Fix NewTransaction method (#78)

Author: uurien

src/api/string_methods.cc

@@ -151,7 +151,8 @@ void AddSecureMarksToTaintedString(const FunctionCallbackInfo<Value>& args) {
     }
 
     uintptr_t transactionId = utils::GetLocalStringPointer(transactionIdArgument);
-    auto transaction = NewTransaction(transactionId);
+
+    auto transaction = GetTransaction(transactionId);
     if (transaction == nullptr) {
         return;
     }

src/transaction_manager.h

@@ -20,12 +20,12 @@ class TransactionManager {
     void operator=(TransactionManager const&) = delete;
 
     T* New(U id) {
-        if (_map.size() >= _maxItems) {
-            return nullptr;
-        }
-
         auto found = _map.find(id);
         if (found == _map.end()) {
+            if (_map.size() >= _maxItems) {
+                return nullptr;
+            }
+
             T* item = _pool.Pop(id);
             _map[id] = item;
             return item;

test/js/new_tainted_string.spec.js

@@ -11,10 +11,18 @@ describe('Taint strings', function () {
   const value = 'test'
   const id = TaintedUtils.createTransaction('1')
 
+  before(() => {
+    TaintedUtils.setMaxTransactions(1)
+  })
+
   afterEach(function () {
     TaintedUtils.removeTransaction(id)
   })
 
+  after(() => {
+    TaintedUtils.setMaxTransactions(2)
+  })
+
   it('Taint new string with undefined transaction', function () {
     const ret = TaintedUtils.newTaintedString(undefined, value, 'param', 'REQUEST')
     assert.strictEqual(ret, 'test', 'Unexpected value')