Friday, November 5, 2010

more android license validation

in a previous post i mentioned a method of cracking the android market license validation library (lvl). there are apparently multiple ways of deploying the android license verification library. most of the time i see com/android/LicenseChecker.smali, com/android/LicenseValidator.smali, etc. recently i found an app that only used ILicensingService and ILicenseResultListener and my normal method of cracking could not be applied.

after about 30 minutes of illuminating reading over binders and parcels work on the android developer site, i came up with this solution: inside ILicenseResultListener$Stub.smali, in the method onTransact(ILandroid/os/Parcel;Landroid/os/Parcel;I)Z simply return true at the top, like this:
.method public onTransact(ILandroid/os/Parcel;Landroid/os/Parcel;I)Z
    .locals 6
    .parameter "code"
    .parameter "data"
    .parameter "reply"
    .parameter "flags"
    .annotation system Ldalvik/annotation/Throws;
        value = {
    .end annotation

    const/4 v4, 0x1

    # lnote: never do binder.ontransact
    # just always return true :)
    return v4

if you want to try to improve on this solution, it help to look at the actual java source here:

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