STTx.cpp

#include <xrpl/protocol/STTx.h>
 
#include <xrpl/basics/Blob.h>
#include <xrpl/basics/Slice.h>
#include <xrpl/basics/StringUtilities.h>
#include <xrpl/basics/base_uint.h>
#include <xrpl/basics/contract.h>
#include <xrpl/basics/safe_cast.h>
#include <xrpl/basics/strHex.h>
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/json/json_value.h>
#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/Batch.h>
#include <xrpl/protocol/HashPrefix.h>
#include <xrpl/protocol/MPTIssue.h>
#include <xrpl/protocol/Protocol.h>
#include <xrpl/protocol/PublicKey.h>
#include <xrpl/protocol/Rules.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/SOTemplate.h>
#include <xrpl/protocol/STAccount.h>
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STArray.h>
#include <xrpl/protocol/STBase.h>
#include <xrpl/protocol/STObject.h>
#include <xrpl/protocol/SecretKey.h>
#include <xrpl/protocol/SeqProxy.h>
#include <xrpl/protocol/Serializer.h>
#include <xrpl/protocol/Sign.h>
#include <xrpl/protocol/TxFlags.h>
#include <xrpl/protocol/TxFormats.h>
#include <xrpl/protocol/jss.h>
 
#include <boost/container/flat_set.hpp>
 
#include <array>
#include <cstddef>
#include <cstdint>
#include <exception>
#include <expected>
#include <format>
#include <functional>
#include <memory>
#include <optional>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
#include <vector>
 
namespace xrpl {
 
static auto
getTxFormat(TxType type)
{
    auto format = TxFormats::getInstance().findByType(type);
 
    if (format == nullptr)
    {
        Throw<std::runtime_error>(
            "Invalid transaction type " +
            std::to_string(safeCast<std::underlying_type_t<TxType>>(type)));
    }
 
    return format;
}
 
STTx::STTx(STObject&& object)
    : STObject(std::move(object)), txType_(safeCast<TxType>(getFieldU16(sfTransactionType)))
{
    applyTemplate(getTxFormat(txType_)->getSOTemplate());  //  may throw
    tid_ = getHash(HashPrefix::TransactionId);
    buildBatchTxns();
}
 
STTx::STTx(SerialIter& sit) : STObject(sfTransaction)
{
    int const length = sit.getBytesLeft();
 
    if ((length < kTxMinSizeBytes) || (length > kTxMaxSizeBytes))
        Throw<std::runtime_error>("Transaction length invalid");
 
    if (set(sit))
        Throw<std::runtime_error>("Transaction contains an object terminator");
 
    txType_ = safeCast<TxType>(getFieldU16(sfTransactionType));
 
    applyTemplate(getTxFormat(txType_)->getSOTemplate());  // May throw
    tid_ = getHash(HashPrefix::TransactionId);
    buildBatchTxns();
}
 
STTx::STTx(TxType type, std::function<void(STObject&)> assembler) : STObject(sfTransaction)
{
    auto format = getTxFormat(type);
 
    set(format->getSOTemplate());
    setFieldU16(sfTransactionType, format->getType());
 
    assembler(*this);
 
    // txType_ must be read after the object is assembled, so this cannot be a
    // member initializer.
    // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
    txType_ = safeCast<TxType>(getFieldU16(sfTransactionType));
 
    if (txType_ != type)
        logicError("Transaction type was mutated during assembly");
 
    tid_ = getHash(HashPrefix::TransactionId);
    buildBatchTxns();
}
 
STBase*
STTx::copy(std::size_t n, void* buf) const
{
    return emplace(n, buf, *this);
}
 
STBase*
STTx::move(std::size_t n, void* buf)
{
    return emplace(n, buf, std::move(*this));
}
 
