Fix clang-tidy: const correctness

* XRPLF/develop:
  chore: Enable clang-tidy modernize-use-nodiscard check (7015)
  fix: Resolve MSVC Debug build failure in JobQueue.h; re-enable _CRTDBG_MAP_ALLOC in CI (6993)
  docs: Update hybrid offer invariant comment (7007)
  fix: Fix flaky CI tests (7005)
  docs: Update bug bounty information (7006)
  fix: Make assorted Payments fixes (6585)
  refactor: Move `LendingHelpers` into `libxrpl/ledger/helpers` (6638)

src/libxrpl/ledger/helpers/LendingHelpers.cpp

@@ -1857,8 +1857,18 @@ loanMakePayment(
 
     // -------------------------------------------------------------
     // overpayment handling
+    //
+    // If the "fixSecurity3_1_3" amendment is enabled, truncate "amount",
+    // at the loan scale. If the raw value is used, the overpayment
+    // amount could be meaningless dust. Trying to process such a small
+    // amount will, at best, waste time when all the result values round
+    // to zero. At worst, it can cause logical errors with tiny amounts
+    // of interest that don't add up correctly.
+    auto const roundedAmount = view.rules().enabled(fixSecurity3_1_3)
+        ? roundToAsset(asset, amount, loanScale, Number::towards_zero)
+        : amount;
     if (paymentType == LoanPaymentType::overpayment && loan->isFlag(lsfLoanOverpayment) &&
-        paymentRemainingProxy > 0 && totalPaid < amount &&
+        paymentRemainingProxy > 0 && totalPaid < roundedAmount &&
         numPayments < loanMaximumPaymentsPerTransaction)
     {
         TenthBips32 const overpaymentInterestRate{loan->at(sfOverpaymentInterestRate)};
@@ -1867,7 +1877,7 @@ loanMakePayment(
         // It shouldn't be possible for the overpayment to be greater than
         // totalValueOutstanding, because that would have been processed as
         // another normal payment. But cap it just in case.
-        Number const overpayment = std::min(amount - totalPaid, *totalValueOutstandingProxy);
+        Number const overpayment = std::min(roundedAmount - totalPaid, *totalValueOutstandingProxy);
 
         detail::ExtendedPaymentComponents const overpaymentComponents =
             detail::computeOverpaymentComponents(

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

@@ -30,6 +30,7 @@
 #include <bit>
 #include <cstdint>
 #include <memory>
+#include <vector>
 
 namespace xrpl {
 
@@ -143,6 +144,7 @@ LoanPay::calculateBaseFee(ReadView const& view, STTx const& tx)
     Number const numPaymentEstimate = static_cast<std::int64_t>(amount / regularPayment);
 
     // Charge one base fee per paymentsPerFeeIncrement payments, rounding up.
+    // This set round is safe because there's a mode guard just above
     Number::setround(Number::upward);
     auto const feeIncrements = std::max(
         std::int64_t(1),
@@ -440,9 +442,10 @@ LoanPay::doApply()
     // Vault object state changes
     view.update(vaultSle);
 
+    Number const assetsAvailableBefore = *assetsAvailableProxy;
+    Number const assetsTotalBefore = *assetsTotalProxy;
 #if !NDEBUG
     {
-        Number const assetsAvailableBefore = *assetsAvailableProxy;
         Number const pseudoAccountBalanceBefore = accountHolds(
             view,
             vaultPseudoAccount,
@@ -466,16 +469,6 @@ LoanPay::doApply()
         "xrpl::LoanPay::doApply",
         "assets available must not be greater than assets outstanding");
 
