Public Sessions - prompt the user for audioCapture/videoCapture requests

chrome/browser/media/public_session_media_access_handler.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_MEDIA_PUBLIC_SESSION_MEDIA_ACCESS_HANDLER_H_
+#define CHROME_BROWSER_MEDIA_PUBLIC_SESSION_MEDIA_ACCESS_HANDLER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/extensions/extension_install_prompt.h"
+#include "chrome/browser/media/extension_media_access_handler.h"
+#include "chrome/browser/media/media_access_handler.h"
+#include "content/public/common/media_stream_request.h"
+#include "extensions/common/extension_id.h"
+
+// MediaAccessHandler for extension capturing requests in Public Sessions. This
+// class is implemented as a wrapper around ExtensionMediaAccessHandler. It
+// allows for finer access control to audioCapture/videoCapture manifest
+// permission features inside of Public Sessions.
+//
+// In Public Sessions extensions are installed by admin policy hence they can

[Andrew T Wilson (Slow), 2016/12/06 02:49:45]

This is a bit confusing, I'd probably phrase it more like this:

In Public Sessions, apps and extensions are force-installed by admin policy so
the user does not get a chance to review the permissions for these apps. This is
not acceptable from a security/privacy standpoint, so when an app uses the
capture APIs for the first time, we show the user a dialog where they can
choose...

[Ivan Šandrk, 2016/12/06 14:02:39]

Done.

+// freely use the camera and microphone without the user knowing. This is not
+// acceptable from a security/privacy standpoint so we show the user a dialog
+// where they can choose whether to allow the extension access to camera and/or
+// microphone. Note: camera and microphone are used through audioCapture and
+// videoCapture manifest permissions which are limited to platform apps only.
+class PublicSessionMediaAccessHandler : public MediaAccessHandler {
+ public:
+  PublicSessionMediaAccessHandler();
+  ~PublicSessionMediaAccessHandler() override;
+
+  // MediaAccessHandler implementation.
+  bool SupportsStreamType(const content::MediaStreamType type,
+                          const extensions::Extension* extension) override;
+  bool CheckMediaAccessPermission(
+      content::WebContents* web_contents,
+      const GURL& security_origin,
+      content::MediaStreamType type,
+      const extensions::Extension* extension) override;
+  void HandleRequest(content::WebContents* web_contents,
+                     const content::MediaStreamRequest& request,
+                     const content::MediaResponseCallback& callback,
+                     const extensions::Extension* extension) override;
+
+ private:
+  // Helper function used to chain the HandleRequest call into the original
+  // inside of ExtensionMediaAccessHandler.
+  void ChainHandleRequest(content::WebContents* web_contents,
+                          const content::MediaStreamRequest& request,
+                          const content::MediaResponseCallback& callback,
+                          const extensions::Extension* extension);
+
+  // Function used to resolve user decision regarding allowing audio/video.
+  void ResolvePermissionPrompt(
+      content::WebContents* web_contents,
+      const content::MediaStreamRequest& request,
+      const content::MediaResponseCallback& callback,
+      const extensions::Extension* extension,
+      ExtensionInstallPrompt::Result prompt_result);
+
+  // Class used to cache user choice regarding allowing audio/video capture.
+  class UserChoice {
+   public:
+    // Helper function for checking if audio/video is allowed by user choice.
+    bool IsAllowed(content::MediaStreamType type) const;
+    // Helper function which returns true if audio/video wasn't prompted yet.
+    bool NeedsPrompting(content::MediaStreamType type) const;
+    void Set(content::MediaStreamType type, bool allowed);
+    void SetPrompted(content::MediaStreamType type);
+
+   private:
+    bool audio_prompted_ = false;
+    bool audio_allowed_ = false;
+    bool video_prompted_ = false;
+    bool video_allowed_ = false;
+  };
+
+  std::map<extensions::ExtensionId, UserChoice> user_choice_cache_;
+  std::map<extensions::ExtensionId, std::unique_ptr<ExtensionInstallPrompt>>

[Andrew T Wilson (Slow), 2016/12/06 02:49:45]

This is fine, but curious why we don't put this in UserChoice?

[Ivan Šandrk, 2016/12/06 14:02:39]

Seemed better to me to logically separate them.

+      extension_install_prompt_map_;
+  ExtensionMediaAccessHandler extension_media_access_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(PublicSessionMediaAccessHandler);
+};
+
+#endif  // CHROME_BROWSER_MEDIA_PUBLIC_SESSION_MEDIA_ACCESS_HANDLER_H_