我有什么方法可以检测我的应用是否已通过Installous下载？

Question

I know there's a way to check if a in App Purchase has been cracked but, is there any way to check if the app has been downloaded from the App Store?

I mean checking with my App if someone has cracked it or someone has downloaded it from Installous?

Answer 1

The short answer: no, not really. For one, I don't think Apple provides a way to do this, though I could be wrong. Even if they did, though, it may not do much good.

Let's assume some function named VerifyAppStorePurchase exists that contacts Apple's servers and confirms the current user has legally purchased your app. Somewhere in your app, you have code like this:

if(!VerifyAppStorePurchase()) {
    exit(-1);
}

This will compile to something like this (But note this is x86 assembly and not arm, so it's not exactly what you'd see on an iOS device. The same concept applies, though.):

    pushl   %ebp
    movl    %esp, %ebp
    subl    $24, %esp
    call    _VerifyAppStorePurchase
    testl   %eax, %eax
    je  L7
    # <snip app code here>
L7:
    movl    $-1, (%esp)
    call    _exit

I can see at least two ways a cracker could disable this check:

• Replace the first two bytes of the call instruction with a jump past the check—a two byte patch
• Replace the jump to the call to exit with a couple nop instructions—again, a two byte patch

Signature verification would normally stop this, but jailbroken iPhones are happy to run unsigned code, so there's nothing stopping a sufficiently motivated cracker from modifying your app to disable any extra checks you add.