Apps/Security

The intent of this page is to provide some background for how security works in B2G and Desktop/Android OpenWebApps. The target audience for this page is (at least for now) primarily people working on implementing B2G and the Open Webapps runtimes. Over time we should improve the pieces that affect web developers such that they can be used as developer documentation.

Note: This is the official reference for the Apps and FirefoxOS Security Model. Please do not edit this page without first discussing changes in dev-webapps@lists.mozilla.org

Introduction

The open web application security and privacy model spans a wide variety of use cases, from typical web content to system-critical applications. As such, a one-size-fits-all security model won't work. Instead we need a range of options that balance out the flexibility and common design patterns for web applications while mitigating the additional risks that come with exposing sensitive APIs. Additionally, providing users as-necessary insight into app use of their data helps them make more informed risk/reward decisions as they install apps and grant permissions.

Discussion and Resources

List of webAPIs and corresponding security discussions: WebAPI

Implementation tracking bug basecamp-security

Installation and updates: Gaia/System/Updates

B2G OS and process security model: B2G/Architecture/Runtime_Security

Foundational Principles

• Maintain core strengths and flexibility of the web
• Protect the security and privacy of the user
• Protect the device from poorly written & malicious applications
• With additional privileges come additional responsibilities for the developer and app store
• User choice and control - treat the user with respect and present them with choices that allow them to make informed decisions. See our privacy operating principles [1], specifically "Real Choices."

Definitions

Explicitly granted permissions

Permissions that need to be enumerated in the manifest and require user consent at "time of use" to enable, whether via a prompt or an in-content user mediated UI. The user can also inspect and modify the explicit permissions for any app via the permissions manager. When the user is prompted for explicit permissions, they need to be informed what is requested, why it's requested, and how the app will use data obtained through this permission.

Implicitly granted permissions

Permissions which are enumerated in the manifest and granted to that type of application without requiring any user interaction. The user may be able to inspect, but not modify, the implicit permissions that an app requests via the permissions manager.

Data Usage Intention

Apps can make a commitment to users about their intended uses of data collected through a given API (for which the user is grants a permission). This is a short string that reflects to users what risk might surface by granting an app permission to use the given API. Users can leverage this Usage Intention to decide whether the value provided by the app is worth the risk or not. Usage Intentions are attached to permissions as an annotation of not only why the permission is needed, but what the app will do with the data.

Types of applications

There are 3 types of installed application. In additional, many webAPIs are also exposed to regular web content, so that category is included here for context.

Normal web content

Not a type of application per our definition of installed apps, but part of the WebAPI security continuum and so discussed here.

• No app store involved
• No manifest or installation experience
• No restrictions on origin or transport (i.e. HTTPS not required)
• All explicit permissions are requested at runtime, not persisted by default
• Most permissions requested via web intents

Installed web application

Unauthenticated applications provide a manifest, and can optionally be obtained through an app store.

• No restrictions on transport but limited to one app per origin (though an app may load assets and code from other origins).
• Installation experience with permissions being opt-in at install and runtime, limited to permissions enumerated in the manifest.
• No app store code reviews as they serve no purpose (app can change anytime without user or reviewer consent).
• No SSL indicators, so trust is limited only to content user is willing to share with any website, and maximum privileges are likewise limited to what is available to normal web content.
• All explicit permissions are requested at runtime, showing user the app's data usage intentions, not persisted by default.
• Most permissions requested via web intents
• Same origin enforced

Installed privileged application

Authenticated application approved by an app store. Equivalent in functionality and security to apps on other mobile platforms.

• App is comprised of an explicit list of assets contained in a zip package.
• App is approved by app store after a code review or some equivalent risk management process.
• App store signs the app manifest which contains the list of assets and their corresponding hashes.
• At install app assets are verified & remain stored locally in package.
• Require a Content Security Policy to mitigate content injection attacks and maintain application integrity.
• All explicit permissions are requested at runtime, showing user the app's data usage intentions, and persisted by default.
• User can monitor permission state and change app permissions via consistent permission notification UI
• Privileges granted are limited to explicit list of application assets; we must enforce security boundaries between privileged code and any unprivileged content that the app may also load.
• No same-origin restrictions for app content; same origin still enforced for non-app content.

Why create a "privileged" application type?

Some permissions are sensitive enough that we don't want just any webapp to get access to it. For example, the DeviceStorage API lets a website delete all the pictures in the user's "pictures folder". The API implementation does ask the user for permission before doing this, however we don't feel that it is enough protection for the user if the only thing standing behind the user and 10 years of lost pictures is a simple "do you want to allow this" dialog.

