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XPOSED魔改一：获取特征

写在前面

受这篇文章——《定制Xposed框架》启发，决定自己也尝试一下。

尝试的过程中发现，文章写得太“简约”了，基本上毫无细节，后人想下手或复现非常困难，对Xposed各模块之间的关系也没有介绍，有点“干”，不易于理解，于是有了此文。

本文细节非常多，相当于手把手，篇幅过长所以分拆成三篇：

  1. XPOSED魔改一：获取特征
  2. XPOSED魔改二：编译源码
  3. XPOSED魔改三：更改特征

话不多说，进入正题，既然想要抹掉XPOSED框架的特征，那么首先得知道XPOSED框架有哪些特征，才能有的放矢、对症下药。

准备环境：选择XPOSED版本v89

从Xposed官方发布频道得知，sdk27版本（也就是安卓8.1）的Xposed还是beta的状态：

最新的正式版是sdk25（也就是安卓7.1），已经是2017年的了：

当然最重要的还是Github主页上开源的版本只到v89，也就是安卓7.1；而不是安卓8的v90系列。

准备环境：选择谷歌原版镜像7.1.2

Xposed今后应该也不会更新了，我们以android-7.1.2_r8版本来进行编译。

首先只需要收集特征，我们先下载其线程的谷歌镜像进行刷机即可：

在Link上右键复制链接地址，可以直接黏贴到国内环境的浏览器里下载的，也可以直接wget：

# wget https://dl.google.com/dl/android/aosp/sailfish-n2g47o-factory-f2bc8024.zip
--2020-03-29 10:18:25--  https://dl.google.com/dl/android/aosp/sailfish-n2g47o-factory-f2bc8024.zip
Resolving dl.google.com (dl.google.com)... 203.208.43.101, 203.208.43.102, 203.208.43.104, ...
Connecting to dl.google.com (dl.google.com)|203.208.43.101|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1914505658 (1.8G) [application/zip]
Saving to: ‘sailfish-n2g47o-factory-f2bc8024.zip’

sailfish-n2g47o-factory-f2bc 100%[============================================>]   1.78G  10.5MB/s    in 3m 25s  

2020-03-29 10:21:51 (8.92 MB/s) - ‘sailfish-n2g47o-factory-f2bc8024.zip’ saved [1914505658/1914505658]

下载完成后进行解压：

# unzip sailfish-n2g47o-factory-f2bc8024.zip 
Archive:  sailfish-n2g47o-factory-f2bc8024.zip
   creating: sailfish-n2g47o/
  inflating: sailfish-n2g47o/radio-sailfish-8996-012901-1702171013.img  
  inflating: sailfish-n2g47o/bootloader-sailfish-8996-012001-1703151359.img                                       
  inflating: sailfish-n2g47o/flash-all.bat                                                                        
  inflating: sailfish-n2g47o/flash-all.sh                                                                         
 extracting: sailfish-n2g47o/image-sailfish-n2g47o.zip                                                            
  inflating: sailfish-n2g47o/flash-base.sh

如果电脑里没有安装fastboot，可以先下载一下：

# wget wget https://dl.google.com/android/repository/platform-tools-latest-linux.zip
--2020-03-29 10:24:28--  http://wget/
Resolving wget (wget)... failed: Name or service not known.
wget: unable to resolve host address ‘wget’
--2020-03-29 10:24:29--  https://dl.google.com/android/repository/platform-tools-latest-linux.zip
Resolving dl.google.com (dl.google.com)... 203.208.50.167, 203.208.50.164, 203.208.50.174, ...
Connecting to dl.google.com (dl.google.com)|203.208.50.167|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: https://dl.google.com/android/repository/platform-tools_r29.0.6-linux.zip [following]
--2020-03-29 10:24:29--  https://dl.google.com/android/repository/platform-tools_r29.0.6-linux.zip
Reusing existing connection to dl.google.com:443.
HTTP request sent, awaiting response... 200 OK
Length: 8254604 (7.9M) [application/zip]
Saving to: ‘platform-tools-latest-linux.zip.1’

platform-tools-latest-linux. 100%[============================================>]   7.87M  9.76MB/s    in 0.8s    