-    if (*assetsAvailableProxy > *assetsTotalProxy)
-    {
-        // LCOV_EXCL_START
-        JLOG(j_.fatal()) << "Vault assets available must not be greater "
-                            "than assets outstanding. Available: "
-                         << *assetsAvailableProxy << ", Total: " << *assetsTotalProxy;
-        return tecINTERNAL;
-        // LCOV_EXCL_STOP
-    }
-
     JLOG(j_.debug()) << "total paid to vault raw: " << totalPaidToVaultRaw
                      << ", total paid to vault rounded: " << totalPaidToVaultRounded
                      << ", total paid to broker: " << totalPaidToBroker
@@ -501,12 +494,68 @@ LoanPay::doApply()
     associateAsset(*vaultSle, asset);
 
     // Duplicate some checks after rounding
+    Number const assetsAvailableAfter = *assetsAvailableProxy;
+    Number const assetsTotalAfter = *assetsTotalProxy;
+
     XRPL_ASSERT_PARTS(
-        *assetsAvailableProxy <= *assetsTotalProxy,
+        assetsAvailableAfter <= assetsTotalAfter,
         "xrpl::LoanPay::doApply",
         "assets available must not be greater than assets outstanding");
+    if (assetsAvailableAfter == assetsAvailableBefore)
+    {
+        // An unchanged assetsAvailable indicates that the amount paid to the
+        // vault was zero, or rounded to zero. That should be impossible, but I
+        // can't rule it out for extreme edge cases, so fail gracefully if it
+        // happens.
+        //
+        // LCOV_EXCL_START
+        JLOG(j_.warn()) << "LoanPay: Vault assets available unchanged after rounding: "  //
+                        << "Before: " << assetsAvailableBefore                           //
+                        << ", After: " << assetsAvailableAfter;
+        return tecPRECISION_LOSS;
+        // LCOV_EXCL_STOP
+    }
+    if (paymentParts->valueChange != beast::zero && assetsTotalAfter == assetsTotalBefore)
+    {
+        // Non-zero valueChange with an unchanged assetsTotal indicates that the
+        // actual value change rounded to zero. That should be impossible, but I
+        // can't rule it out for extreme edge cases, so fail gracefully if it
+        // happens.
+        //
+        // LCOV_EXCL_START
+        JLOG(j_.warn())
+            << "LoanPay: Vault assets expected change, but unchanged after rounding: "  //
+            << "Before: " << assetsTotalBefore                                          //
+            << ", After: " << assetsTotalAfter                                          //
+            << ", ValueChange: " << paymentParts->valueChange;
+        return tecPRECISION_LOSS;
+        // LCOV_EXCL_STOP
+    }
+    if (paymentParts->valueChange == beast::zero && assetsTotalAfter != assetsTotalBefore)
+    {
+        // A change in assetsTotal when there was no valueChange indicates that
+        // something really weird happened. That should be flat out impossible.
+        //
+        // LCOV_EXCL_START
+        JLOG(j_.fatal()) << "LoanPay: Vault assets changed unexpectedly after rounding: "  //
+                         << "Before: " << assetsTotalBefore                                //
+                         << ", After: " << assetsTotalAfter                                //
+                         << ", ValueChange: " << paymentParts->valueChange;
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
+    if (assetsAvailableAfter > assetsTotalAfter)
+    {
+        // Assets available are not allowed to be larger than assets total.
+        // LCOV_EXCL_START
+        JLOG(j_.fatal()) << "LoanPay: Vault assets available must not be greater "
+                            "than assets outstanding. Available: "
+                         << assetsAvailableAfter << ", Total: " << assetsTotalAfter;
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
 
-#if !NDEBUG
+    // These three values are used to check that funds are conserved after the transfers
     auto const accountBalanceBefore = accountHolds(
         view,
         account_,
@@ -535,7 +584,6 @@ LoanPay::doApply()
               ahIGNORE_AUTH,
               j_,
               SpendableHandling::shFULL_BALANCE);
-#endif
 
     if (totalPaidToVaultRounded != beast::zero)
     {
@@ -571,19 +619,22 @@ LoanPay::doApply()
         return ter;
 
