key.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-present The Bitcoin Core developers
// Copyright (c) 2017 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_KEY_H
#define BITCOIN_KEY_H
 
#include <attributes.h>
#include <pubkey.h>
#include <script/keyorigin.h>
#include <serialize.h>
#include <support/allocators/secure.h>
#include <support/cleanse.h>
#include <uint256.h>
 
#include <array>
#include <cassert>
#include <optional>
#include <span>
#include <stdexcept>
#include <utility>
#include <vector>
 
struct secp256k1_context_struct;
typedef struct secp256k1_context_struct secp256k1_context;
struct secp256k1_keypair;
 
typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;
 
inline constexpr size_t ECDH_SECRET_SIZE = CSHA256::OUTPUT_SIZE;
 
// Used to represent ECDH shared secret (ECDH_SECRET_SIZE bytes)
using ECDHSecret = std::array<std::byte, ECDH_SECRET_SIZE>;
 
class KeyPair;
 
class CKey
{
public:
    static constexpr unsigned int SIZE{279};
    static constexpr unsigned int COMPRESSED_SIZE{214};
    static_assert(
        SIZE >= COMPRESSED_SIZE,
        "COMPRESSED_SIZE is larger than SIZE");
 
private:
    using KeyType = std::array<unsigned char, 32>;
 
    bool fCompressed{false};
 
    secure_unique_ptr<KeyType> keydata;
 
    bool static Check(const unsigned char* vch);
 
    void MakeKeyData()
    {
        if (!keydata) keydata = make_secure_unique<KeyType>();
    }
 
    void ClearKeyData()
    {
        keydata.reset();
    }
 
public:
    CKey() noexcept = default;
    CKey(CKey&&) noexcept = default;
    CKey& operator=(CKey&&) noexcept = default;
 
    CKey& operator=(const CKey& other)
    {
        if (this != &other) {
            if (other.keydata) {
                MakeKeyData();
                *keydata = *other.keydata;
            } else {
                ClearKeyData();
            }
            fCompressed = other.fCompressed;
        }
        return *this;
    }
 
    CKey(const CKey& other) { *this = other; }
 
    friend bool operator==(const CKey& a, const CKey& b)
    {
        return a.fCompressed == b.fCompressed &&
            a.size() == b.size() &&
            memcmp(a.data(), b.data(), a.size()) == 0;
    }
 
    template <typename T>
    void Set(const T pbegin, const T pend, bool fCompressedIn)
    {
        if (size_t(pend - pbegin) != std::tuple_size_v<KeyType>) {
            ClearKeyData();
        } else if (Check(UCharCast(&pbegin[0]))) {
            MakeKeyData();
            memcpy(keydata->data(), (unsigned char*)&pbegin[0], keydata->size());
            fCompressed = fCompressedIn;
        } else {
            ClearKeyData();
        }
    }
 
    unsigned int size() const { return keydata ? keydata->size() : 0; }
    const std::byte* data() const { return keydata ? reinterpret_cast<const std::byte*>(keydata->data()) : nullptr; }
    const std::byte* begin() const { return data(); }
    const std::byte* end() const { return data() + size(); }
 
    bool IsValid() const { return !!keydata; }
 
    bool IsCompressed() const { return fCompressed; }
 
    void MakeNewKey(bool fCompressed);
 
    CPrivKey GetPrivKey() const;
 
    CPubKey GetPubKey() const;
 
    bool Sign(const uint256& hash, std::vector<unsigned char>& vchSig, bool grind = true, uint32_t test_case = 0) const;
 
    bool SignCompact(const uint256& hash, std::vector<unsigned char>& vchSig) const;
 
    bool SignSchnorr(const uint256& hash, std::span<unsigned char> sig, const uint256* merkle_root, const uint256& aux) const;
 
    [[nodiscard]] bool Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const;
 
    bool VerifyPubKey(const CPubKey& vchPubKey) const;
 
    bool Load(const CPrivKey& privkey, const CPubKey& vchPubKey, bool fSkipCheck);
 
    EllSwiftPubKey EllSwiftCreate(std::span<const std::byte> entropy) const;
 
