Let a contract emit transactions from its own pseudo-account

checkSign rejects every pseudo-account when BatchV1_1 is enabled, but
emitted transactions need BatchV1_1 to skip the signature check. So no
contract could emit anything. Allow a contract pseudo-account on inner
transactions, and make emitBuiltTxn and emitTxn reject a transaction
whose Account is not the running contract's account. Without that
check, a contract could emit an unsigned transaction from any account.

src/libxrpl/tx/Transactor.cpp

@@ -929,11 +929,16 @@ Transactor::checkSign(
 
         if ((view.rules().enabled(featureLendingProtocol) ||
              view.rules().enabled(featureBatchV1_1) || view.rules().enabled(fixCleanup3_3_0)) &&
-            isPseudoAccount(sle))
+            isPseudoAccount(sle) && !(parentBatchId && sle->isFieldPresent(sfContractID)))
         {
             // Pseudo-accounts can't sign transactions. This check is gated on a
             // few different amendments so that it takes effect as soon as any of
             // them is activated.
+            //
+            // A contract's pseudo-account is the exception for inner transactions:
+            // the contract emits them, and the emit host functions allow only the
+            // running contract's own account. A Batch can't use this, because its
+            // BatchSigners are checked without a parentBatchId.
             return tefBAD_AUTH;
         }
     }

src/libxrpl/tx/wasm/ContractHostFuncImpl.cpp

@@ -973,6 +973,11 @@ ContractHostFunctionsImpl::emitBuiltTxn(std::uint32_t const& index)
             return std::unexpected(HostFunctionError::SubmitTxnFailure);
         }
 
+        // Inner transactions skip the signature check, so a contract may emit
+        // only from its own account.
+        if (stx->getAccountID(sfAccount) != contractCtx.result.contractAccount)
+            return std::unexpected(HostFunctionError::SubmitTxnFailure);
+
         // Use a persistent emit view that is seeded with the
         // transactor's pending state changes (balances, consumed
         // sequence, etc.) so that each emitted transaction validates
@@ -1040,6 +1045,10 @@ ContractHostFunctionsImpl::emitTxn(std::shared_ptr<STTx const> const& stxPtr)
             return std::unexpected(HostFunctionError::SubmitTxnFailure);
         }
 
+        // See emitBuiltTxn: a contract may emit only from its own account.
+        if (txPtr->getAccountID(sfAccount) != contractCtx.result.contractAccount)
+            return std::unexpected(HostFunctionError::SubmitTxnFailure);
+
         // Use a persistent emit view seeded with the transactor's
         // pending state, and do a full apply() for each emission
         // (see emitBuiltTxn for detailed rationale).