Add new invariants

include/xrpl/tx/invariants/LoanInvariant.h

@@ -37,9 +37,13 @@ namespace xrpl {
  *         must be absent.
  *      c. Either `Borrower`, or both `Counterparty` and `CounterpartySignature`,
  *         must be present.
+ *      d. If `Borrower` is present, it must differ from the submitting
+ *         `Account`.
  * 6. A `LoanSet` that creates a loan must set `lsfLoanPending` if and only if
  *    `Borrower` is present and `CounterpartySignature` is absent.
  * 7. A `LoanSet` that creates a loan must set the loan's `Borrower`.
+ *    Additionally, a pending loan's `StartDate` must be in the future (so it is
+ *    still in the future when `LoanAccept` finalizes it).
  * 8. A pending loan (`lsfLoanPending` set) must not be linked into the
  *    borrower's directory (`OwnerNode` absent), and a non-pending loan must
  *    be linked (`OwnerNode` present).

src/libxrpl/tx/invariants/LoanInvariant.cpp

@@ -182,6 +182,14 @@ ValidLoan::finalize(
                                    "CounterpartySignature";
                 return false;
             }
+            // In the two-step flow the named Borrower must be a different
+            // account from the one submitting the LoanSet.
+            if (hasBorrower && tx.getAccountID(sfBorrower) == tx.getAccountID(sfAccount))
+            {
+                JLOG(j.fatal()) << "Invariant failed: LoanSet Borrower is the "
+                                   "submitting account";
+                return false;
+            }
 
             bool const shouldPend = hasBorrower && !hasCounterpartySig;
             if (shouldPend != after->isFlag(lsfLoanPending))
@@ -191,6 +199,18 @@ ValidLoan::finalize(
                 return false;
             }
 
+            // A pending loan (the two-step flow) is accepted in a later ledger,
+            // so its StartDate must be strictly in the future at creation to
+            // remain in the future when LoanAccept finalizes it.
+            if (shouldPend &&
+                after->getFieldU32(sfStartDate) <=
+                    view.parentCloseTime().time_since_epoch().count())
+            {
+                JLOG(j.fatal()) << "Invariant failed: LoanSet created a pending "
+                                   "Loan whose StartDate is not in the future";
+                return false;
+            }
+
             // A created loan must always record its Borrower.
             if (!after->isFieldPresent(sfBorrower))
             {

src/test/app/Invariants_test.cpp

@@ -4123,8 +4123,9 @@ class Invariants_test : public beast::unit_test::Suite
             // Creates a fully paid-off loan, optionally flagged pending, so the
             // earlier loan checks pass and only the LoanSet creation checks
             // fire.
-            auto const createLoan = [](bool pending) {
-                return [pending](Account const& a1, Account const&, ApplyContext& ac) {
+            auto const createLoan = [](bool pending,
+                                       std::optional<std::uint32_t> startDate = std::nullopt) {
+                return [pending, startDate](Account const& a1, Account const&, ApplyContext& ac) {
                     auto const vaultKeylet = keylet::vault(a1.id(), ac.view().seq());
                     auto const loanKeylet = keylet::loan(vaultKeylet.key, 1);
                     auto sleLoan = std::make_shared<SLE>(loanKeylet);
@@ -4135,6 +4136,8 @@ class Invariants_test : public beast::unit_test::Suite
                     sleLoan->setFieldU32(sfPaymentRemaining, 0);
                     if (pending)
                         sleLoan->setFlag(lsfLoanPending);
+                    if (startDate)
+                        sleLoan->setFieldU32(sfStartDate, *startDate);
                     ac.view().insert(sleLoan);
                     return true;
                 };
@@ -4228,6 +4231,35 @@ class Invariants_test : public beast::unit_test::Suite
                         tx.makeFieldPresent(sfCounterpartySignature);
                     }},
                 {tecINVARIANT_FAILED, tefINVARIANT_FAILED});
+
+            // In the two-step flow the named Borrower must differ from the
+            // submitting account; a LoanSet where they are equal is a violation.
+            doInvariantCheck(
+                Env{*this, defaultAmendments() | featureLendingProtocolV1_1},
+                {"LoanSet Borrower is the submitting account"},
+                createLoan(false),
+                XRPAmount{},
+                STTx{
+                    ttLOAN_SET,
+                    [&](STObject& tx) {
+                        tx.setAccountID(sfAccount, borrower.id());
+                        tx.setAccountID(sfBorrower, borrower.id());
+                    }},
+                {tecINVARIANT_FAILED, tefINVARIANT_FAILED});
+
+            // A pending loan created by the two-step flow must have a StartDate
+            // in the future; creating one with a past StartDate is a violation.
+            // createLoan(true, 1) makes a pending loan whose StartDate (1) is in
+            // the past, and the Borrower-only LoanSet keeps the pending flag
+            // consistent so this check is reached.
+            doInvariantCheck(
+                Env{*this, defaultAmendments() | featureLendingProtocolV1_1},
+                {"LoanSet created a pending Loan whose StartDate is not in the "
+                 "future"},
+                createLoan(true, 1u),
+                XRPAmount{},
+                STTx{ttLOAN_SET, [&](STObject& tx) { tx.setAccountID(sfBorrower, borrower.id()); }},
+                {tecINVARIANT_FAILED, tefINVARIANT_FAILED});
         }
 
         // Loan interest due (total value less principal and management fee)