InvariantCheck.cpp

//------------------------------------------------------------------------------
/*
  This file is part of rippled: https://github.com/ripple/rippled
  Copyright (c) 2012-2016 Ripple Labs Inc.
 
  Permission to use, copy, modify, and/or distribute this software for any
  purpose  with  or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.
 
  THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
  MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#include <xrpld/app/misc/AMMHelpers.h>
#include <xrpld/app/misc/AMMUtils.h>
#include <xrpld/app/tx/detail/InvariantCheck.h>
#include <xrpld/app/tx/detail/NFTokenUtils.h>
#include <xrpld/app/tx/detail/PermissionedDomainSet.h>
 
#include <xrpl/basics/Log.h>
#include <xrpl/ledger/CredentialHelpers.h>
#include <xrpl/ledger/ReadView.h>
#include <xrpl/ledger/View.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/STArray.h>
#include <xrpl/protocol/STNumber.h>
#include <xrpl/protocol/SystemParameters.h>
#include <xrpl/protocol/TxFormats.h>
#include <xrpl/protocol/Units.h>
#include <xrpl/protocol/nftPageMask.h>
 
namespace ripple {
 
/*
assert(enforce)
 
There are several asserts (or XRPL_ASSERTs) in this file that check a variable
named `enforce` when an invariant fails. At first glance, those asserts may look
incorrect, but they are not.
 
Those asserts take advantage of two facts:
1. `asserts` are not (normally) executed in release builds.
2. Invariants should *never* fail, except in tests that specifically modify
   the open ledger to break them.
 
This makes `assert(enforce)` sort of a second-layer of invariant enforcement
aimed at _developers_. It's designed to fire if a developer writes code that
violates an invariant, and runs it in unit tests or a develop build that _does
not have the relevant amendments enabled_. It's intentionally a pain in the neck
so that bad code gets caught and fixed as early as possible.
*/
 
enum Privilege {
    noPriv =
        0x0000,  // The transaction can not do any of the enumerated operations
    createAcct =
        0x0001,  // The transaction can create a new ACCOUNT_ROOT object.
    createPseudoAcct = 0x0002,  // The transaction can create a pseudo account,
                                // which implies createAcct
    mustDeleteAcct =
        0x0004,  // The transaction must delete an ACCOUNT_ROOT object
    mayDeleteAcct = 0x0008,    // The transaction may delete an ACCOUNT_ROOT
                               // object, but does not have to
    overrideFreeze = 0x0010,   // The transaction can override some freeze rules
    changeNFTCounts = 0x0020,  // The transaction can mint or burn an NFT
    createMPTIssuance =
        0x0040,  // The transaction can create a new MPT issuance
    destroyMPTIssuance = 0x0080,  // The transaction can destroy an MPT issuance
    mustAuthorizeMPT = 0x0100,  // The transaction MUST create or delete an MPT
                                // object (except by issuer)
    mayAuthorizeMPT = 0x0200,   // The transaction MAY create or delete an MPT
                                // object (except by issuer)
    mayDeleteMPT =
        0x0400,  // The transaction MAY delete an MPT object. May not create.
};
constexpr Privilege
operator|(Privilege lhs, Privilege rhs)
{
    return safe_cast<Privilege>(
        safe_cast<std::underlying_type_t<Privilege>>(lhs) |
        safe_cast<std::underlying_type_t<Privilege>>(rhs));
}
 
#pragma push_macro("TRANSACTION")
#undef TRANSACTION
 
#define TRANSACTION(tag, value, name, delegatable, amendment, privileges, ...) \
    case tag: {                                                                \
        return (privileges) & priv;                                            \
    }
 
bool
hasPrivilege(STTx const& tx, Privilege priv)
{
    switch (tx.getTxnType())
    {
#include <xrpl/protocol/detail/transactions.macro>
        // Deprecated types
        default:
            return false;
    }
};
 
#undef TRANSACTION
#pragma pop_macro("TRANSACTION")
 
void
TransactionFeeCheck::visitEntry(
    bool,
    std::shared_ptr<SLE const> const&,
    std::shared_ptr<SLE const> const&)
{
    // nothing to do
}
 
bool
TransactionFeeCheck::finalize(
    STTx const& tx,
    TER const,
    XRPAmount const fee,
    ReadView const&,
    beast::Journal const& j)
{
    // We should never charge a negative fee
    if (fee.drops() < 0)
    {
        JLOG(j.fatal()) << "Invariant failed: fee paid was negative: "
                        << fee.drops();
        return false;
    }
 
    // We should never charge a fee that's greater than or equal to the
    // entire XRP supply.
    if (fee >= INITIAL_XRP)
    {
        JLOG(j.fatal()) << "Invariant failed: fee paid exceeds system limit: "
                        << fee.drops();
        return false;
    }
 
    // We should never charge more for a transaction than the transaction
    // authorizes. It's possible to charge less in some circumstances.
    if (fee > tx.getFieldAmount(sfFee).xrp())
    {
        JLOG(j.fatal()) << "Invariant failed: fee paid is " << fee.drops()
                        << " exceeds fee specified in transaction.";
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
XRPNotCreated::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    /* We go through all modified ledger entries, looking only at account roots,
     * escrow payments, and payment channels. We remove from the total any
     * previous XRP values and add to the total any new XRP values. The net
     * balance of a payment channel is computed from two fields (amount and
     * balance) and deletions are ignored for paychan and escrow because the
     * amount fields have not been adjusted for those in the case of deletion.
     */
    if (before)
    {
        switch (before->getType())
        {
            case ltACCOUNT_ROOT:
                drops_ -= (*before)[sfBalance].xrp().drops();
                break;
            case ltPAYCHAN:
                drops_ -=
                    ((*before)[sfAmount] - (*before)[sfBalance]).xrp().drops();
                break;
            case ltESCROW:
                if (isXRP((*before)[sfAmount]))
                    drops_ -= (*before)[sfAmount].xrp().drops();
                break;
            default:
                break;
        }
    }
 
    if (after)
    {
        switch (after->getType())
        {
            case ltACCOUNT_ROOT:
                drops_ += (*after)[sfBalance].xrp().drops();
                break;
            case ltPAYCHAN:
                if (!isDelete)
                    drops_ += ((*after)[sfAmount] - (*after)[sfBalance])
                                  .xrp()
                                  .drops();
                break;
            case ltESCROW:
                if (!isDelete && isXRP((*after)[sfAmount]))
                    drops_ += (*after)[sfAmount].xrp().drops();
                break;
            default:
                break;
        }
    }
}
 
bool
XRPNotCreated::finalize(
    STTx const& tx,
    TER const,
    XRPAmount const fee,
    ReadView const&,
    beast::Journal const& j)
{
    // The net change should never be positive, as this would mean that the
    // transaction created XRP out of thin air. That's not possible.
    if (drops_ > 0)
    {
        JLOG(j.fatal()) << "Invariant failed: XRP net change was positive: "
                        << drops_;
        return false;
    }
 
    // The negative of the net change should be equal to actual fee charged.
    if (-drops_ != fee.drops())
    {
        JLOG(j.fatal()) << "Invariant failed: XRP net change of " << drops_
                        << " doesn't match fee " << fee.drops();
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
XRPBalanceChecks::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    auto isBad = [](STAmount const& balance) {
        if (!balance.native())
            return true;
 
        auto const drops = balance.xrp();
 
