Root Access

10:19 PM

I'm trying to reverse-engineer Microsoft's JS code for opening the Windows Store app when you open a Store page in the web browser. It's at assets.onestore.ms/cdnfiles/…

I think I've determined what it does. It analyzes the user agent to determine how to open the Windows Store app or its equivalent (depending on whether it's a Windows 10 device, Xbox One, Windows Phone device, etc.), and if so, constructs and injects a <meta> tag into the webpage's DOM that instructs the browser to open the appropriate app.

<meta name="ms.opennativepdp" content="ms-windows-store:[trimmed]">

@BenN?

Avery

@djsmiley2k arguable

bwDraco

Now that is a clever code snippet.

(inspired by superuser.com/questions/1238282/lanovo-battery-management/…)

Ben N

That JavaScript file itself doesn't appear to do the meta tag creation, but it does return some info on whether/how it would be appropriate to generate a store link

The store is opened because the ms-windows-store protocol is registered to that app

Oh wait

It does indeed create the meta tag if appropriate, my mistake

bwDraco

Seen code like this before, @BenN? Not a JS guru, but can superficially read JS code.

You know there's an online JS beautifier, right?

Ben N

Yeah, I used that but missed the meta creation because that bit was offscreen to the right

bwDraco

10:31 PM

I had to examine the source code of the page as rendered in the Firefox dev tools to find the <meta> tag.

Ben N

I can't recall a specific code fragment I've seen that analyzes the user agent, but I'm sure they're used for various things around the web

e.g. download sites often suggest a version appropriate for the client OS, though that check could be done on the server

bwDraco

oneStoreUserAgent = function() {
        var n = window && window.navigator && window.navigator.userAgent && window.navigator.userAgent.toLowerCase && window.navigator.userAgent.toLowerCase() || null;
        return {
            isFromThresholdDevice: function() {
                return n && (n.indexOf("windows nt 6.4") >= 0 || n.indexOf("windows nt 10") >= 0) && n.indexOf("xbox") < 0 && n.indexOf("arm") < 0
            },
            isFromWinPhone10Device: function() {
                return n && (n.indexOf("windows phone 10") >= 0 || n.indexOf("windows nt 10") >= 0 && n.indexOf("arm") >…

Google says this is my user agent:

> Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0

(Firefox Developer Edition 56.0b12 on Windows 10 x64)

...wait a sec. Just updated Firefox and I get the Photon interface :o

> Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0

What in Oblivion...

(sadly, this means Greasemonkey is now broken :( )

I'm going to force-enable legacy extensions.

I seriously hope Greasemonkey can be updated for Firefox 57 soon.

(At least this is the only XUL/XPCOM extension left on my Firefox installation...)

It'll take me a long time to get used to the Photon interface.

TL;DR: Firefox Developer Edition on my main laptop has updated to version 57, resulting in unexpected and massive changes.

I realize that extensions.legacy.enabled = true is not a supported configuration for Firefox 57, and legacy extensions can break without warning in future updates. I seriously need to see an update for Greasemonkey soon.