Perform a client-side redirect after OAuth server authorization

Summary:
Ref T13099. See that task for discussion. Chrome is unhappy with an MFA form submitting to an endpoint which redirects you to an OAuth URI.

Instead, do the redirect entirely on the client.

Chrome's rationale here isn't obvious, so we may be able to revert this at some point.

Test Plan: Went through the OAuth flow locally, was redirected on the client. Will verify in production.

Maniphest Tasks: T13099

Differential Revision: https://secure.phabricator.com/D19177

resources/celerity/map.php

@@ -502,6 +502,7 @@ return array(
     'rsrc/js/core/behavior-phabricator-nav.js' => '836f966d',
     'rsrc/js/core/behavior-phabricator-remarkup-assist.js' => 'acd29eee',
     'rsrc/js/core/behavior-read-only-warning.js' => 'ba158207',
+    'rsrc/js/core/behavior-redirect.js' => '0213259f',
     'rsrc/js/core/behavior-refresh-csrf.js' => 'ab2f381b',
     'rsrc/js/core/behavior-remarkup-preview.js' => '4b700e9e',
     'rsrc/js/core/behavior-reorder-applications.js' => '76b9fc3e',
@@ -686,6 +687,7 @@ return array(
     'javelin-behavior-project-create' => '065227cc',
     'javelin-behavior-quicksand-blacklist' => '7927a7d3',
     'javelin-behavior-read-only-warning' => 'ba158207',
+    'javelin-behavior-redirect' => '0213259f',
     'javelin-behavior-refresh-csrf' => 'ab2f381b',
     'javelin-behavior-releeph-preview-branch' => 'b2b4fbaf',
     'javelin-behavior-releeph-request-state-change' => 'a0b57eb8',
@@ -934,6 +936,10 @@ return array(
       'javelin-dom',
       'phabricator-keyboard-shortcut',
     ),
+    '0213259f' => array(
+      'javelin-behavior',
+      'javelin-uri',
+    ),
     '04b2ae03' => array(
       'javelin-install',
       'javelin-util',

src/applications/oauthserver/controller/PhabricatorOAuthServerAuthController.php

@@ -172,9 +172,33 @@ final class PhabricatorOAuthServerAuthController
         ));
 
       if ($client->getIsTrusted()) {
-        return id(new AphrontRedirectResponse())
-          ->setIsExternal(true)
-          ->setURI((string)$full_uri);
+        // NOTE: See T13099. We currently emit a "Content-Security-Policy"
+        // which includes a narrow "form-action". At the time of writing,
+        // Chrome applies "form-action" to redirects following form submission.
+
+        // This can lead to a situation where a user enters the OAuth workflow
+        // and is prompted for MFA. When they submit an MFA response, the form
+        // can redirect here, and Chrome will block the "Location" redirect.
+
+        // To avoid this, render an interstitial. We only actually need to do
+        // this in Chrome (but do it everywhere for consistency) and only need
+        // to do it if the request is a redirect after a form submission (but
+        // we can't tell if it is or not).
+
+        Javelin::initBehavior(
+          'redirect',
+          array(
+            'uri' => (string)$full_uri,
+          ));
+
+        return $this->newDialog()
+          ->setTitle(pht('Authenticate: %s', $name))
+          ->setRedirect(true)
+          ->appendParagraph(
+            pht(
+              'Authorization for "%s" confirmed, redirecting...',
+              phutil_tag('strong', array(), $name)))
+          ->addCancelButton((string)$full_uri, pht('Continue'));
       }
 
       // TODO: It would be nice to give the user more options here, like

webroot/rsrc/js/core/behavior-redirect.js

@@ -0,0 +1,9 @@
+/**
+ * @provides javelin-behavior-redirect
+ * @requires javelin-behavior
+ *           javelin-uri
+ */
+
+JX.behavior('redirect', function(config) {
+  JX.$U(config.uri).go();
+});