querystring: check that maxKeys is finite

lib/querystring.js

@@ -215,7 +215,7 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
   }
 
   // maxKeys <= 0 means that we should not limit keys count
-  if (maxKeys > 0) {
+  if (maxKeys > 0 && isFinite(maxKeys)) {
     qs = qs.split(sep, maxKeys);
   } else {
     qs = qs.split(sep);

test/parallel/test-querystring-maxKeys-non-finite.js

@@ -0,0 +1,55 @@
+'use strict';
+// This test was originally written to test a regression
+// that was introduced by
+// https://github.com/nodejs/node/pull/2288#issuecomment-179543894
+require('../common');
+
+const assert = require('assert');
+const parse = require('querystring').parse;
+
+/*
+taken from express-js/body-parser
+https://github.com/expressjs/body-parser/
+blob/ed25264fb494cf0c8bc992b8257092cd4f694d5e/test/urlencoded.js#L636-L651
+*/
+function createManyParams(count) {
+  var str = '';
+
+  if (count === 0) {
+    return str;
+  }
+
+  str += '0=0';
+
+  for (var i = 1; i < count; i++) {
+    var n = i.toString(36);
+    str += '&' + n + '=' + n;
+  }
+
+  return str;
+}
+
+const count = 10000;
+const originalMaxLength = 1000;
+const params = createManyParams(count);
+
+// thealphanerd
+// 27def4f introduced a change to parse that would cause Inifity
+// to be passed to String.prototype.split as an argument for limit
+// In this instance split will always return an empty array
+// this test confirms that the output of parse is the expected length
+// when passed Infinity as the argument for maxKeys
+const resultInfinity = parse(params, undefined, undefined, {maxKeys: Infinity});
+const resultNaN = parse(params, undefined, undefined, {maxKeys: NaN});
+const resultInfinityString = parse(params, undefined, undefined, {
+  maxKeys: 'Infinity'
+});
+const resultNaNString = parse(params, undefined, undefined, {maxKeys: 'NaN'});
+
+// Non Finite maxKeys should return the length of input
+assert.equal(Object.keys(resultInfinity).length, count);
+assert.equal(Object.keys(resultNaN).length, count);
+// Strings maxKeys should return the maxLength
+// defined by parses internals
+assert.equal(Object.keys(resultInfinityString).length, originalMaxLength);
+assert.equal(Object.keys(resultNaNString).length, originalMaxLength);