, TxoutType& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);

/**
 * Generate a Bitcoin scriptPubKey for the given CTxDestination. Returns a P2PKH
 * script for a CKeyID destination, a P2SH script for a CScriptID, and an empty
 * script for CNoDestination.
 */
CScript GetScriptForDestination(const CTxDestination& dest);

/** Generate a P2PK script for the given pubkey. */
CScript GetScriptForRawPubKey(const CPubKey& pubkey);

/** Generate a multisig script. */
CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys);

#endif // BITCOIN_SCRIPT_STANDARD_H