一份礼物.apk的逆向分析
文章来源：齐鲁师院网络安全社团
事情起因是震惊全国大学生的1013事件！！！
刚好看到社团群里在讨论这个，于是就发挥专业特长分析一下
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,这不就是 "送给最好的ta.apk" 吗?
使用Android killer或apk改之理分析一下,这里使用Android Killer:
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。这个mc.mp3就是播放的广告音频了。
剩下的就简单了,虽然lua文件是加密过的,通过分析java代码,发现加密方式也没变,依旧使用/lib/armeabli-v7a/libluajava.so加密,因此使用ida7.0(x32)对这个文件逆向分析:
查找到在luaL.loadbufferx里面有对文件解密的过程
这里直接拿pcat大佬写的解密脚本:
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()
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 = "\230\143\146\228\187\1829.0"
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 = "\230\131\138\228\184\141\230\131\138\229\150\156 \230\132\143\228\184\141\230\132\143\229\164\150"
L2.layout_height = "match_parent"
L2.layout_width = "match_parent"
L2.background = "#88888888"
L2[1] = L3
L0[1] = L1
L0[2] = L2
return L0
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,大概就是读取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
恶搞一时爽，但是也要有度。
万一下一次是个带病毒的文件呢？
对了 解决方案-----------关掉进程或关机！
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