    ECDHSecret ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift,
                                       const EllSwiftPubKey& our_ellswift,
                                       bool initiating) const;
    KeyPair ComputeKeyPair(const uint256* merkle_root) const;
};
 
CKey GenerateRandomKey(bool compressed = true) noexcept;
 
struct CExtKey {
    unsigned char nDepth;
    KeyFingerprint fingerprint;
    unsigned int nChild;
    ChainCode chaincode;
    CKey key;
 
    friend bool operator==(const CExtKey& a, const CExtKey& b)
    {
        return a.nDepth == b.nDepth &&
            a.fingerprint == b.fingerprint &&
            a.nChild == b.nChild &&
            a.chaincode == b.chaincode &&
            a.key == b.key;
    }
 
    CExtKey() = default;
    CExtKey(const CExtPubKey& xpub, const CKey& key_in) : nDepth(xpub.nDepth), fingerprint(xpub.fingerprint), nChild(xpub.nChild), chaincode(xpub.chaincode), key(key_in) {}
 
    KeyFingerprint id_key_fingerprint() const
    {
        return key.GetPubKey().GetID().fingerprint();
    }
 
    template <typename Stream>
    void Serialize(Stream& s) const
    {
        assert(key.size() == 32);
        s << nDepth << fingerprint << Using<BigEndianFormatter<4>>(nChild) << chaincode << uint8_t{0} << std::span{key.data(), key.size()};
    }
    template <typename Stream>
    void Unserialize(Stream& s)
    {
        uint8_t key_prefix;
        std::vector<unsigned char, secure_allocator<unsigned char>> ser_key(32);
        s >> nDepth >> fingerprint >> Using<BigEndianFormatter<4>>(nChild) >> chaincode >> key_prefix >> std::span{ser_key};
        key.Set(ser_key.begin(), ser_key.end(), true);
        if ((nDepth == 0 && (nChild != 0 || fingerprint != KeyFingerprint{})) || key_prefix != 0) key = CKey();
    }
    [[nodiscard]] bool Derive(CExtKey& out, unsigned int nChild) const;
    CExtPubKey Neuter() const;
    void SetSeed(std::span<const std::byte> seed);
};
 
std::optional<std::pair<CExtKey, KeyOriginInfo>> DeriveExtKey(const CExtKey& ext_key, const std::vector<uint32_t>& path);
 
class KeyPair
{
public:
    KeyPair() noexcept = default;
    KeyPair(KeyPair&&) noexcept = default;
    KeyPair& operator=(KeyPair&&) noexcept = default;
    KeyPair& operator=(const KeyPair& other)
    {
        if (this != &other) {
            if (other.m_keypair) {
                MakeKeyPairData();
                *m_keypair = *other.m_keypair;
            } else {
                ClearKeyPairData();
            }
        }
        return *this;
    }
 
    KeyPair(const KeyPair& other) { *this = other; }
 
    friend KeyPair CKey::ComputeKeyPair(const uint256* merkle_root) const;
    [[nodiscard]] bool SignSchnorr(const uint256& hash, std::span<unsigned char> sig, const uint256& aux) const;
 
    const secp256k1_keypair* GetSecpKeypair() const LIFETIMEBOUND
    {
        return IsValid() ? reinterpret_cast<const secp256k1_keypair*>(m_keypair->data()) : nullptr;
    }
 
    bool IsValid() const { return !!m_keypair; }
 
private:
    KeyPair(const CKey& key, const uint256* merkle_root);
 
    using KeyType = std::array<unsigned char, 96>;
    secure_unique_ptr<KeyType> m_keypair;
 
    void MakeKeyPairData()
    {
        if (!m_keypair) m_keypair = make_secure_unique<KeyType>();
    }
 
    void ClearKeyPairData()
    {
        m_keypair.reset();
    }
};
 
bool ECC_InitSanityCheck();
 
secp256k1_context* GetSecp256k1SignContext();
 
class ECC_Context
{
public:
    ECC_Context();
    ~ECC_Context();
};
 
#endif // BITCOIN_KEY_H