Fix redos

lib/dns-sync.js

@@ -3,11 +3,9 @@
 var util = require('util'),
     path = require('path'),
     shell = require('shelljs'),
+    isValidHostName = require('is-valid-hostname'),
     debug = require('debug')('dns-sync');
 
-//source - http://stackoverflow.com/questions/106179/regular-expression-to-match-dns-hostname-or-ip-address
-var ValidHostnameRegex = new RegExp("^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$");
-
 // https://nodejs.org/api/dns.html#dns_dns_resolve_hostname_rrtype_callback
 var RRecordTypes = [
     'A',
@@ -22,9 +20,6 @@ var RRecordTypes = [
     'TXT',
     'ANY'];
 
-function isValidHostName(hostname) {
-    return ValidHostnameRegex.test(hostname);
-}
 /**
  * Resolve hostname to IP address,
  * returns null in case of error

package.json

@@ -22,11 +22,12 @@
   "readmeFilename": "README.md",
   "dependencies": {
     "debug": "^4",
+    "is-valid-hostname": "^0.0.1",
     "shelljs": "~0.8"
   },
   "devDependencies": {
-    "mocha": "^6",
     "eslint": "^6",
-    "eslint-plugin-standard": "^4"
+    "eslint-plugin-standard": "^4",
+    "mocha": "^6"
   }
 }