There are also some APIs that are too hard to explain to the user what consequences approving a certain permission would have, such as raw TCP socket access. For these we can't rely on users making well informed choices and so we need an alternative solution.

To support this we are also supporting a security model where the store takes on the responsibility of ensuring that an app won't behave maliciously with the permissions that it is granted. So for example the store takes on the responsibility of ensuring that an app won't use TCP sockets to scan for data on internal networks and save it on the developers website. And the store makes sure that an app won't delete all the user's pictures even if the user says ok to granting the app permission to use the DeviceStorage API. At least not without making it abundantly clear to the user that that is what will happen, and gives the user plenty of room for error.

Several mechanisms are used to enable to store to do this:

• The app will have to be reviewed by the store. Including reviewing all of the code that makes up the app.
• The app will be signed by the store to ensure that hacking the store website doesn't allow a hacker to install arbitrary content on users devices.
• The app will use a CSP policy to harden the app itself against bugs which would allow an attacker to inject code into the app. This will also make reviewing the app easier.

Default CSP policy

The CSP policy applied to all privileged and certified apps is:

default-src *; script-src 'self'; object-src 'none'; style-src 'self'

This puts the following restrictions on pages in privileged apps:

• Scripts can only be loaded from the package.
• Scripts can not use data:-URIs
• Inline scripts can not be used
• eval() can not be used. Neither can eval-like functions like setTimeout or "new Function". setTimeout can still be used as long as the first argument is a Function object rather than a string.
• onXXX attributes can't be used in the markup of pages. You can still write javascript code like myelement.onXXX = someFunction; as long as you don't assign onXXX to a string, but rather to a Function object.
• <object>, <embed> and <applet> are fully disabled. In other words, plugins won't work at all. Including flash.
• CSS can only be loaded from the package. Inline CSS is however allowed.

This does not restrict any of the following:

• <iframe>s can still point to any URL.
• Images can still be loaded from anywhere. Including when loaded using an <img> element, when using CSS background images or when using other types of CSS images.
• Media (audio and video) can still be loaded from anywhere.
• Network connections can still be opened anywhere using data-centric APIs like XMLHttpRequest or WebSocket.

There is no way for privileged apps to relax this policy. However we may in the future add the ability for packaged apps to define their own CSP policies, in which case that would allow apps to apply more restrictive policies. However such policies would be merged with the above policy which means that it still wouldn't allow the app to relax the policy.

Certified application

This category is reserved for apps that require approval by carrier or OEM due to risk of device corruption or risk to critical functionality. These include apps such as the system settings app, default dialer (to ensure emergency services are always accessible), core radio and power management, etc. Not intended for 3rd party applications. Similar to Privileged apps, except:

• All permissions are implicit.
• User cannot modify permissions (as it could break the device; ex. disable settings permission for the settings app)
• Approval of certified apps is limited to explicit list of authorized app stores.
• Require the same Content Security Policy as Privileged apps
• Not a common application type; reserved only for critical applications

Application Scope

Foundational assumption was that there was only one app per domain. This is because an origin is effectively the only security boundary in the browser, and determining the security implications of allowing apps with different permissions on the same domain is a time consuming exercise for the 1.0 timeframe.

Note that privileged and certified apps have their own unique origin via the app:// scheme.

Permissions

This sections describes the permission model for applications.

Extended permissions

Applications can be granted additional privileges on top of the ones granted to normal websites. By default an application has no permissions on top of the ones normal webpages have. In order to get additional permissions, the first step is for the app to enumerate the additional permissions it wants in the application manifest.

For each additional permission that an app wants, the manifest has to explicitly enumerate that permission along with a human-readable description of why the app wants access to that permission. This description will be surfaced at various points in the UI, and is also used when the app is reviewed.

An example of a fragment of a manifest:

permissions: {
  browser: {
    description: "To enable showing web pages";
  };
  "wifi-information": {
    description: "To alert you about unencrypted wifi networks in your area";
  }
}

Privileged-app-only Permissions

Some permissions are sensitive enough that we don't want to just hand them to any app. For example a permission which enables pages to read or modify pictures from the users picture folder is very sensitive. For such an API we in addition to requiring the app to enumerate the permission in the app manifest, require that the app is a "Privileged App". See details about this in the section for Privileged Apps below.

