hush3/src/zcash/Note.cpp

// Copyright (c) 2016-2023 The Hush developers
// Distributed under the GPLv3 software license, see the accompanying
// file COPYING or https://www.gnu.org/licenses/gpl-3.0.en.html

#include "Note.hpp"
#include "prf.h"
#include "crypto/sha256.h"

#include "random.h"
#include "version.h"
#include "streams.h"

#include "zcash/util.h"
#include "librustzcash.h"
#include <boost/thread.hpp>

using namespace libzcash;

// Construct and populate Sapling note for a given payment address and value.
SaplingNote::SaplingNote(const SaplingPaymentAddress& address, const uint64_t value) : BaseNote(value) {
    d = address.d;
    pk_d = address.pk_d;
    librustzcash_sapling_generate_r(r.begin());
}

// Call librustzcash to compute the commitment
boost::optional<uint256> SaplingNote::cm() const {
    uint256 result;
    if (!librustzcash_sapling_compute_cm(
            d.data(),
            pk_d.begin(),
            value(),
            r.begin(),
            result.begin()
        ))
    {
        return boost::none;
    }

    return result;
}

// Call librustzcash to compute the nullifier
boost::optional<uint256> SaplingNote::nullifier(const SaplingFullViewingKey& vk, const uint64_t position) const
{
    auto ak = vk.ak;
    auto nk = vk.nk;

    uint256 result;
    if (!librustzcash_sapling_compute_nf(
            d.data(),
            pk_d.begin(),
            value(),
            r.begin(),
            ak.begin(),
            nk.begin(),
            position,
            result.begin()
    ))
    {
        return boost::none;
    }

    return result;
}

// Construct and populate SaplingNotePlaintext for a given note and memo.
SaplingNotePlaintext::SaplingNotePlaintext(
    const SaplingNote& note,
    std::array<unsigned char, HUSH_MEMO_SIZE> memo) : BaseNotePlaintext(note, memo)
{
    d = note.d;
    rcm = note.r;
}


boost::optional<SaplingNote> SaplingNotePlaintext::note(const SaplingIncomingViewingKey& ivk) const
{
    auto addr = ivk.address(d);
    if (addr) {
        return SaplingNote(d, addr.get().pk_d, value_, rcm);
    } else {
        return boost::none;
    }
}

boost::optional<SaplingOutgoingPlaintext> SaplingOutgoingPlaintext::decrypt(
    const SaplingOutCiphertext &ciphertext,
    const uint256& ovk,
    const uint256& cv,
    const uint256& cm,
    const uint256& epk
)
{
    auto pt = AttemptSaplingOutDecryption(ciphertext, ovk, cv, cm, epk);
    if (!pt) {
        return boost::none;
    }

    // Deserialize from the plaintext
    try {
        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
        ss << pt.get();

        SaplingOutgoingPlaintext ret;
        ss >> ret;

        assert(ss.size() == 0);

        return ret;
    } catch (const boost::thread_interrupted&) {
        throw;
    } catch (...) {
        return boost::none;
    }
}

boost::optional<SaplingNotePlaintext> SaplingNotePlaintext::decrypt(
    const SaplingEncCiphertext &ciphertext,
    const uint256 &ivk,
    const uint256 &epk,
    const uint256 &cmu
)
{
    auto pt = AttemptSaplingEncDecryption(ciphertext, ivk, epk);
    if (!pt) {
        return boost::none;
    }

    // Deserialize from the plaintext
    SaplingNotePlaintext ret;
    try {
        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
        ss << pt.get();
        ss >> ret;
        assert(ss.size() == 0);
    } catch (const boost::thread_interrupted&) {
        throw;
    } catch (...) {
        return boost::none;
    }

    uint256 pk_d;
    if (!librustzcash_ivk_to_pkd(ivk.begin(), ret.d.data(), pk_d.begin())) {
        return boost::none;
    }

    uint256 cmu_expected;
    if (!librustzcash_sapling_compute_cm(
        ret.d.data(),
        pk_d.begin(),
        ret.value(),
        ret.rcm.begin(),
        cmu_expected.begin()
    ))
    {
        return boost::none;
    }

    if (cmu_expected != cmu) {
        return boost::none;
    }

    return ret;
}

boost::optional<SaplingNotePlaintext> SaplingNotePlaintext::decrypt(
    const SaplingEncCiphertext &ciphertext,
    const uint256 &epk,
    const uint256 &esk,
    const uint256 &pk_d,
    const uint256 &cmu
)
{
    auto pt = AttemptSaplingEncDecryption(ciphertext, epk, esk, pk_d);
    if (!pt) {
        return boost::none;
    }

