NFTokenMint.cpp

#include <xrpl/basics/Expected.h>
#include <xrpl/ledger/View.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/InnerObjectFormats.h>
#include <xrpl/protocol/Rate.h>
#include <xrpl/protocol/TxFlags.h>
#include <xrpl/tx/transactors/nft/NFTokenMint.h>
 
#include <boost/endian/conversion.hpp>
 
#include <array>
 
namespace xrpl {
 
static std::uint16_t
extractNFTokenFlagsFromTxFlags(std::uint32_t txFlags)
{
    return static_cast<std::uint16_t>(txFlags & 0x0000FFFF);
}
 
static bool
hasOfferFields(PreflightContext const& ctx)
{
    return ctx.tx.isFieldPresent(sfAmount) || ctx.tx.isFieldPresent(sfDestination) ||
        ctx.tx.isFieldPresent(sfExpiration);
}
 
bool
NFTokenMint::checkExtraFeatures(PreflightContext const& ctx)
{
    return ctx.rules.enabled(featureNFTokenMintOffer) || !hasOfferFields(ctx);
}
 
std::uint32_t
NFTokenMint::getFlagsMask(PreflightContext const& ctx)
{
    // Prior to fixRemoveNFTokenAutoTrustLine, transfer of an NFToken between
    // accounts allowed a TrustLine to be added to the issuer of that token
    // without explicit permission from that issuer.  This was enabled by
    // minting the NFToken with the tfTrustLine flag set.
    //
    // That capability could be used to attack the NFToken issuer.  It
    // would be possible for two accounts to trade the NFToken back and forth
    // building up any number of TrustLines on the issuer, increasing the
    // issuer's reserve without bound.
    //
    // The fixRemoveNFTokenAutoTrustLine amendment disables minting with the
    // tfTrustLine flag as a way to prevent the attack.  But until the
    // amendment passes we still need to keep the old behavior available.
    std::uint32_t const nfTokenMintMask = [&]() -> std::uint32_t {
        if (ctx.rules.enabled(fixRemoveNFTokenAutoTrustLine))
        {
            // if featureDynamicNFT enabled then new flag allowing mutable URI available
            return ctx.rules.enabled(featureDynamicNFT) ? tfNFTokenMintMask
                                                        : tfNFTokenMintMaskWithoutMutable;
        }
        return ctx.rules.enabled(featureDynamicNFT) ? tfNFTokenMintOldMaskWithMutable
                                                    : tfNFTokenMintOldMask;
    }();
 
    return nfTokenMintMask;
}
 
NotTEC
NFTokenMint::preflight(PreflightContext const& ctx)
{
    if (auto const f = ctx.tx[~sfTransferFee])
    {
        if (f > maxTransferFee)
            return temBAD_NFTOKEN_TRANSFER_FEE;
 
        // If a non-zero TransferFee is set then the tfTransferable flag
        // must also be set.
        if (f > 0u && !ctx.tx.isFlag(tfTransferable))
            return temMALFORMED;
    }
 
    // An issuer must only be set if the tx is executed by the minter
    if (auto iss = ctx.tx[~sfIssuer]; iss == ctx.tx[sfAccount])
        return temMALFORMED;
 
    if (auto uri = ctx.tx[~sfURI])
    {
        if (uri->empty() || uri->length() > maxTokenURILength)
            return temMALFORMED;
    }
 
    if (hasOfferFields(ctx))
    {
        // The Amount field must be present if either the Destination or
        // Expiration fields are present.
        if (!ctx.tx.isFieldPresent(sfAmount))
            return temMALFORMED;
 
        // Rely on the common code shared with NFTokenCreateOffer to
        // do the validation.  We pass tfSellNFToken as the transaction flags
        // because a Mint is only allowed to create a sell offer.
        if (NotTEC notTec = nft::tokenOfferCreatePreflight(
                ctx.tx[sfAccount],
                ctx.tx[sfAmount],
                ctx.tx[~sfDestination],
                ctx.tx[~sfExpiration],
                extractNFTokenFlagsFromTxFlags(ctx.tx.getFlags()),
                ctx.rules);
            !isTesSuccess(notTec))
        {
            return notTec;
        }
    }
 
    return tesSUCCESS;
}
 
uint256
NFTokenMint::createNFTokenID(
    std::uint16_t flags,
    std::uint16_t fee,
    AccountID const& issuer,
    nft::Taxon taxon,
    std::uint32_t tokenSeq)
{
    // An issuer may issue several NFTs with the same taxon; to ensure that NFTs
    // are spread across multiple pages we lightly mix the taxon up by using the
    // sequence (which is not under the issuer's direct control) as the seed for
    // a simple linear congruential generator.  cipheredTaxon() does this work.
    taxon = nft::cipheredTaxon(tokenSeq, taxon);
 
