Merge branch 'xrplf/sponsor' of https://github.com/XRPLF/rippled into mvadari/sponsor/apply-view-context

include/xrpl/ledger/helpers/SponsorHelpers.h

@@ -24,14 +24,6 @@ isReserveSponsored(STTx const& tx)
     return (tx.getFieldU32(sfSponsorFlags) & spfSponsorReserve) != 0u;
 }
 
-inline bool
-isSponsorReserveCoSigning(STTx const& tx)
-{
-    if (!tx.isFieldPresent(sfSponsorSignature))
-        return false;
-    return isReserveSponsored(tx);
-}
-
 inline std::optional<AccountID>
 getTxReserveSponsorAccountID(STTx const& tx)
 {

src/libxrpl/ledger/helpers/AccountRootHelpers.cpp

@@ -343,14 +343,14 @@ checkInsufficientReserve(
 {
     if (sponsorSle)
     {
-        auto const isCoSigning = isSponsorReserveCoSigning(tx);
-
         auto const sle = view.read(
             keylet::sponsorship(
                 sponsorSle->getAccountID(sfAccount), accSle->getAccountID(sfAccount)));
 
-        // prefunded sponsor should have a sponsorship entry
-        if (!isCoSigning && !sle)
+        // A reserve-sponsored tx must carry a sponsor signature
+        // (cosigning path) and/or have a pre-existing sponsorship SLE
+        // (prefunded path). Absence of both is an internal invariant break.
+        if (isReserveSponsored(tx) && !sle && !tx.isFieldPresent(sfSponsorSignature))
             return tecINTERNAL;  // LCOV_EXCL_LINE
 
         if (sle)

src/libxrpl/ledger/helpers/MPTokenHelpers.cpp

@@ -196,17 +196,15 @@ authorizeMPToken(
         if (!sponsorSle)
             return sponsorSle.error();  // LCOV_EXCL_LINE
 
-        auto const isSponsoredAndPreFunded = *sponsorSle && !isSponsorReserveCoSigning(ctx.tx);
-
         // The reserve that is required to create the MPToken. Note
         // that although the reserve increases with every item
         // an account owns, in the case of MPTokens we only
         // *enforce* a reserve if the user owns more than two
         // items. This is similar to the reserve requirements of trust lines.
-        // If PreFunded Sponsor, it must be checked whether sufficient
-        // ReserveCount exists.
-        if (ownerCount(view, *sponsorSle ? *sponsorSle : sleAcct, journal) >= 2 ||
-            isSponsoredAndPreFunded)
+        // The "free-tier" shortcut (ownerCount < 2) does not apply once a sponsor is on
+        // the tx — the sponsor must always cover the reserve (via balance or prefunded
+        // budget), so this check always runs for sponsored transactions.
+        if (*sponsorSle || ownerCount(view, sleAcct, journal) >= 2)
         {
             if (auto const ret = checkInsufficientReserve(
                     view, ctx.tx, sleAcct, priorBalance, *sponsorSle, 1, 0, journal);

src/libxrpl/tx/transactors/token/TrustSet.cpp

@@ -334,9 +334,9 @@ TrustSet::doApply()
 
     std::uint32_t const uOwnerCount = ownerCount(view(), *sponsorSle ? *sponsorSle : sle, j_);
 
-    bool const isSponsoredAndPreFunded = *sponsorSle && !isSponsorReserveCoSigning(ctx_.tx);
-    // If PreFunded Sponsor, it must be checked whether sufficient
-    // ReserveCount exists.
+    // The "free-tier" shortcut (ownerCount < 2) only applies when there is no sponsor.
+    // With any sponsor on the tx, the sponsor must cover the reserve (via balance or
+    // prefunded budget), so the reserve check always runs.
     bool const freeTrustLine = uOwnerCount < 2 && !*sponsorSle;
 
     std::uint32_t const uQualityIn(bQualityIn ? ctx_.tx.getFieldU32(sfQualityIn) : 0);
@@ -540,7 +540,7 @@ TrustSet::doApply()
             // calling adjustOwnerCount().
             if (auto const ret = checkInsufficientReserve(
                     view(), ctx_.tx, sleLowAccount, preFeeBalance_, *sponsorSle, 1, 0, j_);
-                isSponsoredAndPreFunded && !isTesSuccess(ret))
+                *sponsorSle && !isTesSuccess(ret))
                 return tecINSUF_RESERVE_LINE;
 
