Add ZKP and ciphertext malleability tests (#6999)

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

@@ -94,6 +94,7 @@ ConfidentialMPTClawback::preclaim(PreclaimContext const& ctx)
         return tecNO_PERMISSION;  // LCOV_EXCL_LINE
 
     // Sanity check: claw amount can not exceed confidential outstanding amount
+    // or total outstanding amount (prevents underflow in doApply)
     auto const amount = ctx.tx[sfMPTAmount];
     if (amount > (*sleIssuance)[~sfConfidentialOutstandingAmount].value_or(0) ||
         amount > (*sleIssuance)[sfOutstandingAmount])

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

@@ -248,6 +248,9 @@ ConfidentialMPTConvert::doApply()
         // homomorphically add auditor's encrypted balance
         if (auditorEc)
         {
+            if (!sleMptoken->isFieldPresent(sfAuditorEncryptedBalance))
+                return tecINTERNAL;  // LCOV_EXCL_LINE
+
             auto sum = homomorphicAdd(*auditorEc, (*sleMptoken)[sfAuditorEncryptedBalance]);
             if (!sum)
                 return tecINTERNAL;  // LCOV_EXCL_LINE
@@ -258,7 +261,8 @@ ConfidentialMPTConvert::doApply()
     else if (
         !sleMptoken->isFieldPresent(sfIssuerEncryptedBalance) &&
         !sleMptoken->isFieldPresent(sfConfidentialBalanceInbox) &&
-        !sleMptoken->isFieldPresent(sfConfidentialBalanceSpending))
+        !sleMptoken->isFieldPresent(sfConfidentialBalanceSpending) &&
+        !sleMptoken->isFieldPresent(sfAuditorEncryptedBalance))
     {
         // Case 2: First-time convert - initialize all confidential fields
         (*sleMptoken)[sfConfidentialBalanceInbox] = holderEc;