Permission Prompts

Just because a permission is enumerated in the manifest doesn't mean that an app will be automatically granted that permission at time of installation. For many APIs, like the wifi-information API, enumerating the permission in the manifest simply means that the app can attempt to use it. When used, the user will be prompted and asked if it's ok to grant the permission to the app. During this prompt, the description provided in the manifest will be displayed to the user. However it will be displayed in such a way that it is clear that the description comes from the app developer, and not from B2G itself.

The overall flow will be:

• All permissions prompts are at runtime, at the time of the corresponding API request
• User may be able to review permissions which may be requested at install time via a pulldown, but cannot set them
• Implicit permissions for each application type are not visible or user controllable (classified as low-risk)
• Permissions for high risk APIs are prompted for at runtime with a corresponding rationale (data usage intention) for the request
• Permissions that could compromise the system are available only to certified apps and therefore never prompted for
• Full details of implicit vs explicit permissions for each WebAPI are available here: https://wiki.mozilla.org/WebAPI

Implicit access

Not all permissions will result in the user getting prompted when the permission is first used. In some cases it's very hard to describe to the user what granting the permission means.

In this situation we can't rely on the user to make the security decision. Instead we will have to rely on a technical code-review of the app before it is published in a store to ensure that the app doesn't do anything it shouldn't with the extended permission. See the "Privileged apps" section above for how this works.

In this situation access is granted implicitly at install time.

Open question: Should we enable users looking at the list of prompted and implicit permissions at the time of installation?

access property

For some APIs there is an additional "access" property which allows specifying if the app wants read, write or create access. This looks like:

permissions: {
  contacts: {
    description: "To find friends to send your awesome high-scores to.";
    access: "readwrite";
  };
}

Valid values for the access property are:

• "readonly": Ability to read data and be notified about changes to data. No ability to write data at all.
• "createonly": Ability to create new data. Not read, modify any existing data.
• "readcreate": Ability to read existing data as well as create new data. No ability to modify existing data.
• "readwrite": Full ability to read and modify any data.

In the above, deleting existing data counts as modifying it.

These access levels aren't surfaced to the user at all. They are only there as a level of protection and to help during the code review of the app to determine what they need to look for while reviewing an app. So for example in an app which is requesting "createonly" access to the Contacts API doesn't have to be reviewed to see if it is doing anything unexpected with read contacts information (such as save it to the server without first asking the user), since the app can't ever read contact information.

But even for an app which requests "readwrite" access to the Contacts API, as soon as the app performs a reading or writing operation B2G will prompt the user about permitting access, and if the user grants access, full read and write access will be granted. There is no need for additional prompts assuming that the user checks the "remember this decision" checkbox.

Open Question: We could surface in the prompt which of the above four types are being requested. It wouldn't increase the number of prompts that we have, but it would mean having to deal with what happens if the access changes for example from "readonly" to "readcreate" during an update.

Data Usage Intentions

The data usage intentions (provided by apps as a rationale for a permission) can serve many purposes to help users with choice and control over their data.

On the Hook

Apps that make promises via usage intentions have essentially provided assurance to the user that their data will be used in a certain way. If it turns out the app developers use the data for another purpose (say actually recording Stashy photos and posting them on a public twitter feed), users have a clear way to explain how the app is operating deceptively.

Pre-Validation with Privacy Policies

Many apps will have a privacy policy. An app store has the opportunity to pre-screen apps based on the usage intentions in their manifest and the privacy policy they provide. So long as the two are consistent, users have a commitment from the app about what it intends to do with their data. Apps that are not consistent or vague can be rejected from an app store.

Auditing

To provide a "trail of activity", B2G or other app runtime could additionally maintain a capability-access log for each app that keeps track of requests for capabilities and the usage intentions over time. That way a curious user could analyze the log to see how often an app used a permission, why it used it, and perhaps help illustrate abuse of their consent.

Network access

Network access is assumed as an implicit permission for all apps (as it seems strange to prevent access to something all web content normally has). However the issue of network consumption has been raised as a valid concern.

Its not clear this is an issue for the security model to solve however, and would be better solved via an explicit consumption API that can help the user manage and limit resource utilization. Considered out of scope for the security model in general.

Background Apps

Apps running in the background may trigger permission requests. Since app requests should be in context of the user's interaction with the app, we should suppress any permission requests for non-foreground apps. It is up the developer to properly surface permissions requests while the app is interacting with the user.

Background Services

Services need to be certified apps as they have no way of surfacing permission requests to users since they have no UI. This means we should minimize the set of use cases that absolutely require true services.

