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"""Verify BCrypt CNG setup - test raw key + different CFB segment sizes."""
import ctypes
from ctypes import c_void_p, c_ulong, byref
from pathlib import Path
import struct
KEY = b'kj)TGtrK>f]b[Piow.gU+nC@s""""""4'
IV = b"Copyright @ OneO"
bcrypt = ctypes.windll.bcrypt
# Known plaintext (DX header from hook dump)
dx_plain = bytes.fromhex("44580000000000005c58000000000000")
# Known ciphertext (from file at offset 24, first 16 bytes)
file_ct = bytes.fromhex("2e0c10c7c967f66b6d03821271115ad6")
# Full file data
file_data = Path("ocr_data/oneocr.onemodel").read_bytes()
hook_dx = Path("frida_dump/decrypt_1_in22624_out22624.bin").read_bytes()
print("=" * 70)
print("BCrypt CNG CFB Segment Size Test")
print("=" * 70)
print(f"KEY: {KEY}")
print(f"IV: {IV}")
print(f"Expected PT: {dx_plain.hex()}")
print(f"Expected CT: {file_ct.hex()}")
print()
def test_cfb(msg_block_length, use_blob=False):
"""Test BCrypt AES-CFB with given MessageBlockLength."""
tag = "MBL={}".format("default" if msg_block_length is None else msg_block_length)
if use_blob:
tag += "+blob"
hAlg = c_void_p()
status = bcrypt.BCryptOpenAlgorithmProvider(
byref(hAlg), "AES\0".encode("utf-16-le"), None, 0
)
if status != 0:
print(" [{}] OpenAlgorithm failed: {:#010x}".format(tag, status))
return None
mode = "ChainingModeCFB\0".encode("utf-16-le")
status = bcrypt.BCryptSetProperty(
hAlg, "ChainingMode\0".encode("utf-16-le"), mode, len(mode), 0
)
if status != 0:
print(" [{}] SetProperty ChainingMode failed: {:#010x}".format(tag, status))
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
return None
if msg_block_length is not None:
mbl = c_ulong(msg_block_length)
status = bcrypt.BCryptSetProperty(
hAlg, "MessageBlockLength\0".encode("utf-16-le"),
byref(mbl), 4, 0
)
if status != 0:
print(" [{}] SetProperty MBL={} failed: {:#010x}".format(tag, msg_block_length, status))
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
return None
hKey = c_void_p()
if use_blob:
blob = struct.pack('<III', 0x4d42444b, 1, len(KEY)) + KEY
status = bcrypt.BCryptGenerateSymmetricKey(
hAlg, byref(hKey), None, 0, blob, len(blob), 0
)
else:
status = bcrypt.BCryptGenerateSymmetricKey(
hAlg, byref(hKey), None, 0, KEY, len(KEY), 0
)
if status != 0:
print(" [{}] GenerateSymmetricKey failed: {:#010x}".format(tag, status))
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
return None
# Encrypt test
iv_enc = bytearray(IV)
result_size = c_ulong(0)
bcrypt.BCryptEncrypt(hKey, dx_plain, len(dx_plain), None, None, 0,
None, 0, byref(result_size), 0)
output = (ctypes.c_ubyte * result_size.value)()
actual = c_ulong(0)
iv_buf = (ctypes.c_ubyte * 16)(*iv_enc)
bcrypt.BCryptEncrypt(hKey, dx_plain, len(dx_plain), None,
iv_buf, 16, output, result_size.value, byref(actual), 0)
our_ct = bytes(output[:actual.value])
ct_match = our_ct[:16] == file_ct
# Decrypt test (fresh key)
hKey2 = c_void_p()
if use_blob:
blob = struct.pack('<III', 0x4d42444b, 1, len(KEY)) + KEY
bcrypt.BCryptGenerateSymmetricKey(hAlg, byref(hKey2), None, 0, blob, len(blob), 0)