        // Can't have more than the number of drops instantiated
        // in the genesis ledger.
        if (drops > INITIAL_XRP)
            return true;
 
        // Can't have a negative balance (0 is OK)
        if (drops < XRPAmount{0})
            return true;
 
        return false;
    };
 
    if (before && before->getType() == ltACCOUNT_ROOT)
        bad_ |= isBad((*before)[sfBalance]);
 
    if (after && after->getType() == ltACCOUNT_ROOT)
        bad_ |= isBad((*after)[sfBalance]);
}
 
bool
XRPBalanceChecks::finalize(
    STTx const&,
    TER const,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    if (bad_)
    {
        JLOG(j.fatal()) << "Invariant failed: incorrect account XRP balance";
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
NoBadOffers::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    auto isBad = [](STAmount const& pays, STAmount const& gets) {
        // An offer should never be negative
        if (pays < beast::zero)
            return true;
 
        if (gets < beast::zero)
            return true;
 
        // Can't have an XRP to XRP offer:
        return pays.native() && gets.native();
    };
 
    if (before && before->getType() == ltOFFER)
        bad_ |= isBad((*before)[sfTakerPays], (*before)[sfTakerGets]);
 
    if (after && after->getType() == ltOFFER)
        bad_ |= isBad((*after)[sfTakerPays], (*after)[sfTakerGets]);
}
 
bool
NoBadOffers::finalize(
    STTx const&,
    TER const,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    if (bad_)
    {
        JLOG(j.fatal()) << "Invariant failed: offer with a bad amount";
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
NoZeroEscrow::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    auto isBad = [](STAmount const& amount) {
        // XRP case
        if (amount.native())
        {
            if (amount.xrp() <= XRPAmount{0})
                return true;
 
            if (amount.xrp() >= INITIAL_XRP)
                return true;
        }
        else
        {
            // IOU case
            if (amount.holds<Issue>())
            {
                if (amount <= beast::zero)
                    return true;
 
                if (badCurrency() == amount.getCurrency())
                    return true;
            }
 
            // MPT case
            if (amount.holds<MPTIssue>())
            {
                if (amount <= beast::zero)
                    return true;
 
                if (amount.mpt() > MPTAmount{maxMPTokenAmount})
                    return true;  // LCOV_EXCL_LINE
            }
        }
        return false;
    };
 
    if (before && before->getType() == ltESCROW)
        bad_ |= isBad((*before)[sfAmount]);
 
    if (after && after->getType() == ltESCROW)
        bad_ |= isBad((*after)[sfAmount]);
 
    auto checkAmount = [this](std::int64_t amount) {
        if (amount > maxMPTokenAmount || amount < 0)
            bad_ = true;
    };
 
    if (after && after->getType() == ltMPTOKEN_ISSUANCE)
    {
        auto const outstanding = (*after)[sfOutstandingAmount];
        checkAmount(outstanding);
        if (auto const locked = (*after)[~sfLockedAmount])
        {
            checkAmount(*locked);
            bad_ = outstanding < *locked;
        }
    }
 
    if (after && after->getType() == ltMPTOKEN)
    {
        auto const mptAmount = (*after)[sfMPTAmount];
        checkAmount(mptAmount);
        if (auto const locked = (*after)[~sfLockedAmount])
        {
            checkAmount(*locked);
        }
    }
}
 
bool
NoZeroEscrow::finalize(
    STTx const& txn,
    TER const,
    XRPAmount const,
    ReadView const& rv,
    beast::Journal const& j)
{
    if (bad_)
    {
        JLOG(j.fatal()) << "Invariant failed: escrow specifies invalid amount";
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
AccountRootsNotDeleted::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const&)
{
    if (isDelete && before && before->getType() == ltACCOUNT_ROOT)
        accountsDeleted_++;
}
 
bool
AccountRootsNotDeleted::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    // AMM account root can be deleted as the result of AMM withdraw/delete
    // transaction when the total AMM LP Tokens balance goes to 0.
    // A successful AccountDelete or AMMDelete MUST delete exactly
    // one account root.
    if (hasPrivilege(tx, mustDeleteAcct) && result == tesSUCCESS)
    {
        if (accountsDeleted_ == 1)
            return true;
 
        if (accountsDeleted_ == 0)
            JLOG(j.fatal()) << "Invariant failed: account deletion "
                               "succeeded without deleting an account";
        else
            JLOG(j.fatal()) << "Invariant failed: account deletion "
                               "succeeded but deleted multiple accounts!";
        return false;
    }
 
    // A successful AMMWithdraw/AMMClawback MAY delete one account root
    // when the total AMM LP Tokens balance goes to 0. Not every AMM withdraw
    // deletes the AMM account, accountsDeleted_ is set if it is deleted.
    if (hasPrivilege(tx, mayDeleteAcct) && result == tesSUCCESS &&
        accountsDeleted_ == 1)
        return true;
 
    if (accountsDeleted_ == 0)
        return true;
 
    JLOG(j.fatal()) << "Invariant failed: an account root was deleted";
    return false;
}
 
//------------------------------------------------------------------------------
 
void
AccountRootsDeletedClean::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const&)
{
    if (isDelete && before && before->getType() == ltACCOUNT_ROOT)
        accountsDeleted_.emplace_back(before);
}
 
bool
AccountRootsDeletedClean::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    // Always check for objects in the ledger, but to prevent differing
    // transaction processing results, however unlikely, only fail if the
    // feature is enabled. Enabled, or not, though, a fatal-level message will
    // be logged
    [[maybe_unused]] bool const enforce =
        view.rules().enabled(featureInvariantsV1_1) ||
        view.rules().enabled(featureSingleAssetVault);
 
    auto const objectExists = [&view, enforce, &j](auto const& keylet) {
        (void)enforce;
        if (auto const sle = view.read(keylet))
        {
            // Finding the object is bad
            auto const typeName = [&sle]() {
                auto item =
                    LedgerFormats::getInstance().findByType(sle->getType());
 
                if (item != nullptr)
                    return item->getName();
                return std::to_string(sle->getType());
            }();
 
            JLOG(j.fatal())
                << "Invariant failed: account deletion left behind a "
                << typeName << " object";
            // The comment above starting with "assert(enforce)" explains this
            // assert.
            XRPL_ASSERT(
                enforce,
                "ripple::AccountRootsDeletedClean::finalize::objectExists : "
                "account deletion left no objects behind");
            return true;
        }
        return false;
    };
 
    for (auto const& accountSLE : accountsDeleted_)
    {
        auto const accountID = accountSLE->getAccountID(sfAccount);
        // Simple types
        for (auto const& [keyletfunc, _, __] : directAccountKeylets)
        {
            if (objectExists(std::invoke(keyletfunc, accountID)) && enforce)
                return false;
        }
 
        {
            // NFT pages. ntfpage_min and nftpage_max were already explicitly
            // checked above as entries in directAccountKeylets. This uses
            // view.succ() to check for any NFT pages in between the two
            // endpoints.
            Keylet const first = keylet::nftpage_min(accountID);
            Keylet const last = keylet::nftpage_max(accountID);
 
            std::optional<uint256> key = view.succ(first.key, last.key.next());
 
            // current page
            if (key && objectExists(Keylet{ltNFTOKEN_PAGE, *key}) && enforce)
                return false;
        }
 
