Fix a bug where basepath nextUrl is invalid when it should be valid (#2096)

* Fix a bug where basepath nextUrl is invalid when it should be valid

Signed-off-by: Derek Ho <[email protected]>

* Udpate test

Signed-off-by: Derek Ho <[email protected]>

---------

Signed-off-by: Derek Ho <[email protected]>
(cherry picked from commit b1148fb)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

server/utils/next_url.test.ts

@@ -104,6 +104,11 @@ describe('test validateNextUrl', () => {
     expect(validateNextUrl(url, '')).toEqual(undefined);
   });
 
+  test('allow basePath', () => {
+    const url = '/osd';
+    expect(validateNextUrl(url, '/osd')).toEqual(undefined);
+  });
+
   test('allow dashboard url', () => {
     const url =
       '/_plugin/opensearch-dashboards/app/opensearch-dashboards#dashbard/dashboard-id?_g=(param=a&p=b)';

server/utils/next_url.ts

@@ -73,7 +73,7 @@ export function validateNextUrl(
     }
     const pathMinusBase = path.replace(bp, '');
     if (
-      !pathMinusBase.startsWith('/') ||
+      (pathMinusBase && !pathMinusBase.startsWith('/')) ||
       (pathMinusBase.length >= 2 && !/^\/[a-zA-Z_][\/a-zA-Z0-9-_]+$/.test(pathMinusBase))
     ) {
       return INVALID_NEXT_URL_PARAMETER_MESSAGE;