fix($compile): disallow interpolations for DOM event handlers

BREAKING CHANGE: Interpolations inside DOM event handlers are
    disallowed.  DOM event handlers execute arbitrary Javascript code.
    Using an interpolation for such handlers means that the interpolated
    value is a JS string that is evaluated.  Storing or generating such
    strings is error prone and likely leads to an XSS if you're not
    super careful.  On the other hand, ng-click and such event handlers
    evaluate Angular expressions that are a lot safer (e.g. No direct
    access to global objects - only scope), cleaner and harder to
    exploit.

    To migrate the code follow the example below:

    Before:

        JS:   scope.foo = 'alert(1)';
        HTML: <div onclick="{{foo}}">

    After:

        JS:   scope.foo = function() { alert(1); }
        HTML: <div ng-click="foo()">

src/ng/compile.js

@@ -155,6 +155,10 @@ function $CompileProvider($provide) {
       CLASS_DIRECTIVE_REGEXP = /(([\d\w\-_]+)(?:\:([^;]+))?;?)/,
       urlSanitizationWhitelist = /^\s*(https?|ftp|mailto|file):/;
 
+  // Ref: http://developers.whatwg.org/webappapis.html#event-handler-idl-attributes
+  // The assumption is that future DOM event attribute names will begin with
+  // 'on' and be composed of only English letters.
+  var EVENT_HANDLER_ATTR_REGEXP = /^(on[a-z]*|formaction)$/;
 
   /**
    * @ngdoc function
@@ -1165,6 +1169,12 @@ function $CompileProvider($provide) {
         compile: valueFn(function attrInterpolateLinkFn(scope, element, attr) {
           var $$observers = (attr.$$observers || (attr.$$observers = {}));
 
+          if (EVENT_HANDLER_ATTR_REGEXP.test(name)) {
+            throw $compileMinErr('nodomevents',
+                "Interpolations for HTML DOM event attributes are disallowed.  Please use the ng- " +
+                "versions (such as ng-click instead of onclick) instead.");
+          }
+
           // we need to interpolate again, in case the attribute value has been updated
           // (e.g. by another directive's compile function)
           interpolateFn = $interpolate(attr[name], true);

test/ng/compileSpec.js

@@ -2831,6 +2831,36 @@ describe('$compile', function() {
     });
   });
 
+  describe('interpolation on HTML DOM event handler attributes onclick, onXYZ, formaction', function() {
+    it('should disallow interpolation on onclick', inject(function($compile, $rootScope) {
+      // All interpolations are disallowed.
+      $rootScope.onClickJs = "";
+      expect(function() {
+          $compile('<button onclick="{{onClickJs}}"></script>')($rootScope);
+        }).toThrow(
+          "[$compile:nodomevents] Interpolations for HTML DOM event attributes are disallowed.  " +
+          "Please use the ng- versions (such as ng-click instead of onclick) instead.");
+      expect(function() {
+          $compile('<button ONCLICK="{{onClickJs}}"></script>')($rootScope);
+        }).toThrow(
+          "[$compile:nodomevents] Interpolations for HTML DOM event attributes are disallowed.  " +
+          "Please use the ng- versions (such as ng-click instead of onclick) instead.");
+      expect(function() {
+          $compile('<button ng-attr-onclick="{{onClickJs}}"></script>')($rootScope);
+        }).toThrow(
+          "[$compile:nodomevents] Interpolations for HTML DOM event attributes are disallowed.  " +
+          "Please use the ng- versions (such as ng-click instead of onclick) instead.");
+    }));
+
+    it('should pass through arbitrary values on onXYZ event attributes that contain a hyphen', inject(function($compile, $rootScope) {
+      element = $compile('<button on-click="{{onClickJs}}"></script>')($rootScope);
+      $rootScope.onClickJs = 'javascript:doSomething()';
+      $rootScope.$apply();
+      expect(element.attr('on-click')).toEqual('javascript:doSomething()');
+    }));
+  });
+
+
   describe('ngAttr* attribute binding', function() {
 
     it('should bind after digest but not before', inject(function($compile, $rootScope) {