    // The values are packed inside a 32-byte buffer, so we need to make sure
    // that the endianess is fixed.
    flags = boost::endian::native_to_big(flags);
    fee = boost::endian::native_to_big(fee);
    taxon = nft::toTaxon(boost::endian::native_to_big(nft::toUInt32(taxon)));
    tokenSeq = boost::endian::native_to_big(tokenSeq);
 
    std::array<std::uint8_t, 32> buf{};
 
    auto ptr = buf.data();
 
    // This code is awkward but the idea is to pack these values into a single
    // 256-bit value that uniquely identifies this NFT.
    std::memcpy(ptr, &flags, sizeof(flags));
    ptr += sizeof(flags);
 
    std::memcpy(ptr, &fee, sizeof(fee));
    ptr += sizeof(fee);
 
    std::memcpy(ptr, issuer.data(), issuer.size());
    ptr += issuer.size();
 
    std::memcpy(ptr, &taxon, sizeof(taxon));
    ptr += sizeof(taxon);
 
    std::memcpy(ptr, &tokenSeq, sizeof(tokenSeq));
    ptr += sizeof(tokenSeq);
    XRPL_ASSERT(
        std::distance(buf.data(), ptr) == buf.size(),
        "xrpl::NFTokenMint::createNFTokenID : data size matches the buffer");
 
    return uint256::fromVoid(buf.data());
}
 
TER
NFTokenMint::preclaim(PreclaimContext const& ctx)
{
    // The issuer of the NFT may or may not be the account executing this
    // transaction. Check that and verify that this is allowed:
    if (auto issuer = ctx.tx[~sfIssuer])
    {
        auto const sle = ctx.view.read(keylet::account(*issuer));
 
        if (!sle)
            return tecNO_ISSUER;
 
        if (auto const minter = (*sle)[~sfNFTokenMinter]; minter != ctx.tx[sfAccount])
            return tecNO_PERMISSION;
    }
 
    if (ctx.tx.isFieldPresent(sfAmount))
    {
        // The Amount field says create an offer for the minted token.
        if (hasExpired(ctx.view, ctx.tx[~sfExpiration]))
            return tecEXPIRED;
 
        // Rely on the common code shared with NFTokenCreateOffer to
        // do the validation.  We pass tfSellNFToken as the transaction flags
        // because a Mint is only allowed to create a sell offer.
        if (TER const ter = nft::tokenOfferCreatePreclaim(
                ctx.view,
                ctx.tx[sfAccount],
                ctx.tx[~sfIssuer].value_or(ctx.tx[sfAccount]),
                ctx.tx[sfAmount],
                ctx.tx[~sfDestination],
                extractNFTokenFlagsFromTxFlags(ctx.tx.getFlags()),
                ctx.tx[~sfTransferFee].value_or(0),
                ctx.j);
            !isTesSuccess(ter))
            return ter;
    }
    return tesSUCCESS;
}
 
TER
NFTokenMint::doApply()
{
    auto const issuer = ctx_.tx[~sfIssuer].value_or(account_);
 
    auto const tokenSeq = [this, &issuer]() -> Expected<std::uint32_t, TER> {
        auto const root = view().peek(keylet::account(issuer));
        if (root == nullptr)
        {
            // Should not happen.  Checked in preclaim.
            return Unexpected(tecNO_ISSUER);
        }
 
