如何使用 3DES 加密恢复由 OpenSSL 加密的文件的密钥和 iv？

Question

我知道类似问题有一些答案，但这些似乎仅适用于 AES 加密，当我使用 python 进行密钥推导时，我得到了不同的结果。

现在我有了密码和盐（来自以前使用 3DES 的 OpenSSL 加密文件）。我可以简单地通过 OpenSSL 计算密钥和 iv，但我想将密钥派生实现到我的 python.

这是来自 OpenSSL 的输出，我相信在使用 python:

推导密钥后我应该得到相同的结果

# openssl enc -des3 -pass pass:cfe4ec9fcec928d51d243855a094b05ebb7bc870 -S 3AA6A64F87764632 -P
salt=3AA6A64F87764632
key=6A8E552A81763B15EC9E1430FAB774C7B5113AFD89E6F03C
iv =DE2CFC91DC61E734

我将此代码用于我的 python:

...
print("password is", password.hexdigest())
...
D1=hashlib.md5(password.digest() + openssl_salt).digest()
D2=hashlib.md5(D1 + password.digest() + openssl_salt).digest()
D3=hashlib.md5(D2 + password.digest() + openssl_salt).digest()
key=D1+D2
iv=D3
print ('salt:', openssl_salt.hex())
print ('key:', key.hex())
print ('iv:', iv.hex())

这是我的结果，它明显不同而且 key/iv 长度也是错误的：

password is cfe4ec9fcec928d51d243855a094b05ebb7bc870
...
salt: 3aa6a64f87764632
key: 49096a6dca92f70c88e92a9d67062b8ae70223e432e23a4ee9abd3531d35e1aa
iv: 964f7299c4b960a1264863a23fbbf20b

我认为这些代码可能用于 AES 密钥派生，而不是用于 3DES。谁能给点建议？

Answer 1

查看 this post and the documentation openssl enc 使用的 KDF，看来您已经非常接近解决方案了。

密码 cfe... 只是作为 ASCII 文本编码为字节，而不是十六进制字符串。
密钥是24字节，IV是8，MD5摘要是16，所以我们只需要两轮。

放在一起：

>>> password = 'cfe4ec9fcec928d51d243855a094b05ebb7bc870'.encode()
>>> salt = bytes.fromhex('3AA6A64F87764632')
>>> d1 = hashlib.md5(password+salt)
>>> d2 = hashlib.md5(d1.digest()+password+salt)
>>> keymatter = d1.digest() + d2.digest()
>>> key = keymatter[:24].hex().upper()
>>> iv = keymatter[24:32].hex().upper()
>>> print(f'key: {key}\nIV:  {iv}')
key: 6A8E552A81763B15EC9E1430FAB774C7B5113AFD89E6F03C
IV:  DE2CFC91DC61E734

Answer 2

如果您喜欢没有外部库的纯 Python 解决方案，请使用 Tom Tang 在他的 GitHub Gist https://gist.github.com/tly1980/b6c2cc10bb35cb4446fb6ccf5ee5efbc.

上提供的方法

输出将是：

SO derive key and iv from passphrase like OpenSSL for 3DES
password: cfe4ec9fcec928d51d243855a094b05ebb7bc870
salt (hex) length: 8  data: 3aa6a64f87764632
key (hex) length:  24 data: 6a8e552a81763b15ec9e1430fab774c7b5113afd89e6f03c
iv (hex) length:   8  data: de2cfc91dc61e734

完整源代码：

# source get_key_and_iv by Tom Tang 
# https://gist.github.com/tly1980/b6c2cc10bb35cb4446fb6ccf5ee5efbc

# ================================================================
# get_key_and_iv
# ================================================================
def get_key_and_iv(password, salt, klen=32, ilen=16, msgdgst='md5'):
    '''
    Derive the key and the IV from the given password and salt.

    This is a niftier implementation than my direct transliteration of
    the C++ code although I modified to support different digests.

    CITATION: 

    @param password  The password to use as the seed.
    @param salt      The salt.
    @param klen      The key length.
    @param ilen      The initialization vector length.
    @param msgdgst   The message digest algorithm to use.
    '''
    # equivalent to:
    #   from hashlib import <mdi> as mdf
    #   from hashlib import md5 as mdf
    #   from hashlib import sha512 as mdf
    mdf = getattr(__import__('hashlib', fromlist=[msgdgst]), msgdgst)
    password = password.encode('ascii', 'ignore')  # convert to ASCII

    try:
        maxlen = klen + ilen
        keyiv = mdf(password + salt).digest()
        tmp = [keyiv]
        while len(tmp) < maxlen:
            tmp.append( mdf(tmp[-1] + password + salt).digest() )
            keyiv += tmp[-1]  # append the last byte
        key = keyiv[:klen]
        iv = keyiv[klen:klen+ilen]
        return key, iv
    except UnicodeDecodeError:
        return None, None

def bytesToHex(input):
  return input.hex()

print("SO derive key and iv from passphrase like OpenSSL for 3DES")
password = 'cfe4ec9fcec928d51d243855a094b05ebb7bc870'
salt = bytes.fromhex('3AA6A64F87764632')
key, iv = get_key_and_iv(password, salt, 24, 8)
print("password: " + password)
print("salt (hex) length: " + str(len(salt)) + "  data: " + bytesToHex(salt))
print("key (hex) length:  " + str(len(key)) + " data: " + bytesToHex(key))
print("iv (hex) length:   " + str(len(iv)) + "  data: " + bytesToHex(iv))

如何使用 3DES 加密恢复由 OpenSSL 加密的文件的密钥和 iv？

How to recover key and iv for files encrypted by OpenSSL using 3DES encryption?

openssl

python

key

3des