Déchiffrer en Go ce qui a été chiffré avec AES en mode CFB en Python

Publier

Je veux pouvoir décrypter en Go ce qui a été crypté en Python. Les fonctions de chiffrement/déchiffrement fonctionnent respectivement dans chaque langue, mais pas lorsque je chiffre en Python et que je déchiffre en Go, je suppose qu'il y a quelque chose qui ne va pas avec l'encodage car j'obtiens une sortie charabia :

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Chiffrement/déchiffrement en Python

def encrypt(plaintext, key=config.SECRET, key_salt='', no_iv=False):
    """Encrypt shit the right way"""

    # sanitize inputs
    key = SHA256.new((key + key_salt).encode()).digest()
    if len(key) not in AES.key_size:
        raise Exception()
    if isinstance(plaintext, string_types):
        plaintext = plaintext.encode('utf-8')

    # pad plaintext using PKCS7 padding scheme
    padlen = AES.block_size - len(plaintext) % AES.block_size
    plaintext += (chr(padlen) * padlen).encode('utf-8')

    # generate random initialization vector using CSPRNG
    if no_iv:
        iv = ('\0' * AES.block_size).encode()
    else:
        iv = get_random_bytes(AES.block_size)
    log.info(AES.block_size)
    # encrypt using AES in CFB mode
    ciphertext = AES.new(key, AES.MODE_CFB, iv).encrypt(plaintext)

    # prepend iv to ciphertext
    if not no_iv:
        ciphertext = iv + ciphertext
    # return ciphertext in hex encoding
    log.info(ciphertext)
    return ciphertext.hex()


def decrypt(ciphertext, key=config.SECRET, key_salt='', no_iv=False):
    """Decrypt shit the right way"""

    # sanitize inputs
    key = SHA256.new((key + key_salt).encode()).digest()
    if len(key) not in AES.key_size:
        raise Exception()
    if len(ciphertext) % AES.block_size:
        raise Exception()
    try:
        ciphertext = codecs.decode(ciphertext, 'hex')
    except TypeError:
        log.warning("Ciphertext wasn't given as a hexadecimal string.")

    # split initialization vector and ciphertext
    if no_iv:
        iv = '\0' * AES.block_size
    else:
        iv = ciphertext[:AES.block_size]
        ciphertext = ciphertext[AES.block_size:]

    # decrypt ciphertext using AES in CFB mode
    plaintext = AES.new(key, AES.MODE_CFB, iv).decrypt(ciphertext).decode()

    # validate padding using PKCS7 padding scheme
    padlen = ord(plaintext[-1])
    if padlen < 1 or padlen > AES.block_size:
        raise Exception()
    if plaintext[-padlen:] != chr(padlen) * padlen:
        raise Exception()
    plaintext = plaintext[:-padlen]

    return plaintext

Cryptage/Décryptage en Go

// PKCS5Padding adds padding to the plaintext to make it a multiple of the block size
func PKCS5Padding(src []byte, blockSize int) []byte {
    padding := blockSize - len(src)%blockSize
    padtext := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(src, padtext...)
}

// Encrypt encrypts the plaintext,the input salt should be a random string that is appended to the plaintext
// that gets fed into the one-way function that hashes it.
func Encrypt(plaintext) string {
    h := sha256.New()
    h.Write([]byte(os.Getenv("SECRET")))
    key := h.Sum(nil)
    plaintextBytes := PKCS5Padding([]byte(plaintext), aes.BlockSize)
    block, err := aes.NewCipher(key)
    if err != nil {
        panic(err)
    }
    // The IV needs to be unique, but not secure. Therefore it's common to
    // include it at the beginning of the ciphertext.
    ciphertext := make([]byte, aes.BlockSize+len(plaintextBytes))
    iv := ciphertext[:aes.BlockSize]
    if _, err := io.ReadFull(rand.Reader, iv); err != nil {
        panic(err)
    }
    stream := cipher.NewCFBEncrypter(block, iv)
    stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintextBytes)
    // return hexadecimal representation of the ciphertext
    return hex.EncodeToString(ciphertext)
}
func PKCS5UnPadding(src []byte) []byte {
    length := len(src)
    unpadding := int(src[length-1])
    return src[:(length - unpadding)]
}
func Decrypt(ciphertext string) string {

    h := sha256.New()
    // have to check if the secret is hex encoded
    h.Write([]byte(os.Getenv("SECRET")))
    key := h.Sum(nil)
    ciphertext_bytes := []byte(ciphertext)
    block, err := aes.NewCipher(key)
    if err != nil {
        panic(err)
    }
    log.Print(aes.BlockSize)
    // The IV needs to be unique, but not secure. Therefore it's common to
    // include it at the beginning of the ciphertext.
    iv := ciphertext_bytes[:aes.BlockSize]
    if len(ciphertext) < aes.BlockSize {
        panic("ciphertext too short")
    }
    ciphertext_bytes = ciphertext_bytes[aes.BlockSize:]
    stream := cipher.NewCFBDecrypter(block, iv)
    stream.XORKeyStream(ciphertext_bytes, ciphertext_bytes)
    plaintext := PKCS5UnPadding(ciphertext_bytes)
    return string(plaintext)
}