2020-03-29 10:24:30 (9.76 MB/s) - ‘platform-tools-latest-linux.zip.1’ saved [8254604/8254604]

FINISHED --2020-03-29 10:24:30--
Total wall clock time: 2.3s
Downloaded: 1 files, 7.9M in 0.8s (9.76 MB/s)

解压并将fastboot命令加入当前终端的路径中去：

# unzip platform-tools-latest-linux.zip
inflating: platform-tools/systrace/catapult/systrace/systrace/__init__.py  
inflating: platform-tools/systrace/catapult/systrace/systrace/monitor_unittest.py  
inflating: platform-tools/systrace/catapult/systrace/systrace/LICENSE  
inflating: platform-tools/systrace/catapult/systrace/systrace/tracing_controller.py  
inflating: platform-tools/systrace/catapult/systrace/systrace/update_systrace_trace_viewer.py  
inflating: platform-tools/systrace/catapult/systrace/systrace/prefix.html  
creating: platform-tools/systrace/catapult/systrace/systrace/tracing_agents/
inflating: platform-tools/systrace/catapult/systrace/systrace/tracing_agents/walt_agent_unittest.py  
inflating: platform-tools/systrace/catapult/systrace/systrace/tracing_agents/__init__.py  
...
...
# pwd    （获取当前路径）
# export PATH=$PATH:/当前路径/platform-tools/

测试一下当前终端中有fastboot命令了么？如果有，会打印出一堆帮助信息。

# fastboot -h
usage: fastboot [OPTION...] COMMAND...

flashing:
 update ZIP                 Flash all partitions from an update.zip package.
 flashall                   Flash all partitions from $ANDROID_PRODUCT_OUT.
                            On A/B devices, flashed slot is set as active.
                            Secondary images may be flashed to inactive slot.
 flash PARTITION [FILENAME] Flash given partition, using the image from
                            $ANDROID_PRODUCT_OUT if no filename is given.

basics:
 devices [-l]               List devices in bootloader (-l: with device paths).
 getvar NAME                Display given bootloader variable.
 reboot [bootloader]        Reboot device.

locking/unlocking:
 flashing lock|unlock       Lock/unlock partitions for flashing
 flashing lock_critical|unlock_critical
                            Lock/unlock 'critical' bootloader partitions.
 flashing get_unlock_ability
                            Check whether unlocking is allowed (1) or not(0).

将手机进入bootloader模式，这里以pixel一代sailfish为例，刚刚下载的镜像也是专为sailfish这个型号准备的。首先完全关闭手机（可以等关机息屏后再等待一分钟），然后按住音量向下键，再按开机键开机，手机会进入如图状态，就是bootloader模式：

