darkCON CTF - ezpz (48 solves / 470 points)

tl;dr: Just run adb logcat for the flag.

Solution

On running the app this is the UI which only have input text but doesnt do anything other than the dancing submit button xD

My Image

So on reversing the apk we get some java files by following the source code for flag checking in MainActivity.java we can see that it is checking the input with YEET variable which from whyAmIHere class so following the whyAmIHere file we get that the flag is actually fetched from firestore (kinda of db in firebase) and is forwarded to Log.d() which is typical logger in android with TAG as TypicalLogcat.

public class whyAmIHere  {

    public String[] isThisWhatUWant() {
        final String[] justAWaytoMakeAsynctoSync = {""};
        FirebaseFirestore freeOnlineDatabaseYEEEET = FirebaseFirestore.getInstance();
        freeOnlineDatabaseYEEEET.collection("A_Collection_Is_A_Set_Of_Data").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
            @Override
            public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                    for(DocumentSnapshot snapshot : queryDocumentSnapshots){
                        justAWaytoMakeAsynctoSync[0] = snapshot.getString("Points");
                        Log.d("TypicalLogcat",justAWaytoMakeAsynctoSync[0]);
                    }
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                justAWaytoMakeAsynctoSync[0] = "Something Failed,Maybe Contact Author?";
            }
        });
        return justAWaytoMakeAsynctoSync;
    }

}

So by using adb we can check for TypicalLogcat from logcat debug message and we get the flag.

D:\Useless Tools\Geneymotion\tools>adb logcat | FINDSTR TypicalLogcat
02-21 13:52:11.599  2162  2162 D TypicalLogcat: darkCON{d3bug_m5g_1n_pr0duct10n_1s_b4d}