        // If the account is a pseudo account, then the linked object must
        // also be deleted. e.g. AMM, Vault, etc.
        for (auto const& field : getPseudoAccountFields())
        {
            if (accountSLE->isFieldPresent(*field))
            {
                auto const key = accountSLE->getFieldH256(*field);
                if (objectExists(keylet::unchecked(key)) && enforce)
                    return false;
            }
        }
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
LedgerEntryTypesMatch::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (before && after && before->getType() != after->getType())
        typeMismatch_ = true;
 
    if (after)
    {
#pragma push_macro("LEDGER_ENTRY")
#undef LEDGER_ENTRY
 
#define LEDGER_ENTRY(tag, ...) case tag:
 
        switch (after->getType())
        {
#include <xrpl/protocol/detail/ledger_entries.macro>
 
            break;
            default:
                invalidTypeAdded_ = true;
                break;
        }
 
#undef LEDGER_ENTRY
#pragma pop_macro("LEDGER_ENTRY")
    }
}
 
bool
LedgerEntryTypesMatch::finalize(
    STTx const&,
    TER const,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    if ((!typeMismatch_) && (!invalidTypeAdded_))
        return true;
 
    if (typeMismatch_)
    {
        JLOG(j.fatal()) << "Invariant failed: ledger entry type mismatch";
    }
 
    if (invalidTypeAdded_)
    {
        JLOG(j.fatal()) << "Invariant failed: invalid ledger entry type added";
    }
 
    return false;
}
 
//------------------------------------------------------------------------------
 
void
NoXRPTrustLines::visitEntry(
    bool,
    std::shared_ptr<SLE const> const&,
    std::shared_ptr<SLE const> const& after)
{
    if (after && after->getType() == ltRIPPLE_STATE)
    {
        // checking the issue directly here instead of
        // relying on .native() just in case native somehow
        // were systematically incorrect
        xrpTrustLine_ =
            after->getFieldAmount(sfLowLimit).issue() == xrpIssue() ||
            after->getFieldAmount(sfHighLimit).issue() == xrpIssue();
    }
}
 
bool
NoXRPTrustLines::finalize(
    STTx const&,
    TER const,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    if (!xrpTrustLine_)
        return true;
 
    JLOG(j.fatal()) << "Invariant failed: an XRP trust line was created";
    return false;
}
 
//------------------------------------------------------------------------------
 
void
NoDeepFreezeTrustLinesWithoutFreeze::visitEntry(
    bool,
    std::shared_ptr<SLE const> const&,
    std::shared_ptr<SLE const> const& after)
{
    if (after && after->getType() == ltRIPPLE_STATE)
    {
        std::uint32_t const uFlags = after->getFieldU32(sfFlags);
        bool const lowFreeze = uFlags & lsfLowFreeze;
        bool const lowDeepFreeze = uFlags & lsfLowDeepFreeze;
 
        bool const highFreeze = uFlags & lsfHighFreeze;
        bool const highDeepFreeze = uFlags & lsfHighDeepFreeze;
 
        deepFreezeWithoutFreeze_ =
            (lowDeepFreeze && !lowFreeze) || (highDeepFreeze && !highFreeze);
    }
}
 
bool
NoDeepFreezeTrustLinesWithoutFreeze::finalize(
    STTx const&,
    TER const,
    XRPAmount const,
    ReadView const&,
    beast::Journal const& j)
{
    if (!deepFreezeWithoutFreeze_)
        return true;
 
    JLOG(j.fatal()) << "Invariant failed: a trust line with deep freeze flag "
                       "without normal freeze was created";
    return false;
}
 
//------------------------------------------------------------------------------
 
void
TransfersNotFrozen::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    /*
     * A trust line freeze state alone doesn't determine if a transfer is
     * frozen. The transfer must be examined "end-to-end" because both sides of
     * the transfer may have different freeze states and freeze impact depends
     * on the transfer direction. This is why first we need to track the
     * transfers using IssuerChanges senders/receivers.
     *
     * Only in validateIssuerChanges, after we collected all changes can we
     * determine if the transfer is valid.
     */
    if (!isValidEntry(before, after))
    {
        return;
    }
 
    auto const balanceChange = calculateBalanceChange(before, after, isDelete);
    if (balanceChange.signum() == 0)
    {
        return;
    }
 
    recordBalanceChanges(after, balanceChange);
}
 
bool
TransfersNotFrozen::finalize(
    STTx const& tx,
    TER const ter,
    XRPAmount const fee,
    ReadView const& view,
    beast::Journal const& j)
{
    /*
     * We check this invariant regardless of deep freeze amendment status,
     * allowing for detection and logging of potential issues even when the
     * amendment is disabled.
     *
     * If an exploit that allows moving frozen assets is discovered,
     * we can alert operators who monitor fatal messages and trigger assert in
     * debug builds for an early warning.
     *
     * In an unlikely event that an exploit is found, this early detection
     * enables encouraging the UNL to expedite deep freeze amendment activation
     * or deploy hotfixes via new amendments. In case of a new amendment, we'd
     * only have to change this line setting 'enforce' variable.
     * enforce = view.rules().enabled(featureDeepFreeze) ||
     *           view.rules().enabled(fixFreezeExploit);
     */
    [[maybe_unused]] bool const enforce =
        view.rules().enabled(featureDeepFreeze);
 
    for (auto const& [issue, changes] : balanceChanges_)
    {
        auto const issuerSle = findIssuer(issue.account, view);
        // It should be impossible for the issuer to not be found, but check
        // just in case so rippled doesn't crash in release.
        if (!issuerSle)
        {
            // The comment above starting with "assert(enforce)" explains this
            // assert.
            XRPL_ASSERT(
                enforce,
                "ripple::TransfersNotFrozen::finalize : enforce "
                "invariant.");
            if (enforce)
            {
                return false;
            }
            continue;
        }
 
        if (!validateIssuerChanges(issuerSle, changes, tx, j, enforce))
        {
            return false;
        }
    }
 
    return true;
}
 
bool
TransfersNotFrozen::isValidEntry(
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    // `after` can never be null, even if the trust line is deleted.
    XRPL_ASSERT(
        after, "ripple::TransfersNotFrozen::isValidEntry : valid after.");
    if (!after)
    {
        return false;
    }
 
    if (after->getType() == ltACCOUNT_ROOT)
    {
        possibleIssuers_.emplace(after->at(sfAccount), after);
        return false;
    }
 
    /* While LedgerEntryTypesMatch invariant also checks types, all invariants
     * are processed regardless of previous failures.
     *
     * This type check is still necessary here because it prevents potential
     * issues in subsequent processing.
     */
    return after->getType() == ltRIPPLE_STATE &&
        (!before || before->getType() == ltRIPPLE_STATE);
}
 
STAmount
TransfersNotFrozen::calculateBalanceChange(
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after,
    bool isDelete)
{
    auto const getBalance = [](auto const& line, auto const& other, bool zero) {
        STAmount amt =
            line ? line->at(sfBalance) : other->at(sfBalance).zeroed();
        return zero ? amt.zeroed() : amt;
    };
 
    /* Trust lines can be created dynamically by other transactions such as
     * Payment and OfferCreate that cross offers. Such trust line won't be
     * created frozen, but the sender might be, so the starting balance must be
     * treated as zero.
     */
    auto const balanceBefore = getBalance(before, after, false);
 
