Clawback.cpp

#include <xrpl/tx/transactors/token/Clawback.h>
 
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/core/ServiceRegistry.h>
#include <xrpl/ledger/helpers/AccountRootHelpers.h>
#include <xrpl/ledger/helpers/TokenHelpers.h>
#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/Concepts.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/Indexes.h>
#include <xrpl/protocol/Issue.h>
#include <xrpl/protocol/LedgerFormats.h>
#include <xrpl/protocol/MPTAmount.h>
#include <xrpl/protocol/MPTIssue.h>
#include <xrpl/protocol/Protocol.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STLedgerEntry.h>
#include <xrpl/protocol/STTx.h>
#include <xrpl/protocol/TER.h>
#include <xrpl/protocol/XRPAmount.h>
#include <xrpl/tx/ApplyContext.h>
#include <xrpl/tx/Transactor.h>
 
#include <algorithm>
#include <variant>
 
namespace xrpl {
 
template <ValidIssueType T>
static NotTEC
preflightHelper(PreflightContext const& ctx);
 
template <>
NotTEC
preflightHelper<Issue>(PreflightContext const& ctx)
{
    if (ctx.tx.isFieldPresent(sfHolder))
        return temMALFORMED;
 
    AccountID const issuer = ctx.tx[sfAccount];
    STAmount const clawAmount = ctx.tx[sfAmount];
 
    // The issuer field is used for the token holder instead
    AccountID const& holder = clawAmount.getIssuer();
 
    if (issuer == holder || isXRP(clawAmount) || clawAmount <= beast::kZero)
        return temBAD_AMOUNT;
 
    return tesSUCCESS;
}
 
template <>
NotTEC
preflightHelper<MPTIssue>(PreflightContext const& ctx)
{
    if (!ctx.rules.enabled(featureMPTokensV1))
        return temDISABLED;
 
    auto const mptHolder = ctx.tx[~sfHolder];
    auto const clawAmount = ctx.tx[sfAmount];
 
    if (!mptHolder)
        return temMALFORMED;
 
    // issuer is the same as holder
    if (ctx.tx[sfAccount] == *mptHolder)
        return temMALFORMED;
 
    if (clawAmount.mpt() > MPTAmount{kMaxMpTokenAmount} || clawAmount <= beast::kZero)
        return temBAD_AMOUNT;
 
    return tesSUCCESS;
}
 
NotTEC
Clawback::preflight(PreflightContext const& ctx)
{
    if (auto const ret = std::visit(
            [&]<typename T>(T const&) { return preflightHelper<T>(ctx); },
            ctx.tx[sfAmount].asset().value());
        !isTesSuccess(ret))
        return ret;
 
    return tesSUCCESS;
}
 
template <ValidIssueType T>
static TER
preclaimHelper(
    PreclaimContext const& ctx,
    SLE const& sleIssuer,
    AccountID const& issuer,
    AccountID const& holder,
    STAmount const& clawAmount);
 
template <>
TER
preclaimHelper<Issue>(
    PreclaimContext const& ctx,
    SLE const& sleIssuer,
    AccountID const& issuer,
    AccountID const& holder,
    STAmount const& clawAmount)
{
    // If AllowTrustLineClawback is not set or NoFreeze is set, return no
    // permission
    if (!sleIssuer.isFlag(lsfAllowTrustLineClawback) || sleIssuer.isFlag(lsfNoFreeze))
        return tecNO_PERMISSION;
 
    auto const sleRippleState =
        ctx.view.read(keylet::trustLine(holder, issuer, clawAmount.get<Issue>().currency));
    if (!sleRippleState)
        return tecNO_LINE;
 
    STAmount const balance = (*sleRippleState)[sfBalance];
 
    // If balance is positive, issuer must have higher address than holder
    if (balance > beast::kZero && issuer < holder)
        return tecNO_PERMISSION;
 
    // If balance is negative, issuer must have lower address than holder
    if (balance < beast::kZero && issuer > holder)
        return tecNO_PERMISSION;
 
    // At this point, we know that issuer and holder accounts
    // are correct and a trustline exists between them.
    //
    // Must now explicitly check the balance to make sure
    // available balance is non-zero.
    //
    // We can't directly check the balance of trustline because
    // the available balance of a trustline is prone to new changes (eg.
    // XLS-34). So we must use `accountHolds`.
    if (accountHolds(
            ctx.view,
            holder,
            clawAmount.get<Issue>().currency,
            issuer,
            FreezeHandling::IgnoreFreeze,
            ctx.j) <= beast::kZero)
        return tecINSUFFICIENT_FUNDS;
 