Power User

Power users should be able to override the default trust roots to allow them to install arbitrary apps as privileged or certified. This is highly dangerous and should include a correspondingly strong disclaimer or equivalent workflow.

Same Origin Policy

Same origin policy should not be enforced for certified apps or privileged apps, since each app has its own cookie store. The app would have to declare its intent to bypass same-origin policy.

Application Sandboxing

Data stored per app

Each application runs in as a separate sandbox, meaning that all data stored by an application is separate from all data stored by another application. This includes things like cookie data, localStorage data, indexedDB data and site permissions.

This means that if the user has two apps installed, App A and App B, these apps will have completely different set of cookies, different local data and different permission. This even applies if both of these apps open an <iframe> which point to the same origin. I.e. if both App A and App B open an <iframe> pointing to "http://www.mozilla.org", they will both render the website, however the website will be fetched and rendered with different cookies in the two apps.

A result of this is that if the user logs in to, for example, facebook while using App A, this in no way affects App Bs ability to interact with the users account on facebook. The login cookie that facebook sets when the user logs in using App A is only available in App A. If App B open an <iframe> to facebook, the cookie wouldn't be there and so when App B opens facebook, it receives the facebook login page rather than the users account.

Apps can't open each other

This means that apps can't open other apps by using iframes. If App A creates an iframe with the src set to the URL of App B, this won't actually open App B in the iframe. It will simply open the website located at that URL. It will not use any of App B's cookies and so it will behave no different than as if App B wasn't installed on the user's device.

This applies even for packaged apps (more about them below). If App A tries to open the packaged App B by using an <iframe> pointing to the app:// URL of App B, this will simply fail to load. If this results in a 404, or some other type of error is still to be determined, but it will definitely fail to load. And it will fail in the same way no matter if App B is installed on the user's device or not, as to make it impossible for App A to determine if App B is installed.

The same thing happens if the top-level frame of App A is navigated to a URL for App B. We always know for a given frame which app is opened in it, and so when attempting to load the App B URL in the App A frame, this will behave exactly like the two situations described above. I.e. in no way will App B's resources, like cookies or other local data, be used.

Motivation

There are both benefits and downsides to this approach. The downside is that if the user interacts with the same website through several apps, he/she will have to log in in every app. Likewise, if a website wants to store data locally, and the user interacts with this website in several apps, the data will end up getting duplicated in each app which could be a problem if it's a large amount of data.

The main benefit of this approach is that it's a more stable model. There is no way that several apps could interact with each other through a 3rd party website in unexpected ways such that installing an app causes another app to stop working. When an app is uninstalled there is no way that data for another app could be lost, or that another app will stop working due to functional dependence of the uninstalled app.

There are also large security benefits. A user can safely use his AwesomeSocial app to log in to facebook without having to worry that the SketchGame app can mount any types of attack for getting at the users facebook data by exploiting bugs or other shortcomings in the facebook website.

There are also good privacy benefits. The user can safely install the PoliticalPartyPlus app without having to worry that MegaCorpEmployeeApp will be able to detect that the app was installed or what data it has created.

Sandboxed Permissions

And just like website data is sandboxed per app, so are permission grants. If App A loads a page from http://maps.google.com and that page requests to use geolocation and the user says "yes, and remember this decision for all times", this only means that http://maps.google.com has access to geolocation within App A. If App B then opens http://maps.google.com, that page won't have access to geolocation unless the user grants that permission again.

And just like in the normal browser, permissions are separated by origin. This means that if App A is granted permission to use Geolocation, this does not mean that all origins running in App A have the permission to use Geolocation. If App A opens an <iframe> to http://maps.google.com, then http://maps.google.com still has to ask the user for permission before geolocation access is granted.

To additionally secure applications that open a large set of URLs, such as browsers, we have added a "browserContent flag". The browserContent flag allows each app to have not one, but two sandboxes, one for the app itself, and one for any "web content" that it opens. For example:

Say that the MyBrowser app is loaded from the https://mybrowser.com domain. This is the domain where the scripts and resources are loaded within. The scripts and resources belong to this domain.

Now, if a page in this app creates an <iframe mozbrowser> a different sandbox is created and used for this <iframe>, which is different from the sandbox used by the app - i.e. if this iframe is navigated to https://mybrowser.com, it will result in different cookies being used inside the <iframe mozbrowser>. Likewise, the contents inside the <iframe mozbrowser> will see different IndexedDB and localStorage databases from the ones opened by the app.