    // Deserialize from the plaintext
    SaplingNotePlaintext ret;
    try {
        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
        ss << pt.get();
        ss >> ret;
        assert(ss.size() == 0);
    } catch (const boost::thread_interrupted&) {
        throw;
    } catch (...) {
        return boost::none;
    }

    uint256 cmu_expected;
    if (!librustzcash_sapling_compute_cm(
        ret.d.data(),
        pk_d.begin(),
        ret.value(),
        ret.rcm.begin(),
        cmu_expected.begin()
    ))
    {
        return boost::none;
    }

    if (cmu_expected != cmu) {
        return boost::none;
    }

    return ret;
}

boost::optional<SaplingNotePlaintextEncryptionResult> SaplingNotePlaintext::encrypt(const uint256& pk_d) const
{
    // Get the encryptor
    auto sne = SaplingNoteEncryption::FromDiversifier(d);
    if (!sne) {
        return boost::none;
    }
    auto enc = sne.get();

    // Create the plaintext
    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
    ss << (*this);
    SaplingEncPlaintext pt;
    assert(pt.size() == ss.size());
    memcpy(&pt[0], &ss[0], pt.size());

    // Encrypt the plaintext
    auto encciphertext = enc.encrypt_to_recipient(pk_d, pt);
    if (!encciphertext) {
        return boost::none;
    }
    return SaplingNotePlaintextEncryptionResult(encciphertext.get(), enc);
}

SaplingOutCiphertext SaplingOutgoingPlaintext::encrypt(
        const uint256& ovk,
        const uint256& cv,
        const uint256& cm,
        SaplingNoteEncryption& enc
    ) const
{
    // Create the plaintext
    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
    ss << (*this);
    SaplingOutPlaintext pt;
    assert(pt.size() == ss.size());
    memcpy(&pt[0], &ss[0], pt.size());

    return enc.encrypt_to_ourselves(ovk, cv, cm, pt);
}

boost::optional<SaplingNotePlaintext> SaplingNotePlaintext::attempt_sapling_enc_decryption_deserialization(
    const SaplingEncCiphertext &ciphertext,
    const uint256 &ivk,
    const uint256 &epk
)
{
    auto encPlaintext = AttemptSaplingEncDecryption(ciphertext, ivk, epk);

    if (!encPlaintext) {
        return boost::none;
    }

    // Deserialize from the plaintext
    SaplingNotePlaintext ret;
    try {
        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
        ss << encPlaintext.value();
        ss >> ret;
        assert(ss.size() == 0);
        return ret;
    } catch (const boost::thread_interrupted&) {
        throw;
    } catch (...) {
        return boost::none;
    }
}

boost::optional<SaplingNotePlaintext> SaplingNotePlaintext::plaintext_checks_without_height(
    const SaplingNotePlaintext &plaintext,
    const uint256 &ivk,
    const uint256 &epk,
    const uint256 &cmu
)
{
    uint256 pk_d;
    if (!librustzcash_ivk_to_pkd(ivk.begin(), plaintext.d.data(), pk_d.begin())) {
        return boost::none;
    }

    uint256 cmu_expected;
    uint256 rcm = plaintext.rcm();
    if (!librustzcash_sapling_compute_cmu(
        plaintext.d.data(),
        pk_d.begin(),
        plaintext.value(),
        rcm.begin(),
        cmu_expected.begin()
    ))
    {
        return boost::none;
    }

    if (cmu_expected != cmu) {
        return boost::none;
    }

    if (plaintext.get_leadbyte() != 0x01) {
        assert(plaintext.get_leadbyte() == 0x02);
        // ZIP 212: Check that epk is consistent to guard against linkability
        // attacks without relying on the soundness of the SNARK.
        uint256 expected_epk;
        uint256 esk = plaintext.generate_or_derive_esk();
        if (!librustzcash_sapling_ka_derivepublic(plaintext.d.data(), esk.begin(), expected_epk.begin())) {
            return boost::none;
        }
        if (expected_epk != epk) {
            return boost::none;
        }
    }

    return plaintext;
}