    /* Same as above, trust lines can be dynamically deleted, and for frozen
     * trust lines, payments not involving the issuer must be blocked. This is
     * achieved by treating the final balance as zero when isDelete=true to
     * ensure frozen line restrictions are enforced even during deletion.
     */
    auto const balanceAfter = getBalance(after, before, isDelete);
 
    return balanceAfter - balanceBefore;
}
 
void
TransfersNotFrozen::recordBalance(Issue const& issue, BalanceChange change)
{
    XRPL_ASSERT(
        change.balanceChangeSign,
        "ripple::TransfersNotFrozen::recordBalance : valid trustline "
        "balance sign.");
    auto& changes = balanceChanges_[issue];
    if (change.balanceChangeSign < 0)
        changes.senders.emplace_back(std::move(change));
    else
        changes.receivers.emplace_back(std::move(change));
}
 
void
TransfersNotFrozen::recordBalanceChanges(
    std::shared_ptr<SLE const> const& after,
    STAmount const& balanceChange)
{
    auto const balanceChangeSign = balanceChange.signum();
    auto const currency = after->at(sfBalance).getCurrency();
 
    // Change from low account's perspective, which is trust line default
    recordBalance(
        {currency, after->at(sfHighLimit).getIssuer()},
        {after, balanceChangeSign});
 
    // Change from high account's perspective, which reverses the sign.
    recordBalance(
        {currency, after->at(sfLowLimit).getIssuer()},
        {after, -balanceChangeSign});
}
 
std::shared_ptr<SLE const>
TransfersNotFrozen::findIssuer(AccountID const& issuerID, ReadView const& view)
{
    if (auto it = possibleIssuers_.find(issuerID); it != possibleIssuers_.end())
    {
        return it->second;
    }
 
    return view.read(keylet::account(issuerID));
}
 
bool
TransfersNotFrozen::validateIssuerChanges(
    std::shared_ptr<SLE const> const& issuer,
    IssuerChanges const& changes,
    STTx const& tx,
    beast::Journal const& j,
    bool enforce)
{
    if (!issuer)
    {
        return false;
    }
 
    bool const globalFreeze = issuer->isFlag(lsfGlobalFreeze);
    if (changes.receivers.empty() || changes.senders.empty())
    {
        /* If there are no receivers, then the holder(s) are returning
         * their tokens to the issuer. Likewise, if there are no
         * senders, then the issuer is issuing tokens to the holder(s).
         * This is allowed regardless of the issuer's freeze flags. (The
         * holder may have contradicting freeze flags, but that will be
         * checked when the holder is treated as issuer.)
         */
        return true;
    }
 
    for (auto const& actors : {changes.senders, changes.receivers})
    {
        for (auto const& change : actors)
        {
            bool const high = change.line->at(sfLowLimit).getIssuer() ==
                issuer->at(sfAccount);
 
            if (!validateFrozenState(
                    change, high, tx, j, enforce, globalFreeze))
            {
                return false;
            }
        }
    }
    return true;
}
 
bool
TransfersNotFrozen::validateFrozenState(
    BalanceChange const& change,
    bool high,
    STTx const& tx,
    beast::Journal const& j,
    bool enforce,
    bool globalFreeze)
{
    bool const freeze = change.balanceChangeSign < 0 &&
        change.line->isFlag(high ? lsfLowFreeze : lsfHighFreeze);
    bool const deepFreeze =
        change.line->isFlag(high ? lsfLowDeepFreeze : lsfHighDeepFreeze);
    bool const frozen = globalFreeze || deepFreeze || freeze;
 
    bool const isAMMLine = change.line->isFlag(lsfAMMNode);
 
    if (!frozen)
    {
        return true;
    }
 
    // AMMClawbacks are allowed to override some freeze rules
    if ((!isAMMLine || globalFreeze) && hasPrivilege(tx, overrideFreeze))
    {
        JLOG(j.debug()) << "Invariant check allowing funds to be moved "
                        << (change.balanceChangeSign > 0 ? "to" : "from")
                        << " a frozen trustline for AMMClawback "
                        << tx.getTransactionID();
        return true;
    }
 
    JLOG(j.fatal()) << "Invariant failed: Attempting to move frozen funds for "
                    << tx.getTransactionID();
    // The comment above starting with "assert(enforce)" explains this assert.
    XRPL_ASSERT(
        enforce,
        "ripple::TransfersNotFrozen::validateFrozenState : enforce "
        "invariant.");
 
    if (enforce)
    {
        return false;
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
ValidNewAccountRoot::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (!before && after->getType() == ltACCOUNT_ROOT)
    {
        accountsCreated_++;
        accountSeq_ = (*after)[sfSequence];
        pseudoAccount_ = isPseudoAccount(after);
        flags_ = after->getFlags();
    }
}
 
bool
ValidNewAccountRoot::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    if (accountsCreated_ == 0)
        return true;
 
    if (accountsCreated_ > 1)
    {
        JLOG(j.fatal()) << "Invariant failed: multiple accounts "
                           "created in a single transaction";
        return false;
    }
 
    // From this point on we know exactly one account was created.
    if (hasPrivilege(tx, createAcct | createPseudoAcct) && result == tesSUCCESS)
    {
        bool const pseudoAccount =
            (pseudoAccount_ && view.rules().enabled(featureSingleAssetVault));
 
        if (pseudoAccount && !hasPrivilege(tx, createPseudoAcct))
        {
            JLOG(j.fatal()) << "Invariant failed: pseudo-account created by a "
                               "wrong transaction type";
            return false;
        }
 
        std::uint32_t const startingSeq =                     //
            pseudoAccount                                     //
            ? 0                                               //
            : view.rules().enabled(featureDeletableAccounts)  //
                ? view.seq()                                  //
                : 1;
 
        if (accountSeq_ != startingSeq)
        {
            JLOG(j.fatal()) << "Invariant failed: account created with "
                               "wrong starting sequence number";
            return false;
        }
 
        if (pseudoAccount)
        {
            std::uint32_t const expected =
                (lsfDisableMaster | lsfDefaultRipple | lsfDepositAuth);
            if (flags_ != expected)
            {
                JLOG(j.fatal())
                    << "Invariant failed: pseudo-account created with "
                       "wrong flags";
                return false;
            }
        }
 
        return true;
    }
 
    JLOG(j.fatal()) << "Invariant failed: account root created illegally";
    return false;
}  // namespace ripple
 
//------------------------------------------------------------------------------
 
void
ValidNFTokenPage::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    static constexpr uint256 const& pageBits = nft::pageMask;
    static constexpr uint256 const accountBits = ~pageBits;
 
    if ((before && before->getType() != ltNFTOKEN_PAGE) ||
        (after && after->getType() != ltNFTOKEN_PAGE))
        return;
 
    auto check = [this, isDelete](std::shared_ptr<SLE const> const& sle) {
        uint256 const account = sle->key() & accountBits;
        uint256 const hiLimit = sle->key() & pageBits;
        std::optional<uint256> const prev = (*sle)[~sfPreviousPageMin];
 
        // Make sure that any page links...
        //  1. Are properly associated with the owning account and
        //  2. The page is correctly ordered between links.
        if (prev)
        {
            if (account != (*prev & accountBits))
                badLink_ = true;
 
            if (hiLimit <= (*prev & pageBits))
                badLink_ = true;
        }
 
        if (auto const next = (*sle)[~sfNextPageMin])
        {
            if (account != (*next & accountBits))
                badLink_ = true;
 
            if (hiLimit >= (*next & pageBits))
                badLink_ = true;
        }
 
        {
            auto const& nftokens = sle->getFieldArray(sfNFTokens);
 