             // Set reserve for low account.
@@ -569,7 +569,7 @@ TrustSet::doApply()
             // calling adjustOwnerCount().
             if (auto const ret = checkInsufficientReserve(
                     view(), ctx_.tx, sleHighAccount, preFeeBalance_, *sponsorSle, 1, 0, j_);
-                isSponsoredAndPreFunded && !isTesSuccess(ret))
+                *sponsorSle && !isTesSuccess(ret))
                 return tecINSUF_RESERVE_LINE;
 
             // Set reserve for high account.

src/test/app/Sponsor_test.cpp

@@ -746,6 +746,47 @@ public:
         }
     }
 
+    void
+    testSponsoredFreeTierReserve()
+    {
+        testcase("Sponsored Free-Tier Reserve");
+        using namespace test::jtx;
+        Account const alice("alice");
+        Account const issuer("issuer");
+        Account const sponsor("sponsor");
+
+        // Trust lines and MPTokens normally skip the reserve check when the
+        // holder's ownerCount < 2 (the "free-tier" / first-two-items shortcut). When the
+        // tx is sponsored, that shortcut must not apply — the sponsor must
+        // still cover the reserve.
+        Env env{*this, testableAmendments()};
+        env.fund(XRP(10000), alice, issuer);
+        // Sponsor is funded just below the reserve required to cover a single
+        // sponsored item.
+        env.fund(reserve(env, 1) - drops(1), sponsor);
+        env.close();
+        BEAST_EXPECT(ownerCount(env, alice) == 0);
+
+        MPTTester mptt(env, issuer, {.fund = false});
+        mptt.create();
+
+        // Free-tier trust line cosigned by an undercapitalized sponsor must
+        // fail — the holder's free-first-two-items shortcut does not let the
+        // sponsor skip the reserve check.
+        env(trust(alice, issuer["USD"](100)),
+            sponsor::As(sponsor, spfSponsorReserve),
+            Sig(sfSponsorSignature, sponsor),
+            Ter(tecNO_LINE_INSUF_RESERVE));
+        env.close();
+
+        // Free-tier MPTokenAuthorize must also fail for the same reason.
+        env(MPTTester::authorizeJV({.account = alice, .id = mptt.issuanceID()}),
+            sponsor::As(sponsor, spfSponsorReserve),
+            Sig(sfSponsorSignature, sponsor),
+            Ter(tecINSUFFICIENT_RESERVE));
+        env.close();
+    }
+
     void
     testTransferSponsor()
     {
@@ -2821,10 +2862,11 @@ public:
             env(noop(sponsor), ticket::Use(ticketSeq));
             env.close();
 
-            // pass (free mptoken)
+            // pass (free-tier mptoken for the holder, but the sponsor is still
+            // charged a reserve increment regardless of the ownerCount < 2 shortcut).
             if (cosigning)
             {
-                adjustAccountXRPBalance(env, sponsor, reserve(env, 2) - drops(1));
+                adjustAccountXRPBalance(env, sponsor, reserve(env, 2));
                 env(jv,
                     sponsor::As(sponsor, spfSponsorReserve),
                     Sig(sfSponsorSignature, sponsor),
@@ -3723,6 +3765,7 @@ protected:
         testSimpleSponsorshipSet();
 
         testPreFundAndCosign();
+        testSponsoredFreeTierReserve();
 
         testTransferSponsor();
         testSponsorFee();