// STObject functions.
SerializedTypeID
STTx::getSType() const
{
    return STI_TRANSACTION;
}
 
std::string
STTx::getFullText() const
{
    std::string ret = "\"";
    ret += to_string(getTransactionID());
    ret += "\" = {";
    ret += STObject::getFullText();
    ret += "}";
    return ret;
}
 
boost::container::flat_set<AccountID>
STTx::getMentionedAccounts() const
{
    boost::container::flat_set<AccountID> list;
 
    for (auto const& it : *this)
    {
        if (auto sacc = dynamic_cast<STAccount const*>(&it))
        {
            XRPL_ASSERT(!sacc->isDefault(), "xrpl::STTx::getMentionedAccounts : account is set");
            if (!sacc->isDefault())
                list.insert(sacc->value());
        }
        else if (auto samt = dynamic_cast<STAmount const*>(&it))
        {
            auto const& issuer = samt->getIssuer();
            if (!isXRP(issuer))
                list.insert(issuer);
        }
    }
 
    return list;
}
 
static Blob
getSigningData(STTx const& that)
{
    Serializer s;
    s.add32(HashPrefix::TxSign);
    that.addWithoutSigningFields(s);
    return s.getData();
}
 
uint256
STTx::getSigningHash() const
{
    return STObject::getSigningHash(HashPrefix::TxSign);
}
 
Blob
STTx::getSignature(STObject const& sigObject)
{
    try
    {
        return sigObject.getFieldVL(sfTxnSignature);
    }
    catch (std::exception const&)
    {
        return Blob();
    }
}
 
SeqProxy
STTx::getSeqProxy() const
{
    std::uint32_t const seq{getFieldU32(sfSequence)};
    if (seq != 0)
        return SeqProxy::rawSequence(seq);
 
    std::optional<std::uint32_t> const ticketSeq{at(~sfTicketSequence)};
    if (!ticketSeq)
    {
        // No TicketSequence specified.  Return the Sequence, whatever it is.
        return SeqProxy::rawSequence(seq);
    }
 
    return SeqProxy::rawTicket(*ticketSeq);
}
 
void
STTx::sign(
    PublicKey const& publicKey,
    SecretKey const& secretKey,
    std::optional<std::reference_wrapper<SField const>> signatureTarget)
{
    auto const data = getSigningData(*this);
 
    auto const sig = xrpl::sign(publicKey, secretKey, makeSlice(data));
 
    if (signatureTarget)
    {
        auto& target = peekFieldObject(*signatureTarget);
        target.setFieldVL(sfTxnSignature, sig);
    }
    else
    {
        setFieldVL(sfTxnSignature, sig);
    }
    tid_ = getHash(HashPrefix::TransactionId);
}
 
std::expected<void, std::string>
STTx::checkSign(Rules const& rules, STObject const& sigObject) const
{
    try
    {
        // Determine whether we're single- or multi-signing by looking
        // at the SigningPubKey.  If it's empty we must be
        // multi-signing.  Otherwise we're single-signing.
 
        Blob const& signingPubKey = sigObject.getFieldVL(sfSigningPubKey);
        return signingPubKey.empty() ? checkMultiSign(rules, sigObject)
                                     : checkSingleSign(sigObject);
    }
    catch (...)
    {
        return std::unexpected("Internal signature check failure.");
    }
}
 
std::expected<void, std::string>
STTx::checkSign(Rules const& rules) const
{
    if (auto const ret = checkSign(rules, *this); !ret)
        return ret;
 
    if (isFieldPresent(sfCounterpartySignature))
    {
        auto const counterSig = getFieldObject(sfCounterpartySignature);
        if (auto const ret = checkSign(rules, counterSig); !ret)
            return std::unexpected("Counterparty: " + ret.error());
    }
 
    if (isFieldPresent(sfSponsorSignature))
    {
        auto const sponsorSignatureObj = getFieldObject(sfSponsorSignature);
        if (auto const ret = checkSign(rules, sponsorSignatureObj); !ret)
            return std::unexpected("Sponsor: " + ret.error());
    }
 
