CryptJS PyCryptoDome - JS 端 AES 解密是不可能的

Question

I have been struggling for a day now with the following problem. I have already check a lot of answers in other topics, but nothing seems to work. Therefore, I have to ask here what the problem might be.

So, I can encrypt something in JS using AES w/ MODE_CBC, and decrypt it in python. However, I cannot do the other way around, therefore, I cannot encrypt in Python and decrypt in CryptoJS using the same mode, keys, and IVs. I thought that maybe the JS would receive the Passphrase, or the string or the IV worng, but it does not.

Can anyone help?

Here is the code

function Decrypt(key_from_python, passcode_encrypted_from_python){
    var key, k = sha256(key_from_python).substring(0, 32)
    var iv, i = sha256(key_from_python).substring(0, 16)
    key =  CryptoJS.enc.Utf8.parse(key);
    iv = CryptoJS.enc.Utf8.parse(iv);
    var to_decrypt = CryptoJS.enc.Base64.parse(passcode_encrypted_from_python)
    var encrypted = CryptoJS.AES.decrypt({ciphertext : to_decrypt}, key, {
          iv: iv,
    });
    return {
        "passcode": to_decrypt.toString(CryptoJS.enc.Base64),
        "passcode_bytes": to_decrypt.toString(CryptoJS.enc.Latin1),
        "s" : to_decrypt,
        "key" : k,
        "iv" : i,
        "enc" : encrypted
    }
}

Python Code:

def _pad(self, data):
    length = 16 - (len(data) % 16)
    return data + chr(length)*length

def _encrypt(self, to_encrypt, passphrase, iv):
    to_encrypt = self._encode(to_encrypt)
    print("To Encrypt", to_encrypt)
    passphrase = self._encode(passphrase)
    iv = self._encode(iv)

     #aes = AES.new(passphrase, AES.MODE_CFB, iv, segment_size=128)
     aes = AES.new(passphrase, AES.MODE_CBC, iv=iv)
     return aes.encrypt(to_encrypt)

OUTPUT FROM PYTHON:

key:  f26e2b2b7f6e89f5a8601bd24fb15327
iv:  f26e2b2b7f6e89f5
passcode:  b'8/TCP7QS\x08\x08\x08\x08\x08\x08\x08\x08'
To Encrypt b'8/TCP7QS\x08\x08\x08\x08\x08\x08\x08\x08'
Encrypted:  ¹Ïô·öï³Æ¼ÏÛ 
Encryptedb64 oLnPmfS39u+zxrzP28KYIA==

OUTPUT FROM JS:

key f26e2b2b7f6e89f5a8601bd24fb15327
iv f26e2b2b7f6e89f5
Encrypted:  ¹Ïô·öï³Æ¼ÏÛ 
Encryptedb64 oLnPmfS39u+zxrzP28KYIA==

However, the decrypted from JS giveS:

{
  'sigBytes': -114, 
   'words': [-1446864399, -2036001390, 207964078, 2005241986]
}

Any idea??

Many Thanks

Answer 1

I had a similar issue between Python and Java in the past which came down to incompatibilities in how the data was padded prior to encryption. The Python code was using a python module which had a defect ( https://github.com/jeppeter/pypkcs7/issues/1 ) and in some cases wouldn't pad at all and the Java code was expecting a pad.

The _pad method is padding correctly but it is not called in this example. If this is not called and CryptoJS is expecting a pad then this may explain your issue.

As mentioned by @Topaco in the comments there could be some other things going on depending on the content of the encode and sha256 methods.