src: fix tls certificate root store data race

OpenSSL internally synchronizes access to the X509_STORE. Creation of
the global root store in Node was not properly synchronized, however,
introducing the possibility of data races when multiple threads try to
create it concurrently.

This commit coincidentally removes the last call to the thread-unsafe
ERR_error_string() function.

Fixes: #45743
PR-URL: #45767
Reviewed-By: Anna Henningsen <anna@addaleax.net>

src/crypto/crypto_context.cc

@@ -47,10 +47,14 @@ static const char* const root_certs[] = {
 
 static const char system_cert_path[] = NODE_OPENSSL_SYSTEM_CERT_PATH;
 
-static X509_STORE* root_cert_store;
-
 static bool extra_root_certs_loaded = false;
 
+inline X509_STORE* GetOrCreateRootCertStore() {
+  // Guaranteed thread-safe by standard, just don't use -fno-threadsafe-statics.
+  static X509_STORE* store = NewRootCertStore();
+  return store;
+}
+
 // Takes a string or buffer and loads it into a BIO.
 // Caller responsible for BIO_free_all-ing the returned object.
 BIOPointer LoadBIO(Environment* env, Local<Value> v) {
@@ -701,7 +705,7 @@ void SecureContext::AddCACert(const FunctionCallbackInfo<Value>& args) {
   X509_STORE* cert_store = SSL_CTX_get_cert_store(sc->ctx_.get());
   while (X509Pointer x509 = X509Pointer(PEM_read_bio_X509_AUX(
              bio.get(), nullptr, NoPasswordCallback, nullptr))) {
-    if (cert_store == root_cert_store) {
+    if (cert_store == GetOrCreateRootCertStore()) {
       cert_store = NewRootCertStore();
       SSL_CTX_set_cert_store(sc->ctx_.get(), cert_store);
     }
@@ -731,7 +735,7 @@ void SecureContext::AddCRL(const FunctionCallbackInfo<Value>& args) {
     return THROW_ERR_CRYPTO_OPERATION_FAILED(env, "Failed to parse CRL");
 
   X509_STORE* cert_store = SSL_CTX_get_cert_store(sc->ctx_.get());
-  if (cert_store == root_cert_store) {
+  if (cert_store == GetOrCreateRootCertStore()) {
     cert_store = NewRootCertStore();
     SSL_CTX_set_cert_store(sc->ctx_.get(), cert_store);
   }
@@ -745,14 +749,10 @@ void SecureContext::AddRootCerts(const FunctionCallbackInfo<Value>& args) {
   SecureContext* sc;
   ASSIGN_OR_RETURN_UNWRAP(&sc, args.Holder());
   ClearErrorOnReturn clear_error_on_return;
-
-  if (root_cert_store == nullptr) {
-    root_cert_store = NewRootCertStore();
-  }
-
+  X509_STORE* store = GetOrCreateRootCertStore();
   // Increment reference count so global store is not deleted along with CTX.
-  X509_STORE_up_ref(root_cert_store);
-  SSL_CTX_set_cert_store(sc->ctx_.get(), root_cert_store);
+  X509_STORE_up_ref(store);
+  SSL_CTX_set_cert_store(sc->ctx_.get(), store);
 }
 
 void SecureContext::SetCipherSuites(const FunctionCallbackInfo<Value>& args) {
@@ -1025,7 +1025,7 @@ void SecureContext::LoadPKCS12(const FunctionCallbackInfo<Value>& args) {
     for (int i = 0; i < sk_X509_num(extra_certs.get()); i++) {
       X509* ca = sk_X509_value(extra_certs.get(), i);
 
-      if (cert_store == root_cert_store) {
+      if (cert_store == GetOrCreateRootCertStore()) {
         cert_store = NewRootCertStore();
         SSL_CTX_set_cert_store(sc->ctx_.get(), cert_store);
       }
@@ -1328,24 +1328,18 @@ unsigned long AddCertsFromFile(  // NOLINT(runtime/int)
 
 // UseExtraCaCerts is called only once at the start of the Node.js process.
 void UseExtraCaCerts(const std::string& file) {
+  if (file.empty()) return;
   ClearErrorOnReturn clear_error_on_return;
-
-  if (root_cert_store == nullptr) {
-    root_cert_store = NewRootCertStore();
-
-    if (!file.empty()) {
-      unsigned long err = AddCertsFromFile(  // NOLINT(runtime/int)
-                                           root_cert_store,
-                                           file.c_str());
-      if (err) {
-        fprintf(stderr,
-                "Warning: Ignoring extra certs from `%s`, load failed: %s\n",
-                file.c_str(),
-                ERR_error_string(err, nullptr));
-      } else {
-        extra_root_certs_loaded = true;
-      }
-    }
+  X509_STORE* store = GetOrCreateRootCertStore();
+  if (auto err = AddCertsFromFile(store, file.c_str())) {
+    char buf[256];
+    ERR_error_string_n(err, buf, sizeof(buf));
+    fprintf(stderr,
+            "Warning: Ignoring extra certs from `%s`, load failed: %s\n",
+            file.c_str(),
+            buf);
+  } else {
+    extra_root_certs_loaded = true;
   }
 }