 #if !NDEBUG
-    Number const assetsAvailableAfter = *assetsAvailableProxy;
+    {
-    Number const pseudoAccountBalanceAfter = accountHolds(
+        Number const pseudoAccountBalanceAfter = accountHolds(
-        view,
+            view,
-        vaultPseudoAccount,
+            vaultPseudoAccount,
-        asset,
+            asset,
-        FreezeHandling::fhIGNORE_FREEZE,
+            FreezeHandling::fhIGNORE_FREEZE,
-        AuthHandling::ahIGNORE_AUTH,
+            AuthHandling::ahIGNORE_AUTH,
-        j_);
+            j_);
-    XRPL_ASSERT_PARTS(
+        XRPL_ASSERT_PARTS(
-        assetsAvailableAfter == pseudoAccountBalanceAfter,
+            assetsAvailableAfter == pseudoAccountBalanceAfter,
-        "xrpl::LoanPay::doApply",
+            "xrpl::LoanPay::doApply",
-        "vault pseudo balance agrees after");
+            "vault pseudo balance agrees after");
+    }
+#endif
 
+    // Check that funds are conserved
     auto const accountBalanceAfter = accountHolds(
         view,
         account_,
@@ -612,14 +663,121 @@ LoanPay::doApply()
               ahIGNORE_AUTH,
               j_,
               SpendableHandling::shFULL_BALANCE);
+    auto const balanceScale = [&]() {
+        // Find a reasonable scale to use for the balance comparisons.
+        //
+        // First find the minimum and maximum exponent of all the non-zero balances, before and
+        // after. If min and max are equal, use that value. If they are not, use "max + 1" to reduce
+        // rounding discrepancies without making the result meaningless. Cap the scale at
+        // STAmount::cMaxOffset, just in case the numbers are all very large.
+        std::vector<int> exponents;
 
