How to Unlock/Crack Premium Features of Android App (ARR – Part 4)

    In our Android App Reversing Using Android Phones Series we have discussed about its introduction , how to remove banner ads and extending the trial period so far. In today’s article we will  be discussing to Unlock/crack Premium Features of Android App. Without any delay let’s start:

    Note: This tutorial will be more difficult and advance than previous one.

    Unlock/Crack Premium Features of Android App

    TARGET: Sensor Alarm
    METHOD: Reversing Smali Codes and editing resources
    DIFFICULTY:  Advanced

    Step 1:

    Before starting first lets note down the Locked features and the pop-up message.

    Locked Features:

    • Camera
    • Temperature
    • Phone Number – SMS
    • Phone Number – Call

    Pop-up Message:

    Step 2:

    Start Apktool and select “Decompile All” Option

    Step 3:

    Once decompile process finish go to following folder:
    Sensor Alarm Free_src\smali\com\oceansoftware\sensoralarm_free

    This is the main folder where we can find all our relevant codes to reverse. Now search for the string “Please buy Paid Version” with the help of “aGrep” app.

    We find this string inside “MainActivity.smali”

    Step 4:

    Now go to the first set of Alert message code in “MainActivity.smali”. To open, find and edfit we use our next app called “920 Text Editor”

    Code View:

    Now we know where our Bad Boy Message created and how it will be called so nownext we do is go to the start of whole process which start at here:

    Code View:

    In order to avoid pop-up message we need to break the free version code routine which we can do with the helpof reversing condition Jump code which we find at “.line 535”

    Step 6:

    Now you have to repeat Step-6 three more time in order ti fix three more pop-up message similar file at:

    Now save and go to next .smali file and continue our search for same string and we find one more message in “MainActivity$1$1.smali” file at:

    There is one more message to go inside “MainActivity$17.smali”

    If you dig more inside code i.e condition we were set to jump, then you will notice that we are lucky because because all our jump to the condition’s are working codes for the relevant button action.It means no dead or junk code and the app is not Demo Version.

    How to know whether trial of free app is having only Demo Codes?

    • There is no conditional jump in such case before start pop-up code.
    • If there has conditional jump then its land over Error Message i.e for no action and return void

    Step 7:

    Now lets modify some of resources to give pro version look to this app

    Start with changing Launcher icon and this we can do simply by:

    Go to res\drawable-mdpi  folder and interchange the name of “app_icon_free.png” to “app_icon.png”

    Note: This will not the case in all app. Many Trial and Free app not include full version component.

    Now we are going to change the name of app from “Sensor Alarm Free” to “Sensor Alarm” and this can be done by:
    Go to res\value then open “strings.xml” and edit as follow:

    Step 8:

    Now all done and go for Recompile, Zipalign and Sign the apk.

    This will be our last post on Android app reversing. If you want any further post on this series kindly comment below and also mention what do you want. To be updated about our post please allow notification and do like our facebook page

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