            // An NFTokenPage should never contain too many tokens or be empty.
            if (std::size_t const nftokenCount = nftokens.size();
                (!isDelete && nftokenCount == 0) ||
                nftokenCount > dirMaxTokensPerPage)
                invalidSize_ = true;
 
            // If prev is valid, use it to establish a lower bound for
            // page entries.  If prev is not valid the lower bound is zero.
            uint256 const loLimit =
                prev ? *prev & pageBits : uint256(beast::zero);
 
            // Also verify that all NFTokenIDs in the page are sorted.
            uint256 loCmp = loLimit;
            for (auto const& obj : nftokens)
            {
                uint256 const tokenID = obj[sfNFTokenID];
                if (!nft::compareTokens(loCmp, tokenID))
                    badSort_ = true;
                loCmp = tokenID;
 
                // None of the NFTs on this page should belong on lower or
                // higher pages.
                if (uint256 const tokenPageBits = tokenID & pageBits;
                    tokenPageBits < loLimit || tokenPageBits >= hiLimit)
                    badEntry_ = true;
 
                if (auto uri = obj[~sfURI]; uri && uri->empty())
                    badURI_ = true;
            }
        }
    };
 
    if (before)
    {
        check(before);
 
        // While an account's NFToken directory contains any NFTokens, the last
        // NFTokenPage (with 96 bits of 1 in the low part of the index) should
        // never be deleted.
        if (isDelete && (before->key() & nft::pageMask) == nft::pageMask &&
            before->isFieldPresent(sfPreviousPageMin))
        {
            deletedFinalPage_ = true;
        }
    }
 
    if (after)
        check(after);
 
    if (!isDelete && before && after)
    {
        // If the NFTokenPage
        //  1. Has a NextMinPage field in before, but loses it in after, and
        //  2. This is not the last page in the directory
        // Then we have identified a corruption in the links between the
        // NFToken pages in the NFToken directory.
        if ((before->key() & nft::pageMask) != nft::pageMask &&
            before->isFieldPresent(sfNextPageMin) &&
            !after->isFieldPresent(sfNextPageMin))
        {
            deletedLink_ = true;
        }
    }
}
 
bool
ValidNFTokenPage::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    if (badLink_)
    {
        JLOG(j.fatal()) << "Invariant failed: NFT page is improperly linked.";
        return false;
    }
 
    if (badEntry_)
    {
        JLOG(j.fatal()) << "Invariant failed: NFT found in incorrect page.";
        return false;
    }
 
    if (badSort_)
    {
        JLOG(j.fatal()) << "Invariant failed: NFTs on page are not sorted.";
        return false;
    }
 
    if (badURI_)
    {
        JLOG(j.fatal()) << "Invariant failed: NFT contains empty URI.";
        return false;
    }
 
    if (invalidSize_)
    {
        JLOG(j.fatal()) << "Invariant failed: NFT page has invalid size.";
        return false;
    }
 
    if (view.rules().enabled(fixNFTokenPageLinks))
    {
        if (deletedFinalPage_)
        {
            JLOG(j.fatal()) << "Invariant failed: Last NFT page deleted with "
                               "non-empty directory.";
            return false;
        }
        if (deletedLink_)
        {
            JLOG(j.fatal()) << "Invariant failed: Lost NextMinPage link.";
            return false;
        }
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
void
NFTokenCountTracking::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (before && before->getType() == ltACCOUNT_ROOT)
    {
        beforeMintedTotal += (*before)[~sfMintedNFTokens].value_or(0);
        beforeBurnedTotal += (*before)[~sfBurnedNFTokens].value_or(0);
    }
 
    if (after && after->getType() == ltACCOUNT_ROOT)
    {
        afterMintedTotal += (*after)[~sfMintedNFTokens].value_or(0);
        afterBurnedTotal += (*after)[~sfBurnedNFTokens].value_or(0);
    }
}
 
bool
NFTokenCountTracking::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    if (!hasPrivilege(tx, changeNFTCounts))
    {
        if (beforeMintedTotal != afterMintedTotal)
        {
            JLOG(j.fatal()) << "Invariant failed: the number of minted tokens "
                               "changed without a mint transaction!";
            return false;
        }
 
        if (beforeBurnedTotal != afterBurnedTotal)
        {
            JLOG(j.fatal()) << "Invariant failed: the number of burned tokens "
                               "changed without a burn transaction!";
            return false;
        }
 
        return true;
    }
 
    if (tx.getTxnType() == ttNFTOKEN_MINT)
    {
        if (result == tesSUCCESS && beforeMintedTotal >= afterMintedTotal)
        {
            JLOG(j.fatal())
                << "Invariant failed: successful minting didn't increase "
                   "the number of minted tokens.";
            return false;
        }
 
        if (result != tesSUCCESS && beforeMintedTotal != afterMintedTotal)
        {
            JLOG(j.fatal()) << "Invariant failed: failed minting changed the "
                               "number of minted tokens.";
            return false;
        }
 
        if (beforeBurnedTotal != afterBurnedTotal)
        {
            JLOG(j.fatal())
                << "Invariant failed: minting changed the number of "
                   "burned tokens.";
            return false;
        }
    }
 
    if (tx.getTxnType() == ttNFTOKEN_BURN)
    {
        if (result == tesSUCCESS)
        {
            if (beforeBurnedTotal >= afterBurnedTotal)
            {
                JLOG(j.fatal())
                    << "Invariant failed: successful burning didn't increase "
                       "the number of burned tokens.";
                return false;
            }
        }
 
        if (result != tesSUCCESS && beforeBurnedTotal != afterBurnedTotal)
        {
            JLOG(j.fatal()) << "Invariant failed: failed burning changed the "
                               "number of burned tokens.";
            return false;
        }
 
        if (beforeMintedTotal != afterMintedTotal)
        {
            JLOG(j.fatal())
                << "Invariant failed: burning changed the number of "
                   "minted tokens.";
            return false;
        }
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
ValidClawback::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const&)
{
    if (before && before->getType() == ltRIPPLE_STATE)
        trustlinesChanged++;
 
    if (before && before->getType() == ltMPTOKEN)
        mptokensChanged++;
}
 
bool
ValidClawback::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    if (tx.getTxnType() != ttCLAWBACK)
        return true;
 
    if (result == tesSUCCESS)
    {
        if (trustlinesChanged > 1)
        {
            JLOG(j.fatal())
                << "Invariant failed: more than one trustline changed.";
            return false;
        }
 
        if (mptokensChanged > 1)
        {
            JLOG(j.fatal())
                << "Invariant failed: more than one mptokens changed.";
            return false;
        }
 
        if (trustlinesChanged == 1)
        {
            AccountID const issuer = tx.getAccountID(sfAccount);
            STAmount const& amount = tx.getFieldAmount(sfAmount);
            AccountID const& holder = amount.getIssuer();
            STAmount const holderBalance = accountHolds(
                view, holder, amount.getCurrency(), issuer, fhIGNORE_FREEZE, j);
 
