crypto: prevent Sign::SignFinal from crashing

The validation logic could be tricked into assuming an option was
valid using malicious getters, leading to an invalid value being
passed to the C++ layer, thus crashing the process.

PR-URL: #21815
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>

lib/internal/crypto/sig.js

@@ -57,10 +57,11 @@ function getSaltLength(options) {
 
 function getIntOption(name, defaultValue, options) {
   if (options.hasOwnProperty(name)) {
-    if (options[name] === options[name] >> 0) {
-      return options[name];
+    const value = options[name];
+    if (value === value >> 0) {
+      return value;
     } else {
-      throw new ERR_INVALID_OPT_VALUE(name, options[name]);
+      throw new ERR_INVALID_OPT_VALUE(name, value);
     }
   }
   return defaultValue;