Creating Tiny BareBone executables in Python for debugging shellcode and function stubs

The following python script creates a barebone exe called out.exe that does nothing.  Its extremely useful when you need to debug shellcode or an application stub.  Simply load out.exe into Immunity, allocate a buffer, cut and paste the shellcode into the new buffer via the hex dump window, or just cut and paste the shellcode below the return at address 0x00401010 (for example) in the hex dump window. Finally modify RETN to JMP + ADDR of the shellcode you would like to execute. 

out.exe loaded into immunity debugger.  

Simply modifying the RETN command to JMP 00401010 for example and paste your shellcode at that address in the hex window.  Next press F7 to step into your stub or shellcode.  

miniexe.py

import re
import sys
import binascii
import os
exe_str = "4D5A9" + ("0" * 4) + "3" + ("0" * 7) + "4" + ("0" * 6) + "FFFF" + ("0" * 4) + \
"B8" + ("0" * 14) + "4" + ("0" * 71) + "B" + ("0" * 8) + \
"E1FBA0E00B409CD21B8014CCD21546869732070726F6772616D2063616E6E6F742062652072756E20696E20444F53206D6F64652E0D0D0A24" + \
("0" * 14) + "BB41E4DAFF208A89FF208A89FF208A89FF208A89FE208A8990561789FE208A8952696368FF208A89" + \
("0" * 16) + "5045" + ("0" * 4) + "4C0101004C9AF85" + ("0" * 17) + "E" + ("0" * 4) + \
"2010B010A" + ("0" * 5) + "2" + ("0" * 22) + "1" + ("0" * 7) + "1" + ("0" * 7) + \
"2" + ("0" * 9) + "4" + ("0" * 5) + "1" +("0" * 8) + "2" + ("0" * 5) + "5" + ("0" * 3) + \
"1" + ("0" * 11) + "5" + ("0" *3) + "1" + ("0" * 12) + "2" + ("0" * 8) + "2" + ("0" * 13) + \
"3004085" + ("0" * 4) + "1" + ("0" * 5) + "1" + ("0" * 9) + "1" + ("0" * 5) + "1" + ("0" * 13) + \
"1" + ("0" * 263) + "2E74657874" + ("0" * 7) + "1" + ("0" * 8) + "1" + ("0" * 8) + \
"2" + ("0" * 7) + "2" + ("0" * 28) + "2" + ("0" * 5) + "6" + ("0" * 97) + "C3"+ ("0" * 1022)
f = open("out.exe", 'wb')
f.write(binascii.unhexlify(exe_str))
f.close()

hexdump of out.exe 

hexdump -C out.exe 
00000000  4d 5a 90 00 03 00 00 00  04 00 00 00 ff ff 00 00  |MZ..............|
00000010  b8 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  |........@.......|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 b0 00 00 00  |................|
00000040  0e 1f ba 0e 00 b4 09 cd  21 b8 01 4c cd 21 54 68  |........!..L.!Th|
00000050  69 73 20 70 72 6f 67 72  61 6d 20 63 61 6e 6e 6f  |is program canno|
00000060  74 20 62 65 20 72 75 6e  20 69 6e 20 44 4f 53 20  |t be run in DOS |
00000070  6d 6f 64 65 2e 0d 0d 0a  24 00 00 00 00 00 00 00  |mode....$.......|
00000080  bb 41 e4 da ff 20 8a 89  ff 20 8a 89 ff 20 8a 89  |.A... ... ... ..|
00000090  ff 20 8a 89 fe 20 8a 89  90 56 17 89 fe 20 8a 89  |. ... ...V... ..|
000000a0  52 69 63 68 ff 20 8a 89  00 00 00 00 00 00 00 00  |Rich. ..........|
000000b0  50 45 00 00 4c 01 01 00  4c 9a f8 50 00 00 00 00  |PE..L...L..P....|
000000c0  00 00 00 00 e0 00 02 01  0b 01 0a 00 00 02 00 00  |................|
000000d0  00 00 00 00 00 00 00 00  00 10 00 00 00 10 00 00  |................|
000000e0  00 20 00 00 00 00 40 00  00 10 00 00 00 02 00 00  |. ....@.........|
000000f0  05 00 01 00 00 00 00 00  05 00 01 00 00 00 00 00  |................|
00000100  00 20 00 00 00 02 00 00  00 00 00 00 03 00 40 85  |. ............@.|
00000110  00 00 10 00 00 10 00 00  00 00 10 00 00 10 00 00  |................|
00000120  00 00 00 00 10 00 00 00  00 00 00 00 00 00 00 00  |................|
00000130  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001a0  00 00 00 00 00 00 00 00  2e 74 65 78 74 00 00 00  |.........text...|
000001b0  01 00 00 00 00 10 00 00  00 02 00 00 00 02 00 00  |................|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 20 00 00 60  |............ ..`|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200  c3 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400

EOF