            if (holderBalance.signum() < 0)
            {
                JLOG(j.fatal())
                    << "Invariant failed: trustline balance is negative";
                return false;
            }
        }
    }
    else
    {
        if (trustlinesChanged != 0)
        {
            JLOG(j.fatal()) << "Invariant failed: some trustlines were changed "
                               "despite failure of the transaction.";
            return false;
        }
 
        if (mptokensChanged != 0)
        {
            JLOG(j.fatal()) << "Invariant failed: some mptokens were changed "
                               "despite failure of the transaction.";
            return false;
        }
    }
 
    return true;
}
 
//------------------------------------------------------------------------------
 
void
ValidMPTIssuance::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (after && after->getType() == ltMPTOKEN_ISSUANCE)
    {
        if (isDelete)
            mptIssuancesDeleted_++;
        else if (!before)
            mptIssuancesCreated_++;
    }
 
    if (after && after->getType() == ltMPTOKEN)
    {
        if (isDelete)
            mptokensDeleted_++;
        else if (!before)
            mptokensCreated_++;
    }
}
 
bool
ValidMPTIssuance::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const _fee,
    ReadView const& view,
    beast::Journal const& j)
{
    if (result == tesSUCCESS)
    {
        if (hasPrivilege(tx, createMPTIssuance))
        {
            if (mptIssuancesCreated_ == 0)
            {
                JLOG(j.fatal()) << "Invariant failed: transaction "
                                   "succeeded without creating a MPT issuance";
            }
            else if (mptIssuancesDeleted_ != 0)
            {
                JLOG(j.fatal()) << "Invariant failed: transaction "
                                   "succeeded while removing MPT issuances";
            }
            else if (mptIssuancesCreated_ > 1)
            {
                JLOG(j.fatal()) << "Invariant failed: transaction "
                                   "succeeded but created multiple issuances";
            }
 
            return mptIssuancesCreated_ == 1 && mptIssuancesDeleted_ == 0;
        }
 
        if (hasPrivilege(tx, destroyMPTIssuance))
        {
            if (mptIssuancesDeleted_ == 0)
            {
                JLOG(j.fatal()) << "Invariant failed: MPT issuance deletion "
                                   "succeeded without removing a MPT issuance";
            }
            else if (mptIssuancesCreated_ > 0)
            {
                JLOG(j.fatal()) << "Invariant failed: MPT issuance deletion "
                                   "succeeded while creating MPT issuances";
            }
            else if (mptIssuancesDeleted_ > 1)
            {
                JLOG(j.fatal()) << "Invariant failed: MPT issuance deletion "
                                   "succeeded but deleted multiple issuances";
            }
 
            return mptIssuancesCreated_ == 0 && mptIssuancesDeleted_ == 1;
        }
 
        // ttESCROW_FINISH may authorize an MPT, but it can't have the
        // mayAuthorizeMPT privilege, because that may cause
        // non-amendment-gated side effects.
        bool const enforceEscrowFinish = (tx.getTxnType() == ttESCROW_FINISH) &&
            (view.rules().enabled(featureSingleAssetVault)
             /*
               TODO: Uncomment when LendingProtocol is defined
               || view.rules().enabled(featureLendingProtocol)*/
            );
        if (hasPrivilege(tx, mustAuthorizeMPT | mayAuthorizeMPT) ||
            enforceEscrowFinish)
        {
            bool const submittedByIssuer = tx.isFieldPresent(sfHolder);
 
            if (mptIssuancesCreated_ > 0)
            {
                JLOG(j.fatal()) << "Invariant failed: MPT authorize "
                                   "succeeded but created MPT issuances";
                return false;
            }
            else if (mptIssuancesDeleted_ > 0)
            {
                JLOG(j.fatal()) << "Invariant failed: MPT authorize "
                                   "succeeded but deleted issuances";
                return false;
            }
            else if (
                submittedByIssuer &&
                (mptokensCreated_ > 0 || mptokensDeleted_ > 0))
            {
                JLOG(j.fatal())
                    << "Invariant failed: MPT authorize submitted by issuer "
                       "succeeded but created/deleted mptokens";
                return false;
            }
            else if (
                !submittedByIssuer && hasPrivilege(tx, mustAuthorizeMPT) &&
                (mptokensCreated_ + mptokensDeleted_ != 1))
            {
                // if the holder submitted this tx, then a mptoken must be
                // either created or deleted.
                JLOG(j.fatal())
                    << "Invariant failed: MPT authorize submitted by holder "
                       "succeeded but created/deleted bad number of mptokens";
                return false;
            }
 
            return true;
        }
        if (tx.getTxnType() == ttESCROW_FINISH)
        {
            // ttESCROW_FINISH may authorize an MPT, but it can't have the
            // mayAuthorizeMPT privilege, because that may cause
            // non-amendment-gated side effects.
            XRPL_ASSERT_PARTS(
                !enforceEscrowFinish,
                "ripple::ValidMPTIssuance::finalize",
                "not escrow finish tx");
            return true;
        }
 
        if (hasPrivilege(tx, mayDeleteMPT) && mptokensDeleted_ == 1 &&
            mptokensCreated_ == 0 && mptIssuancesCreated_ == 0 &&
            mptIssuancesDeleted_ == 0)
            return true;
    }
 
    if (mptIssuancesCreated_ != 0)
    {
        JLOG(j.fatal()) << "Invariant failed: a MPT issuance was created";
    }
    else if (mptIssuancesDeleted_ != 0)
    {
        JLOG(j.fatal()) << "Invariant failed: a MPT issuance was deleted";
    }
    else if (mptokensCreated_ != 0)
    {
        JLOG(j.fatal()) << "Invariant failed: a MPToken was created";
    }
    else if (mptokensDeleted_ != 0)
    {
        JLOG(j.fatal()) << "Invariant failed: a MPToken was deleted";
    }
 
    return mptIssuancesCreated_ == 0 && mptIssuancesDeleted_ == 0 &&
        mptokensCreated_ == 0 && mptokensDeleted_ == 0;
}
 
//------------------------------------------------------------------------------
 
void
ValidPermissionedDomain::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (before && before->getType() != ltPERMISSIONED_DOMAIN)
        return;
    if (after && after->getType() != ltPERMISSIONED_DOMAIN)
        return;
 
    auto check = [](SleStatus& sleStatus,
                    std::shared_ptr<SLE const> const& sle) {
        auto const& credentials = sle->getFieldArray(sfAcceptedCredentials);
        sleStatus.credentialsSize_ = credentials.size();
        auto const sorted = credentials::makeSorted(credentials);
        sleStatus.isUnique_ = !sorted.empty();
 