+        for (auto const& a : {
+                 accountBalanceBefore,
+                 vaultBalanceBefore,
+                 brokerBalanceBefore,
+                 accountBalanceAfter,
+                 vaultBalanceAfter,
+                 brokerBalanceAfter,
+             })
+        {
+            // Exclude zeroes
+            if (a != beast::zero)
+                exponents.push_back(a.exponent());
+        }
+        if (exponents.empty())
+        {
+            UNREACHABLE("xrpl::LoanPay::doApply : all zeroes");
+            return 0;
+        }
+        auto const [minItr, maxItr] = std::ranges::minmax_element(exponents);
+        auto const min = *minItr;
+        auto const max = *maxItr;
+        JLOG(j_.trace()) << "Min scale: " << min << ", max scale: " << max;
+        // IOU rounding can be interesting. We want all the balance checks to agree, but don't want
+        // to round to such an extreme that it becomes meaningless.  e.g. Everything rounds to one
+        // digit. So add 1 to the max (reducing the number of digits after the decimal point by 1)
+        // if the scales are not already all the same.
+        return std::min(min == max ? max : max + 1, STAmount::cMaxOffset);
+    }();
+
+    // No object changes are made below this point
     XRPL_ASSERT_PARTS(
-        accountBalanceBefore + vaultBalanceBefore + brokerBalanceBefore ==
+        Number::getround() == Number::to_nearest,
-            accountBalanceAfter + vaultBalanceAfter + brokerBalanceAfter,
+        "xrpl::LoanPay::doApply",
+        "Number rounding to_nearest");
+    NumberRoundModeGuard const mg(Number::to_nearest);
+
+    auto const accountBalanceBeforeRounded = roundToScale(accountBalanceBefore, balanceScale);
+    auto const vaultBalanceBeforeRounded = roundToScale(vaultBalanceBefore, balanceScale);
+    auto const brokerBalanceBeforeRounded = roundToScale(brokerBalanceBefore, balanceScale);
+
+    auto const totalBalanceBefore = accountBalanceBefore + vaultBalanceBefore + brokerBalanceBefore;
+    auto const totalBalanceBeforeRounded = roundToScale(totalBalanceBefore, balanceScale);
+
+    JLOG(j_.trace()) << "Before: "  //
+                     << "account " << Number(accountBalanceBeforeRounded) << " ("
+                     << Number(accountBalanceBefore) << ")"
+                     << ", vault " << Number(vaultBalanceBeforeRounded) << " ("
+                     << Number(vaultBalanceBefore) << ")"
+                     << ", broker " << Number(brokerBalanceBeforeRounded) << " ("
+                     << Number(brokerBalanceBefore) << ")"
+                     << ", total " << Number(totalBalanceBeforeRounded) << " ("
+                     << Number(totalBalanceBefore) << ")";
+
+    auto const accountBalanceAfterRounded = roundToScale(accountBalanceAfter, balanceScale);
+    auto const vaultBalanceAfterRounded = roundToScale(vaultBalanceAfter, balanceScale);
+    auto const brokerBalanceAfterRounded = roundToScale(brokerBalanceAfter, balanceScale);
+
+    auto const totalBalanceAfter = accountBalanceAfter + vaultBalanceAfter + brokerBalanceAfter;
+    auto const totalBalanceAfterRounded = roundToScale(totalBalanceAfter, balanceScale);
+
+    JLOG(j_.trace()) << "After: "  //
+                     << "account " << Number(accountBalanceAfterRounded) << " ("
+                     << Number(accountBalanceAfter) << ")"
+                     << ", vault " << Number(vaultBalanceAfterRounded) << " ("
+                     << Number(vaultBalanceAfter) << ")"
+                     << ", broker " << Number(brokerBalanceAfterRounded) << " ("
+                     << Number(brokerBalanceAfter) << ")"
+                     << ", total " << Number(totalBalanceAfterRounded) << " ("
+                     << Number(totalBalanceAfter) << ")";
+
+    auto const accountBalanceChange = accountBalanceAfter - accountBalanceBefore;
+    auto const vaultBalanceChange = vaultBalanceAfter - vaultBalanceBefore;
+    auto const brokerBalanceChange = brokerBalanceAfter - brokerBalanceBefore;
+
+    auto const totalBalanceChange = accountBalanceChange + vaultBalanceChange + brokerBalanceChange;
+    auto const totalBalanceChangeRounded = roundToScale(totalBalanceChange, balanceScale);
+
+    JLOG(j_.trace()) << "Changes: "                                    //
+                     << "account " << to_string(accountBalanceChange)  //
+                     << ", vault " << to_string(vaultBalanceChange)    //
+                     << ", broker " << to_string(brokerBalanceChange)  //
+                     << ", total " << to_string(totalBalanceChangeRounded) << " ("
+                     << Number(totalBalanceChange) << ")";
+
+    if (totalBalanceBeforeRounded != totalBalanceAfterRounded)
+    {
+        JLOG(j_.warn()) << "Total rounded balances don't match"
+                        << (totalBalanceChangeRounded == beast::zero ? ", but total changes do"
+                                                                     : "");
+    }
+    if (totalBalanceChangeRounded != beast::zero)
+    {
+        JLOG(j_.warn()) << "Total balance changes don't match"
+                        << (totalBalanceBeforeRounded == totalBalanceAfterRounded
+                                ? ", but total balances do"
+                                : "");
+    }
+
+    // Rounding for IOUs can be weird, so check a few different ways to show
+    // that funds are conserved.
+    XRPL_ASSERT_PARTS(
+        totalBalanceBeforeRounded == totalBalanceAfterRounded ||
+            totalBalanceChangeRounded == beast::zero,
         "xrpl::LoanPay::doApply",
         "funds are conserved (with rounding)");
-    XRPL_ASSERT_PARTS(
+
-        accountBalanceAfter >= beast::zero, "xrpl::LoanPay::doApply", "positive account balance");
     XRPL_ASSERT_PARTS(
         accountBalanceAfter < accountBalanceBefore || account_ == asset.getIssuer(),
         "xrpl::LoanPay::doApply",
@@ -640,7 +798,6 @@ LoanPay::doApply()
         vaultBalanceAfter > vaultBalanceBefore || brokerBalanceAfter > brokerBalanceBefore,
         "xrpl::LoanPay::doApply",
         "vault and/or broker balance increased");
-#endif
 