    // Verify batch signer signatures here so they are cached with the rest
    // of signature checking.
    if (isFieldPresent(sfBatchSigners))
    {
        if (auto const ret = checkBatchSign(rules); !ret)
            return ret;
    }
    return {};
}
 
std::expected<void, std::string>
STTx::checkBatchSign(Rules const& rules) const
{
    try
    {
        if (getTxnType() != ttBATCH)
        {
            // LCOV_EXCL_START
            UNREACHABLE("STTx::checkBatchSign : not a batch transaction");
            return std::unexpected("Not a batch transaction.");
            // LCOV_EXCL_STOP
        }
        if (!isFieldPresent(sfBatchSigners))
            return std::unexpected("Missing BatchSigners field.");  // LCOV_EXCL_LINE
        STArray const& signers{getFieldArray(sfBatchSigners)};
        // Bound signature verification to the protocol cap. This runs in
        // checkValidity (via checkSign) at relay / submit time, BEFORE preflight
        // and passesLocalChecks enforce the cap. Without this guard a malicious
        // peer could put an oversized sfBatchSigners array in a 1 MB blob and
        // force one signature verification per entry before any of those checks
        // (or the fee charge) runs.
        if (signers.size() > kMaxBatchSigners)
            return std::unexpected("BatchSigners array exceeds max entries.");
        // Defensive.
        if (!batchTxns_)
        {
            // LCOV_EXCL_START
            UNREACHABLE("STTx::checkBatchSign : batch transactions not built");
            return std::unexpected("Missing inner transactions.");
            // LCOV_EXCL_STOP
        }
        auto const txIds = getBatchTransactionIDs();
        for (auto const& signer : signers)
        {
            Blob const& signingPubKey = signer.getFieldVL(sfSigningPubKey);
            auto const result = signingPubKey.empty() ? checkBatchMultiSign(signer, rules, txIds)
                                                      : checkBatchSingleSign(signer, txIds);
 
            if (!result)
                return result;
        }
        return {};
    }
    catch (std::exception const& e)
    {
        // LCOV_EXCL_START
        return std::unexpected(std::string("Internal batch signature check failure: ") + e.what());
        // LCOV_EXCL_STOP
    }
}
 
json::Value
STTx::getJson(JsonOptions options) const
{
    json::Value ret = STObject::getJson(JsonOptions::Values::None);
    if (!(options & JsonOptions::Values::DisableApiPriorV2))
        ret[jss::hash] = to_string(getTransactionID());
    return ret;
}
 
json::Value
STTx::getJson(JsonOptions options, bool binary) const
{
    bool const v1 = !(options & JsonOptions::Values::DisableApiPriorV2);
 
    if (binary)
    {
        Serializer const s = STObject::getSerializer();
        std::string const dataBin = strHex(s.peekData());
 
        if (v1)
        {
            json::Value ret(json::ValueType::Object);
            ret[jss::tx] = dataBin;
            ret[jss::hash] = to_string(getTransactionID());
            return ret;
        }
 
        return json::Value{dataBin};
    }
 
    json::Value ret = STObject::getJson(JsonOptions::Values::None);
    if (v1)
        ret[jss::hash] = to_string(getTransactionID());
 
    return ret;
}
 
std::string const&
STTx::getMetaSQLInsertReplaceHeader()
{
    static std::string const kSql =
        "INSERT OR REPLACE INTO Transactions "
        "(TransID, TransType, FromAcct, FromSeq, LedgerSeq, Status, RawTxn, "
        "TxnMeta)"
        " VALUES ";
 
    return kSql;
}
 
std::string
STTx::getMetaSQL(std::uint32_t inLedger, std::string const& escapedMetaData) const
{
    Serializer s;
    add(s);
    return getMetaSQL(s, inLedger, TxnSql::Validated, escapedMetaData);
}
 