usb线连接到电脑后，可以使用fastboot命令检测到：

如果系统是在VMware里，那么要确保usb口连接到VMware里的Linux系统。

# fastboot devices
FA69P0300560    fastboot

最终就是进入刚刚解压出来的sailfish镜像文件夹，运行其中的flash-all.sh命令即可。

# cd sailfish-n2g47o/
# ./flash-all.sh 
Sending 'bootloader_b' (32380 KB)                  OKAY [  3.792s]
Writing 'bootloader_b'                             (bootloader) Valid bootloader version.
(bootloader) Flashing active slot "_b" 
(bootloader) Flashing active slot "_b" 
OKAY [ 12.260s]
Finished. Total time: 16.250s
Rebooting into bootloader                          OKAY [  0.048s]
Finished. Total time: 0.149s
< waiting for any device >
Sending 'radio_b' (57240 KB)                       OKAY [  6.854s]
Writing 'radio_b'                                  OKAY [  0.951s]
Finished. Total time: 7.991s
Rebooting into bootloader                          OKAY [  0.045s]
Finished. Total time: 0.096s
--------------------------------------------
Bootloader Version...: 8996-012001-1703151359
Baseband Version.....: 8996-012901-1702171013
Serial Number........: FA69P0306926
--------------------------------------------
extracting android-info.txt (0 MB) to RAM...
Checking 'product'                                 OKAY [  0.048s]
Checking 'version-bootloader'                      OKAY [  0.050s]
Checking 'version-baseband'                        OKAY [  0.050s]
Setting current slot to 'b'                        OKAY [  0.405s]
extracting boot.img (24 MB) to disk... took 0.353s
archive does not contain 'boot.sig'
Sending 'boot_b' (24653 KB)                        OKAY [  3.192s]
Writing 'boot_b'                                   OKAY [  0.605s]
archive does not contain 'system.sig'
Sending sparse 'system_b' 1/4 (521196 KB)          OKAY [ 64.041s]
Writing 'system_b'                                 OKAY [  7.893s]
Sending sparse 'system_b' 2/4 (524080 KB)          OKAY [ 66.481s]
Writing 'system_b'                                 OKAY [ 15.006s]
Sending sparse 'system_b' 3/4 (496387 KB)          OKAY [ 60.688s]
Writing 'system_b'                                 OKAY [  7.644s]
Sending sparse 'system_b' 4/4 (32756 KB)           OKAY [  4.007s]
Writing 'system_b'                                 OKAY [  0.996s]
archive does not contain 'system_ext.img'
extracting system_other.img (1641 MB) to disk... took 30.917s
archive does not contain 'system.sig'
Sending sparse 'system_a' 1/4 (520579 KB)          OKAY [ 64.744s]
Writing 'system_a'                                 OKAY [  5.791s]
Sending sparse 'system_a' 2/4 (521193 KB)          OKAY [ 63.390s]
Writing 'system_a'                                 OKAY [  6.042s]
Sending sparse 'system_a' 3/4 (510220 KB)          OKAY [ 61.388s]
Writing 'system_a'                                 OKAY [  5.191s]
Sending sparse 'system_a' 4/4 (128745 KB)          OKAY [ 15.756s]
Writing 'system_a'                                 OKAY [  1.953s]
extracting vendor.img (236 MB) to disk... took 4.279s
archive does not contain 'vendor.sig'
Sending 'vendor_b' (242102 KB)                     OKAY [ 29.721s]
Writing 'vendor_b'                                 OKAY [  7.801s]
archive does not contain 'vendor_other.img'
Erasing 'userdata'                                 OKAY [  6.061s]
mke2fs 1.45.4 (23-Sep-2019)
Creating filesystem with 6509568 4k blocks and 1630208 inodes
Filesystem UUID: 4b251af0-28e0-479e-b726-813ed8a0ed0c
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done   

Sending 'userdata' (4272 KB)                       OKAY [  0.572s]
Writing 'userdata'                                 OKAY [  0.111s]
Rebooting                                          OKAY [  0.050s]
Finished. Total time: 567.899s

安装成功就会出现finished字样，并且手机重启，进入系统。

准备环境：使用SuperSU进行root

貌似Magisk环境与XPOSED是有冲突的，不然不会有[Magisk] Systemless Xposed v89.3/v90.2-beta3 (SDK 21-27)这种产物了，所以幸亏我们选择的是7.1.2，用老牌的SuperSU还是支持的。

SuperSU官网提供的下载已经无法下载了，所以在其他网盘里找到个能用的SR3-SuperSU-v2.82-SR3-20170813133244.zip，用TWRP刷进这个SuperSU就行了。

TWRP则使用这个版本：twrp-3.2.1-0-sailfish.img，先都下载了。

  1. 首先手机进入bootloader状态，这个上文已经讲过；
  2. 使用fastboot命令加载TWRP，
# fastboot boot twrp-3.2.1-0-sailfish.img 
Sending 'boot.img' (30948 KB)                      OKAY [  3.981s]
Booting                                            OKAY [  1.005s]
Finished. Total time: 5.160s
  1. 待TWRP完全开机之后，将SR3-SuperSU-v2.82-SR3-20170813133244.zip推送到/sdcard/目录下：
# adb push SR3-SuperSU-v2.82-SR3-20170813133244.zip /sdcard/
* daemon not running; starting now at tcp:5037
* daemon started successfully
SR3-SuperSU-v2.82-SR3-20170813133244.zip: 1 file pushed, 0 skipped. 21.8 MB/s (6918737 bytes in 0.303s)
  1. 选择Install，浏览到/sdcard/目录下，点选SR3-SuperSU-v2.82-SR3-20170813133244.zip文件，将最下方滑块从最左拖到最右，即开始刷入SuperSU。刷入成功后如图所示。

