encrypt.py

import ctypes
from ctypes import c_void_p, c_int, c_char, c_ulong

lib_path = '/opt/homebrew/opt/openssl@3/lib/libcrypto.dylib'
lib = ctypes.cdll.LoadLibrary(lib_path)

MAX_BLOCK_LENGTH = 32
MAX_IV_LENGTH = 16


class CipherType(ctypes.Structure):
    _fields_ = [
        ('nid', c_int),
        ('block_size', c_int),
        ('key_len', c_int),
        ('iv_len', c_int),
        ('flags', c_ulong),
        ('init', c_void_p),
        ('do_cipher', c_void_p),
        ('cleanup', c_void_p),
        ('ctx_size', c_int),
        ('set_asn1_parameters', c_void_p),
        ('get_asn1_parameters', c_void_p),
        ('ctrl', c_void_p),
        ('app_data', c_void_p),
    ]


class Cipher(ctypes.Structure):
    _fields_ = [
        ('cipher', c_void_p),  # POINTER(CipherType)
        ('engine', c_void_p),  # POINTER(ENGINE)
        ('encrypt', c_int),
        ('buf_len', c_int),
        ('oiv', c_char * MAX_IV_LENGTH),
        ('iv', c_char * MAX_IV_LENGTH),
        ('buf', c_char * MAX_BLOCK_LENGTH),
        ('num', c_int),
        ('app_data', c_void_p),
        ('key_len', c_int),
        ('flags', c_ulong),
        ('cipher_data', c_void_p),
        ('final_used', c_int),
        ('block_mask', c_int),
        ('final', c_char * MAX_BLOCK_LENGTH),
    ]


def get_error():
    err = lib.ERR_get_error()
    msg = ctypes.create_string_buffer(1024)
    lib.ERR_error_string(err, msg)
    return msg.value.decode()


lib.EVP_CIPHER_CTX_new.restype = ctypes.POINTER(Cipher)

ctx = lib.EVP_CIPHER_CTX_new().contents
assert ctx
key = '11111111111111111111111111111111'.encode()
iv = '1111111111111111'.encode()

engine = None
lib.EVP_get_cipherbyname.argtypes = (ctypes.c_char_p,)
lib.EVP_get_cipherbyname.restype = ctypes.POINTER(CipherType)
cipher = lib.EVP_get_cipherbyname('AES-256-CBC'.encode('ascii'))
assert cipher
encrypt = True
lib.EVP_CipherInit_ex.argtypes = (
    ctypes.POINTER(Cipher),
    ctypes.POINTER(CipherType),
    ctypes.c_void_p,
    ctypes.c_char_p,
    ctypes.c_char_p,
    ctypes.c_int,
)

res = lib.EVP_CipherInit_ex(ctx, cipher.contents, engine, key, iv, encrypt)
if res == 0:
    print(f"Error initializing cipher: {get_error()}")
    raise SystemExit(1)

data = b''
out = ctypes.create_string_buffer(len(data) + MAX_BLOCK_LENGTH - 1)
out_len = ctypes.c_int()

out_data = []

lib.EVP_CipherUpdate.argtypes = (
    ctypes.POINTER(Cipher),
    ctypes.c_char_p,
    ctypes.POINTER(ctypes.c_int),
    ctypes.c_char_p,
    ctypes.c_int,
)

res = lib.EVP_CipherUpdate(ctx, out, out_len, data, len(data))
if res != 1:
    print(f"Error updating cipher: {get_error()}")
    raise SystemExit(1)

out_data.append(out.raw[: out_len.value])

out = ctypes.create_string_buffer(MAX_BLOCK_LENGTH)
out_len = ctypes.c_int()

lib.EVP_CipherFinal_ex.argtypes = (
    ctypes.POINTER(Cipher),
    ctypes.c_char_p,
    ctypes.POINTER(ctypes.c_int),
)
res = lib.EVP_CipherFinal_ex(ctx, out, out_len)
if res != 1:
    print(f"Error finalizing cipher: {get_error()}")