// VFALCO This could be a free function elsewhere
std::string
STTx::getMetaSQL(
    Serializer rawTxn,
    std::uint32_t inLedger,
    TxnSql status,
    std::string const& escapedMetaData) const
{
    std::string rTxn = sqlBlobLiteral(rawTxn.peekData());
 
    auto format = TxFormats::getInstance().findByType(txType_);
    XRPL_ASSERT(format, "xrpl::STTx::getMetaSQL : non-null type format");
 
    return std::format(
        "('{}', '{}', '{}', '{}', '{}', '{}', {}, {})",
        to_string(getTransactionID()),
        format->getName(),
        toBase58(getAccountID(sfAccount)),
        getFieldU32(sfSequence),
        inLedger,
        safeCast<char>(status),
        rTxn,
        escapedMetaData);
}
 
static std::expected<void, std::string>
singleSignHelper(STObject const& sigObject, Slice const& data)
{
    // We don't allow both a non-empty sfSigningPubKey and an sfSigners.
    // That would allow the transaction to be signed two ways.  So if both
    // fields are present the signature is invalid.
    if (sigObject.isFieldPresent(sfSigners))
        return std::unexpected("Cannot both single- and multi-sign.");
 
    bool validSig = false;
    try
    {
        auto const spk = sigObject.getFieldVL(sfSigningPubKey);
        if (publicKeyType(makeSlice(spk)))
        {
            Blob const signature = sigObject.getFieldVL(sfTxnSignature);
            validSig = verify(PublicKey(makeSlice(spk)), data, makeSlice(signature));
        }
    }
    catch (std::exception const&)
    {
        validSig = false;
    }
 
    if (!validSig)
        return std::unexpected("Invalid signature.");
 
    return {};
}
 
std::expected<void, std::string>
STTx::checkSingleSign(STObject const& sigObject) const
{
    auto const data = getSigningData(*this);
    return singleSignHelper(sigObject, makeSlice(data));
}
 
std::expected<void, std::string>
STTx::checkBatchSingleSign(STObject const& batchSigner, std::vector<uint256> const& txIds) const
{
    XRPL_ASSERT(getTxnType() == ttBATCH, "STTx::checkBatchSingleSign : batch transaction");
    Serializer msg;
    serializeBatch(msg, getAccountID(sfAccount), getSeqProxy().value(), getFlags(), txIds);
    finishMultiSigningData(batchSigner.getAccountID(sfAccount), msg);
    return singleSignHelper(batchSigner, msg.slice());
}
 
std::expected<void, std::string>
multiSignHelper(
    STObject const& sigObject,
    std::optional<AccountID> txnAccountID,
    std::function<Serializer(AccountID const&)> makeMsg,
    Rules const& rules)
{
    // Make sure the MultiSigners are present.  Otherwise they are not
    // attempting multi-signing and we just have a bad SigningPubKey.
    if (!sigObject.isFieldPresent(sfSigners))
        return std::unexpected("Empty SigningPubKey.");
 
    // We don't allow both an sfSigners and an sfTxnSignature.  Both fields
    // being present would indicate that the transaction is signed both ways.
    if (sigObject.isFieldPresent(sfTxnSignature))
        return std::unexpected("Cannot both single- and multi-sign.");
 
    STArray const& signers{sigObject.getFieldArray(sfSigners)};
 
    // There are well known bounds that the number of signers must be within.
    if (signers.size() < STTx::kMinMultiSigners || signers.size() > STTx::kMaxMultiSigners)
        return std::unexpected("Invalid Signers array size.");
 
    // Signers must be in sorted order by AccountID.
    AccountID lastAccountID(beast::kZero);
 
    for (auto const& signer : signers)
    {
        auto const accountID = signer.getAccountID(sfAccount);
 
        // The account owner may not usually multisign for themselves.
        // If they can, txnAccountID will be unseated, which is not equal to any
        // value.
        if (txnAccountID == accountID)
            return std::unexpected("Invalid multisigner.");
 
        // No duplicate signers allowed.
        if (lastAccountID == accountID)
            return std::unexpected("Duplicate Signers not allowed.");
 
        // Accounts must be in order by account ID.  No duplicates allowed.
        if (lastAccountID > accountID)
            return std::unexpected("Unsorted Signers array.");
 
        // The next signature must be greater than this one.
        lastAccountID = accountID;
 