选择Reboot System→ Do Not Install即可。

准备环境：安装Xposed框架并激活插件

下载安装最新版xposed.installer_3.1.5，下载完安装和打开，然后安装Xposed的底包，具体流程见下图。

安装、重启完成后，须出现“Xposed框架89版已激活”字样，绿色勾勾（而不是红色或黄色）。在Xposed Installer的“下载”模块里找到GraviryBox[N]安装和激活，然后让状态栏文字变成如图绿色康康（原来为白色）。

到这里框架和插件都安装成功并正常使用了。

收集特征：底包详细信息

从手机里把底包抽出来，也就是xposed-v89-sdk25-arm64.zip，应该就是服务器上的https://dl-xda.xposed.info/framework/sdk25/arm64/xposed-v89-sdk25-arm64.zip，解压康康发现里面东西很多。

这个里面最关键的就是安装包文件做了什么，这里只取最关键的康康，其余拷贝证书之类的，心里有数就好：

# cat META-INF/com/google/android/flash-script.sh

##########################################################################################
#
# Xposed framework installer zip.
#
# This script installs the Xposed framework files to the system partition.  该脚本将Xposed框架安装到系统分区
# The Xposed Installer app is needed as well to manage the installed modules. XposedInstaller用来管理模块
#
##########################################################################################

...
...

##########################################################################################

echo "******************************"
echo "Xposed framework installer zip" 框架安装
echo "******************************"

if [ ! -f "system/xposed.prop" ]; then
  echo "! Failed: Extracted file system/xposed.prop not found!"
  exit 1
fi

# 挂载system和vendor分区可读可写
echo "- Mounting /system and /vendor read-write"
mount /system >/dev/null 2>&1
mount /vendor >/dev/null 2>&1
mount -o remount,rw /system
mount -o remount,rw /vendor >/dev/null 2>&1
if [ ! -f '/system/build.prop' ]; then
  echo "! Failed: /system could not be mounted!"
  exit 1
fi

# 检查环境并设置变量
echo "- Checking environment"
API=$(grep_prop ro.build.version.sdk)
APINAME=$(android_version $API)
ABI=$(grep_prop ro.product.cpu.abi | cut -c-3)
ABI2=$(grep_prop ro.product.cpu.abi2 | cut -c-3)
ABILONG=$(grep_prop ro.product.cpu.abi)
XVERSION=$(grep_prop version system/xposed.prop)
XARCH=$(grep_prop arch system/xposed.prop)
XMINSDK=$(grep_prop minsdk system/xposed.prop)
XMAXSDK=$(grep_prop maxsdk system/xposed.prop)

XEXPECTEDSDK=$(android_version $XMINSDK)
if [ "$XMINSDK" != "$XMAXSDK" ]; then
  XEXPECTEDSDK=$XEXPECTEDSDK' - '$(android_version $XMAXSDK)
fi

ARCH=arm
IS64BIT=
if [ "$ABI" = "x86" ]; then ARCH=x86; fi;
if [ "$ABI2" = "x86" ]; then ARCH=x86; fi;
if [ "$API" -ge "21" ]; then
  if [ "$ABILONG" = "arm64-v8a" ]; then ARCH=arm64; IS64BIT=1; fi;
  if [ "$ABILONG" = "x86_64" ]; then ARCH=x64; IS64BIT=1; fi;
fi


# 这一行其实输出更加详细的信息，只是被作者注销掉了
# echo "DBG [$API] [$ABI] [$ABI2] [$ABILONG] [$ARCH] [$XARCH] [$XMINSDK] [$XMAXSDK] [$XVERSION]"