This also applies if the MyBrowser app wants to create integration with, for example, google maps, to implement location-based browsing. If the app opens an <iframe> to http://maps.google.com, that will open an iframe which will receive a set of cookies for the http://maps.google.com website. If the user then navigates inside web content area, i.e. inside the <iframe mozbrowser>, to http://maps.google.com, this will use different cookies and different permissions than the top level app.

Another example where this is useful is in a Yelp-like app. Yelp has the ability to visit a restaurant's website directly in the app. By using <iframe mozbrowser> to open the restaurant website, the Yelp app ensures that the restaurant website can't contain an <iframe> pointing back to Yelp's app (which points to http://yelp.com). If it does, the website will only receive the Yelp website, rather than the Yelp app. So there is no way that the restaurant website can mount an attack against the app since the contained Yelp website won't share any permissions or data with the Yelp app.

The security model can be shown in a simple picture

+---------------------------------+
| APP-001                         |---->App-Sandbox
|				  ----->Cookie-A
|				  ----->indexedDBStorage-A
|        			  |
|  +--------------------------+   |
|  + http://maps.google.com   +-------->Internal-Sandbox
|  +--------------------------+   |
|  |			      |   |
|  |			      |-->Cookie-B
|  |			      |-->indexedDBStorage-B
|  |    +------------------+  |   |
|  |    | maps.google.com  |  |   |
|  |    +------------------+---------->iFrame opened in web-app
|  |    |                  |---------->Cookie-C
|  |    |                  |  |------->indexedDBStorage-C
|  |    |                  |  |   |
|  |    |                  |  |   |
|  |    +------------------+  |   |
|  +--------------------------+   |
|				  |
+---------------------------------+




+---------------------------------+
| APP-002                         |---->App-Sandbox
|				  ----->Cookie-D
|				  ----->indexedDBStorage-D
|        			  |
|  +--------------------------+   |
|  + http://maps.google.com   +-------->Internal-Sandbox
|  +--------------------------+   |
|  |			      |   |
|  |			      |-->Cookie-E
|  |			      |-->indexedDBStorage-E
|  |    +------------------+  |   |
|  |    | maps.google.com  |  |   |
|  |    +------------------+---------->iFrame opened in web-app
|  |    |                  |---------->Cookie-E
|  |    |                  |  |------->indexedDBStorage-E
|  |    |                  |  |   |
|  |    |                  |  |   |
|  |    +------------------+  |   |
|  +--------------------------+   |
|				  |
+---------------------------------+

Apps can run content from many domains

As has been discussed above, an app can always contain content from multiple domains. This is exactly like how a website today can create an <iframe> pointing to a different domain.

But just like for websites today, a webpage which contains an <iframe> pointing to a different origin can't reach into that iframe and modify or touch the objects there. And like with normal websites, permissions are separated by origin, meaning that just because a permission is granted to an app, doesn't mean that any <iframe>s that that app opens has access to the same permissions.

Data management

appid/browserContent flag in B2G separate profiles on desktop/android

Application Lifecycle

This section describes the format, installation and updates process for applications.

Delivery mechanisms

B2G will support two formats for distributing apps, "hosted" and "packaged". Hosted apps work much like websites do today in that the resources for the app are located on a webserver and loaded through http. These can be cached for faster startup, but they still generally are delivered a lot like a normal website.

Packaged apps are delivered as a .zip file which contains the resources that the app consists of.

Generally speaking, it's entirely up to the app developer to choose between hosted or packaged apps. There are no differences as far as capabilities goes.

However, there are some APIs that are only available to "Privileged Apps", which currently requires the app to be packaged due to signing requirements. See section below for Privileged apps.

Hosted apps

A hosted app consists solely of an application manifest file on the developer's web server. Often the manifest will also point to an appcache manifest which allows an app to be cashed for faster startup and to enable offline usage, but otherwise doesn't affect the app at all.

From a security point of view, hosted apps work very much like normal websites. When a hosted app is loaded, the URL of the loaded pages are the normal URLs that those pages have on their web server. So to link to a specific page or resource in the app, the same URL is used as when linking to that page or URL on the website.

This doesn't change the fact that hosted apps, like all apps, are subject to the application sandbox described above.

In order to secure that an app really wants to be installed as a web app we have to ensure that it's not possible to trick a website into hosting an application manifest. This is done by requiring that the manifest is served with a specific mime-type, "application/x-web-app-manifest+json". This restriction is relaxed when the manifest app, and thus the app manifest, is same-origin with the page that requested the app to be installed.

