openssl enc hashcat poc

openssl_poc.py

# install requirements: pip3 install pycryptodome hashlib
import sys, os
from binascii import unhexlify, hexlify
from hashlib import md5, sha256
from Crypto.Cipher import AES

# default setting, "openssl enc" pre v1.1.0
def kdf_aes256_md5(pwd, salt):

	h1 = md5(pwd + salt).digest()
	h2 = md5(h1 + pwd + salt).digest()
	iv = md5(h2 + pwd + salt).digest()
	print("h1 = " + hexlify(h1).decode('ascii'))
	print("h2 = " + hexlify(h2).decode('ascii'))
	
	aes_key = h1 + h2
	return aes_key, iv

#default setting "openssl enc" since v1.1.0
def kdf_aes256_sha256(pwd, salt):

	h1 = sha256(pwd + salt).digest()
	h2 = sha256(h1 + pwd + salt).digest()
	print("h2 = " + hexlify(h2).decode('ascii'))

	aes_key = h1
	iv = h2[:16]  # first 16 bytes

	return aes_key, iv

# usage: openssl_poc.py encrypted_file.aes "password_to_try" "known_header"
# all vars are raw bytes, there are no coversions to hex strings

password_to_try = sys.argv[2].encode()
known_header = sys.argv[3].encode()

with open(sys.argv[1], "rb") as f:
	if f.read(8) != b"Salted__":
		print("File " + sys.argv[1] + " is not a 'openssl enc' salted file, maybe it is base64 coded?")
		sys.exit(-1)
	file_salt = f.read(8)
	first_block = f.read(16)

print("File: " + sys.argv[1])
print("salt = " + hexlify(file_salt).decode('ascii'))
print("checking password [" + sys.argv[2] + "] = " + hexlify(password_to_try).decode('ascii'))

kdfs = { "OpenSSL 1.0.X default: MD5 / AES256": kdf_aes256_md5,
	"OpenSSL 1.1.X default: SHA256 / AES256": kdf_aes256_sha256 }

for desc, kdf in kdfs.items():
	print("\n == " + desc  + " ==")
	aes_key, iv = kdf(password_to_try, file_salt)
	print("aes_key = " + hexlify(aes_key).decode('ascii').upper())
	print("iv = " + hexlify(iv).decode('ascii').upper())
	
	aes = AES.new(aes_key, AES.MODE_CBC, iv)
	first_block_plain = aes.decrypt(first_block)
	pwd_is_good = first_block_plain[:len(known_header)] == known_header

	print("password [" + sys.argv[2] + "] correct: " + str(pwd_is_good))
	print("last block decrypted: [" + str(first_block_plain) + "]")

openssl_tohash.py

#!/usr/bin/env python3
import sys, os
from binascii import unhexlify, hexlify

if len(sys.argv) != 3:
	print("usage: openssl_tohash.py encrypted_file.aes known_header")
	print("  Format: $opensslenc$salt*first_block*known_header")
	sys.exit(-1)

try:
	file_size = os.stat(sys.argv[1]).st_size
	if file_size < 32:
		print("File " + sys.argv[1] + " is not a 'openssl enc' salted file, can't be smaller than 32 bytes")
		sys.exit(-1)
	single_block = file_size == 32
	with open(sys.argv[1], "rb") as f:
		if f.read(8) != b"Salted__":
			print("File " + sys.argv[1] + " is not a 'openssl enc' salted file, maybe it is base64 coded?")
			sys.exit(-1)
		file_salt = f.read(8)
		first_block = f.read(16)
except EnvironmentError as err:
	print("Error reading file: " + str(err))
	sys.exit(-1)

outstr = "$opensslenc$" + hexlify(file_salt).decode('ascii')
outstr += "*" + hexlify(first_block).decode('ascii')
outstr += "*" + hexlify(sys.argv[2].encode()).decode('ascii')

print(outstr)
sys.exit(0)