# 只输出了简化版信息，图片中有。
echo "  Xposed version: $XVERSION"

# 如果各种信息不匹配，则输出错误信息
XVALID=
if [ "$ARCH" = "$XARCH" ]; then
  if [ "$API" -ge "$XMINSDK" ]; then
    if [ "$API" -le "$XMAXSDK" ]; then
      XVALID=1
    else
      echo "! Wrong Android version: $APINAME"
      echo "! This file is for: $XEXPECTEDSDK"
    fi
  else
    echo "! Wrong Android version: $APINAME"
    echo "! This file is for: $XEXPECTEDSDK"
  fi
else
  echo "! Wrong platform: $ARCH"
  echo "! This file is for: $XARCH"
fi

if [ -z $XVALID ]; then
  echo "! Please download the correct package"
  echo "! for your platform/ROM!"
  exit 1
fi

# 上面环境监测都通过时，就开始把不同的文件放到相应的位置上去，区分32位和64位。

echo "- Placing files"
install_nobackup /system/xposed.prop                      0    0 0644
install_nobackup /system/framework/XposedBridge.jar       0    0 0644

install_and_link  /system/bin/app_process32               0 2000 0755 u:object_r:zygote_exec:s0
install_overwrite /system/bin/dex2oat                     0 2000 0755 u:object_r:dex2oat_exec:s0
install_overwrite /system/bin/oatdump                     0 2000 0755
install_overwrite /system/bin/patchoat                    0 2000 0755 u:object_r:dex2oat_exec:s0
install_overwrite /system/lib/libart.so                   0    0 0644
install_overwrite /system/lib/libart-compiler.so          0    0 0644
install_overwrite /system/lib/libart-disassembler.so      0    0 0644
install_overwrite /system/lib/libsigchain.so              0    0 0644
install_nobackup  /system/lib/libxposed_art.so            0    0 0644
if [ $IS64BIT ]; then
  install_and_link  /system/bin/app_process64             0 2000 0755 u:object_r:zygote_exec:s0
  install_overwrite /system/lib64/libart.so               0    0 0644
  install_overwrite /system/lib64/libart-compiler.so      0    0 0644
  install_overwrite /system/lib64/libart-disassembler.so  0    0 0644
  install_overwrite /system/lib64/libsigchain.so          0    0 0644
  install_nobackup  /system/lib64/libxposed_art.so        0    0 0644
fi

if [ "$API" -ge "22" ]; then
  find /system /vendor -type f -name '*.odex.gz' 2>/dev/null | while read f; do mv "$f" "$f.xposed"; done
fi

echo "- Done"
exit 0

也就是说该脚本的实质，把确保安装包没有下错，跟系统环境是匹配的，以及把不同的文件放到相应的位置上去。这里我们有了基本的概念，至少我们最终编译出来的可以刷机的包，得包含下列文件，他们最终会被放在系统的system/bin/、system/framework/、system/lib64/位置上。

简单地搜下字符串，可以看到几乎所有的二进制文件中都含有xposed的字符串，我们最终的目标最起码要拿掉xposed的字符串特征。

# grep -ril "xposed" *
META-INF/CERT.SF
META-INF/MANIFEST.MF
META-INF/com/google/android/update-binary
META-INF/com/google/android/flash-script.sh
system/lib64/libxposed_art.so
system/lib64/libart-compiler.so
system/lib64/libart.so
system/lib/libxposed_art.so
system/lib/libart-compiler.so
system/lib/libart.so
system/bin/oatdump
system/bin/dex2oat
system/bin/app_process32_xposed
system/bin/app_process64_xposed
xposed-v89-sdk25-arm64.zip