else:
bcrypt.BCryptGenerateSymmetricKey(hAlg, byref(hKey2), None, 0, KEY, len(KEY), 0)
iv_dec = bytearray(IV)
encrypted_chunk = file_data[24:24 + 32]
result_size = c_ulong(0)
bcrypt.BCryptDecrypt(hKey2, encrypted_chunk, len(encrypted_chunk), None, None, 0,
None, 0, byref(result_size), 0)
output2 = (ctypes.c_ubyte * result_size.value)()
iv_buf2 = (ctypes.c_ubyte * 16)(*iv_dec)
status = bcrypt.BCryptDecrypt(hKey2, encrypted_chunk, len(encrypted_chunk), None,
iv_buf2, 16, output2, result_size.value, byref(actual), 0)
our_pt = bytes(output2[:actual.value])
pt_match = our_pt[:2] == b"DX"
mark = "*** MATCH! ***" if ct_match else ""
print(" [{}] Enc->CT: {} {} {}".format(tag, our_ct[:16].hex(), "OK" if ct_match else "FAIL", mark))
print(" [{}] Dec->PT: {} {}".format(tag, our_pt[:16].hex(), "OK DX" if pt_match else "FAIL"))
bcrypt.BCryptDestroyKey(hKey)
bcrypt.BCryptDestroyKey(hKey2)
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
return ct_match
print("--- Raw key (correct for BCryptGenerateSymmetricKey) ---")
test_cfb(None)
test_cfb(1)
test_cfb(16)
print()
print("--- Blob key (has 12-byte header prepended - wrong) ---")
test_cfb(None, use_blob=True)
test_cfb(1, use_blob=True)
test_cfb(16, use_blob=True)
print()
print("--- BCryptImportKey with BCRYPT_KEY_DATA_BLOB ---")
for mbl in [None, 1, 16]:
tag = "Import+MBL={}".format("default" if mbl is None else mbl)
hAlg = c_void_p()
bcrypt.BCryptOpenAlgorithmProvider(byref(hAlg), "AES\0".encode("utf-16-le"), None, 0)
mode = "ChainingModeCFB\0".encode("utf-16-le")
bcrypt.BCryptSetProperty(hAlg, "ChainingMode\0".encode("utf-16-le"), mode, len(mode), 0)
if mbl is not None:
mbl_val = c_ulong(mbl)
bcrypt.BCryptSetProperty(hAlg, "MessageBlockLength\0".encode("utf-16-le"),
byref(mbl_val), 4, 0)
blob = struct.pack('<III', 0x4d42444b, 1, len(KEY)) + KEY
hKey = c_void_p()
status = bcrypt.BCryptImportKey(
hAlg, None, "KeyDataBlob\0".encode("utf-16-le"),
byref(hKey), None, 0, blob, len(blob), 0
)
if status != 0:
print(" [{}] ImportKey failed: {:#010x}".format(tag, status))
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
continue
iv_dec = bytearray(IV)
encrypted_chunk = file_data[24:24 + 32]
result_size = c_ulong(0)
bcrypt.BCryptDecrypt(hKey, encrypted_chunk, 32, None, None, 0,
None, 0, byref(result_size), 0)
output = (ctypes.c_ubyte * result_size.value)()
actual = c_ulong(0)
iv_buf = (ctypes.c_ubyte * 16)(*iv_dec)
status = bcrypt.BCryptDecrypt(hKey, encrypted_chunk, 32, None,
iv_buf, 16, output, result_size.value, byref(actual), 0)
dec = bytes(output[:actual.value])
match = dec[:2] == b"DX"
mark = "*** MATCH! ***" if match else ""
print(" [{}] Decrypt: {} {} {}".format(tag, dec[:16].hex(), "OK DX" if match else "FAIL", mark))
bcrypt.BCryptDestroyKey(hKey)
bcrypt.BCryptCloseAlgorithmProvider(hAlg, 0)
print()
print("=" * 70)
print("If no method matched, need to hook BCryptSetProperty in the DLL")
print("to discover ALL properties set before BCryptDecrypt is called.")
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