        // Verify the signature.
        bool validSig = false;
        std::optional<std::string> errorWhat;
        try
        {
            auto spk = signer.getFieldVL(sfSigningPubKey);
            if (publicKeyType(makeSlice(spk)))
            {
                Blob const signature = signer.getFieldVL(sfTxnSignature);
                validSig = verify(
                    PublicKey(makeSlice(spk)), makeMsg(accountID).slice(), makeSlice(signature));
            }
        }
        catch (std::exception const& e)
        {
            // We assume any problem lies with the signature.
            validSig = false;
            errorWhat = e.what();
        }
        if (!validSig)
        {
            return std::unexpected(
                std::string("Invalid signature on account ") + toBase58(accountID) +
                (errorWhat ? ": " + *errorWhat : "") + ".");
        }
    }
    // All signatures verified.
    return {};
}
 
std::expected<void, std::string>
STTx::checkBatchMultiSign(
    STObject const& batchSigner,
    Rules const& rules,
    std::vector<uint256> const& txIds) const
{
    XRPL_ASSERT(getTxnType() == ttBATCH, "STTx::checkBatchMultiSign : batch transaction");
    // We can ease the computational load inside the loop a bit by
    // pre-constructing part of the data that we hash.  Fill a Serializer
    // with the stuff that stays constant from signature to signature.
    auto const batchSignerAccount = batchSigner.getAccountID(sfAccount);
    Serializer dataStart;
    serializeBatch(dataStart, getAccountID(sfAccount), getSeqProxy().value(), getFlags(), txIds);
    dataStart.addBitString(batchSignerAccount);
    return multiSignHelper(
        batchSigner,
        batchSignerAccount,
        [&dataStart](AccountID const& accountID) -> Serializer {
            Serializer s = dataStart;
            finishMultiSigningData(accountID, s);
            return s;
        },
        rules);
}
 
std::expected<void, std::string>
STTx::checkMultiSign(Rules const& rules, STObject const& sigObject) const
{
    // Used inside the loop in multiSignHelper to enforce that
    // the account owner may not multisign for themselves.
    // For delegated transactions sfDelegate is the account whose signer list is checked,
    // the delegate account itself can not be among the signers.
    auto const txnAccountID =
        &sigObject != this ? std::nullopt : std::optional<AccountID>(getInitiator());
 
    // We can ease the computational load inside the loop a bit by
    // pre-constructing part of the data that we hash.  Fill a Serializer
    // with the stuff that stays constant from signature to signature.
    Serializer dataStart = startMultiSigningData(*this);
    return multiSignHelper(
        sigObject,
        txnAccountID,
        [&dataStart](AccountID const& accountID) -> Serializer {
            Serializer s = dataStart;
            finishMultiSigningData(accountID, s);
            return s;
        },
        rules);
}
 
void
STTx::buildBatchTxns()
{
    // Precondition: the template must have been applied first, so the fields
    // (including sfRawTransactions) are canonical before the inner txns are
    // hashed. The constructors call this immediately after applying the
    // template; isFree() being false confirms a template is set.
    XRPL_ASSERT(!isFree(), "STTx::buildBatchTxns : template applied");
    if (getTxnType() != ttBATCH)
        return;
    // A Batch always seats its inner transactions here, so every downstream
    // consumer can rely on them. sfRawTransactions is required by the format
    // (applyTemplate rejects a Batch without it); this guards a future change
    // that made it optional.
    if (!isFieldPresent(sfRawTransactions))
    {
        // LCOV_EXCL_START
        UNREACHABLE("STTx::buildBatchTxns : missing RawTransactions");
        Throw<std::runtime_error>("Batch has no RawTransactions.");
        // LCOV_EXCL_STOP
    }
 
    auto const& raw = getFieldArray(sfRawTransactions);
    if (raw.size() > kMaxBatchTxCount)
        Throw<std::runtime_error>("Batch has too many inner transactions.");
 