这些文件的用途及与源码的比对我们下一章再详细介绍。

收集特征：日志输出信息

Xposed插件在运行的时候会输出日志，如下图：

可以提取出来看个完整的：

# cat xposed_error_20200331_150832.log 
03-31 14:06:50.383 I/Xposed  (  713): -----------------
03-31 14:06:50.383 I/Xposed  (  713): Starting Xposed version 89, compiled for SDK 25
03-31 14:06:50.384 I/Xposed  (  713): Device: Pixel (Google), Android version 7.1.2 (SDK 25)
03-31 14:06:50.384 I/Xposed  (  713): ROM: N2G47O
03-31 14:06:50.384 I/Xposed  (  713): Build fingerprint: google/sailfish/sailfish:7.1.2/N2G47O/3852959:user/release-keys
03-31 14:06:50.384 I/Xposed  (  713): Platform: arm64-v8a, 64-bit binary, system server: yes
03-31 14:06:50.384 I/Xposed  (  713): SELinux enabled: yes, enforcing: yes
03-31 14:06:51.426 I/Xposed  (  713): -----------------
03-31 14:06:51.426 I/Xposed  (  713): Added Xposed (/system/framework/XposedBridge.jar) to CLASSPATH
03-31 14:06:52.425 I/Xposed  (  713): Detected ART runtime
03-31 14:06:52.433 I/Xposed  (  713): Found Xposed class 'de/robv/android/xposed/XposedBridge', now initializing
03-31 14:06:52.774 I/Xposed  (  713): Loading modules from /data/app/com.ceco.nougat.gravitybox-1/base.apk
03-31 14:06:52.806 I/Xposed  (  713):   Loading class com.ceco.nougat.gravitybox.GravityBox
03-31 14:06:52.819 I/Xposed  (  713): GB:Hardware: sailfish
03-31 14:06:52.819 I/Xposed  (  713): GB:Product: sailfish
03-31 14:06:52.819 I/Xposed  (  713): GB:Device manufacturer: Google
03-31 14:06:52.819 I/Xposed  (  713): GB:Device brand: google
03-31 14:06:52.819 I/Xposed  (  713): GB:Device model: Pixel
03-31 14:06:52.821 I/Xposed  (  713): GB:Device type: phone
03-31 14:06:52.821 I/Xposed  (  713): GB:Is MTK device: false
03-31 14:06:52.821 I/Xposed  (  713): GB:Is Xperia device: false
03-31 14:06:52.821 I/Xposed  (  713): GB:Is Moto XT device: false
03-31 14:06:52.821 I/Xposed  (  713): GB:Is OxygenOS ROM: false
03-31 14:06:52.822 I/Xposed  (  713): GB:Has telephony support: true
03-31 14:06:52.822 I/Xposed  (  713): GB:Has Gemini support: false
03-31 14:06:52.822 I/Xposed  (  713): GB:Android SDK: 25
03-31 14:06:52.822 I/Xposed  (  713): GB:Android Release: 7.1.2
03-31 14:06:52.822 I/Xposed  (  713): GB:ROM: N2G47O
03-31 14:06:52.822 I/Xposed  (  713): GB:Error logging: false
03-31 14:07:05.189 I/Xposed  ( 1296): GB:Is AOSP forced: false

可以观察到主要涉及的文件也就是/system/framework/XposedBridge.jar，也就是前文中放到/system/framework/的XposedBridge.jar文件，可见XposedBridge.jar文件在Xposed插件的运行中起到了关键的作用。

收集特征：插件开发配置信息

根据官方tutorial，典型的插件开发流程分为：

  • 加入Xposed Framework API
  • 修改AndroidManifest.xml
  • 编写hook代码
  • 将类注册到assets/xposed_init文件中去

比如编写下述java的hook代码，最终效果就是改变系统时钟颜色：

package de.robv.android.xposed.mods.tutorial;

import static de.robv.android.xposed.XposedHelpers.findAndHookMethod;
import android.graphics.Color;
import android.widget.TextView;
import de.robv.android.xposed.IXposedHookLoadPackage;
import de.robv.android.xposed.XC_MethodHook;
import de.robv.android.xposed.callbacks.XC_LoadPackage.LoadPackageParam;

public class Tutorial implements IXposedHookLoadPackage {
	public void handleLoadPackage(final LoadPackageParam lpparam) throws Throwable {
		if (!lpparam.packageName.equals("com.android.systemui"))
			return;

		findAndHookMethod("com.android.systemui.statusbar.policy.Clock", lpparam.classLoader, "updateClock", new XC_MethodHook() {
			@Override
			protected void afterHookedMethod(MethodHookParam param) throws Throwable {
				TextView tv = (TextView) param.thisObject;
				String text = tv.getText().toString();
				tv.setText(text + " :)");
				tv.setTextColor(Color.RED);
			}
		});
	}
}