        // If array have duplicates then all the other checks are invalid
        sleStatus.isSorted_ = false;
 
        if (sleStatus.isUnique_)
        {
            unsigned i = 0;
            for (auto const& cred : sorted)
            {
                auto const& credTx = credentials[i++];
                sleStatus.isSorted_ = (cred.first == credTx[sfIssuer]) &&
                    (cred.second == credTx[sfCredentialType]);
                if (!sleStatus.isSorted_)
                    break;
            }
        }
    };
 
    if (before)
    {
        sleStatus_[0] = SleStatus();
        check(*sleStatus_[0], after);
    }
 
    if (after)
    {
        sleStatus_[1] = SleStatus();
        check(*sleStatus_[1], after);
    }
}
 
bool
ValidPermissionedDomain::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    if (tx.getTxnType() != ttPERMISSIONED_DOMAIN_SET || result != tesSUCCESS)
        return true;
 
    auto check = [](SleStatus const& sleStatus, beast::Journal const& j) {
        if (!sleStatus.credentialsSize_)
        {
            JLOG(j.fatal()) << "Invariant failed: permissioned domain with "
                               "no rules.";
            return false;
        }
 
        if (sleStatus.credentialsSize_ >
            maxPermissionedDomainCredentialsArraySize)
        {
            JLOG(j.fatal()) << "Invariant failed: permissioned domain bad "
                               "credentials size "
                            << sleStatus.credentialsSize_;
            return false;
        }
 
        if (!sleStatus.isUnique_)
        {
            JLOG(j.fatal())
                << "Invariant failed: permissioned domain credentials "
                   "aren't unique";
            return false;
        }
 
        if (!sleStatus.isSorted_)
        {
            JLOG(j.fatal())
                << "Invariant failed: permissioned domain credentials "
                   "aren't sorted";
            return false;
        }
 
        return true;
    };
 
    return (sleStatus_[0] ? check(*sleStatus_[0], j) : true) &&
        (sleStatus_[1] ? check(*sleStatus_[1], j) : true);
}
 
//------------------------------------------------------------------------------
 
void
ValidPseudoAccounts::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (isDelete)
        // Deletion is ignored
        return;
 
    if (after && after->getType() == ltACCOUNT_ROOT)
    {
        bool const isPseudo = [&]() {
            // isPseudoAccount checks that any of the pseudo-account fields are
            // set.
            if (isPseudoAccount(after))
                return true;
            // Not all pseudo-accounts have a zero sequence, but all accounts
            // with a zero sequence had better be pseudo-accounts.
            if (after->at(sfSequence) == 0)
                return true;
 
            return false;
        }();
        if (isPseudo)
        {
            // Pseudo accounts must have the following properties:
            // 1. Exactly one of the pseudo-account fields is set.
            // 2. The sequence number is not changed.
            // 3. The lsfDisableMaster, lsfDefaultRipple, and lsfDepositAuth
            // flags are set.
            // 4. The RegularKey is not set.
            {
                std::vector<SField const*> const& fields =
                    getPseudoAccountFields();
 
                auto const numFields = std::count_if(
                    fields.begin(),
                    fields.end(),
                    [&after](SField const* sf) -> bool {
                        return after->isFieldPresent(*sf);
                    });
                if (numFields != 1)
                {
                    std::stringstream error;
                    error << "pseudo-account has " << numFields
                          << " pseudo-account fields set";
                    errors_.emplace_back(error.str());
                }
            }
            if (before && before->at(sfSequence) != after->at(sfSequence))
            {
                errors_.emplace_back("pseudo-account sequence changed");
            }
            if (!after->isFlag(
                    lsfDisableMaster | lsfDefaultRipple | lsfDepositAuth))
            {
                errors_.emplace_back("pseudo-account flags are not set");
            }
            if (after->isFieldPresent(sfRegularKey))
            {
                errors_.emplace_back("pseudo-account has a regular key");
            }
        }
    }
}
 
bool
ValidPseudoAccounts::finalize(
    STTx const& tx,
    TER const,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    bool const enforce = view.rules().enabled(featureSingleAssetVault);
 
    // The comment above starting with "assert(enforce)" explains this assert.
    XRPL_ASSERT(
        errors_.empty() || enforce,
        "ripple::ValidPseudoAccounts::finalize : no bad "
        "changes or enforce invariant");
    if (!errors_.empty())
    {
        for (auto const& error : errors_)
        {
            JLOG(j.fatal()) << "Invariant failed: " << error;
        }
        if (enforce)
            return false;
    }
    return true;
}
 
//------------------------------------------------------------------------------
 
void
ValidPermissionedDEX::visitEntry(
    bool,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (after && after->getType() == ltDIR_NODE)
    {
        if (after->isFieldPresent(sfDomainID))
            domains_.insert(after->getFieldH256(sfDomainID));
    }
 
    if (after && after->getType() == ltOFFER)
    {
        if (after->isFieldPresent(sfDomainID))
            domains_.insert(after->getFieldH256(sfDomainID));
        else
            regularOffers_ = true;
 
        // if a hybrid offer is missing domain or additional book, there's
        // something wrong
        if (after->isFlag(lsfHybrid) &&
            (!after->isFieldPresent(sfDomainID) ||
             !after->isFieldPresent(sfAdditionalBooks) ||
             after->getFieldArray(sfAdditionalBooks).size() > 1))
            badHybrids_ = true;
    }
}
 
bool
ValidPermissionedDEX::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    auto const txType = tx.getTxnType();
    if ((txType != ttPAYMENT && txType != ttOFFER_CREATE) ||
        result != tesSUCCESS)
        return true;
 
    // For each offercreate transaction, check if
    // permissioned offers are valid
    if (txType == ttOFFER_CREATE && badHybrids_)
    {
        JLOG(j.fatal()) << "Invariant failed: hybrid offer is malformed";
        return false;
    }
 
    if (!tx.isFieldPresent(sfDomainID))
        return true;
 
    auto const domain = tx.getFieldH256(sfDomainID);
 
    if (!view.exists(keylet::permissionedDomain(domain)))
    {
        JLOG(j.fatal()) << "Invariant failed: domain doesn't exist";
        return false;
    }
 
    // for both payment and offercreate, there shouldn't be another domain
    // that's different from the domain specified
    for (auto const& d : domains_)
    {
        if (d != domain)
        {
            JLOG(j.fatal()) << "Invariant failed: transaction"
                               " consumed wrong domains";
            return false;
        }
    }
 
    if (regularOffers_)
    {
        JLOG(j.fatal()) << "Invariant failed: domain transaction"
                           " affected regular offers";
        return false;
    }
 
    return true;
}
 
void
ValidAMM::visitEntry(
    bool isDelete,
    std::shared_ptr<SLE const> const& before,
    std::shared_ptr<SLE const> const& after)
{
    if (isDelete)
        return;
 
    if (after)
    {
        auto const type = after->getType();
        // AMM object changed
        if (type == ltAMM)
        {
            ammAccount_ = after->getAccountID(sfAccount);
            lptAMMBalanceAfter_ = after->getFieldAmount(sfLPTokenBalance);
        }
        // AMM pool changed
        else if (
            (type == ltRIPPLE_STATE && after->getFlags() & lsfAMMNode) ||
            (type == ltACCOUNT_ROOT && after->isFieldPresent(sfAMMID)))
        {
            ammPoolChanged_ = true;
        }
    }
 
    if (before)
    {
        // AMM object changed
        if (before->getType() == ltAMM)
        {
            lptAMMBalanceBefore_ = before->getFieldAmount(sfLPTokenBalance);
        }
    }
}
 
static bool
validBalances(
    STAmount const& amount,
    STAmount const& amount2,
    STAmount const& lptAMMBalance,
    ValidAMM::ZeroAllowed zeroAllowed)
{
    bool const positive = amount > beast::zero && amount2 > beast::zero &&
        lptAMMBalance > beast::zero;
    if (zeroAllowed == ValidAMM::ZeroAllowed::Yes)
        return positive ||
            (amount == beast::zero && amount2 == beast::zero &&
             lptAMMBalance == beast::zero);
    return positive;
}
 