    return tesSUCCESS;
}
 
template <>
TER
preclaimHelper<MPTIssue>(
    PreclaimContext const& ctx,
    SLE const& sleIssuer,
    AccountID const& issuer,
    AccountID const& holder,
    STAmount const& clawAmount)
{
    auto const issuanceKey = keylet::mptokenIssuance(clawAmount.get<MPTIssue>().getMptID());
    auto const sleIssuance = ctx.view.read(issuanceKey);
    if (!sleIssuance)
        return tecOBJECT_NOT_FOUND;
 
    if (!sleIssuance->isFlag(lsfMPTCanClawback))
        return tecNO_PERMISSION;
 
    if (sleIssuance->getAccountID(sfIssuer) != issuer)
        return tecNO_PERMISSION;
 
    if (!ctx.view.exists(keylet::mptoken(issuanceKey.key, holder)))
        return tecOBJECT_NOT_FOUND;
 
    if (accountHolds(
            ctx.view,
            holder,
            clawAmount.get<MPTIssue>(),
            FreezeHandling::IgnoreFreeze,
            AuthHandling::IgnoreAuth,
            ctx.j) <= beast::kZero)
        return tecINSUFFICIENT_FUNDS;
 
    return tesSUCCESS;
}
 
TER
Clawback::preclaim(PreclaimContext const& ctx)
{
    AccountID const issuer = ctx.tx[sfAccount];
    auto const clawAmount = ctx.tx[sfAmount];
    AccountID const holder = clawAmount.holds<Issue>() ? clawAmount.getIssuer() : ctx.tx[sfHolder];
 
    auto const sleIssuer = ctx.view.read(keylet::account(issuer));
    auto const sleHolder = ctx.view.read(keylet::account(holder));
    if (!sleIssuer || !sleHolder)
        return terNO_ACCOUNT;
 
    // Note the order of checks - when SAV is active, this check here will make
    // the one which follows `sleHolder->isFieldPresent(sfAMMID)` redundant.
    if (ctx.view.rules().enabled(featureSingleAssetVault) && isPseudoAccount(sleHolder))
    {
        return tecPSEUDO_ACCOUNT;
    }
    if (sleHolder->isFieldPresent(sfAMMID))
    {
        return tecAMM_ACCOUNT;
    }
 
    return std::visit(
        [&]<typename T>(T const&) {
            return preclaimHelper<T>(ctx, *sleIssuer, issuer, holder, clawAmount);
        },
        ctx.tx[sfAmount].asset().value());
}
 
template <ValidIssueType T>
static TER
applyHelper(ApplyContext& ctx);
 
template <>
TER
applyHelper<Issue>(ApplyContext& ctx)
{
    AccountID const issuer = ctx.tx[sfAccount];
    STAmount clawAmount = ctx.tx[sfAmount];
    AccountID const holder = clawAmount.getIssuer();  // cannot be reference
 
    // Replace the `issuer` field with issuer's account
    clawAmount.get<Issue>().account = issuer;
    if (holder == issuer)
        return tecINTERNAL;  // LCOV_EXCL_LINE
 
    // Get the spendable balance. Must use `accountHolds`.
    STAmount const spendableAmount = accountHolds(
        ctx.view(),
        holder,
        clawAmount.get<Issue>().currency,
        clawAmount.getIssuer(),
        FreezeHandling::IgnoreFreeze,
        ctx.journal);
 
    return directSendNoFee(
        ctx.view(), holder, issuer, std::min(spendableAmount, clawAmount), true, ctx.journal);
}
 
template <>
TER
applyHelper<MPTIssue>(ApplyContext& ctx)
{
    AccountID const issuer = ctx.tx[sfAccount];
    auto clawAmount = ctx.tx[sfAmount];
    AccountID const holder = ctx.tx[sfHolder];
 
    // Get the spendable balance. Must use `accountHolds`.
    STAmount const spendableAmount = accountHolds(
        ctx.view(),
        holder,
        clawAmount.get<MPTIssue>(),
        FreezeHandling::IgnoreFreeze,
        AuthHandling::IgnoreAuth,
        ctx.journal);
 
    return directSendNoFee(
        ctx.view(),
        holder,
        issuer,
        std::min(spendableAmount, clawAmount),
        /*checkIssuer*/ false,
        ctx.journal);
}
 
TER
Clawback::doApply()
{
    return std::visit(
        [&]<typename T>(T const&) { return applyHelper<T>(ctx_); },
        ctx_.tx[sfAmount].asset().value());
}
 
void
Clawback::visitInvariantEntry(bool, SLE::const_ref, SLE::const_ref)
{
    // No transaction-specific invariants yet (future work).
}
 
bool
Clawback::finalizeInvariants(STTx const&, TER, XRPAmount, ReadView const&, beast::Journal const&)
{
    // No transaction-specific invariants yet (future work).
    return true;
}
 
}  // namespace xrpl