        // If the issuer hasn't minted an NFToken before we must add a
        // FirstNFTokenSequence field to the issuer's AccountRoot.  The
        // value of the FirstNFTokenSequence must equal the issuer's
        // current account sequence.
        //
        // There are three situations:
        //  o If the first token is being minted by the issuer and
        //     * If the transaction consumes a Sequence number, then the
        //       Sequence has been pre-incremented by the time we get here in
        //       doApply.  We must decrement the value in the Sequence field.
        //     * Otherwise the transaction uses a Ticket so the Sequence has
        //       not been pre-incremented.  We use the Sequence value as is.
        //  o The first token is being minted by an authorized minter.  In
        //    this case the issuer's Sequence field has been left untouched.
        //    We use the issuer's Sequence value as is.
        if (!root->isFieldPresent(sfFirstNFTokenSequence))
        {
            std::uint32_t const acctSeq = root->at(sfSequence);
 
            root->at(sfFirstNFTokenSequence) =
                ctx_.tx.isFieldPresent(sfIssuer) || ctx_.tx.getSeqProxy().isTicket() ? acctSeq
                                                                                     : acctSeq - 1;
        }
 
        std::uint32_t const mintedNftCnt = (*root)[~sfMintedNFTokens].value_or(0u);
 
        (*root)[sfMintedNFTokens] = mintedNftCnt + 1u;
        if ((*root)[sfMintedNFTokens] == 0u)
            return Unexpected(tecMAX_SEQUENCE_REACHED);
 
        // Get the unique sequence number of this token by
        // sfFirstNFTokenSequence + sfMintedNFTokens
        std::uint32_t const offset = (*root)[sfFirstNFTokenSequence];
        std::uint32_t const tokenSeq = offset + mintedNftCnt;
 
        // Check for more overflow cases
        if (tokenSeq + 1u == 0u || tokenSeq < offset)
            return Unexpected(tecMAX_SEQUENCE_REACHED);
 
        ctx_.view().update(root);
        return tokenSeq;
    }();
 
    if (!tokenSeq.has_value())
        return (tokenSeq.error());
 
    std::uint32_t const ownerCountBefore =
        view().read(keylet::account(account_))->getFieldU32(sfOwnerCount);
 
    // Assemble the new NFToken.
    SOTemplate const* nfTokenTemplate =
        InnerObjectFormats::getInstance().findSOTemplateBySField(sfNFToken);
 
    if (nfTokenTemplate == nullptr)
    {
        // Should never happen.
        return tecINTERNAL;  // LCOV_EXCL_LINE
    }
 
    auto const nftokenID = createNFTokenID(
        extractNFTokenFlagsFromTxFlags(ctx_.tx.getFlags()),
        ctx_.tx[~sfTransferFee].value_or(0),
        issuer,
        nft::toTaxon(ctx_.tx[sfNFTokenTaxon]),
        tokenSeq.value());
 
    STObject newToken(*nfTokenTemplate, sfNFToken, [this, &nftokenID](STObject& object) {
        object.setFieldH256(sfNFTokenID, nftokenID);
 
        if (auto const uri = ctx_.tx[~sfURI])
            object.setFieldVL(sfURI, *uri);
    });
 
    if (TER const ret = nft::insertToken(ctx_.view(), account_, std::move(newToken));
        !isTesSuccess(ret))
        return ret;
 
    if (ctx_.tx.isFieldPresent(sfAmount))
    {
        // Rely on the common code shared with NFTokenCreateOffer to create
        // the offer.  We pass tfSellNFToken as the transaction flags
        // because a Mint is only allowed to create a sell offer.
        if (TER const ter = nft::tokenOfferCreateApply(
                view(),
                ctx_.tx[sfAccount],
                ctx_.tx[sfAmount],
                ctx_.tx[~sfDestination],
                ctx_.tx[~sfExpiration],
                ctx_.tx.getSeqProxy(),
                nftokenID,
                preFeeBalance_,
                j_);
            !isTesSuccess(ter))
            return ter;
    }
 
    // Only check the reserve if the owner count actually changed.  This
    // allows NFTs to be added to the page (and burn fees) without
    // requiring the reserve to be met each time.  The reserve is
    // only managed when a new NFT page or sell offer is added.
    if (auto const ownerCountAfter =
            view().read(keylet::account(account_))->getFieldU32(sfOwnerCount);
        ownerCountAfter > ownerCountBefore)
    {
        if (auto const reserve = view().fees().accountReserve(ownerCountAfter);
            preFeeBalance_ < reserve)
            return tecINSUFFICIENT_RESERVE;
    }
    return tesSUCCESS;
}
 
}  // namespace xrpl