可以看到引入的包都位于de.robv.android.xposed包中，当然这也是引入Xposed Framework API时被包含进项目的：

repositories {
    jcenter();
}

dependencies {
    provided 'de.robv.android.xposed:api:82'
}

官网最新的版本还是api-82.jar、api-source-82.jar。

下载来看下里面的内容，一个是.class字节码，一个是.java源代码而已。

随便打开个文件来康康，IXposedHookLoadPackage.java：

package de.robv.android.xposed;

import android.app.Application;

import de.robv.android.xposed.callbacks.XC_LoadPackage;
import de.robv.android.xposed.callbacks.XC_LoadPackage.LoadPackageParam;

/**
 * Get notified when an app ("Android package") is loaded.
 * This is especially useful to hook some app-specific methods.
 *
 * <p>This interface should be implemented by the module's main class. Xposed will take care of
 * registering it as a callback automatically.
 */
public interface IXposedHookLoadPackage extends IXposedMod {
	/**
	 * This method is called when an app is loaded. It's called very early, even before
	 * {@link Application#onCreate} is called.
	 * Modules can set up their app-specific hooks here.
	 *
	 * @param lpparam Information about the app.
	 * @throws Throwable Everything the callback throws is caught and logged.
	 */
	void handleLoadPackage(LoadPackageParam lpparam) throws Throwable;

	/** @hide */
	final class Wrapper extends XC_LoadPackage {
		private final IXposedHookLoadPackage instance;
		public Wrapper(IXposedHookLoadPackage instance) {
			this.instance = instance;
		}
		@Override
		public void handleLoadPackage(LoadPackageParam lpparam) throws Throwable {
			instance.handleLoadPackage(lpparam);
		}
	}
}

里面的各种xposed特征字符串到处都是。

也就是说，如果我们更改了xposed的字符串特征，也要制作这样的一份api-82.jar、api-source-82.jar，供开发者编写代码时进行调用。

并且开发者在编码时，使用的系列API中，至少不存在xposed字样。

到这里正常的Xposed插件开发及使用流程中可以搜集到的特征就都有了，接下来看一个专业检测Xposed的App，看看它主要检测哪些方面。

收集特征：XposedChecker源码

作者已经将源码开源：XposedChecker，安装包位于app目录中，名字叫Xposed Checker 4.apk，先装上去跑一下，申请root权限时点击“同意”，结果如下图所示，可信度竟然5/9，我的GravityBox插件还在跑着，状态栏还变着色：

这个结果肯定是不准确的，那四个绿色的项目中，只有“检测虚拟Xposed环境”是对的，毕竟我们不是VirtualXposed，而是真实的Xposed。其他三项出现了失误，可以看看它的源码怎么写的，主要的检测逻辑位于app\src\main\java\ml\w568w\checkxposed\ui\MainActivity.java文件中，定义了以下功能：

private static final String[] CHECK_ITEM = {
  "载入Xposed工具类",
  "寻找特征动态链接库",
  "代码堆栈寻找调起者",
  "检测Xposed安装情况",
  "判定系统方法调用钩子",
  "检测虚拟Xposed环境",
  "寻找Xposed运行库文件",
  "内核查找Xposed链接库",
  "环境变量特征字判断",
};
  • 载入Xposed工具类
private boolean testClassLoader() {
        try {
            ClassLoader.getSystemClassLoader()
				.loadClass("de.robv.android.xposed.XposedHelpers");

