Allow Vega's emsfile to bypass sanitization (#17370)

* Allow Vega's emsfile to bypass sanitization

Fixes https://github.com/elastic/kibana/issues/16669

src/core_plugins/vega/public/data_model/__tests__/vega_parser.js

@@ -1,6 +1,7 @@
 import _ from 'lodash';
 import expect from 'expect.js';
 import { VegaParser } from '../vega_parser';
+import { bypassExternalUrlCheck } from '../../vega_view/vega_base_view';
 
 describe(`VegaParser._setDefaultValue`, () => {
 
@@ -62,6 +63,7 @@ describe('VegaParser._resolveEsQueries', () => {
         getFileLayers: async () => [{ name: 'file1', url: 'url1' }]
       });
       await vp._resolveDataUrls();
+
       expect(vp.spec).to.eql(expected);
       expect(vp.warnings).to.have.length(warnCount || 0);
     };
@@ -73,7 +75,9 @@ describe('VegaParser._resolveEsQueries', () => {
   it('es', test({ data: { url: { index: 'a' }, x: 1 } }, { data: { values: [42], x: 1 } }));
   it('es', test({ data: { url: { '%type%': 'elasticsearch', index: 'a' } } }, { data: { values: [42] } }));
   it('es arr', test({ arr: [{ data: { url: { index: 'a' }, x: 1 } }] }, { arr: [{ data: { values: [42], x: 1 } }] }));
-  it('emsfile', test({ data: { url: { '%type%': 'emsfile', name: 'file1' } } }, { data: { url: 'url1' } }));
+  it('emsfile', test(
+    { data: { url: { '%type%': 'emsfile', name: 'file1' } } },
+    { data: { url: bypassExternalUrlCheck('url1') } }));
 });
 
 describe('VegaParser._parseSchema', () => {

src/core_plugins/vega/public/data_model/ems_file_parser.js

@@ -1,3 +1,5 @@
+import { bypassExternalUrlCheck } from '../vega_view/vega_base_view';
+
 /**
  * This class processes all Vega spec customizations,
  * converting url object parameters into query results.
@@ -38,7 +40,9 @@ export class EmsFileParser {
       if (!foundLayer) {
         throw new Error(`emsfile ${JSON.stringify(name)} does not exist`);
       }
-      obj.url = foundLayer.url;
+
+      // This URL can bypass loader sanitization at the later stage
+      obj.url = bypassExternalUrlCheck(foundLayer.url);
     }
   }
 

src/core_plugins/vega/public/vega_view/vega_base_view.js

@@ -8,6 +8,13 @@ vega.scheme('elastic',
   ['#00B3A4', '#3185FC', '#DB1374', '#490092', '#FEB6DB', '#F98510', '#E6C220', '#BFA180', '#920000', '#461A0A']
 );
 
+const bypassToken = Symbol();
+
+export function bypassExternalUrlCheck(url) {
+  // processed in the  loader.sanitize  below
+  return { url, bypassToken };
+}
+
 export class VegaBaseView {
   constructor(vegaConfig, editorMode, parentEl, vegaParser, serviceSettings) {
     this._vegaConfig = vegaConfig;
@@ -58,20 +65,7 @@ export class VegaBaseView {
         }
       });
 
-      this._vegaViewConfig = {
-        logLevel: vega.Warn,
-        renderer: this._parser.renderer,
-      };
-      if (!this._vegaConfig.enableExternalUrls) {
-        // Override URL loader and sanitizer to disable all URL-based requests
-        const errorFunc = () => {
-          throw new Error('External URLs are not enabled. Add  "vega": {"enableExternalUrls": true}  to kibana.yml');
-        };
-        const loader = vega.loader();
-        loader.load = errorFunc;
-        loader.sanitize = errorFunc;
-        this._vegaViewConfig.loader = loader;
-      }
+      this._vegaViewConfig = this.createViewConfig();
 
       // The derived class should create this method
       await this._initViewCustomizations();
@@ -80,6 +74,30 @@ export class VegaBaseView {
     }
   }
 
+  createViewConfig() {
+    const config = {
+      logLevel: vega.Warn,
+      renderer: this._parser.renderer,
+    };
+
+    // Override URL sanitizer to prevent external data loading (if disabled)
+    const loader = vega.loader();
+    const originalSanitize = loader.sanitize.bind(loader);
+    loader.sanitize = (uri, options) => {
+      if (uri.bypassToken === bypassToken) {
+        // If uri has a bypass token, the uri was encoded by bypassExternalUrlCheck() above.
+        // because user can only supply pure JSON data structure.
+        uri = uri.url;
+      } else if (!this._vegaConfig.enableExternalUrls) {
+        throw new Error('External URLs are not enabled. Add   vega.enableExternalUrls: true   to kibana.yml');
+      }
+      return originalSanitize(uri, options);
+    };
+    config.loader = loader;
+
+    return config;
+  }
+
   onError() {
     this._addMessage('err', Utils.formatErrorToStr(...arguments));
   }