feat($compile): Lower the security context of SVG's a and image xlink:href attributes.

They should go through regular sanitization, RESOURCE_URL is overkill there.
This does not change the context for the rest of xlink:href attributes.

This is a breaking change in very unlikely cases. If someone whitelisted RESOURCE_URL
for the purpose of binding into xlink:href, and that these can't pass the regular URL
sanitization, they'll get broken: the fix is to whitelist in the $compileProvider's
URL sanitization.

Author: rjamet

src/ng/compile.js

@@ -1671,7 +1671,8 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
         nodeName = nodeName_(this.$$element);
 
         if ((nodeName === 'a' && (key === 'href' || key === 'xlinkHref')) ||
-            (nodeName === 'img' && key === 'src')) {
+            (nodeName === 'img' && key === 'src') ||
+            (nodeName === 'image' && key === 'xlinkHref')) {
           // sanitize a[href] and img[src] values
           this[key] = value = $$sanitizeUri(value, key === 'src');
         } else if (nodeName === 'img' && key === 'srcset' && isDefined(value)) {
@@ -3254,8 +3255,10 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
         if (['img', 'video', 'audio', 'source', 'track'].indexOf(tag) === -1) {
           return $sce.RESOURCE_URL;
         }
-      // maction[xlink:href] can source SVG.  It's not limited to <maction>.
-      } else if (attrNormalizedName === 'xlinkHref' ||
+      } else if (
+          // Some xlink:href are okay, most aren't
+          (attrNormalizedName === 'xlinkHref' && (tag !== 'image' && tag !== 'a')) ||
+          // Formaction
           (tag === 'form' && attrNormalizedName === 'action') ||
           // If relative URLs can go where they are not expected to, then
           // all sorts of trust issues can arise.

test/ng/compileSpec.js

@@ -11122,23 +11122,42 @@ describe('$compile', function() {
     });
 
     it('should use $$sanitizeUri when working with svg and xlink:href', function() {
+      var $$sanitizeUri = jasmine.createSpy('$$sanitizeUri');
+      module(function($provide) {
+        $provide.value('$$sanitizeUri', $$sanitizeUri);
+      });
+      inject(function($compile, $rootScope) {
+        element = $compile('<svg><a xlink:href="{{ testUrl }}"></a></svg>')($rootScope);
+
+        //both of these fail the RESOURCE_URL test, that shouldn't be run
+        $rootScope.testUrl = 'https://bad.example.org';
+        $$sanitizeUri.and.returnValue('https://clean.example.org');
+
+        $rootScope.$apply();
+        expect(element.find('a').attr('xlink:href')).toBe('https://clean.example.org');
+        expect($$sanitizeUri).toHaveBeenCalledWith($rootScope.testUrl, false);
+      });
+    });
+
+    it('should use $$sanitizeUri when working with svg and xlink:href through ng-href', function() {
       var $$sanitizeUri = jasmine.createSpy('$$sanitizeUri');
       module(function($provide) {
         $provide.value('$$sanitizeUri', $$sanitizeUri);
       });
       inject(function($compile, $rootScope) {
         element = $compile('<svg><a xlink:href="" ng-href="{{ testUrl }}"></a></svg>')($rootScope);
-        $rootScope.testUrl = 'evilUrl';
+        //both of these fail the RESOURCE_URL test, that shouldn't be run
+        $rootScope.testUrl = 'https://bad.example.org';
+        $$sanitizeUri.and.returnValue('https://clean.example.org');
 
-        $$sanitizeUri.and.returnValue('someSanitizedUrl');
         $rootScope.$apply();
-        expect(element.find('a').prop('href').baseVal).toBe('someSanitizedUrl');
+        expect(element.find('a').prop('href').baseVal).toBe('https://clean.example.org');
         expect($$sanitizeUri).toHaveBeenCalledWith($rootScope.testUrl, false);
       });
     });
 
 
-    it('should use $$sanitizeUri when working with svg and xlink:href', function() {
+    it('should use $$sanitizeUri when working with svg and xlink:href through ng-href', function() {
       var $$sanitizeUri = jasmine.createSpy('$$sanitizeUri');
       module(function($provide) {
         $provide.value('$$sanitizeUri', $$sanitizeUri);
@@ -11153,6 +11172,18 @@ describe('$compile', function() {
         expect($$sanitizeUri).toHaveBeenCalledWith($rootScope.testUrl, false);
       });
     });
+
+
+    it('should have a RESOURCE_URL context for xlink:href by default', function() {
+      inject(function($compile, $rootScope) {
+        element = $compile('<svg><whatever xlink:href="{{ testUrl }}"></whatever></svg>')($rootScope);
+        $rootScope.testUrl = 'https://bad.example.org';
+
+        expect(function() {
+          $rootScope.$apply();
+        }).toThrowError(/\$sce:insecurl/);
+      });
+    });
   });
 
   describe('interpolation on HTML DOM event handler attributes onclick, onXYZ, formaction', function() {