    // Build and validate each inner as an STTx once. A malformed inner throws;
    // a nested batch is rejected before building it (a batch cannot contain a
    // batch, and building one would recurse).
    auto& txns = batchTxns_.emplace();
    txns.reserve(raw.size());
    for (STObject const& rb : raw)
    {
        if (rb.getFieldU16(sfTransactionType) == ttBATCH)
            Throw<std::runtime_error>("Batch inner transaction cannot be a Batch.");
 
        txns.push_back(std::make_shared<STTx const>(STObject{rb}));
    }
}
 
std::vector<uint256>
STTx::getBatchTransactionIDs() const
{
    auto const& txns = getBatchTransactions();
    std::vector<uint256> ids;
    ids.reserve(txns.size());
    for (auto const& stx : txns)
        ids.push_back(stx->getTransactionID());
    return ids;
}
 
std::vector<std::shared_ptr<STTx const>> const&
STTx::getBatchTransactions() const
{
    XRPL_ASSERT(getTxnType() == ttBATCH, "STTx::getBatchTransactions : batch transaction");
    XRPL_ASSERT(batchTxns_.has_value(), "STTx::getBatchTransactions : batch transactions built");
    XRPL_ASSERT(
        batchTxns_->size() == getFieldArray(sfRawTransactions).size(),
        "STTx::getBatchTransactions : batch transactions size mismatch");
    return *batchTxns_;
}
 
AccountID
STTx::getInitiator() const
{
    // If sfDelegate is present, the delegate account is the initiator
    // note: if a delegate is specified, its authorization to act on behalf of the account is
    // enforced in `Transactor::invokeCheckPermission`
    // cryptographic signature validity is checked separately (e.g., in `Transactor::checkSign`)
    if (isFieldPresent(sfDelegate))
        return getAccountID(sfDelegate);
 
    // Default initiator
    return getAccountID(sfAccount);
}
 
AccountID
STTx::getFeePayerID() const
{
    if (isFieldPresent(sfSponsor) && ((getFieldU32(sfSponsorFlags) & spfSponsorFee) != 0u))
        return at(sfSponsor);
 
    return getInitiator();
}
 
//------------------------------------------------------------------------------
 
static bool
isMemoOkay(STObject const& st, std::string& reason)
{
    if (!st.isFieldPresent(sfMemos))
        return true;
 
    auto const& memos = st.getFieldArray(sfMemos);
 
    // The number 2048 is a preallocation hint, not a hard limit
    // to avoid allocate/copy/free's
    Serializer s(2048);
    memos.add(s);
 
    // FIXME move the memo limit into a config tunable
    if (s.getDataLength() > 1024)
    {
        reason = "The memo exceeds the maximum allowed size.";
        return false;
    }
 
    for (auto const& memo : memos)
    {
        auto memoObj = dynamic_cast<STObject const*>(&memo);
 
        if ((memoObj == nullptr) || (memoObj->getFName() != sfMemo))
        {
            reason = "A memo array may contain only Memo objects.";
            return false;
        }
 
        for (auto const& memoElement : *memoObj)
        {
            auto const& name = memoElement.getFName();
 
            if (name != sfMemoType && name != sfMemoData && name != sfMemoFormat)
            {
                reason =
                    "A memo may contain only MemoType, MemoData or "
                    "MemoFormat fields.";
                return false;
            }
 
            // The raw data is stored as hex-octets, which we want to decode.
            auto optData = strUnHex(memoElement.getText());
 
            if (!optData)
            {
                reason =
                    "The MemoType, MemoData and MemoFormat fields may "
                    "only contain hex-encoded data.";
                return false;
            }
 
            if (name == sfMemoData)
                continue;
 
