POC to transform a binary into a library

bin2lib.py

#!/usr/bin/env python3.6
import lief
import pathlib
from lief.ELF import Symbol

from lief import Logger
Logger.set_level(lief.LOGGING_LEVEL.INFO)

CURRENT_DIR = pathlib.PosixPath(".").resolve().as_posix()

# Assume that we figured out the address of the 'check' function at 0xB4C
CHECK_ADDR = 0xB4C
crackme = lief.parse(f"{CURRENT_DIR}/crackme.bin")

# Create a symbol for this address
check = Symbol()
check.name       = "check"
check.type       = lief.ELF.SYMBOL_TYPES.FUNC
check.binding    = lief.ELF.SYMBOL_BINDINGS.GLOBAL
check.visibility = lief.ELF.SYMBOL_VISIBILITY.DEFAULT
check.value      = CHECK_ADDR
check.shndx      = 12 # .text section

# Add it as an exported symbol
crackme.add_dynamic_symbol(check)

crackme.write(f"{CURRENT_DIR}/libcrackme.so")


# Now we have access to the 'check' function as follow

# #include <iostream>
# extern "C" {
# bool check(const char* input);
# }
#
# int main(int argc, char** argv) {
#   if (argc != 2) {
#     std::cerr << "Usage: " << argv[0] << " <string>" << std::endl;
#     return 1;
#   }
# 
#   std::cout << std::boolalpha << check(argv[1]); << std::endl;
#   return 0;
# }

# Compilation
# g++ play.cpp -L. -lcrackme -o play.bin