Xctf mobile--app3 problem solving

1. Download it and find that .ab file ..ab The file is an Android backup file , May be encrypted , No encryption here

download android-backup-extractor

Execute... In folder

java -jar abe.jar unpack app3.ab app3.tar

  obtain bask.apk,.db file , take apk Drag the file into jadx in

2.

 3. Yes a() Function to analyze

Loaded the database , And then I created one a The object of , So you can check this class

Follow up the algorithm step by step

 

 4. The code comes to idea, newly build java, Modify and run . obtain ”ae56f99“

5. Use SQLite Open database （ There are pits here. ）

  Be sure to choose 3 , Because the version is given in the code

Open the data

It looks a bit like base64 encryption

 

summary ： The topic is not difficult, but it involves a lot of things , The code is tedious . During decompilation ,jadx Some of the code did not decompile successfully ,jeb Sure .