攻防世界 reverse pingpong

pingpong XCTF 3rd-BCTF-2017

java层代码很简单：

  1 package com.geekerchina.pingpongmachine;
  2 
  3 import android.os.Bundle;
  4 import android.support.v7.app.AppCompatActivity;
  5 import android.view.Menu;
  6 import android.view.MenuItem;
  7 import android.view.View$OnClickListener;
  8 import android.view.View;
  9 import android.widget.TextView;
 10 
 11 public class MainActivity extends AppCompatActivity {
 12     class com.geekerchina.pingpongmachine.MainActivity$1 implements View$OnClickListener {
 13         com.geekerchina.pingpongmachine.MainActivity$1(MainActivity arg1) {
 14             MainActivity.this = arg1;
 15             super();
 16         }
 17 
 18         public void onClick(View arg7) {
 19             if(MainActivity.this.tt % 2 == 1) {
 20                 MainActivity.this.p = 0;
 21                 MainActivity.this.num = 0;
 22                 MainActivity.this.tt = MainActivity.this.ttt;
 23             }
 24 
 25             --MainActivity.this.tt;
 26             MainActivity.this.p = MainActivity.this.ping(MainActivity.this.p, MainActivity.this.num);
 27             ++MainActivity.this.num;
 28             if(MainActivity.this.num >= 7) {
 29                 MainActivity.this.num = 0;
 30             }
 31 
 32             View v0 = MainActivity.this.findViewById(0x7F0B0056);
 33             ((TextView)v0).setText("PING");
 34             if(MainActivity.this.tt == 0) {
 35                 ((TextView)v0).setText("FLAG: BCTF{MagicNum" + Integer.toString(MainActivity.this.p) + "}");
 36             }
 37         }
 38     }
 39 
 40     class com.geekerchina.pingpongmachine.MainActivity$2 implements View$OnClickListener {
 41         com.geekerchina.pingpongmachine.MainActivity$2(MainActivity arg1) {
 42             MainActivity.this = arg1;
 43             super();
 44         }
 45 
 46         public void onClick(View arg7) {
 47             if(MainActivity.this.tt % 2 == 0) {
 48                 MainActivity.this.p = 0;
 49                 MainActivity.this.num = 0;
 50                 MainActivity.this.tt = MainActivity.this.ttt;
 51             }
 52 
 53             --MainActivity.this.tt;
 54             MainActivity.this.p = MainActivity.this.pong(MainActivity.this.p, MainActivity.this.num);
 55             ++MainActivity.this.num;
 56             if(MainActivity.this.num >= 7) {
 57                 MainActivity.this.num = 0;
 58             }
 59 
 60             View v0 = MainActivity.this.findViewById(0x7F0B0056);
 61             ((TextView)v0).setText("PONG");
 62             if(MainActivity.this.tt == 0) {
 63                 ((TextView)v0).setText("FLAG: BCTF{MagicNum" + Integer.toString(MainActivity.this.p) + "}");
 64             }
 65         }
 66     }
 67 
 68     View$OnClickListener jping;
 69     View$OnClickListener jpong;
 70     public int num;
 71     public int p;
 72     public int tt;
 73     public int ttt;
 74 
 75     static {
 76         System.loadLibrary("pp");
 77     }
 78 
 79     public MainActivity() {
 80         super();
 81         this.p = 0;
 82         this.num = 0;
 83         this.ttt = 1000000;
 84         this.tt = this.ttt;
 85         this.jping = new com.geekerchina.pingpongmachine.MainActivity$1(this);
 86         this.jpong = new com.geekerchina.pingpongmachine.MainActivity$2(this);
 87     }
 88 
 89     protected void onCreate(Bundle arg4) {
 90         super.onCreate(arg4);
 91         this.setContentView(0x7F04001B);
 92         this.findViewById(0x7F0B0057).setOnClickListener(this.jping);
 93         this.findViewById(0x7F0B0058).setOnClickListener(this.jpong);
 94     }
 95 
 96     public boolean onCreateOptionsMenu(Menu arg3) {
 97         this.getMenuInflater().inflate(0x7F0D0000, arg3);
 98         return 1;
 99     }
100 
101     public boolean onOptionsItemSelected(MenuItem arg3) {
102         boolean v1 = arg3.getItemId() == 0x7F0B0070 ? true : super.onOptionsItemSelected(arg3);
103         return v1;
104     }
105 
106     public native int ping(int arg1, int arg2) {
107     }
108 
109     public native int pong(int arg1, int arg2) {
110     }
111 }

