Merge remote-tracking branch 'origin/tapanito/bugfix-loan-pay-fn-67' into ripple/lending-protocol-fv

src/libxrpl/tx/transactors/lending/LoanPay.cpp

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/Number.h>
+#include <xrpl/beast/utility/Journal.h>
 #include <xrpl/beast/utility/Zero.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/json/to_string.h>
@@ -9,6 +10,8 @@
 #include <xrpl/ledger/View.h>
 #include <xrpl/ledger/helpers/LendingHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
+#include <xrpl/protocol/AccountID.h>
+#include <xrpl/protocol/Asset.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/LedgerFormats.h>
@@ -33,6 +36,34 @@
 
 namespace xrpl {
 
+namespace {
+// Returns the account's true, unclamped balance in `asset`, for use only in
+// fund-conservation checks. accountHolds(..., SpendableHandling::FullBalance)
+// cannot be used for this: for XRP it always defers to xrpLiquid, which
+// subtracts the account's reserve, so a payee sitting below its own reserve
+// would appear to receive nothing even though its raw ledger balance grew.
+// That mismatch is exactly what a conservation check must not see.
+STAmount
+conservationBalance(ReadView const& view, AccountID const& id, Asset const& asset, beast::Journal j)
+{
+    if (isXRP(asset))
+    {
+        auto const sle = view.read(keylet::account(id));
+        if (!sle)
+            return STAmount{};
+        return view.balanceHookIOU(id, xrpAccount(), sle->getFieldAmount(sfBalance));
+    }
+    return accountHolds(
+        view,
+        id,
+        asset,
+        FreezeHandling::IgnoreFreeze,
+        AuthHandling::IgnoreAuth,
+        j,
+        SpendableHandling::FullBalance);
+}
+}  // namespace
+
 bool
 LoanPay::checkExtraFeatures(PreflightContext const& ctx)
 {
@@ -587,34 +618,13 @@ LoanPay::doApply()
     }
 
     // These three values are used to check that funds are conserved after the transfers
-    auto const accountBalanceBefore = accountHolds(
-        view,
-        accountID_,
-        asset,
-        FreezeHandling::IgnoreFreeze,
-        AuthHandling::IgnoreAuth,
-        j_,
-        SpendableHandling::FullBalance);
+    auto const accountBalanceBefore = conservationBalance(view, accountID_, asset, j_);
     auto const vaultBalanceBefore = accountID_ == vaultPseudoAccount
         ? STAmount{asset, 0}
-        : accountHolds(
-              view,
-              vaultPseudoAccount,
-              asset,
-              FreezeHandling::IgnoreFreeze,
-              AuthHandling::IgnoreAuth,
-              j_,
-              SpendableHandling::FullBalance);
+        : conservationBalance(view, vaultPseudoAccount, asset, j_);
     auto const brokerBalanceBefore = accountID_ == brokerPayee
         ? STAmount{asset, 0}
-        : accountHolds(
-              view,
-              brokerPayee,
-              asset,
-              FreezeHandling::IgnoreFreeze,
-              AuthHandling::IgnoreAuth,
-              j_,
-              SpendableHandling::FullBalance);
+        : conservationBalance(view, brokerPayee, asset, j_);
 
     if (totalPaidToVaultRounded != beast::kZero)
     {
@@ -670,33 +680,13 @@ LoanPay::doApply()
 #endif
 
     // Check that funds are conserved
-    auto const accountBalanceAfter = accountHolds(
-        view,
-        accountID_,
-        asset,
-        FreezeHandling::IgnoreFreeze,
-        AuthHandling::IgnoreAuth,
-        j_,
-        SpendableHandling::FullBalance);
+    auto const accountBalanceAfter = conservationBalance(view, accountID_, asset, j_);
     auto const vaultBalanceAfter = accountID_ == vaultPseudoAccount
         ? STAmount{asset, 0}
-        : accountHolds(
-              view,
-              vaultPseudoAccount,
-              asset,
-              FreezeHandling::IgnoreFreeze,
-              AuthHandling::IgnoreAuth,
-              j_,
-              SpendableHandling::FullBalance);
-    auto const brokerBalanceAfter = accountID_ == brokerPayee ? STAmount{asset, 0}
-                                                              : accountHolds(
-                                                                    view,
-                                                                    brokerPayee,
-                                                                    asset,
-                                                                    FreezeHandling::IgnoreFreeze,
-                                                                    AuthHandling::IgnoreAuth,
-                                                                    j_,
-                                                                    SpendableHandling::FullBalance);
+        : conservationBalance(view, vaultPseudoAccount, asset, j_);
+    auto const brokerBalanceAfter = accountID_ == brokerPayee
+        ? STAmount{asset, 0}
+        : conservationBalance(view, brokerPayee, asset, j_);
     auto const balanceScale = [&]() {
         // Find a reasonable scale to use for the balance comparisons.
         //

src/test/app/Loan_test.cpp

@@ -11183,6 +11183,107 @@ protected:
         checkVaultBroker(99'025, 0, 0, 975, "after LoanManage(default)");
     }
 