Packaged apps

The second distribution format that B2G will support is packaged apps. A packaged app consists of a normal zip file which contains both the manifest and the application resources. When a packaged app is installed, the zip file is downloaded and the manifest is read from a well-known location inside the zip file.

Unlike a hosted app, packaged apps doesn't have an obvious URL that their resources can be loaded from. The way to refer to a resource in a packaged app is by using the app: protocol. The format for a app: URL is as follows

app://identifier/path/within/zipfile/file.html

The identifier is a uuid generated at install time. This identifier will remain constant as long as the app is installed. (Eventually the identifier might become the home domain of the app, but we don't have such a concept yet).

Whenever a resource is loaded using the app: protocol, this will only allow loading resources from the zip file associated with the current app. I.e. if you specify an identifier for another app, it will behave exactly as if you specify an invalid identifier or an identifier for an app which isn't installed.

Relative links within app: works just like relative links within http:. Simply using a URL like <img src="/images/picture.jpg"> will load the image named "images/picture.jpg" in the zip package. You can also use markup like <a href="foo/bar.html"> to refer to a page relative the current page.

Open question: We probably need to allow linking to an app:// page. However we could forbid putting an app:// page in an <iframe>. Other than by other app:// pages of course.

One important thing to note about this is that the app protocol doesn't have a concept of a domain. In other words, packaged apps aren't same-origin with any "normal" websites. This is because we don't know the home domain of the developers or the app. We only know which store was used to install the app.

A result of this is that any time XMLHttpRequest is used to read data from a website, it's considered a cross-origin read and so the website has to support CORS. Eventually we'll want to enable packaged apps having a home domain, but that's not yet supported.

Just like with hosted apps, we want to make sure that a hosting website can't be tricked into hosting a app package. The risk is fairly low even if that could happen since even if the user got an app installed, as mentioned above, that app won't be same-origin with the website that the package came from. However to be safe we still apply the same security restrictions as for hosted apps. I.e. the package has to be served with a specific MIME type, or has to be same-origin with the page installing the package.

More information about why we developed a packaged apps solution is available here: Apps/PackagingProposal

Format for privileged and certified apps

We need an application delivery mechanism that provides assurances on app integrity and authenticity, and also allows for well-defined application & privilege scope enforcement so integrity can be maintained at runtime.

Thus all privileged and certified apps will be in packaged format. This package will be provided to the app store for the review, which will then sign it upon approval. Upon installation, the client will verify that the signature is valid and chains to a privileged app store.

Privileged and certified apps will be accessed via a unique scheme (app://). The domain will correspond to the app id.

App Signing

Definition of the signing format goes here. Signing Service

Updates

A lot of the update model is still being defined. Requirements are being collected here at Gaia/System/Updates

Privileged Application Review Guidelines

We need a set of guidelines that define an acceptable level of security and privacy review for privileged applications. This should include:

• Ensuring that requested permissions are used for the purposes stated (in the permission rationale)
• Use of implicit permissions is appropriate
• Any interfaces between privileged app content and unprivileged external content have appropriate mitigations to prevent elevation of privilege attacks

The store is responsible for reviewing the app to ensure that it doesn't do anything dangerous with the permissions it is granted.

Since the OpenWebApps API allows any website to become a store, only stores approved by B2G will be allowed to install Privileged apps. Our goal is that multiple stores will become approved for installing privileged app, but given how much responsibility is put on the store, we need to ensure that we put agreements in place to protect users before approving a store for being allowed to install privileged apps.

Out of scope for 1.0

Magic button

This is a proposal to used a privileged button that grants access to certain APIs (camera, for example). This button would be located in the app's UI but rendered by the OS. It would have a consistent look & feel, and could not by styled, overlaid or obscured by the app.

Clicking this button would implicitly enable access to the camera. Clicking this button again (or providing a separate stop button) would turn off access again.

This is out of scope for 1.0. We do not have the time to fully understand the design and implementation issues with this approach, but it has a lot of merit and we will investigate it further for a subsequent release.

USB, Bluetooth, and NFC access

… for 3rd party apps. These have not been identified as priority use cases for 1.0 and require substantial research. We will support these in a subsequent release.

Certified apps as a 3rd party use case

We may someday have use cases that require certified 3rd party apps, but at this time all 3rd party apps that have been identified can be effectively implemented as privileged apps from a security and UX standpoint. We have no plans to support 3rd party apps as certified apps.