Execute a given program with custom args and env vars. Can be used by gdb as exec wrapper.

wrapper_template.py

#!/usr/bin/python2

import sys
from ctypes import cdll, c_char_p, cast
from ctypes.util import find_library

# to use with gdb:
# set exec-wrapper ./wrapper_template.py

# custom args and env vars
ARGS = [
    'arg1',
    'arg2',
]

ENVARS = [
    'VAR1=foo',
    'VAR2=bar',
]

def main():
    if len(sys.argv) < 2:
        usage()
    else:
        wrap(sys.argv[1], ARGS, ENVARS)

def usage():
    print("Usage: {:s} target_program".format(sys.argv[0]))
    exit(0)

def wrap(vuln, args, envars):
    libc = cdll.LoadLibrary(find_library("c"))
    execve = libc.execve

    argp = py2c_str_list(args)
    envp = py2c_str_list(envars)
    execve(vuln, argp, envp)

    # if it reach this point, execve has failed
    print('execve failed!')

def py2c_str_list(py_list):
    py_list += [None]
    str_ptrs = (c_char_p * len(py_list))()

    for i, s in enumerate(py_list):
        str_ptrs[i] = cast(s, c_char_p)
    return str_ptrs

if __name__ == "__main__":
    main()