[SOLVED] How can I tell if an app was purchased using Apple's volume purchase program for education?

How can I tell if an app was purchased using Apple's volume purchase program for education?

I have an app that has been available in the AppStore for a while now.
I can see from the iTunes reports that it's been purchased using Apple's volume purchase program, which is great, however - I would like to know if a certain device is running a volume purchased app or a standard AppStore app.
I tried prying inside the receipt ([[NSBundle mainBundle] appStoreReceiptURL]) but I couldn't find anything informative.
Creating a different bundle ID for this purpose is not an option, and kind of misses the idea of the VPP so, please - don't offer it.
Is there a programatic way to tell if the app was purchased using the VPP?

Solution

You were right to look inside the app receipt for VPP information, but you need to refresh it with the SKReceiptPropertyIsVolumePurchase flag set first:

self.refresh = [[SKReceiptRefreshRequest alloc] initWithReceiptProperties:@{SKReceiptPropertyIsVolumePurchase : @YES}];
self.refresh.delegate = self;
[self.refresh start];

You then get your receipt data in requestDidFinish:

- (void)requestDidFinish:(SKRequest *)request {
    NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
    NSData *receipt = [NSData dataWithContentsOfURL:receiptURL];
    // decode receipt and examine vpp fields here 
}

There are many ways to decode an apple receipt, I find the easiest way is to use Apple's receipt verifier, so I moved the receipt data to a file (receipt-data.der) on my computer:

curl -d "{ \"receipt-data\" : \"$(base64 receipt-data.der)\" }" https://sandbox.itunes.apple.com/verifyReceipt

This showed some interesting new fields:

"organization_display_name": "ACME Bad VPPReceipt Inc."
"receipt_type": "ProductionVPPSandbox"
"expiration_date": "2015-12-10 00:44:22 Etc/GMT"

This is in the sandbox, so results will change when you move to production, but this should be enough to figure out if a given device is vpp or not. If you use Apple's receipt verifier, make sure to change the URL to https://buy.itunes.apple.com/verifyReceipt.