            return true;
        }
		catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return false;
    }
  • 寻找特征动态链接库
private int check2() {
    return checkContains("XposedBridge") ? 1 : 0;
}
public static boolean checkContains(String paramString) {
    try {
        HashSet<String> localObject = new HashSet<>();
        // 读取maps文件信息
        BufferedReader localBufferedReader =
    new BufferedReader(new FileReader("/proc/" + Process.myPid() + "/maps"));
        while (true) {
            String str = localBufferedReader.readLine();
            if (str == null) {
                break;
            }
            localObject.add(str.substring(str.lastIndexOf(" ") + 1));
        }
        //应用程序的链接库不可能是空，除非是高于7.0。。。
        if (localObject.isEmpty() && Build.VERSION.SDK_INT <= Build.VERSION_CODES.M) {
            return true;
        }
        localBufferedReader.close();
        for (String aLocalObject : localObject) {
            if (aLocalObject.contains(paramString)) {
                return true;
            }
        }
    }
catch (Throwable ignored) {
    }
    return false;
}
  • 代码堆栈寻找调起者
private int check3() {
        try {
            throw new Exception();
        }
		catch (Exception e) {
            StackTraceElement[] arrayOfStackTraceElement = e.getStackTrace();
            for (StackTraceElement s : arrayOfStackTraceElement) {
                if ("de.robv.android.xposed.XposedBridge".equals(s.getClassName())) {
                    return 1;
                }
            }
            return 0;
        }
    }
  • 检测XposedInstaller安装情况
    private int check4() {
        try {
            List<PackageInfo> list = getPackageManager().getInstalledPackages(0);
            for (PackageInfo info : list) {
                if ("de.robv.android.xposed.installer".equals(info.packageName)) {
                    return 1;
                }
                if ("io.va.exposed".equals(info.packageName)) {
                    return 1;
                }
            }
        }
		catch (Throwable ignored) {

        }
        return 0;
    }
  • 判定系统方法调用钩子
    private int check5() {
        try {
            Method method = Throwable.class.getDeclaredMethod("getStackTrace");
            return Modifier.isNative(method.getModifiers()) ? 1 : 0;
        }
		catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
        return 0;
    }
  • 检测虚拟Xposed环境
private int check6() {
    return System.getProperty("vxp") != null ? 1 : 0;
}
  • 寻找Xposed运行库文件
private int check7() {
        CommandResult commandResult = Shell.run("ls /system/lib");
        return commandResult.isSuccessful() ? commandResult.getStdout().contains("xposed") ? 1 : 0 : 0;
    }
  • 内核查找Xposed链接库
char isXposedMaps(char * pid){
	FILE * maps;
	char path[80];
	char * content;
	strcpy (path,"/proc/");
	strcat (path,pid);
	strcat (path,"/maps");
	if((maps=fopen(path,"r"))==NULL){
		return 0;
	}else{
		int len=filelength(maps);
		content=(char *)malloc(len);
		fread(content,len,1,maps);
		content[len-1]='\0';
		return strstr(content,"XposedBridge")!=NULL;
	}
}
  • 环境变量特征字判断
private int check9() {
    return System.getenv("CLASSPATH").contains("XposedBridge") ? 1 : 0;
}

收集特征：逆向分析大厂方案

以上每一篇都看过来之后，发现文章还是比较过时的，现在大部分风控都是写在so中，检测项目可能多达成百上千项，并且Ollvm甚至自家vmp来混淆下，不会让你轻易地找到并patch的；只是他们收集了环境特征后只是加密上传，并不会把app退掉让你发现而已。

针对这种加固/风控的行为特征，可能比较好的方案就是修改aosp系统源码，打更多的埋点，收集so的检测项目，形成一个checklist；或者unicorn来模拟执行，只是现在对抗unicorn的技术也越来越多，unicorn的终极形态，就是一个完整的安卓系统；所以不如直接改系统。

当然我们不用分析那么远，只需要简单修改XPOSED的字符串，过简单的根据字符串特征的XPOSED检测是没有问题的。

在下一篇中我们将介绍XPOSED框架之间的关系，以及如何编译使用原版XPOSED框架，最后一篇中再来简单更改特征。