fix($parse): do not convert to string computed properties multiple times

Do not convert to string properties multiple times.

Author: lgalfaso

src/ng/parse.js

@@ -29,21 +29,31 @@ var promiseWarning;
 
 
 function ensureSafeMemberName(name, fullExpression) {
+  if (name === "__defineGetter__" || name === "__defineSetter__"
+      || name === "__lookupGetter__" || name === "__lookupSetter__"
+      || name === "__proto__") {
+    throw $parseMinErr('isecfld',
+        'Attempting to access a disallowed field in Angular expressions! '
+        + 'Expression: {0}', fullExpression);
+  }
+  return name;
+}
+
+function getStringValue(name, fullExpression) {
   // From the JavaScript docs:
   // Property names must be strings. This means that non-string objects cannot be used
   // as keys in an object. Any non-string object, including a number, is typecasted
   // into a string via the toString method.
   //
   // So, to ensure that we are checking the same `name` that JavaScript would use,
-  // we cast it to a string, if possible
-  name =  (isObject(name) && name.toString) ? name.toString() : name;
-
-  if (name === "__defineGetter__" || name === "__defineSetter__"
-      || name === "__lookupGetter__" || name === "__lookupSetter__"
-      || name === "__proto__") {
-    throw $parseMinErr('isecfld',
-        'Attempting to access a disallowed field in Angular expressions! '
-        +'Expression: {0}', fullExpression);
+  // we cast it to a string, if possible.
+  // Doing `name + ''` can cause a repl error if the result to `toString` is not a string,
+  // this is, this will handle objects that misbehave.
+  name = name + '';
+  if (!isString(name)) {
+    throw $parseMinErr('iseccst',
+        'Cannot convert object to primitive value! '
+        + 'Expression: {0}', fullExpression);
   }
   return name;
 }
@@ -722,7 +732,7 @@ Parser.prototype = {
 
     return extend(function(self, locals) {
       var o = obj(self, locals),
-          i = indexFn(self, locals),
+          i = getStringValue(indexFn(self, locals), parser.text),
           v, p;
 
       ensureSafeMemberName(i, parser.text);
@@ -739,7 +749,7 @@ Parser.prototype = {
       return v;
     }, {
       assign: function(self, value, locals) {
-        var key = ensureSafeMemberName(indexFn(self, locals), parser.text);
+        var key = ensureSafeMemberName(getStringValue(indexFn(self, locals), parser.text), parser.text);
         // prevent overwriting of Function.constructor which would break ensureSafeObject check
         var o = ensureSafeObject(obj(self, locals), parser.text);
         if (!o) obj.assign(self, o = {});

test/ng/parseSpec.js

@@ -1119,6 +1119,27 @@ describe('parser', function() {
           expect(count).toBe(1);
         });
 
+       it('should prevent the exploit', function() {
+          expect(function() {
+            scope.$eval('(1)[{0: "__proto__", 1: "__proto__", 2: "__proto__", 3: "safe", length: 4, toString: [].pop}].foo = 1');
+          }).toThrow();
+          if (!msie || msie > 10) {
+            expect((1)['__proto__'].foo).toBeUndefined();
+          }
+       });
+
+        it('should prevent the exploit', function() {
+          expect(function() {
+            scope.$eval('' +
+              ' "".sub.call.call(' +
+                '({})["constructor"].getOwnPropertyDescriptor("".sub.__proto__, "constructor").value,' +
+                'null,' +
+                '"alert(1)"' +
+              ')()' +
+              '');
+          }).toThrow();
+        });
+
 
         it('should call the function once when it is part of the context on array lookups', function() {
           var count = 0;