     return tesSUCCESS;
 }

src/test/app/Loan_test.cpp

@@ -370,16 +370,11 @@ protected:
                         env.balance(vaultPseudo, broker.asset).number());
                     if (ownerCount == 0)
                     {
-                        // Allow some slop for rounding IOUs
+                        // The Vault must be perfectly balanced if there
-
+                        // are no loans outstanding
-                        // TODO: This needs to be an exact match once all the
-                        // other rounding issues are worked out.
                         auto const total = vaultSle->at(sfAssetsTotal);
                         auto const available = vaultSle->at(sfAssetsAvailable);
-                        env.test.BEAST_EXPECT(
+                        env.test.BEAST_EXPECT(total == available);
-                            total == available ||
-                            (!broker.asset.integral() && available != 0 &&
-                             ((total - available) / available < Number(1, -6))));
                         env.test.BEAST_EXPECT(vaultSle->at(sfLossUnrealized) == 0);
                     }
                 }
@@ -7068,6 +7063,140 @@ protected:
         BEAST_EXPECT(afterSecondCoverAvailable == 0);
     }
 
+    void
+    testYieldTheftRounding(std::uint32_t flags)
+    {
+        testcase("Rounding manipulation does not permit yield theft");
+        using namespace jtx;
+        using namespace loan;
+
+        // 1. Setup Environment
+        Env env(*this, all);
+        Account const issuer{"issuer"};
+        Account const lender{"lender"};
+        Account const borrower{"borrower"};
+
+        env.fund(XRP(1000), issuer, lender, borrower);
+        env.close();
+
+        // 2. Asset Selection
+        PrettyAsset const iou = issuer["USD"];
+        env(trust(lender, iou(100'000'000)));
+        env(trust(borrower, iou(100'000'000)));
+        env(pay(issuer, lender, iou(100'000'000)));
+        env(pay(issuer, borrower, iou(100'000'000)));
+        env.close();
+
+        // 3. Create Vault and Broker with High Debt Limit (100M)
+        auto const brokerInfo = createVaultAndBroker(
+            env,
+            iou,
+            lender,
+            {
+                .vaultDeposit = 5'000'000,
+                .debtMax = Number{100'000'000},
+                .coverDeposit = 500'000,
+            });
+        auto const [currentSeq, vaultKeylet] = [&]() {
+            auto const brokerSle = env.le(keylet::loanbroker(brokerInfo.brokerID));
+            auto const currentSeq = brokerSle->at(sfLoanSequence);
+            auto const vaultKeylet = keylet::vault(brokerSle->at(sfVaultID));
+            return std::make_tuple(currentSeq, vaultKeylet);
+        }();
+
+        // 4. Loan Parameters (Attack Vector)
+        Number const principal = 1'000'000;
+        TenthBips32 const interestRate = TenthBips32{1};  // 0.001%
+        std::uint32_t const paymentInterval = 86400;
+        std::uint32_t const paymentTotal = 3650;
+
+        auto const loanSetFee = fee(env.current()->fees().base * 2);
+        env(set(borrower, brokerInfo.brokerID, iou(principal).value(), flags),
+            sig(sfCounterpartySignature, lender),
+            loan::interestRate(interestRate),
+            loan::paymentInterval(paymentInterval),
+            loan::paymentTotal(paymentTotal),
+            fee(loanSetFee));
+        env.close();
+
+        // --- RETRIEVE OBJECTS & SETUP ATTACK ---
+
+        auto borrowerBalance = [&]() { return env.balance(borrower, iou); };
+        auto const borrowerScale = static_cast<STAmount const&>(borrowerBalance()).exponent();