+    void
+    testLoanPayFundsConservedPayeeBelowReserve(FeatureBitset features)
+    {
+        // Regression test: LoanPay::doApply's fund-conservation check used to
+        // read XRP balances via accountHolds(..., SpendableHandling::
+        // FullBalance), which for XRP always defers to xrpLiquid (balance
+        // minus reserve, clamped at zero). When the broker fee landed on a
+        // payee sitting below its own reserve, that payee's clamped balance
+        // stayed zero and the fee vanished from the conservation sum,
+        // tripping "funds are conserved (with rounding)".
+        testcase << "LoanPay funds conserved: broker fee payee below reserve";
+
+        using namespace jtx;
+
+        Env env(*this, features);
+
+        Account const issuer{"issuer"};
+        Account const lender{"lender"};
+        Account const borrower{"borrower"};
+
+        // Broker defaults match the fuzz workload: ManagementFeeRate = 100
+        // tenth-bips. The service fee guarantees feePaid > 0 on the first
+        // regular payment.
+        BrokerParameters const brokerParams;
+        Number const serviceFeeValue{2};
+        LoanParameters const loanParams{
+            .account = borrower,
+            .counter = lender,
+            .principalRequest = 1000,
+            .serviceFee = serviceFeeValue,
+            .interest = TenthBips32{percentageToTenthBips(12)},
+            .payTotal = 12,
+            .payInterval = 3600};
+
+        auto const loanOpt =
+            createLoan(env, AssetType::XRP, brokerParams, loanParams, issuer, lender, borrower);
+        if (BEAST_EXPECT(loanOpt); !loanOpt.has_value())
+            return;
+        auto const& [broker, loanKeylet, brokerPseudo] = *loanOpt;
+
+        auto const vaultPseudo = [&]() {
+            auto const vaultSle = env.le(keylet::vault(broker.vaultID));
+            BEAST_EXPECT(vaultSle);
+            return vaultSle ? vaultSle->at(sfAccount) : AccountID{};
+        }();
+
+        // Raw AccountRoot balance, matching LoanPay::doApply's conservation
+        // check (not the reserve-clamped accountHolds()/xrpLiquid() value).
+        auto rawBalance = [&](AccountID const& id) -> STAmount {
+            auto const sle = env.le(keylet::account(id));
+            return sle ? sle->getFieldAmount(sfBalance) : STAmount{};
+        };
+        auto lenderReserve = [&] {
+            return env.current()->fees().accountReserve(ownerCount(env, lender), 1);
+        };
+
+        STAmount const baseFee{env.current()->fees().base};
+
+        // Park the lender (broker owner, fee payee) exactly at its reserve,
+        // then burn part of the reserve with an oversized transaction fee.
+        // Fees are exempt from the reserve check, so the balance ends up
+        // below the reserve.
+        env(pay(lender, issuer, rawBalance(lender.id()) - lenderReserve() - baseFee));
+        env(noop(lender), Fee(XRP(100)));
+        env.close();
+        BEAST_EXPECT(env.balance(lender) < lenderReserve());
+
+        // First regular payment, exactly the amount due.
+        auto const state = getCurrentState(env, broker, loanKeylet);
+        STAmount const serviceFee = broker.asset(serviceFeeValue);
+        STAmount const roundedPeriodicPayment{
+            broker.asset,
+            roundPeriodicPayment(broker.asset, state.periodicPayment, state.loanScale)};
+        STAmount const totalDue = roundToScale(
+            roundedPeriodicPayment + serviceFee, state.loanScale, Number::RoundingMode::Upward);
+
+        auto const borrowerBefore = rawBalance(borrower.id());
+        auto const vaultBefore = rawBalance(vaultPseudo);
+        auto const lenderBefore = rawBalance(lender.id());
+
+        // Before the fix, this aborted inside LoanPay::doApply on
+        // XRPL_ASSERT_PARTS(goodRounding, "xrpl::LoanPay::doApply", "funds
+        // are conserved (with rounding)").
+        env(loan::pay(borrower, loanKeylet.key, totalDue));
+        env.close();
+
+        auto const borrowerAfter = rawBalance(borrower.id());
+        auto const vaultAfter = rawBalance(vaultPseudo);
+        auto const lenderAfter = rawBalance(lender.id());
+
+        // The broker fee reached the lender's AccountRoot, even though the
+        // lender's balance remains below its reserve.
+        BEAST_EXPECT(lenderAfter > lenderBefore);
+        BEAST_EXPECT(lenderAfter < lenderReserve());
+
+        // Total funds conserved across the payer, vault, and fee payee.
+        BEAST_EXPECT(
+            borrowerBefore - baseFee + vaultBefore + lenderBefore ==
+            borrowerAfter + vaultAfter + lenderAfter);
+    }
+
     void
     runAmendmentIndependent()
     {
@@ -11226,6 +11327,8 @@ protected:
         testLoanPayLateFullPaymentBypassesPenalties(features);
         testLoanCoverMinimumRoundingExploit(features);
 #endif
+        testLoanPayFundsConservedPayeeBelowReserve(features);
+
         // Lifecycle
         testLifecycle(features);
         testLoanSet(features);