            // The only allowed characters for MemoType and MemoFormat are the
            // characters allowed in URLs per RFC 3986: alphanumerics and the
            // following symbols: -._~:/?#[]@!$&'()*+,;=%
            static constexpr std::array<char, 256> const kAllowedSymbols = []() {
                std::array<char, 256> a{};
 
                std::string_view const symbols(
                    "0123456789"
                    "-._~:/?#[]@!$&'()*+,;=%"
                    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                    "abcdefghijklmnopqrstuvwxyz");
 
                for (unsigned char const c : symbols)
                    a[c] = 1;
                return a;
            }();
 
            for (unsigned char const c : *optData)
            {
                if (kAllowedSymbols[c] == 0)
                {
                    reason =
                        "The MemoType and MemoFormat fields may only "
                        "contain characters that are allowed in URLs "
                        "under RFC 3986.";
                    return false;
                }
            }
        }
    }
 
    return true;
}
 
// Ensure all account fields are 160-bits
static bool
isAccountFieldOkay(STObject const& st)
{
    for (int i = 0; i < st.getCount(); ++i)
    {
        auto t = dynamic_cast<STAccount const*>(st.peekAtPIndex(i));
        if ((t != nullptr) && t->isDefault())
            return false;
    }
 
    return true;
}
 
static bool
invalidMPTAmountInTx(STObject const& tx)
{
    auto const txType = tx[~sfTransactionType];
    if (!txType)
        return false;
    if (auto const* item = TxFormats::getInstance().findByType(safeCast<TxType>(*txType)))
    {
        for (auto const& e : item->getSOTemplate())
        {
            if (tx.isFieldPresent(e.sField()) && e.supportMPT() != SoeMptNone)
            {
                if (auto const& field = tx.peekAtField(e.sField());
                    (field.getSType() == STI_AMOUNT &&
                     safeDowncast<STAmount const&>(field).holds<MPTIssue>()) ||
                    (field.getSType() == STI_ISSUE &&
                     safeDowncast<STIssue const&>(field).holds<MPTIssue>()))
                {
                    if (e.supportMPT() != SoeMptSupported)
                        return true;
                }
            }
        }
    }
    return false;
}
 
static bool
isBatchRawTransactionOkay(STTx const& tx, std::string& reason)
{
    XRPL_ASSERT(
        tx.getTxnType() == ttBATCH || !tx.isFieldPresent(sfRawTransactions),
        "xrpl::isBatchRawTransactionOkay : raw transactions only on batch");
 
    if (tx.getTxnType() != ttBATCH)
        return true;
 
    if (!tx.isFieldPresent(sfRawTransactions))
    {
        // LCOV_EXCL_START
        reason = "Batch transactions must contain raw transactions.";
        return false;
        // LCOV_EXCL_STOP
    }
 
    if (tx.isFieldPresent(sfBatchSigners) &&
        tx.getFieldArray(sfBatchSigners).size() > kMaxBatchSigners)
    {
        reason = "BatchSigners array exceeds max entries.";
        return false;
    }
 
    // Inner structure (type, template, no nesting, count) is validated when the
    // batch STTx is constructed; here we only run each inner's local checks.
    for (auto const& inner : tx.getBatchTransactions())
    {
        if (!passesLocalChecks(*inner, reason))
            return false;
    }
    return true;
}
 
bool
passesLocalChecks(STTx const& tx, std::string& reason)
{
    if (!isMemoOkay(tx, reason))
        return false;
 
    if (!isAccountFieldOkay(tx))
    {
        reason = "An account field is invalid.";
        return false;
    }
 
    if (isPseudoTx(tx))
    {
        reason = "Cannot submit pseudo transactions.";
        return false;
    }
 
    if (invalidMPTAmountInTx(tx))
    {
        reason = "Amount can not be MPT.";
        return false;
    }
 
    if (!isBatchRawTransactionOkay(tx, reason))
        return false;
 
    return true;
}
 
std::shared_ptr<STTx const>
sterilize(STTx const& stx)
{
    Serializer s;
    stx.add(s);
    SerialIter sit(s.slice());
    return std::make_shared<STTx const>(std::ref(sit));
}
 
bool
isPseudoTx(STObject const& tx)
{
    auto const t = tx[~sfTransactionType];
 
    if (!t)
        return false;
 
    auto const tt = safeCast<TxType>(*t);
 
    return tt == ttAMENDMENT || tt == ttFEE || tt == ttUNL_MODIFY;
}
 
}  // namespace xrpl