+
+        auto const loanKeylet = keylet::loan(brokerInfo.brokerID, currentSeq);
+        auto const maybePeriodicPayment = [&]() -> std::optional<STAmount> {
+            auto const loanSle = env.le(loanKeylet);
+            if (!BEAST_EXPECT(loanSle))
+                return std::nullopt;
+            // Construct Payment
+            return STAmount{iou, loanSle->at(sfPeriodicPayment)};
+        }();
+        if (!maybePeriodicPayment)
+            return;
+        auto const periodicPayment = *maybePeriodicPayment;
+        auto const roundedPayment = roundToScale(periodicPayment, borrowerScale, Number::upward);
+
+        // ATTACK: Add dust buffer (1e-9) to force 'excess' logic execution
+        STAmount const paymentBuffer{iou, Number(1, -9)};
+        STAmount const attackPayment = periodicPayment + paymentBuffer;
+
+        auto const maybeInitialVaultAssets = [&]() -> std::optional<Number> {
+            auto const vault = env.le(vaultKeylet);
+            if (!BEAST_EXPECT(vault))
+                return std::nullopt;
+            return vault->at(sfAssetsTotal);
+        }();
+        if (!maybeInitialVaultAssets)
+            return;
+        auto const initialVaultAssets = *maybeInitialVaultAssets;
+
+        // 5. Execution Loop
+        int yieldTheftCount = 0;
+        auto previousAssetsTotal = initialVaultAssets;
+
+        for (int i = 0; i < 100; ++i)
+        {
+            auto const balanceBefore = borrowerBalance();
+            env(pay(borrower, loanKeylet.key, attackPayment, flags));
+            env.close();
+            auto const borrowerDelta = balanceBefore - borrowerBalance();
+            BEAST_EXPECT(borrowerDelta.signum() == roundedPayment.signum());
+
+            auto const loanSle = env.le(loanKeylet);
+            if (!BEAST_EXPECT(loanSle))
+                break;
+            auto const updatedPayment = STAmount{iou, loanSle->at(sfPeriodicPayment)};
+            BEAST_EXPECT(
+                (roundToScale(updatedPayment, borrowerScale, Number::upward) == roundedPayment));
+            BEAST_EXPECT(
+                (updatedPayment == periodicPayment) ||
+                (flags == tfLoanOverpayment && i >= 2 && updatedPayment < periodicPayment));
+
+            auto const currentVaultSle = env.le(vaultKeylet);
+            if (!BEAST_EXPECT(currentVaultSle))
+                break;
+
+            auto const currentAssetsTotal = currentVaultSle->at(sfAssetsTotal);
+            auto const delta = currentAssetsTotal - previousAssetsTotal;
+
+            BEAST_EXPECT(
+                (delta == beast::zero && borrowerDelta <= roundedPayment) ||
+                (delta > beast::zero && borrowerDelta > roundedPayment));
+
+            // If tx succeeded but Assets Total didn't change, interest was
+            // stolen.
+            if (delta == beast::zero && borrowerDelta > roundedPayment)
+            {
+                yieldTheftCount++;
+            }
+
+            previousAssetsTotal = currentAssetsTotal;
+        }
+
+        BEAST_EXPECTS(yieldTheftCount == 0, std::to_string(yieldTheftCount));
+    }
+
     // Tests that vault withdrawals work correctly when the vault has unrealized
     // loss from an impaired loan, ensuring the invariant check properly
     // accounts for the loss.
@@ -7206,6 +7335,11 @@ public:
         testLoanPayLateFullPaymentBypassesPenalties();
         testLoanCoverMinimumRoundingExploit();
 #endif
+        for (auto const flags : {0u, tfLoanOverpayment})
+        {
+            testYieldTheftRounding(flags);
+        }
+
         testWithdrawReflectsUnrealizedLoss();
         testInvalidLoanSet();