dns: Use object without protoype for map

benjamingr · jasnell · commit c9c387fdac7d · 2016-03-22T11:13:03.000-07:00
Currently we use `{}` for the `lookup` function to find the relevant resolver to the dns.resolve function. It is preferable to use an object without a Object.prototype, currently for example you can do something like: ```js dns.resolve("google.com", "toString", console.log); ``` And get `[Object undefined]` logged and the callback would never be called. This is unexpected and strange behavior in my opinion. In addition, if someone adds a property to `Object.prototype` might also create unexpected results. This pull request fixes it, with it an appropriate error is thrown. PR-URL: #5843 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Michaël Zasso <mic.besace@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
diff --git a/lib/dns.js b/lib/dns.js
@@ -243,7 +243,7 @@ function resolver(bindingName) {
 }
 
 
-var resolveMap = {};
+var resolveMap = Object.create(null);
 exports.resolve4 = resolveMap.A = resolver('queryA');
 exports.resolve6 = resolveMap.AAAA = resolver('queryAaaa');
 exports.resolveCname = resolveMap.CNAME = resolver('queryCname');
diff --git a/test/parallel/test-c-ares.js b/test/parallel/test-c-ares.js
@@ -27,6 +27,11 @@ assert.throws(function() {
   dns.resolve('www.google.com', 'HI');
 }, /Unknown type/);
 
+// Try calling resolve with an unsupported type that's an object key
+assert.throws(function() {
+  dns.resolve('www.google.com', 'toString');
+}, /Unknown type/);
+
 // Windows doesn't usually have an entry for localhost 127.0.0.1 in
 // C:\Windows\System32\drivers\etc\hosts
 // so we disable this test on Windows.

Original file line number	Diff line number	Diff line change
`@@ -243,7 +243,7 @@ function resolver(bindingName) {`
`243`	`243`	`}`
`244`	`244`
`245`	`245`
`246`		`-var resolveMap = {};`
	`246`	`+var resolveMap = Object.create(null);`
`247`	`247`	`exports.resolve4 = resolveMap.A = resolver('queryA');`
`248`	`248`	`exports.resolve6 = resolveMap.AAAA = resolver('queryAaaa');`
`249`	`249`	`exports.resolveCname = resolveMap.CNAME = resolver('queryCname');`