bool
ValidAMM::finalizeVote(bool enforce, beast::Journal const& j) const
{
    if (lptAMMBalanceAfter_ != lptAMMBalanceBefore_ || ammPoolChanged_)
    {
        // LPTokens and the pool can not change on vote
        // LCOV_EXCL_START
        JLOG(j.error()) << "AMMVote invariant failed: "
                        << lptAMMBalanceBefore_.value_or(STAmount{}) << " "
                        << lptAMMBalanceAfter_.value_or(STAmount{}) << " "
                        << ammPoolChanged_;
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
 
    return true;
}
 
bool
ValidAMM::finalizeBid(bool enforce, beast::Journal const& j) const
{
    if (ammPoolChanged_)
    {
        // The pool can not change on bid
        // LCOV_EXCL_START
        JLOG(j.error()) << "AMMBid invariant failed: pool changed";
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
    // LPTokens are burnt, therefore there should be fewer LPTokens
    else if (
        lptAMMBalanceBefore_ && lptAMMBalanceAfter_ &&
        (*lptAMMBalanceAfter_ > *lptAMMBalanceBefore_ ||
         *lptAMMBalanceAfter_ <= beast::zero))
    {
        // LCOV_EXCL_START
        JLOG(j.error()) << "AMMBid invariant failed: " << *lptAMMBalanceBefore_
                        << " " << *lptAMMBalanceAfter_;
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
 
    return true;
}
 
bool
ValidAMM::finalizeCreate(
    STTx const& tx,
    ReadView const& view,
    bool enforce,
    beast::Journal const& j) const
{
    if (!ammAccount_)
    {
        // LCOV_EXCL_START
        JLOG(j.error())
            << "AMMCreate invariant failed: AMM object is not created";
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
    else
    {
        auto const [amount, amount2] = ammPoolHolds(
            view,
            *ammAccount_,
            tx[sfAmount].get<Issue>(),
            tx[sfAmount2].get<Issue>(),
            fhIGNORE_FREEZE,
            j);
        // Create invariant:
        // sqrt(amount * amount2) == LPTokens
        // all balances are greater than zero
        if (!validBalances(
                amount, amount2, *lptAMMBalanceAfter_, ZeroAllowed::No) ||
            ammLPTokens(amount, amount2, lptAMMBalanceAfter_->issue()) !=
                *lptAMMBalanceAfter_)
        {
            JLOG(j.error()) << "AMMCreate invariant failed: " << amount << " "
                            << amount2 << " " << *lptAMMBalanceAfter_;
            if (enforce)
                return false;
        }
    }
 
    return true;
}
 
bool
ValidAMM::finalizeDelete(bool enforce, TER res, beast::Journal const& j) const
{
    if (ammAccount_)
    {
        // LCOV_EXCL_START
        std::string const msg = (res == tesSUCCESS)
            ? "AMM object is not deleted on tesSUCCESS"
            : "AMM object is changed on tecINCOMPLETE";
        JLOG(j.error()) << "AMMDelete invariant failed: " << msg;
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
 
    return true;
}
 
bool
ValidAMM::finalizeDEX(bool enforce, beast::Journal const& j) const
{
    if (ammAccount_)
    {
        // LCOV_EXCL_START
        JLOG(j.error()) << "AMM swap invariant failed: AMM object changed";
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
 
    return true;
}
 
bool
ValidAMM::generalInvariant(
    ripple::STTx const& tx,
    ripple::ReadView const& view,
    ZeroAllowed zeroAllowed,
    beast::Journal const& j) const
{
    auto const [amount, amount2] = ammPoolHolds(
        view,
        *ammAccount_,
        tx[sfAsset].get<Issue>(),
        tx[sfAsset2].get<Issue>(),
        fhIGNORE_FREEZE,
        j);
    // Deposit and Withdrawal invariant:
    // sqrt(amount * amount2) >= LPTokens
    // all balances are greater than zero
    // unless on last withdrawal
    auto const poolProductMean = root2(amount * amount2);
    bool const nonNegativeBalances =
        validBalances(amount, amount2, *lptAMMBalanceAfter_, zeroAllowed);
    bool const strongInvariantCheck = poolProductMean >= *lptAMMBalanceAfter_;
    // Allow for a small relative error if strongInvariantCheck fails
    auto weakInvariantCheck = [&]() {
        return *lptAMMBalanceAfter_ != beast::zero &&
            withinRelativeDistance(
                poolProductMean, Number{*lptAMMBalanceAfter_}, Number{1, -11});
    };
    if (!nonNegativeBalances ||
        (!strongInvariantCheck && !weakInvariantCheck()))
    {
        JLOG(j.error()) << "AMM " << tx.getTxnType() << " invariant failed: "
                        << tx.getHash(HashPrefix::transactionID) << " "
                        << ammPoolChanged_ << " " << amount << " " << amount2
                        << " " << poolProductMean << " "
                        << lptAMMBalanceAfter_->getText() << " "
                        << ((*lptAMMBalanceAfter_ == beast::zero)
                                ? Number{1}
                                : ((*lptAMMBalanceAfter_ - poolProductMean) /
                                   poolProductMean));
        return false;
    }
 
    return true;
}
 
bool
ValidAMM::finalizeDeposit(
    ripple::STTx const& tx,
    ripple::ReadView const& view,
    bool enforce,
    beast::Journal const& j) const
{
    if (!ammAccount_)
    {
        // LCOV_EXCL_START
        JLOG(j.error()) << "AMMDeposit invariant failed: AMM object is deleted";
        if (enforce)
            return false;
        // LCOV_EXCL_STOP
    }
    else if (!generalInvariant(tx, view, ZeroAllowed::No, j) && enforce)
        return false;
 
    return true;
}
 
bool
ValidAMM::finalizeWithdraw(
    ripple::STTx const& tx,
    ripple::ReadView const& view,
    bool enforce,
    beast::Journal const& j) const
{
    if (!ammAccount_)
    {
        // Last Withdraw or Clawback deleted AMM
    }
    else if (!generalInvariant(tx, view, ZeroAllowed::Yes, j))
    {
        if (enforce)
            return false;
    }
 
    return true;
}
 
bool
ValidAMM::finalize(
    STTx const& tx,
    TER const result,
    XRPAmount const,
    ReadView const& view,
    beast::Journal const& j)
{
    // Delete may return tecINCOMPLETE if there are too many
    // trustlines to delete.
    if (result != tesSUCCESS && result != tecINCOMPLETE)
        return true;
 
    bool const enforce = view.rules().enabled(fixAMMv1_3);
 
    switch (tx.getTxnType())
    {
        case ttAMM_CREATE:
            return finalizeCreate(tx, view, enforce, j);
        case ttAMM_DEPOSIT:
            return finalizeDeposit(tx, view, enforce, j);
        case ttAMM_CLAWBACK:
        case ttAMM_WITHDRAW:
            return finalizeWithdraw(tx, view, enforce, j);
        case ttAMM_BID:
            return finalizeBid(enforce, j);
        case ttAMM_VOTE:
            return finalizeVote(enforce, j);
        case ttAMM_DELETE:
            return finalizeDelete(enforce, result, j);
        case ttCHECK_CASH:
        case ttOFFER_CREATE:
        case ttPAYMENT:
            return finalizeDEX(enforce, j);
        default:
            break;
    }
 
    return true;
}
 
}  // namespace ripple