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Re: Adding Web Intents to the Webapps WG deliverables

From: Charles Pritchard <chuck@jumis.com>
Date: Thu, 29 Sep 2011 11:34:25 -0700
Message-Id: <2D76BB30-8145-4468-9768-D6C394264BA0@jumis.com>
Cc: "public-webapps@w3.org" <public-webapps@w3.org>
To: Adrienne Porter Felt <apf@berkeley.edu>
Top posting: in web messaging, we typically set an origin property on events and authors are expected to check that property.

Are your concerns addressed by that practice?

It is an added step, an added nuance. And developers may neglect it. But, if they are neglecting origin, they are just plain leaving security holes.

On Sep 28, 2011, at 12:09 PM, Adrienne Porter Felt <apf@berkeley.edu> wrote:

> Android developers chronically misunderstand and misuse Android Intents, and these mistakes lead to security bugs.  To illustrate how prevalent the confusion is, Erika Chin and I found that 9 of 20 popular Android apps (45%!) contain security vulnerabilities due to misusing Intents.  I've also found these same types of bugs in Google-produced Android applications (the default ones that ship as built-in apps).  I posted examples & details of two real-world applications that exhibit these vulnerabilities: http://www.adrienneporterfelt.com/blog/?p=313.
> It's my hope that Web Intents can be designed to prevent developers from making the same mistakes.
> There are two common types of errors:
> 1)  Android Intents can be used for both inter- and intra-application communication, and developers don't know the difference.  A canonical accident occurs when a developer creates a "unique" action string like foo.bar.xyz and uses it for internal communication.  The problem is that any other application can register for the same action string, even if it's supposedly hard to guess.  This introduces two security bugs.  (1)  The component that receives foo.bar.xyz has been unintentionally made public, since anyone can send that action string to it.  (2)  Another application could register to receive foo.bar.xyz and steal any data associated with it, or simply gain the user's attention away from the original app.
> 2)  The Android OS sends Intents to applications as notifications.  Developers register components to receive these system Intents.  By default, registering for a system Intent makes a component public.  Developers don't realize that these components become public by default, so they don't check that the Intent was really sent by the OS.
> I have two suggestions to prevent these same errors from appearing in Web Intents:
> 1)  Developers need to be discouraged from using Web Intents for internal application communication.  One way to do this is to make it so that Web Intents are only delivered after the user selects a service in a browser popup window.  (Nothing hidden in the background!)  This would be annoying for intra-application communication, so I think developers would avoid it.
> 2)  If a developer registers to receive a Web Intent from the browser (like for a system notification), that component should NOT be invocable by any other application unless it's registered for a second Intent as well.
> Adrienne
Received on Thursday, 29 September 2011 18:34:58 UTC

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