有两个按钮，分别调用natice层 ping方法、pong方法

先随便点一个，然后先ping 后pong，总共点击1000000次后输出flag

libpp.so 中的方法ping、pong中都有调用sleep(1) ，我们需要修改so文件，将其参数设为0

网上的一些wp都是新建个工程，然后调用so中方法。

那我们直接使用frida调用不就好了。

frida脚本：

  1 import frida, sys
  2 
  3 
  4 def on_message(message, data):
  5     if message['type'] == 'send':
  6         print("[*] {0}".format(message['payload']))
  7     else:
  8         print(message)
  9 
 10 jscode = """
 11 setImmediate(function () {
 12     Java.perform(function () {
 13         console.log("start");
 14         //so层hook
 15         //导出函数
 16         //var exports = Module.enumerateExportsSync("libpp.so");
 17         //for(var i=0;i<exports.length;i++){
 18         //    send("name:"+exports[i].name+"  address:"+exports[i].address);
 19         // }
 20 
 21         //遍历模块找基址
 22         Process.enumerateModules({
 23             onMatch: function (exp) {
 24                 if (exp.name == 'libpp.so') {
 25                     send('enumerateModules find');
 26                     send(exp.name + "|" + exp.base + "|" + exp.size + "|" + exp.path);
 27                     send(exp);
 28                     return 'stop';
 29                 }
 30             },
 31             onComplete: function () {
 32                 send('enumerateModules stop');
 33             }
 34         });
 35 
 36         //通过模块名直接查找基址
 37         var soAddr = Module.findBaseAddress("libpp.so");
 38         send("soAddr:" + soAddr);
 39 
 40         var aping=0x1308+1
 41         var apong=0x1564+1
 42         //   hook导出函数 通过函数名
 43 
 44         var fping=Module.findExportByName("libpp.so", "Java_com_geekerchina_pingpongmachine_MainActivity_ping")
 45         send("findExportByName ping():" +fping );
 46         fping=new NativePointer(soAddr).add(aping);
 47         //NativePointer   简写ptr
 48         send("findExportByName ping():" +fping );
 49         var ping=new NativeFunction(fping, "int", ['pointer','pointer','int', 'int']);
 50 
 51 
 52         //send("findExportByName edit():"+Module.findExportByName("libpp.so", "_ZL4editP7_JNIEnvP8_jobjecti"))
 53         // Interceptor.attach(fping, {
 54         //     onEnter: function (args) {
 55         //         send("ping() began p:" + args[2] + ", num:" + args[3] );
 56         //     },
 57         //     onLeave: function (retval) {
 58         //         send("ping() return:" + retval);
 59         //     }
 60         // });
 61 
 62         //   hook导出函数 通过函数名
 63         var fpong=Module.findExportByName("libpp.so", "Java_com_geekerchina_pingpongmachine_MainActivity_pong")
 64         send("findExportByName pong():" +fpong );
 65         fpong=new NativePointer(soAddr).add(apong);
 66         send("findExportByName pong():" +fpong );
 67         var pong=new NativeFunction(fpong, "int", ['pointer','pointer','int', 'int']);
 68         //send("findExportByName edit():"+Module.findExportByName("libpp.so", "_ZL4editP7_JNIEnvP8_jobjecti"))
 69         // Interceptor.attach(fpong, {
 70         //     onEnter: function (args) {
 71         //         send("pong() began p:" + args[2] + ", num:" + args[3] );
 72         //     },
 73         //     onLeave: function (retval) {
 74         //         send("pong() return:" + retval);
 75         //     }
 76         // });
 77         var env = Java.vm.getEnv();
 78         var obj=ptr(0);
 79         var check = 1000000;
 80         var beFlag = 0;
 81         var num = 0;
 82         while (true) {               //下面这部分代码参考 https://blog.csdn.net/jasalee/article/details/70242837
 83             if (check % 2 == 1) {
 84                 --check;
 85                 beFlag = pong(env,obj,beFlag,num);
 86                 ++num;
 87                 if(num >= 7) {
 88                     num = 0;
 89                 }
 90             } else {
 91                 --check;
 92                 beFlag = ping(env,obj,beFlag,num);
 93                 ++num;
 94                 if(num >= 7){
 95                     num = 0;
 96                 }
 97             }
 98             if (check == 0) {
 99                 send("check:"+check+" num:"+num)
100                 send("FLAG : "+"BCTF{MagicNum" + beFlag+ "}");
101                 break;
102             }
103         }
104         
105     });
106 });
107 """
108 
109 
110 # 运行中hook
111 process = frida.get_usb_device().attach('com.geekerchina.pingpongmachine')
112 script = process.create_script(jscode)
113 script.on('message', on_message)
114 print('[*] Running test')
115 script.load()
116 sys.stdin.read()
117 
118 
119 '''
120 [*] Running test
121 start
122 [*] enumerateModules find
123 [*] libpp.so|0xd4c48000|24576|/data/app/com.geekerchina.pingpongmachine-6gshbHpfeBmTBFRYBxQpNg==/lib/arm/libpp.so
124 [*] {'name': 'libpp.so', 'base': '0xd4c48000', 'size': 24576, 'path': '/data/app/com.geekerchina.pingpongmachine-6gshbHpfeBmTBFRYBxQpNg==/lib/arm/libpp.so'}
125 [*] enumerateModules stop
126 [*] soAddr:0xd4c48000
127 [*] findExportByName ping():0xd34c9309
128 [*] findExportByName ping():0xd4c49309
129 [*] findExportByName pong():0xd34c9565
130 [*] findExportByName pong():0xd4c49565
131 [*] check:0 num:1
132 [*] FLAG : BCTF{MagicNum4500009}
133 '''

大约要跑4、5分钟的样子，没去分析ping、pong方法，大佬们可以分析一波 0.0

BCTF{MagicNum4500009}

脚本编写中也发现了一个问题：

　　Module.findExportByName 得到的地址不正确。

应该使用 基地址+函数偏移地址（thumb指令下偏移地址+1）