crypto: Use reference count to manage cert_store

Setting reference count at the time of setting cert_store instead of
trying to manage it by modifying internal states in destructor.

PR-URL: #8334

src/node_crypto.cc

@@ -773,6 +773,8 @@ void SecureContext::AddRootCerts(const FunctionCallbackInfo<Value>& args) {
   }
 
   sc->ca_store_ = root_cert_store;
+  // Increment reference count so global store is not deleted along with CTX.
+  CRYPTO_add(&root_cert_store->references, 1, CRYPTO_LOCK_X509_STORE);
   SSL_CTX_set_cert_store(sc->ctx_, sc->ca_store_);
 }
 

src/node_crypto.h

@@ -142,13 +142,6 @@ class SecureContext : public BaseObject {
   void FreeCTXMem() {
     if (ctx_) {
       env()->isolate()->AdjustAmountOfExternalAllocatedMemory(-kExternalSize);
-      if (ctx_->cert_store == root_cert_store) {
-        // SSL_CTX_free() will attempt to free the cert_store as well.
-        // Since we want our root_cert_store to stay around forever
-        // we just clear the field. Hopefully OpenSSL will not modify this
-        // struct in future versions.
-        ctx_->cert_store = nullptr;
-      }
       SSL_CTX_free(ctx_);
       if (cert_ != nullptr)
         X509_free(cert_);